• Title/Summary/Keyword: Thermal Elastic Plastic Analysis

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A Study on the Simulation of Welding Deformation for accurate Assembling (고정밀도 조립을 위한 용접 변형의 해석에 관한 연구)

  • Sung, Ki-Chan;Jang, Kyung-Bok;Jung, Jin-Woo;Kang, Sung-Soo
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.4
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    • pp.129-134
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    • 2001
  • It is essential to predict the welding deformation at assembly stage, to increase productivity through mechanization and automation effectively. A practical analysis method appled for production engineering was proposed to simulate the deformation of arc welding, with an analytical model using finite element method solving thermal-elastic-plastic behavior. In this research, for accurate assembling, 3-D thermal-elastic-plastic finite element model is used to simulate the out-of-plane deformation caused by arc welding. Efforts have been made to find out the efficient method to improve the reliability and accuracy of the numerical calculation. Each of theories of small and large deformation is applied in solving 3-D thermal-elastic-plastic problem to compare with their efficiency about calculation imes and solution accuracy. When solid elements are used in a bending problem of a plate, phenomenon that the predictive deformation is more than that of actual survey is observed. To prevent this phenomenon, reduced integration method for element is employed instead of full integration that is generally used in 3-D thermal-elastic-plastic analysis.

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Visco-Elastic Fracture Analysis of IC Package under Thermal Loading (열하중하에 있는 IC 패키지의 점탄성 파괴해석)

  • 이강용;양지혁
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.1
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    • pp.43-50
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    • 1998
  • The purpose of the paper is to protect the damage of plastic IC package with searching the cause of the fracture due to the delamination and crack when the encapsulant of plastic IC package is on viscoelastic behavior with the effect of creep on high temperature, The model for analysis is the plastic SOJ package with dimpled diepad in the IR soldering process of surface mounting technology. The risk of delamination with calculating the distribution of viscoelastic thermal stress in the package without the crack in the surface mounting process is checked. The package model with the perfect delamination between chip and diepad is chosen to estimate the resistance against fracture in thermal loading with calculating C (t)-integrals according to the change of the design. The optimum design to depress the delamination and crack is presented.

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A Study on the Integrity Evaluation Method of Subclad Crack Under Pressurized Thermal Shock (가압열충격 사고시 클래드 하부균열 안전성 평가 방법에 관한 연구)

  • Kim, Yeong-Jin;Kim, Jin-Su;Gu, Bon-Geol;Choe, Jae-Bung;Park, Yun-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.7
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    • pp.1139-1146
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    • 2001
  • The reactor pressure vessel(RPV) is usually cladded with stainless steel to prevent corrosion and radiation embrittlement, and a number of subclad cracks have been found during an in-service-inspection. These subclad cracks should be assured for a safe operation under normal conditions and faulted conditions such as pressurized thermal shock(PTS). Currently available integrity assessment procedure for an RPV, ASME Code Sec. XI, are built on the basis of linear fracture mechanics (LEFM). In PTS condition, however, thermal stress and mechanical stress give rise to high tensile stress at the cladding and elastic-plastic behavior is expected in this area. Therfore, ASME Code Sec. XI is overly conservative in assessing the structural integrity under PTS condition. In this paper, the fracture parameter (stress intensity factor, K, and RT(sub)NDT) from elastic analysis using ASME Sec. XI and finite element method were validated against 3-D elastic-plastic finite element analyses. The difference between elastic and elastic-plastic analysis became significant with increasing crack depth. Therfore, it is recommended to perform elastic-plastic analysis for the accurate assessment of subclad cracks under TPS which causes plastic deformation at the cladding.

Three Dimensional Thermal-Elastic Plastic Analysis of GMAW Considering the Melting of Weld Bead (비드의 용용상태를 고려한 가스메탈 아크용접의 3차원 열탄소성 변형 해석)

  • Jang-Hyun Lee;Jong-Gye Shin;Ji-Hoon Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.39 no.1
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    • pp.49-60
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    • 2002
  • Welding is essential in ship production since welding is very popular method for joining two or more metals. However, welding causes residual stress and distortion and these give a bad influence to the structure strength and assembly of ship blocks. Therefore, prediction and treatment of residual stress and distortion is a key to accuracy control in shipyard. In this paper, a computational procedure, based on thermal-elastic-plastic 3-dimensional FEA, has been suggested to simulate butt and fillet welding process. In the simulation process, temperature distribution at each time step is obtained by heat transfer analysis and then thermal deformation analysis is done with obtained temperature distributions to find the residual stress and distortion. In heat transfer analysis, enthalpy method is used to realize phase change at melting temperature. Also element birth and death method is used to simulate adding of weld metal in both heat transfer analysis and thermal elastic plastic analysis. The proposed procedure is verified by related researches and the results show good agreement with those of related researches.

A Study on the Mechanical Behavior of Resistance Spot Welding by Finite Element Method (유한요소법에 의한 저항 점용접부의 역학적 특성에 관한 연구)

  • 방한서;주성민;방희선;차용훈;최병기
    • Journal of Welding and Joining
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    • v.17 no.5
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    • pp.77-82
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    • 1999
  • Resistance spot welding process is completed in very short time and there are many factors affecting on the generation of heat. It is difficult to control these experimental factors and monitor distribution of the temperature and stresses in the experimental analysis case. and too much time and expense are required for the experimental trials to fine proper welding condition. So numerical analyses have been attempted steadily, but most numerical analyses on the resistance spot welding are mainly focused on thermal behavior. Therefore, in this paper, the numerical analysis of mechanical behavior as well as heat conduction is carried out for the spot welding process. For this numerical analysis, axial symmetric computer program for the spot welding analysis by F.E.M. has been developed considering heat conduction and thermal elastic-plastic theory. Material properties depending on temperature such as density, heat conductivity, heat expansion coefficient, specific heat, yield stress, elastic modulus, and specific resistance are considered. Using the results of temperature distribution obtained from heat conduction analysis, the thermal elastic-plastic analysis is carried out to clarify mechanical behavior of spot welded specimen. In order to evaluate the effect of residual stresses, numerical analyses are carried out under tension-shear load in two cases respectively; one with residual stress, the other without residual stresses.

