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Browsing by Author "Paradowska, AM"

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9th Australasian Congress on Applied Mechanics (ACAM 9), University of New South Wales, Sydney, Australia, 27 Nov - 29 Nov 2017
(Engineers Australia, 2017-01) Prusty, BG; Paradowska, AM
The proceedings contain 106 papers. The topics discussed include: hydrofoil manufacture with automated fiber placement; honeycomb energy absorbing device for improved falling object protection system in fire fighting tractors; Bragg-edge elastic strain tomography; a scaled boundary finite element based node-to-node scheme for 2D frictional contact problem; transitional negative stiffness and numerical modeling of failure of particulate material; finite element modeling of high-porosity open-cell metal foams using a digital framework; a comparison of thermoplastic materials prepared by 3D printing and injection molding; on evaluation of fatigue crack front shapes; and numerical analysis of cavitation about marine propellers using a compressible multiphase VOF fractional step method.
Additively manufactured Haynes-282 monoliths containing thin wall struts of varying thicknesses
(Elsevier, 2022-09-01) Lim, B; Chen, H; Nomoto, K; Chen, Z; Saville, AI; Vogel, SC; Clarke, AJ; Paradowska, AM; Reid, M; Primig, S; Liao, XZ; Babu, SS; Breen, AJ; Ringer, SP
Magnitude and distribution of residual stresses in additively manufactured Ni-based superalloys may impact the mechanical performance of as-fabricated parts. Though electron beam powder bed fusion (E-PBF) can produce components with minimal defects and residual stresses compared to laser powder bed fusion and directed energy deposition, variations of them may occur within the complex geometry of a component, due to inherent variations of thermal signatures and the evolution of section modulus along the build direction. This work reveals the residual stress distribution, characterised from neutron diffraction, of an as-fabricated Haynes 282 monolith containing internal cube voids and thin wall struts of varying thicknesses. Complementary local hardness measurements and multi-scale microscopy were used to investigate the geometry-structure-property relationships. Observed variations in hardness were attributed to a combination of type I macro-scale residual stresses and variations in bimodal γ′ precipitation behaviour. The results highlight the influence of residual stresses and microstructure on the mechanical properties of E-PBF Haynes 282. © 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
Aluminothermic welding of rails: Improved qualification and performance under heavy haul conditions
(Railway Technical Society of Australasia, 2014-01-01) Salehi, I; Khodabakhshi, B; Mutton, PJ; Paradowska, AM
Aluminothermic welding continues to be used widely throughout the rail industry, due to its low capital cost and flexibility of use. A range of weld types are available from the two manufacturers who support the Australian market; these vary in terms of collar design, preheating conditions, etc. Single-use crucibles, which are now commonly used, have overcome some of the inherent disadvantages of multi-use crucibles. However the reliability of aluminothermic welds continues to be lower than that of flashbutt welds, particularly under heavy haul conditions where aluminothermic welds are responsible for the majority of rail defects and broken rails. Failure modes in aluminothermic welds can vary depending on the characteristics of the individual weld type and the service conditions, although the majority of failures are associated with fatigue cracking at the top or underside of the rail foot. Other failure modes include fatigue cracking in either web or underhead regions; these modes are strongly dependent on the weld collar design and residual stress levels. Qualification requirements for aluminothermic welds in the current Australian standard include mandatory fatigue testing of the rail foot, and an optional web fatigue test which is generally applied when approving welding procedures for some heavy haul conditions. At present there is no established test procedure for fatigue of the underhead region. Several concurrent activities being undertaken with the support of both consumable manufacturers and some heavy haul rail systems, in conjunction with the Australian Nuclear Science and Technology Organisation (ANSTO), aimed at improving the reliability of aluminothermic welds. These include neutron diffraction measurement of residual stress levels in the critical regions of the weld collar, development of a fatigue test methodology for the underhead region, and an enhanced welder training and audit program which provides the opportunity to address any issues with consumables or equipment in a timely manner. © 2014 Railway Technical Society of Australasia
Application and validity of the Radon transform applied to axisymmetric neutron strain imaging
(Elsevier B. V., 2019-12-15) Kirkwood, HJ; Wensrich, CM; Paradowska, AM; Abbey, B
Next generation pulsed neutron sources and wavelength dispersive imaging detectors are creating new opportunities for strain analysis. One such technique is Bragg edge transmission analysis in which projected measurements of the crystallographic properties of bulk polycrystalline samples are recorded on a time-of-flight area detector. The ability to measure the elastic strain field poses the question of whether it is possible to reconstruct a three-dimensional map of the elastic strain tensor from a set of lower order projection data. Here we present a fundamental exploration of the validity of axisymmetric strain reconstruction algorithms available for inverting Bragg edge data. The results demonstrate that the compatibility of the elastic strain field under investigation is critical in determining which algorithm may be successfully applied. Finally, a more robust approach to Radon transform strain tomography is presented based on the condition of zero total strain. ©2019 Elsevier Ltd.
