ANSTO :: Browsing by Author "Law, M"

Browsing by Author "Law, M"

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Assessment of residual stress, hardness, and defect tolerance in a tee joint, as-welded and after post-weld heat treatment
(Scientific Surveys Ltd, 2017-03-01) Law, M; Paradowska, AM; Hoye, N; Grace, P
The risk of hydrogen-assisted cold cracking (HACC) is often conflated with the risk of brittle fracture. However, if delayed non-destructive testing (NDT) shows there are no defects, or defects below the critical crack size, then brittle fracture is not possible. Post-weld heat treatment (PWHT) is known to reduce the risk of HACC but is not always possible to perform. To assess the effects of PWHT, the residual stresses and hardness values were measured before and after PWHT to assess the effects of PWHT on HACC susceptibility and on the critical defect sizes. The residual stresses were lower than code-based estimates. PWHT reduced the residual stress and hardness, and increased the critical crack size. Copyright Scientific Surveys Ltd
An assessment of the effect of cutting welded samples on residual stress measurements by chill modelling
(SAGE Publications, 2010-08-01) Law, M; Kirstein, O; Luzin, V
In making residual stress measurements in welds, a common problem is that the samples are often cut before measurement, which may alter the stresses. To estimate the effects of cutting, a simplified method of modelling residual stresses in welds was developed, known as chill modelling, which requires limited material data and no welding process data. The method can be performed with elastic finite element analysis. The method does not predict the value of the stresses, just the relative reduction that occurs after cutting. The method was validated against published synchrotron measurements of welded plates, which were cut and remeasured a number of times. For welded plates only, an empirical equation was developed that predicts the change in stress after cutting. © 2010, SAGE Publications
Crack initiation and crack growth assessment of a high pressure steam chest
(Elsevier, 2011-01) Payten, WM; Wei, T; Snowden, KU; Bendeich, PJ; Law, M; Charman, D
Extensive cracking had occurred in a number of high pressure steam chests. An assessment was undertaken based on the R5 British Energy methodology to assess the components for both creep–fatigue damage initiation and crack growth analysis to determine fitness for purpose. The analysis determined that the remaining base rupture endurance life of the component was greater then 1 million hours, however, due to the start-up and shutdown ramp rates, creep–fatigue damage greater then unity has occurred leading to crack initiation in a number of locations. These cracks were confirmed during internal inspection of the steam chest. A subsequent crack growth analysis determined that the component could safely be returned to service for the expected future life of the station. © 2011, Elsevier Ltd.
Development of a DC-LSND welding process for GMAW on DH-36 steel
(Australian Institute of Nuclear Science and Engineering (AINSE), 2013-11-02) Paradowska, AM; Law, M; Larkin, N; Holder, R; Li, H; Kuzmikova, L; Pan, Z; Norrish, J; Shen, C
The reduction of weld induced distortion has become an important focus of research for the shipbuilding industry with the continuing trend of using thinner plates in the ship's hull and super structure. This paper investigates the use of an active cooling process known as Dynamically Controlled—Low Stress No Distortion (DC-LSND) Welding on medium thickness (5 to 6 mm) DH-36 steel. Thermal profiles are obtained. Hardness, distortion and residual stress measurements are also achieved. Results show that the application of a localized cryogenic cooling source trailing the welding arc can significantly reduce weld induced distortion and residual stress using the GMAW process. And welds done by DC-LSND process show a hardening and brittle tendency. The effect of forced cooling on the weld microstructure is also observed.
