scholarly journals PWSCC Growth Assessment Model Considering Stress Triaxiality Factor for Primary Alloy 600 Components

2016 ◽  
Vol 48 (4) ◽  
pp. 1036-1046 ◽  
Author(s):  
Jong-Sung Kim ◽  
Ji-Soo Kim ◽  
Jun-Young Jeon ◽  
Yun-Jae Kim
Keyword(s):  
Stress Triaxiality ◽  
Assessment Model ◽  
Alloy 600 ◽  
Growth Assessment ◽  
Triaxiality Factor

Notch Effects, Stress State, and Ductility

1978 ◽  
Vol 100 (4) ◽  
pp. 348-355 ◽  
Author(s):  
Alice M. Agogino
Keyword(s):  
Stress State ◽  
Stress Triaxiality ◽  
Review Of The Literature ◽  
Simple Criterion ◽  
Short Term ◽  
Notched Specimens ◽  
Tension Tests ◽  
Notch Geometry ◽  
Limiting Value ◽  
Triaxiality Factor

A review of the literature on testing of notched specimens is provided with emphasis on short-term notched bar tension tests. The effects of notch geometry, stress state, and smooth-bar tensile properties on notched ductility, notch sensitivity, and mode of fracture are discussed. For design against failure due to notch weakening, a simple criterion based on a limiting value of notched ductility is proposed. Notched ductility for the metals considered in this study, can be approximated by the reduction in and from a smooth tension test divided by a tensile stress triaxiality factor that is proportional to the ratio of hydrostatic to octahedral shearing stresses associated with the notch.

Prediction of Creep Void Growth in Heat-Affected Zone of High Chromium Steel Weldments Considering Multiaxial Stress State

2012 ◽  
Author(s):  
Eiji Murakami ◽  
Masamitsu Hashimoto ◽  
Seiji Kikuhara
Keyword(s):  
Stress State ◽  
Heat Affected Zone ◽  
Void Growth ◽  
Stress Triaxiality ◽  
Chromium Steel ◽  
Growth Behavior ◽  
High Chromium ◽  
Multiaxial Stress State ◽  
The Relationship ◽  
Triaxiality Factor

This paper deals with a method for predicting creep void growth in heat-affected zone (HAZ) of high chromium steel weldments. The method has been proposed by authors based on the relationship between creep void density increasing rate and multiaxial stress state. In this study, internal pressure creep tests of ASME grade 91 (9Cr-1Mo-Nb-V) tubes with longitudinal weldments subjected to several internal pressures have been conducted to reveal creep void growth behavior in HAZ. In addition, finite element creep analyses of the specimens at different creep strain rates in base metal, weld metal and HAZ have been carried out to investigate distribution of stresses and stress triaxiality factor in HAZ. A comparison between stress distributions and void distributions revealed that stress triaxiality factor predominantly affects growth behavior of creep voids. From the result, the relationship between creep void density increasing rate and the parameter as a function of principal stress and triaxiality factor was established. It was found that there is a proportional relationship between creep void density increasing rate and the parameter to represent stress multiaxiality on the logarithmic graph. To verify proposed prediction method, the method was applied to the internal pressure creep test specimens at different experimental conditions. As a result, the predicted void distribution and void density increasing rates were in good agreement with experimental results.

Simplified Prediction of Creep Void Density in Heat-Affected Zone of Grade 122 Steel Considering Multiaxial Stress State

2013 ◽  
Author(s):  
Eiji Murakami ◽  
Masamitsu Hashimoto ◽  
Seiji Kikuhara
Keyword(s):  
Stress State ◽  
Void Growth ◽  
Stress Triaxiality ◽  
Prediction Method ◽  
Growth Behavior ◽  
Multiaxial Stress State ◽  
Grade 91 ◽  
The Relationship ◽  
Tubular Specimens ◽  
Triaxiality Factor

