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SUS-304강 용접부의 잔류응력이 피로균열진전속도에 미치는 영향
이택순,양현태 대한용접접합학회 1997 대한용접·접합학회지 Vol.15 No.4
In the weldmentsm the crack propagation rate is changed due to the residual stress. The crack propagation rate is high in the region with the residual stress. However it shows rhw same behavior with the base metal in the region that does not include the residual stress. The fatigue crack growth rate for the material with residual stresses can be predicted more precisely by using the effective stress ratio. The difference between experimental results and prediction results in the initial stage seems to be due to the redistribution of residual stresses and microstructural change.
有限要素法에 의한 Butt 熔接部 殘留應力의 熱彈塑性解析
李澤淳 嶺南大學校 工業技術硏究所 1985 연구보고 Vol.13 No.1
It is well known that welding thermal stress and resulting residual stress influence the strength of welded structre, causing brittle fracture and cracking. During welding, a limited portion of the welded joint is heated up to a very high temperature and cooled down to room temperature. These condition produce thermal stress, which causes distorsion and residual stress of structure. In the thermal cycle, the temperature distribution change with time and it effects the mechanical properties of the metals. In order to perform a reliable theoretical analysis, it is necessary to obtain an accurate informations on the entire histories of material properties during thermal cycle. With the help of thermal elasto-plastic theory method, the author developed a method of finite element analysis of thermal and residual stresses induced in butt weld under a moving electrode in the course of first bead.
AJM을 이용한 HDM에 의한 잔류응력 계측에 관한 연구 1
이택순 대한용접접합학회 1988 대한용접·접합학회지 Vol.6 No.3
The Hole Drilling Method(HDM) is widely used to measure residual stresses in the welded structures. The purpose of this study is to evaluate the accuracy fo measuring residual stresses when drilling the hole by Air-abrasive Jet machine(AJM). Simulated residual stresses wre introduced by applying known stresses to steel bars. These known streses were then compared with measured stresses relaxed from hole drilling. the obtained results are summarized as follows; 1) It was possible to obtain well defined holes with the nozzle designed for this study. 2) If the hole shape is not cylindrical, critical may occur. 3) In the uniaxial strain field, the measurement error of the maximum principal stress was within .+-.10 percent. The orientation angle of the maximum principal stress was within 8.deg. from the given directioin. 4) meausrements were made varying hole depths. Little or no change of stresses occurs since holse were drilled more than the depth of the 0.6 times diameter. 5) The air-abrasive jet machining for drilling holse does not cause appreciable apparent stresses which si critical to measure residual stresses.
고강도 알루미늄 합금 용접부에 있어서의 피로균열전파에 미치는 과하중 효과
이택순,김상태,김인식 대한용접접합학회 1988 대한용접·접합학회지 Vol.6 No.1
Retardation or delay in fatigue crack growth due to overloads are important for the accurate prediction of fatigue lives of structural materials. In this study, retardation of fatigue crack growth in Al 6061-T6 weldments and heat affected zones (HAZ) after single overload cycle had been investigated. Retardation in both weldments and HAZ was observed. It was concluded that retardation in both weldment and HAZ was greater than in base metal due to microstructural change and crack branching and crack closure were major governing factor in retardation.