A Simplified Approach to the Effect of Specimen Size on the Creep Rupture of Cross Weld Samples

1982 ◽  
Vol 104 (1) ◽  
pp. 36-40 ◽  
Author(s):  
J. A. Williams
Keyword(s):  
Failure Time ◽  
Stress Rupture ◽  
Limit Load ◽  
Parent Material ◽  
Creep Rupture ◽  
Creep Data ◽  
Simplified Approach ◽  
Reference Stress ◽  
Failure Location ◽  
Stress Rupture Testing

Various methods are available to assess the performance of welded joints under creep conditions. One approach uses the creep rupture testing of cross weld geometries in uniaxial tension. This paper examines an idealized model of a cross weld specimen where the weld metal is weaker than the parent material. The analysis, which is developed from published work on brazed and soldered joints, characterizes the limit load of the specimen as a function of the weld thickness:specimen diameter ratio and the yield strengths of both materials. The limit load is then used to define a creep reference stress which may be applied to uniaxial data. The predictions of the failure location and failure time are compared with cross weld creep data generated within the CEGB as no suitable data were found in the general literature. Finally, the model is used to postulate a size or weld thickness:specimen diameter effect on stress rupture testing of cross weld geometries.

Multiaxial Stress Rupture Testing and Compendium of Data for Creep Resisting Steels

1982 ◽  
Vol 104 (4) ◽  
pp. 291-296 ◽  
Author(s):  
R. J. Browne ◽  
D. Lonsdale ◽  
P. E. J. Flewitt
Keyword(s):  
Stress Rupture ◽  
Creep Rupture ◽  
Estimation Methods ◽  
Multiaxial Stress ◽  
Life Estimation ◽  
Uniaxial Creep ◽  
Rupture Data ◽  
Stress Rupture Testing ◽  
Present Life ◽  
Rupture Criterion

Recently, there has been an increasing need for more accurate methods of predicting the life of components operating in the creep range. Although many such components are invariably subject to multiaxial stress systems, present life estimation methods utilize available uniaxial creep rupture data via a representative stress for the component. This stress is usually empirically derived and in many cases leads to undue conservatism in life estimates because no account is taken of the creep and rupture response of the material to multiaxial stresses. This paper reviews the various multiaxial stress rupture test techniques which have been employed to determine the multiaxial stress rupture criterion. The multiaxial stress rupture data available in the literature for some commonly used creep resisting steels are compiled and discussed.

Prediction of Long Term Stress Rupture Data for 2124

2006 ◽  
Vol 519-521 ◽  
pp. 1041-1046 ◽  
Author(s):  
Brian Wilshire ◽  
H. Burt ◽  
N.P. Lavery
Keyword(s):  
Q Methodology ◽  
Fracture Behavior ◽  
Stress Rupture ◽  
Creep Data ◽  
Short Term ◽  
Rupture Data ◽  
Term Creep ◽  
Term Data ◽  
Short Term Creep

The standard power law approaches widely used to describe creep and creep fracture behavior have not led to theories capable of predicting long-term data. Similarly, traditional parametric methods for property rationalization also have limited predictive capabilities. In contrast, quantifying the shapes of short-term creep curves using the q methodology introduces several physically-meaningful procedures for creep data rationalization and prediction, which allow straightforward estimation of the 100,000 hour stress rupture values for the aluminum alloy, 2124.

J-Integral Analysis of Surface Cracks in Round Bars under Bending Moments

2011 ◽  
Vol 52-54 ◽  
pp. 43-48 ◽  
Author(s):  
Al Emran Ismail ◽  
Ahmad Kamal Ariffin ◽  
Shahrum Abdullah ◽  
Mariyam Jameelah Ghazali ◽  
Ruslizam Daud
Keyword(s):  
Finite Element ◽  
Crack Depth ◽  
Crack Tip ◽  
Bending Moment ◽  
Limit Load ◽  
Fe Model ◽  
Surface Cracks ◽  
Element Analysis ◽  
Reference Stress ◽  
Proposed Model

This paper presents a non-linear numerical investigation of surface cracks in round bars under bending moment by using ANSYS finite element analysis (FEA). Due to the symmetrical analysis, only quarter finite element (FE) model was constructed and special attention was given at the crack tip of the cracks. The surface cracks were characterized by the dimensionless crack aspect ratio, a/b = 0.6, 0.8, 1.0 and 1.2, while the dimensionless relative crack depth, a/D = 0.1, 0.2 and 0.3. The square-root singularity of stresses and strains was modeled by shifting the mid-point nodes to the quarter-point locations close to the crack tip. The proposed model was validated with the existing model before any further analysis. The elastic-plastic analysis under remotely applied bending moment was assumed to follow the Ramberg-Osgood relation with n = 5 and 10. J values were determined for all positions along the crack front and then, the limit load was predicted using the J values obtained from FEA through the reference stress method.

