【摘要】：零件和結(jié)構(gòu)的疲勞壽命預(yù)測對于工程實(shí)際的重要性是不言而喻的,無數(shù)的工程師和科學(xué)家依據(jù)各種疲勞失效實(shí)例和假設(shè)建立起了不同的疲勞壽命預(yù)測方法。本文以45#鋼缺口試樣為研究對象,結(jié)合疲勞實(shí)驗(yàn)對缺口試件的四種疲勞壽命評估方法的實(shí)用性與準(zhǔn)確性進(jìn)行對比研究,所作具體工作如下:根據(jù)相關(guān)國內(nèi)外疲勞試驗(yàn)標(biāo)準(zhǔn)確定了光滑試樣、U形缺口試樣、半圓形缺口試樣的尺寸,結(jié)合ABAQUS有限元分析結(jié)果,分別采用名義應(yīng)力法、局部應(yīng)力應(yīng)變法、TCD算法中的點(diǎn)方法和線方法四種方法對兩種缺口試件在四種應(yīng)力級下疲勞壽命進(jìn)行分析。在疲勞試驗(yàn)機(jī)上針對不同試樣選取四種應(yīng)力級進(jìn)行疲勞試驗(yàn),根據(jù)外推試驗(yàn)法對試驗(yàn)數(shù)據(jù)進(jìn)行處理獲取了不同應(yīng)力級下的試驗(yàn)疲勞壽命,將不同理論疲勞壽命分析結(jié)果與疲勞試驗(yàn)壽命數(shù)據(jù)進(jìn)行對比分析,研究發(fā)現(xiàn)傳統(tǒng)TCD算法在本文研究條件下并不適用,遂采用1 KT?參數(shù)對標(biāo)準(zhǔn)TCD算法進(jìn)行修正,得到了以下結(jié)論:1.求解缺口部件的理論應(yīng)力集中系數(shù)可采用有限元方法代替查表法,更適合工程實(shí)踐;2.相比于其他三種方法,名義應(yīng)力法計(jì)算過程最為簡單,但由于其只考慮了應(yīng)力集中效應(yīng),預(yù)測結(jié)果偏于危險(xiǎn);3.局部應(yīng)力應(yīng)變法的低周疲勞預(yù)測結(jié)果較為保守,中高周疲勞預(yù)測精度相較于名義應(yīng)力法有很大提高;4.修正TCD算法綜合了線彈性斷裂力學(xué)、應(yīng)力集中效應(yīng)并結(jié)合有限元分析軟件獲取的缺口根部附近應(yīng)力場得到了更為接近試驗(yàn)壽命的結(jié)果,其中線方法相對于點(diǎn)方法在本文的研究條件下獲取了更為準(zhǔn)確的疲勞壽命預(yù)測結(jié)果.總結(jié)發(fā)現(xiàn)修正的TCD算法在本文的研究條件下,預(yù)測45#鋼缺口試件的疲勞壽命比傳統(tǒng)方法有更強(qiáng)的實(shí)用性與準(zhǔn)確性,為工程疲勞壽命估算提供了一種新理論計(jì)算方法,有很大工程實(shí)際意義。
[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.
【學(xué)位授予單位】：鄭州大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG142.15

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