Fatigue Test Result of the Pipe Support Welds Associated With Elastic-Plastic Analysis of Piping Systems for the Development of Fatigue Evaluation Methods

Abstract In this study, in order to apply the JSME design fatigue curve, which was developed mainly using small size specimen such as a standard round bar specimen, to the fatigue evaluation of elastic-plastic supports, fatigue tests were conducted focusing on the welds of piping support structures and the results were compared with existing design fatigue curve. In this fatigue tests, test specimens simulating pipe supports in actual plants were manufactured, and an actuator was used to apply repeated displacement with displacement control, and the number of cycles at which the weld broke and the strain value of the test specimen during the test were obtained. In addition, fatigue tests were conducted on test specimens with parameters, such as cross-section shape of member (square steel pipe, angle steel, channel steel), plate thickness, welding procedure, weld shape (penetration welding, fillet welding), and groove dimensions to confirm the effect of differences in these parameters on fatigue strength. The test results for the test case with the basic fracture pattern in which cracks initiated at the weld toe and propagated on the base metal side showed good agreement with the ASME BFC (Best Fit Curve) which is the best fit curve for relationship between strain amplitude and fatigue life of experimental data. Therefore, it was confirmed that the JSME design fatigue curve, which was formulated based on the ASME BFC, can be applied to fatigue evaluation in the case of the above basic fracture patterns. Based on the results of this test, we will consider specific fatigue evaluation methods in the future.