多过载作用下Q345R疲劳裂纹扩展行为研究

发布时间：2017-12-31 04:41

本文关键词：多过载作用下Q345R疲劳裂纹扩展行为研究　出处：《浙江工业大学》2016年硕士论文　论文类型：学位论文

【摘要】：工程构件在实际服役过程中常承受复杂的疲劳载荷,疲劳循环中时有过载情况。不同的过载形式对材料疲劳裂纹扩展的影响不尽相同,因此,研究多过载作用下疲劳裂纹扩展行为具有较大的学术价值和工程意义。本文针对Q345R材料,通过试验研究和数值模拟的方法,进行多过载作用下疲劳裂纹扩展行为的研究工作,具体研究内容和结论如下:(1)采用Q345R材料标准紧凑拉伸试样,在保持应力比、过载位置和过载比不变的情况下,在两个过载作用下,随着过载间距增加,迟滞效应先增加后减小;过载间距循环数是单一过载迟滞循环数的一半时,迟滞效应最明显。在多过载作用下,由于过载之间相互作用,过载间距比较小时,前一个过载的迟滞阶段会被下一个过载的影响区覆盖;增加过载间距,过载后出现迟滞阶段。(2)运用不含过载交互作用参数和含过载交互作用参数的修正Wheeler模型预测两个过载作用下的疲劳裂纹扩展行为,对比两个模型的预测结果,含过载交互作用参数模型预测结果与试验结果能更好的吻合。采用两个修正Wheeler模型预测多个过载作用下裂纹扩展行为,过载间距较小时,前两个或者多个过载与后一个过载均会产生交互作用,使得预测结果与试验结果存在差距。(3)运用基于累积损伤裂纹扩展模型预测两个过载作用下疲劳裂纹扩展行为,预测结果与试验结果吻合。接着采用该模型预测多个过载作用下疲劳裂纹扩展行为,并与含过载交互作用参数的修正Wheeler模型预测结果进行比较,结果显示:损伤模型比修正Wheeler模型能更好地预测多个过载作用下裂纹扩展行为,验证了该模型预测多过载作用下裂纹扩展行为的正确性。
[Abstract]:Engineering components often bear complex fatigue loads in the actual service process, and there is overload in the fatigue cycle. Different forms of overload have different effects on fatigue crack growth of materials, therefore. It is of great academic value and engineering significance to study the fatigue crack growth behavior under multiple overload. In this paper, the method of experimental study and numerical simulation is used to study Q345R material. The fatigue crack propagation behavior under multiple overload is studied. The concrete contents and conclusions are as follows: 1) the Q345R standard compact tensile specimen is used to maintain the stress ratio. Under the condition of constant overload position and overload ratio, the hysteresis effect increases first and then decreases with the increase of overload spacing. The hysteresis effect is the most obvious when the cycle number of overload spacing is half of that of single overload hysteresis cycle. Under the action of multiple overload, the overload spacing is smaller because of the interaction between overload and overload. The hysteresis phase of the previous overload will be covered by the influence area of the next overload; Increase overload spacing. The modified Wheeler model with no overload interaction parameters and overload interaction parameters is used to predict the fatigue crack growth behavior. Compared with the prediction results of the two models, the prediction results of the model with overload interaction parameters are in better agreement with the experimental results. Two modified Wheeler models are used to predict the crack growth behavior under multiple overload. When the overload spacing is small, the first two or more overloads interact with the latter. The results show that there is a gap between the predicted results and the experimental results. (3) based on the cumulative damage crack propagation model, the fatigue crack growth behavior under two overload loads is predicted. The prediction results are in agreement with the experimental results. Then the fatigue crack growth behavior under multiple overload is predicted by the model and compared with the modified Wheeler model with overload interaction parameters. The results show that the damage model is better than the modified Wheeler model in predicting the crack growth behavior under multiple overload, and the correctness of the model is verified.
【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG142.1

【相似文献】