Browsing by Author "Roy, T"
Now showing 1 - 13 of 13
Results Per Page
Sort Options
- ItemEffect 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, WIn 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
- ItemEffect 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, WTo 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.
- ItemEvaluation of the mechanical properties of laser cladded hypereutectoid steel rails(Elsevier B. V., 2019-08-15) Roy, T; Abrahams, R; Paradowska, AM; Lai, Q; Mutton, PR; Soodi, M; Fasuhi, P; Yan, WLocal material properties of the cladding layer, heat affected zone and substrate of laser cladded hypereutectoid steel rails were evaluated by uniaxial tensile tests on miniature specimens. Three laser cladding materials, i.e. 410 L, SS420 and Stellite 6, and two different heat treatment conditions were considered. To examine any possible anisotropic behaviour, specimens machined along the longitudinal and transverse laser cladding directions were tested. All the cladding layers showed similar or higher yield and ultimate tensile strengths, but lower elongation than the non-clad rail. Application of post-heat treatment significantly improved the elongation of all the cladding layer specimens. Elongation increments of 70%, 192% and 90% were respectively obtained from the 410 L, SS420 and Stellite 6 post-heat treated cladding layers. The post-heat treatment also marginally increased the yield and ultimate tensile strengths in this region. The improvement in tensile properties was associated with a more favourable microstructure, which resulted in a more dimpled morphology as depicted in the SEM images of the fractographic analysis of the tested specimens. While other properties are similar, both cladding layer and HAZ specimens showed significant different elongation values between the longitudinal and transverse directions in some cases, which indicates certain anisotropy in those materials’ ductility. © 2019 Elsevier B.V.
- ItemEvidence against solar influence on nuclear decay constants(Elsevier B. V., 2016-10-10) Pommé, S; Stroh, H; Paepen, J; Van Ammel, R; Marouli, M; Altzitzoglou, T; Hult, M; Kossert, K; Nähle, O; Schrader, H; Juget, F; Bailat, CJ; Nedjadi, Y; Bochud, F; Buchillier, T; Michotte, C; Courte, S; van Rooy, MW; van Staden, MJ; Lubbe, J; Simpson, BRS; Fazio, A; De Felice, P; Jackson, TW; van Wyngaardt, WM; Reinhard, MI; Golya, J; Bourke, S; Roy, T; Galea, R; Keightley, JD; Ferreira, KM; Collins, SM; Ceccatelli, A; Unterweger, MP; Fitzgerald, R; Bergeron, DE; Pibida, L; Verheyen, L; Bruggeman, M; Vodenik, B; Korun, M; Chisté, V; Amiot, MNThe hypothesis that proximity to the Sun causes variation of decay constants at permille level has been tested and disproved. Repeated activity measurements of mono-radionuclide sources were performed over periods from 200 days up to four decades at 14 laboratories across the globe. Residuals from the exponential nuclear decay curves were inspected for annual oscillations. Systematic deviations from a purely exponential decay curve differ from one data set to another and are attributable to instabilities in the instrumentation and measurement conditions. The most stable activity measurements of alpha, beta-minus, electron capture, and beta-plus decaying sources set an upper limit of 0.0006% to 0.008% to the amplitude of annual oscillations in the decay rate. Oscillations in phase with Earth's orbital distance to the Sun could not be observed within a to range of precision. There are also no apparent modulations over periods of weeks or months. Consequently, there is no indication of a natural impediment against sub-permille accuracy in half-life determinations, renormalisation of activity to a distant reference date, application of nuclear dating for archaeology, geo- and cosmochronology, nor in establishing the SI unit becquerel and seeking international equivalence of activity standards. © 2016 The Authors. Published by Elsevier B.V.