Assessing carbonation in one-part fly ash/slag geopolymer mortar: Change in pore characteristics using the state-of-the-art technique neutron tomography
(Elsevier, 2020-11-01) Vu, TH; Gowripalan, N; De Silva, P; Paradowska, AM; Garbe, U; Kidd, P; Sirivivatnanon, V
Carbonation has long been recognised as a durability issue attributed to corrosion of steel reinforcement in geopolymer materials. The currently available information, however, is not sufficient to gain a deep understanding of this issue, particularly the facet of the carbonation impact on the pore structure of such materials. This paper, thus, assessed the influence of carbonation on porosity and pore size characteristics of one-part fly ash/slag geopolymer mortar, by using neutron tomography. The cutting-edge thermal neutron tomography used in this study provided the prowess of non-destructive 3D analysis of exploring different regions within geopolymers. The results obtained showed that carbonation in the investigated geopolymer mortars drew their porosity down approximately 30% and shifted pore size regions to smaller pore areas. Other evaluations such as changing pH, carbonation front depth and elemental mapping by scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDS) were also performed in this study, in order to supplement the findings of neutron tomography. © 2020 Elsevier Ltd.
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
Challenges of measuring residual stresses in large girth welded pipe spools by neutron diffraction
(Materials Research Forum LLC, 2016-07-03) Ren, Y; Paradowska, AM; Eren, SE; Wang, B
In this paper, welding induced residual stresses in a welded API 5L X65 girth pipe spools are discussed in as-welded and in local post weld heat treated conditions. Stress measurements were carried out non-destructively using the neutron diffraction technique. For such large-scale components residual stress measurements require significant preparation and planning. First of all, a choice of stress free lattice spacing value, discussed extensively, is of great importance for the evaluation of residual strains and stresses correctly. Besides, the use of a virtual instrument (SSCANSS software) can optimize measurements for distorted or undistorted large components with or without complex details. Moreover, the well-planned “window” cut through the thickness greatly reduced measurement time. A number of points were measured across the weld, HAZ and the parent material. Measurement results showed that residual stresses in the as-welded condition was lower than the yield strength of the material, and significant relaxation was also observed in the post weld heat treated samples. © The Authors
Characterization of the residual strains in iterative laser forming
(Elsevier, 2012-01-01) Knupfer, SM; Paradowska, AM; Kirstein, O; Moore, AJ
In laser forming, thermally induced strains transverse to the laser scan line vary with depth in the material and contribute most significantly to the desired deformation. The through-thickness transverse residual strain distribution was measured by neutron diffraction in laser-formed low carbon steel and aluminium alloy specimens. The specimens were formed with a wide range of laser line energies covering the temperature gradient mechanism (TGM) and shortening or upsetting mechanism (SM), and for single and multi-pass forming (up to 3 laser passes). Below the saturation line energy where the TGM dominates, the gradient of the through-thickness strain distribution was found to increase with increasing line energy and number of laser passes; the gradient decreased again at line energies above the saturation line energy where the efficiency of the TGM decreases. Iterative laser forming can be applied to reduce weld-induced distortions. The peak longitudinal strain measured in the weld seam of a specimen that had been straightened by iterative laser forming was also significantly reduced.(C) 2011 Elsevier B.V.
