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Item Metadata only Unraveling dual phase transformations in a CrCoNi medium-entropy alloy(Elsevier, 2021) Chen, Y.; Chen, D.; An, X.; Zhang, Y.; Zhou, Z.; Lu, S.; Munroe, P.; Zhang, S.; Liao, X.; Zhu, T.; Xie, Z.Abstract not available.Item Metadata only Analysis of a rock bolt failed in service(Curran Associates, 2002) Gamboa, E.; Atrens, A.; International Corrosion Congress (15th : 2002 : Granada, Spain)This paper describes a fractographic investigation of a rock bolt failed in service in a NSW colliery and relates the failure to service conditions. Optical microscopy revealed that the fracture surface contained a dark thumbnail shaped area 1.9 mm deep. The rest of the fracture surface was quite shiny. There was no necking or other evidence of plasticity. This fracture appearance is consistent with stress corrosion cracking (SCC) followed by fast brittle fracture. There were secondary cracks also indicative of SCC. SEM observation characterized the SCC surface. This failure analysis has indicated that rock bolts can fail in service in a brittle manner with no prior warning at stresses much lower than their ultimate tensile strength. This represents a new failure mode for a critical mine component, that is critical for mine safety. There is no prior experience with this failure mode, and laboratory work is needed to understand the failure mechanisms. With understanding of the failure mechanism, it will be possible to devise counter-measures.Item Metadata only Characterizing water sorption in 100% solids epoxy coatings(Elsevier Science SA, 2013) Coniglio, N.; Nguyen, K.; Kurji, R.; Gamboa, E.In the present work, water sorption kinetics and equilibrium in 100% solids epoxy coatings are investigated by immersion into distilled water baths from 20 to 85 C (absorption tests) and drying in a furnace between 60 and 85 C (desorption tests). The gravimetric liquid sorption measurements reveal a non-Fickian two-stage diffusion behaviour during both absorption and desorption. The effect of hydrothermal history was also investigated. Cycling the immersion bath temperature increases the saturation values. Alternating sorption-desorption cycles increases the speed of water movement. The hydrothermal-induced coating degradation and the sorption modes are discussed. © 2013 Elsevier B.V. All rights reserved.Item Metadata only Hydrothermal ageing of X65 steel specimens coated with 100% solids epoxy(Elsevier Science SA, 2013) Gamboa, E.; Coniglio, N.; Kurji, R.; Callar, G.In some regions of Australia, epoxy-based coatings are commonly used to isolate the outer steel surface of a buried gas pipeline from the aggressive soil environment, but the rate at which the ability of the coating to exclude the environment deteriorates is unknown. The aim of this project was to investigate the accelerated ageing of a pipeline organic coating using a hydrothermal test as a proxy of pipeline's long-term exposure in the field. API-5L-X65 pipeline steel specimens were coated with a commercial 100% solids epoxy coating and immersed into an 80 C distilled water bath with traces of carbonate-bicarbonate salts whilst electrically connected to an aluminium sacrificial anode. A limited number of specimens were taken out at different predefined ageing times, providing data to evaluate the degradation rate of the coating. Samples aged for 28 weeks were found to have a lower Barcol hardness, greater electrical permeability, and lower dry adhesion strength than non-aged samples. © © 2013 Elsevier B.V. All rights reserved.Item Metadata only Architectural design of diamond-like carbon coatings for long-lasting joint replacements(Elsevier Science BV, 2013) Liu, Y.; Zhao, X.; Zhang, L.; Habibi, D.; Xie, Z.Surface engineering through the application of super-hard, low-friction coatings as a potential approach for increasing the durability of metal-on-metal replacements is attracting significant attention. In this study innovative design strategies are proposed for the development of diamond-like-carbon (DLC) coatings against the damage caused by wear particles on the joint replacements. Finite element modeling is used to analyze stress distributions induced by wear particles of different sizes in the newly-designed coating in comparison to its conventional monolithic counterpart. The critical roles of architectural design in regulating stress concentrations and suppressing crack initiation within the coatings is elucidated. Notably, the introduction of multilayer structure with graded modulus is effective in modifying the stress field and reducing the magnitude and size of stress concentrations in the DLC diamond-like-carbon coatings. The new design is expected to greatly improve the load-carrying ability of surface coatings on prosthetic implants, in addition to the provision of damage tolerance through crack arrest.Item Open Access A realistic assessment of recoverable thermal energy from Australian geothermal reservoirs: a simulation study(Geoscience Australia, 2012) Doonechaly, N.; Rahman, S.; Kotooussov, A.; Australian