- ItemFinite element analysis of thermal cycle in laser cladding for railway repair(Engineers Australia, 2017-01-01) Lai, Q; Abrahams, R; Yan, W; Mutton, PJ; Qiu, C; Paradowska, AM; Soodi, M; Roy, TMaterial degradation in the forms of wear and rolling contact fatigue is one of main hindrances in the development of today's expeditious heavy-haul railway systems. Laser cladding is proposed as a promising repair technique for damaged rail tracks so as to mitigate the material degradation rates and prolong the component service life. This paper reports the influence of laser cladding directions on thermal cycle and the corresponding mircostructures and service performance of laser cladded premium hypereutectoid rails. For two separate cladding directions, thermal information of pre-, during and post-laser treatment on three dimensional 68 kg rail models was simulated via ANSYS platform. Furthermore, microstructural characteristics of the actual rails under the analogous processing conditions were assessed via optical microscopy. Potential mechanical and tribological properties were characterized by Vickers indentation. The unified correlations between the measured properties and observed microstructural features were acquired. The reasons for the formation of martensite renowned for great cracking tendency at certain regions in HAZ were unveiled, thus future prevention of forming martensite can be achieved.
- ItemLaser cladding for railway repair: influence of depositing materials and heat treatment on microstructural characteristics(American Society of Civil Engineers (ASCE), 2017) Lai, Q; Abrahams, R; Mutton, PJ; Qiu, C; Paradowska, AM; Soodi, M; Roy, T; Yan, WThe contact between train wheels and rail tracks is known to induce material degradation in the form of wear, and rolling contact fatigue in the railhead. Laser cladding, a state of the art surface engineering technique, is a promising solution to repair damaged railheads so as to alleviate the rates of degradation and extend the component longevity. In this paper, effects of cladding material and heat treatment on microstructures of laser treated rails is presented. Laser cladding of premium hypereutectoid rail, four different depositing materials, and different heat treatments were investigated. For the preheating length of 400 mm, equal to the cladding length, the formation of martensite in heat affected zone (HAZ) was not hindered by the application of preheating to 350 °C on the rail-longitudinally deposited railhead of the four materials. Consequentially, cracking in the clad and HAZ was expected. An uncracked microstructure with excellent microstructural consistency across the entire rail-longitudinally deposited railhead and its HAZ was established using a heat treatment combination consisting of pre-heating, postheating, and slow cooling, regardless of the depositing materials. © 2018 American Society of Civil Engineers
- ItemMaterial characteristics of laser-cladded hypereutectoid rail steels(Railway Technical Society of Australasia (RTSA); Technical Society of Engineers Australia. , 2018-01-01) Lai, Q; Roy, T; Abrahams, R; Yan, W; Paradowska, AM; Qiu, C; Mutton, PJ; Soodi, MThe impact of preheating conditions and carbon dilution on the microstructural and mechanical properties of laser cladded rails at various number of deposition layers has been investigated for hypereutectoid steel grades typically used under heavy hall conditions. The microstructures in the HAZ showed that formation of martensite, which has a detrimental effect on behaviour in wheel-rail contact, was successfully inhibited by increasing the length of the preheated region using a preheating temperature of 350C. Dilution of carbon from the hypereutectoid substrate was observed and its effect on the microstructures on the 410L ferritic stainless-steel deposits was investigated. The formation of the ferrite in the 410L cladding layers was attributed to the very low carbon content, and no carbide formation was observed on boundaries of the ferritic grains. The thickness of the dilution band was determined to be approximately equal to the thickness of the first cladding layer. Mechanical charaterization of the 410L deposits undertaken in terms of Vickers microhardness was correlated with the observed microstructural morphologies. © 2021 Informit
