【摘要】：一般情況下,典型的白車身結(jié)構(gòu)通常含有多達(dá)3000~5000個(gè)焊點(diǎn)。焊點(diǎn)周圍存在較嚴(yán)重的應(yīng)力集中,疲勞裂紋易于形成和擴(kuò)展,據(jù)統(tǒng)計(jì)大約50%的汽車結(jié)構(gòu)的疲勞問(wèn)題和焊點(diǎn)有關(guān),大約80%的車身疲勞問(wèn)題和焊點(diǎn)有關(guān)。因此,在設(shè)計(jì)的早期運(yùn)用計(jì)算機(jī)輔助分析的手段,對(duì)焊點(diǎn)進(jìn)行疲勞壽命預(yù)測(cè),對(duì)于有效降低生產(chǎn)成本,縮短汽車設(shè)計(jì)開發(fā)周期,提高產(chǎn)品的質(zhì)量有著重要的現(xiàn)實(shí)意義�，F(xiàn)今面對(duì)能源短缺、環(huán)境污染等一系列21世紀(jì)人類發(fā)展的重要問(wèn)題,減輕汽車自重、降低燃油消耗已成為各大汽車生產(chǎn)商提高競(jìng)爭(zhēng)能力的關(guān)鍵。因此,傳統(tǒng)的低碳鋼正越來(lái)越多地被高強(qiáng)度鋼所取代,它能夠在不降低車身強(qiáng)度、剛度等各項(xiàng)性能指標(biāo)的前提下,減少車身重量。本文正是在此背景下對(duì)高強(qiáng)鋼點(diǎn)焊接頭的疲勞仿真預(yù)測(cè)方法展開相關(guān)研究工作。針對(duì)傳統(tǒng)的基于力的LBF方法和基于應(yīng)力的LMS方法這兩種焊點(diǎn)疲勞壽命仿真預(yù)測(cè)方法所存在的預(yù)測(cè)精度不高、建模和計(jì)算效率偏低等問(wèn)題,本文提出了一種新的焊點(diǎn)疲勞壽命仿真預(yù)測(cè)模型,從斷裂力學(xué)的角度考慮焊點(diǎn)的疲勞失效,采用一種模塊化焊點(diǎn)模型,提出了一種焊點(diǎn)裂紋在板厚擴(kuò)展路徑上的平均應(yīng)力強(qiáng)度因子DK作為疲勞壽命的評(píng)價(jià)參量。選擇目前常用的高強(qiáng)度低合金鋼(HSLA340GI)和雙相高強(qiáng)鋼(DP600GI)這兩種高強(qiáng)鋼材料、4種板厚組合的電阻點(diǎn)焊接頭進(jìn)行了剪切疲勞試驗(yàn),并與傳統(tǒng)的LBF和LMS方法進(jìn)行預(yù)測(cè)精度的對(duì)比分析。主要的研究?jī)?nèi)容如下:(1)介紹了高強(qiáng)鋼電阻點(diǎn)焊的的研究現(xiàn)狀,簡(jiǎn)要敘述了點(diǎn)焊接頭疲勞壽命預(yù)測(cè)的研究現(xiàn)狀,介紹了疲勞理論的發(fā)展過(guò)程,指出傳統(tǒng)的焊點(diǎn)疲勞壽命預(yù)測(cè)方法無(wú)法直接應(yīng)用到高強(qiáng)鋼焊點(diǎn)疲勞壽命預(yù)測(cè)中。(2)采用了一種模塊化焊點(diǎn)建模方法,相對(duì)于傳統(tǒng)LBF和LMS方法所采用的焊點(diǎn)模型,該模型可以準(zhǔn)確模擬焊點(diǎn)實(shí)際位置,更加符合焊點(diǎn)的物理幾何特征,并且不會(huì)降低建模和計(jì)算效率,運(yùn)用該模型進(jìn)行焊點(diǎn)疲勞仿真分析能夠獲得更準(zhǔn)確的疲勞壽命預(yù)測(cè)結(jié)果。(3)采用焊點(diǎn)疲勞裂紋在板厚擴(kuò)展路徑上的平均應(yīng)力強(qiáng)度因子DK作為焊點(diǎn)疲勞壽命的評(píng)價(jià)參量,對(duì)HSLA340GI和DP600GI兩種高強(qiáng)鋼材料、4種板厚組合的電阻點(diǎn)焊接頭進(jìn)行了剪切疲勞試驗(yàn),得到了不同點(diǎn)焊接頭樣件的疲勞壽命數(shù)據(jù),通過(guò)DK與焊點(diǎn)疲勞數(shù)據(jù)的回歸分析,得到一條主DK-N曲線,并與傳統(tǒng)的LBF和LMS方法進(jìn)行了預(yù)測(cè)精度的對(duì)比分析。結(jié)果表明本文提出的焊點(diǎn)疲勞壽命仿真預(yù)測(cè)模型能夠有效預(yù)測(cè)高強(qiáng)鋼點(diǎn)焊接頭的疲勞壽命,且預(yù)測(cè)精度高于傳統(tǒng)的LBF和LMS方法。本文研究表明:本文提出的基于平均應(yīng)力強(qiáng)度因子的焊點(diǎn)疲勞壽命仿真預(yù)測(cè)模型能夠有效預(yù)測(cè)高強(qiáng)鋼點(diǎn)焊接頭的疲勞壽命,并且預(yù)測(cè)精度高于傳統(tǒng)的LBF和LMS方法,具有較高的工程應(yīng)用價(jià)值。
[Abstract]:Typically, a typical white-body structure contains as many as 3, 000-5, 000 solder joints. There is a serious stress concentration around the solder joint, and fatigue cracks are easy to form and expand. According to statistics, about 50% of the fatigue problems of automobile structures are related to solder joints, and about 80% of the body fatigue problems are related to solder joints. Therefore, in the early stage of design, using the means of computer aided analysis to predict the fatigue life of butt welding spot is of great practical significance to effectively reduce production cost, shorten the period of automobile design and development, and improve the quality of products. In the face of energy shortage, environmental pollution and a series of important problems of human development in the 21st century, reducing auto weight and fuel consumption has become the key to improve the competitiveness of automobile manufacturers. Therefore, traditional low carbon steel is more and more replaced by high strength steel, which can reduce the weight of body without reducing the body strength, stiffness and other performance indexes. In this paper, the fatigue simulation prediction method of spot welding joint of high strength steel is studied in this paper. The traditional force-based LBF method and the stress-based LMS method are used to predict the fatigue life of solder joint. The prediction accuracy is not high and the efficiency of modeling and calculation is low. In this paper, a new simulation model for predicting the fatigue life of solder joint is proposed. The fatigue failure of solder joint is considered from the point of view of fracture mechanics, and a modular solder joint model is adopted. The average stress intensity factor (DK) of solder joint crack on the plate thickness propagation path is proposed as the evaluation parameter of fatigue life. The shear fatigue tests of resistance spot welding joints with four kinds of plate thickness combination of high strength low alloy steel (HSLA340GI) and dual phase high strength steel (DP600GI) were carried out, and the prediction accuracy was compared with that of traditional LBF and LMS methods. The main research contents are as follows: (1) the research status of resistance spot welding of high strength steel is introduced, the research status of fatigue life prediction of spot welding joint is briefly described, and the development process of fatigue theory is introduced. It is pointed out that the traditional prediction method of solder joint fatigue life can not be directly applied to the prediction of fatigue life of high strength steel solder joint. (2) A modular solder joint modeling method is adopted, compared with the solder joint model used by traditional LBF and LMS methods. The model can accurately simulate the actual position of solder joint, which is more consistent with the physical geometric characteristics of solder joint, and does not reduce the efficiency of modeling and calculation. Using the model to simulate solder joint fatigue can obtain more accurate prediction results of fatigue life. (3) the average stress intensity factor (DK) of solder joint fatigue crack on the plate thickness propagation path is used as the evaluation parameter of solder joint fatigue life. The shear fatigue test of resistance spot welding joint with two kinds of high strength steel materials (HSLA340GI and DP600GI) was carried out. The fatigue life data of different spot welded joints were obtained, and the regression analysis between DK and joint fatigue data was carried out. A main DK-N curve is obtained and compared with the traditional LBF and LMS methods. The results show that the model proposed in this paper can effectively predict the fatigue life of high-strength steel spot welded joints, and the prediction accuracy is higher than that of the traditional LBF and LMS methods. The results show that the proposed simulation model based on average stress intensity factor can effectively predict the fatigue life of high-strength steel spot welded joints, and the prediction accuracy is higher than that of traditional LBF and LMS methods. It has high engineering application value.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：U466;TG405

