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Browsing by Author "Reid, M"

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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
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
Defect dynamics in polycrystalline zirconium alloy probed in situ by primary extinction of neutron diffraction
(American Institute Physics, 2013-02-13) Kabra, S; Yan, K; Carr, DG; Harrison, RP; Dippenaar, RJ; Reid, M; Liss, KD
After alpha+beta-zirconium has fully transformed into beta-phase upon heating, the intensities of all beta-Zr Bragg reflections decrease simultaneously as a function of time. It is shown that this effect represents a transition from the kinematic to the dynamic theory of diffraction due to the ever increasing crystal perfection driven by thermal recovery of the system. The best fitting coherent crystallite size of 30 mu m and other microstructural features are verified by in situ laser scanning confocal microscopy. This effect of primary extinction in neutron diffraction has been employed to further investigate the crystal perfection kinetics. Upon further heating, crystal recovery is identified as a process of dislocation annihilation, suffering from lattice friction. Upon cooling, precipitating alpha-Zr induces strain into the perfect beta-crystallites, re-establishing the kinematic diffraction intensities. An Avrami analysis leads to the estimations of nucleation time, consumption of nucleation sites and lower-dimensional growth. Such technique bears great value for further investigation on all metal systems annealed close to the melting temperature. © 2013, American Institute of Physics.
Development of a new powder-bed arc additive manufacturing approach for producing high entropy alloys
(Australian Nuclear Science and Technology Organisation, 2021-11-26) Dong, BS; Muránsky, O; Zhu, Hl; Muránsky, O; Wang, ZY; Reid, M; Li, HJ
High entropy alloys (HEAs) have gained significant attention over the past decade from both academic and industrial communities due to their unique design concept and promising properties. The manufacturing of this emerging material with desired properties remains challenging. Most of previous work utilized conventional vacuum arc melting and casting methods for producing HEAs. However, the disadvantage of typical casting microstructure, columnar dendrite and serious chemical segregation, causes serious deterioration to their mechanical properties. A new powder-bed arc additive manufacturing (PAAM) has been developed at the University of Wollongong for producing HEAs. This approach, with a high level of flexibility for controlling the forming process and the characteristic rapid solidification, enables the tailoring of the microstructure through the process control and the effective reduction of the chemical segregation in these compositionally complexed alloys. Additionally, compared with the laser and electron beam based additive manufacturing, PAAM is advantageous for higher production rate hence it is promising in industrial applications for producing bulk components in shorter period. The production of a eutectic AlCoCrFeNi2.1 HEA using this new PAAM approach will be presented to demonstrate its capability. The characterisation work shows that the produced AlCoCrFeNi2.1 samples have a lamellar microstructure consisting of the soft but ductile face-centered cubic (FCC) phase as well as the hard body-centered-cubic (BCC) phase. The material demonstrates a remarkable combination of excellent ultimate tensile strength (719 MPa) and ductility (elongation ~27%). The current work has demonstrated that the developed PAAM process is promising for producing HEA components with desired properties. © 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).
Dynamic recovery and recrystallization during hot-working in an advanced TiAl alloy
(Carl Hanser Verlag, 2011-01-01) Schmoelzer, T; Liss, KD; Rester, M; Yan, K; Stark, A; Reid, M; Peel, MJ; Clemens, H
Intermetallic TiAl alloys are light-weight high-temperature materials and intended to partly replace Ni based alloys in jet engines. Due to difficult forming operations, component prices are high and limit the possible field of application. During hot-working, recovery and recrystallization effects determine the microstructural evolution and thereby the mechanical properties of the finished part as well as its behavior during deformation. To study the occurring experiments with high-energy X-rays were conducted. By means of this method, the dominating processes were identified. The results were validated through electron back scatter diffraction experiments. © 2011 CARL HANSER VERLAG
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 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.
