Residual Stresses Evaluation in Welds and Implications for Design for Pressure Vessel Applications

2005 ◽  
Author(s):  
John W. H. Price ◽  
Anna Paradowska ◽  
Trevor Finlayson
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Scale Up ◽  
Small Scale ◽  
Fitness For Purpose ◽  
Fatigue And Fracture ◽  
Single Bead ◽  
Key Issues ◽  
Neutron Diffraction Technique

Welding residual stresses have important consequences on the performance of engineering components. High residual stresses lead to loss of performance in corrosion, fatigue and fracture but as yet these consequences are poorly quantified. The major cause of this is that residual stress often remains the single largest unknown in industrial damage situations since they are difficult to measure or estimate theoretically. One of the key issues in the study of residual stress is that the detail of the stress distribution on a small scale (in the order of millimetres) can be important. In this paper, the neutron diffraction technique is used which while it is a very expensive technique, is capable of non-destructively measuring residual stresses at this scale up to a depth of 35mm. The investigation reported compares the residual stress characteristics due to various restraints for a single bead and in fully restrained samples with different numbers of beads. The findings have important consequences with respect to design of welding procedures and fitness for purpose assessments.

Residual Stresses Evaluation in Welds and Implications for Design for Pressure Vessel Applications

2006 ◽  
Vol 128 (4) ◽  
pp. 638-643 ◽  
Author(s):  
John W. H. Price ◽  
Anna M. Pardowska ◽  
Raafat Ibrahim ◽  
Trevor R. Finlayson
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Pressure Vessel ◽  
Scale Up ◽  
Small Scale ◽  
Fatigue And Fracture ◽  
Single Bead ◽  
Key Issues ◽  
Neutron Diffraction Technique

Welding residual stresses have important consequences on the performance of engineering components. High residual stresses may lead to loss of performance in corrosion, fatigue, and fracture but as yet these consequences are poorly quantified. The major cause of this is that residual stress often remains the single largest unknown in industrial damage situations since it is difficult to measure or estimate theoretically. One of the key issues in the study of residual stress is that the detail of the stress distribution on a small scale (in the order of millimeters) can be important. In this paper, the neutron diffraction technique is used which while it is a very expensive technique, is capable of nondestructively measuring residual stresses at this scale up to a depth of 35mm. The investigation reported compares the residual stress characteristics due to various restraints for a single bead and in fully restrained samples with different numbers of beads. This paper considers the results of the neutron diffraction studies in relation to fitness for purpose guidance and implication for pressure vessel design.

Neutron Diffraction Evaluation of Residual Stress for Several Welding Arrangements and Comparison With Fitness-for-Purpose Assessments

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Anna M. Pardowska ◽  
John W. H. Price ◽  
Raafat Ibrahim ◽  
Trevor R. Finlayson
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Assessment Procedure ◽  
Stress Distributions ◽  
Fitness For Purpose ◽  
Single Bead ◽  
Surface Measurements ◽  
Number Of Passes ◽  
Neutron Diffraction Technique ◽  
Level 2

In this research, the neutron diffraction technique was used to investigate and compare the residual stress characteristics in several weld arrangements. This research has focused on the effects on residual stress of restraint condition applied during welding, the start and end of the weld for a single bead, and increasing the number of passes. The measured residual stress distributions are normalized by the yield strength of the material and compared with distribution provided in fitness-for-purpose procedures. It is found that the current safety assessment procedure BS 7910 and R6 Level 1 significantly conservative for longitudinal stresses outside the weld and heat affected zone, and for transverse residual stress across the weldment for surface measurements. For a less conservative assessment, R6 Level 2 is recommended, however, even if this assessment is often conservative, in particular, for transverse residual stresses.

Neutron diffraction analysis of the residual stress distribution in a bent bar

2000 ◽  
Vol 35 (4) ◽  
pp. 235-246 ◽  
Author(s):  
A. N Ezeilo ◽  
G. A Webster
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Residual Stress Distribution ◽  
Four Point Bending ◽  
Refinement Method ◽  
Nickel Based Alloy ◽  
Neutron Diffraction Technique ◽  
Profile Refinement

A well-characterized residual stress distribution resulting from four-point bending has been analysed using the neutron diffraction technique. Residual stresses were obtained from the strains measured at discrete positions through the bent bar on the (111) and (311) crystal planes of a nickel-based alloy using the appropriate diffraction elastic constants. In addition a profile refinement method was used to determine the residual stresses from average strains from all the diffraction peaks in the spectrum. The measured residual stress profiles have also been compared with strain gauge data and with analytical and finite element predictions. It has been established that the profile refinement approach gives stresses which most closely match those obtained by the non-diffraction techniques.

