The Influence of Prior Loading on Structural Integrity

Smith, David J.

doi:10.1016/b0-08-043749-4/07116-0

Cited by 10 publications

(8 citation statements)

References 89 publications

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“…The increase in the strength is due to the accumulation of plastic strain in the material after pre-straining. 38 The accumulated plastic strain after pre-straining can be qualitatively determined by hardness measurements. The hardness values of the non-strained, 10% pre-strained and 20% pre-strained base material are 154, 218 and 251 H V , respectively (Figure 5).…”

Section: Discussionmentioning

confidence: 99%

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Experimental and numerical study of strength mismatch in cross-weld tensile testing

Acar

Güngör

2015

The Journal of Strain Analysis for Engineering Design

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The mechanical properties of welded boiler tubes used in power plants can be significantly altered as a result of the fabrication history, such as pre-straining and heat treatment. The primary aim of the study was to determine the effect of fabrication history on local tensile properties across the welds. This was achieved by testing cross-weld specimens machined from welded thin-walled tubes (with unstrained or pre-strained base metal) before and after heat treatment. Digital image correlation (DIC), which is a full-field strain measurement technique, was implemented in order to obtain the local stress-strain curves and to extract the corresponding local tensile properties such as offset proof stress. Evidence of strain hardening due to the constraint and thermo-mechanical cycles during the welding process was found in the heat-affected-zone (HAZ) and evidence of softening was observed in the pre-strained base metal. It was found that the heat treatment process removed the effect of pre-straining and welding on the proof stress and the strength along the specimen was nearly homogenized. However, mapping the local stress-strain curves in the as-welded crossweld specimens with pre-strained base metal has revealed abnormal strain-relaxation with increase in load in the weld-affected region. For a better understanding of this behaviour, a tensile test of a cross-weld specimen with a large strength mismatch between the weld metal and the base metal was simulated using the finite element method. It was found that the strength mismatch in the specimen causes the development of bi-axial stresses in the HAZ once local yielding begins and the use of global axial stress to construct the local stress-strain 2 curve results in an apparent "reduced-strain" anomaly. Nevertheless, for the strength mismatch ratios studied, this anomalous behaviour did not seem to significantly affect the determination of the local proof stress in the specimens.

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Section: Discussionmentioning

confidence: 99%

“…4(b)). The increase in the strength is due to the accumulation of plastic strain in the material after pre-straining [38]. The accumulated plastic strain after prestraining can be qualitatively determined by hardness measurements.…”

Section: Effects Of Manufacturing Steps On Tensile Propertiesmentioning

confidence: 99%

Experimental and numerical study of strength mismatch in cross-weld tensile testing

Acar

Güngör

2015

The Journal of Strain Analysis for Engineering Design

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“…In general, for structures subjected to tensile loading tensile residual stresses are harmful and reduce component life and compressive residual stresses are beneficial [1]. Therefore, for integrity assessments of engineering components, it is important to obtain a detailed knowledge of residual stresses [2].…”

Section: Introductionmentioning

confidence: 99%

A New Procedure to Measure Near Yield Residual Stresses Using the Deep Hole Drilling Technique

et al. 2008

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Mechanical strain relief techniques for estimating the magnitude of residual stress work by measuring strains or displacements when part of the component is machined away. The underlying assumption is that such strain or displacement changes result from elastic unloading. Unfortunately, in components containing high levels of residual stress, elasticplastic unloading may well occur, particularly when the residual stresses are highly triaxial. This paper examines the performance of one mechanical strain relief technique particularly suitable for large section components, the deep hole drilling (DHD) technique. The magnitude of error is calculated for different magnitudes of residual stress and can be substantial for residual stress states close to yield. A modification to the technique is described to allow large magnitudes of residual stress to be measured correctly. The new technique is validated using the case of a quenched cylinder where use of the standard DHD technique leads to unacceptable error. The measured residual stresses using the new technique are compared with the results obtained using the neutron diffraction technique and are shown to be in excellent agreement.

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“…There is an increasing body of evidence [10,11], however, highlighting the effect of plastic strain history on ensuing fracture behaviour. The level of plastic strain is often assumed to control nucleation of micro-cracks in brittle fracture [12] and the degree of void growth in ductile failure [13].…”

Section: Introductionmentioning

confidence: 99%

Diffraction measurements for evaluating plastic strain in A533B ferritic steel—a feasibility study

Lewis¹,

Truman²

2010

J. Phys. D: Appl. Phys.

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It is known that the physical properties of many engineering materials may be strongly affected by previous loading, in particular prior plastic deformation. Most obviously, work hardening will alter subsequent yielding behaviour. Plastic deformation may also preferentially align the material microstructure, resulting in anisotropy of subsequent behaviour and a change in material fracture resistance. When physical characterisation is undertaken by experimental testing it is, therefore, important to have some knowledge of the current state of the material. As a result, it is desirable to have methods of quantitatively evaluating the level of plastic deformation which specimen material may have experienced prior to testing. This paper presents the results of a feasibility study, using a ferritic reactor pressure vessel steel, into the use of diffractive methods for plastic strain evaluation. Using neutron diffraction, changes in diffraction peak width and anisotropy of peak response were correlated with plastic deformation in a tensile test. The relationships produced were then used to evaluate permanent deformation levels in large samples, representative of standard fracture toughness test specimens.

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The Influence of Prior Loading on Structural Integrity

Cited by 10 publications

References 89 publications

Experimental and numerical study of strength mismatch in cross-weld tensile testing

Experimental and numerical study of strength mismatch in cross-weld tensile testing

A New Procedure to Measure Near Yield Residual Stresses Using the Deep Hole Drilling Technique

Diffraction measurements for evaluating plastic strain in A533B ferritic steel—a feasibility study

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