• Title, Summary, Keyword: residual stress

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The effect of initial stress induced during the steel manufacturing process on the welding residual stress in multi-pass butt welding

  • Park, Jeong-ung;An, Gyubaek;Woo, Wanchuck
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.10 no.2
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    • pp.129-140
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    • 2018
  • A residual stress generated in the steel structure is broadly categorized into initial residual stress during manufacturing steel material, welding residual stress caused by welding, and heat treatment residual stress by heat treatment. Initial residual stresses induced during the manufacturing process is combined with welding residual stress or heat treatment residual stress, and remained as a final residual stress. Because such final residual stress affects the safety and strength of the structure, it is of utmost importance to measure or predict the magnitude of residual stress, and to apply this point on the design of the structure. In this study, the initial residual stress of steel structures having thicknesses of 25 mm and 70 mm during manufacturing was measured in order to investigate initial residual stress (hereinafter, referred to as initial stress). In addition, thermal elastic plastic FEM analysis was performed with this initial condition, and the effect of initial stress on the welding residual stress was investigated. Further, the reliability of the FE analysis result, considering the initial stress and welding residual stress for the steel structures having two thicknesses, was validated by comparing it with the measured results. In the vicinity of the weld joint, the initial stress is released and finally controlled by the weld residual stress. On the other hand, the farther away from the weld joint, the greater the influence of the initial stress. The range in which the initial stress affects the weld residual stress was not changed by the initial stress. However, in the region where the initial stress occurs in the compressive stress, the magnitude of the weld residual compressive stress varies with the compression or tension of the initial stress. The effect of initial stress on the maximum compression residual stress was far larger when initial stress was considered in case of a thickness of 25 mm with a value of 180 MPa, while in case of thickness at 70 mm, it was 200 MPa. The increase in compressive residual stress is almost the same as the initial stress. However, if initial stress was tensile, there was no significant change in the maximum compression residual stress.

Redistribution of Welding Residual Stress and its Effects on Fatigue Crack Propagation (피로균열이 진전할 때 용접잔류응력의 재분포와 그 영향)

  • 이용복;조남익
    • Journal of Welding and Joining
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    • v.13 no.4
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    • pp.155-162
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    • 1995
  • Redistribution of residual stress and its effects during fatigue crack propagates from tensile residual stress region in weldment are investigated. Tests are performed by using welded CCT specimens of structual rolling steel (SS400) and it makes fatigue crack propagate from tensile residual stress region. For this study tension-tension loading type is selected by external loading condition and magnetizing stress indicator is used correctly to measure redistribution of residual stress according to fatigue crack growth and number of loading cycles. From this result, it is proved that redistribution of residual stress is mainly consist of residual stress released by fatigue crack growth. When fatigue crack propagates from tensile residual stress region residual stress are redistributed and it makes fatigue crack growth rate largely increase. Fatigue crack growth rate is low in case of redistributed residual stress compare with initial distributed residual stress.

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A Study on the Residual Stress Distribution of Pure Titanium Welding Material (순수티타늄 용접재의 잔류응력분포에 관한 연구)

  • Choi Byung-ki;Chang Kyung-chun
    • Journal of the Korean Society of Safety
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    • v.19 no.4
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    • pp.8-13
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    • 2004
  • The purpose of this paper is to investigate the welding residual stress distribution according to the constraint or non-constraint welding condition with titanium commonly using power station, aircraft, and ship. The measuring method of the residual stress was applied stress release rating method with strain gages and a potable strain meter. The x direction residual stress generally showed the tensile residual stress in case of res03int welding. On the other hand, the x direction residual stress under non-restraint welding were changed tensile stress into compressive stress on 15mm away from welding bead center. Also, the y direction residual stress generally showed the tensile residual stress in case of non-restraint welding and the y direction residual stress under restraint welding were changed tensile stress into compressive stress about 60mm away from welding bead center.

