本文選題：數(shù)字圖像相關(guān) + 裂紋��； 參考：《大連理工大學(xué)》2015年碩士論文

【摘要】：焊接結(jié)構(gòu)件廣泛運(yùn)用于壓力容器與管道、工程機(jī)械、船舶、汽車等工業(yè)領(lǐng)域,而焊接不可避免將焊接殘余應(yīng)力殘留在焊接結(jié)構(gòu)件中。在役的焊接結(jié)構(gòu)件隨著服役時間的增加,其中的微觀缺陷會萌發(fā)和擴(kuò)展成為裂紋。裂紋降低了結(jié)構(gòu)的承載能力,造成應(yīng)力集中,裂紋的進(jìn)一步擴(kuò)展甚至導(dǎo)致突發(fā)性和災(zāi)難性事故。因此,對裂紋特性尤其是焊接結(jié)構(gòu)件裂紋特性的研究顯得尤為重要。研究焊接結(jié)構(gòu)件裂紋特性的關(guān)鍵是研究斷裂參量應(yīng)力強(qiáng)度因子、J積分、裂紋尖端張開位移在焊接條件改變時的變化規(guī)律。本文通過實(shí)驗(yàn)法,運(yùn)用數(shù)字圖像相關(guān)(Digital Image Correlation, DIC)技術(shù),以緊湊拉伸(compact tension, CT)試樣為研究對象,采用焊接件與未焊接件的斷裂參量進(jìn)行對比的方法來進(jìn)行裂紋特性的研究。首先,對未焊接CT試件進(jìn)行常溫下的拉伸實(shí)驗(yàn),運(yùn)用數(shù)字圖像相關(guān)測量系統(tǒng)對試件的斷裂參量進(jìn)行測量與計(jì)算,得到各個斷裂參量值以及各值隨載荷的變化規(guī)律。結(jié)果表明：線彈性階段,應(yīng)力強(qiáng)度因子KI隨著載荷的增大呈線性增大規(guī)律；J積分和裂紋尖端張開位移隨著載荷的增大而增大。其次,通過改變裂紋尖端與焊縫中心的距離,改變焊接過程中兩道焊之間的間隔時間,改變兩道焊的焊接方向,對CT試件進(jìn)行焊接,得到不同焊接條件下的焊接殘余應(yīng)力分布,再對各焊接件進(jìn)行拉伸試驗(yàn),通過數(shù)字圖像相關(guān)測量系統(tǒng)得到不同焊接殘余應(yīng)力分布下的裂紋斷裂參量。最后,通過對比未焊接與焊接CT試件在不同焊接條件下CT試件的各個斷裂參量值,得到改變焊接條件后斷裂參量的變化規(guī)律。結(jié)果表明：焊接CT試件的各斷裂參量值小于未焊接CT試件的各斷裂參量值；當(dāng)焊接方向由正反面同向焊接變?yōu)檎疵娈愊蚝附訒r,各斷裂參量值減�。划�(dāng)焊縫中心距離裂紋尖端的距離由8mm變?yōu)?0mm時,各斷裂參量值減�。划�(dāng)兩道焊之間的間隔時間由無間隔到間隔30分鐘時,各斷裂參量值減小。
[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.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG404

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