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 The Society of Naval Architects of Korea 2018 International Journal of Naval Architecture and Oc Vol.10 No.2

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.

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

Jeong-ung Park,Gyubaek An,Wanchuck Woo 대한조선학회 2018 International Journal of Naval Architecture and Oc Vol.10 No.2

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.

Neutron diffraction residual stress analysis during fatigue crack growth retardation of stainless steel

Seo, Sukho,Huang, E-Wen,Woo, Wanchuck,Lee, Soo Yeol Elsevier 2017 International journal of fatigue Vol.104 No.-

<P><B>Abstract</B></P> <P>After tensile overloading during fatigue crack growth, retardation of the crack growth rate was significant. Neutron diffraction was employed to examine the evolution of crack-tip residual stress fields during constant-amplitude cyclic loading and during fatigue crack growth following the overload. It was found that the tensile overload induces larger compressive residual stress and zone size near the crack tip in the crack-growth and crack-opening direction. For the maximum crack growth retardation, the largest compressive residual stresses were measured in the region between an overloading point and the current propagating crack tip, for all three of the orthogonal directions. Such large compressive residual stresses in the crack-wake region are thought to reduce the crack tip driving force, thereby retarding the crack propagation rate significantly. Residual stress mapping was performed to examine the effect of the fatigue stress state on the residual stresses in the three different regions from the centerline to the surface, along the through-thickness direction in the compact-tension specimen. Much larger compressive residual stresses were measured at the surface than at mid-thickness. It is thought that larger compressive residual stresses at the surface result from the plane stress condition, resulting in a slower fatigue crack growth rate at the surface of the specimen.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Neutron diffraction was used to measure residual stress fields near the crack tip. </LI> <LI> A tensile overload induced larger compressive residual stress and zone size. </LI> <LI> The maximum retardation revealed the largest compressive residual stresses. </LI> <LI> Compressive residual stresses were larger at the surface than in the middle. </LI> <LI> Effect of the fatigue stress state on the residual stress was revealed. </LI> </UL> </P>

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

Kwak, Si Young,Hwang, Ho Young Society for Computational Design and Engineering 2018 Journal of computational design and engineering Vol.5 No.1

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.

5083-0 Al합금 鎔接材의 잔류응력에 관한 硏究

권관구(Gwan-Gu Gwon) 산업기술교육훈련학회 2012 산업기술연구논문지 (JITR) Vol.17 No.4

The purpose of this thesis was to investigate the welding characteristics and the residual stress behavior of SS41, commonly using power station, aircraft and ship. The experimented material was GMA welded in order to look over the residual stress distribution was measured under perfect restraint and nonrestraint welding conditions. From these test, we reached conclusion as followings ; The welding residual stress welded specimens was much higher in restraint condition than in nonrestraint. In case of restraint welding, the σx direction residual stress was measured the tensile residual stress. In case of nonrestraint welding, it was rapidly changed to compressive residual stress at about 15mm from welding bead center. In case of nonrestraint welding, the σy direction residual stress was measured the tensile residual stress. In case of restraint welding, it was changed to compressive residual stress at 40~45mm from welding bead center.

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

Si Young Kwak,Ho Young Hwang 한국CDE학회 2018 Journal of computational design and engineering Vol.5 No.1

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 resid-ual 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 pro-gram 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 agree-ment 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.

링 전단시험기를 이용한 암석절리의 잔류강도 특성에 관한 연구

권준욱,김선명,윤지선 한국지반공학회 2000 한국지반공학회논문집 Vol.16 No.6

Residual stress is defined as a minimum stress with a large displacement of specimens and the residual stress after peak shear stress appears with displacement volume but there is no provision to select the residual stress. In the previous study, residual stress was recorded when the change of shear load is small in the condition of the strain more than 15%. But, in this study, hyperbolic function((No Abstract.see full/text), b=experimental constant) of soil test is adapted to joint of rock and the propriety is investigated. In a landslide and landsliding of artificial slope, wedge failure of tunnel with a large displacement, tests are simulated from peak stress to residual stress for safety analysis. But now. direct shear stress and triaxial compressive tests are usually performed to find out characteristics of shear stress about joint. Although these tests get a small displacement, that data of peak stress and residual stress are used for safety analysis. In this study, we tried to determine failure criteria for joints of rock using ring shear test machine. The residual stress following shear behavior was determined by the result of ring shear test and direct shear test. In conclusion, after comparing the results of the two test, we found that cohesion(c) and internal friction angle(ø) of ring shear test are 30% and 22% respectively of those of the direct shear test.

인장 및 압축 등방 잔류응력 측정을 위한 누프 압입시험의 응력환산계수 결정

정민재 ( Min Jae Jeong ),김영천 ( Young-cheon Kim ) 한국부식방식학회 2021 Corrosion Science and Technology Vol.20 No.6

Instrumented indentation testing has been widely used for residual stress measurement. The Knoop indentation is mainly selected for determining anisotropic mechanical properties and non-equibiaxial residual stress. However, the measurement of equibiaxial stress state and compressive residual stress on a specimen surface using Knoop indentation is neither fully comprehended nor unavailable. In this study, we investigated stress conversion factors for measuring Knoop indentation on equibiaxial stress state through indentation depth using finite element analysis. Knoop indentation was conducted for specimens to determine tensile and compressive equibiaxial residual stress. Both were found to be increased proportionally according to indentation depth. The stress field beneath the indenter during each indentation test was also analyzed. Compressive residual stress suppressed the in-plane expansion of stress field during indentation. In contrast, stress fields beneath the indenter developed diagonally downward for tensile residual stress. Furthermore, differences between trends of stress fields at long and short axes of Knoop indenter were observed due to difference in indenting angles and the projected area of plastic zone that was exposed to residual stress.

용접 잔류응력장 중에서의 Aluminum-Alloy 용접재의 피로균열 성장거동 연구(Ⅱ) : 잔류응력 재 분포 Redistribution of the Residual Stress

최용식,정영석 成均館大學校 科學技術硏究所 1988 論文集 Vol.39 No.1

It is well known that welding residual stress has a great 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(ΔK) and stress ratio (R) during a loading cycle. The superposition technique can be applied generally for determination of K. The crack growth rate of the welds correlated with the effective stress intensity factor range, ΔK_eff, which was estimated by superposition of the respective stress intensity factors for the residual stress fields and for the applied stresses. However, redistribution of residual stress occurs during crack growth and its effect is not negligible. In this study, fatigue crack growth characteristics of the weld joint were examined by using superposition of redistributed residual stress and examined in comparison with that of the initial residual stress superposition.

Effect of welding residual stress on operating stress of nuclear turbine low pressure rotor

Tan Long,Zhao Liangyin,Zhao Pengcheng,Wang Lulu,Pan Jiajing,Zhao Xiuxiu 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.8

The purpose of this study is to investigate the effect of welding residual stress on operating stress in designing a nuclear turbine welded rotor. A two-dimensional axisymmetric finite element model is employed to calculate the residual stress before and after post weld heat treatment (PWHT), and then the superposition of residual stress after PWHT and operating stress at normal speed and overspeed were discussed. The investigated results show that operating stress can be affected significantly by welding residual stress, and the distribution trend of superposition stress at the weld area is mainly determined by welding residual stress. The superposition of residual stress and operating stress is linear superposition, and the hoop stress distribution of superposition stress is similar with the distribution of residual stress. With the increasing overspeed, the distribution pattern of the hoop superimposed stress remains almost unchanged, while the stress level increases