發(fā)布時(shí)間：2018-02-27 16:19

  本文關(guān)鍵詞： 起重機(jī) 箱形主梁 焊縫 等效結(jié)構(gòu)應(yīng)力法 子模型技術(shù) 疲勞壽命　出處：《鄭州大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：起重機(jī)是最為常用和重要的特種設(shè)備，主要是由大型板材通過焊接而成的箱形結(jié)構(gòu)，因此焊接結(jié)構(gòu)的疲勞失效形式在很大程度上就決定了起重機(jī)結(jié)構(gòu)的失效。受到焊接過程中的各種不確定性因素的影響，在焊接結(jié)構(gòu)的焊縫位置難免會(huì)存在一定的焊接缺陷（氣孔、夾渣、未熔透等）和應(yīng)力集中現(xiàn)象，所以疲勞失效也往往主要發(fā)生在焊縫位置。 焊縫處的節(jié)點(diǎn)應(yīng)力奇異，使用傳統(tǒng)有限元法分析得到的焊縫位置的應(yīng)力，其結(jié)果對(duì)有限單元網(wǎng)格尺寸和類型相當(dāng)敏感，故而難以計(jì)算出符合工程實(shí)際的應(yīng)力結(jié)果，對(duì)結(jié)構(gòu)的疲勞壽命預(yù)測造成困難。為了能夠合理有效地評(píng)估起重機(jī)結(jié)構(gòu)的疲勞失效性能，本文首先對(duì)結(jié)構(gòu)疲勞壽命分析的研究背景及國內(nèi)外發(fā)展現(xiàn)狀進(jìn)行了概述和總結(jié)，并且通過對(duì)比分析現(xiàn)有評(píng)估方法中存在的一些問題，確定本課題研究的方法：基于網(wǎng)格不敏感結(jié)構(gòu)應(yīng)力和主S-N曲線法（等效結(jié)構(gòu)應(yīng)力法）來預(yù)測起重機(jī)金屬結(jié)構(gòu)的疲勞壽命。其次，為了有效應(yīng)用等效結(jié)構(gòu)應(yīng)力法，文中重點(diǎn)對(duì)其理論進(jìn)行了整理，并結(jié)合現(xiàn)有知識(shí)對(duì)該方法中的重要公式進(jìn)行了理論推導(dǎo)。接著根據(jù)起重機(jī)的疲勞失效形式，確定以某廠生產(chǎn)的最大額定起升重量為50噸，，跨度為31.5米的橋式起重機(jī)箱形主梁為分析對(duì)象，采用有限元方法對(duì)其進(jìn)行靜態(tài)分析，結(jié)果表明該起重機(jī)主梁結(jié)構(gòu)的靜強(qiáng)度和剛度都符合設(shè)計(jì)要求。接著，對(duì)比靜態(tài)分析結(jié)果與試驗(yàn)測試結(jié)果，驗(yàn)證了力學(xué)模型簡化、建模方式的正確性以及分析結(jié)果的可靠性。以結(jié)構(gòu)靜態(tài)分析為基礎(chǔ)確定危險(xiǎn)焊縫位置，采用“殼到實(shí)體”有限元子模型分析技術(shù)建立了關(guān)鍵位置處包含焊縫細(xì)節(jié)的子模型，并對(duì)其進(jìn)行靜力分析。隨后，對(duì)疲勞主S-N曲線的數(shù)學(xué)模型進(jìn)行了概述，并結(jié)合實(shí)例驗(yàn)證了等效結(jié)構(gòu)應(yīng)力法的網(wǎng)格不敏感性及壽命預(yù)測結(jié)果的準(zhǔn)確性。最后，將子模型分析的應(yīng)力通過結(jié)構(gòu)應(yīng)力轉(zhuǎn)化計(jì)算主要焊縫的等效結(jié)構(gòu)應(yīng)力，進(jìn)而對(duì)該金屬結(jié)構(gòu)的疲勞壽命進(jìn)行了預(yù)估，結(jié)果表明，主要焊縫具有很好的抗疲勞性能，滿足設(shè)計(jì)要求。 最后，本文還對(duì)課題研究過程中存在的不完善之處進(jìn)行了分析和總結(jié)，并提出了有待進(jìn)一步解決的問題，希望在后期研究中得以完善和解決。
[Abstract]:Crane is the most commonly used and important special equipment, mainly made of large plate through welding box structure, Therefore, the fatigue failure form of welded structure determines the failure of crane structure to a great extent. It is inevitable that there are some welding defects (porosity, slag inclusion, not penetration) and stress concentration in the weld position of the welded structure, so fatigue failure often occurs in the weld position. The stress singularity of the joints at the weld seam is very sensitive to the size and type of finite element mesh, so it is difficult to calculate the stress results which accord with the engineering practice. It is difficult to predict the fatigue life of the structure. In order to evaluate the fatigue failure performance of the crane structure reasonably and effectively, this paper firstly summarizes the research background of the fatigue life analysis of the structure and its development status at home and abroad. And through the comparative analysis of some problems in the existing evaluation methods, In order to effectively apply the equivalent structural stress method, the fatigue life of crane metal structure is predicted based on the grid insensitive structural stress and the principal S-N curve (equivalent structural stress method). In this paper, the theory of the crane is mainly sorted out, and the important formulas in this method are deduced in combination with the existing knowledge. Then, according to the fatigue failure form of crane, it is determined that the maximum rated lifting weight of a certain factory is 50 tons. The box girder of the bridge crane with a span of 31.5 meters is analyzed by using the finite element method. The results show that the static strength and stiffness of the main girder structure of the crane meet the design requirements. By comparing the static analysis results with the test results, the simplified mechanical model, the correctness of the modeling method and the reliability of the analysis results are verified. The location of the dangerous welds is determined on the basis of the structural static analysis. In this paper, the finite element submodel analysis technique of "shell to solid" is used to establish the submodel containing weld details at the key position, and the static analysis is carried out. Then, the mathematical model of the fatigue principal S-N curve is summarized. The grid insensitivity of the equivalent structural stress method and the accuracy of the life prediction results are verified by an example. Finally, the equivalent structural stress of the main weld is calculated by transforming the stress of the sub-model into the structural stress. Furthermore, the fatigue life of the metal structure is predicted. The results show that the main weld has good fatigue resistance and meets the design requirements. Finally, this paper analyzes and summarizes the imperfections existing in the course of the research, and puts forward the problems to be solved further, hoping to be perfected and solved in the later research.
【學(xué)位授予單位】：鄭州大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TH21

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