This paper deals with a simplified method for approximately predicting creep void growth in heat-affected zone (HAZ) of ASME grade 122 (11Cr-2W-0.4Mo-Cu-Nb-V) steel weldments. Authors have proposed a simplified prediction method based on the relationship between creep void density increasing rate and multiaxial stress state. This method has been applied to prediction of creep void growth behavior for grade 91 (9Cr-1Mo-Nb-V) tubular specimens with longitudinal weldments. In this study, the method has been also applied to grade 122 steel to clarify the applicability of the method. Internal pressure creep tests of grade 122 tubular specimens with longitudinal weldments subjected to several internal pressures have been conducted to reveal creep void growth behavior in HAZ. In addition, finite element creep analyses for the specimens at different creep strain rates in base metal, weld metal and HAZ have been carried out to investigate distribution of stresses and stress triaxiality factor in HAZ. A comparison between stress distributions and creep void distributions revealed that stress triaxiality factor affects growth behavior of creep voids. From the result, the relationship between creep void density increasing rate and the parameter as a function of principal stress and triaxiality factor was established. It was found that the slope of this relationship for 122 steel has a tendency to be slightly small compared with grade 91 steel. To demonstrate the applicability of the proposed simplified prediction method, the method was applied to the internal pressure creep test specimens at different experimental conditions. As a result, the predicted void distribution and void density increasing rates for grade 122 steel were in good agreement with the experimental results.

Ductile Crack Initiation Behavior of Prestrained Steels

2011 ◽  
Author(s):  
Takehisa Yamada ◽  
Yoichi Yamashita
Keyword(s):  
Crack Initiation ◽  
Void Nucleation ◽  
Equivalent Plastic Strain ◽  
Stress Triaxiality ◽  
Ductile Crack ◽  
Round Bar ◽  
Point Bend ◽  
Materials Used ◽  
Cracked Specimens ◽  
Triaxiality Factor

Ductile crack initiation behaviors were experimentally and analytically investigated using compressively prestrained notched round bar specimen (lower stress triaxiality condition) and four point bend specimen (higher stress triaxiality condition). The materials used were SM400B and HT780. It was observed that ductile crack initiation of notched round bar specimen occurred at the center of specimen and was caused by coalescence of micro voids. Ductile limit curves, which are the relationships between equivalent plastic strain and stress triaxiality factor at ductile crack initiation, were obtained using FE-analyses and experimental results. Ductile crack initiation of four point bend specimens as cracked specimens could be evaluated using ductile crack initiation limit curves obtained from notched round bar specimens if the positions of void nucleation at crack tip are properly considered. It has been found that ductile crack initiation limits can be evaluated using ductile limit curves under both low and high constraint conditions (stress triaxiality conditions.

scholarly journals Effect of Stress Triaxiality on the Strain Concentration Factor

2019 ◽  
Vol 8 (4) ◽  
pp. 3468-3474
Keyword(s):  
Stress State ◽  
Concentration Factor ◽  
Notch Root ◽  
Stress Triaxiality ◽  
Critical Section ◽  
Triaxial Stress ◽  
Triaxial Stress State ◽  
Strain Concentration ◽  
Machine Element ◽  
Triaxiality Factor

Axisymmetric machine element with irregularities such as notches encountered with effects of stress triaxiality on the strain concentration factor (SNCF) at the reduced section. The effect of notch geometries on the triaxial stress state development in the critical section of a notched cylindrical bar is studied here using FEM. In addition, the effect of triaxial stress state (TSS) on the SNCF is evaluated. To this end, a notched cylindrical bars with notch depths from extremely deep notch (do/Do = 0.2) shallow notch (do/Do = 0.95) has been employed. The results show that the notches introduce a TSS at the critical section, which strongly affected by the notch depth as well as the notch radii. In this paper, a new concentration factor is introduced as the ratio of the stress triaxiality factor at the notch root (TFNR) to the average triaxiality on the critical section (), i.e. the triaxiality concentration factor KTF. The numerical results reveal that the variation of the average triaxiality factor with total strain shows the same trend as that of the SNCF. The variation of the elastic values of TFCN, , , and SNCF with do/Do and show that the minimum TFNR leads to the maximum elastic SNCF. It is prominent that elastic TFNR is less that elastic TFCN for 0.2 ≤ do/Do ≤ 0.85, while it is greater for shallow notches. The current results indicate a strong compatibility between the newly defined triaxiality concentration factor and the SNCF up to general yielding.

