Final Report Summary - ULTRAGRIP (Development of a high grip designing tool)
The ULTRAGRIP project (FP7-SME-2010-1-262413) has developed knowledge, technology and tools which can be used by sole and flooring manufacturers to optimise product performance in relation to slipping factors. These results contribute to the harmonisation of criteria and the achievement of efficient, quick and cost-effective solutions to slip problems relating to both, soles and floorings.
During the ULTRAGRIP project, the standard methods currently available for testing slip-resistance properties of footwear and flooring products have been studied in detail. This allowed for the identification of correlations in measurements shared by the two industries. These findings have been very interesting, especially for those project participants belonging to the flooring industry. This is due to the fact that, in contrast to the footwear industry, this sector and the related standardisation committees cannot reach an agreement regarding the testing methodologies to be used, as the use of one methodology over another depends on the type of product or the target market. In addition, biomechanical criteria that rule slipping have been identified, and also the test conditions according to applicable standards have been analysed, in order to decide on which extent they comply (or not) with the aforementioned criteria. The resulting knowledge has been transferred to standardisation committees representing the footwear and flooring industries. After the project completion, discussions with the committees concerned are still taking place, mainly by ITC and INESCOP, with the final objective that - in the short term - manufacturers from both industries operate under more efficient standards to evaluate the gripping properties of their products.
The development of technology aiming at the optimisation of non-slip performance of products, which can be used during the design stage, has also been an objective of the ULTRAGRIP project. It is worth mentioning the development of innovative high-speed image acquisition technology for the footwear sole-ground interface, which allows experts to understand the evolution of contact-surfaces during gait, as well as the way contaminants can be drained from the pavement. This technology is essential for the study and understanding of the friction phenomenon which takes place between shoe sole and the pavement with each step. Also, innovative technology has been developed for the simulation of the gradual wear and tear shoe soles and the pavement are subjected to during their everyday usage, permitting us to not only evaluate the initial performance of the products against friction, but also the overall durability of said performance.
Tools for internal use in companies of both sectors have also been developed. On the one hand, the 'CoF calculator', that is software able to calculate the coefficient of friction (CoF) for different types of products, which can be used in the design stage. This new software, which is based on CoF predictive mathematical models, allows for a more direct, efficient, and cost-effective way to proceed to a final prototype without first having carried out previous validation tests. On the other hand, the resulting knowledge has been used in the development of easy-to-understand guidelines for the selection of the most suitable footwear and floorings for different environmental conditions or different applications.
Project context and objectives:
The European SMEs working in the footwear industry are in a difficult and particularly complex period, due to the fact that the global market competition demands extreme flexibility and speed in the production to meet the high customisation needs of customers. In fact consumers are showing a growing tendency in favouring products more and more oriented to the individual, paying attention to the accuracy of manufacturing, to the quality of material, to the care of personal health and comfort.
Furthermore, by 2020 the world's middle class is expected to rise up to include 52 % of the global population: middle class will almost double in developing countries where sustained economic growth is lifting people above the poverty line fast.
Such a scenario proves how the development of high quality manufactured products is, and will remain, an utterly important factor of growth for both the economy and the identity of Europe.
The footwear industry, and in particular casual and sport shoe targeted factories as the ones involved in the project, needs integrated design and production process innovation in order to reduce the time-to-market and the production costs, to increase product diversification in conjunction with a small batch production, and a high fashion content and quality of the product.
Moreover, the footwear market is highly globalized and the EU industry is facing very thorough competition from low labour cost countries. Over the last decades, the EU industry has been gradually pushed towards the higher end of the market by cheap footwear from these low labour cost countries. Besides, the EU industry is the global leader as regards high quality footwear with 190 million pairs exported worth around EUR 4 billion.
The flooring sector is facing a similar situation to the footwear sector. In the period between 2001 and 2006, world ceramic tile increased by 40 %. Most of the increase in production took place in Asian countries, especially China.
Today, competition from Far East countries is on low labour cost, impacting on 40 % of the footwear price. Driven by such an odd challenge, there is a strong tendency of companies to delocalise the production activities, with a consequent effect of lowering the quality and compromising the organisational effectiveness.
Likewise, the legislation in force in the European Union clearly establishes the safety requirements of protective footwear, one of them being the footwear's slip resistance property. The interest to increase the anti-slip properties of professional footwear is now expanding more and more to other types of footwear, such as sport shoes, leisure, etc., although there is no legislation forcing the fulfilment of this feature in these kinds of footwear. On the other hand, floorings must achieve the CE marking requirements according to the EU Construction Products Directive (89/106/EEC), which also include the declaration of slip resistance.
The common interest in both sectors is avoiding injuries caused by slipping (around 44 % of accidents in the workplace are caused by slipping). They also have a common need to generate knowledge about the friction phenomenon and to have the usable tools available for the manufacturers in the fashion of guidelines for the improvement of anti-slip properties and specific software that allow the harmonisation of criteria and the achievement of efficient, quick and cost-effective solutions to slip problems.
The main objective of the project has been to develop guidelines and specific software which could be used as a design tools for soles and floorings to optimise their performance in relation to slipping. To achieve this, it has been necessary to generate information and develop advanced technologies for obtaining data about friction processes which not available at the moment.
The availability of these tools will impact on a reduction in the design-production time of the footwear as well as a reduction in costs, as unnecessary costs could be avoided, such as those derived from amendments to sole moulds, materials used for the production of prototypes, slip resistance validation tests following prototyping, etc. With the project, it has been obtained a change in the sole prototype production process.
Project results:
In particular the following results for the project, or set of solutions, have been identified:
Res 1. Correlations between the assessment methods used in the footwear and flooring sectors (floorings: prEN 15673-1, DIN 51130, UNE ENV 12633; footwear: EN ISO 13287) that allow an objective definition of the normative slipping criteria to be addressed. Fulfilment of the methods with the biomechanical criteria that rule slipping.
Res 2. Reference materials, both for flooring and footwear, to be jointly used in both sectors for the validation-calibration of the testing methods specific for each field, in order to harmonise the footwear and flooring manufacturers' approach.
Res 3. High-speed image acquisition technology (HSIAT) for in the sole-contaminant-flooring interface.
Res 4. Software for HSIAT, which measures the evolution of contact surface between sole and pavement during gait.
Res 5. Knowledge about the existing interactions between sole-contaminant-flooring in a molecular scale.
Res 6. Assessment of performance durability and maintenance with reference to the wear processes, surface contamination, etc.
Res 7. Novel real-scale wear simulation technology for footwear and floorings.
Res 8. Slip behaviour predicting software for the different combinations of floorings and footwear, as a design tool for both sectors and for the precise definition of the requirement level that ensures user's safety.
Res 9. Guidelines for recommendations-requirements on improving slip resistance for both sectors, directed towards the different friction conditions (sole, flooring and contaminant combinations), based on specific knowledge that allow the sole and flooring manufacturers to better adequate their materials and designs to the safety and comfort requirements demanded by manufacturers and end-users. This will all be directed towards the improvement of product quality in both sectors.
These results can be classified in three different categories: technology, tools and knowledge. More detailed description of results, which belongs to SMEs partners, is available at ULTRAGRIP showroom: http://showroom.ultragrip.eu.
Results are described below:
Technology
High-speed image acquisition technology:
This technology provides image sequences of the contact between the footwear sole and the ground with enough spatial and temporal resolution to allow a detailed view and analysis of the sole contact at any point in time. The use of surface pollutants is also considered.
It consists in a 10 m walkway with a metal frame supporting an illuminated glass plate, an inclined mirror and the camera to film the sole contact. It has been integrated into a motion analysis lab, meaning that the subjects' and footwear motion as well as the appearing ground reaction forces can be measured simultaneously to the high speed video sequences of the sole contacting the ground. Covering the glass with a thin, opaque, inextensible layer ensures high contrast images regardless of the sole colour.
