鋼結構端板連接用M24高強度螺栓疲勞裂紋擴展數值分析
首發時間:2023-10-19
摘要:為探究高強度螺栓疲勞裂紋擴展機理,基于30個M24高強度螺栓常幅疲勞試驗數據,對典型螺栓斷口進行宏、微觀分析,采用ABAQUS有限元軟件對含預制裂紋的高強度螺栓進行數值模擬,重點探討了螺栓在不同長度預制裂紋下的應力分布情況及預制裂紋的幾何特征對應力強度因子(stress intensity factor, SIF)、裂紋擴展方向的影響。結果表明:在相同應力比下,疲勞擴展區徑向長度隨著平均特征應力幅的增加而降低,降低幅度為21.8%和5.7%,且瞬斷區韌窩深度隨著疲勞輝紋間隙的增大而加深;預制裂紋幾何特征對螺栓應力分布影響明顯,試件疲勞斷裂SIF與裂紋預制長度、裂紋徑向/環向之比呈正相關關系,但與預制裂紋初始角度無明顯關系。此外,還建立了基于試件應力變化率判斷疲勞裂紋長度變化率的預測公式,指出了高強度螺栓疲勞斷裂過程的位移變化率在n/N>0.75時有明顯改變。
關鍵詞: 高強度螺栓 疲勞破壞 應力強度因子 裂紋擴展角 擴展有限元法
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Numerical analysis of fatigue crack propagation of M24 high-strength bolts for end plate connection of steel structure
Abstract:In order to explore the fatigue crack propagation mechanism of high-strength bolts, based on the constant amplitude fatigue test data of 30 M24 high-strength bolts, the macro and micro analysis of typical bolt fractures were carried out. The ABAQUS finite element software was used to simulate the high-strength bolts with prefabricated cracks. The stress distribution of bolts under different lengths of prefabricated cracks and the influence of geometric characteristics of prefabricated cracks on stress intensity factor and crack propagation direction were discussed. The results show that under the same stress ratio, the radial length of the fatigue propagation zone decreases by 21.8% and 5.7% with the increase of the average characteristic stress amplitude, and the dimple depth of the instantaneous fracture zone increases with the increase of the fatigue striation gap. The geometric characteristics of the prefabricated cracks have obvious influence on the stress distribution of bolts. The fatigue fracture stress intensity factor of specimens is positively correlated with the prefabricated length of cracks and the ratio of radial / circumferential direction of cracks, but has no obvious dependence on the initial angle of prefabricated cracks. In addition, a prediction formula for judging the change rate of fatigue crack length is established based on the stress change rate of the specimen which indicates that the displacement change rate of the high-strength bolt fatigue fracture process changes significantly when n/N > 0.75.
Keywords: high-strength bolts fatigue failure stress intensity factor (SIF) crack propagation angle extended finite element method (XFEM)
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