The Combined Effects of Residual Stress and Warm Prestressing on Cleavage Fracture in Steels

2012 ◽  
Author(s):  
Karin Rosahl ◽  
Julian Booker ◽  
David Smith
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Cleavage Fracture ◽  
Operating Conditions ◽  
System Model ◽  
Engineering Structures ◽  
Initial Residual Stress ◽  
Warm Prestressing ◽  
Subsequent Fracture ◽  
New System

Residual stresses (RS) appear in most engineering structures, either because they have been deliberately introduced or they are a by-product of the manufacturing process. Since RS play an important role in increasing and decreasing the possibility of failure, it is necessary that their effect on the integrity of the structure is understood. In the presence of RS, many components are subjected to a variety of prior loading histories. One such case is often associated with warm prestressing (WPS), where the component is subjected to some form of preloading at a temperature higher than operating conditions. The aim here was to explore how WPS, together with RS, might influence the subsequent fracture conditions for cleavage fracture. First, a model for WPS is reconsidered so that it could be used for Monte Carlo (MC) simulations of WPS. Results are compared with experimental data. The model is then adopted to consider the effects of long range residual stress created in fracture samples through an initial misfit. This is done by fitting the sample into a structure, with the new system subsequently being subjected to WPS conditions. The advantage of the system model is that it facilitates the systematic prediction of the interrelationship and interaction between the applied loads and the misfit (or residual) stresses. The results show that tensile RS act to enhance the effects of WPS, and the WPS cycle, in itself, can act to relax the initial residual stress.

Analysis of circumferentially welded thin-walled cylinders to study the effects of tack weld orientations and joint root opening on residual stress fields

2009 ◽  
Vol 223 (5) ◽  
pp. 1037-1049 ◽  
Author(s):  
N U Dar ◽  
E M Qureshi ◽  
A M Malik ◽  
M M I Hammouda ◽  
R A Azeem
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Arc Welding ◽  
Operating Conditions ◽  
Stress Fields ◽  
Welded Structures ◽  
Prime Concern ◽  
Thin Walled ◽  
Tack Weld ◽  
Welding Processes

In recent years, the demand for resilient welded structures with excellent in-service load-bearing capacity has been growing rapidly. The operating conditions (thermal and/or structural loads) are becoming more stringent, putting immense pressure on welding engineers to secure excellent quality welded structures. The local, non-uniform heating and subsequent cooling during the welding processes cause complex thermal stress—strain fields to develop, which finally leads to residual stresses, distortions, and their adverse consequences. Residual stresses are of prime concern to industries producing weld-integrated structures around the globe because of their obvious potential to cause dimensional instability in welded structures, and contribute to premature fracture/failure along with significant reduction in fatigue strength and in-service performance of welded structures. Arc welding with single or multiple weld runs is an appropriate and cost-effective joining method to produce high-strength structures in these industries. Multi-field interaction in arc welding makes it a complex manufacturing process. A number of geometric and process parameters contribute significant stress levels in arc-welded structures. In the present analysis, parametric studies have been conducted for the effects of a critical geometric parameter (i.e. tack weld) on the corresponding residual stress fields in circumferentially welded thin-walled cylinders. Tack weld offers considerable resistance to the shrinkage, and the orientation and size of tacks can altogether alter stress patterns within the weldments. Hence, a critical analysis for the effects of tack weld orientation is desirable.

scholarly journals UK Research Programme on Residual Stresses: A Review of Progress

2008 ◽  
Author(s):  
S. K. Bate ◽  
P. Hurrell ◽  
J. A. Francis ◽  
M. Turski
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Stress Measurement ◽  
Experimental Testing ◽  
Research Programme ◽  
Austenitic Steels ◽  
Assessment Procedure ◽  
Engineering Structures ◽  
Modelling Techniques