Corrigendum to “Effects of preheating and carbon dilution on material characteristics of laser-cladded hypereutectoid rail steels” [Mater. Sci. Eng. A 712 (2018) 548–563]
(Elsevier, 2019-01-10) Lai, Q; Abrahams, R; Yan, W; Qiu, C; Mutton, PJ; Paradowska, AM; Fang, X; Soodi, M; Wu, X
The authors regret that the scale bar was missing from Figure 7. This has now been corrected. Fig. 7. Unaffected rail substrate and corresponding HAZ of a typical rail-transverse sections at (a) left gauge corner, (b) middle section, (c) right gauge corner and (d) representative of the longitudinal sections for (i) Group 1-1L, (ii) Group 1-2L, (iii) Group 2-1L & (iv) Group 2-2L. Martensitic morphology (M=martensite) with white etching colour were detected in (c) and (d) of the (i) Group 1-1L and (ii) Group 1-2L. Copyright © 2021 Elsevier B.V.
Critical deposition height for sustainable restoration via laser additive manufacturing
(Springer Nature, 2013-10-03) Paul, S; Singh, R; Yan, W; Samajdar, I; Paradowska, AM; Thool, K; Reid, M
Laser material deposition based restoration of high-value components can be a revolutionary technology in remanufacturing. The deposition process induces residual stresses due to thermomechanical behavior and metallurgical transformations. The presence of tensile residual stresses in the deposited layer will compromise the fatigue life of the restored component. We have developed a novel fully coupled metallurgical, thermal and mechanical (metallo-thermomechanical) model to predict residual stresses and identified a critical deposition height, which ensures compressive residual stresses in the deposited layer. Any lower deposition height will result in tensile residual stresses and higher deposition height will result in excessive dilution (substrate melting). We have validated the model using neutron and micro-focus X-ray diffraction measurements. This study highlights that the critical deposition height corresponds to the minimum cooling rate during solidification. It addresses one of the major outstanding problems of additive manufacturing and paves a way for “science-enabled-technology” solutions for sustainable restoration/remanufacturing. © 2021 Springer Nature Limited
Deep surface rolling for fatigue life enhancement of laser clad aircraft aluminium alloy
(Elsevier, 2014-11-30) Zhuang, W; Liu, Q; Djugum, R; Sharp, PK; Paradowska, AM
Deep surface rolling can introduce deep compressive residual stresses into the surface of aircraft metallic structure to extend its fatigue life. To develop cost-effective aircraft structural repair technologies such as laser cladding, deep surface rolling was considered as an advanced post-repair surface enhancement technology. In this study, aluminium alloy 7075-T651 specimens with a blend-out region were first repaired using laser cladding technology. The surface of the laser cladding region was then treated by deep surface rolling. Fatigue testing was subsequently conducted for the laser clad, deep surface rolled and post-heat treated laser clad specimens. It was found that deep surface rolling can significantly improve the fatigue life in comparison with the laser clad baseline repair. In addition, three dimensional residual stresses were measured using neutron diffraction techniques. The results demonstrate that beneficial compressive residual stresses induced by deep surface rolling can reach considerable depths (more than 1.0 mm) below the laser clad surface. © 2014 Elsevier B.V.
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.
Development of crystallographic-orientation-dependent internal strains around a fatigue-crack tip during overloading and underloading
(Elsevier Science Inc, 2013-05-01) Lee, SY; Huang, EW; Wu, W; Liaw, PK; Paradowska, AM
In-situ neutron diffraction was employed to directly measure the crystallographic-orientation-dependent (i.e. hkl) internal strains as a function of distance from the crack tip on the pre-cracked Hastelloy C-2000 compact-tension specimen. Both in-plane (IP) and through-thickness (TT) strain evolutions for various grain orientations were examined during tensile overloading and compressive underloading cycles. After overloading, underloading and their combination loadings were applied and unloaded, the significantly different {hkl} residual strain profiles were obtained in the vicinity of the crack tip. The load responses of the {200} grain orientation in both the IP and TT directions were more significant than those of any other orientations. It is suggested that the different orientation-dependent strain distributions around the crack tip are caused by the combined effects of elastic and plastic anisotropy of each {hkl} reflection upon loading and the subsequent development of residual stresses generated near the crack tip during unloading as a result of the plastic deformation. © 2013, Elsevier Ltd.