Effect of cladding direction on residual stress distribution in laser cladded rails
(Zenodo, 2018-01-01) Roy, T; Paradowska, AM; Abrahams, R; Lai, Q; Law, M; Mutton, PJ; Soodi, M; Yan, W
In this investigation, a laser cladding process with a powder feeding was used to deposit stainless steel 410L (high strength, excellent resistance to abrasion and corrosion, and great laser compatibility) onto railhead (higher strength, heat treated hypereutectoid rail grade manufactured in accordance with the requirements of European standard EN 13674 Part 1 for R400HT grade), to investigate the development and controllability of process-induced residual stress in the cladding, heat-affected zone (HAZ) and substrate and to analyse their correlation with hardness profile during two different laser cladding directions (across and along the track). Residual stresses were analysed by neutron diffraction at OPAL reactor, ANSTO. Neutron diffraction was carried out on the samples in longitudinal (parallel to the rail), transverse (perpendicular to the rail) and normal (through thickness) directions with high spatial resolution through the thickness. Due to the thick rail and thin cladding, 4 mm thick reference samples were prepared from every specimen by Electric Discharge Machining (EDM). Metallography across the laser claded sample revealed four distinct zones: The clad zone, the dilution zone, HAZ and the substrate. Compressive residual stresses were found in the clad zone and tensile residual stress in the dilution zone and HAZ. Laser cladding in longitudinally cladding induced higher tensile stress in the HAZ, whereas transversely cladding rail showed lower tensile behavior. © Creative Commons Attribution 4.0 International License
Effect of residual stress on the integrity of a branch connection
(Elsevier Science Ltd, 2012-08-01) Law, M; Kirstein, O; Luzin, V
A new connection to an existing gas pipeline was made by hot-tapping, welding directly onto a pressurised pipeline. The welds were not post-weld heat treated, causing significant residual stresses. The critical weld had residual stresses determined by neutron diffraction using ANSTO's residual stress diffractometer, Kowari. The maximum measured residual stress (290 MPa) was 60% of the yield strength. The magnitudes of errors from a number of sources were estimated. An integrity assessment of the welded branch connection was performed with the measured residual stress values and with residual stress distributions from the BS 7910 and API 579 analysis codes. Analysis using estimates of residual stress from API 579 overestimated the critical crack size. © 2012, Elsevier Ltd.
Effect of spatial variation of stress-free lattice spacings on measured residual stresses
(SAGE Publications, 2011-11-01) Law, M; Luzin, V
When neutron diffraction is used to measure residual stresses, estimates of the unstressed lattice spacing (d(0)) are often required. These are generally measured on a sample that is considered representative of the component. In the case of welded samples, the possibility of variation in weld shape between the d(0) sample and the area where stresses are determined must be taken into account. To assess this, d(0) values are measured on an area considered representative of the sample, and then are re-measured on a sample cut from the actual strain measurement plane. The residual stresses are re-calculated with these new d(0) values and the results compared to those based on the initial d(0) measurement. Methods of estimating these errors are discussed. The errors in residual stress that arise from the spatial variation of d(0) values are greater than the commonly reported peak fitting errors. These errors can be estimated and should be included in the reported residual stress measurements. Cutting a d(0) sample from the measurement plane makes this a destructive technique. © 2011, SAGE Publications
The effect of the crystallographic texture on intergranular stress corrosion crack paths
(Elsevier, 2014-11) Lavigne, O; Gamboa, E; Luzin, V; Law, M; Giuliani, M; Costin, W
Intergranular stress corrosion cracking (IGSCC) crack paths usually travel perpendicular to the applied load direction. Some instances of crack paths propagating in directions away from the perpendicular have been observed in low carbon steels. This study shows that the crystallographic texture is a critical factor that drives the IGSCC crack path. Residual shear strain induced by shear texture (induced by rolling processes) explains the inclination of the cracks at a certain depth and the continuous propagation of the cracks along the transverse directions. The residual strains coming from the manufacturing processes determine the crack propagation paths. © 2014, Elsevier B.V.
Effects of cutting and specimen size on neutron measurement of residual stresses
(Insitute of Physics, 2010-12-16) Law, M; Luzin, V; Kirstein, O
To perform neutron residual stress measurements it is often necessary to cut samples to a manageable size. The effects of cutting a girth welded pipe were investigated with analytical methods and finite element analysis. The effect of cutting on measured stresses was calculated. A simplified method of modelling residual stresses in welds, "chill modelling", is introduced. In ring slitting a cut is made in the axial direction and the deformation is maeesured. The change in elastic stress can be calculated and added to neutron diffraction measurements made on a cut ring to calculate the original stresses. Residual stress measurements were performed to validate the ring slitting correction using ANSTO's residual stress diffractometer Kowari. © 2010, Insitute of Physics.