A long-term UK research programme on residual stresses was launched in 2004. It involves Rolls-Royce plc and Serco Assurance, supported by UK industry and academia. The programme is aimed at progressing the understanding of weld residual stresses and the implementation of finite element simulation and residual stress measurement for assessing the integrity of engineering structures. Following on from this, the intention is then to develop improved guidance on residual stress modelling techniques and then to provide methods and analysis tools for design in order to control and minimise residual stress. The focus of the work to date has been to develop modelling guidelines which can be used by a finite element analyst to predict the residual stresses in austenitic welded components. These guidelines are now drafted and will be incorporated into the next issue of the British Energy R6 defect assessment procedure following peer review. The guidelines have been developed based on the experience that has been attained using various modelling techniques. To support this development, a series of welded mock-ups have been manufactured. The residual stresses in these welds have been measured using various techniques (diffraction and strain relaxation). These measurements are being used to validate the predicted stresses. It is only by corroborating each other that the resulting residual stresses can be confidently used for assessment. Mock-ups are also being used to develop material models for ferritic steel which undergo phase transformations, and to investigate how various weld parameters affect the magnitude and distribution of residual stress. Similarly, mock-ups have been manufactured to investigate the effect of start-stops on residual stresses. The programme is also supported by experimental testing to develop physical and mechanical properties which are required for analysis, i.e. up to melting temperature. Both conventional and miniaturised testing has been used to measure properties in ferritic and austenitic steels. A task has also been undertaken to develop a methodology for providing upper bound residual stress profiles which can be used as an initial estimate of stress for use in structural assessment.

UK Research Programme on Residual Stresses: Progress to Date

2007 ◽  
Author(s):  
S. K. Bate ◽  
A. P. Warren ◽  
C. T. Watson ◽  
P. Hurrell ◽  
J. A. Francis
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Stress Measurement ◽  
Research Programme ◽  
Assessment Procedure ◽  
Engineering Structures ◽  
Element Analysis ◽  
Simplifying Assumptions ◽  
Modelling Techniques

A long-term UK research programme on residual stresses was launched in 2004. It involves Rolls-Royce plc and Serco Assurance, and is supported by UK industry and academia. The programme is aimed at progressing the understanding of weld residual stresses and the implementation of finite element simulation and residual stress measurement for assessing the integrity of engineering structures. Following on from this, the intention is then to develop improved guidance on residual stress modelling techniques. In the first two years finite element activities have addressed heat source representation, simplified modelling (e.g. 2D v 3D, bead lumping), material hardening models, high temperature behaviour and phase transformations. It is recognized that simplifying assumptions have to be made in order to reduce the computational run-time and modelling complexity, especially for multi-pass welds. The effects of these assumptions on the determined stresses have been considered by carrying out finite element analyses of welded mock-ups. The welded mock-ups have been developed to provide measured residual stress data which are necessary to validate the modelling techniques that have been developed. These activities have been used to support the development of guidelines on the use finite element analysis to predict residual stresses in welded components. These guidelines will be incorporated in the next issue of the British Energy R6 defect assessment procedure.

scholarly journals Residual Stresses in Passenger Car Wheels

2006 ◽  
Author(s):  
Shuangqin Liu ◽  
Benjamin Perlman ◽  
Jeffrey Gordon
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Residual Stress Distribution ◽  
Operating Conditions ◽  
Computational Time ◽  
Passenger Car ◽  
3 Dimensional ◽  
Dimensional Modeling ◽  
Service Loading

Knowledge of the residual stress state in wheels resulting from manufacturing and subsequent service loading is useful for several practical reasons. The ability to estimate residual stress levels permits the tuning of manufacturing processes to control the magnitude and distribution of these stresses in new wheels in order to achieve safe performance in service. Similarly, understanding the redistribution of residual stresses following application of service loads (wheel/rail contact and thermal stresses) is crucial to avoid operating conditions which may lead to premature wheel failure. Axisymmetric (2-dimensional) analyses are typically performed in order to conduct manufacturing process simulations since these processes affect the entire wheel in a circumferentially uniform sense. Generally, analyses involving service loading have sought to identify the "shakedown state" at which the residual stress distribution stabilizes after some number of loading cycles. In order to properly account for service loads, 3-dimensional models are required since contact and brake shoe thermal loading are not axisymmetric. Since the as-manufactured residual stress distribution must be considered in a service loading simulation, 3-dimensional modeling of this process is required. This paper presents a preliminary comparison of 2- and 3-dimensional modeling of the wheel heat treatment process. Except for the increased computational time required for the 3-dimensional analysis, the results agree favorably. The 3-dimensional model is used to simulate service loads involving wheel-rail contact loading representative of a typical passenger car. The model is exercised with a variety of material models for comparison with previous work. Results are presented for multiple loading scenarios and shakedown stress states are established for a range of applied loads.