Development of Direct Laser Melting (DLM) deposition system for in-situ use on neutron beam instruments
(Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Baldwin, C; White, R; Paradowska, AM; Booth, N; Davidson, G; D’Adam, TM; Shumack, A; Darmann, F
Direct Laser Melting (DLM) deposition is an additive manufacturing technique in which a high power laser is used to create a melt pool on a workpiece while a jet of metal powder is applied, resulting in localised material deposition. This technique is used in industry for additive repairs, cladding with dissimilar metals, or, in conjunction with a CNC milling machine, as a full-fledged 3D additive fabrication platform. As the prominence of this technology rises, so too does interest in characterising deposition dynamics over a vast parameter space. Neutron beam instruments offer unique capabilities for such characterisation. As part of the NSW Research Attraction and Acceleration Program, ACNS is developing world first sample environment capabilities enabling in-situ laser metal deposition, for use on KOWARI and DINGO beamline. The system will utilise a self-contained motion stage and laser cladding head which will construct a thin wall structure on a user specified substrate, utilising up to two metal powders at a time. Neutron studies of the melt pool or heat affected zone can then be performed during and after printing. This paper will present the technical specifications and capabilities of the system, which will be available to the user community in late 2021. © The authors.
Diffraction-based residual stress mapping of a stress frame of gray iron via vibratory stress relief method
(Frontier Media S.A., 2022-04-07) Chen, SW; Huang, EW; Chiu, SM; Reid, M; Wu, CY; Paradowska, AM; Lam, TN; Wu, YH; Lee, SY; Lu, SC; Chen, SA; Lin, YG; Weng, SC
The role of residual stress is critical, particularly for machine tools demanding accuracy below 1 µm. Although minor stresses are subjected to a tiny area, the applied force can cause devastating distortions on the precision components at this length scale. In this research, we systematically investigated the residual stress in a stress frame of the gray iron used in machine tools using synchrotron X-ray and neutron sources. Through the combination of these techniques, the residual stresses on the surface, inside the bulk, and in average were presented. Comprehensive analysis results shed light on the vibratory stress relief technique, which reduced the residual stresses and stabilized them, even materials undergoing cycling heating. Although compressive stresses are not effectively reduced, this technique is useful in improving the mechanical stability of the materials in machine tools. © 2022 Chen, Huang, Chiu, Reid, Wu, Paradowska, Lam, Wu, Lee, Lu, Chen, Lin and Weng. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).
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 deposition material and heat treatment on wear and rolling contact fatigue of laser cladded rails
(Elsevier, 2018-10-15) Roy, T; Lai, Q; Abrahams, R; Mutton, PJ; Paradowska, AM; Soodi, M; Yan, W
To develop a laser cladding technique for repairing rail surface damages due to rolling contact, wear and rolling contact fatigue characteristics of a set of laser cladded rails were investigated using a roller-on-disc test machine. Three deposition materials 410L, SS420 and Stellite 6, were chosen to clad a premium hypereutectoid steel rail under two different heat treatment processes. In the first heat treatment, only preheating at 350 °C was conducted and in the second heat treatment, preheating at 350 °C, post-heating at 350 °C (1 h) then slow-cooling to room temperature was conducted. Preheating the substrate was insufficient to prevent martensite formation resulting from the rapid cooling rate, whereas post heat treatment was beneficial for refining the lamellar spacing and eliminating martensite formation in the clad layer and heat affected zone. Following the roller-on-disc tests, wear loss was calculated from wear track profiles using a laser optical profilometer. The level of surface degradation, surface cracking and spalling was investigated using an optical microscope. Experimental results revealed that SS420 cladding had the highest wear resistant behaviour but severe surface cracks and spalling were found in the worn area. Stellite 6 cladding showed similar wear resistance as the parent substrate rail and the best fatigue resistance behaviour among the three cladded rail samples. Based on this research, Stellite 6 is the most promising deposition material for repairing rails by laser cladding. © 2018 Elsevier B.V.