- ItemOn decay constants and orbital distance to the Sun—part I: alpha decay(IOP Publishing, 2016-11-28) Pommé, S; Stroh, H; Paepen, J; Van Ammel, R; Marouli, M; Altzitzoglou, A; Hult, M; Kossert, K; Nähle, O; Schrader, H; Juget, F; Bailat, C; Nedjadi, Y; Bochud, F; Buchillier, T; Michotte, M; Courte, S; van Rooy, MW; van Staden, MJ; Lubbe, L; Simpson, BRS; Fazio, A; De Felice, D; Jackson, TW; van Wyngaardt, WM; Reinhard, MI; Golya, J; Bourke, S; Roy, T; Galea, R; Keightley, JD; Ferreira, KM; Collins, SM; Ceccatelli, A; Verheyen, L; Bruggeman, M; Vodenik, M; Korun, M; Chisté, V; Amiot, MNClaims that proximity to the Sun causes variation of decay constants at permille level have been investigated for alpha decaying nuclides. Repeated decay rate measurements of 209Po, 226Ra, 228Th, 230U, and 241Am sources were performed over periods of 200 d up to two decades at various nuclear metrology institutes around the globe. Residuals from the exponential decay curves were inspected for annual oscillations. Systematic deviations from a purely exponential decay curve differ in amplitude and phase from one data set to another and appear attributable to instabilities in the instrumentation and measurement conditions. The most stable activity measurements of α decaying sources set an upper limit between 0.0006% and 0.006% to the amplitude of annual oscillations in the decay rate. There are no apparent indications for systematic oscillations at a level of weeks or months. Oscillations in phase with Earth's orbital distance to the sun could not be observed within 10−5–10−6 range precision. © The Authors CC BY 3.0 licence
- ItemOn decay constants and orbital distance to the Sun—part II: beta minus decay(IOP Publishing, 2016-11-28) Pommé, S; Stroh, H; Paepen, J; Van Ammel, R; Marouli, M; Altzitzoglou, A; Hult, M; Kossert, K; Nähle, O; Schrader, H; Juget, F; Bailat, C; Nedjadi, Y; Bochud, F; Buchillier, T; Michotte, M; Courte, S; van Rooy, MW; van Staden, MJ; Lubbe, L; Simpson, BRS; Fazio, A; De Felice, D; Jackson, TW; van Wyngaardt, WM; Reinhard, MI; Golya, J; Bourke, S; Roy, T; Galea, R; Keightley, JD; Ferreira, KM; Collins, SM; Ceccatelli, A; Verheyen, L; Bruggeman, M; Vodenik, M; Korun, M; Chisté, V; Amiot, MNClaims that proximity to the Sun causes variations of decay constants at the permille level have been investigated for beta-minus decaying nuclides. Repeated activity measurements of 3H, 14C, 60Co, 85Kr, 90Sr, 124Sb, 134Cs, 137Cs, and 154Eu sources were performed over periods of 259 d up to 5 decades at various nuclear metrology institutes. Residuals from the exponential decay curves were inspected for annual oscillations. Systematic deviations from a purely exponential decay curve differ in amplitude and phase from one data set to another and appear attributable to instabilities in the instrumentation and measurement conditions. Oscillations in phase with Earth's orbital distance to the Sun could not be observed within 10−4–10−5 range precision. The most stable activity measurements of β− decaying sources set an upper limit of 0.003%–0.007% to the amplitude of annual oscillations in the decay rate. There are no apparent indications for systematic oscillations at a level of weeks or months. © The Authors CC BY 3.0 licence
- ItemOn decay constants and orbital distance to the Sun—part III: beta plus and electron capture decay(IOP Publishing, 2016-11-28) Pommé, S; Stroh, H; Paepen, J; Van Ammel, R; Marouli, M; Altzitzoglou, T; Hult, M; Kossert, K; Nähle, O; Schrader, H; Juget, F; Bailat, C; Nedjadi, Y; Bochud, F; Buchillier, T; Michotte, C; Courte, S; van Rooy, MW; van Staden, MJ; Lubbe, J; Simpson, BRS; Fazio, A; De Felice, P; Jackson, TW; van Wyngaardt, WM; Reinhard, MI; Golya, J; Bourke, S; Roy, T; Galea, R; Keightley, JD; Ferreira, KM; Collins, SM; Ceccatelli, A; Verheyen, L; Bruggeman, M; Vodenik, B; Korun, M; Chisté, V; Amiot, MNThe hypothesis that seasonal changes in proximity to the Sun cause variation of decay constants at permille level has been tested for radionuclides disintegrating through electron capture and beta plus decay. Activity measurements of 22Na, 54Mn, 55Fe, 57Co, 65Zn, 82+85Sr, 90Sr, 109Cd, 124Sb, 133Ba, 152Eu, and 207Bi sources were repeated over periods from 200 d up to more than four decades at 14 laboratories across the globe. Residuals from the exponential nuclear decay curves were inspected for annual oscillations. Systematic deviations from a purely exponential decay curve differ from one data set to another and appear attributable to instabilities in the instrumentation and measurement conditions. Oscillations in phase with Earth's orbital distance to the sun could not be observed within 10−4–10−5 range precision. The most stable activity measurements of β+ and EC decaying sources set an upper limit of 0.006% or less to the amplitude of annual oscillations in the decay rate. There are no apparent indications for systematic oscillations at a level of weeks or months. © The Authors CC BY 3.0 licence