This technology is available at Functional Analysis Laboratory of INESCOP.
Novel real-scale wear simulation technology for footwear:
A technology for simulation of wear produced on soles under real use conditions has been developed, where it is possible to remove one layer of material, with specified thickness, from the tread surface of the sole. Using this method, it is possible to assess the change in the coefficient of friction before and after the use of the soles.
It consists in an abrasive disc attached to a holder and placed on the tread surface. It makes several runs longitudinally at specified rpm on the sole / test-piece, always in the same direction. Finally, the tread surface is cleaned using clean, compressed air.
Novel real-scale wear simulation technology for floorings
The evaluation of the slip resistance performance of floorings has been carried out on ex-factory samples until now, due to current wear methods not allowing the acquisition of enough abraded surface area for subsequent slip resistance testing.
A new technology for simulation of wear on floorings under real service conditions has been developed. Using this method, it is possible to assess the change in the coefficient of friction throughout the useful life of the floor.
It consists in a single industrial polishing head mounted above a reversible conveyor belt, which includes six posts for the abrasive blocks covered by scouring pads (85 % quartz with an average particle size of 45 µm). Using this technology, a homogeneous middle abraded area of approximately 15 cm is obtained, which allows slip tests to be carried out with the pendulum method. This wear method has been validated by comparison with the results obtained on floorings subjected to real exposure under indoor and outdoor conditions.
Tools
Image acquisition and analysis software for the high-speed recording technology
This software analyses the image sequences of the contact between the footwear sole and the ground, obtained with the high-speed recording technology developed and allows the sole contact area to be obtained at any point in time, either during machine tests or during real walking trials. Also, this software allows visualising the ability to drain the contaminant present on the pavement.
Slip behaviour predicting software
A software tool for the prediction of the CoF for footwear and pavements has been developed. The software predicts the CoF for: footwear, indoor pavements, outdoor pavements and industrial pavements.
For each product, there is a screen in which a questionnaire is made asking for qualitative or quantitative characteristics of the material or the design of the product, all of them having a big influence on the friction properties of the product ('input parameters'). After this introduction of 'parameters', the software acts as a 'CoF calculator' by using different CoF-predictive mathematical models also developed during the project.
Guidelines for recommendations-requirements
Slip resistance depends on many factors: floorings (type, profile, roughness,..) ,footwear's properties and design, presence of contaminants (water, oil, sand,..), type of activities (sports, leisure, working activities) and psycho-physical wellbeing of users. Many injuries caused by slipping could be avoided if appropriate sole materials and tread, as well as adequate floorings were chosen. But so far the existing legislation regarding the slip resistance properties of footwear and floorings are inadequate in certain cases and in certain countries. In some countries, like Spain, there is national regulation on slipperiness, in others, like Slovenia such document does not exist so far.
Therefore, based on the knowledge obtained within the ULTRAGRIP project, supported by relevant requirements from standards and national regulations, as well as with literature data, a Guideline for the selection of floorings and footwear has been developed. The present guidelines represent an attempt to improve the current slip resistance regulations and it will be helpful to designers, producers, investors and users. It is presented in two formats, according to the environment conditions or to the intended use, in order that users can easily find recommendations for the selection of the most adequate footwear and floorings for different applications.
Knowledge
Biomechanical criteria that rule slipping
A slip occurs whenever the horizontal force needed for a given step exceeds the horizontal force that the interface sole / ground and the potential presence of pollutant allow to achieve, given the vertical force applied at that instant.
The physical magnitude quantifying the slipperiness is the coefficient of friction (CoF), also referred to with the Greek letter 'µ', equals to Fr/N, where Fr = friction force (force parallel to the surface and opposing to the direction of slipping) and N = normal force (force orthogonal to the surface pushing the footwear against it).
In order to predict slipping behaviour, relying only on the mechanical properties and the geometry of the sole and surface materials is not sufficient. The biomechanics of walking need to be considered as well.
For any activity the required CoF (rCoF) can be determined by measuring the GRF during several representative and successful trials of that activity. The highest value of the quotient between horizontal and vertical force will indicate the required CoF. The instant of that maximum value will be one of the critical instants and the position of the sole relative to the ground, the surface area and geometry being in contact with the ground at that instant also need to be part of the analysis. There might be more than one critical instant; in walking there are typically three: The instant of heel strike, short after when the first maximum is reached and at push off, when the second maximum is achieved. At the ULTRAGRIP project, the rCoF has been calculated for a range of actions covering most of the activities of daily life and some sporting actions as well. In addition, for walking, the other relevant instantaneous biomechanical variables have been determined as well.
The gained knowledge can be used to improve sole design, but also might serve to improve the existing standard tests in order to provide more realistic values.
Correlations between the slip testing methods
A complete experimental work has been done with the most commonly used slip testing methods for floorings (pendulum and ramp) and shoes (EN ISO 13287), and using an extensive selection of types of footwear and floorings. In order to avoid interferences from the calibration procedures of the testing methods and to ensure that neither the footwear sole nor the flooring was becoming worn out during the test series, common reference floors and soles were also used.
From the analysis of the results, it has been concluded that the lack of correlation between the current standard test methods comes from the different testing conditions, with a major influence from the contaminant and the shoes / slider used.
The major results obtained from this study are the following:
- Using flat soles/sliders on flat floors with water contamination, the three methods show good correlation up to 0.6 CoF units.
- When testing profiled surface floorings, the pendulum method provides conservative results compared to those obtained with other methods.
- Test methods using profiled soles (ramp and shoe tester) shows less repeatability and higher scatter.
It is therefore recommended to establish different methods for each of the relevant actual uses, ensuring that the test conditions (shoe, contaminant and floor) are representative of the ones expected in the shoe or floor applications to be simulated.
Reference materials, both for footwear and floorings
The three slip testing methods studied and compared in ULTRAGRIP project corresponding to footwear and flooring sectors are as follows:
- method of EN ISO 13287:2007 (used by the footwear sector)
- ramp method of DIN 51130 and DIN 51097 (used by the flooring sector)
- pendulum method described in many standards for polished and unpolished surfaces ENV 16633, stone EN 14231, clay paving units.
EN 1344, road surfaces 13036-4, road marking materials EN 1436, and wood floorings EN 14342. It is also defined as a single method for all types of floorings in British standard BS 7976-2, and one of the two methods in Australian standard AS/NZ S4663 for existing pedestrian surface, and in AS/NZS 4586 for new pedestrian surfaces (used by the flooring sector).
In each standard involved there is a set of reference materials that must be used in order to obtain correct values of friction coefficients (CoF). If footwear is tested, then a floor is used as the reference material for comparison (either steel or a ceramic tile). If floorings are tested, the reference material shall be footwear or an elastomeric material test-piece, as stated in the test method used.
But in the ULTRAGRIP project, a big effort has been made to define common reference materials that can be used by all the methods aforementioned. So, it has been defined different combinations of floors and shoes / sliders that generate friction values around the biomechanical critical values (approximately 0,30 CoF), and that show high wear resistance, in order to avoid changes in the results due to progressive wear. Measurements of friction coefficients using these common reference materials have permitted to compare the slipping methods and establish the existing correlations between them.
For example, the footwear sample for testing according to different slipping test methods studied in the project (ramp method, footwear method, biomechanical method, etc.) has been unified. It consists of a size 42 pair of shoes with removable sole, which permit to change the material and the design of the sole without changing the rest of the footwear.
Molecular interactions between sole-contaminant-floor
In this study it has been determined the correlation between surface energy (E) and CoF, both in footwear and floorings. For this, E and CoF have been determined in commercial and customised solings and floorings.