Neutron Diffraction Evaluation of Residual Stress for Several Welding Arrangements and Comparison With Fitness-for-Purpose Assessments

2006 ◽  
Author(s):  
Anna M. Paradowska ◽  
John W. H. Price ◽  
Raafat Ibrahim ◽  
Trevor Finlayson ◽  
Richard Blevins ◽  
...  
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Assessment Procedure ◽  
Stress Distributions ◽  
Fitness For Purpose ◽  
Single Bead ◽  
Level 1 ◽  
Number Of Passes ◽  
Neutron Diffraction Technique ◽  
Level 2

In this research the neutron diffraction technique was used to investigate and compare the residual stress characteristics in a several weld arrangements. This research has focused on the effects on residual stress of: • restraint condition applied during welding, • the start and end of the weld for a single bead, and • increasing the number of passes. The measured residual stress distributions are normalized by the yield strength of the material and compared with distribution provided in fitness-for-purpose procedures. It is found that the current safety assessment procedure BS 7910 and R6 Level 1 are significantly conservative. For a less conservative assessment R6 Level 2 is recommended, however even this assessment is often conservative, in particular for transverse residual stresses.

Theoretical prediction of residual stresses induced by cold spray with experimental validation

2019 ◽  
Vol 15 (3) ◽  
pp. 599-616 ◽  
Author(s):  
Dibakor Boruah ◽  
Xiang Zhang ◽  
Matthew Doré
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Cold Spray ◽  
Residual Stress Distribution ◽  
Thermal Mismatch ◽  
Individual Layer ◽  
Content Type ◽  
Layer Height ◽  
Proposed Model

PurposeThe purpose of this paper is to develop a simple analytical model for predicting the through-thickness distribution of residual stresses in a cold spray (CS) deposit-substrate assembly.Design/methodology/approachLayer-by-layer build-up of residual stresses induced by both the peening dominant and thermal mismatch dominant CS processes, taking into account the force and moment equilibrium requirements. The proposed model has been validated with the neutron diffraction measurements, taken from the published literature for different combinations of deposit-substrate assemblies comprising Cu, Mg, Ti, Al and Al alloys.FindingsThrough a parametric study, the influence of geometrical variables (number of layers, substrate height and individual layer height) on the through-thickness residual stress distribution and magnitude are elucidated. Both the number of deposited layers and substrate height affect residual stress magnitude, whereas the individual layer height has little effect. A good agreement has been achieved between the experimentally measured stress distributions and predictions by the proposed model.Originality/valueThe proposed model provides a more thorough explanation of residual stress development mechanisms by the CS process along with mathematical representation. Comparing to existing analytical and finite element methods, it provides a quicker estimation of the residual stress distribution and magnitude. This paper provides comparisons and contrast of the two different residual stress mechanisms: the peening dominant and the thermal mismatch dominant. The proposed model allows parametric studies of geometric variables, and can potentially contribute to CS process optimisation aiming at residual stress control.

A Further Study of Residual Stresses in Circumferential Welds

1973 ◽  
Vol 95 (4) ◽  
pp. 238-242 ◽  
Author(s):  
S. Vaidyanathan ◽  
H. Weiss ◽  
I. Finnie
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Base Metal ◽  
Filler Metal ◽  
Residual Stress Distribution ◽  
Experimental Results ◽  
Circumferential Welds ◽  
Single Pass ◽  
Full Penetration

The residual stress distribution for a circumferential weld between cylinders was obtained in a prior publication for a full penetration, single pass weld with no variation of alloy content across the weld. In the present work the approach is extended to cover a wider variety of weld conditions. It is shown that the effects of multipass welds, partial penetration welds, and welds with filler metal differing greatly in properties from the base metal can approximately be taken into account. Experimental results are presented to support the proposed method of analysis.

