DP590钢板激光胶接点焊工艺及接头强度分析

发布时间：2019-05-18 13:49

【摘要】：激光胶接点焊是一种融合了激光点焊与粘接连接各自优点的薄板材料新型连接技术,其连接接头具有优良的动/静态承载能力以及密封特性。本文以1.5mm厚DP590汽车用钢板为试验材料,借助高功率光纤激光器,研究激光胶接点焊的连接工艺,分析接头的静拉伸及疲劳性能。开展激光点焊和激光胶接点焊工艺的试验研究。以焊接功率、焊接时间、离焦量为变量,设计三因素三水平正交试验,通过拉剪试验获得不同焊接工艺条件下接头的抗拉强度。结果表明:激光点焊接头的最优工艺参数组合为,焊接功率1800 W,焊接时间200 ms,离焦量+3 mm;激光胶接点焊的最优工艺参数组合为,焊接功率1400 W,焊接时间1000 ms,离焦量+3 mm。采用AUTODYN软件建立了激光胶接点焊接头的有限元模型,分析胶层受热气化后对焊接熔池的冲击效应。随着粘弹性衰减系数的增大,即胶体粘度下降,胶层检测点压力历程曲线中压力最大值呈现增大的趋势,焊点处表面依次出现穿孔、结瘤、平整等焊接现象,仿真结果与实验表征的现象相符,证实了胶体粘度对焊接工艺及接头质量的影响。运用极差分析和方差分析,探究了焊接功率、焊接时间和离焦量对不同焊接接头峰值载荷、峰值位移及能量吸收值的影响。试验结果表明:激光点焊试验中,焊接时间对接头各项力学性能指标的影响最大,焊接功率次之,离焦量的影响最小;激光胶接点焊试验中,焊接功率对接头各项力学性能指标影响最大,焊接时间次之,离焦量的影响最小。借助疲劳实验机,在拉剪频率10 Hz,载荷比0.1条件下分别对激光点焊、激光胶接点焊和粘接三种接头进行疲劳性能测试。通过数据拟合获得了三种接头的载荷—寿命曲线,结果表明:激光胶接点焊接头的疲劳性能最好,粘接接头次之,激光点焊接头的疲劳性能最差。采用扫描电子显微镜对激光点焊接头和激光胶接点焊接头进行断口分析,结果表明:激光点焊接头的拉伸断口表现为韧性断裂,激光胶接点焊接头的拉伸断口表现为韧性断裂和脆性断裂;两种接头的疲劳断口均表现为脆性断裂。运用超声波扫描显微镜对焊接接头进行无损检测,获取不同焊接工艺条件下接头的超声波C扫描图像,提取不同位置处的超声波A扫描信号,并根据超声波A扫描信号变化特征对超声波C扫描图像进行分区,激光点焊接头C扫描图像分为:焊核区、热影响区和母材区,激光胶接点焊接头分为:焊核区、热影响区气化层区和胶层区。借助超声波C扫描图像灰度值的变化特征测得了焊核直径,激光点焊接头焊核直径变化范围0.66 mm-2.73 mm,激光胶接点焊接头焊核直径变化范围 1.23 mm-2.51 mm。
[Abstract]:Laser bonded spot welding is a new connecting technology of thin plate material, which combines the advantages of laser spot welding and bonding connection. the joint has excellent dynamic / static bearing capacity and sealing characteristics. In this paper, 1.5mm thick DP590 automobile steel plate is used as experimental material, with the help of high power fiber laser, the bonding technology of laser bonding spot welding is studied, and the static tensile and fatigue properties of the joint are analyzed. The experimental research on laser spot welding and laser bonding spot welding is carried out. Taking welding power, welding time and defocusing amount as variables, the orthogonal test of three factors and three levels is designed, and the tensile strength of the joint under different welding conditions is obtained by tensile shear test. The results show that the optimum process parameters of laser spot welding joint are as follows: welding power 1800 W, welding time 200 ms, defocus 3 mm; The optimum process parameters of laser bonding spot welding are as follows: welding power 1400 W, welding time 1000 ms, defocus 3 mm. The finite element model of laser bonding joint is established by AUTODYN software, and the impact effect of adhesive layer on welding pool after heating and gasification is analyzed. With the increase of Viscoelastic attenuation coefficient, that is, the colloid viscosity decreases, the maximum pressure value in the pressure history curve of the testing point of the adhesive layer tends to increase, and the welding phenomena such as perforation, nodulation and leveling appear on the surface of the welding point in turn. The simulation results are in good agreement with the experimental results, and the effect of colloid viscosity on welding process and joint quality is confirmed. The effects of welding power, welding time and defocusing amount on the peak load, peak displacement and energy absorption of different welded joints were investigated by means of range analysis and variance analysis. The test results show that in the laser spot welding test, the welding time has the greatest influence on the mechanical properties of the joint, the welding power is the second, and the defocusing amount has the least effect. In the laser bonding spot welding test, the welding power has the greatest influence on the mechanical properties of the joint, the welding time is the second, and the defocusing amount has the least effect. With the help of fatigue test machine, the fatigue properties of laser spot welding, laser adhesive spot welding and bonding were tested under the condition of 10 Hz, load ratio of tension and shear frequency. The load-life curves of three kinds of joints are obtained by data fitting. The results show that the fatigue properties of laser bonded joint are the best, the bonded joint is the second, and the fatigue property of laser spot welded joint is the worst. The fracture surface of laser spot welding joint and laser bonded spot welding joint is analyzed by scanning electron microscope (SEM). The results show that the tensile fracture of laser spot welding joint is ductile fracture. The tensile fracture of laser bonded joint is ductile fracture and brittle fracture. The fatigue fracture of the two kinds of joints is brittle fracture. Ultrasonic scanning microscope is used to detect the welded joints, and the ultrasonic C scanning images of the joints under different welding conditions are obtained, and the ultrasonic A scanning signals at different positions are extracted. According to the change characteristics of ultrasonic A scanning signal, the ultrasonic C scanning image is divided into: welding core zone, heat affected zone and base metal zone, laser bonding joint is divided into: welding core zone, laser spot welding joint C scanning image is divided into: welding core zone, heat affected zone and base metal zone. Heat affected zone Gasification layer area and rubber layer area. With the help of the variation characteristics of gray value of ultrasonic C scan image, the welding core diameter of laser spot welding joint is measured. The change range of laser spot welding joint welding core diameter is 0.66 mm-2.73 mm, and the change range of laser bonding joint welding core diameter is 1.23 mm-2.51 mm..
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG456.6

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