E is obtained from the values of the contact angles (?) measured using different reference liquids (at least two with different polar natures) and applying diverse equations. CoF is obtained according to footwear test method EN-ISO 13287:
- CoF in solings: solings (76 x 25 x 7 mm) slipping over Eurotile 2 flooring with angle of 7o,
- CoF in floorings: reference rubber Slider 96 (76 x 25 x 7mm) slipping over floorings with angle of 7 o.
A trend between E and CoF has been observed: The higher the wettability, the higher surface energy, the higher the CoF. But an important increase in E is needed to obtain a significant increase in CoF.
Evaluation of footwear friction performance durability and maintenance
The requirements that are currently in force for footwear refer exclusively to professional footwear, according to standards EN ISO 20345-6-7. However, no reference is made to preserving the slipping performance of footwear throughout its useful life. For this reason, the change in the friction coefficient of footwear (CoF) caused by the wear degree of the soles at two levels: soles from conducted wear trials of footwear, and soles from laboratory wear treatments, has been analysed.
Different wear trials were conducted in order to evaluate the changes in CoF because of the wear, according to the methodology of EN-ISO 13287:2007. Final users of these trials have been:
Sports wear trials:
- handball club 'Elche',
- handball club 'Elda Prestigio',
- futsal club 'El Pozo Murcia',
- other futsal users,
- seven-a-side football users,
- running users.
Professional wear trials:
- the Vinalop? Area Fire partment (Alicante),
- Master Chocolatier Paco Torreblanca.
Some of these wear trials have been also used for project dissemination by means of disclosing information in the media about the collabouration between the ULTRAGRIP project and different groups of renowned users.
Footwear wear trials results and laboratory wear results (using the developed wear technology) indicate that it is necessary that the slipping testing methodology considers a more aggressive laboratory wear treatment of the sole as a preparation method of the sample before testing. That is why the ULTRAGRIP proposal is testing the footwear sample before (as established in the current standard) and after the wear treatment developed in the project.
Evaluation of floorings friction performance durability and maintenance
In the case of the flooring sector, the regulation in force, for example in Spain, derived from the publication of the technical building code (DB-SUA), not only establishes some friction requirements for floorings for public access sites but also requires the maintenance of their performance throughout their whole useful life.
In situ wet pendulum studies on the changes of slip resistance due to wear at indoor and outdoor actual conditions have been developed in different places: In the town of Castellon at University Jaume I and Santa Clara Square; In Lujbliana at ZAG facilities, kofja Loka bridge and St. Anton church. The changes on the surface due to the freezing action (in the presence of salts which are commonly used to reduce the occurrence of ice) have been studied too. The results confirm that the slip resistance performance of most flooring materials decreases during their first year in service, especially in outdoor conditions.
These studies have allowed the validation of the new technology for simulation of wear on floorings, which has been used to analyse the durability of different types of floors. The results show that the changes on friction depend on the nature of the material and its surface design. So the ULTRAGRIP project is testing friction on abraded flooring surfaces when the floorings are expected to be used in outdoor areas or areas with direct outdoor access.
Friction coefficient mathematical predictive models
Four different mathematical predictive models have been developed, to predict the friction behaviour in each one of the following four products:
- footwear,
- indoor pavements,
- outdoor pavements,
- industrial pavements.
The possible input parameters (P) of the models have been a priori defined based on Inescop and ITC's wide experience and the development of specific experiment designs. Some of these parameters could be qualitative and other quantitative, which could be part of the polynomial-type mathematical function for CoF prediction.
CoF= f(P).
The models have been created in an attempt for them to be, in addition to being predictive, explanatory as well. In other words, the has parameters which must mandatorily be included in the models and their sign have been identified; all this based on the studies carried out, so that the final mathematical functions could make physical sense and explain the friction phenomenon predicted by the model.
Each model comprises different polynomials (LM), in such a way that the CoF is estimated using one or another depending on the input parameter values of the model. In other words, each polynomial takes part when certain conditions of the input parameters occur.
These models are the basis of the CoF prediction software developed in the project.
White paper on new standard for testing footwear in different environments / conditions
The European standardised method for measuring CoF in footwear is described in the standard EN-ISO 13287:2007. Only professional footwear has to fulfil the normative requisites.
In this method, the footwear is placed on the reference testing surface (the floor) and a normal force (v) is applied. Then the surface slides below the shoe in a horizontal direction at a constant speed. The vertical load as well as the force required to move the floor are measured and this way the dynamic friction coefficients are then calculated and the footwear slipping response can be graded according to their grip.
This method is robust, repeatable and in general, according to experience following years of usage, a valid method of testing slipping resistance. This means that, generally speaking, footwear passing these tests does not show slipping problems and very often footwear not reaching the prescribed minimal values, do have slipping problems in real use. However based on the experiences gained during the ULTRAGRIP project, some improvements have been proposed.
First of all, it should be pointed out, that the existing method is valid when the main task to be performed is walking and possibly even heel to toe running. So this standard is fine to evaluate casual and safety footwear. However, when it comes to sport shoes, the friction requirements tested with the existing method do not match with those required for the sport shoes to perform appropriately. Therefore improvements are proposed in two different sections: One for casual and safety footwear and another for sports shoes.
The ULTRAGRIP improvements proposed to the current standard which measures the footwear friction, were presented to the standardisation committees (23 May 2012 at the CEN-TC161-WG3 meeting, held at INESCOP-Elda-Spain).
White paper on new standard for testing FLOORINGS in different environments / conditions
The results of the experimental work confirm that it is not possible to predict the friction using the results coming from a different test conditions than the actual ones. So the ULTRAGRIP project proposes to use a new approach for application based standards which jointly consider the influence of the expected footwear, contaminant and floorings.
ULTRAGRIP results were presented to the ISO TC 189 standardisation committee 'Ceramic tile' on 15 November 2011 at the meeting which took place in London.
Proposal of new application based standards
1) Floors for indoor areas without direct outdoor access
Test method: pendulum / flat rubber IRHD 57 slider
Contaminant: water
Reference floors: Ceramic1, Eurotile-1 and Ceramic2
Wear simulation conditioning: not applicable.
2) Floors for indoor areas with direct outdoor access
Test method: pendulum / flat rubber IRHD 57 slider
Contaminant: water
Reference floors: Ceramic1, Eurotile-1 and Ceramic2
Wear simulation conditioning: 100 cycles.
3) Floors for outdoor areas
Test method: pendulum/flat rubber IRHD 57 slider
Contaminant: water
Reference floors: Ceramic1, Eurotile-1 and Ceramic2
Wear simulation conditioning: accumulated cycles till stabilisation.
4) Floors for working areas
Test method: Ramp & UVEX safety footwear
Contaminant: oil
Reference floors: Ceramic StI, Ceramic StII and Ceramic StIII
Wear simulation conditioning: when requested, accumulated cycles till stabilization.
5) Floors for wet barefoot areas
Test method: ramp barefoot
Contaminant: water + 0,5% sodium lauryl sulphate
Reference floors: Ceramic3, Eurotile-1 and Ceramic4
Wear simulation conditioning: not applicable.
Potential impact:
The project has contributed to enhance SMEs' competitive strength by supporting the creation of design tools for the improvement of the slip behaviour of products in footwear and pavement sectors. The market need for innovative anti-slip products for a variety of applications (shopping malls, hospitals, sport facilities and other public places) which represents a large market potential that is typically suitable for small and medium enterprises, where the production flexibility of the SME companies is of a major competitive advantage.
The legislation in force in the European Union clearly establishes the safety requirements of protective footwear, one of them being the footwear's slip resistance property. The interest to increase the anti-slip properties of professional footwear is now expanding more and more to other types of footwear, such as sport shoes, leisure, etc., although there is no legislation forcing the fulfilment of this feature in these kinds of footwear. On the other hand, floorings must achieve the CE marking requirements according to the EU Construction Products Directive (89/106/EEC), which also include the declaration of slip resistance. The common interest in both sectors is avoiding or reducing injuries caused by slipping (around 44 % of accidents in the workplace are caused by slipping). This highlights that the existing legislation regarding the slip resistance properties of footwear and floorings is inadequate in certain cases.
