圧縮及び引張コイルばね中の表面き裂の応力拡大係数の FEM 解析

抄録

In this study, 3D finite element analyses have been made on the stress intensity factors for semi-elliptic surface cracks on the inner wire surface of compression coil springs in order to investigate the effects of spring parameters on the correction factors F_i (i =I, II, and III) for the three modes of the stress intensity factors. The parameters selected for the present analyses are crack inclination angle, or the inclination angle of the cracks to the equator of the wire, θ and crack aspect ratio a/c where a is crack depth and c half crack surface length. The results are compared and discussed with those obtained by the present authors’ previous work for tension coil springs. For crack inclination angle θ, F _II was dominant over the other two factors in compression coil springs whereas F _I in tension coil springs. For crack aspect ratio a/c, F _I was dominant and the F _I－a/c relationships showed a similar tendency for eccentric angle φ in the both types of coil springs. Namely, the relationships were represented by quadratic curves of a/c projected upward and the F _I value reached its maxima for a/c =2.0 near wire surface at φ≒0° and 180°. The F _I values, however, were monotonically decreased for increasing a/c value at φ=45°, 90° and 135°.