摘 要焊接残余应力的存在会导致构件性能降低和使用寿命减少。超声冲击是一种有效消除焊接残余应力的方法。

本课题以55mm厚的Q345钢的MAG焊缝为研究对象。分别采用无超声冲击、盖面前超声冲击和分层超声冲击三种方式制备三类焊接接头,采用小孔法测量三类接头上下表面残余应力的分布，通过使用轮廓法得到纵向和横向残余应力的二维映射，以得到试板内部应力分布。87008

分别对比无超声冲击、盖面前超声冲击和分层超声冲击接头的全厚度应力分布，研究两种超声冲击方式对试样残余应力的影响；对比盖面前超声冲击和分层超声冲击两种超声冲击消除焊接残余应力的差异。研究表明，盖面前超声冲击对上表面横向残余应力的消除率约为33%，分层超声冲击消除残余应力效果不明显，两种超声冲击都能够减小拉应力梯度。

毕业论文关键词：超声冲击；焊接残余应力；盲孔法；轮廓法

Abstract The existence of the welding residual stress can reduce the component performance and service life。 Ultrasonic impact treatment is an effective way to eliminate welding residual stress。

In this paper, the experimental results based on the determination of 55 mm thick Q345 steel welds, which is made by metal active gas arc welding。 First, we fabricate three types of welded joints by non-ultrasonic, ultrasonic impact treatment before cover and layered ultrasonic impact treatment, respectively。 And then measuring the residual stress of three welded plates’ upper surface and under surface with the blind hole method, two-dimensional maps of the longitudinal residual stress and transversal residual stress were obtained by using the contour method, in order to get the distribution status of inner stress of three types of welded joints。

 Compare the residual stress distribution of three types of welded plates; research the effect of different ultrasonic impact treatment on residual stresses。 The studies have shown that after ultrasonic impact treatment before cover, the eliminate rate of transverse residual stress is about 33% on the lateral surface, it’s not obvious that the effect of layered ultrasonic impact  treatment eliminate residual stress。 Both two types of ultrasonic impact treatment could reduce stress gradient effectively。

Keywords: Ultrasonic impact treatment; Residual stress; Blind hole method; 

Contour method

目录

第一章 绪论 1

1。1课题的研究背景及意义 1

1。2残余应力 2

1。2。1 残余应力产生机理 2

1。2。3残余应力危害 2

1。3残余应力测试方法 3

1。3。1盲孔法 4

1。3。2轮廓法 5

1。4消除焊接残余应力的方法 5

1。4。1传统消除焊接应力的方法 5

1。4。2超声冲击消除残余应力 7

1。5研究思路 9

第二章 实验设备及方法 10

2。1试样材料和坡口形式 10

2。2焊接方法 11

2。3超声冲击 12

2。3残余应力测试 14

2。3。1盲孔法 14

2。3。2轮廓法