發(fā)布時(shí)間：2018-08-04 11:25

【摘要】：伴隨著我國(guó)橋梁建設(shè)的發(fā)展,鋼結(jié)構(gòu)橋梁的比重在不斷的增大,出現(xiàn)了大量的焊接細(xì)節(jié)。我國(guó)焊接疲勞設(shè)計(jì)起步相對(duì)較晚,沒(méi)有完善的焊接細(xì)節(jié)的疲勞設(shè)計(jì)標(biāo)準(zhǔn)。若對(duì)結(jié)構(gòu)焊接細(xì)節(jié)設(shè)計(jì)不當(dāng),會(huì)出現(xiàn)鋼橋焊接細(xì)節(jié)的疲勞裂紋,甚至造成嚴(yán)重的事故。 焊接是一個(gè)涉及物理、化學(xué)、力學(xué)的復(fù)雜過(guò)程,焊接加熱冷卻之后結(jié)構(gòu)內(nèi)部會(huì)存在復(fù)雜的殘余應(yīng)力。焊接節(jié)點(diǎn)傳力過(guò)程中的應(yīng)力集中,焊接節(jié)點(diǎn)焊接過(guò)程引起的初始缺陷及使結(jié)構(gòu)呈現(xiàn)受拉狀態(tài)的焊接殘余應(yīng)力是導(dǎo)致焊接節(jié)點(diǎn)疲勞性能顯著降低的直接原因。反復(fù)荷載作用下,為準(zhǔn)確描述焊接節(jié)點(diǎn)實(shí)際應(yīng)力場(chǎng)狀態(tài),需要首先對(duì)焊接殘余應(yīng)力進(jìn)行數(shù)值模擬,再疊加不同荷載幅引起的結(jié)構(gòu)工作應(yīng)力幅。焊接殘余應(yīng)力的準(zhǔn)確模擬對(duì)焊接節(jié)點(diǎn)疲勞性能研究具有重要意義。 本文利用ANSYS程序?qū)?duì)接、T字形、U肋與頂板三種典型焊接細(xì)節(jié)的焊接殘余應(yīng)力進(jìn)行了數(shù)值模擬,并對(duì)焊接接頭危險(xiǎn)點(diǎn)位進(jìn)行了疲勞性能的分析,論文工作有以下幾方面： 1根據(jù)高溫條件下Q345的物理和力學(xué)參數(shù),確定焊接熱源模型、焊接過(guò)程的參數(shù),實(shí)現(xiàn)了焊縫熱源的移動(dòng)加載,得出了三種接頭準(zhǔn)確的焊接過(guò)程溫度場(chǎng)。編寫了不同焊接接頭焊接過(guò)程數(shù)值模擬的APDL命令。 2通過(guò)溫度場(chǎng)和應(yīng)力場(chǎng)的間接耦合調(diào)用三種接頭溫度場(chǎng)的計(jì)算結(jié)果,計(jì)算出殘余應(yīng)力的分布。對(duì)于U肋與頂板接頭,等效殘余應(yīng)力隨頂板厚度的增加而增加,起弧和滅弧的局部,殘余應(yīng)力略高于屈服強(qiáng)度。 3根據(jù)歐洲規(guī)范中三種接頭名義應(yīng)力加載計(jì)算出三種接頭的實(shí)際應(yīng)力,并選取應(yīng)力集中較為嚴(yán)重的部位作為危險(xiǎn)點(diǎn)。通過(guò)該點(diǎn)計(jì)算所得的殘余應(yīng)力與實(shí)際應(yīng)力的疊加,采用Goodman關(guān)系結(jié)合Q345的材料S-N曲線繪制危險(xiǎn)點(diǎn)的新S-N曲線。將計(jì)算結(jié)果與歐洲規(guī)范的焊接接頭S-N曲線對(duì)比,分析了曲線差異的原因并提出了兩個(gè)應(yīng)力修正系數(shù)。
[Abstract]:With the development of the bridge construction in China, the proportion of the steel structure and bridge is increasing, and a lot of welding details have appeared. The welding fatigue design in our country is relatively late, and there is no perfect standard of fatigue design for welding details. A heavy accident.
Welding is a complex process involving physics, chemistry and mechanics. After the welding is heated and cooled, there will be complex residual stresses in the structure. The stress concentration in the process of welding joint force, the initial defects caused by welding joint welding process and the welding residual stress of the structure showing the tensile state of the welded joints lead to the fatigue performance of the welded joints. In order to accurately describe the actual stress field of welding joints under repeated loads, it is necessary to simulate the welding residual stress at first, and then superimpose the working stress amplitude of the structure caused by different load amplitude. The accurate simulation of welding residual stress is of great significance to the study of the fatigue performance of welding node.
In this paper, the ANSYS program is used to simulate the welding residual stresses of three typical welding details such as docking, T shape, U ribs and top plates, and the fatigue properties of the dangerous points of the welded joint are analyzed. The work of this paper has the following aspects:
1 according to the physical and mechanical parameters of Q345 under high temperature, the welding heat source model and the parameters of the welding process are determined. The moving load of the weld heat source is realized, and the accurate welding temperature field of three kinds of joints is obtained. The APDL command of the numerical simulation of the welding process of different welding joints is written.
2 the distribution of residual stress is calculated by calculating the temperature field of the temperature field and the indirect coupling of the stress field, and the distribution of residual stress is calculated. For the U ribs and the top plate joints, the equivalent residual stress increases with the increase of the thickness of the roof. The residual stress is slightly higher than the yield strength.
3 according to the nominal stress loading of three kinds of joint in the European standard, the actual stress of the three kinds of joint is calculated, and the more serious part of the stress concentration is selected as the danger point. The superposition of the residual stress and the actual stress obtained by this point is calculated. The new S-N curve of the dangerous point is drawn by the Goodman relation and the material S-N curve of the material. The calculation will be calculated. Results compared with the S-N curves of welded joints in European standard, the reasons for the difference of curves were analyzed, and two stress correction coefficients were proposed.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：U441;U448.36

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