本文選題：打底焊 + 有限元分析　； 參考：《天津工業(yè)大學(xué)》2017年碩士論文

【摘要】：非對稱角接結(jié)構(gòu)是兩板厚度不同的特殊T型鋼角接結(jié)構(gòu),該結(jié)構(gòu)在工業(yè)等領(lǐng)域應(yīng)用非常廣泛。在焊接過程中,非對稱角接板因兩板厚度不同而使得熱量分配不均,按對稱焊縫結(jié)構(gòu)的焊接方法進(jìn)行施焊難以達(dá)到焊接要求。打底焊可以防止角變形或在自動焊時發(fā)生燒穿。在帶單邊V型坡口的厚板對接時,打底焊是必不可少的環(huán)節(jié),使得其作用顯得尤為重要。此外,因非對稱角接結(jié)構(gòu)的熱量分配不均使得打底焊很難實(shí)現(xiàn)。為解決非對稱角接結(jié)構(gòu)打底焊難焊的問題,本文提出了通過改變焊槍角度以實(shí)現(xiàn)能量分配,進(jìn)而獲得良好的熔透成形。首先,本文運(yùn)用有限元分析軟件COMSOL,以中厚板非對稱角接結(jié)構(gòu)焊接溫度場為研究對象,分別研究在焊槍角度為30°、45°及60°時焊縫的熔透情況。模擬分析之前,先建立非對稱結(jié)構(gòu)角焊的幾何模型,并根據(jù)焊接的實(shí)際情況,劃分不同密度的網(wǎng)格。選取廣義雙橢球熱源作為移動焊接熱源并由此建立溫度場模型,從而得出溫度場的分布規(guī)律。采用不同焊接電流和不同焊槍角度的焊接方法,分析熔池成形規(guī)律,得到在焊接電流為150A、焊槍角度為45°時焊縫熔透效果最好。其次,建立了基于CCD相機(jī)非對稱角焊的試驗(yàn)檢測平臺,拍攝得到在不同焊接工藝、不同焊接電流及不同焊槍角度下的熔池圖像,進(jìn)而對圖像進(jìn)行處理,以獲得熔池邊緣信息。首先,分別檢測MIG焊和TIG焊條件下的熔池形態(tài)。分析焊接過程中拍攝的熔池圖像,得到不同焊接工藝下的焊接環(huán)境變化、熔池流動情況,從而對焊接質(zhì)量進(jìn)行分析。結(jié)合溫度場模擬結(jié)果,分析焊接拍攝的圖形,從而驗(yàn)證理論分析。最后,根據(jù)紅外熱像儀的測溫原理,對非對稱角接結(jié)構(gòu)的溫度場進(jìn)行研究,以獲得熔池背部溫度信息,來驗(yàn)證數(shù)值模擬的正確性。采用非制冷焦面紅外熱像儀,測量了 Q235鋼鎢極氬弧焊的焊接溫度場,并利用數(shù)值模擬方法彌補(bǔ)了強(qiáng)弧光干擾的溫度場缺失,得到了整體焊接溫度場。借助紅外熱像儀對不同焊接工藝、不同焊接電流及不同焊槍角度下的溫度場進(jìn)行采集和分析,得到了非對稱結(jié)構(gòu)件的熱量傳遞過程和表面溫度的變化過程,研究了不同條件下對非對稱結(jié)構(gòu)件的溫度場的影響。通過拍攝得到的熱像圖,分析不同等溫線的范圍及熔池所在區(qū)域;由熔池區(qū)域的大小可以分析出熔池的熔寬等信息。將拍攝得到的熱像圖與數(shù)值模擬溫度場進(jìn)行對比,以驗(yàn)證數(shù)值模擬的正確性。
[Abstract]:Asymmetric corner structure is a special T-section structure with different thickness of two plates. It is widely used in industry and other fields.In the process of welding, the heat distribution of the asymmetrical corner plate is uneven because of the difference in thickness of the two plates, so it is difficult to meet the welding requirements by welding the symmetrical weld structure.Bottom welding can prevent angle deformation or burn-through in automatic welding.Bottom welding is an essential link in the butt joint of thick plate with one side V groove, which makes its function more important.In addition, the uneven distribution of heat in asymmetric angle structure makes it difficult to realize bottom welding.In order to solve the problem that it is difficult to weld at the bottom of asymmetric angle joint structure, this paper puts forward that the energy distribution can be realized by changing the angle of welding torch, and then good penetration forming can be obtained.Firstly, using finite element analysis software COMSOL and taking the welding temperature field of asymmetric angular connection structure of plate as the research object, the penetration of welding seam at 30 擄angle 45 擄and 60 擄is studied respectively.Before simulation and analysis, the geometric model of asymmetrical structure angle welding is established, and the mesh with different density is divided according to the actual condition of welding.The generalized double ellipsoid heat source is selected as the moving welding heat source and the temperature field model is established, and the distribution law of the temperature field is obtained.By using different welding current and different welding torch angle, the weld pool forming law is analyzed. The results show that the weld penetration effect is the best when the welding current is 150A and the welding torch angle is 45 擄.Secondly, an experimental detection platform for asymmetric angle welding based on CCD camera is established. The weld pool images under different welding processes, different welding currents and different welding torch angles are captured, and then the image is processed to obtain the edge information of the weld pool.Firstly, the weld pool morphology of MIG welding and TIG welding was detected respectively.By analyzing the weld pool images taken during the welding process, the changes of welding environment and molten pool flow under different welding processes were obtained, and the welding quality was analyzed.Combined with the simulation results of temperature field, the pattern taken by welding is analyzed, and the theoretical analysis is verified.Finally, according to the temperature measurement principle of infrared thermal imager, the temperature field of asymmetric angular structure is studied to obtain the back temperature information of the molten pool to verify the correctness of the numerical simulation.The welding temperature field of Q235 steel TIG welding was measured by using uncooled focal plane infrared thermal imager, and the temperature field of Q235 steel welding was obtained by using numerical simulation method to compensate for the absence of strong arc interference temperature field.The temperature field of different welding process, different welding current and different welding torch angle were collected and analyzed by infrared thermal imager, and the heat transfer process and surface temperature change process of asymmetric structural parts were obtained.The effect of different conditions on the temperature field of asymmetric structural parts is studied.The range of different isotherms and the region where the molten pool is located are analyzed by taking the thermal image and the information of the melting pool width can be analyzed from the size of the weld pool region.In order to verify the correctness of the numerical simulation, the obtained thermal image is compared with the temperature field of the numerical simulation.
【學(xué)位授予單位】：天津工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG409

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