Effect of holding time on strain relaxation in high-strength low-alloy steel welds: an in-situ neutron diffraction approach
(Elsevier, 2022-01) Alipooramirabad, H; Paradowska, AM; Reid, M; Ghomaschi, R
In-situ neutron diffraction was employed in the present investigation to study the effects of holding time on the relaxation of residual strains during Post-Weld Heat Treatment (PWHT) for multi-pass High-Strength Low-Alloy (HSLA) steel welds. Different holding time intervals (0.5, 1 and 3 h) were utilized to evaluate and monitor the residual strain relaxation during PWHT. It was found that the holding time has little effects on the strain relaxations as strain relaxations occurs predominantly during the reheating stage of the heat treatment (~80% of strain relaxation). A similar trend is observed for all three holding time arrangements with the high strain relaxation during the reheating stage followed by linear strain relief may confirm the hypothesis that creep (primary and secondary) is responsible for strain relaxation during PWHT. It further confirms the selected soaking temperature of 600 °C has a significant effect on the stress relaxation. This finding is in line with the microstructural characterization studies indicating the formation of sub-grains through polygonization in the Heat Affected Zone (HAZ) and Weld Metal (WM) of the heat treated joints. Ex-situ neutron diffraction which was conducted after PWHT confirmed the in-situ neutron diffraction results and showed slightly higher level of residual stresses for the heat-treated specimen with 1/2 hour holding time (~32% of yield strength of the WM). Furthermore, the tensile, hardness and Charpy impact test results support the notion that a shorter holding time is more beneficial, not only for the cost issues but also for the microstructural and mechanical properties of the welded joints. The findings of this study can be used to optimize the current PWHT codes and standards. It can also be used for the validation studies of the finite element modeling of this process. © 2021 Published by Elsevier Ltd on behalf of The Society of Manufacturing Engineers.
Effect of sheet material properties on residual stress profile in self-pierce riveted joint
(Australian Institute of Nuclear Science and Engineering (AINSE), 2012-11-07) Haque, R; Durandet, Y; Paradowska, AM
Self-Piercing Riveting (SPR) is a high-speed mechanical fastening technique which does not require pre-drilling. During SPR, a tubular rivet is driven through the top sheet, piercing the bottom sheet without breaking through it, accompanied by flaring of the legs in the bottom sheet under the guidance of a suitable die. The rivet material should have adequate hardness to pierce the sheets, and sufficient ductility to deform in the bottom sheet without cracking, thus producing a mechanical interlock between the sheets. An increase in strength or thickness of the ply materials narrows down the operating window in terms of joint quality and performance. It is important to know the residual stress distribution arising from the riveting process, and its dependence on the ply materials properties. to ensure a sound joint. In this study, four different joints consisting of two different hardnesses of materials and two different hardnesses of rivets were examined. Residual stresses were measured on the strain scanner Kowari at ANSTO at selected critical locations. The study revealed that the hardness of the rivet and a ply material influence the magnitude and distribution of compressive residual stress in the rivet joint. It was observed that the maximum compressive residual stress occurred in the rivet leg in the transverse direction relative to plane of sheet. The challenges related to the application of neutron diffraction technique to the measurements of residual stress in the riveted joints are presented and discussed.
Effect of ultrasonic peening on fatigue crack propagation from a weld toe
(International Institute of Welding, 2016-07-10) Hellier, AK; Prusty, BG; Pearce, GM; Reid, M; Paradowska, AM
The objective of this work was to investigate the effect of ultrasonic peening on the fatigue propagation life for a semi-elliptical flaw at a T-butt weld toe. A number of T-butt joints have been fabricated from 10 mm thick A350 grade black mild steel plate. Through-thickness residual stresses at the weld toe have been measured using neutron diffraction for both as-welded and ultrasonically peened joints. Ultrasonic peening is relatively cheap, can be applied in-situ and offers significant improvements in the lifespan of welded components when applied correctly. Numerical analyses were conducted using BDKH stress intensity and HBC stress distribution parametric equations in conjunction with the Paris Law and Forman Equation fatigue crack growth models.

Browsing by Author "Paradowska, AM"

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