Generating Well Defined Residual Stresses in Laboratory Specimens

2006 ◽  
Author(s):  
Amir-Hossein Mahmoudi ◽  
Christpher Aird ◽  
Christopher E. Truman ◽  
Ali Mirzaee-Sisan ◽  
David J. Smith
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Material Damage ◽  
Testing Laboratory ◽  
Engineering Structures ◽  
Damage Mechanisms ◽  
Microstructural Changes ◽  
Advantages And Disadvantages ◽  
New Methods ◽  
Insight Into

Residual stresses play an important role in increasing and decreasing the possibility of failure. The magnitude and direction of the residual stresses is an important factor in the integrity of engineering structures, including those containing defects. Ideally, we would like to gain insight into the integrity of a structure through testing laboratory samples. The purpose of this paper is to review methods of introducing residual stresses into laboratory specimens that are either subsequently loaded to fracture or used to assess the influence of residual stress on material damage mechanisms. Three methods, mechanical, thermal and welding, are scrutinized and illustrative examples provided. The advantages and disadvantages are explored. We conclude that new methods that do not introduce microstructural changes during the generation of residual stress should be sought if an improved understanding of the effects residual stress on fracture is required.

Effect of Residual Stress, Temperature and Adhesion on Wheel Surface Fatigue Cracking

2008 ◽  
Author(s):  
Daniel H. Stone ◽  
Scott M. Cummings
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Contact Stress ◽  
Fatigue Cracking ◽  
Fatigue Tests ◽  
Operating Conditions ◽  
Defect Prevention ◽  
Class C ◽  
Research Consortium

The Wheel Defect Prevention Research Consortium (WDPRC) conducted an analysis pertaining to the fatigue cracking of wheel treads by incorporating the effects of residual stresses, temperature, and wheel/rail contact stress. Laboratory fatigue tests were conducted on specimens of wheel tread material under a variety of conditions allowing the analysis to properly account for the residual stresses accumulated in normal operating conditions. Existing literature was used in the analysis in consideration of the effects of contact stress and residual stress relief. This project was performed to define a temperature range in which the life of an AAR Class C wheel is not shortened by premature fatigue and shelling. Wayside wheel thermal detectors are becoming more prevalent on North American railroads as a means of identifying trains, cars, and wheels with braking issues. Yet, from a wheel fatigue perspective, the acceptable maximum operating temperature remains loosely defined for AAR Class C wheels. It was found that residual compressive circumferential stresses play a key role in protecting a wheel tread from fatigue damage. Therefore, temperatures sufficient to relieve residual stresses are a potential problem from a wheel fatigue standpoint. Only the most rigorous braking scenarios can produce expected train average wheel temperatures approaching the level of concern for reduced fatigue life. However, the variation in wheel temperatures within individual cars and between cars can result in temperatures high enough to cause a reduction in wheel fatigue life.

Effect of Initial Residual Stress on Stress Relaxation in Cold-Drawn Steel Rods

2010 ◽  
Vol 652 ◽  
pp. 227-232
Author(s):  
Jesus Ruiz-Hervias ◽  
Jose M. Atienza ◽  
Javier R. Santisteban ◽  
Manuel Elices Calafat
Keyword(s):  
Residual Stress ◽  
Stress Relaxation ◽  
Residual Stresses ◽  
Cross Section ◽  
Stress Relaxation Behavior ◽  
Relaxation Experiment ◽  
Initial Residual Stress ◽  
Residual Stress State ◽  
Residual Strains

This work shows the effect of the initial residual stress state on the stress relaxation behavior of cold-drawn steel rods. The evolution of residual strains at several locations along the rod diameter was measured in-situ by neutron diffraction during a stress relaxation experiment. It was found that if residual stresses are significant, stress relaxation is not homogeneous in the cross-section of the rods. This also explains the higher stress losses found in the rods with high residual stresses.