Effects of through-thickness stress assumptions on residual stress measurements in welds
(The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Law, M; Gnaupel-Herold, T
The three normal stresses have been measured by neutron diffraction for girth welded rings cut from linepipe in a number of thicknesses. The welds are manual metal arc cellulosic electrode welds made in X70 linepipe, these were measured at 5 through thickness positions at 19 locations (from the center of the weld up to 35 mm away from the weld) with a spatial resolution of 1 mm 3. The assumption of zero through thickness stress is a common one in thin walled tubes such as these, however there may be significant local through-thickness stresses depending on the welding technique. These local effects, and the change in measured stresses if these are included, are discussed. © 2005 The Authors
Energy-based approach for the evaluation of low cycle fatigue behaviour of 2.25Cr-1Mo steel at elevated temperature
(Elsevier, 2010-08-20) Callaghan, MD; Humphries, SR; Law, M; Ho, M; Bendeich, PJ; Li, HJ; Yeung, WY
The energy-based approach for the evaluation of low cycle fatigue behaviour of 2.25Cr–1Mo steel at elevated temperature has been investigated and detailed analyses discussed. Plastic strain energy was determined per cycle and found to characterise both crack initiation and propagation to failure regimes. At cyclic stabilisation, average plastic strain energy may be used as a suitable damage parameter and correlations between experimental and predicted data determined. The fatigue toughness to failure of the material was established and the development of a fatigue toughness to crack propagation analysis is presented. © 2010, Elsevier Ltd.
Evaluation of high temperature fatigue behaviour of P22 by miniature specimen testing
(Trans Tech Publications, 2010-01-01) Callaghan, MD; Humphries, SR; Law, M; Li, HJ; Yeung, WY
Miniature specimen testing to evaluate mechanical properties, presents a novel opportunity to undertake structural integrity assessments of in-service power generation components, by removing only a very small volume of material. In this study, high temperature fatigue testing of P22 steel was undertaken and a number of fatigue properties determined using a miniature specimen testing methodology. Good comparisons were observed between fatigue properties determined by miniature specimens and the more established standard-sized specimen testing reported in literature.
High-pH inclined stress corrosion cracking in Australian and Canadian gas pipeline X65 steels
(Taylor & Francis, 2016-05-02) Lavigne, O; Gamboa, E; Griggs, J; Luzin, V; Law, M; Roccisano, A
High-pH stress corrosion cracking is a form of environmental degradation of gas pipeline steels. The crack path is intergranular by nature and typically perpendicular to the maximum applied (hoop) stress (i.e. perpendicular to the pipe outer surface). Some unusual instances of cracks have been observed in Canadian and Australian X65 pipes, where cracks grow away from the perpendicular for considerable distances. This paper presents a comparative study in terms of crack morphology, mechanical properties and crystallographic texture for these Australian and Canadian pipe steels. It is shown that the crack morphologies are quite similar, the main difference being the angle at which the cracks propagate into the material. This difference could be explained by the different through-wall texture and grain aspect ratio measured in the two materials. The interdependency of crack tip plasticity, crack tip electrochemistry and anisotropy in microstructural texture seems to heavily affect the resulting inclined crack path. © 2016 Taylor & Francis
An investigation of residual stress, hardness, and texture on stress corrosion cracking in a gas pipeline
(Trans Tech Publication Ltd, 2014-02) Law, M; Luzin, V; Linton, V; Gamboa, E
Stress Corrosion Cracking (SCC) may be a serious problem in gas pipelines. This work studies the hardness and residual stress profiles in two nominally identical sections of adjacent pipe with similar environment and coating, one of which was affected by detectable SCC and the other that was not. The results show changes in texture, residual stress, plastic strain, and hardness at the pipe surface which may be responsible for the altered susceptibility to SCC. © 2014, Trans Tech Publications.
Measured residual stresses and integrity of pipeline girth welds
(Maney Publishing, 2012-11-01) Law, M; Luzin, V
Pipeline girth welds were made by manual metal arc and semiautomatic flux cored arc welding processes, both without post-weld heat treatment. The residual stresses in these welds were measured by neutron diffraction on ANSTO's strain scanner, Kowari. The two welds had similar residual stress values and profiles. An integrity assessment of the welded branch connection was performed with a conservative estimate based on the measured values of residual stress, and values of residual stress predicted by BS 7910. The critical crack size based on the measurements was almost twice as large, showing the value of these measurements. © 2012, Maney Publishing.
Measurement of residual stress in a welded branch connection and effects on fracture behaviour
(Insitute of Physics, 2010-12-16) Law, M; Luzin, V; Kirstein, O
The branch analysed in this paper was not post weld heat treated, resulting in significant residual stresses. Assessment codes assume these to be at, or close to, yield. An integrity assessment of a welded branch connection was carried out using these high assumed residual stresses. The weld then had residual stresses determined by neutron diffraction, performed using ANSTO's residual stress diffractometer, Kowari. The maximum measured residual stress (290 MPa or 60% of yield) was much lower than the yield value assumed by assessment codes. Reanalysing with the actual residual stresses almost doubled the critical crack size, increasing the safety of the connection. © 2010, Insitute of Physics.