Effect of ultrasonic peening on residual stresses at a T-butt weld toe
(Materials Research Forum LLC, 2016-07-03) Hellier, AK; Prusty, BG; Pearce, GM; Reid, M; Paradowska, AM; Simons, P
The current paper presents the results of neutron diffraction measurements of the throughthickness residual stress field at the toe of a T-butt weld, made from 10mm thick A350 grade black mild steel plates, after successful ultrasonic peening. A single ultrasonic peening treatment was carried out at the weld toe. Residual stresses were measured using the KOWARI instrument at ANSTO. The neutron diffraction technique was chosen for this study because of its ability to measure three-dimensional residual stress deep within the component at high resolutions. Although the nominal yield stress of the A350 grade plate is 350 MPa the actual yield stress is generally higher, in this case averaging out to about 400 MPa. Ultrasonic peening was highly effective, leading to a residual stress redistribution with a maximum compressive stress of about 250 MPa at the weld toe surface and a maximum tensile stress of 220 MPa, at a depth of almost 3mm into the base plate. The resulting compressive residual stresses at the weld toe surface will almost certainly increase substantially both the fatigue initiation and propagation lives, or may prevent fatigue completely. Since A350 steel is widely used in buildings, bridges and offshore structures, ultrasonic peening shows great promise as an in-situ peening method in order to improve weld fatigue performance. © The Authors
Effects of welding process and heat input on residual stresses in multi-pass welds: application of neutron diffraction
(ICMS Australasia, 2015-07-19) Alipooramirabad, H; Paradowska, AM; Gomashchi, R; Reid, M
High strength low alloy (HSLA) steels are widely used in oil & Gas and pressure vessel applications due to their favorable mechanical properties. The need for safe operation of the welded structures has led to an emphasis on fracture and fatigue-related failure assessments for HSLA steels. It is well known that residual stresses and particularly tensile residual stresses are potentially detrimental to the performance of the structures because they may lead to abrupt crack initiation, stress corrosion cracking, fatigue and other structural failures. Therefore controlling and minimizing the residual stress levels in welded structures are crucial for the longevity and safe operation of these structures. Controlling residual stress levels may be achieved through appropriate selection of pre-welding conditions, in-process parameters and post welding treatments. The current study employed neutron diffraction to investigate the effect of heat input and welding process on the distribution of residual stresses in multi-pass weldments. The outcomes of this study indicate that the utilization of welding procedures with higher heat input weld runs is beneficial in the reduction of the residual stresses The experimental results also indicated that the welding process itself has a significant impact on the residual stress levels. The generated experimental data may also be utilized for validation studies of computational modelling and approaches.
Evolution of residual stress through the processing stages in manufacturing of bore-chilled sand-cast aluminum engine blocks with pressed-in iron liners
(Research Square, 2021-11-30) Stroh, J; Sediako, D; Lombardi, A; Byczynski, G; Reid, M; Paradowska, AM
The cumulative global emissions produced by the automotive industry over the last decade has put a tremendous strain on the environment. Consequently, automotive engineers and manufacturers have been forced to improve the efficiencies of their automobiles which is frequently accomplished by increasing the operating pressure, and therefore temperature, of the combustion engine. Unfortunately, in addition to the rise in operational pressures and temperatures, large tensile residual stresses often accumulate in the cylinder bridges during the casting process of aluminum engine blocks due to the use of cast-in iron cylinder liners, leading to combined stress magnitudes above the strength of the currently used aluminum alloys. Thus, the present study aims to characterize the evolution of residual stress, with application of neutron diffraction, at several critical stages of the manufacturing process of sand-cast aluminum engine blocks that have eliminated the iron cylinder liners from the casting process and replaced them with cylinder bore chills that are pressed-out after the thermal sand reclamation process. The replacement of the iron liners shifted the stress mode from purely tension to purely compression until the bore chills were removed. Following removal of the bore chills, the maximum tensile stress at the top of the cylinder bridge was ~70% lower than the engine’s predecessor which was produced with iron liners. Moreover, in the production-ready state (i.e., T7 heat treated, machined and press-fit liners inserted), the stress mode maintains the partially compressive nature with low magnitudes of tension, thereby lowering the material’s susceptibility to crack growth and propagation. This work is licensed under a Creative Commons Attribution 4.0 International License.
Experimental and modelling approaches to the determination of fatigue crack growth from a structural steel T-butt weld toe
(Engineers Australia, 2017-11-27) Tanulia, V; Prusty, BG; Pearce, GM; Hellier, AK; Li, H; Reid, M; Paradowska, AM
T-butt welded joints are found in many structural steel applications including buildings, bridges and offshore structures and are susceptible to fatigue crack initiation and propagation,which often leads ultimately to fast fracture failure. An example ofthis was the I-35W bridge in Minneapolis, which collapsed in 2007 resulting in 13 fatalities, as shown in Figure 1 [1]. The experimental work for this project was conducted using A350 grade black mild steel plate. An ultrasonic peening treatment was applied to one T-butt specimen to introduce compressive residual stress at the weld toe, in order to reduce the effective fatigue crack propagation rate. The results generated from 3-D FEA modelling plus a FORTRAN program (implementing parametric stress intensity factor and crack propagation equations) will be compared with experimental fatigue test results. © (2017) by Engineers Australia
Experimental investigation of welding stresses in MWIC weldability test
(Materials Research Forum LLC, 2016-07-03) Alipooramirabad, H; Paradowska, AM; Ghomashchi, R; Hoye, N; Reid, M
The use of high-strength steels in the manufacture of energy pipelines, coupled with the transition to larger pipe diameters and greater wall thicknesses, has led to an increased potential for cracking including hydrogen assisted cracking of energy pipelines due to higher constraint induced stresses. In the present study, a modified version of the Welding Institute of Canada (MWIC) restraint test was used to simulate the constraint conditions of full-scale girth welds on energy pipelines, allowing the influence of welding process parameters on crack formation to be assessed. MWIC test samples of X70 grade high-strength low alloy pipeline steel were manually welded using two different welding processes, namely shielded metal arc welding (SMAW) and modified short-arc welding (MSAW). Residual strains, and hence stresses, in these samples were analysed quantitatively using neutron diffraction technique. Overall, results indicate that the modified WIC restraint test produces significant residual stresses and so is effective in constraining the root run and in consequence studying the hydrogen assisted cracking of high-strength pipeline steels. © The Authors
How neutron scattering can help improve advanced manufacturing industry?
