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工程结构和零件普遍而严重的失效形式是疲劳断裂,自十九世纪中叶德国人Wohler首次成功地解决了机车车轴的疲劳问题,近一百多年来,人们发现疲劳断裂总是起因于零件关键部位应力集中区(如槽底、孔边、台肩过渡截面等)的塑性形变。在交变载荷的反复作用下,由于这种不可逆的塑性形变的不断累积而形成微裂纹,宏观裂纹,最终导致零件的断裂。显然,一个零件的疲劳寿命取决于其关键薄弱部位的寿命,应对这些部位加以控制。在实验室采用简单的试样,模拟零件应力(或应变)集中区的应力-应变行为,测定其疲劳寿命。
The common and serious form of failure of engineering structures and parts is fatigue fracture. For the first time since the mid-19th century the German Wohler successfully solved the problem of locomotive axle fatigue. For more than a century, it has been found that fatigue fracture always results from the part-critical Part of the stress concentration area (such as the bottom groove, hole edge, shoulder transition section, etc.) of the plastic deformation. Under the repeated load of alternating load, due to the irreversible plastic deformation of the cumulative accumulation of micro-cracks, macroscopic cracks, eventually leading to the fracture of the parts. Obviously, the fatigue life of a part depends on the life of its key weak parts, which should be controlled. A simple sample was used in the laboratory to simulate the stress-strain behavior in the stress-strain (or strain) area of a part and determine its fatigue life.