本文選題：汽車輕量化　切入點(diǎn)：激光焊接　出處：《武漢理工大學(xué)》2015年碩士論文

【摘要】：汽車輕量化是汽車工業(yè)未來發(fā)展的主要趨勢,也是解決能源消耗過快、減少環(huán)境污染的重要手段之一。車身重量占汽車總重量的40%左右,對實(shí)現(xiàn)汽車整體結(jié)構(gòu)的輕量化有很重要的意義。使用先進(jìn)材料和先進(jìn)的連接方式是實(shí)現(xiàn)車身輕量化的重要途徑。因此,在車身材質(zhì)方面采用高強(qiáng)度鋼或輕質(zhì)合金代替?zhèn)鹘y(tǒng)鋼板,同時在車身成形工藝方面采用激光焊接代替點(diǎn)焊、電弧焊等傳統(tǒng)焊接方式引起了廣泛關(guān)注。本論文的主要目的是研究車身新型材料先進(jìn)高強(qiáng)鋼以及輕質(zhì)鋁合金的激光焊接過程,采用有限元方法對焊接溫度場和應(yīng)力場的分布特點(diǎn)與變化規(guī)律進(jìn)行仿真分析,并進(jìn)一步討論工藝參數(shù)對焊接結(jié)果的影響規(guī)律,從而為激光焊接的實(shí)際應(yīng)用提供理論依據(jù)和參考。本論文的主要內(nèi)容包括:(1)建立了車身典型焊接部位車頂與側(cè)圍的幾何模型,利用Hyper Mesh軟件建立有限元分析模型導(dǎo)入到ANSYS軟件中進(jìn)行有限元分析;對不同的熱源模型進(jìn)行討論和總結(jié),根據(jù)激光深熔焊匙孔形狀和焊縫熔合線熱點(diǎn),提出了采用高斯面熱源和峰值遞增式圓柱體熱源作為熱源模型,并利用ANSYS特有的編程語言和生死單元技術(shù)實(shí)現(xiàn)了熱源不規(guī)則移動、焊縫有序生成和循環(huán)加載過程。(2)對材料分別為BH鋼和DP600高強(qiáng)鋼的車頂與側(cè)圍激光焊接過程進(jìn)行仿真模擬,研究了焊接熔池、溫度場及熱應(yīng)力場的分布特點(diǎn)和變化規(guī)律,并分析了焊接工藝參數(shù)對熔池、溫度場和熱應(yīng)力場的影響規(guī)律。結(jié)果表明:熔池尺寸和焊縫的最高溫度隨功率升高而增大,隨焊接速度升高而減小;焊縫熱應(yīng)力隨功率升高而減小,隨焊接速度升高而增大。(3)對材料為輕質(zhì)6061鋁合金的車頂與側(cè)圍激光焊接過程進(jìn)行仿真模擬,研究了焊接熔池、溫度場及熱應(yīng)力場的分布和變化規(guī)律,并分析了鋁合金焊縫溫度場的變化規(guī)律,發(fā)現(xiàn)鋁合金焊接溫度場具有冷卻快且熱應(yīng)力沿焊縫中心線兩側(cè)集中的特點(diǎn)。(4)搭建了激光焊接熱歷程測量系統(tǒng),對激光焊接過程中不同位置的溫度變化進(jìn)行全程測量和記錄。通過測量結(jié)果與模擬結(jié)果對比,驗(yàn)證了有限元模型和熱源模型的可靠性,從而為激光焊接的工藝制定以及數(shù)值仿真提供了依據(jù)。
[Abstract]:Automobile lightweight is the main trend in the future development of automobile industry, and it is also one of the important means to solve the problem of excessive energy consumption and reduce environmental pollution. Body weight accounts for about 40% of the total vehicle weight. It is very important to realize the lightweight of the whole automobile structure. The use of advanced materials and the advanced connection mode is an important way to realize the lightweight of the body. Therefore, in the body material aspect, the high strength steel or light alloy is used instead of the traditional steel plate, At the same time, laser welding instead of spot welding, arc welding and other traditional welding methods have attracted wide attention. The main purpose of this paper is to study the laser welding process of advanced high-strength steel and light aluminum alloy. The distribution and variation of welding temperature field and stress field are simulated by finite element method, and the influence of process parameters on welding results is discussed. The main contents of this paper include: (1) the geometric model of roof and side circumference in typical welding position of car body is established. The finite element analysis model is established by Hyper Mesh software and imported into ANSYS software for finite element analysis. Different heat source models are discussed and summarized. According to the shape of keyhole and the hot spot of weld fusion line in laser deep fusion welding, different heat source models are discussed and summarized. The Gao Si surface heat source and the cylinder heat source with increasing peak value are used as the heat source model, and the irregular movement of the heat source is realized by using the special programming language of ANSYS and the technology of birth and death unit. The process of laser welding on the roof and side of BH steel and DP600 high strength steel was simulated. The distribution and variation of weld pool, temperature field and thermal stress field were studied. The influence of welding process parameters on weld pool, temperature field and thermal stress field is analyzed. The results show that the size of weld pool and the maximum temperature of weld increase with the increase of power and decrease with the increase of welding speed. The thermal stress of weld decreases with the increase of power and increases with the increase of welding speed. The laser welding process of roof and side of 6061 aluminum alloy with light weight is simulated and the weld pool is studied. The distribution and variation law of temperature field and thermal stress field, and the variation law of temperature field of aluminum alloy weld are analyzed. It is found that the welding temperature field of aluminum alloy has the characteristics of fast cooling and thermal stress concentration along both sides of the center line of the weld. The temperature changes in different positions during laser welding were measured and recorded. The reliability of the finite element model and the heat source model were verified by comparing the measured results with the simulation results. Therefore, it provides the basis for laser welding process formulation and numerical simulation.
【學(xué)位授予單位】：武漢理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG456.7

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