灰铸铁圆轴纯扭转破坏拉应力与拉伸强度比实验和强度理论计算的矛盾

In this paper, using the traditional theory for torsion stress analysis of circular shaft, the uniaxial tensile, uniaxial compressive, pure torsional experimental data of five groups of gray cast iron are researched from aspects of experiment and strength theory respectively. It is obtained that the ratio (k) between the experimental value of the maximum tensile strength and the uniaxial tensile strength of gray cast iron when fracture is between 1.362 and 1.530; the maximum tensile strength of gray cast iron when fracture is more than 1.3 times larger than the relative uniaxial tensile stress. According to the four strength theory for gray cast iron, Mohr-Coulomb criterion, Josefson-Hjelm criterion, Altenbach criterion, limiting strain energy strength theory, the value of k of gray cast iron when fracture is between 0.778 and 1.176. It is discovered there exist a contradiction between the experimental value of k of gray cast iron and the relative calculation results according to strength theories. The average calculation error of five groups of experimental data of gray cast gray under pure torsion is 40%-90%, which indicates the principal stress according to the traditional theory for torsion stress analysis of circular shaft overestimated the fracture strength of gray cast iron under pure torsion. The traditional theory for torsion stress analysis of circular shaft may not be applicable for gray cast iron. This problem is worth further research.