This project proposal deals with reduction of slipping risks. According to ESENER (Enterprise survey on new and emerging risks that examines how health and safety is managed in practice in European workplaces), the results to the following question indicate the importance of safety equipment in order to avoid accidents: 'For each of the following issues, please tell me whether it is of major concern, some concern or no concern at all in your establishment. Accidents'.
Apart from the importance that firms give to this issue, citizens also demand for better health and security at their workplace (results from Pan-European opinion poll on occupational safety and health-2012).
For all the above, the participant SMEs, which are footwear and flooring manufacturers, need to differentiate their products from those imported from low wage countries by means of the addition of attributes that such imported products do not incorporate. Among these attributes, the slip resistance plays an essential role in both sectors.
Currently, sole manufacturers design their models to be anti-slip using basic design criteria, often relying on their intuition and previous experience. The problem resides in the lack of design tools that can be used in the conception of footwear, which would make prototyping much cheaper, quicker and more effective in creating an answer to the friction that the shoe would be subjected to when used.
The availability of these tools has generated an impact on a reduction in the design-production time of the footwear as well as a reduction in costs, as unnecessary costs could be avoided, such as those derived from amendments to sole moulds, materials used for the production of prototypes, slip resistance validation tests following prototyping, etc. On the other hand, SME flooring manufactures has to carry out a series of different slip resistance tests to comply with the various national requirements, the amount being dependent on the number of countries they export and their respective regulations. The successful result of the project has also been highly beneficial for flooring manufacturers as a cost reduction and a way to speed the time to the market of his innovative products.
With the project, it is possible to change the prototype sole production process. This entails:
- fabrication of one mould with the moulding cavity having the prototype shape,
- moulding of some samples of soles with the final sole material selected,
- slip resistance testing of the sole samples according to current standards.
If friction coefficient does not pass the requirements, then changes must be introduced in the 2D - 3D design of the sole, and the prototyping process must start again. Usually, this validation process is repeated two or three times, making double or triple the prototyping costs, and increasing the process time.
Impact due to internal use of ULTRAGRIP tools on participating footwear SMEs (KELME, Ruizalejos and Basepro) is related with previous data.
- Reduction in time for prototyping:
Manufacturers design their models to be anti-slipping using basic design criteria, often relying on their intuition and previous experience. But, with the new design tools they will go directly to the optimum prototype, avoiding repetitions (12 days instead of 55 days).
- Reduction in prototyping costs:
The reduction in time for prototyping will directly imply a reduction in the cost of this operation. Current situation is that manufacturers need to modify the first sole prototype including pattern changes because the friction behaviour is not the needed one. Then changes must be introduced in the 2D - 3D design of the sole, and the prototyping process must start again. Usually, this validation process is repeated two or three times, making double or triple the prototyping costs. This will mean an indicator of 33 % or 67 %. More drastic scenario has been considered (67 %).
- Reduction in production costs:
The reduction in the costs of prototyping will directly imply a reduction in final production costs, always with lower impact than the first two indicators explained above.
- Product quality:
The design tools developed will imply a final increase in anti-slipping behaviour of products.
- Overall time-to-market:
The reduction in designing-prototyping times will directly imply a reduction in time-to-market (57 days onstead of 100 days).
- Market share:
An increase in quality of the products will directly imply a higher level of satisfaction for consumers.
- New skills:
Traditional designing-prototyping operation will be replaced with new design tools based on knowledge, so they will imply a better qualification and a knock-on effect over young people and designers.
Vender and Exagres, as polymeric flooring producers, will have similar impact than those obtained by footwear producers SME partners: they will reduce costs and they will find a way to speed the time to the market of their innovative products. Nevertheless, VERN?S and Marmor will obtain lower impact due to the type of article they manufacture (natural stones, etc.) in which design is not as important as could be in other kind of products as soles, polymeric pavements, etc.
Impact on SMEs also will come from results commercialisation. The project results can be classified in three different categories: technology, tools and knowledge (see http://showroom.ultragrip.eu for details). Project results that can give direct revenues to the SMEs partners through their external commercialisation are those of 'technology' and 'tools' types:
Res 3. Technology for high-speed image acquisition in the sole-contaminant-flooring interface. Estimated selling price EUR 20 000/unit.
Res 4. Image acquisition and analysis software for the high-speed recording technology. Estimate prices EUR 4000.
Res 7. Novel real-scale wear simulation technology for footwear and floorings. Estimate price EUR 15 000/unit.
Res 8. Slip behaviour predicting software for the different combinations of floorings and footwear, as a design tool for both sectors and for the precise definition of the requirement level that ensures user's safety. Estimated price EUR 3000/unit.
Res. 3 and Res.4 are only addressed to footwear sector, as the high speed technology uses a transparent crystal as pavement; Res. 7 and Res. 8 are addressed to both sector manufacturers.
According to previous figures, a first hypothesis on the total economic benefit for each individual SME partner is based on the cost of the project to implement the planned solutions, the current revenues of the companies and the forecast revenues due to internal use of project results and external commercialisation of them. The forecast revenues are calculated for the first three years after the end of the project and they are based on 5 %, 10 % and 15 % of current revenues respectively.
ULTRAGRIP project provides also other advantages like:
- development of new shoe models with better grip performance,
- development of new pavement with better grip performance,
- increasing in the number of orders, due to a higher level of satisfaction for consumers and shorter time to market,
- better flexibility of the production, since the developed design tools do not limit the style,
- better differentiation of European products from those imported from low wage countries by means of the addition of slip resistance attribute that such imported products do not incorporate,
- possibility to maintain the production in the origin country, without the need of delocalization,
- criteria harmonisation in footwear and pavement sectors as regards the assessment of slip resistance.
Project website: http://www.ultragrip.eu
Project FaceBook profile: http://www.facebook.com/pages/ULTRAGRIP/140415302728444
Showroom of project results: http://showroom.ultragrip.eu
Main project contacts
Dr Cristina Llobell Andres (Project coordinator)
RTD Manager
Inescop - Instituto Technolygico del Calzado y Conexas
Tel: +34-965-395213
Fax: +34-965-381045
E-mail: cllobelll@inescop.es
ULTRAGRIP consortium
1. INESCOP (Spain)- Coordinator
Contact person: Cristina LLobell
Email: cllobelll@inescop.es
2. KELME - New Millenium Sports, S.L. (Spain)
Contact persons: Luca Gios, Luis Maestre
Email: luca@kelme.es; lmaestre@kelme.es
3. Cauchos Ruiz-Alejos, S.A. (Spain)
Contact person: Ismael Ru?z-Alejos
Email: ismael@cauchosruiz-alejos.com
4. Vernis, S.A. (Spain)
Contact persons: Anabel Castell?, M. Carmen Segura
Email: acastello@vernis.es; mcsegura@vernis.es
5. Basepro - Base Protection SRL (Italy)
Contact persons: Cataldo de Luca, Mauro Dimolfetta
Email: rd@basepro.it; m.dimolfetta@basepro.it
6. Marmor - Marmor Hotavlje Druzba za Obdelavokamna dd Hotavlje (Slovenia)
Contact person: Zdenko Mrdja
Email: zdenko.mrdja@m-h.si
7. Vender - Vender Proizvodnja Trgovina Inzeniring in Zastopstvo DOO (Slovenia)
Contact person: Dusan Verdel
Email: info@vender.si
8. ITC - Asociaci?n de Investigaci?n de las industrias ceramicas AICE (Spain)
Contact person: Gonzalo Silva
Email: gonzalo.silva@itc.uji.es
9.ZAG - Zavod za Gradbenistvo Slovenije (Slovenia)
Contact person: Vilma Ducman
Email: vilma.ducman@zag.si
10. Exagres, S.A. (Spain)
Contact persons: Crist?bal Badenes, Sara Rubert
Email: cbadenes@versatile.es; srubert@versatile.es
During the ULTRAGRIP project, the standard methods currently available for testing slip-resistance properties of footwear and flooring products have been studied in detail. This allowed for the identification of correlations in measurements shared by the two industries. These findings have been very interesting, especially for those project participants belonging to the flooring industry. This is due to the fact that, in contrast to the footwear industry, this sector and the related standardisation committees cannot reach an agreement regarding the testing methodologies to be used, as the use of one methodology over another depends on the type of product or the target market. In addition, biomechanical criteria that rule slipping have been identified, and also the test conditions according to applicable standards have been analysed, in order to decide on which extent they comply (or not) with the aforementioned criteria. The resulting knowledge has been transferred to standardisation committees representing the footwear and flooring industries. After the project completion, discussions with the committees concerned are still taking place, mainly by ITC and INESCOP, with the final objective that - in the short term - manufacturers from both industries operate under more efficient standards to evaluate the gripping properties of their products.