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Thermal Elastic-Plastic Analysis of Strength Considering Temperature Rise due to Plastic Deformation by Dynamic Leading in Welded Joint (동적하중하에서의 용접이음부의 강도적특성에 대한 온도상승을 고려한 열탄소성 해석)

  • 안규백;망월정인;대전흉;방한서;농전정남
    • Journal of Welding and Joining
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    • v.21 no.3
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    • pp.68-77
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    • 2003
  • It is important to understand the characteristics of material strength and fracture under the dynamic loading like as earthquakes to assure the integrity of welded structures. The characteristics of dynamic strength and fracture in structural steels and their welded joints should be evaluated based on the effects of the strain rate and the service temperature. It is difficult to predict or measure temperature rise history with the corresponding stress-strain behavior. In particular, material behaviors beyond the uniform elongation can not be precisely evaluated, though the behavior at large strain region after the maximum loading point is much important for the evaluation of fracture. In this paper, the coupling phenomena of temperature and stress-strain fields under the dynamic loading was simulated by using the finite element method. The modified rate-temperature parameter was defined by accounting for the effect of temperature rise under the dynamic deformation, and it was applied to the fully-coupled analysis between heat conduction and thermal elastic-plastic behavior. Temperature rise and stress-strain behavior including complicated phenomena were studies after the maximum loading point in structural steels and their undermatched joints and compared with the measured values.

Analysis of Residual Stress Relaxation in Welded Joints due to External Loads (외부하중에 의한 용접 체결부의 잔류응력 이완 특성 해석에 관한 연구)

  • Jang, Chang-Doo;Song, Ha-Cheol;Jo, Young-Chun
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2003.10a
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    • pp.167-170
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    • 2003
  • Thermal elastic-plastic analysis was performed to assess the initial residual stress distribution of welded joints considering temperature dependent material properties. The test model was the idealized boxing fillet specimen, frequently appeared in the joints of longitudinal and transverse members of ship structure. Residual stress relaxations due to external loads were analyzed by subsequent elastic-plastic analysis considering loading and unloading steps, and the characteristics of residual stress relaxations were discussed with the levels of external loads. Additionally, to define the fatigue life of crack initiation and propagation, the S-N data for each crack length were appraised.

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A Study on Welding Residual Stress by Numerical Simulation on friction Stir Welding

  • Bang, H.S.;Kim, H.J.;Go, M.S.;Chang, W.S.;Lee, C.W.
    • International Journal of Korean Welding Society
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    • v.2 no.1
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    • pp.62-66
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    • 2002
  • The Friction Stir Welding (FSW) is a new joining method that was developed at The Welding Institute (TWI) in England in 1991. It applied heating by the rotational friction and material plastic flow. It was developed as a new joining method to solve the problems of epochally in the welding of Al alloys. In the study, 6000series of Alloy composed of Al-Mg-Si, one of the Al alloys that are utilized for shipbuilding and construction, is selected as a specimen and the numerical is executed against the welded zone of FSW. The material used in this study had the unique properties of strength and anti-corrosion, but since the welded joint of this material is easily softened by the welding heat, FSW is executed and the numerical analysis is carried out around the joint. To examine the mechanical behaviors and properties, F.E.M analysis is executed and the developed thermal-elastic-plastic finite analysis are used.

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Structural Analysis of Gas Generator Regenerative Cooling Chamber (재생냉각형 가스발생기 챔버 구조해석)

  • Ryu, Chul-Sung;Kim, Hong-Jip;Choi, Hwan-Seok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.10
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    • pp.1046-1052
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    • 2007
  • Elastic-plastic structural analysis for regenerative cooling chamber of gas generator was performed. Uniaxial tension test was conducted for STS316L at room and high temperature conditions to get the material data necessary for the structural analysis of the chamber which was operated under thermal load and high internal pressure. Physical properties including thermal conductivity, specific heat and thermal expansion were also measured. The structural analysis for four different types of regenerative cooling chamber of gas generator revealed that increased cooling performance decreased the thermal load and strain of the cooling channel structure. The results propose that in order for the regenerative cooling gas generator chamber to have high structural stability with endurance to high mechanical and thermal loads, it is important for the chamber to be designed to have high cooling performance.

Structural Analysis of Gas Generator Regenerative Cooling Chamber (가스발생기 재생냉각 챔버 구조해석)

  • Ryu, Chul-Sung;Choi, Hwan-Seok
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.802-807
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    • 2007
  • Elastic-plastic structural analysis for regenerative cooling chamber of gas generator was performed. Uniaxial tension test was also conducted for STS316L at room and high temperature conditions to get the material data necessary for the structural analysis of the chamber which is operated under thermal load and high internal pressure. Physical properties including thermal conductivity, specific heat and thermal expansion data were also measured. The structural analysis for four different types of regenerative cooling chamber of gas generator revealed that increased cooling performance decreases the thermal load and strain of the cooling channel. The results propose that in order for the regenerative cooling gas generator chamber to have high structural stability with endurance to high mechanical and thermal loads, it is important for the chamber to be designed to have high cooling performance.

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