The Effect of Residual Stresses on the Fracture Resistance of Ductile Steels

2002 ◽  
Author(s):  
Noel P. O’Dowd ◽  
Yuebao Lei
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Residual Stresses ◽  
Crack Opening ◽  
Stress Distributions ◽  
Residual Stress Field ◽  
Element Analysis ◽  
Fatigue And Fracture ◽  
Negative Effect ◽  
Fracture Performance

Tensile residual stresses, such as those generated by welding, act as crack opening stresses and can have a negative effect on the fatigue and fracture performance of a component. In this work the effect of representative residual stress distributions on the fracture behaviour of a ferritic steel has been examined using finite element analysis. A Gurson-type void growth model is used to model the effect of ductile tearing ahead of a crack. For the cases examined it is seen that a tensile residual stress field may lead to a reduction in the toughness of the material (as represented by the J-resistance curve). The observed difference in toughness can be linked to the different constraint levels in the specimens due to the introduction of the residual stress field and can be rationalised through the use of a two parameter, J–Q approach.

Measurement and Modelling of Residual Stresses in Fracture Toughness Specimens Extracted From Large Components

2008 ◽  
Author(s):  
S. J. Lewis ◽  
S. Hossain ◽  
C. E. Truman ◽  
D. J. Smith ◽  
M. Hofmann
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Residual Stresses ◽  
Driving Force ◽  
Large Scale ◽  
Structural Integrity ◽  
Mechanical Load ◽  
Crack Driving Force ◽  
Neutron Diffraction Technique ◽  
Fracture Specimens

A number of previously published works have shown that the presence of residual stresses can significantly affect measurements of fracture toughness, unless they are properly accounted for when calculating parameters such as the crack driving force. This in turn requires accurate, quantitative residual stress data for the fracture specimens prior to loading to failure. It is known that material mechanical properties may change while components are in service, for example due to thermo-mechanical load cycles or neutron embrittlement. Fracture specimens are often extracted from large scale components in order to more accurately determine the current fracture resistance of components. In testing these fracture specimens it is generally assumed that any residual stresses present are reduced to a negligible level by the creation of free surfaces during extraction. If this is not the case, the value of toughness obtained from testing the extracted specimen is likely to be affected by the residual stress present and will not represent the true material property. In terms of structural integrity assessments, this can lead to ‘double accounting’ — including the residual stresses in both the material toughness and the crack driving force, which in turn can lead to unnecessary conservatism. This work describes the numerical modelling and measurement of stresses in fracture specimens extracted from two different welded parent components: one component considerably larger than the extracted specimens, where considerable relaxation would be expected as well as a smaller component where appreciable stresses were expected to remain. The results of finite element modelling, along with residual stress measurements obtained using the neutron diffraction technique, are presented and the likely implications of the results in terms of measured fracture toughness are examined.

scholarly journals Separation of the Formation Mechanisms of Residual Stresses in LPBF 316L

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1234
Author(s):  
Alexander Ulbricht ◽  
Simon J. Altenburg ◽  
Maximilian Sprengel ◽  
Konstantin Sommer ◽  
Gunther Mohr ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Residual Stress Distribution ◽  
Formation Mechanisms ◽  
Micro Computed Tomography ◽  
Solidification Shrinkage ◽  
Stainless Steel 316L ◽  
Heat Accumulation ◽  
Cooling Rates

Rapid cooling rates and steep temperature gradients are characteristic of additively manufactured parts and important factors for the residual stress formation. This study examined the influence of heat accumulation on the distribution of residual stress in two prisms produced by Laser Powder Bed Fusion (LPBF) of austenitic stainless steel 316L. The layers of the prisms were exposed using two different border fill scan strategies: one scanned from the centre to the perimeter and the other from the perimeter to the centre. The goal was to reveal the effect of different heat inputs on samples featuring the same solidification shrinkage. Residual stress was characterised in one plane perpendicular to the building direction at the mid height using Neutron and Lab X-ray diffraction. Thermography data obtained during the build process were analysed in order to correlate the cooling rates and apparent surface temperatures with the residual stress results. Optical microscopy and micro computed tomography were used to correlate defect populations with the residual stress distribution. The two scanning strategies led to residual stress distributions that were typical for additively manufactured components: compressive stresses in the bulk and tensile stresses at the surface. However, due to the different heat accumulation, the maximum residual stress levels differed. We concluded that solidification shrinkage plays a major role in determining the shape of the residual stress distribution, while the temperature gradient mechanism appears to determine the magnitude of peak residual stresses.

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