The development of technology aiming at the optimisation of non-slip performance of products, which can be used during the design stage, has also been an objective of the ULTRAGRIP project. It is worth mentioning the development of innovative high-speed image acquisition technology for the footwear sole-ground interface, which allows experts to understand the evolution of contact-surfaces during gait, as well as the way contaminants can be drained from the pavement. This technology is essential for the study and understanding of the friction phenomenon which takes place between shoe sole and the pavement with each step. Also, innovative technology has been developed for the simulation of the gradual wear and tear shoe soles and the pavement are subjected to during their everyday usage, permitting us to not only evaluate the initial performance of the products against friction, but also the overall durability of said performance.
Tools for internal use in companies of both sectors have also been developed. On the one hand, the 'CoF calculator', that is software able to calculate the coefficient of friction (CoF) for different types of products, which can be used in the design stage. This new software, which is based on CoF predictive mathematical models, allows for a more direct, efficient, and cost-effective way to proceed to a final prototype without first having carried out previous validation tests. On the other hand, the resulting knowledge has been used in the development of easy-to-understand guidelines for the selection of the most suitable footwear and floorings for different environmental conditions or different applications.
Project context and objectives:
The European SMEs working in the footwear industry are in a difficult and particularly complex period, due to the fact that the global market competition demands extreme flexibility and speed in the production to meet the high customisation needs of customers. In fact consumers are showing a growing tendency in favouring products more and more oriented to the individual, paying attention to the accuracy of manufacturing, to the quality of material, to the care of personal health and comfort.
Furthermore, by 2020 the world's middle class is expected to rise up to include 52 % of the global population: middle class will almost double in developing countries where sustained economic growth is lifting people above the poverty line fast.
Such a scenario proves how the development of high quality manufactured products is, and will remain, an utterly important factor of growth for both the economy and the identity of Europe.
The footwear industry, and in particular casual and sport shoe targeted factories as the ones involved in the project, needs integrated design and production process innovation in order to reduce the time-to-market and the production costs, to increase product diversification in conjunction with a small batch production, and a high fashion content and quality of the product.
Moreover, the footwear market is highly globalized and the EU industry is facing very thorough competition from low labour cost countries. Over the last decades, the EU industry has been gradually pushed towards the higher end of the market by cheap footwear from these low labour cost countries. Besides, the EU industry is the global leader as regards high quality footwear with 190 million pairs exported worth around EUR 4 billion.
The flooring sector is facing a similar situation to the footwear sector. In the period between 2001 and 2006, world ceramic tile increased by 40 %. Most of the increase in production took place in Asian countries, especially China.
Today, competition from Far East countries is on low labour cost, impacting on 40 % of the footwear price. Driven by such an odd challenge, there is a strong tendency of companies to delocalise the production activities, with a consequent effect of lowering the quality and compromising the organisational effectiveness.
Likewise, the legislation in force in the European Union clearly establishes the safety requirements of protective footwear, one of them being the footwear's slip resistance property. The interest to increase the anti-slip properties of professional footwear is now expanding more and more to other types of footwear, such as sport shoes, leisure, etc., although there is no legislation forcing the fulfilment of this feature in these kinds of footwear. On the other hand, floorings must achieve the CE marking requirements according to the EU Construction Products Directive (89/106/EEC), which also include the declaration of slip resistance.
The common interest in both sectors is avoiding injuries caused by slipping (around 44 % of accidents in the workplace are caused by slipping). They also have a common need to generate knowledge about the friction phenomenon and to have the usable tools available for the manufacturers in the fashion of guidelines for the improvement of anti-slip properties and specific software that allow the harmonisation of criteria and the achievement of efficient, quick and cost-effective solutions to slip problems.
The main objective of the project has been to develop guidelines and specific software which could be used as a design tools for soles and floorings to optimise their performance in relation to slipping. To achieve this, it has been necessary to generate information and develop advanced technologies for obtaining data about friction processes which not available at the moment.
The availability of these tools will impact on a reduction in the design-production time of the footwear as well as a reduction in costs, as unnecessary costs could be avoided, such as those derived from amendments to sole moulds, materials used for the production of prototypes, slip resistance validation tests following prototyping, etc. With the project, it has been obtained a change in the sole prototype production process.
Project results:
In particular the following results for the project, or set of solutions, have been identified:
Res 1. Correlations between the assessment methods used in the footwear and flooring sectors (floorings: prEN 15673-1, DIN 51130, UNE ENV 12633; footwear: EN ISO 13287) that allow an objective definition of the normative slipping criteria to be addressed. Fulfilment of the methods with the biomechanical criteria that rule slipping.
Res 2. Reference materials, both for flooring and footwear, to be jointly used in both sectors for the validation-calibration of the testing methods specific for each field, in order to harmonise the footwear and flooring manufacturers' approach.
Res 3. High-speed image acquisition technology (HSIAT) for in the sole-contaminant-flooring interface.
Res 4. Software for HSIAT, which measures the evolution of contact surface between sole and pavement during gait.
Res 5. Knowledge about the existing interactions between sole-contaminant-flooring in a molecular scale.
Res 6. Assessment of performance durability and maintenance with reference to the wear processes, surface contamination, etc.
Res 7. Novel real-scale wear simulation technology for footwear and floorings.
Res 8. Slip behaviour predicting software for the different combinations of floorings and footwear, as a design tool for both sectors and for the precise definition of the requirement level that ensures user's safety.
Res 9. Guidelines for recommendations-requirements on improving slip resistance for both sectors, directed towards the different friction conditions (sole, flooring and contaminant combinations), based on specific knowledge that allow the sole and flooring manufacturers to better adequate their materials and designs to the safety and comfort requirements demanded by manufacturers and end-users. This will all be directed towards the improvement of product quality in both sectors.
These results can be classified in three different categories: technology, tools and knowledge. More detailed description of results, which belongs to SMEs partners, is available at ULTRAGRIP showroom: http://showroom.ultragrip.eu.
Results are described below:
Technology
High-speed image acquisition technology:
This technology provides image sequences of the contact between the footwear sole and the ground with enough spatial and temporal resolution to allow a detailed view and analysis of the sole contact at any point in time. The use of surface pollutants is also considered.
It consists in a 10 m walkway with a metal frame supporting an illuminated glass plate, an inclined mirror and the camera to film the sole contact. It has been integrated into a motion analysis lab, meaning that the subjects' and footwear motion as well as the appearing ground reaction forces can be measured simultaneously to the high speed video sequences of the sole contacting the ground. Covering the glass with a thin, opaque, inextensible layer ensures high contrast images regardless of the sole colour.
This technology is available at Functional Analysis Laboratory of INESCOP.
