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韧性材料的多向静应力状态,有最大正应力、最大剪应力等强度理论,作为强度设计计算的判断准则,而在多向动应力状态下的强度理论是什么呢?至今尚未有确切的定论。本文根据韧性材料的疲劳破坏机理,提出了在多向动应力状态下,材料的某一截面上沿某个方向首先开始破坏,主要是由于其剪应力时间历程的作用最不利所引起的,并同时考虑了该截面上的正应力时间历程的影响,建立了韧性材料在多向动应力状态下疲劳破坏截面的位置及其寿命的计算公式,作为动强度设计计算的判断准则,简称之为动强度理论。
The multi-directional static stress state of ductile materials, such as the maximum normal stress, the maximum shear stress, etc., is used as the criterion for the strength design calculation. What is the strength theory in the multi-axial dynamic stress state? There is no definite conclusion yet. . Based on the fatigue failure mechanism of ductile materials, this paper proposes that in a multi-directional dynamic stress state, the material begins to fail in a certain direction along a certain direction, mainly due to the most unfavorable effect of its shear stress history. At the same time, considering the influence of the time history of positive stress on the cross section, the formula for calculating the position and life of the fatigue failure cross section of a ductile material under multi-directional dynamic stress is established, which is used as a criterion for dynamic strength design calculation. Strength theory.