- ItemResidual stress in laser cladded heavy-haul rails investigated by neutron diffraction(Elsevier, 2020-04-01) Roy, T; Paradowska, AM; Abrahams, R; Law, M; Mutton, PJ; Soodi, M; Yan, WResidual stress is one of the critical parameters affecting the fatigue behaviour of tribological components, which can be introduced by a thermo-mechanical process such as laser cladding. In this study, the residual stress distribution of laser cladded rails was evaluated using a neutron diffraction technique. The substrate rail for the laser cladding was hypereutectoid rail steel used in Australian heavy-haul railway track, and the cladding materials were 410L (a low carbon content stainless steel alloy) and Stellite 6 (a Co-based alloy). The cladding materials were selected based on their high wear, corrosion and fatigue resistance properties. This study measured the residual stress in full-scale laser cladded rails where the residual stresses were measured in the cladding layer, heat affected zone (HAZ) and substrate zone of the railhead. A new sample preparation strategy was developed to quantify the residual stresses in the full-scale rails with high spatial resolution. Higher compressive residual stress was found in the cladding layer, which may have resulted from the martensitic transformation occurred in that region. Tensile stresses occurred in the HAZ to a depth of 4 mm, which might be mainly caused by thermal contraction and volumetric change in the microstructure. The addition of a second cladding layer did not significantly affect the magnitude of the residual stresses, but the peak tensile residual stress shifted to a deeper location from the surface, which is beneficial in resisting wear. Post-cladding heat treatment significantly reduced the undesirable high residual stress from the cladding layer and HAZ. © 2019 Elsevier B.V.
- ItemResidual stress measurement in laser cladded rail utilizing neutron diffraction technique(Engineers Australia, 2017-11-27) Roy, T; Paradowska, AM; Abrahams, R; Law, M; Mutton, PJ; Soodi, M; Yan, WThe residual stress distribution of an excellent abrasion and corrosion resistant steel was evaluated to assess the potential of using laser cladding as a repair tool for rail track components. 410L steel powder was used to clad over a head treated rail steel substrate using a 4 kW IPG fibre laser. Pre-heating the substrate before cladding was investigated. Residual stress was measured by using neutron diffraction facility at the OPAL reactor, ANSTO (Australian Nuclear Science and Technology Organisation). A new experimental method was developed to measure residual stress of a small area of interest in large thick component. Residual stress results showed a compressive residual stress at the top surface of virgin and cladded rail. Clad layer was characterised by compressive residual stress and HAZ was characterised by tensile residual stress. A beneficial compressive residual stress was found at the cladding-substrate interface. © 2017 Engineers Australia
- ItemTribological behaviour of laser cladded rail under rolling contact test(American Society of Civil Engineers (ASCE), 2017) Roy, T; Abrahams, R; Lai, Q; Mutton, PJ; Soodi, M; Paradowska, AM; Yan, WWRolling contact fatigue (RCF), a pervasive and insidious problem on all types of railway systems, dominates the cause of maintenance and replacement on heavy-haul rail lines. It also plays a significant role in economic and safety challenge for commuter and metro lines. Intensive research around the world has been taken to improve RCF by introducing different surface modification techniques. Laser cladding has attracted attention because of its advanced and more efficient repairing technique. In this present investigation, influence of laser cladding on wear and RCF of a premium hypereutectoid rail steel, currently used in Australian heavy haul railways, has been studied under a roller-on-disc test rig in laboratory conditions. Rolling test was carried out using a roller made of heat treated harden steel with laser cladded and un-cladded rail steel discs. Micro-hardness of the roller was 820-850 HV5 to minimize plastic deformation and wear of the roller. Considering the real scenario of rail-wheel contacts, tests were run under partial sliding and rolling motion. The maximum contact pressure was similar to that experienced in rail due to rail-wheel contact. Wear resistance of laser cladded specimen was found to be significantly improved compared to non-cladded rail steel. © 1996–2021, American Society of Civil Engineers