Fatigue life and experimental study of high-temperature bellows based on the improved Manson-Coffin equation

Abstract

Based on the high-temperature fatigue failure mechanism, this study proposes the use of the maximum shear strain range of crystal slip systems as the fatigue damage parameter and improves the Manson-Coffin equation accordingly. An Inconel-625 bellows model is constructed using the ANSYS Workbench platform for thermo-mechanical coupled analysis (temperature of 650 °C, displacement load of 7 mm, internal pressure of 0.3 MPa). Stress tests, including circumferential and axial stress, are conducted on the bellows to verify the accuracy of the finite element model. The six strain components in the model are extracted, and the improved Manson-Coffin equation is applied to calculate the fatigue life of the high-temperature bellows, resulting in a value of 12,318 cycles. Additionally, high-temperature fatigue life tests are performed on the Inconel-625 bellows under the conditions of 650 °C, 7 mm displacement load, and 0.3 MPa internal pressure, yielding a measured fatigue life of 9163 cycles. By comparing the experimental results of this study with those from relevant literature and plotting error band charts, it is demonstrated that the results obtained using the improved Manson-Coffin equation fall within a two-fold error band, validating the applicability of the improved Manson-Coffin equation for calculating the high-temperature fatigue life of bellows with different temperatures and models.