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

2002 ◽  
Vol 124 (2) ◽  
pp. 207-214 ◽  
Author(s):  
Keiji Nakacho
Keyword(s):  
Stress State ◽  
Stress Relaxation ◽  
Residual Stresses ◽  
Welded Joint ◽  
Uniaxial Stress ◽  
Stress Relief ◽  
Pressure Vessels ◽  
Relaxation Phenomenon ◽  
Multiaxial Stress ◽  
Creep Theory

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.

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

2001 ◽  
Vol 124 (1) ◽  
pp. 14-21 ◽  
Author(s):  
Keiji Nakacho
Keyword(s):  
Stress State ◽  
Stress Relaxation ◽  
Residual Stresses ◽  
Welded Joint ◽  
Estimating Equations ◽  
Stress Relief ◽  
Pressure Vessels ◽  
Relaxation Phenomenon ◽  
Multiaxial Stress ◽  
Multiaxial Stress State

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.

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

1999 ◽  
Vol 121 (1) ◽  
pp. 11-16 ◽  
Author(s):  
K. Nakacho ◽  
Y. Ueda
Keyword(s):  
Stress State ◽  
Residual Stresses ◽  
Welded Joint ◽  
Uniaxial Stress ◽  
Stress Relief ◽  
Pressure Vessels ◽  
The Finite Element Method ◽  
Creep Theory ◽  
Multiaxial Stress State ◽  
Further Development

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 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.

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

1996 ◽  
Vol 118 (3) ◽  
pp. 343-350 ◽  
Author(s):  
K. Nakacho ◽  
Y. Ueda
Keyword(s):  
Stress State ◽  
Residual Stresses ◽  
Welded Joint ◽  
Uniaxial Stress ◽  
Stress Relief ◽  
Pressure Vessels ◽  
The Finite Element Method ◽  
Hand Calculation ◽  
Analytical Result ◽  
Good Coincidence

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.

Analysis on Fracture Morphology and Microstructure of T92 Steel after High Temperature Multiaxial Creep

2013 ◽  
Vol 860-863 ◽  
pp. 967-971
Author(s):  
Xue Ping Mao ◽  
Xiao Wang ◽  
Sai Dong Huang ◽  
Chao Li ◽  
Hong Xu ◽  
...  
Keyword(s):  
High Temperature ◽  
Stress State ◽  
Standard Specimen ◽  
Uniaxial Stress ◽  
Fracture Morphology ◽  
Multiaxial Stress ◽  
Creep Life ◽  
Creep Tests ◽  
Multiaxial Stress State ◽  
Multiaxial Creep

The high temperature creep tests of standard specimen and double U-type notch specimen of T92 steel were carried out under different stresses at 650 °C. Then optical microscopy and scanning electron microscopy were used to observe the fracture morphology and microstructure. The results show that the multiaxial stress state leads to the creep fracture cracking initiation in notch. Under multiaxial stress state, the failure mode of T92 steel is transgranular and dimple plastic fracture, and is more obvious with the increase of creep life. Compared with under uniaxial stress state, the precipitates under multiaxial stress state are larger in size and quantity, and are much coarser.

Effect of multiaxial stress state on creep damage in ASME T92 welded joint

2020 ◽  
Vol 43 (5) ◽  
pp. 907-918
Author(s):  
Xiao Wang ◽  
Xue Wang ◽  
Chuang Wang ◽  
Ya‐Lin Zhang ◽  
Qiao‐Sheng Huang
Keyword(s):  
Stress State ◽  
Welded Joint ◽  
Creep Damage ◽  
Multiaxial Stress ◽  
Multiaxial Stress State

scholarly journals Model Of Relaxation Of Residual Stresses In Hot-Rolled Strips

2015 ◽  
Vol 60 (3) ◽  
pp. 1935-1940 ◽  
Author(s):  
A. Milenin ◽  
R. Kuziak ◽  
V. Pidvysots'kyy ◽  
P. Kustra ◽  
Sz. Witek ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Residual Stresses ◽  
Thermal Stresses ◽  
Plastic Material ◽  
Material Model ◽  
Creep Model ◽  
Creep Theory ◽  
Elastic Plastic ◽  
Elastic Plastic Material ◽  
Hot Rolled

