超声波激振随焊控制铝合金焊接应力及变形的应力应变演变研究

发布时间：2018-05-14 05:10

本文选题：铝合金 + 焊接变形　；参考：《华侨大学》2015年硕士论文

【摘要】：铝及其合金由于具有优良的物理力学性能,在工业生产中有着广泛的应用。但由于铝合金本身的线膨胀系数较大、导热率较高等特性,铝合金薄板结构在焊接过程中会出现较大的焊接变形,严重影响产品质量,并造成一定程度的浪费和经济损失。超声波激振随焊方法是一种控制焊接变形的新方法,它将功率超声引入到焊接过程中,通过连续激振熔池后方处于塑性应变区的金属,使其产生塑性延展,增加冷却过程中产生的拉伸塑性应变,降低焊后固有应变,从而较小焊接残余应力,进而减小焊接变形。本课题在超声激振随焊方法的基础上,采用有限元数值模拟与实验验证相结合的方法,研究超声激振随焊过程中动态应力应变的演变规律,进一步阐述超声激振随焊方法控制铝合金薄板焊接变形的本质机理。本文首先介绍了固有应变理论中的经典力学模型,应用固有应变理论详细地阐述了超声激振随焊控制铝合金薄板焊接应力及变形的基本原理。对LY12铝合金常规TIG焊接过程的温度场进行了有限元数值分析,研究了温度场分布及热循环曲线,并确定了塑性应变区。基于温度场的分析结果,应用有限元方法分别研究了常规焊与激振随焊过程中动态应力应变的演变过程,并进行了对比分析,发现了激振过程中不同区域应变变化的三种情况。随后应用红外热成像仪及多路温度测试仪测量铝合金薄板焊接过程中的温度数值,将实验数据与模拟结果进行对比分析发现,两者吻合良好,验证了温度场模拟结果的正确性。应用静态应变仪通过切条法分别测量了常规焊与激振随焊后铝合金薄板弹性区的残余应变,实验数据与模拟结果吻合良好,间接验证了焊接应力应变场模拟结果的正确性。研究结果表明,激振随焊方法能够有效地降低焊接残余应力,减小焊接变形。在激振力的作用下,热源后方的冷凝收缩金属能够发生明显的塑性延展,且由于延展量的不同,最终的固有应变值也不相同。
[Abstract]:Aluminum and its alloys have been widely used in industrial production due to their excellent physical and mechanical properties. However, due to the large linear expansion coefficient and high thermal conductivity of aluminum alloy, large welding deformation will occur in the welding process of aluminum alloy thin plate structure, which will seriously affect the product quality, and cause a certain degree of waste and economic loss. The ultrasonic vibration following welding method is a new method to control the welding deformation. It introduces the power ultrasonic into the welding process and makes the metal in the plastic strain zone behind the continuous excited pool produce plastic extension. The tensile plastic strain produced during cooling is increased and the inherent strain after welding is reduced, thus the residual stress of welding is reduced and the welding deformation is reduced. On the basis of ultrasonic excited vibration welding method, the dynamic stress-strain evolution law of ultrasonic excited vibration welding process is studied by means of finite element numerical simulation and experimental verification. The essential mechanism of controlling welding deformation of aluminum alloy sheet by ultrasonic induced vibration following welding method is further expounded. In this paper, the classical mechanical model of inherent strain theory is introduced, and the basic principle of ultrasonic induced vibration welding for controlling welding stress and deformation of aluminum alloy sheet is described in detail by using inherent strain theory. The temperature field of LY12 aluminum alloy during conventional TIG welding was numerically analyzed by finite element method. The distribution of temperature field and thermal cycle curve were studied, and the plastic strain zone was determined. Based on the results of temperature field analysis, the dynamic stress-strain evolution process of conventional welding and excited vibration with welding is studied by using finite element method. Then the infrared thermal imager and multi-channel temperature tester are used to measure the temperature values in the welding process of aluminum alloy sheet. The experimental data are compared with the simulation results and the results are in good agreement with each other, which verifies the correctness of the simulation results of the temperature field. The residual strain in elastic zone of aluminum alloy sheet after conventional welding and excited vibration welding was measured by static strain meter by cutting strip method. The experimental data are in good agreement with the simulation results, which indirectly verify the correctness of the simulation results of welding stress and strain field. The results show that the method can effectively reduce welding residual stress and welding deformation. Under the action of the exciting force, the condensing shrinkage metal behind the heat source can take place obvious plastic extension, and the ultimate intrinsic strain value is also different because of the different amount of extension.
【学位授予单位】：华侨大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG457.14

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