焊接变形高精度测量方法的研究

发布时间：2018-06-20 17:32

本文选题：变形测量 + 固有变形　；参考：《重庆交通大学》2017年硕士论文

【摘要】：金属材料的焊接过程是一个冷却速度非常快的非线性过程。整个焊接热循环的过程中的不均匀的温度场和局部塑性变形和比容不同的组织导致金属材料焊接结构件不可避免的发生焊接变形。然而通过简单的经验公式不能够精确的预测焊接过程中发生的焊接变形,特别是大型复杂的金属材料焊接件的焊接变形。伴随着计算机技术的发展,基于有限元分析的方法被广泛的应用到计算焊接变形的领域。当前基于有限元分析的焊接变形预测方法主要有两种。一种是热-弹-塑性有限元法,另一种方法是基于固有应变理论的弹性有限元法。由于热-弹-塑性有限元法运算量大、速度慢,只适用于预测中小型焊接件的焊接变形。而固有应变法不着眼整个焊接和冷却过程,而是将固有变形当作初始应变进行弹性有限元分析,在预测大型焊接件焊接变形方法中固有应变法得到了更为广泛的运用。本文系统地阐述了热弹塑性有限元理论、固有应变有限元理论和固有变形的逆解析原理。基于高效、高精度的数值模拟研究背景,本文采用基于有限元分析的固有变形逆解析方法来获取金属材料焊接结构件的固有变形。目前测量金属材料焊接变形的方法多种多样,本文通过分析静态测量的各种方法和瞬态测量的各种方法,详细阐述了这些变形测量方法的优点和缺点。为了进一步提高固有变形逆解析结果的精度,本文采用BRTApe×710接触式三维坐标测量仪对金属薄板焊接变形进行测量,提出了获得金属焊接结构件中面上三维坐标值的计算方法。即在焊接薄板上选取的标志点位置加工小孔,然后在测量这些小孔附近八个点的三维坐标,将测量获得的坐标值经过一系列运算得到小孔中心的三维坐标。将计算得到的小孔中心三维坐标值代入开发的逆解析程序可以得到金属薄板的固有变形,最后将金属薄板的固有变形值代入顺解析程序中进行固有变形的弹性有限元分析。为了验证该仪器测量结果的有效性和测量精度是否满足高精度的要求,本论文以2 mm和3 mm金属焊接薄板表面堆焊焊接接头为例,以计算得到的小孔中心三维空间坐标为已知参数,基于逆解析方法求得了各成分固有变形,并采用固有应变法预测了2 mm和3 mm金属薄板焊接变形。通过比较分析发现,尽管焊件板厚只相差1 mm,但焊接变形的特征和变形量却有显著的差别,采用该测量方法及算法能获得焊接接头中面上较精确的三维坐标,无论是对变形量较大的2 mm板还是对变形相对较小的3 mm板而言,基于逆解析方法都能获得准确有效的固有变形各成分。
[Abstract]:The welding process of metal material is a very fast nonlinear process. The uneven temperature field, local plastic deformation and different specific volume structure during the whole welding thermal cycle process lead to the inevitable welding deformation of the welded structural parts of metal materials. However, the simple empirical formula can not accurately predict the welding deformation in the welding process, especially the welding deformation of large and complex metal materials. With the development of computer technology, finite element analysis (FEM) is widely used to calculate welding deformation. There are two main methods of welding deformation prediction based on finite element analysis. One is thermo-elastic-plastic finite element method, the other is elastic finite element method based on inherent strain theory. Due to the large computation and slow speed, thermo-elastic-plastic finite element method is only suitable for predicting welding deformation of small and medium-sized welded parts. However, the inherent strain method does not focus on the whole welding and cooling process, but takes the inherent deformation as the initial strain for elastic finite element analysis. It is widely used in predicting the welding deformation of large welded parts. In this paper, thermoelastic-plastic finite element theory, inherent strain finite element theory and inverse analytical principle of inherent deformation are systematically expounded. Based on the research background of high efficiency and high precision numerical simulation, this paper uses the inverse analysis method of inherent deformation based on finite element analysis to obtain the inherent deformation of welded structural parts of metal materials. There are a variety of methods for measuring welding deformation of metal materials at present. The advantages and disadvantages of these methods are described in detail by analyzing various methods of static measurement and transient measurement. In order to improve the accuracy of inverse analysis of inherent deformation, this paper uses BRTApe 脳 710 contact 3D coordinate measuring instrument to measure the welding deformation of metal sheet, and puts forward a method to calculate the value of 3D coordinate on the surface of metal welded structure. In other words, the position of the mark points selected on the welded thin plate is used to process the holes, then the three-dimensional coordinates of the eight points near these holes are measured, and the coordinate values obtained from the measurements are calculated through a series of operations to get the three-dimensional coordinates of the center of the small holes. The original deformation of the thin metal plate can be obtained by replacing the calculated three-dimensional coordinate value of the center of the small hole with the developed inverse analytical program. Finally, the intrinsic deformation value of the thin metal plate can be replaced into the program to carry out the elastic finite element analysis of the inherent deformation. In order to verify the validity of the measurement results and whether the measurement accuracy meets the requirements of high accuracy, this paper takes the surfacing welding joint of 2 mm and 3 mm metal welded sheet as an example. Taking the three dimensional coordinates of the center of the small hole as known parameters, the inherent deformation of each component is obtained based on inverse analytical method, and the welding deformation of 2 mm and 3 mm metal thin plates is predicted by the inherent strain method. Through comparison and analysis, it is found that, although the thickness difference of welding plate is only 1 mm, there are significant differences in the characteristics and deformation of welding deformation. Using this measuring method and algorithm, the more accurate three-dimensional coordinates on the middle surface of welded joint can be obtained. For the 2 mm plate with large deformation and the 3 mm plate with relatively small deformation, the exact and effective components of inherent deformation can be obtained based on inverse analytical method.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG404

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