A study on the fatigue crack growth behavior of aluminum alloy weldments in welding residual stress fields (용접잔류응력장 중에서의 Aluminum-Alloy용접재료의 피로균열성장거동 연구)

  • 최용식;정영석
    • Journal of Welding and Joining
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    • v.7 no.1
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    • pp.28-35
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    • 1989
  • The fatigue crack growth behavior in GTA butt welded joints of Al-Alloy 5052-H38 was examined using Single Edge Notched(SEN) specimens. It is well known that welding residual stress has marked influence on fatigue crack growth rate in welded structure. In the general area of fatigue crack growth in the presence of residual stress, it is noted that the correction of stress intensity factor (K) to account for residual stress is important for the determination of both stress intensity factor range(.DELTA.K) and stress ratio(R) during a loading cycle. The crack growth rate(da/dN) in welded joints were correlated with the effective stress intensity factor range(.DELTA.Keff) which was estimated by superposition of the respective stress intensity factors for the residual stress field and for the applied stress. However, redistribution of residual stress occurs during crack growth and its effect is not negligible. In this study, fatigue crack growth characteristics of the welded joints were examined by using superposition of redistributed residual stress and discussed in comparison with the results of the initial welding residual stress superposition.

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The Effect of residual stress for fracture behavior in the laser weldment (레이저용접부의 파괴에 미치는 잔류응력의 영향)

  • Jo, Seong-Gyu;Yang, Yeong-Su
    • Proceedings of the Korean Society of Laser Processing Conference
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    • pp.3-8
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    • 2006
  • The integrity of laser welded structures is decided with fracture strength and fatigue strength. This study presents fracture behavior considering residual stress in the laser welding. Experiments are conducted and analyses are performed to explore the influence of residual stress on fracture behavior of bead-on laser welded compact specimen. Fracture experiments are performed using ASTM 1820. The performed analyses included thermo-elasto-plastic analyses for residual stress and subsequent J-integral calculation. A modified J integral is calculated in the presence of residual stresses. The J-integral is path-independent for combination of residual stress field and stress due to mechanical loading. The results indicates that the tensile residual stress near crack front bring the low fracture load while the compressive residual stress bring the high fracture load compared to no residual stress specimen. These results quantitatively understand the influence of residual stress on fracture behavior.

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The Effect of residual stress on fracture behavior in the laser weldment (레이저용접부의 파괴에 미치는 잔류응력의 영향)

  • Cho, Sung-Kyu;Yang, Young-Soo;Noh, Young-Jin
    • Journal of Korean Society of Laser Processing
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    • v.11 no.2
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    • pp.1-7
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    • 2008
  • The integrity of laser welded structures is decided in fracture strength and fatigue strength. This study made an effort to understand the fracture behavior considering residual stress. Experiments are conducted and analyses are performed to explore the influence of residual stress on fracture behavior of bead-on laser welded compact specimen. Fracture experiments are performed using ASTM 1820. The performed analyses included thermo-elasto-plastic analyses for residual stress and subsequent J-integral calculation. A modified J integral is calculated in the presence of residual stresses. The J-integral is path-independent for combination of residual stress field and stress due to mechanical loading. The results indicates that the tensile residual stress near crack front bring the low fracture load while the compressive residual stress bring the high fracture load compared to no residual stress specimen. These results quantitatively understand the influence of residual stress on fracture behavior.

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A Study on Residual Stress Characteristics for Joint of Soft Rock in Ring Shear Tests (링 전단시험기를 이용한 연암의 절리에 대한 잔류강도 특성에 관한 연구)

  • 권준욱;김선명;윤지선
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.281-288
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    • 2000
  • In this study, we tried to determine failure criteria for joints of soft rock using ring shear test machine. The residual stress fellowing shear behavior was determined by the result of ring shear test and direct shear test. Ring shear test with the specimens which cover a large deformation range was adapted to measure a residual stress, and was possible to present the peak stress to present the peak stress to the residual stress at the same time. Residual stress is defined a minimal stress of specimens with a large displacement and the result of the peak residual stress is shown by a size of displacement volume. Therefore, the residual stress in soil was decided by shear stress of maximum shear stress - shear displacement(angle) based on the test result of a hyperbolic function ((equation omitted), a, b = experimental constant). In this study, it was proved that the residual stress of rock joint can be determined by using of this method.