(Australian Nuclear Science and Technology Organisation, 2021-11-26) Paradowska, AM; Reid, M; Garbe, A
The Australian Centre for Neutron Scattering at ANSTO has several instruments available for materials science and engineering applications. The instruments have a unique non-destructive ability to determine critical imperfections assist performance of engineering apparatus via radiography and tomography, measure internal residual stresses and textures in crystalline materials, such as metals, alloys, ceramics, and composites. These measurements can be carried out on real engineering components, mock-ups, or test samples with minimal preparation. The results directly impact into optimisation of modern manufacturing processes, improved product reliability, enhanced design performance, reduced production cost, and extended life prediction on significant engineering assets. The versatile team has established a strong record in assisting Australian and international researchers and engineers across a wide range of engineering projects. Over time, we have built an exceptional body of skills, experience and technical expertise, which is on offer to support industrial research and development. This presentation will focus on the challenges and highlights of the application of neutron scattering and imaging to target big and small questions of advanced manufacturing industry. © 2021 The Authors
Hydrostatic compression behavior and high-pressure stabilized β-phase in γ-based titanium aluminide intermetallics
(Multidisciplinary Digital Publishing Institute, 2016-07-15) Liss, KD; Funakoshi, K; Dippenaar, RJ; Higo, Y; Shiro, A; Reid, M; Suzuki, H; Shobu, T; Akita, K
Titanium aluminides find application in modern light-weight, high-temperature turbines, such as aircraft engines, but suffer from poor plasticity during manufacturing and processing. Huge forging presses enable materials processing in the 10-GPa range, and hence, it is necessary to investigate the phase diagrams of candidate materials under these extreme conditions. Here, we report on an in situ synchrotron X-ray diffraction study in a large-volume press of a modern (α2 + γ) two-phase material, Ti-45Al-7.5Nb-0.25C, under pressures up to 9.6 GPa and temperatures up to 1686 K. At room temperature, the volume response to pressure is accommodated by the transformation γ → α2, rather than volumetric strain, expressed by the apparently high bulk moduli of both constituent phases. Crystallographic aspects, specifically lattice strain and atomic order, are discussed in detail. It is interesting to note that this transformation takes place despite an increase in atomic volume, which is due to the high ordering energy of γ. Upon heating under high pressure, both the eutectoid and γ-solvus transition temperatures are elevated, and a third, cubic β-phase is stabilized above 1350 K. Earlier research has shown that this β-phase is very ductile during plastic deformation, essential in near-conventional forging processes. Here, we were able to identify an ideal processing window for near-conventional forging, while the presence of the detrimental β-phase is not present under operating conditions. Novel processing routes can be defined from these findings. © 2016, The Authors
In situ characterization of a Nb and Mo containing γ-TiAl based alloy using neutron diffraction and high-temperature microscopy
(Wiley-VCH Verlag Berlin, 2009-11) Watson, IJ; Liss, KD; Clemens, H; Wallgram, W; Schmoelzer, T; Hansen, TC; Reid, M
In recent times, novel titanium aluminides containing the bcc β-phase at high temperatures are being developed for improved hot-working capabilities, however, predictions of the phase diagrams are merely uncertain. Here we present in-situ neutron studies, which are particularly sensitive to the atomic disorder in the ordered phases. Complementary laser scanning confocal microscopy is employed for in-situ microstructural investigations. © 2009, Wiley-VCH Verlag Berlin
In situ neutron diffraction measurement of strain relaxation in welds during heat treatment
(Taylor & Francis Online, 2016-12-11) Alipooramirabad, H; Paradowska, AM; Lavigne, O; Ghomashchi, R; Reid, M
Neutron diffraction (ND) is commonly used to investigate the stress redistribution before and after post-weld heat treatment (PWHT) in welded structures. However, there is a lack of information on the evaluations of strains during PWHT. The present work employed in situ ND to measure the relaxation of residual strains during conventional PWHT in multi-pass high-strength low-alloy steel welds. It was found that strain relaxation occurs principally during the heating stage of the heat treatment. The findings have important economic bearings and can be used to characterise comparable material combinations and optimise the PWHT process for high-strength low-alloy weld joints. This unique information also provides a valuable benchmark for the finite element modelling of this complex process. © 2021 Informa UK Limited
In situ study of dynamic recrystallization and hot deformation behavior of a multiphase titanium aluminide alloy
(American Institute of Physics, 2009-12-01) Liss, KD; Schmoelzer, T; Yan, K; Reid, M; Peel, MJ; Dippenaar, RJ; Clemens, H