Novel real-scale wear simulation technology for footwear:
A technology for simulation of wear produced on soles under real use conditions has been developed, where it is possible to remove one layer of material, with specified thickness, from the tread surface of the sole. Using this method, it is possible to assess the change in the coefficient of friction before and after the use of the soles.
It consists in an abrasive disc attached to a holder and placed on the tread surface. It makes several runs longitudinally at specified rpm on the sole / test-piece, always in the same direction. Finally, the tread surface is cleaned using clean, compressed air.
Novel real-scale wear simulation technology for floorings
The evaluation of the slip resistance performance of floorings has been carried out on ex-factory samples until now, due to current wear methods not allowing the acquisition of enough abraded surface area for subsequent slip resistance testing.
A new technology for simulation of wear on floorings under real service conditions has been developed. Using this method, it is possible to assess the change in the coefficient of friction throughout the useful life of the floor.
It consists in a single industrial polishing head mounted above a reversible conveyor belt, which includes six posts for the abrasive blocks covered by scouring pads (85 % quartz with an average particle size of 45 µm). Using this technology, a homogeneous middle abraded area of approximately 15 cm is obtained, which allows slip tests to be carried out with the pendulum method. This wear method has been validated by comparison with the results obtained on floorings subjected to real exposure under indoor and outdoor conditions.
Tools
Image acquisition and analysis software for the high-speed recording technology
This software analyses the image sequences of the contact between the footwear sole and the ground, obtained with the high-speed recording technology developed and allows the sole contact area to be obtained at any point in time, either during machine tests or during real walking trials. Also, this software allows visualising the ability to drain the contaminant present on the pavement.
Slip behaviour predicting software
A software tool for the prediction of the CoF for footwear and pavements has been developed. The software predicts the CoF for: footwear, indoor pavements, outdoor pavements and industrial pavements.
For each product, there is a screen in which a questionnaire is made asking for qualitative or quantitative characteristics of the material or the design of the product, all of them having a big influence on the friction properties of the product ('input parameters'). After this introduction of 'parameters', the software acts as a 'CoF calculator' by using different CoF-predictive mathematical models also developed during the project.
Guidelines for recommendations-requirements
Slip resistance depends on many factors: floorings (type, profile, roughness,..) ,footwear's properties and design, presence of contaminants (water, oil, sand,..), type of activities (sports, leisure, working activities) and psycho-physical wellbeing of users. Many injuries caused by slipping could be avoided if appropriate sole materials and tread, as well as adequate floorings were chosen. But so far the existing legislation regarding the slip resistance properties of footwear and floorings are inadequate in certain cases and in certain countries. In some countries, like Spain, there is national regulation on slipperiness, in others, like Slovenia such document does not exist so far.
Therefore, based on the knowledge obtained within the ULTRAGRIP project, supported by relevant requirements from standards and national regulations, as well as with literature data, a Guideline for the selection of floorings and footwear has been developed. The present guidelines represent an attempt to improve the current slip resistance regulations and it will be helpful to designers, producers, investors and users. It is presented in two formats, according to the environment conditions or to the intended use, in order that users can easily find recommendations for the selection of the most adequate footwear and floorings for different applications.
Knowledge
Biomechanical criteria that rule slipping
A slip occurs whenever the horizontal force needed for a given step exceeds the horizontal force that the interface sole / ground and the potential presence of pollutant allow to achieve, given the vertical force applied at that instant.
The physical magnitude quantifying the slipperiness is the coefficient of friction (CoF), also referred to with the Greek letter 'µ', equals to Fr/N, where Fr = friction force (force parallel to the surface and opposing to the direction of slipping) and N = normal force (force orthogonal to the surface pushing the footwear against it).
In order to predict slipping behaviour, relying only on the mechanical properties and the geometry of the sole and surface materials is not sufficient. The biomechanics of walking need to be considered as well.
For any activity the required CoF (rCoF) can be determined by measuring the GRF during several representative and successful trials of that activity. The highest value of the quotient between horizontal and vertical force will indicate the required CoF. The instant of that maximum value will be one of the critical instants and the position of the sole relative to the ground, the surface area and geometry being in contact with the ground at that instant also need to be part of the analysis. There might be more than one critical instant; in walking there are typically three: The instant of heel strike, short after when the first maximum is reached and at push off, when the second maximum is achieved. At the ULTRAGRIP project, the rCoF has been calculated for a range of actions covering most of the activities of daily life and some sporting actions as well. In addition, for walking, the other relevant instantaneous biomechanical variables have been determined as well.
The gained knowledge can be used to improve sole design, but also might serve to improve the existing standard tests in order to provide more realistic values.
Correlations between the slip testing methods
A complete experimental work has been done with the most commonly used slip testing methods for floorings (pendulum and ramp) and shoes (EN ISO 13287), and using an extensive selection of types of footwear and floorings. In order to avoid interferences from the calibration procedures of the testing methods and to ensure that neither the footwear sole nor the flooring was becoming worn out during the test series, common reference floors and soles were also used.
From the analysis of the results, it has been concluded that the lack of correlation between the current standard test methods comes from the different testing conditions, with a major influence from the contaminant and the shoes / slider used.
The major results obtained from this study are the following:
- Using flat soles/sliders on flat floors with water contamination, the three methods show good correlation up to 0.6 CoF units.
- When testing profiled surface floorings, the pendulum method provides conservative results compared to those obtained with other methods.
- Test methods using profiled soles (ramp and shoe tester) shows less repeatability and higher scatter.
It is therefore recommended to establish different methods for each of the relevant actual uses, ensuring that the test conditions (shoe, contaminant and floor) are representative of the ones expected in the shoe or floor applications to be simulated.
Reference materials, both for footwear and floorings
The three slip testing methods studied and compared in ULTRAGRIP project corresponding to footwear and flooring sectors are as follows:
- method of EN ISO 13287:2007 (used by the footwear sector)
- ramp method of DIN 51130 and DIN 51097 (used by the flooring sector)
- pendulum method described in many standards for polished and unpolished surfaces ENV 16633, stone EN 14231, clay paving units.
EN 1344, road surfaces 13036-4, road marking materials EN 1436, and wood floorings EN 14342. It is also defined as a single method for all types of floorings in British standard BS 7976-2, and one of the two methods in Australian standard AS/NZ S4663 for existing pedestrian surface, and in AS/NZS 4586 for new pedestrian surfaces (used by the flooring sector).
In each standard involved there is a set of reference materials that must be used in order to obtain correct values of friction coefficients (CoF). If footwear is tested, then a floor is used as the reference material for comparison (either steel or a ceramic tile). If floorings are tested, the reference material shall be footwear or an elastomeric material test-piece, as stated in the test method used.
But in the ULTRAGRIP project, a big effort has been made to define common reference materials that can be used by all the methods aforementioned. So, it has been defined different combinations of floors and shoes / sliders that generate friction values around the biomechanical critical values (approximately 0,30 CoF), and that show high wear resistance, in order to avoid changes in the results due to progressive wear. Measurements of friction coefficients using these common reference materials have permitted to compare the slipping methods and establish the existing correlations between them.
For example, the footwear sample for testing according to different slipping test methods studied in the project (ramp method, footwear method, biomechanical method, etc.) has been unified. It consists of a size 42 pair of shoes with removable sole, which permit to change the material and the design of the sole without changing the rest of the footwear.
Molecular interactions between sole-contaminant-floor
In this study it has been determined the correlation between surface energy (E) and CoF, both in footwear and floorings. For this, E and CoF have been determined in commercial and customised solings and floorings.
E is obtained from the values of the contact angles (?) measured using different reference liquids (at least two with different polar natures) and applying diverse equations. CoF is obtained according to footwear test method EN-ISO 13287:
- CoF in solings: solings (76 x 25 x 7 mm) slipping over Eurotile 2 flooring with angle of 7o,
- CoF in floorings: reference rubber Slider 96 (76 x 25 x 7mm) slipping over floorings with angle of 7 o.
