Evaluating creep cracking in welded fracture mechanics specimens

Nikbin, Kamran

doi:10.1016/j.engfracmech.2006.08.023

Cited by 6 publications

(7 citation statements)

References 25 publications

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“…5,34 This is observed to be true for all cases in which the CT specimen comprises a single material such as the PM configurations. 6,34,40 However, it should be noted that the C * -integral is also applicable and widely used in other cracked specimen geometries, for example, DENT plate proposed by Assire et al 42 The static form of C * , that is, J-integral, was derived on the basis that the contour does not cross any material boundaries, that is, the structure is homogeneous. 36 Considerations should be made of the validity of C * -contour path-independence when applying the integral to a heterogeneous structure, typically welds.…”

Section: Considerations Of Geometry Of Specimen and Residual Stressesmentioning

confidence: 77%

“…The C * -integral is considered to be path-independent and thus can be used to describe CCG response. 5,34 This is observed to be true for all cases in which the CT specimen comprises a single material such as the PM configurations. 6,34,40 However, it should be noted that the C * -integral is also applicable and widely used in other cracked specimen geometries, for example, DENT plate proposed by Assire et al 42…”

Section: Ct Specimenmentioning

confidence: 77%

“…30 Care should be taken when C * -values are obtained via FE modelling since the values differ for plane stress and plane strain significantly, as described by Nikbin. 34 Several solutions exist with the most widely used being the displacement rate solution related to the load applied, P , and load line displacement rate, Δ · C or V · C –equation (18). 31 Relations between the crack growth rate, a · , and C * -integral value can be established and accurate predictions of creep life are obtained (see Figures 39 and 40)…”

Section: Ct Specimenmentioning

confidence: 99%

“…Residual stresses that arise within the weld structure can affect the failure life predictions in a CT specimen with tensile ones assisting crack opening and compressive residual stresses reducing the crack growth rate. 37,38 Thus, the following residual stress compensation expression for reference stress C * -value is suggested by Nikbin 34…”

Section: Ct Specimenmentioning

confidence: 99%

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Practical considerations of the use of cross-weld and compact tension specimens’ creep data

Petkov

Hyde

2016

The Journal of Strain Analysis for Engineering Design

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The present article gives an overview of the use of cross-weld and compact tension specimen modelling and analyses data to characterise creep behaviour of high temperature components. Cross-weld and CT specimens are used to describe creep crack growth in heterogeneous material structures, such as welds, and a number of factors that affect the creep behaviour of the structure, associated with this heterogeneity, have been identified. Creep data obtained from cross-weld specimen modelling is substantially affected by the material model used (e.g. Norton Power law, Liu/Murakami model, etc.), stress singularities that arise at the material interfaces and in between the columnar and equiaxed zones of the weld material, residual stresses which arise though the thickness of a multi-pass weld and the extraction orientation of the specimen relative to the welding direction. Creep crack growth data obtained from CT specimen testing and analyses is strongly dependent on the material models used (isotropic hardening models, Norton Creep law, Liu/Murakami model, etc.), the path-dependence of the C*-contour integral fracture parameter for certain heterogeneous material configurations and the accurate computation of material constants for damage mechanics models, and the agreement between loading state to the actual stress state of the component to which the CT specimen creep data is applied to. The present study examines typical results and observations from cross-weld specimen and CT specimen creep analyses, identifying the advantages, disadvantages and limitations of each specimen procedure.

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Section: Considerations Of Geometry Of Specimen and Residual Stressesmentioning

confidence: 77%

Section: Ct Specimenmentioning

confidence: 77%

Section: Ct Specimenmentioning

confidence: 99%

Section: Ct Specimenmentioning

confidence: 99%

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Practical considerations of the use of cross-weld and compact tension specimens’ creep data

Petkov

Hyde

2016

The Journal of Strain Analysis for Engineering Design

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“…13 Residual hoop stress variations against distance from the weld centre, along a straight line on the outside surface in the axial direction, after removing the weld crown, and after PWHT with the holding time ranging from 0 to 100 h (A 5 56.8610 228 for stress in megapascals and time in hours; n 5 10.836) associated assessment risks. Induced weaknesses due to the presence of residual stresses can range from possible fabrication or transportation cracking to a faster high-temperature microstructural degradation at peak tensile stress locations in the weld region and HAZ, including the possibility of enhancing early crack growth [26]. Once operating creep conditions are prevalent in a welded power plant pipeline, adverse effects of the residual stress distribution usually become less significant, since high-temperature conditions are likely to reduce stress magnitudes substantially in a relatively short period of time because of creep deformation.…”

Section: Discussionmentioning

confidence: 99%

Finite element simulation of welding and residual stresses in a P91 steel pipe incorporating solid-state phase transformation and post-weld heat treatment

Yaghi

Hyde

Becker

et al. 2008

The Journal of Strain Analysis for Engineering Design

118

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The finite element (FE) method has been applied to simulate residual axial and hoop stresses generated in the weld region and heat-affected zone of an axisymmetric 50-bead circumferentially butt-welded P91 steel pipe, with an outer diameter of 145 mm and wall thickness of 50 mm. The FE simulation consists of a thermal analysis and a sequentially coupled structural analysis. Solid-state phase transformation (SSPT), which is characteristic of P91 steel during welding thermal cycles, has been modelled in the FE analysis by allowing for volumetric changes in steel and associated changes in yield stress due to austenitic and martensitic transformations. Phase transformation plasticity has also been taken into account. The effects of post-weld heat treatment (PWHT) have been investigated, including those of heat treatment holding time. Residual axial and hoop stresses have been depicted through the pipe wall thickness as well as along the outer surface of the pipe. The results indicate the importance of including SSPT in the simulation of residual stresses during the welding of P91 steel as well as the significance of PWHT on stress relaxation.

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Process stress simulation of medium-high carbon steel after hard-face-welding during martensite transformation

Liao

Liu

et al. 2008

Computational Materials Science

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Evaluating creep cracking in welded fracture mechanics specimens

Cited by 6 publications

References 25 publications

Practical considerations of the use of cross-weld and compact tension specimens’ creep data

Practical considerations of the use of cross-weld and compact tension specimens’ creep data

Finite element simulation of welding and residual stresses in a P91 steel pipe incorporating solid-state phase transformation and post-weld heat treatment

Process stress simulation of medium-high carbon steel after hard-face-welding during martensite transformation

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