Hot-compression tests were conducted in a high-energy synchrotron x-ray beam to study in situ and in real time microstructural changes in the bulk of a beta-solidifying titanium aluminide alloy. The occupancy and spottiness of the diffraction rings have been evaluated in order to access grain growth and refinement, orientation relationships, subgrain formation, dynamic recovery, and dynamic recrystallization, as well as phase transformations. This method has been applied to an alloy consisting of two coexisting phases at high temperature and it was found that the bcc beta-phase recrystallizes dynamically, much faster than the hcp alpha-phase, which deforms predominantly through crystallographic slip underpinned by a dynamic recovery process with only a small component of dynamic recrystallization. The two phases deform to a very large extent independently from each other. The rapid recrystallization dynamics of the beta-phase combined with the easy and isotropic slip characteristics of the bcc structure explain the excellent deformation behavior of the material, while the presence of two phases effectively suppresses grain growth. © 2009, American Institute of Physics
In-situ characterization of lattice structure evolution during phase transformation of Zr-2.5Nb
(Wiley-Blackwell, 2011-09-01) Yan, K; Carr, DG; Kabra, S; Reid, M; Studer, AJ; Harrison, RP; Dippenaar, RJ; Liss, KD
The alpha-beta phase transformation behavior of Zr-2.5Nb (in mass%) has been characterized in real time during an in situ neutron diffraction experiment. The Zr-2.5Nb material in the current study consists, at room temperature, of alpha-Zr phase (hcp) and two beta phases (bcc), a Nb rich beta-Nb phase and retained, Zr rich, beta-Zr(Nb) phase. It is suggested that this is related to a quench off the equilibrium solubility of Nb atoms in the Zr bcc unit cells. Vegard's law combined with thermal expansion is applied to calculate the composition of the beta-phase, which is compared with the phase diagram, revealing the system's kinetic behavior for approaching equilibrium. © 2011, Wiley-Blackwell.
Influence of tempering and surface grinding on the residual stress of 415SS laser clad hypereutectoid rail components
(Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Kendal, O; Abrahams, R; Paradowska, AM; Reid, M
A growing reliance on critical transport infrastructure combined with the dependence upon railway for mining and mineral export has heightened operational requirements and lead to premature failure of rail components under severe loading conditions caused by plastic deformation, rolling contact fatigue and accelerated wear rates. Rail replacement is a costly and disruptive undertaking therefore in-situ maintenance is necessary for ongoing repairs to keep these extensive railway networks operational. Traditional maintenance techniques such as arc welding can be damaging to the rail and promote undesirable microstructural changes and softening due to the large thermal input. Laser cladding is an emerging regenerative maintenance strategy that utilises a high energy laser to metallurgically bond a deposition layer that imparts superior mechanical and tribological properties to restore the rail profile. Despite the smaller heat affected zone (HAZ) generated from the reduced thermal input, laser cladding produces a complex residual stress state due to thermal gradients, phase changes and solidification shrinkage. It is the combination of residual stress and cyclic wheel-rail contact stresses that govern the rail fatigue behaviour and susceptibility to wear and defect formation, therefore high internal stresses may increase the likelihood of failure. 415SS is a new martensitic stainless steel alloy developed to recondition hypereutectoid rail substrates and contains beneficial compressive stresses in the untempered cladding deposition, determined using neutron diffraction techniques. For in field applications, laser cladding repairs require further tempering and rail grinding procedures to prepare the surface for wheel contact by achieving the required mechanical properties and reducing surface roughness to minimise friction, wear and noise. Both thermal and machining processes alter the post cladding internal stress state which in turn impacts the fatigue behaviour. Non-destructive neutron diffraction has been undertaken on the Kowari strain scanner at ANSTO to assess the effect of post cladding tempering and surface grinding on the residual stress of 415SS clad high carbon rail. The triaxial residual stress distribution was measured after 350oC and 540oC tempering processes and surface grinding to remove 0.5 mm and 1.4 mm from the cladding surface. Strain scanning was also performed on a disc with a 0.4µm surface finish. The research outcomes from this investigation will assist in better understanding the effect of post cladding processes on the rail fatigue behaviour as accurate measurement of the internal stress state is a critical aspect in developing a viable laser cladding maintenance strategy. These findings will be used in conjunction with full microstructural and mechanical property evaluation to determine the influence of cladding repairs on rail performance and identify the most desirable parameters for post cladding procedures to optimise the operation lifetime of rail components.

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