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 龔曉叁;韓紹昌;黃開發(fā);;B340LA低合金高強(qiáng)鋼電阻點(diǎn)焊工藝試驗(yàn)優(yōu)化與分析[J];熱加工工藝;2014年23期

2 宋占勛;方少軒;謝基龍;;T形焊接接頭根部裂紋應(yīng)力強(qiáng)度因子研究[J];機(jī)械工程學(xué)報(bào);2013年02期

3 謝斌;成艾國(guó);陳濤;董立強(qiáng);;基于汽車碰撞仿真的實(shí)體單元焊點(diǎn)模擬方法研究[J];中國(guó)機(jī)械工程;2011年10期

4 許君;張延松;朱平;陳關(guān)龍;;雙相鋼搭接點(diǎn)焊接頭疲勞壽命分析[J];焊接學(xué)報(bào);2008年05期

5 蔡洪能;王雅生;張占偉;楊宏偉;;汽車用鋼板電阻點(diǎn)焊工藝參數(shù)優(yōu)化選擇方法[J];材料工程;2006年S1期

6 葉平;沈劍平;王光耀;吳劍;;汽車輕量化用高強(qiáng)度鋼現(xiàn)狀及其發(fā)展趨勢(shì)[J];機(jī)械工程材料;2006年03期

7 龍靖宇;機(jī)械設(shè)備焊接結(jié)構(gòu)的疲勞壽命研究[J];煤礦機(jī)械;2005年06期

8 康永林,孫建林;高強(qiáng)度薄鋼板研究的新進(jìn)展及其在汽車上的應(yīng)用[J];鋼鐵;2002年05期

9 林曉斌;基于有限元的疲勞設(shè)計(jì)分析系統(tǒng)MSC/FATIGUE[J];中國(guó)機(jī)械工程;1998年11期

10 林曉斌;工程預(yù)測(cè)焊點(diǎn)疲勞壽命[J];中國(guó)機(jī)械工程;1998年11期

相關(guān)碩士學(xué)位論文 前2條

1 李琦;B340LA高強(qiáng)鋼電阻點(diǎn)焊工藝及質(zhì)量監(jiān)控模式研究[D];吉林大學(xué);2012年

2 甄舒;B340/590DP高強(qiáng)鋼電阻點(diǎn)焊接頭組織與力學(xué)性能的研究[D];吉林大學(xué);2010年

，

本文編號(hào)：2144194