A trend between E and CoF has been observed: The higher the wettability, the higher surface energy, the higher the CoF. But an important increase in E is needed to obtain a significant increase in CoF.
Evaluation of footwear friction performance durability and maintenance
The requirements that are currently in force for footwear refer exclusively to professional footwear, according to standards EN ISO 20345-6-7. However, no reference is made to preserving the slipping performance of footwear throughout its useful life. For this reason, the change in the friction coefficient of footwear (CoF) caused by the wear degree of the soles at two levels: soles from conducted wear trials of footwear, and soles from laboratory wear treatments, has been analysed.
Different wear trials were conducted in order to evaluate the changes in CoF because of the wear, according to the methodology of EN-ISO 13287:2007. Final users of these trials have been:
Sports wear trials:
- handball club 'Elche',
- handball club 'Elda Prestigio',
- futsal club 'El Pozo Murcia',
- other futsal users,
- seven-a-side football users,
- running users.
Professional wear trials:
- the Vinalop? Area Fire partment (Alicante),
- Master Chocolatier Paco Torreblanca.
Some of these wear trials have been also used for project dissemination by means of disclosing information in the media about the collabouration between the ULTRAGRIP project and different groups of renowned users.
Footwear wear trials results and laboratory wear results (using the developed wear technology) indicate that it is necessary that the slipping testing methodology considers a more aggressive laboratory wear treatment of the sole as a preparation method of the sample before testing. That is why the ULTRAGRIP proposal is testing the footwear sample before (as established in the current standard) and after the wear treatment developed in the project.
Evaluation of floorings friction performance durability and maintenance
In the case of the flooring sector, the regulation in force, for example in Spain, derived from the publication of the technical building code (DB-SUA), not only establishes some friction requirements for floorings for public access sites but also requires the maintenance of their performance throughout their whole useful life.
In situ wet pendulum studies on the changes of slip resistance due to wear at indoor and outdoor actual conditions have been developed in different places: In the town of Castellon at University Jaume I and Santa Clara Square; In Lujbliana at ZAG facilities, kofja Loka bridge and St. Anton church. The changes on the surface due to the freezing action (in the presence of salts which are commonly used to reduce the occurrence of ice) have been studied too. The results confirm that the slip resistance performance of most flooring materials decreases during their first year in service, especially in outdoor conditions.
These studies have allowed the validation of the new technology for simulation of wear on floorings, which has been used to analyse the durability of different types of floors. The results show that the changes on friction depend on the nature of the material and its surface design. So the ULTRAGRIP project is testing friction on abraded flooring surfaces when the floorings are expected to be used in outdoor areas or areas with direct outdoor access.
Friction coefficient mathematical predictive models
Four different mathematical predictive models have been developed, to predict the friction behaviour in each one of the following four products:
- footwear,
- indoor pavements,
- outdoor pavements,
- industrial pavements.
The possible input parameters (P) of the models have been a priori defined based on Inescop and ITC's wide experience and the development of specific experiment designs. Some of these parameters could be qualitative and other quantitative, which could be part of the polynomial-type mathematical function for CoF prediction.
CoF= f(P).
The models have been created in an attempt for them to be, in addition to being predictive, explanatory as well. In other words, the has parameters which must mandatorily be included in the models and their sign have been identified; all this based on the studies carried out, so that the final mathematical functions could make physical sense and explain the friction phenomenon predicted by the model.
Each model comprises different polynomials (LM), in such a way that the CoF is estimated using one or another depending on the input parameter values of the model. In other words, each polynomial takes part when certain conditions of the input parameters occur.
These models are the basis of the CoF prediction software developed in the project.
White paper on new standard for testing footwear in different environments / conditions
The European standardised method for measuring CoF in footwear is described in the standard EN-ISO 13287:2007. Only professional footwear has to fulfil the normative requisites.
In this method, the footwear is placed on the reference testing surface (the floor) and a normal force (v) is applied. Then the surface slides below the shoe in a horizontal direction at a constant speed. The vertical load as well as the force required to move the floor are measured and this way the dynamic friction coefficients are then calculated and the footwear slipping response can be graded according to their grip.
This method is robust, repeatable and in general, according to experience following years of usage, a valid method of testing slipping resistance. This means that, generally speaking, footwear passing these tests does not show slipping problems and very often footwear not reaching the prescribed minimal values, do have slipping problems in real use. However based on the experiences gained during the ULTRAGRIP project, some improvements have been proposed.
First of all, it should be pointed out, that the existing method is valid when the main task to be performed is walking and possibly even heel to toe running. So this standard is fine to evaluate casual and safety footwear. However, when it comes to sport shoes, the friction requirements tested with the existing method do not match with those required for the sport shoes to perform appropriately. Therefore improvements are proposed in two different sections: One for casual and safety footwear and another for sports shoes.
The ULTRAGRIP improvements proposed to the current standard which measures the footwear friction, were presented to the standardisation committees (23 May 2012 at the CEN-TC161-WG3 meeting, held at INESCOP-Elda-Spain).
White paper on new standard for testing FLOORINGS in different environments / conditions
The results of the experimental work confirm that it is not possible to predict the friction using the results coming from a different test conditions than the actual ones. So the ULTRAGRIP project proposes to use a new approach for application based standards which jointly consider the influence of the expected footwear, contaminant and floorings.
ULTRAGRIP results were presented to the ISO TC 189 standardisation committee 'Ceramic tile' on 15 November 2011 at the meeting which took place in London.
Proposal of new application based standards
1) Floors for indoor areas without direct outdoor access
Test method: pendulum / flat rubber IRHD 57 slider
Contaminant: water
Reference floors: Ceramic1, Eurotile-1 and Ceramic2
Wear simulation conditioning: not applicable.
2) Floors for indoor areas with direct outdoor access
Test method: pendulum / flat rubber IRHD 57 slider
Contaminant: water
Reference floors: Ceramic1, Eurotile-1 and Ceramic2
Wear simulation conditioning: 100 cycles.
3) Floors for outdoor areas
Test method: pendulum/flat rubber IRHD 57 slider
Contaminant: water
Reference floors: Ceramic1, Eurotile-1 and Ceramic2
Wear simulation conditioning: accumulated cycles till stabilisation.
4) Floors for working areas
Test method: Ramp & UVEX safety footwear
Contaminant: oil
Reference floors: Ceramic StI, Ceramic StII and Ceramic StIII
Wear simulation conditioning: when requested, accumulated cycles till stabilization.
5) Floors for wet barefoot areas
Test method: ramp barefoot
Contaminant: water + 0,5% sodium lauryl sulphate
Reference floors: Ceramic3, Eurotile-1 and Ceramic4
Wear simulation conditioning: not applicable.
Potential impact:
The project has contributed to enhance SMEs' competitive strength by supporting the creation of design tools for the improvement of the slip behaviour of products in footwear and pavement sectors. The market need for innovative anti-slip products for a variety of applications (shopping malls, hospitals, sport facilities and other public places) which represents a large market potential that is typically suitable for small and medium enterprises, where the production flexibility of the SME companies is of a major competitive advantage.
The legislation in force in the European Union clearly establishes the safety requirements of protective footwear, one of them being the footwear's slip resistance property. The interest to increase the anti-slip properties of professional footwear is now expanding more and more to other types of footwear, such as sport shoes, leisure, etc., although there is no legislation forcing the fulfilment of this feature in these kinds of footwear. On the other hand, floorings must achieve the CE marking requirements according to the EU Construction Products Directive (89/106/EEC), which also include the declaration of slip resistance. The common interest in both sectors is avoiding or reducing injuries caused by slipping (around 44 % of accidents in the workplace are caused by slipping). This highlights that the existing legislation regarding the slip resistance properties of footwear and floorings is inadequate in certain cases.
