刘光连^1，*， 黄明辉^1，， 刘振^2，， 李显方^3，

（  1、中南大学机电工程学院；       2、香港城市大学制造工程与工程管理系；       3、中南大学土木建筑学院；  ）

摘要： 文献[1]应用圆轴扭转应力分析传统理论，发现了灰铸铁圆轴纯扭转破坏时最大拉应力与拉伸强度比的实验值和强度理论计算值之间存在较大的矛盾，四个强度理论计算五组灰铸铁纯扭转强度实验数据的组平均误差是40%-90%的正误差。本文对这一矛盾的原因进行了分析，通过对灰铸铁圆轴纯扭转试件表面断裂线螺旋角的测量研究，发现灰铸铁圆轴纯扭转试件表面断裂线螺旋角约为32 ，与轴线的夹角约为58 ，两者都不是传统的45 。应用平面应力状态最大主应力所在截面方位角计算公式，得到灰铸铁圆轴纯扭转破坏时存在一个与轴横截面上扭转剪应力大小相等、方向平行的附加压应力，并提出灰铸铁圆轴扭转剪应力诱导正应力假设，揭示了灰铸铁圆轴纯扭转破坏时最大拉应力与拉伸强度比实验值和强度理论计算值之间存在矛盾的原因。根据扭转剪应力诱导正应力假设，四个强度理论计算灰铸铁圆轴纯扭转破坏时的相对误差都减少了30%以上，极限应变能强度理论能用于灰铸铁圆轴纯扭转强度计算，Mohr-Coulomb准则、Josefson-Hjelm准则、Altenbach等屈服准则不适合灰铸铁圆轴扭转强度计算。扭转剪应力诱导正应力假设动态应变测量的实验验证、及其在塑性材料轴中是否适用还值得深入研究。
关键词： 灰铸铁圆轴；扭转剪应力诱导正应力假设；实验；强度理论

LIU Guanglian^1,*， HUANG Minghui^2,， LIU Zhen^3,， LI Xianfang^4,

（  1、School of Mechanical and Electrical Engineering, Central South University；       2、School of Mechanical and Electrical Engineering, Central South University ；       3、Department of Manufacturing Engineering & Engineering Management, City University of Hong Kong；       4、School of Civil Engineering and Architecture, Central South University ；  ）

Abstract： In Reference [1], using the traditional theory for torsion stress analysis of circular shaft, it was discovered that there exist great contradiction between the experiment and strength theory calculation of the ratio between the maximum fracture tensile stress and tensile strength of gray cast iron circular shaft under pure torsion. The average calculation error of five groups of strength experimental data of gray cast gray under pure torsion is 40%-90%. In this paper, the cause of this contradiction is analyzed. Through measuring the helical angle of the fracture line on the surface of torsion gray cast iron circular shaft specimen, it is discovered the helical angle of the surface fracture line is about 32 , and its intersection angle with the axis is about 58 ; both of them are not of the traditional value 45 . Using the formula of azimuth angle on the cross section where the plane stress state maximum principal stress lies, it is obtained that when the gray cast iron circular shaft is under fracture; there exists an additional compressive stress which is equal to and parallel to the cross-section torsion shear stress of the shaft. An assumption that the torsion shear stress of the gray cast iron circular shaft induces normal stress is proposed. The proposed assumption reveals the cause of the contradiction between the experiment and strength theory calculation of the ratio between the maximum fracture tensile stress and tensile strength of gray cast iron circular shaft under pure torsion. Based on the proposed assumption, the calculated relative error of gray cast iron circular shaft under pure torsion fracture according to four strength theories all reduces more than 30%, the limiting strain energy strength theory is applicable for pure torsion strength calculation of gray cast iron circular shaft, while the Mohr-Coulomb criterion, Josefson-Hjelm criterion, Altenbach criterion is not applicable. The dynamic strain experiment validation of the proposed assumption and whether the proposed assumption is applicable for plastic shaft are still worth further research.

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