The structural integrity of many industrial structures is generally ensured by preventing the initiation of cracks. However, in the field of pipeline industries, the problem of fast crack propagation and crack arrest is of highest importance and has led to extensive studies.
To study dynamic ductile crack propagation over long distances under conditions as close as possible to in-service conditions, OCAS studies dynamic ductile crack propagation in full-thickness plates at high crack speeds over a length of 180 mm using an experimental dynamic tear test (DTT) set-up. This dynamic tear testing approach is used to address challenges such as specimen size limitation and inverse fracture propagation associated to Charpy V-notch (CVN) and drop weight tear test (DWTT) experiments.
The OCAS dynamic tear testing machine capacity is large enough to test full thickness plates. Once the force reaches a critical level, the crack starts to propagate and the specimen is fractured within milliseconds.
This dynamic tear testing equipment was used in the framework of the European FP7 funded research programme CO2QUEST.
The fracture surface of dynamic tear testing shows a ductile fracture aspect. From this fracture surface it is possible to reproduce real scale slant fracture associated to steel pipeline failure phenomenon.
“This custom-built machine allows us to study the crack propagation behaviour of materials on full thickness samples in tensile mode. Standard tests and equipment are often limited to bending mode and therefore do not fully reflect in-service conditions,”
Dennis van Hoecke, Senior team leader Applications & Solutions department, OCAS
“OCAS’s dynamic tear tester employs a mechanical spring which stiffness can be tuned to the test material. The machine and sample are instrumented to fully capture the material’s resistance to crack propagation, ”
Koen Bracke, Technician Advanced Mechanical Characterisation, OCAS