Abstract Residual stresses in hot-rolled strips are of practical importance when the laser cutting of these strip is applied. The factors influencing the residual stresses include the non uniform distribution of elastic-plastic deformations, phase transformation occurring during cooling and stress relaxation during rolling and cooling. The latter factor, despite its significant effect on the residual stress, is scarcely considered in the scientific literature. The goal of the present study was development of a model of residual stresses in hot-rolled strips based on the elastic-plastic material model, taking into account the stress relaxation. Residual stresses in hot-rolled strips were evaluated using the FEM model for cooling in the laminar cooling line and in the coil. Relaxation of thermal stresses was considered based on the creep theory. Coefficients of elastic-plastic material model and of the creep model for steels S235 and S355 were obtained from the experiments performed on the Gleeble 3800 simulator for the temperatures 35-1100°C. Experiments composed small tensile deformations of the sample (0.01-0.02) and subsequent shutter speed without removing the load. Model of the thermal deformation during cooling was obtained on the basis of the dilatometric tests at cooling rates of 0.057°C/s to 60°C/s. Physical simulations of the cooling process were performed to validate the model. Samples were fixed in the simulator Gleeble 3800, then heated to the temperature of 1200°C and cooled to the room temperature at a rate of 1-50°C/s. Changes of stresses were recorded. Good agreement between calculated and experimental values of stresses was observed. However, due to neglecting the effect of stress relaxation the stress at high temperatures was overestimated. Due to the change of their stress sign during the unloading process the resulting residual stresses were underestimated. Simulation of residual stresses in rolling and cooling were performed on the basis of the developed model. It was shown that the effect of stress relaxation and phase transformations on the distribution of residual stresses in strips is essential and neglecting these factors could lead to an underestimation of residual stresses.

Fatigue Life Assessment of Fillet Welded Joint Considering the Relaxation and Redistribution of Residual Stresses

2004 ◽  
Author(s):  
Chang Doo Jang ◽  
Ha Cheol Song ◽  
Young Chun Jo
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Stress Relaxation ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Welded Joint ◽  
Life Assessment ◽  
Ship Structure ◽  
Fatigue Life Assessment ◽  
Plastic Analysis

This paper presents the fatigue life assessment procedure for the welded joint of ship structure. Test model is a boxing fillet specimen, the idealized welded joint model of longitudinal and transverse members in ship structure. Fatigue test was executed according to the 14-points S-N method of JSME, and experimental data were presented in the S-N curve based on HSS (Hot Spot Stress) approach. To define the fatigue life of crack initiation and crack propagation, S-N data for each length of crack were appraised. In this study, the new FE analysis algorithms for the estimation of residual stress relaxation due to external load and residual stress redistribution due to crack propagation were proposed to assess the effect of residual stresses on crack growth precisely. Initial welding residual stress field was obtained by thermal elasto-plastic analysis considering temperature dependent material properties, and the amount of residual stress relaxation and redistribution were assessed by subsequent elasto-plastic analysis. In the analysis of crack propagation, the SIF (Stress Intensity Factor) range was evaluated by 1/4-point displacement extrapolation method, and the effect of welding residual stresses on fatigue behaviors was considered by introducing the effective SIF concept. The test results of crack propagations were compared with the predicted data from the analysis.

Analysis on Fracture Mechanism of T92 Steel under High Temperature Multiaxial Creep

2014 ◽  
Vol 941-944 ◽  
pp. 1423-1427
Author(s):  
Hong Xu ◽  
Jun Yuan ◽  
Jing Liu ◽  
Sai Dong Huang ◽  
Chao Li ◽  
...  
Keyword(s):  
High Temperature ◽  
Stress State ◽  
Uniaxial Stress ◽  
Fracture Morphology ◽  
Second Phase ◽  
Strengthening Effect ◽  
Multiaxial Stress ◽  
Creep Tests ◽  
Multiaxial Stress State ◽  
Multiaxial Creep

The high temperature creep tests of standard specimen and double U-notched specimen of T92 steel were carried out under different stresses at 600°C and 650 °C. Then scanning electron microscopy was used to observe the fracture morphology. The results show that the notch weakens plasticity, and weakening with the notch acuity. Under multiaxial stress state, the failure mode of T92 steel gradually transfers from ductile dimple to brittle quasi-cleavage fracture. Compared with uniaxial stress state, the dimples under multiaxial stress state are smaller and shallower, within lots of carbides and second phase particles. The notch slows the connection, growth and gather of microvoids, and exhibits notch strengthening effect.

The effect of differential thermal expansion on residual stresses in a welded connection

1976 ◽  
Vol 11 (1) ◽  
pp. 56-61
Author(s):  
E Procter ◽  
E M Beaney
Keyword(s):  
Residual Stress ◽  
Thermal Expansion ◽  
Residual Stresses ◽  
Welded Joint ◽  
Stress Relief ◽  
Apparent Strain ◽  
Differential Thermal Expansion ◽  
Strain Gauge Measurements ◽  
Welded Connection ◽  
Differential Expansion

Two tests were conducted on a welded joint between a forging and a pipe adaptor, to investigate the effect of differential thermal expansion in the various parts of the joint, on the residual stress. The first test was carried out with the weld in the approved manufacturing stress relieved condition. The second test was carried out following normalizing and extended stress relief heat treatments. Strain gauge measurements were made on the heat affected zones and at various positions across the weld as the forging was heated and cooled through approximately 250° C. The apparent strain outputs of the gauges used at each location were determined from gauges attached to ‘stress free islands’ machined in the weld at the required postions Since the tests could only be carried out over a 250° C range the results were linearly extrapolated to cover the range of stress relief temperatures. It is shown that differential expansion can have significant effects on residual weld stresses as the structures are temperature cycled.

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