Geothermal Energy Conference (5th : 2012 : Sydney, Australia)This paper presents an innovative distributed dislocation theory for estimation of change in fracture aperture due fluid induced pressure. The new approach is used to analyze the potential for thermal energy recovery from the Patchawarra geothermal reservoir in Australia. Results of this study show that the time required to stimulate a 500 m2 reservoir rock and sustain commercial flow rate (80 l/s) is much greater (two to three folds) than that previously studied. These results, however, agree well with the experience of existing EGS trials around the world. Thermal stresses induced during the circulation of cold water have a significant bearing on the long term production rate. As thermal drawdown of the rock matrix takes place, tensile thermal stresses are induced which allow residing fractures to dilate and enhance permeability. This gradually increases the fluid velocities between the injector and producer, yielding increasing production rates with time. It was also observed that the maximum thermal energy that can be recovered by use of our current know-how would be as much as 42%.Item Metadata only The economics of applying internal coatings to pump casings(Australasian Corrosion Association (ACA), 2012) Wong, A.; Vince, P.; Gamboa, E.; Annual Conference of the Australasian Corrosion Association (2012 : Melbourne, Victoria)Pumping is one of the major costs in many industries that require liquid transportation. By improving pump efficiency, significant energy and cost savings can be achieved. One of the methods that are used to improve pumping efficiency is to apply an anticorrosion coating to the pump internal surfaces. The coatings trialled in this project are two ceramic filled epoxies from two different suppliers, and an epoxy from a third supplier. These were trialled on two pumps and pump efficiencies were measured over a ten year period. Results are presented and compared. It was found that ceramic filled epoxies achieved the best performance in these examples. It was also found that regular pump testing is an ideal method to evaluate pump performance and can be used to schedule major overhauls. Copyright © (2012) by the Australasian Corrosion Association.Item Metadata only Effects of irradiation and non-enzymatic glycation on the fracture resistance of bovine cortical bone(Engineers Australia, 2012) Fletcher, L.; Codrington, J.; Parkinson, I.; Australasian Congress on Applied Mechanics (7th : 2012 : Adelaide, S.A.)Bone is a complex multi-phase composite having mechanical properties that are strongly dependent on its constituent parts. Components contributing towards the overall mechanical quality of bone include the organic phase (primarily Collagen I) and the inorganic phase (Hydroxyapatite). However, the individual contribution of each of the material phases towards crack propagation and the inherent fracture toughening mechanisms that are observed in bone are not well understood. Therefore, this study aims to investigate the contribution of the organic and inorganic constituents to the fracture resistance of cortical bone. Three treatment methods were selected that independently alter either the organic or inorganic components of cortical bone. The first two treatments effect the organic phase by denaturation of the collagen and formation of natural enzymatic cross-links from exposure to irradiation, and by incubation in a Ribose solution to induce Non-Enzymatic Glycation (NEG). The third treatment alters the inorganic phase by decalcification in ethyl-diamine-tetra-acetic acid (EDTA). Following treatment, the specimens were mechanically tested to obtain the fracture resistance curve as a function of crack growth using the unloading compliance method. To supplement this technique, stages of the crack growth were sequentially labelled using fluorochrome stains to observe the crack path as well as the toughening mechanisms (e.g. ligament bridging). Overall, the results of this study show that the organic phase is responsible for the toughening and fracture resistance behaviour of cortical bone while the inorganic phase contributes to its stiffness. The results of this study also suggest that the formation of natural enzymatic cross-links and protein denaturation due to irradiation are more detrimental to the fracture resistance of cortical bone than the non-enzymatic cross-links formed by NEG.Item Metadata only On the residual opening of cracks with rough faces stimulted by shear slip(Engineers Australia, 2012) Bortolan Neto, L.; Kotooussov, A.; Australasian Congress on Applied Mechanics (7th : 2012 : Adelaide, S.A.)The hydraulic stimulation of fractures has been widely employed worldwide for increasing the productivity of hydrocarbon reservoirs. Many exciting potential applications of this technique, specifically for geothermal reservoirs and coal seam gas (CSG) industries stipulate a strong need for new theoretical models and solutions capable to describe the residual fracture openings after hydraulic stimulations. In