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一、用双判据法对提升机主轴表面纹裂的分析与计算 由线弹性断裂力学理论可知,只有当结构或试样的裂纹尺寸大到一定的程度,或当破坏载荷低于材料毁损的极限载荷一半时,则裂纹周围的塑性区才可能控制在较小的范围内,此时按线弹性断裂力学来处理是能够满足工程所要求的精度(可使误差<7％),即只有在这样情况下由线弹性断裂力学判据所得出的最大容许载荷或最大的缺陷尺寸才是可靠的。假若构件上的缺陷尺寸较小,特别是应力集中处的裂纹,则其破坏载荷便有可能超过材料毁损极限载荷的一半。此时裂纹周围的塑性区便增加到相当的分量而不再满足小范围屈服条件。此情形下即使采用小范围塑性区进行修正也是不恰当的,因为这
First, the double criterion method of lifting the spindle surface crack analysis and calculation of linear elastic fracture mechanics theory shows that only when the structure or specimen crack size to a certain extent, or when the damage load is lower than the material damage When the ultimate load is half, the plastic zone around the crack can be controlled within a small range. At this time, the linear elastic fracture mechanics is able to meet the engineering requirements (error <7%), that is, In this case, the maximum allowable load or the maximum defect size obtained from the linear elastic fracture mechanics criterion is reliable. If the defect size of the component is small, especially the cracks in the stress concentration place, the breaking load may exceed half of the material damage ultimate load. At this point the plastic zone around the crack increases to a considerable extent and no longer satisfies the small-scale yield conditions. Even in this case, it is not appropriate to correct with a small area of plastic because of this