1212 ねじ谷底の残留応力と疲労強度の関係 : 第1報,X線による転造丸溝の残留応力測定(ねじ及び締結・把持要素の特性,一般講演)

概要

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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 clarify the effect of the axial residual stress on the fatigue strength quantitatively by using newly developed technologies. As the first step, the residual stress at the root of groove-rolled specimen was measured by X-ray method with CCD positioning system, and two-dimensional FEM simulation for rolling process was also performed by using DEFORM with axisymmetric model. The experimental results show that the compressive residual stress of 700 MPa level exists at the root surface, and the maximum of 1200 MPa level is generated at the inner layer of about 0.5 mm from the surface. The residual stress distribution has good correspondence with Vickers hardness distribution measured. However, such a distribution cannot be simulated by FEM, which may be due to the difference of the contact conditions between actual rolling process and axially symmetric model.
2008-04-20