this paper a new mechanical model to predict the roughness induced fracture residual opening due to shear slip is developed. It is based on simplified and well established mechanical models of shear slip and contact law of rough surfaces. The solution procedure utilises the distributed dislocation technique, which reduces the governing system to a system of singular equations. The latter is solved using the standard Gauss-Chebyshev quadrature method.Item Metadata only Residual opening of hydraulically stimulated fractures filled with granular particles(Elsevier Science BV, 2012) Bortolan Neto, L.; Kotooussov, A.It is well-known that residual opening of hydraulically stimulated fractures significantly influences the production rate of a well. Despite the numerous studies carried out in the past, there still is a lack of simple mathematical models capable of foreseeing the residual opening of fractures filled with granular particles and subjected to a confining pressure. In this paper a mathematical model based on the Distributed Dislocation Technique was developed and implemented to predict the height of the residual opening of a single crack filled with granular particles after releasing the stimulated hydraulic pressure. The mechanical response of the proppant (granular particles) to the applied pressure in this work was simulated by Terzaghi's classical consolidation model. Two limiting cases were investigated in detail in order to demonstrate the model behaviour and validate the computational technique. The developed model can be further utilised to predict the increase of the production rate during hydraulic fracture stimulations and investigate other important phenomena influencing well productivity, such as, for example, secondary cracking of the fractured media. © 2012 Elsevier B.V.Item Metadata only Steady flow towards a row of collinear hydraulic fractures(Engineers Australia, 2012) Khanna, A.; Kotooussov, A.; Australasian Congress on Applied Mechanics (7th : 2012 : Adelaide, S.A.)Hydraulic fracturing is one of the most effective techniques for increasing the productivity of wells drilled in low permeability reservoirs and for alleviating near-wellbore formation damage. In the analysis of production schemes involving multiple fractured wells, the fracture is often assumed to be elliptical in shape or having a constant thickness. However, the shape of the hydraulic fracture can be more complicated and might significantly affect the productivity of the well system. In this paper, a simple production scheme consisting of a row of fractured wells is considered. The flow is assumed to be steady state and the governing equation is written in terms of the fluid flux entering the fractures. The Gauss-Chebyshev quadrature method is used to obtain a numerical solution for the fluid flux distribution along the fracture. The effects of fracture conductivity, well interference and fracture shape are investigated. It has been found that over a certain range of governing parameters, the shape of the fracture significantly influences the productivity of well system. The results justify the importance of modelling the shape of fractures to simulate the flow in a system of wells using numerical solvers.Item Metadata only Bending strain measurements utilising a scanning laser Doppler vibrometer(Engineers Australia, 2012) Wildy, S.; Kotooussov, A.; Cazzolato, B.; Codrington, J.; Australasian Congress on Applied Mechanics (7th : 2012 : Adelaide, S.A.)This paper presents an investigation into the accuracy of 1D scanning laser Doppler vibrometry in measuring quasi-static surface strain of an aluminium beam specimen, induced by bending. The formulation and experimental setup of the strain measurement technique utilised in this research is presented, as well as the approach used to evaluate the accuracy of the technique. Finally, the affect various parameters have on the accuracy of the technique is presented, including the parameters of the numerical method, spatial interval between measurement points and amplitude of loading.Item Metadata only On the non singular higher order terms in bi-dimensional and three-dimensional engineering applications(Engineers Australia, 2012) Berto, F.; Lazzarin, P.; Kotooussov, A.; Australasian Congress on Applied Mechanics (7th : 2012 : Adelaide, S.A.)In stress analysis of cracked plates, alongside the stress intensity factor which quantifies the singular stress component perpendicular to the crack plane, the role played in crack growth by the constant term parallel to the crack plane, called the T-stress, has been widely investigated by many researchers. There are, however, cases of practical interest where the influence on the stress field of the higher order terms in the series expansion for the crack tip stress field, is not negligible. The main aim of the present investigation is to present and apply a set of equations able to describe more accurately the stress components for those cases where the mode I and mode II stress intensity factors used in combination with the T-stress