The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Keiji Nakacho - One of the best experts on this subject based on the ideXlab platform.
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A Simple Estimating Method for Reduction of Welding Residual Stresses in Thick Welded Joint From Stress-Relief Annealing—Part IV: Applicability of the Simple Estimating Method for Stress-Relief Annealing of Thick Welded Joint
Journal of Pressure Vessel Technology, 2002Co-Authors: Keiji NakachoAbstract:Stress-relief annealing (SR treatment) is often applied to relieve welding residual Stresses in the fabrication process of pressure vessels, etc. This study aims at development of an efficient method as simple as hand calculation to estimate reduction of residual Stresses of a very thick welded joint by SR treatment. In the first report, an estimating method was developed for Relaxation tests, in uniaxial Stress state, at changing and constant temperatures because the Stress Relaxation Phenomenon may be considerably similar to that observed in the SR treatment of a joint. In the second report, the Stresses relaxed by SR treatment in a very thick welded joint were analyzed accurately by the finite element method based on thermal elastic-plastic creep theory. The characteristics of the changes of the welding residual Stresses in multiaxial Stress state were studied in detail for further development of the estimating method to SR treatment of a very thick welded joint, of which the Stress state and boundary condition are very complex. In the third report, the estimating equations in multiaxial Stress states were developed for the Stress Relaxation Phenomenon in the thick welded joints, based on the foregoing characteristics. In this report, the applicability of the simple estimating method is investigated for SR treatment of the thick welded joint, by comparing the estimated results with the accurate ones obtained by FEM.
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A Simple Estimating Method for Reduction of Welding Residual Stresses in Thick Welded Joint From Stress-Relief Annealing—Part III: Development of Estimating Equations for Multiaxial Stress State in Thick Welded Joint
Journal of Pressure Vessel Technology, 2001Co-Authors: Keiji NakachoAbstract:Stress-relief annealing (SR treatment) is often applied to relieve welding residual Stresses in the fabrication process of pressure vessels, etc. This study aims at development of an efficient method as simple as hand calculation to estimate reduction of residual Stresses of a very thick welded joint by SR treatment. In the first report, an estimating method was developed for Relaxation tests, in uniaxial Stress state, at changing and constant temperatures because the Stress Relaxation Phenomenon is considerably similar to that observed in the SR treatment of a joint. In the second report, the Stresses relaxed by SR treatment in a very thick welded joint were analyzed accurately by the finite element method based on thermal elastic-plastic creep theory. The characteristics of the changes of the welding residual Stresses in multiaxial Stress state were studied in detail for further development of the estimating method to SR treatment of a very thick welded joint, of which the Stress state and boundary condition are very complex. In this report, the estimating equations in multiaxial Stress states are developed for the Stress Relaxation Phenomenon in the thick welded joints, based on the foregoing characteristics.
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A Simple Estimating Method for Reduction of Welding Residual Stresses in Thick Welded Joint From Stress-Relief Annealing—Part II: The Characteristics of Reduction of Welding Residual Stresses in Very Thick Joints During SR Treatment
Journal of Pressure Vessel Technology, 1999Co-Authors: Keiji Nakacho, Y. UedaAbstract:Stress-reliefannealing (SR treatment) is often applied to relieve welding residual Stresses in the fabrication process of pressure vessels, etc. This study aims at development of an efficient method as simple as hand calculation to estimate reduction of residual Stresses of very thick welded joint by SR treatment. In the first report, an estimating method was developed for Relaxation tests, in uniaxial Stress state, at changing and constant temperatures because the Stress Relaxation Phenomenon is considerably similar to that observed in the SR treatment of a joint. In this report, the Stresses relaxed by SR treatment in a very thick welded joint are analyzed accurately by the finite element method based on thermal elastic-plastic-creep theory. The characteristics of the changes of the welding residual Stresses in multiaxial Stress state are studied in detail for further development of the estimating method to SR treatment of a very thick welded joint, of which the Stress state and boundary condition are very complex.
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A Simple Estimating Method for Reduction of Welding Residual Stresses in Thick Welded Joint From Stress-Relief Annealing—Part I: Development of the Analytical Method for Relaxation Tests and Its Applicability
Journal of Pressure Vessel Technology, 1996Co-Authors: Keiji Nakacho, Y. UedaAbstract:Stress-relief annealing (SR treatment) is often applied to relieve welding residual Stresses in the fabrication process of pressure vessels etc. This study aims at development of an efficient method as simple as hand calculation to estimate reduction of residual Stresses of very thick welded joint by SR treatment. In this first report, an estimating method is developed for Relaxation tests, in uniaxial Stress state, at changing and constant temperatures because the Stress Relaxation Phenomenon is very similar to that observed in the SR treatment of a joint. Using the various relations between Stress and strains in the Relaxation tests, estimating equations are formulated in order to simply calculate the change of the Stress. The results obtained by applying the equations are compared with the highly accurate analytical result based on the finite element method. Both results show such a good coincidence that the appropriateness of the adopted method is confirmed. In the next report, this method is extended to SR treatment of a very thick welded joint, of which the Stress state and boundary condition are very complex.
M. Jeannin - One of the best experts on this subject based on the ideXlab platform.
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High temperature oxidation of Ni70Cr30 alloy: Determination of oxidation kinetics and Stress evolution in chromia layers by Raman spectroscopy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: M. Kemdehoundja, J.f. Dinhut, Jean-luc Grosseau-poussard, M. JeanninAbstract:Abstract In this work, the oxidation of Ni70Cr30 alloy has been produced at a temperature of 900 °C in air. The parabolic behaviour of oxidation was established ex situ and the corresponding kinetic constant was deduced. Microscopic observations have shown that chromia grain size does not exceed 1 μm. Raman spectroscopy was used to determine Stresses in chromia (Cr2O3) layers. Stresses are found to be compressive and increase with the chromia thickness before reaching a “plateau” at −2.9 GPa. The Stress Relaxation Phenomenon discussed here takes into account theoretical modelling that can be found in literature.
