中厚板非对称角焊缝熔透成形温度场模拟及检测

发布时间：2018-04-19 04:04

本文选题：打底焊 + 有限元分析　；参考：《天津工业大学》2017年硕士论文

【摘要】：非对称角接结构是两板厚度不同的特殊T型钢角接结构,该结构在工业等领域应用非常广泛。在焊接过程中,非对称角接板因两板厚度不同而使得热量分配不均,按对称焊缝结构的焊接方法进行施焊难以达到焊接要求。打底焊可以防止角变形或在自动焊时发生烧穿。在带单边V型坡口的厚板对接时,打底焊是必不可少的环节,使得其作用显得尤为重要。此外,因非对称角接结构的热量分配不均使得打底焊很难实现。为解决非对称角接结构打底焊难焊的问题,本文提出了通过改变焊枪角度以实现能量分配,进而获得良好的熔透成形。首先,本文运用有限元分析软件COMSOL,以中厚板非对称角接结构焊接温度场为研究对象,分别研究在焊枪角度为30°、45°及60°时焊缝的熔透情况。模拟分析之前,先建立非对称结构角焊的几何模型,并根据焊接的实际情况,划分不同密度的网格。选取广义双椭球热源作为移动焊接热源并由此建立温度场模型,从而得出温度场的分布规律。采用不同焊接电流和不同焊枪角度的焊接方法,分析熔池成形规律,得到在焊接电流为150A、焊枪角度为45°时焊缝熔透效果最好。其次,建立了基于CCD相机非对称角焊的试验检测平台,拍摄得到在不同焊接工艺、不同焊接电流及不同焊枪角度下的熔池图像,进而对图像进行处理,以获得熔池边缘信息。首先,分别检测MIG焊和TIG焊条件下的熔池形态。分析焊接过程中拍摄的熔池图像,得到不同焊接工艺下的焊接环境变化、熔池流动情况,从而对焊接质量进行分析。结合温度场模拟结果,分析焊接拍摄的图形,从而验证理论分析。最后,根据红外热像仪的测温原理,对非对称角接结构的温度场进行研究,以获得熔池背部温度信息,来验证数值模拟的正确性。采用非制冷焦面红外热像仪,测量了 Q235钢钨极氩弧焊的焊接温度场,并利用数值模拟方法弥补了强弧光干扰的温度场缺失,得到了整体焊接温度场。借助红外热像仪对不同焊接工艺、不同焊接电流及不同焊枪角度下的温度场进行采集和分析,得到了非对称结构件的热量传递过程和表面温度的变化过程,研究了不同条件下对非对称结构件的温度场的影响。通过拍摄得到的热像图,分析不同等温线的范围及熔池所在区域;由熔池区域的大小可以分析出熔池的熔宽等信息。将拍摄得到的热像图与数值模拟温度场进行对比,以验证数值模拟的正确性。
[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 掳angle 45 掳and 60 掳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 掳.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.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG409

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