金属轴类零件当量弯矩中折算系数的取值问题

STUDY ON THE CONVERSION COEFFICIENT IN THE EQUIVALENT MOMENT FOR METAL SHAFTS

理论研究和实验证明 ,按统一多重屈服面理论 ,可采用Tresca准则 (第三强度理论 )对金属轴类零件的疲劳强度进行简化分析计算。当量弯矩强度条件作为疲劳强度条件的一种简化近似描述 ,反映在两个强度条件的计算公式中 (几何描述均为椭圆 ) ,两个椭圆的半轴长度应相近。本文对按当量弯矩计算与按疲劳强度计算两个强度条件的分析、比较 ,得出了两个强度条件等效时应满足的条件 ,由此得到的折算系数α值可使当量弯矩强度条件更接近于精确值。这样不仅可使计算简化 ,而且可得到既经济又安全的效果。

It has been proved by theoretical researches and experiments that in accordance with the theory of the unified multi layer yield plane, Tresca Criterion, i.e., the Third Strength Theory, can be used to do the simplified analysis and calculation of the fatigue strength for the metal shafts. The equivalent moment strength condition, as a simplified approximate description of the fatigue strength condition, is reflected in the two calculation formulae, their geometrical descriptions being ellipses, and the lengthes of half axes of these two ellipses must be proximate. In this paper, strength conditions derived by equivalent moment calculation and fatigue strength calculation are both analysed and compared, thereby giving the equivalent conditions which must be satisfied at the same time by these two strength conditions. And in so doing,the values of α , the conversion coefficients, can be made approaching to the exact values of the equivalent moment condition. Therefore not only the calculation can be made simplified but also the effect of economy and safety can be achieved.