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High temperature oxidation of Ni70Cr30 alloy: Determination of oxidation kinetics and Stress evolution in chromia layers by Raman spectroscopy
Materials Science and Engineering: A, 2006Co-Authors: M. Kemdehoundja, J.f. Dinhut, Jean-luc Grosseau-poussard, M. JeanninAbstract:In this work, the oxidation of Ni70Cr30 alloy has been produced at a temperature of 900 °C in air. The parabolic behaviour of oxidation was established ex situ and the corresponding kinetic constant was deduced. Microscopic observations have shown that chromia grain size does not exceed 1 μm. Raman spectroscopy was used to determine Stresses in chromia (Cr2O3) layers. Stresses are found to be compressive and increase with the chromia thickness before reaching a "plateau" at -2.9 GPa. The Stress Relaxation Phenomenon discussed here takes into account theoretical modelling that can be found in literature. © 2006 Elsevier B.V. All rights reserved.
Frederic Barlat - One of the best experts on this subject based on the ideXlab platform.
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Stress Relaxation and its effect on tensile deformation of steels
Materials & Design, 2013Co-Authors: Krishnaswamy Hariharan, Omid Majidi, Frederic BarlatAbstract:Abstract The tensile deformation of metallic materials, when interrupted without unloading, exhibit Relaxation of Stress. The Stress Relaxation Phenomenon can alter the mechanical behavior of the materials. Stress Relaxation Phenomenon during tensile test is studied in three steel grades with different microstructures. The influence of Stress Relaxation on uniform elongation has not been reported before. The uniform elongation varies with strain at which material relaxes and is found to increase upto 3.5%. Contradicting with the published results, the Stress drop during Stress Relaxation varies with strain and the possible reasons are explained. The Stress drop during Relaxation is governed by strain hardening mechanism in low carbon steel and strain aging mechanism due to martensite in dual phase (DP) and transformation induced plasticity (TRIP) steels.
Y. Ueda - One of the best experts on this subject based on the ideXlab platform.
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A Simple Estimating Method for Reduction of Welding Residual Stresses in Thick Welded Joint From Stress-Relief Annealing—Part II: The Characteristics of Reduction of Welding Residual Stresses in Very Thick Joints During SR Treatment
Journal of Pressure Vessel Technology, 1999Co-Authors: Keiji Nakacho, Y. UedaAbstract:Stress-reliefannealing (SR treatment) is often applied to relieve welding residual Stresses in the fabrication process of pressure vessels, etc. This study aims at development of an efficient method as simple as hand calculation to estimate reduction of residual Stresses of very thick welded joint by SR treatment. In the first report, an estimating method was developed for Relaxation tests, in uniaxial Stress state, at changing and constant temperatures because the Stress Relaxation Phenomenon is considerably similar to that observed in the SR treatment of a joint. In this report, the Stresses relaxed by SR treatment in a very thick welded joint are analyzed accurately by the finite element method based on thermal elastic-plastic-creep theory. The characteristics of the changes of the welding residual Stresses in multiaxial Stress state are studied in detail for further development of the estimating method to SR treatment of a very thick welded joint, of which the Stress state and boundary condition are very complex.
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A Simple Estimating Method for Reduction of Welding Residual Stresses in Thick Welded Joint From Stress-Relief Annealing—Part I: Development of the Analytical Method for Relaxation Tests and Its Applicability
Journal of Pressure Vessel Technology, 1996Co-Authors: Keiji Nakacho, Y. UedaAbstract:Stress-relief annealing (SR treatment) is often applied to relieve welding residual Stresses in the fabrication process of pressure vessels etc. This study aims at development of an efficient method as simple as hand calculation to estimate reduction of residual Stresses of very thick welded joint by SR treatment. In this first report, an estimating method is developed for Relaxation tests, in uniaxial Stress state, at changing and constant temperatures because the Stress Relaxation Phenomenon is very similar to that observed in the SR treatment of a joint. Using the various relations between Stress and strains in the Relaxation tests, estimating equations are formulated in order to simply calculate the change of the Stress. The results obtained by applying the equations are compared with the highly accurate analytical result based on the finite element method. Both results show such a good coincidence that the appropriateness of the adopted method is confirmed. In the next report, this method is extended to SR treatment of a very thick welded joint, of which the Stress state and boundary condition are very complex.
Keh-chih Hwang - One of the best experts on this subject based on the ideXlab platform.
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Oxidation Stress evolution and Relaxation of oxide film/metal substrate system
Journal of Applied Physics, 2012Co-Authors: Xuelin Dong, Xue Feng, Keh-chih HwangAbstract:Stresses in the oxide film/metal substrate system are crucial to the reliability of the system at high temperature. Two models for predicting the Stress evolution during isothermal oxidation are proposed. The deformation of the system is depicted by the curvature for single surface oxidation. The creep strain of the oxide and metal, and the lateral growth strain of the oxide are considered. The proposed models are compared with the experimental results in literature, which demonstrates that the elastic model only considering for elastic strain gives an overestimated Stress in magnitude, but the creep model is consistent with the experimental data and captures the Stress Relaxation Phenomenon during oxidation. The effects of the parameter for the lateral growth strain rate are also analyzed.