摘要焊接是一个牵涉到电弧物理、传热、冶金和力学的复杂过程。焊接现象包括焊接时的电磁、传热过程、金属的熔化和凝固、冷却时的相变、焊接应力与变形等。要得到一个高质量的焊接结构必须控制这些因素。一旦各种焊接现象能够实现计算机模拟，我们就可以通过计算机系统来确定焊接各种结构和材料时的最佳设计、最佳工艺方法和焊接参数。本文从这一点出发，在总结前人的工作基础上结合数值计算的方法，对焊接过程产生的温度场、应力场、变形以及焊接后残余应力和变形进行了三维实体动态模拟的研究。48795

由于是一个局部快速加热到高温，并随后快速冷却的过程。随着热源移动，整个焊件的温度随时间和空间急剧变化，材料的物理性能参数也随温度剧烈变化，同时还存在相变时的潜热现象。因此，焊接温度场的分析属于典型的非线性瞬态热传导问题，因为焊接温度场分布十分分布不均匀，在焊接过程中和焊后产生相当大的焊接应力和变形。

本文建立了可行的三维焊接温度场、应力和变形的动态模拟分析方法，为复杂焊接结构进行三维焊接温度场、应力和变形的分析提供了理论依据和指导，促进了有限元分析技术在焊接力学分析以及工程中的应用。

毕业论文关键词：焊接、有限元、数值模拟、温度场、应力变形。

Abstract Welding is a complicated physicochemical process which involves in electromagnetism, heat transferring, metal melting and freezing, phase -change, welding stress and deformation and so on. In order to get high quality welding structure, we have to control these factors.If welding process can be simulated with computer, we will easily determine the best design, procedure method and optimum welding parameter. Based on summing up others' experience, employing numerical calculation method, this paper researches how to realize the 3D dynamic simulation of welding temperature field, stress field and welding deformation when weldment is been welding and welding residual stress and residual deformation when weldment is cooled.

Welding process is that parts of an area is quickly heated to high temperature and then rapidly cooled. With the heat source moving,the whole weldment's temperature sharply changes, and the material'sphysical property parameters also sharply change. At the same time, there is latent heat of melt and phase-change. Therefore, the analysis of welding temperature field is a typical  nonlinear transient heat conduction problem. Because of non-uniform temperature distribution, atthe course of welding and postweld, weldment takes on seriouswelding stress and deformation. 

this paper establishes  a feasible dynamic simulation method on 3D welding temperature field, stress and deformation, which providestheory foundation and  instruction, promotes the  application of FEM(Finite Element Method)on welding mechanics analysis and engineering.

Keywords:welding, finite element, numerical simulation, temperature field, stress and deformation.

目录

第一章  绪论 10

1.1 选题的目的和意义 10

1.2课题的研究现状 11

1.3本文的主要研究内容 14

1.4本文的研究方法及步骤 14

第二章  有限元法及热分析理论 16

2.1有限元法 16

2.1.1有限元法的定义 16

2.1.2有限元的发展与现状 16

2.1.3有限元法的一般描述