are unable to characterise with sufficient precision the complete stress field ahead the crack tip. The starting point is represented by the Williams' solution (Williams, 1957) where stresses as expressed in terms of a power series. An example is investigated of a thin-thickness welded lap joint characterized by various joint width to thickness ratios, in the range of d/t ranging from 0.5 to 5. The present paper indicates that the local stresses as well as the strain energy averaged over a control volume which embraces the slip tip, can be evaluated with satisfactory precision only by taking into account a further four terms besides KI, KII and T-stress. Dealing with three-dimensional models the influence of higher order terms tied to mode II loading on the out-ofplane singular mode is investigated here dealing with cracked plates. An accurate analysis of mode II higher order terms and their effects on mode O is carried out by means of a large bulk of 3D numerical models.Item Metadata only Coupled fracture modes in three-dimensional fracture mechanics(Engineers Australia, 2012) Kotooussov, A.; Lazzarin, P.; Berto, F.; Australasian Congress on Applied Mechanics (7th : 2012 : Adelaide, S.A.)Shear and anti-plane loadings of an elastic plate with a through-the-thickness crack generate various singular stress states: primary fracture modes (conventional fracture mode II and III), corner singularities, and coupled fracture modes. Two latter 3D singular states are largely ignored in theoretical and experimental investigations as well as in the current standards and failure assessment codes. It is often implicitly assumed that all three-dimensional effects are negligible and the actual three-dimensional stress state can be adequately approximated by stress components found, for example, from the corresponding classical solutions of the plane theory of elasticity. In this paper we provide an overview of recent 3D studies carried out by the authors, which demonstrate that the account for these coupled modes can totally change the classical view of many fracture phenomena. In particular, this relates to a generation of the coupled fracture modes by shear and anti-plane loading with KII = 0 and KIII = 0, respectively. In these cases the coupled fracture modes dominate the near crack tip stress field and are capable to initiate brittle fracture. In addition, the intensities of the coupled modes are significantly influenced by the thickness of the plate, the effects of which are also disregarded in the classical Linear-Elastic Fracture Mechanics.Item Metadata only Three dimensional finite element mixed fracture mode under anti-plane loading of a crack(Elsevier Science BV, 2012) Kotooussov, A.; Berto, F.; Lazzarin, P.; Pegorin, F.The 3D Finite Element method is applied to mixed fracture under anti-plane loading of a straight through-the-thickness crack in a linear elastic plate. This coupled fracture mode represents one of three-dimensional phenomena, which are currently largely ignored in numerical simulations and failure assessment of structural components weakened by cracks. It arises due to the boundary conditions on the plate free surfaces, which negate the transverse shear stress components corresponding to classical mode III. Instead, a new singular stress state in addition to the well-known 3D corner singularity is generated. This singular stress state (or coupled fracture mode) can affect or contribute significantly to the fracture initiation conditions. The coupled singular mode exists even if the applied anti-plane loading produces no singularities (KIII=0). In this case there is a strong thickness effect on the intensity of the coupled fracture mode. © 2013 Elsevier Ltd.Item Metadata only Revealing microstructural and mechanical characteristics of cold-drawn pearlitic steel wires undergoing simulated galvanization treatment(Elsevier Science SA, 2012) Fang, F.; Hu, X.; Chen, S.; Xie, Z.; Jiang, J.Spheroidization of lamellar cementite often occurs in cold-drawn pearlitic steel wires during galvanizing treatment, leading to the degradation of mechanical properties. Therefore, it is important to understand effects of galvanization process on microstructure and mechanical properties of cold-drawn wires. In this paper, cold-drawn steel wires were fabricated by cold drawing pearlitic steel rods from 13. mm to 6.9. mm in diameter. Thermal annealing at 450 °C was used to simulate galvanizing treatment of steel wires. Tensile strength, elongation and torsion laps of steel rods and wires with, and without, annealing treatment were determined. Microstructure was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, differential scanning calorimetry (DSC) was used to probe the spheroidization temperature of cementite. Experimental results showed that tensile strength of wires increased from 1780. MPa to 1940. MPa for annealing <5. min, and then decreased. Tensile strength became constant for annealing >10. min. Elongation of wires decreased for annealing <2.5. min, and then recovered slightly. It approached a constant value