Volume 16, Issue 2 (March 1988)
Fatigue Life Prediction in Flexural Bending of Hollow Cross-Sectional Bars from Axial Fatigue Information
Bending fatigue results in the low cyclic life range often differ from those of axial fatigue due to the plastic flow, which alters the linear stress-strain relation normally used to determine the nominal stresses. An approach was presented and an equation derived in earlier work to take into account the plastic flow in calculating nominal bending stress based on actual surface stress for solid rectangular and circular cross-sectional bars. The flexural bending fatigue life prediction of bars with hollow cross sections is addressed in this paper. An equation is derived for calculating the nominal bending stress versus life curve for hollow cross sections that depends directly on the functions derived for the solid section of the same geometry, and k, the ratio of inner to outer dimensions. The nominal bending stress versus life curves are shown for the case of hollow circular sections for six typical materials for various k values.