Displacement Based Failure Criterion Applicable to Finite Element Analysis Results for Wall-Thinned Pipes Under Pressure Load

In this work, a failure criterion applicable to large strain elastic-plastic Finite Element Analysis (EP FEA) results was proposed in order to predict the burst pressure of wall-thinned straight pipes. The key finding was that, though the pipe material was strain-hardening material, and though the pipe was locally wall-thinned, the outer surface radial displacement at the flaw center obtained from the EP FEA tended to diverge with the increase in pressure, even though the strain was very low compared to the true strain of fracture. This tendency was validated by the image processing displacement measurement results from the systematic burst tests of wall-thinned pipes. By comparing the EP-FEA results with the test results, the proposed criterion predicted the burst pressure within a maximum 10% difference. Advantage of the criterion is that it uses the true stress and strain relationship below the true tensile strength, and the ambiguous near fracture relationship is not necessary.