Residual Stress Shakedown in Typical Weld Joints and Its Effect on Fatigue of FPSOs

2007 ◽  
Author(s):  
Liangbi Li ◽  
Torgeir Moan ◽  
Bin Zhang
Keyword(s):  
Residual Stress ◽  
Cyclic Loading ◽  
Residual Stresses ◽  
Welded Joints ◽  
Hot Spot ◽  
Fatigue Behaviour ◽  
Combined Effect ◽  
Element Analysis ◽  
Variable Amplitude ◽  
Initial Residual Stress

Structural members of FPSO hulls often undergo fairly large static loading before they enter service or variable amplitude cyclic loading when they are in service. The combined effect of both applied stress and high initial residual stress is expected to cause shakedown of the residual stresses. Only a few papers seem to deal with appropriate procedures for fatigue analysis by considering the combined effect of variable amplitude cyclic loading with shakedown of residual stresses. Hence, the fatigue behaviour of welded joints in some experiments could not be explained reasonably well. In this paper, some typical welded connections in ship-shaped structures are investigated with 3-D elastic-plastic finite element analysis. The effect of residual stress relaxation, initial residual stress and the applied load after variable amplitude cyclic loading is revealed, and a formula for predicting the residual stress at hot spot quantitatively is proposed. Based on the formula, an improved fatigue procedure is introduced. The proposed fatigue procedure was validated against the experimental results. Therefore, the modified fatigue procedure could be applied to welded joints under arbitrary cyclic loading while accounting for shakedown of residual stresses.

scholarly journals Elastic follow-up and relaxation of residual stresses

2010 ◽  
Vol 224 (4) ◽  
pp. 777-787 ◽  
Author(s):  
D J Smith ◽  
J McFadden ◽  
S Hadidimoud ◽  
A J Smith ◽  
A J Stormonth-Darling ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Experimental Results ◽  
Test Rig ◽  
Reliable Measure ◽  
Initial Residual Stress ◽  
Series Of Experiments ◽  
Different Levels ◽  
Simple Models

A series of experiments were undertaken using a multiple bar assembly to measure elastic follow-up and relaxation of an initial residual stress. A test rig was designed to permit different levels of elastic follow-up to occur. The general features of the experimental results confirmed predictions provided by simple models. The most reliable measure of elastic follow-up was obtained by measuring the relaxation of the initial residual stress. The rate of relaxation of the residual stress is found to be proportional to the elastic follow-up factor.

Modelling the Interpass Temperature Effect on Residual Stress in Low Transformation Temperature Stainless Steel Welds

2011 ◽  
Author(s):  
H. Dai ◽  
R. J. Moat ◽  
P. J. Withers
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Residual Stresses ◽  
Transformation Temperature ◽  
Contour Method ◽  
304L Stainless Steel ◽  
Engineering Structures ◽  
Four Levels ◽  
Carry Over ◽  
Interpass Temperature

Weld residual stresses often have serious implications for the integrity of engineering structures (distortion, stress-corrosion cracking, hydrogen-induced cracking). Previously, it has been demonstrated by the authors that the use of a stainless steel welding consumable with a low martensite start temperature in single-pass welding can lead to lower (potentially harmful) tensile residual stresses or even compressive stress within the fusion zone and heat affected zones compared to non-transforming austenitic fillers. However, such effects may not carry over to multi-pass welding if the filler transforms fully on cooling from the first pass. In this paper finite element modelling is used to examine the use of interpass hold temperatures on the residual stresses introduced using such weld fillers in multi-pass welding of 304L stainless steel plate. Four levels of interpass temperature have been studied. The model has also been verified against experimental data obtained using the contour method for two welded plates having two different inter-pass temperatures. It is demonstrated that interpass hold temperatures above, or around, the transformation temperature can have very significant effects, allowing residual stress management of the resulting welded joint.

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