Abstract
A hypothesis was presented concerning the effect of the axial residual stress at the first thread root of a bolt on its fatigue strength. However, this has not yet been verified since the residual stress which may exist locally around the thread root cannot be measured or estimated with sufficient accuracy. This study aims to quantify the effect of the residual stress on the fatigue strength. For this purpose, residual stress at the root of groove-rolled specimens were measured by X-ray method, and it was found that the maximum compressive residual stress was generated at the inner layer about 0.5 mm from the surface. However, such a distribution could not be simulated by FEM analysis with simple plane strain model. In this report, FEM analysis is performed for three levels of coefficient of shear friction (0.12, 0.25 and 0.5) and two types of loading process with continuous or 11 steps. The results show that the residual stress distribution is affected by these parameters, and can be simulated by using f = 0.12 or 0.25 and discrete loading process.