This project proposal deals with reduction of slipping risks. According to ESENER (Enterprise survey on new and emerging risks that examines how health and safety is managed in practice in European workplaces), the results to the following question indicate the importance of safety equipment in order to avoid accidents: 'For each of the following issues, please tell me whether it is of major concern, some concern or no concern at all in your establishment. Accidents'.
Apart from the importance that firms give to this issue, citizens also demand for better health and security at their workplace (results from Pan-European opinion poll on occupational safety and health-2012).
For all the above, the participant SMEs, which are footwear and flooring manufacturers, need to differentiate their products from those imported from low wage countries by means of the addition of attributes that such imported products do not incorporate. Among these attributes, the slip resistance plays an essential role in both sectors.
Currently, sole manufacturers design their models to be anti-slip using basic design criteria, often relying on their intuition and previous experience. The problem resides in the lack of design tools that can be used in the conception of footwear, which would make prototyping much cheaper, quicker and more effective in creating an answer to the friction that the shoe would be subjected to when used.
The availability of these tools has generated an impact on a reduction in the design-production time of the footwear as well as a reduction in costs, as unnecessary costs could be avoided, such as those derived from amendments to sole moulds, materials used for the production of prototypes, slip resistance validation tests following prototyping, etc. On the other hand, SME flooring manufactures has to carry out a series of different slip resistance tests to comply with the various national requirements, the amount being dependent on the number of countries they export and their respective regulations. The successful result of the project has also been highly beneficial for flooring manufacturers as a cost reduction and a way to speed the time to the market of his innovative products.
With the project, it is possible to change the prototype sole production process. This entails:
- fabrication of one mould with the moulding cavity having the prototype shape,
- moulding of some samples of soles with the final sole material selected,
- slip resistance testing of the sole samples according to current standards.
If friction coefficient does not pass the requirements, then changes must be introduced in the 2D - 3D design of the sole, and the prototyping process must start again. Usually, this validation process is repeated two or three times, making double or triple the prototyping costs, and increasing the process time.
Impact due to internal use of ULTRAGRIP tools on participating footwear SMEs (KELME, Ruizalejos and Basepro) is related with previous data.
- Reduction in time for prototyping:
Manufacturers design their models to be anti-slipping using basic design criteria, often relying on their intuition and previous experience. But, with the new design tools they will go directly to the optimum prototype, avoiding repetitions (12 days instead of 55 days).
- Reduction in prototyping costs:
The reduction in time for prototyping will directly imply a reduction in the cost of this operation. Current situation is that manufacturers need to modify the first sole prototype including pattern changes because the friction behaviour is not the needed one. Then changes must be introduced in the 2D - 3D design of the sole, and the prototyping process must start again. Usually, this validation process is repeated two or three times, making double or triple the prototyping costs. This will mean an indicator of 33 % or 67 %. More drastic scenario has been considered (67 %).
- Reduction in production costs:
The reduction in the costs of prototyping will directly imply a reduction in final production costs, always with lower impact than the first two indicators explained above.
- Product quality:
The design tools developed will imply a final increase in anti-slipping behaviour of products.
- Overall time-to-market:
The reduction in designing-prototyping times will directly imply a reduction in time-to-market (57 days onstead of 100 days).
- Market share:
An increase in quality of the products will directly imply a higher level of satisfaction for consumers.
- New skills:
Traditional designing-prototyping operation will be replaced with new design tools based on knowledge, so they will imply a better qualification and a knock-on effect over young people and designers.
Vender and Exagres, as polymeric flooring producers, will have similar impact than those obtained by footwear producers SME partners: they will reduce costs and they will find a way to speed the time to the market of their innovative products. Nevertheless, VERN?S and Marmor will obtain lower impact due to the type of article they manufacture (natural stones, etc.) in which design is not as important as could be in other kind of products as soles, polymeric pavements, etc.
Impact on SMEs also will come from results commercialisation. The project results can be classified in three different categories: technology, tools and knowledge (see http://showroom.ultragrip.eu for details). Project results that can give direct revenues to the SMEs partners through their external commercialisation are those of 'technology' and 'tools' types:
Res 3. Technology for high-speed image acquisition in the sole-contaminant-flooring interface. Estimated selling price EUR 20 000/unit.
Res 4. Image acquisition and analysis software for the high-speed recording technology. Estimate prices EUR 4000.
Res 7. Novel real-scale wear simulation technology for footwear and floorings. Estimate price EUR 15 000/unit.
Res 8. Slip behaviour predicting software for the different combinations of floorings and footwear, as a design tool for both sectors and for the precise definition of the requirement level that ensures user's safety. Estimated price EUR 3000/unit.
Res. 3 and Res.4 are only addressed to footwear sector, as the high speed technology uses a transparent crystal as pavement; Res. 7 and Res. 8 are addressed to both sector manufacturers.
According to previous figures, a first hypothesis on the total economic benefit for each individual SME partner is based on the cost of the project to implement the planned solutions, the current revenues of the companies and the forecast revenues due to internal use of project results and external commercialisation of them. The forecast revenues are calculated for the first three years after the end of the project and they are based on 5 %, 10 % and 15 % of current revenues respectively.
ULTRAGRIP project provides also other advantages like:
- development of new shoe models with better grip performance,
- development of new pavement with better grip performance,
- increasing in the number of orders, due to a higher level of satisfaction for consumers and shorter time to market,
- better flexibility of the production, since the developed design tools do not limit the style,
- better differentiation of European products from those imported from low wage countries by means of the addition of slip resistance attribute that such imported products do not incorporate,
- possibility to maintain the production in the origin country, without the need of delocalization,
- criteria harmonisation in footwear and pavement sectors as regards the assessment of slip resistance.
Project website: http://www.ultragrip.eu
Project FaceBook profile: http://www.facebook.com/pages/ULTRAGRIP/140415302728444
Showroom of project results: http://showroom.ultragrip.eu
Main project contacts
Dr Cristina Llobell Andres (Project coordinator)
RTD Manager
Inescop - Instituto Technolygico del Calzado y Conexas
Tel: +34-965-395213
Fax: +34-965-381045
E-mail: cllobelll@inescop.es
ULTRAGRIP consortium
1. INESCOP (Spain)- Coordinator
Contact person: Cristina LLobell
Email: cllobelll@inescop.es
2. KELME - New Millenium Sports, S.L. (Spain)
Contact persons: Luca Gios, Luis Maestre
Email: luca@kelme.es; lmaestre@kelme.es
3. Cauchos Ruiz-Alejos, S.A. (Spain)
Contact person: Ismael Ru?z-Alejos
Email: ismael@cauchosruiz-alejos.com
4. Vernis, S.A. (Spain)
Contact persons: Anabel Castell?, M. Carmen Segura
Email: acastello@vernis.es; mcsegura@vernis.es
5. Basepro - Base Protection SRL (Italy)
Contact persons: Cataldo de Luca, Mauro Dimolfetta
Email: rd@basepro.it; m.dimolfetta@basepro.it
6. Marmor - Marmor Hotavlje Druzba za Obdelavokamna dd Hotavlje (Slovenia)
Contact person: Zdenko Mrdja
Email: zdenko.mrdja@m-h.si
7. Vender - Vender Proizvodnja Trgovina Inzeniring in Zastopstvo DOO (Slovenia)
Contact person: Dusan Verdel
Email: info@vender.si
8. ITC - Asociaci?n de Investigaci?n de las industrias ceramicas AICE (Spain)
Contact person: Gonzalo Silva
Email: gonzalo.silva@itc.uji.es
9.ZAG - Zavod za Gradbenistvo Slovenije (Slovenia)
Contact person: Vilma Ducman
Email: vilma.ducman@zag.si
10. Exagres, S.A. (Spain)
Contact persons: Crist?bal Badenes, Sara Rubert
Email: cbadenes@versatile.es; srubert@versatile.es