Measuring residual stress in parts built using selective laser melting
(Australian Institute of Nuclear Science and Engineering (AINSE), 2013-12-02) Slingsby, T; Paradowska, AM; Law, M; Davies, C; Wu, X
Selective Laser Melting (SLM) is an additive manufacturing technology that allows parts to be created from a laser melting metal powder in layer, rather than traditional methods such a machining and milling which removes waste from a bulk material. It is because of the greater efficiencies presented with this new technology that additive manufacturing is considered to be at the forefront of the third industrial revolution. SLM shows great promise to produce parts with unique geometry, minimal waste and short production times. While processing issues of balling, density and surface finish are gradually being improved, the issues of deformation and residual stress are major problems. For the SLM technology to be utilised, an understanding of the formation and control of residual stresses must be established. As the layer thickness of the manufacturing process is small, approx. 40μ, the techniques for analysing the residual stresses present must be carefully devised. A combination of neutron and synchrotron diffraction is to be used to analyse both macro and micro stresses in parts, utilising the advantages of both technologies. Experimental temperature profile logging and residual stress testing results are used alongside Finite Element Modelling (FEM) to quantify, predict and control these stresses.
Microstructural and mechanical factors influencing high pH stress corrosion cracking susceptibility of low carbon line pipe steel
(Elsevier, 2014-10) Lavigne, O; Gamboa, E; Costin, W; Law, M; Luzin, V; Linton, V
Several adjacent gas pipe sections were obtained from the field. These pipe sections had nominally identical manufacturing, construction, coating and operational conditions. Some sections were unaffected by stress corrosion cracking (SCC), whereas surrounding sections were affected by SCC. Slight differences in mechanical and microstructural properties were found between the two types of section. Residual stress/strain and hardness close to the outer surface of the pipes and high angle boundary fraction values were lower for the non-cracked pipe sections. Predominant 〈1 1 0〉//ND texture was also found at the outer surface of the non-cracked pipe sections. These characteristics lead to a lower crack growth rate in laboratory SCC experiments. These features being mainly a result of the line pipe steel manufacturing operations, appropriate metallurgical processes leading to low residual stress (6.2%YS), relatively low fraction of high angle boundaries (about 0.75) and predominant {1 1 0}〈1 1 0〉 texture in the material (or in the near surface) are expected to greatly improve the stress corrosion cracking resistance of line pipe steels on the field. © 2014, Elsevier Ltd.
Neutron diffraction residual stress measurements of weldments for shipbuilding application
(Australian Institute of Nuclear Science and Engineering (AINSE), 2012-11-15) Shen, C; Paradowska, AM; Larkin, N; Li, H; Pan, Z; Law, M
Pulsed tandem gas metal arc welding (PT-GMAW) has been identified as a welding process potentially capable of increasing productivity and minimising distortion in ship-building. For this study, the PT-GMAW process was used in pulse-pulse mode to butt-weld DH36 steel in order to determine its suitability as a replacement for standard gas-metal-arc welding and submerged-arc welding in naval shipbuilding. Weld residual stresses often lead to increased distortion, and reduction of fatigue life. Quantitative 3D nondestructive neutron diffraction measurements are vital to fully understand the complexity of this welding procedure and their influence on the weld integrity. This paper presents preliminary study of mechanical properties and residual stresses of the welds and their influence on the distortion and fatigue performance. Residual stress measurements were conducted by neutron diffraction at the OPAL reactor on the strain scanner KOWARI. The challenges of the project will be discussed and future planes will be presented.
Neutron diffraction residual stress measurements of welds made with pulsed tandem gas metal arc welding (PT-GMAW)
(Cambridge University Press, 2014-11-10) Paradowska, AM; Larkin, N; Li, H; Pan, Z; Shen, C; Law, M
Pulsed tandem gas metal arc welding (PT-GMAW) is being developed to increase productivity and minimise weld-induced distortion in ship-building. The PT-GMAW process was used in pulse–pulse mode to butt-weld two different strength and thickness steels; the residual stress and hardness profiles of the welds are reported and correlated. © International Centre for Diffraction Data 2014

Browsing by Author "Law, M"

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