基于实验的缺口试件疲劳寿命评估方法比较研究
发布时间：2018-10-19 19:20
【摘要】：零件和结构的疲劳寿命预测对于工程实际的重要性是不言而喻的,无数的工程师和科学家依据各种疲劳失效实例和假设建立起了不同的疲劳寿命预测方法。本文以45#钢缺口试样为研究对象,结合疲劳实验对缺口试件的四种疲劳寿命评估方法的实用性与准确性进行对比研究,所作具体工作如下:根据相关国内外疲劳试验标准确定了光滑试样、U形缺口试样、半圆形缺口试样的尺寸,结合ABAQUS有限元分析结果,分别采用名义应力法、局部应力应变法、TCD算法中的点方法和线方法四种方法对两种缺口试件在四种应力级下疲劳寿命进行分析。在疲劳试验机上针对不同试样选取四种应力级进行疲劳试验,根据外推试验法对试验数据进行处理获取了不同应力级下的试验疲劳寿命,将不同理论疲劳寿命分析结果与疲劳试验寿命数据进行对比分析,研究发现传统TCD算法在本文研究条件下并不适用,遂采用1 KT?参数对标准TCD算法进行修正,得到了以下结论:1.求解缺口部件的理论应力集中系数可采用有限元方法代替查表法,更适合工程实践;2.相比于其他三种方法,名义应力法计算过程最为简单,但由于其只考虑了应力集中效应,预测结果偏于危险;3.局部应力应变法的低周疲劳预测结果较为保守,中高周疲劳预测精度相较于名义应力法有很大提高;4.修正TCD算法综合了线弹性断裂力学、应力集中效应并结合有限元分析软件获取的缺口根部附近应力场得到了更为接近试验寿命的结果,其中线方法相对于点方法在本文的研究条件下获取了更为准确的疲劳寿命预测结果.总结发现修正的TCD算法在本文的研究条件下,预测45#钢缺口试件的疲劳寿命比传统方法有更强的实用性与准确性,为工程疲劳寿命估算提供了一种新理论计算方法,有很大工程实际意义。
[Abstract]:The importance of predicting the fatigue life of parts and structures for engineering practice is self-evident. Numerous engineers and scientists have established different fatigue life prediction methods based on various fatigue failure examples and assumptions. In this paper, the practicability and accuracy of four fatigue life evaluation methods for notched specimens are compared with fatigue tests. The specific work is as follows: according to the fatigue test standards at home and abroad, the dimensions of smooth specimen, U-shaped notched specimen and semi-circular notched specimen are determined. Combined with the results of ABAQUS finite element analysis, nominal stress method is used respectively. The local stress-strain method, point method and line method in TCD algorithm are used to analyze the fatigue life of two notched specimens under four stress levels. Four kinds of stress levels were selected on the fatigue testing machine for different samples. According to the extrapolation test method, the test fatigue life of different stress levels was obtained by processing the test data. By comparing the fatigue life analysis results of different theories with the fatigue test life data, it is found that the traditional TCD algorithm is not applicable in this paper, and 1 KT? is adopted. Parameters of the standard TCD algorithm are modified, and the following conclusions are obtained: 1. The theoretical stress concentration factor of notched parts can be solved by using finite element method instead of table searching method, which is more suitable for engineering practice. 2. Compared with the other three methods, the notional stress method is the most simple one, but because it only takes into account the stress concentration effect, the predicted results are more dangerous. The low cycle fatigue prediction results of local stress-strain method are conservative, and the precision of mid-high cycle fatigue prediction is much higher than that of nominal stress method. The modified TCD algorithm synthesizes the linear elastic fracture mechanics, the stress concentration effect and the stress field near the notch root obtained by the finite element analysis software. The results are closer to the test life. Compared with the point method, the midline method is more accurate than the point method in predicting fatigue life. It is found that the modified TCD algorithm has better practicability and accuracy than the traditional method in predicting fatigue life of 4 steel notched specimens under the research conditions in this paper, which provides a new theoretical calculation method for engineering fatigue life estimation. It has great practical significance in engineering.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.15
[Abstract]:The importance of predicting the fatigue life of parts and structures for engineering practice is self-evident. Numerous engineers and scientists have established different fatigue life prediction methods based on various fatigue failure examples and assumptions. In this paper, the practicability and accuracy of four fatigue life evaluation methods for notched specimens are compared with fatigue tests. The specific work is as follows: according to the fatigue test standards at home and abroad, the dimensions of smooth specimen, U-shaped notched specimen and semi-circular notched specimen are determined. Combined with the results of ABAQUS finite element analysis, nominal stress method is used respectively. The local stress-strain method, point method and line method in TCD algorithm are used to analyze the fatigue life of two notched specimens under four stress levels. Four kinds of stress levels were selected on the fatigue testing machine for different samples. According to the extrapolation test method, the test fatigue life of different stress levels was obtained by processing the test data. By comparing the fatigue life analysis results of different theories with the fatigue test life data, it is found that the traditional TCD algorithm is not applicable in this paper, and 1 KT? is adopted. Parameters of the standard TCD algorithm are modified, and the following conclusions are obtained: 1. The theoretical stress concentration factor of notched parts can be solved by using finite element method instead of table searching method, which is more suitable for engineering practice. 2. Compared with the other three methods, the notional stress method is the most simple one, but because it only takes into account the stress concentration effect, the predicted results are more dangerous. The low cycle fatigue prediction results of local stress-strain method are conservative, and the precision of mid-high cycle fatigue prediction is much higher than that of nominal stress method. The modified TCD algorithm synthesizes the linear elastic fracture mechanics, the stress concentration effect and the stress field near the notch root obtained by the finite element analysis software. The results are closer to the test life. Compared with the point method, the midline method is more accurate than the point method in predicting fatigue life. It is found that the modified TCD algorithm has better practicability and accuracy than the traditional method in predicting fatigue life of 4 steel notched specimens under the research conditions in this paper, which provides a new theoretical calculation method for engineering fatigue life estimation. It has great practical significance in engineering.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.15
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