コイルばねの応力・変形特性に及ぼす素線の異方性の影響

抄録

The present paper has investigated the effects of wire anisotropy on the stress distributions in tensile coil springs and on their deformation behavior obtained by the finite element analyses (FEM). The types of anisotropy investigated in this paper were cylindrical and general anisotropy. The former simulates wire drawing and the latter considers the mutual influence effects of shear stresses (strains) and normal strains (stresses). The calculated deflections of tension coil springs and their spring constant agreed well with the values calculated by their well-known practical formulas for isotropic and cylindrically anisotropic springs. The values of normal stress σ_z and shear stress τ _θz on the wire cross section of these springs varied from a negative value on the outer periphery of the coil to a positive value on the inner periphery on the cross section of the isotropic springs. The distribution of the shear stress τ _θz agreed well with that of the shear stress τ _θz modified by the Wahl correction factor. In the generally anisotropic tension coil springs, however, the deflection δ showed abrupt increase, and thus the spring constant was markedly decreased for C ₁₄ ＞ 40 GPa. The distributions of σ_z and τ _θz were completely different from those in the isotropic and the cylindrically anisotropic springs. The absolute values of the normal stress σ_z in the generally anisotropic springs were more than four times higher than those in the isotropic and the cylindrically anisotropic springs. The shear stress τ _θz distribution did not agree with Wahl’s modified stress distribution. The higher absolute value of σ_z brought about sudden increase of deflection of the generally anisotropic springs for C ₁₄ ＞ 40 GPa.