ねじ谷底の残留応力とボルトの疲労強度の関係 : 第1報,転造丸溝試験片の残留応力について(機械要素,潤滑,工作,生産管理など)

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 groove rolling process was performed by using DEFORM with simple plane strain model. The experimental results show that the compressive residual stress of 700MPa level exists at the root surface, and the maximum residual stress of 1200MPa level is generated at the inner layer of about 0.5mm from the surface. Such a residual stress distribution can be simulated by FEM although it is affected by the coefficient of shear friction and the restraint conditions which may affect the circumferential material flow in groove rolling process.
2009-04-25