【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)傳力過程中的應(yīng)力集中,焊接節(jié)點(diǎn)焊接過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)確的焊接過程溫度場(chǎng)。編寫了不同焊接接頭焊接過程數(shù)值模擬的APDL命令。 2通過溫度場(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 bridge construction in China, the proportion of steel bridge is increasing, and a lot of welding details appear. Welding fatigue design in China started relatively late, and there is no perfect fatigue design standard for welding details. If the welding details of the structure are not properly designed, the fatigue cracks of the welding details of the steel bridge will appear, and even cause serious accidents. Welding is a complex process involving physics, chemistry and mechanics. The stress concentration in the process of welding joint transmission, the initial defects caused by welding process and the welding residual stress which make the structure appear tensile state are the direct reasons for the obvious reduction of fatigue properties of welded joints. In order to accurately describe the actual stress field of welded joints under repeated loads, it is necessary to simulate the welding residual stress first, and then to superimpose the working stress amplitude of the structure caused by different load amplitudes. The accurate simulation of welding residual stress is of great significance to the fatigue performance of welded joints. In this paper, the welding residual stress of three typical welding details of butt joint T-shaped U-rib and roof is simulated by ANSYS program, and the fatigue performance of welded joint at dangerous point is analyzed. According to the physical and mechanical parameters of Q345 at high temperature, the model of welding heat source and the parameters of welding process are determined, and the moving loading of weld heat source is realized. The accurate welding temperature field of three kinds of joints is obtained. APDL commands for numerical simulation of welding process of different welded joints are compiled. 2 the distribution of residual stress is calculated by indirect coupling of temperature field and stress field. For U-rib and roof joints, the equivalent residual stress increases with the thickness of the roof. The residual stress is slightly higher than the yield strength. 3 the actual stresses of the three joints are calculated according to the nominal stress loading of the three joints in the European Code, and the places where the stress concentration is more serious are selected as the dangerous points. Through the superposition of residual stress and actual stress calculated at this point, a new S-N curve of dangerous point is drawn by combining the Goodman relation with the material S-N curve of Q345. By comparing the calculated results with the S-N curves of welded joints in European specifications, the reasons for the difference of the curves are analyzed and two stress correction coefficients are 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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