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

The Influence of Multiaxial Stress Relaxation on Component Creep Damage Accumulation

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Nayden Matev ◽  
Robert A. Ainsworth ◽  
Meini Su ◽  
Mark Stevens ◽  
Alan Jappy
Keyword(s):  
Stress State ◽  
Stress Drop ◽  
Damage Accumulation ◽  
Stress Ratio ◽  
Equivalent Stress ◽  
Creep Damage ◽  
Biaxial Stress ◽  
Multiaxial Stress ◽  
Multiaxial Stress State

Abstract Unless inelastic analysis is used, high temperature codes base creep relaxation on the start-of-dwell equivalent stress, which relaxes according to a uniaxial creep law. Elastic follow-up is also included. This approach only evaluates equivalent stress and creep strain rate and the multiaxial stress state is assumed to remain at its initial value as the stress relaxes. Codes suggest that the stress drop is limited to a fraction (typically 20%) of the initial equivalent stress to ensure this assumption does not introduce significant inaccuracies. This article provides a numerical examination of creep relaxation of a cruciform plate subjected to displacement-controlled biaxial loading, with the aim to provide clarification of any required constraint on stress drop. The initial biaxial stress ratio, the plate geometry and the power in a power–law creep model are varied, leading to variations in the elastic follow-up describing the creep relaxation. The biaxial stress ratio is generally found to change with relaxation and a multiaxial ductility approach is used to evaluate the associated creep damage accumulation. This is compared with the damage estimated assuming relaxation is controlled by the equivalent stress with no change in multiaxial stress state. For biaxial plane stress with one principal stress initially being compressive and one tensile, it is found that significant equivalent stress drops (about 40% of the initial stress) can be allowed without the simplified equivalent stress approach becoming inaccurate. More care is required for tensile–tensile stress biaxiality where multiaxial stress changes depend on the initial stress biaxiality and the degree of elastic follow-up. The results will be used to propose improved guidance for simplified inelastic calculations.

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.

Study on Creep Behaviors of T92 Steel under Multiaxial Stress State

2013 ◽  
Vol 860-863 ◽  
pp. 774-779
Author(s):  
Xue Ping Mao ◽  
Yang Yu ◽  
Chao Li ◽  
Sai Dong Huang ◽  
Hong Xu ◽  
...  
Keyword(s):  
Stress State ◽  
Rupture Life ◽  
Creep Damage ◽  
Creep Rupture ◽  
Failure Behavior ◽  
Multiaxial Stress ◽  
Creep Tests ◽  
Creep Ductility ◽  
Notched Specimen ◽  
Multiaxial Stress State

Creep tests for smooth specimens and notched specimens of T92 steel were carried out to study the effect of multiaxial stress state on creep rupture behaviors at 650°C. Creep rupture life was estimated by representative stress at multiaxial state of stress, the failure behavior of multiaxial creep was analyzed, and Kachanov creep damage formula was used to analyze the experimental data. The results show that the notch strengthens rupture life, multiaxial rupture behavior is controlled by mixed parameters, the creep ductility of the smooth and notched specimen decreases with rupture time, and damage factors of the smooth specimen and notched specimen are similar according to Kachanov formula.

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.

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.

Reliability Evaluation of Structural Ceramics Under Multiaxial Stress State

1998 ◽  
Author(s):  
Takashi Ono ◽  
Masaki Kaji ◽  
Michiaki Nishimura
Keyword(s):  
Experimental Data ◽  
Distribution Function ◽  
Stress State ◽  
Fracture Probability ◽  
Test Method ◽  
Structural Ceramics ◽  
Multiaxial Stress ◽  
Fatigue Lifetime ◽  
Empirical Parameter ◽  
Multiaxial Stress State

Strength and fatigue lifetime of structural ceramics under multiaxial stress state have been estimated and compared with experimental data. Biaxial strength tests were done by an anticlastic bending test method at room temperature. Biaxial fatigue tests were done by anticlastic bending and also ring-on-ring test method at 1200°C in air. Fracture probability and lifetime were predicted on the basis of a Weibull multiaxial distribution function and subcritical crack growth, using the results of stress analyses by the finite element method. Modified maximum hoop stress theory including an empirical parameter, T, was applied to the equivalent normal stress in the multiaxial distribution function. The empirical parameter T represents a shear stress sensitivity to mixed-mode fracture due to a grain interlocking effect. It has been confirmed that the predicted fracture probability and the fatigue lifetime agrees well with the experimental data if grain interlocking effects are taking into account.

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