for annealing >5. min. Tensile strength and elongation of wires were both influenced by the strain age hardening and static recovery processes. Notably, torsion laps of wires hardly changed when annealing time was less than 2.5. min, and then decreased rapidly. Its value became constant when the hold time is greater than 10. min. Lamellar cementite began to spheroidize at annealing >2.5. min, starting at the boundary of pearlitic grains, and moving inward. A broad exothermic peak was found at temperatures between 380 °C and 480 °C, resulting primarily from the spheroidization of lamellar cementite, which is responsible for the degradation of torsion property of cold-drawn wires. © 2012 Elsevier B.V.Item Metadata only Enhanced corrosion-resistance in nanocrystalline MoSi₂ films enabled by Cr additions(Elsevier Science SA, 2012) Xu, J.; Lai, D.; Wu, J.; Xie, Z.; Munroe, P.Nanocrystalline C40-structured (Mo 1-xCr x)Si 2 films were engineered onto Ti6Al4V substrates by a double glow discharge plasma technique. The electrochemical behavior of the newly developed films in a 3.5wt.% NaCl solution was characterized by electrochemical techniques including open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy. To gain a deeper understanding of the role of Cr alloying in corrosion resistance, both cohesive energy and Mulliken population of the interatomic bonds in C40 (Mo 1-xCr x)Si 2 were calculated based on the first-principles density-functional theory. © 2012.Item Metadata only Plasticity-induced crack closure model for two collinear cracks in plates of arvitrary thickness(Engineers Australia, 2012) Chang, D.; Kotooussov, A.; Australasian Congress on Applied Mechanics (7th : 2012 : Adelaide, S.A.)Fracture and fatigue assessment of structures weakened by multiple site damage, such as two or more interacting cracks, is currently a very challenging problem. The main objective of this paper is to develop a mathematical model and an approach to investigate fracture behavior of two through-the-thickness collinear cracks of equal length in a plate of arbitrary thickness under remote cycling loading. The developed mathematical model of the problem under consideration is based on the classical strip yield model and plasticity induced crack closure concept. The approach utilises the fundamental solution for an edge dislocation in a plate of finite thickness and the distributed dislocation technique to obtain an effective and accurate solution to the system of governing equations. The obtained results show a very good agreement with the previously published analytical solutions for limiting cases. In particular, the new results confirm that the crack closure behavior and the opening stress variation in the case of two collinear cracks are significantly dependent on the separation gap between two cracks as well as the plate thickness.Item Metadata only Nanocomposite bilayer film for resisting wear and corrosion damage of a Ti-6Al-4V alloy(Elsevier Science SA, 2012) Xu, J.; Liu, L.; Xie, Z.; Munroe, P.A nanocomposite NiSi 2/Ti 5Si 3 bilayer film was engineered onto Ti-6Al-4V alloy by double cathode glow discharge. The outer layer of the resulting film comprised of NiSi 2, having dense and fine-grained (35nm in size) columnar structure with a fraction of nanoscale twin bundles, and the inner layer consisted of equiaxed Ti 5Si 3with a grain size of 50nm. Nanoindentation was carried out on polished cross-sections to measure the elastic modulus and hardness of each layer of the as-deposited film. Scratch tests were undertaken to evaluate the resistance of the as-deposited film to both abrasive and adhesive damage. The dry sliding wear experiments were conducted against ZrO 2 ceramic balls under the applied load ranging from 3.3N to 4.8N at room temperature and 500°C using a ball-on-disc tribometer. Compared with the Ti-6Al-4V alloy, the specific wear rates of the alloy coated with the bilayer film decreased by one order of magnitude at room temperature and were further reduced by one order of magnitude at 500°C. The electrochemical behavior of the coated alloy was characterized by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 5wt.% HCl solution. The results revealed that nanocomposite NiSi 2/Ti 5Si 3 bilayer film exhibited a higher corrosion resistance than the Ti-6Al-4V alloy. © 2012.Item Metadata only Microstructural characterization of sputtered garnet materials and all-garnet magnetic heterostructures: establishing the technology for magnetic photonic crystal fabrication(IOP Publishing Ltd, 2009) Vasiliev, M.; Wo, P.; Alameh, K.; Munroe, P.; Xie, Z.; Kotov, V.; Burkov, V.We have established a set of technologies for the deposition and annealing of magneto-optic ferrite and paramagnetic garnets, as well as multilayer nanostructures which are based on these materials, for use in magnetic photonic crystals. Transmission electron microscope analysis has been performed to investigate the structure of both amorphous and crystallized garnet layers, nanocrystallites and layer interfaces within all-garnet heterostructures.