Stopping dangerous cracks in their tracks
Critical transport structures such as oil tankers carried on road and rail systems, or at sea, are subject to corrosion and fatigue. The resulting failures of such structures cause significant negative impact on the environment, economics and even human lives. Conventional inspection and maintenance are typically conducted on a pre-defined schedule and require removing the vehicle from service. Such procedures are limited by their inability to detect potential failures early and by the financial impact of lost service time. Scientists initiated the EU-funded project 'Cost effective corrosion and fatigue monitoring for transport products' (CORFAT) to develop non-destructive testing (NDT) for in-service components based on acoustic emission testing (AT). AT uses piezoelectric sensors mounted at the surface of the structure to detect sound waves formed as a release of energy from a material under stress. AT differs from other NDT techniques in that no external energy is supplied to the tested object and mainly dynamic events (active corrosion, crack propagation) are recorded. For further evaluation of defects found by AT researchers developed procedures for follow-up NDT using other conventional measures. Experiments enabled the investigation and characterisation of active corrosion and fatigue cracking under various conditions during acoustic emission (AE) monitoring. Application of filtering, including pattern recognition, made it possible to distinguish between AE signals related to corrosion and fatigue cracking and AE signals caused by background noise, especially by noises occurring during service. In addition, scientists used sensors mounted at the surface of the structure to demonstrate the ability to detect AE waves propagating directly in the metal, as well as AE waves partly propagating through liquid cargo. Verification tests on transport products enabled the optimisation of testing procedures, measuring equipment and analyses. CORFAT incorporated the careful consideration of hazardous conditions and relevant inspection rules and existing standards throughout the project. Hence, also AE equipment and procedures for application in hazardous areas have been developed. Scientists have delivered a new NDT technology based on Atthat includesinspection procedures, standardisation drafts containing system requirements, safety rules, follow-up NDT and related maintenance actions. This powerful in-service diagnostic technology could significantly reduce the likelihood of cargo transport component failure. Successful outcomes will have positive implications for environmental and human health and increase EU competitiveness in the industry. A variety of other sectors such as air transport and offshore wind generation could stand to benefit as well.
