焊接条件对裂纹特性影响的DIC实验研究

发布时间：2018-06-20 06:20

本文选题：数字图像相关 + 裂纹　；参考：《大连理工大学》2015年硕士论文

【摘要】：焊接结构件广泛运用于压力容器与管道、工程机械、船舶、汽车等工业领域,而焊接不可避免将焊接残余应力残留在焊接结构件中。在役的焊接结构件随着服役时间的增加,其中的微观缺陷会萌发和扩展成为裂纹。裂纹降低了结构的承载能力,造成应力集中,裂纹的进一步扩展甚至导致突发性和灾难性事故。因此,对裂纹特性尤其是焊接结构件裂纹特性的研究显得尤为重要。研究焊接结构件裂纹特性的关键是研究断裂参量应力强度因子、J积分、裂纹尖端张开位移在焊接条件改变时的变化规律。本文通过实验法,运用数字图像相关(Digital Image Correlation, DIC)技术,以紧凑拉伸(compact tension, CT)试样为研究对象,采用焊接件与未焊接件的断裂参量进行对比的方法来进行裂纹特性的研究。首先,对未焊接CT试件进行常温下的拉伸实验,运用数字图像相关测量系统对试件的断裂参量进行测量与计算,得到各个断裂参量值以及各值随载荷的变化规律。结果表明：线弹性阶段,应力强度因子KI随着载荷的增大呈线性增大规律；J积分和裂纹尖端张开位移随着载荷的增大而增大。其次,通过改变裂纹尖端与焊缝中心的距离,改变焊接过程中两道焊之间的间隔时间,改变两道焊的焊接方向,对CT试件进行焊接,得到不同焊接条件下的焊接残余应力分布,再对各焊接件进行拉伸试验,通过数字图像相关测量系统得到不同焊接残余应力分布下的裂纹断裂参量。最后,通过对比未焊接与焊接CT试件在不同焊接条件下CT试件的各个断裂参量值,得到改变焊接条件后断裂参量的变化规律。结果表明：焊接CT试件的各断裂参量值小于未焊接CT试件的各断裂参量值；当焊接方向由正反面同向焊接变为正反面异向焊接时,各断裂参量值减小；当焊缝中心距离裂纹尖端的距离由8mm变为30mm时,各断裂参量值减小；当两道焊之间的间隔时间由无间隔到间隔30分钟时,各断裂参量值减小。
[Abstract]:Welding structural parts are widely used in industrial fields such as pressure vessels and pipes, engineering machinery, ships and automobiles. Welding residual stresses are inevitably retained in welding structures. With the increase of service time in service, the micro defects will germinate and expand into cracks. The cracks reduce the bearing capacity of the structure. The ability to cause the stress concentration, the further expansion of the cracks even causes sudden and catastrophic accidents. Therefore, it is very important to study the crack characteristics especially the crack characteristics of the welded structures. The key to the study of the crack characteristics of the welded structures is to study the stress intensity factor of the fracture parameter, the J integral, the crack tip opening displacement in the welding. In this paper, in this paper, through the experimental method, using Digital Image Correlation (DIC) technology, with the compact tensile (compact tension, CT) sample as the research object, the method of comparing the fracture parameters of the welded parts with the fracture parameters of the non welded parts is used to study the crack characteristics. First, the non welded CT test parts are used. The tensile test at normal temperature is carried out, and the fracture parameters of the specimen are measured and calculated by the digital image correlation measurement system. The values of each fracture parameter and the variation of each value with the load are obtained. The results show that the stress intensity factor KI is linearly increasing with the increase of load; J integral and crack tip tension. The opening displacement increases with the increase of the load. Secondly, by changing the distance between the crack tip and the center of the weld, the interval between the two weld and the welding direction is changed, the welding direction of the two weld is changed, the CT specimen is welded, the residual stress distribution under different welding conditions is obtained, and then the tensile test of the welding parts is carried out. Through the digital image correlation measurement system, the crack fracture parameters under the distribution of different welding residual stresses are obtained. Finally, by comparing the fracture parameters of the CT specimen under different welding conditions under different welding conditions, the change law of the fracture parameters is obtained after the welding conditions are changed. The results show that the fracture parameters of the welded CT specimen are all the fracture parameters of the welded CT specimen. The value is less than the fracture parameter value of the unwelded CT specimen. When the welding direction changes from the positive and reverse side to the reverse side welding, the fracture parameter values decrease; when the distance from the crack tip to the crack tip is changed from 8mm to 30mm, the fracture parameter values decrease; when the interval time between the two channel welding is separated to 30 minutes from the interval to the interval At the time, the value of each fracture parameter decreases.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG404

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