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.

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 influence of initial stress on wave propagation and dynamic elastic coefficients

Li, Xibing,Tao, Ming Techno-Press 2015 Geomechanics & engineering Vol.8 No.3

The governing equations of wave propagation in one dimension of elastic continuum materials are investigated by taking the influence of the initial stress into account. After a short review of the theory of elastic wave propagation in a rock mass with an initial stress, results indicate that the initial stress differentially influences P-wave and S-wave propagation. For example, when the initial stress is homogeneous, for the P-wave, the initial stress only affects the magnitude of the elastic coefficients, but for the S-wave, the initial stress not only influences the elastic coefficients but also changes the governing equation of wave propagation. In addition, the P-wave and S-wave velocities were measured for granite samples at a low initial stress state; the results indicate that the seismic velocities increase with the initial stress. The analysis of the previous data of seismic velocities and elastic coefficients in rocks under ultra-high hydrostatic initial stress are also investigated.

Effects of Initial Condition of Steel Plate on Welding Deformation and Residual Stress due to Welding

PARK. J. U,LEE H. W 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.3

The effects of initial deflection and initial residual stress in steel plate on the out-of-plane deformation and residual stress due to welding are investigated from analysis results of thermal elastic-plastic FEM modeling with large deflection theory. Initial residual stress due to plate forming has very little effects on welding deformation and welding residual stress. For initial deflection, with concave profile (Type Ⅰ), welding induced deformation has the same type as initial deflection and its magnitudes are small. When initial deflection is in the direction parallel to weld line (Type Ⅱ), welding induced deformation has minor variations. When initial deflection is bended in the direction normal to weld line (Type Ⅲ), welding deformation was largely generated along the width direction of the steel plate. On the other hand, the variation in type of initial deflection does not affect the residual stress and plastic strain.

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.

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 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.

Propagation of p- and T-waves in solid-liquid of thermoelastic media subjected to initial stress and magnetic field in the context of CT-theory

S. M. Abo-Dahab,A. M. Abd-Alla,A. Kilicman 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.2

The effect of magnetic field and initial stress on plane wave propagation is discussed. We have investigated the problem of reflectionand refraction of the thermoelastic wave at a magnetized solid-liquid interface in presence of initial stress. In the context of the CT-theory(Classical dynamical theory) of thermoelasticity, the problem has been solved. The boundary conditions at the interface for (i) displacementcontinuity, (ii) vanishing the tangential displacement, (iii) continuity of normal force per unit initial area, (iv) tangential force perunit initial area must vanish, and (v) continuity of temperature are applied. The amplitude ratios for the incident p- and T-waves havebeen obtained. The reflection and transmitted coefficients for the incident waves are computed numerically, considering the initial stressand magnetic field effect and presented graphically. Comparisons are made with the results in the absence and presence of initial stressand magnetic field. The results indicate that the effect of initial stress and magnetic field on wave propagation are very pronounced.

Influence of initial stresses on the critical velocity of the moving load acting in the interior of the hollow cylinder surrounded by an infinite elastic medium

Surkay D. Akbarov,Mahir A. Mehdiyev 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.1

The bi-material elastic system consisting of the pre-stressed hollow cylinder and pre-stresses surrounding infinite elastic medium is considered and it is assumed that the mentioned initial stresses in this system are caused with the compressing or stretching uniformly distributed normal forces acting at infinity in the direction which is parallel to the cylinder's axis. Moreover, it is assumed that on the internal surface of the cylinder the ring load which moves with constant velocity acts and within these frameworks it is required to determine the influence of the aforementioned initial stresses on the critical velocity of the moving load. The corresponding investigations are carried out within the framework of the so-called three-dimensional linearized theory of elastic waves in initially stresses bodies and the axisymmetric stress-strain state case is considered. The “moving coordinate system” method is used and the Fourier transform is employed for solution to the formulated mathematical problem and Fourier transformation of the sought values are determined analytically. However, the originals of those are determined numerically with the use of the Sommerfeld contour method. The critical velocity is determined from the criterion, according to which, the magnitudes of the absolute values of the stresses and displacements caused with the moving load approaches an infinity. Numerical results on the influence of the initial stresses on the critical velocity and interface normal and shear stresses are presented and discussed. In particular, it is established that the initial stretching (compressing) of the constituents of the system under consideration causes a decrease (an increase) in the values of the critical velocity.

Influence of initial stresses on the critical velocity of the moving load acting in the interior of the hollow cylinder surrounded by an infinite elastic medium

Akbarov, Surkay D.,Mehdiyev, Mahir A. Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.1

The bi-material elastic system consisting of the pre-stressed hollow cylinder and pre-stresses surrounding infinite elastic medium is considered and it is assumed that the mentioned initial stresses in this system are caused with the compressing or stretching uniformly distributed normal forces acting at infinity in the direction which is parallel to the cylinder's axis. Moreover, it is assumed that on the internal surface of the cylinder the ring load which moves with constant velocity acts and within these frameworks it is required to determine the influence of the aforementioned initial stresses on the critical velocity of the moving load. The corresponding investigations are carried out within the framework of the so-called three-dimensional linearized theory of elastic waves in initially stresses bodies and the axisymmetric stress-strain state case is considered. The "moving coordinate system" method is used and the Fourier transform is employed for solution to the formulated mathematical problem and Fourier transformation of the sought values are determined analytically. However, the originals of those are determined numerically with the use of the Sommerfeld contour method. The critical velocity is determined from the criterion, according to which, the magnitudes of the absolute values of the stresses and displacements caused with the moving load approaches an infinity. Numerical results on the influence of the initial stresses on the critical velocity and interface normal and shear stresses are presented and discussed. In particular, it is established that the initial stretching (compressing) of the constituents of the system under consideration causes a decrease (an increase) in the values of the critical velocity.