High-Temperature Failures

2012 ◽  
pp. 415-459
Keyword(s):  
High Temperature ◽  
Stress Rupture ◽  
Creep Life Prediction ◽  
Creep Curves ◽  
Creep Fatigue ◽  
Temperature Fracture ◽  
Underlying Mechanisms ◽  
Thermomechanical Damage ◽  
Stress Rupture Testing ◽  
Related Design

Abstract This chapter compares and contrasts the high-temperature behaviors of metals and composites. It describes the use of creep curves and stress-rupture testing along with the underlying mechanisms in creep deformation and elevated-temperature fracture. It also discusses creep-life prediction and related design methods and some of the factors involved in high-temperature fatigue, including creep-fatigue interaction and thermomechanical damage.

Reliability Assessment of Piping With Cracks Using Advanced First-Order Second-Moment Method

2009 ◽  
Author(s):  
Shinji Yoshida ◽  
Hideo Machida
Keyword(s):  
Safety Factor ◽  
Reliability Assessment ◽  
Limit Load ◽  
Service Level ◽  
Assessment Method ◽  
J Integral ◽  
Reference Stress ◽  
First Order Second Moment ◽  
Fracture Assessment ◽  
Second Moment Method

This paper describes applicability of the 2 parameter assessment method using a reference stress method from the viewpoint of reliability. The applicability of the reference stress method was examined comparing both the GE-EPRI method. As a result, J-integral and limit load at the time of fracture evaluated by the reference stress method is almost equivalent to that by the GE-EPRI method. Furthermore, the partial safety factor (PSF) evaluated by reliability assessment has little difference between two methods, and the required safety factor is enveloped by the safety factor for Service Level-A and B defined in fitness for service (FFS) codes. These results show that of the reference stress method is applicable for J-integral calculation in fracture assessment.

Creep–rupture model of aluminum alloys: Cohesive zone approach

2014 ◽  
Vol 229 (8) ◽  
pp. 1343-1347 ◽  
Author(s):  
Kyungmok Kim
Keyword(s):  
Aluminum Alloys ◽  
Cohesive Zone ◽  
Rupture Life ◽  
Stress Rupture ◽  
Creep Rupture ◽  
Time Dependent ◽  
Element Analysis ◽  
Rupture Model ◽  
Term Creep

In this article, a creep–rupture model of aluminum alloys is developed using a time-dependent cohesive zone law. For long-term creep rupture, a time jump strategy is used in a cohesive zone law. Stress–rupture scatter of aluminum alloy 4032-T6 is fitted with a power law form. Then, change in the slope of a stress-rupture line is identified on a log–log scale. Implicit finite element analysis is employed with a model containing a cohesive zone. Stress–rupture curves at various given temperatures are calculated and compared with experimental ones. Results show that a proposed method allows predicting creep–rupture life of aluminum alloys.

Recent Advances for J Simplified Assessment in RSE-M Code

2003 ◽  
Author(s):  
Bruno Michel ◽  
Jean-Philippe Sermage ◽  
Philippe Gilles ◽  
Bruno Barthelet ◽  
Patrick Le Delliou
Keyword(s):  
Large Scale ◽  
Surface Defects ◽  
Complex Loading ◽  
Limit Load ◽  
Assessment Method ◽  
Reactor Power ◽  
Pressurized Water ◽  
Reference Stress ◽  
Recent Advances ◽  
Wide Range

The RSE-M Code [1] provides rules and requirements for in-service inspection of French Pressurized Water Reactor power plant components. Non mandatory guidance is given in the Code for analytical flaw evaluation in a wide range of situations. In Appendix 5.4 of the Code, influence coefficients are provided to calculate stress intensity factors in pipes and shells containing semi-elliptical surface defects. The J assessment method is based on the reference stress concept with two options for reference loads evaluation: “CEP elastic plastic stress” and “CLC modified limit load”. In this paper recent advances concerning J assessment under mechanical loading for a crack located in a pipe-elbow junction are presented. Reference stress evaluation with “CLC” option is developed and mechanical foundations of the equation of large scale yielding under complex loading (pressure, in-plane and out-of-plane bending) are presented.

A New Approach of Reliability Design for Creep Rupture Property

2009 ◽  
Author(s):  
Jie Zhao ◽  
Dong-ming Li ◽  
Yuan-yuan Fang ◽  
Shi-jie Zhu
Keyword(s):  
Parametric Method ◽  
Stress Rupture ◽  
Creep Rupture ◽  
Parameter Method ◽  
Reliability Design ◽  
Safety Coefficient ◽  
Real Distribution ◽  
Z Parameter ◽  
Rupture Data ◽  
Temperature Time

It has been noted that the use of safety coefficient can deal with uncertainties existed in practical structures, while reliability concept provides more precise results by considering the real distribution of creep rupture property. Generally, creep rupture data of a heat-resistant steel can be compressed into a narrow band by using a temperature-time parametric method such as Larson-Miller or Manson-Haferd method. In order to describe the scattering of the data, the current paper proposes a “Z parameter” method to represent the magnitude of the deviation of the rupture data to master curve. Statistical analysis shows that the scattering of Z parameter for several types of steels is supported by normal distribution. Using this method, it is possible to achieve unified analysis of the creep rupture data in various temperature and stress conditions. Stress-TTP-Reliability curves (σ-TTP-R curves), Stress-Rupture time-Reliability curves (σ-tr-R curves) and Allowable stress-Temperature-Reliability curves ([σ]-T-R curves) are proposed which could embrace reliability concept into creep rupture property design.

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