Effects of thermal aging and stress triaxiality on PWSCC initiation susceptibility of nickel-based Alloy 600

2016 ◽  
Vol 30 (10) ◽  
pp. 4403-4406
Author(s):  
Seung Chang Yoo ◽  
Kyoung Joon Choi ◽  
Taeho Kim ◽  
Ji Hyun Kim
Keyword(s):  
Thermal Aging ◽  
Stress Triaxiality ◽  
Alloy 600 ◽  
Nickel Based Alloy

Creep Damage Evaluation for Fine Grained HAZ of Mod. 9Cr Steels Under Multi-Axial Stress Conditions

2013 ◽  
Author(s):  
Kimiaki Yoshida ◽  
Masataka Yatomi ◽  
Masaaki Tabuchi ◽  
Ken-ichi Kobayashi
Keyword(s):  
Axial Stress ◽  
Stress Triaxiality ◽  
Creep Damage ◽  
Creep Rupture ◽  
Stress Conditions ◽  
Damage Evaluation ◽  
Metallographic Examination ◽  
Fine Grained ◽  
Notched Specimens ◽  
Triaxiality Factor

This study is concerned with the creep damage evaluation for the fine grained heat affected zone (HAZ) of modified 9Cr steels under multi-axial stress conditions. Circumferentially notched bar creep rupture and interrupted tests have been conducted on the simulated HAZ specimens of modified 9Cr Steels. A metallographic examination has been carried out to quantify creep damage accumulation in the specimens. It has been found from void observation that growth of creep void correlates with maximum principle stress and stress triaxiality factor. Finite element predictions based on ductility exhaustion approach have also been performed to predict the creep rupture time and creep damage in notched specimens. It has been concluded that a ductility exhaustion approach with empirical model provides reasonable life predictability almost in a scatter band of a factor of 2.

New Analytical Approach to Predict Creep Void Growth in Heat-Affected Zone of High Cr Steel Weldments

2011 ◽  
Author(s):  
Eiji Murakami ◽  
Takeshi Iwamoto ◽  
Toshiyuki Sawa
Keyword(s):  
Finite Element ◽  
Heat Affected Zone ◽  
Void Growth ◽  
Analytical Approach ◽  
Axial Stress ◽  
Stress Triaxiality ◽  
Growth Behavior ◽  
Damage Level ◽  
The Relationship ◽  
Triaxiality Factor

This paper proposes a new analytical approach to predict creep void growth and remaining creep lifetime in a heat-affected zone (HAZ) of high Cr steel weldments. Concept of the new approach is based on a relationship between creep void growth rate and a parameter to represent multi-axial stress state obtained by finite element analysis. In this study, creep tests of ASME grade 91 (9Cr-1Mo-Nb-V) and grade 122 (11Cr-2W-0.4Mo-Cu-Nb-V) tubes with longitudinal weldments subjected to various internal pressures have been conducted to reveal creep void growth behavior in HAZ. Some specimens were intentionally interrupted before leakage at a damage level from 40 to 70% for clarification of void growth behavior at intermediate damage level. In addition, finite element creep analyses of the specimens at different creep strain rates in base metal, weld metal and HAZ have been carried out to investigate distribution of stress and stress triaxiality factor in HAZ. A comparison between stress distributions and void distributions revealed that stress triaxiality factor predominantly affects growth behavior of creep voids. From the result, the relationship between creep void growth rates and the parameter as a function of principal stress and triaxiality factor was established. Based on the relationship, a new prediction method was proposed. To verify proposed approach, the new method was applied to the elbow pipe with longitudinal weldment. As a result, predicted creep void growth in HAZ showed a good agreement with the results from diffusion simulation reported by literature. Therefore, the results demonstrated that the proposed approach is applicable to predict void distribution and remaining creep lifetime in the HAZ of high Cr steel weldments.

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