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Effect of heat treatment residual stress on stress behavior of constant stress beam

  • Kwak, Si Young;Hwang, Ho Young
    • Journal of Computational Design and Engineering
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    • v.5 no.1
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    • pp.137-143
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    • 2018
  • Although most casting and heat treatment processes generate significantly high residual stress in the products, this factor is generally not taken into account in the design stage of the product. In this study, experimental study and numerical analysis were conducted on a constant stress beam to examine effects of the residual stress generated during the heat treatment process on yielding behavior of the product in use. A constant stress beam of SUS 304 was designed in order to test the stress behavior related to residual stress. The residual stresses generated during quenching heat treatment of the beam were measured in advance by ESPI (Electronic Speckle-Pattern Interferometry) equipment, and then the external stresses generated while applying a simple external load on the beam were measured. Also, the residual stress distribution generated during the heat treatment process was computed using a numerical analysis program designed for analyzing heat treatment processes. Then, the stress distribution by a simple external load to the beam was combined with the calculated residual stress results of the previous heat treatment step. Finally, the results were compared with experimental ones. Simulation results were in good agreement with the experimental results. Consistency between experimental results and computational results prove that residual stress has significant effects on the stress behavior of mechanical parts. Therefore, the residual stress generated in the previous heat treatment step of casting must be taken into account in the stage of mechanical product design.

Application of Laser Interferometry for Assessment of Surface Residual Stress by Determination of Stress-free State (무잔류 응력상태 결정을 통한 표면 잔류응력장 평가에의 레이저 간섭계 적용)

  • 김동원;이낙규;나경환;권동일
    • Journal of the Semiconductor & Display Technology
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    • v.3 no.2
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    • pp.35-40
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    • 2004
  • The total relaxed stress in annealing and the thermal strain/stress were obtained from the identification of the residual stress-free state using electronic speckle pattern interferometry (ESPI). The residual stress fields in case of both single and film / substrate systems were modeled using the thermo-elastic theory and the relationship between relaxed stresses and displacements. We mapped the surface residual stress fields on the indented bulk Cu and the 0.5 $\mu\textrm{m}$ Au film by ESPI. In indented Cu, the normal and shear residual stress are distributed over -1.7 GPa to 700 MPa and -800 GPa to 600 MPa respectively around the indented point and in deposited Au film on Si wafer, the tensile residual stress is uniformly distributed on the Au film from 500 MPa to 800 MPa. Also we measured the residual stress by the x-ray diffractometer (XRD) for the verification of above residual stress results by ESPI...

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Residual Stress Evolution during Leveling of Hot Rolled High Strength Coils and Camber Prediction by Residual Stress Distribution (냉간 성형용 열연 고강도 강판의 교정 중 잔류응력 변화와 절단 후 캠버 발생 예측)

  • Park, K.C.;Ryu, J.H.
    • Transactions of Materials Processing
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    • v.17 no.2
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    • pp.107-112
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    • 2008
  • In order to investigate the residual stress evolution during the leveling process of hot rolled high strength coils for cold forming, the in-plane residual stress of plate sampled at SPM, rough leveler and finish leveler were measured by cutting method. Residual stress was localized near the edge of plate. As the thickness of plate was increased, the size of residual stress region was expanded. The gradient of residual stress within the plate was reduced during the leveling process. But the residual stress itself was not removed completely within the ranges of tested conditions. The exact camber of cut plate was able to be predicted by the measurement of residual stress distribution after leveling of the plate.