The Experts below are selected from a list of 102 Experts worldwide ranked by ideXlab platform
A K Ariffin - One of the best experts on this subject based on the ideXlab platform.
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Simulation of Crack Propagation in Metal Powder Compaction
International Journal for Computational Methods in Engineering Science and Mechanics, 2006Co-Authors: Suraya Mohd Tahir, A K AriffinAbstract:This paper presents the Fracture criterion of metal powder compact and simulation of the crack initiation and propagation during cold compaction process. Based on the Fracture criterion of rock in compression, a displacement-based finite element model has been developed to analyze Fracture initiation and crack growth in iron powder compact. Estimation of Fracture Toughness Variation with relative density is established in order to provide the Fracture parameter as compaction proceeds. A finite element model with adaptive remeshing technique is used to accommodate changes in geometry during the compaction and Fracture process. Friction between crack faces is modelled using the six-node isoparametric interface elements. The shear stress and relative density distributions of the iron compact with predicted crack growth are presented, where the effects of different loading conditions are presented for comparison purposes.
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Fracture in metal powder compaction
International Journal of Solids and Structures, 2006Co-Authors: Suraya Mohd Tahir, A K AriffinAbstract:This paper presents a preliminary assessment and qualitative analysis on Fracture criterion and crack growth in metal powder compact during the cold compaction process. Based on the Fracture criterion of granular materials in compression, a displacement based finite element model has been developed to analyse Fracture initiation and crack growth in metal powder compact. Approximate estimation of Fracture Toughness Variation with relative density is established in order to provide the Fracture parameter as compaction proceed. A single crack initiated from the boundary of a multi-level component made of iron powder is considered in this work. The finite element simulation of the crack propagation indicates that shear crack grows during the compaction process and propagates in the direction of higher shear stress and higher relative density. This also implies that the crack grows in the direction where the compaction pressure is much higher, which is in line with the conclusion made by previous researchers on shear crack growth in materials under compression. In agreement with reported work by previous researchers, high stress concentration and high density gradient at the inner corner in multi-level component results in Fracture of the component during preparation.
Suraya Mohd Tahir - One of the best experts on this subject based on the ideXlab platform.
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Simulation of Crack Propagation in Metal Powder Compaction
International Journal for Computational Methods in Engineering Science and Mechanics, 2006Co-Authors: Suraya Mohd Tahir, A K AriffinAbstract:This paper presents the Fracture criterion of metal powder compact and simulation of the crack initiation and propagation during cold compaction process. Based on the Fracture criterion of rock in compression, a displacement-based finite element model has been developed to analyze Fracture initiation and crack growth in iron powder compact. Estimation of Fracture Toughness Variation with relative density is established in order to provide the Fracture parameter as compaction proceeds. A finite element model with adaptive remeshing technique is used to accommodate changes in geometry during the compaction and Fracture process. Friction between crack faces is modelled using the six-node isoparametric interface elements. The shear stress and relative density distributions of the iron compact with predicted crack growth are presented, where the effects of different loading conditions are presented for comparison purposes.
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Fracture in metal powder compaction
International Journal of Solids and Structures, 2006Co-Authors: Suraya Mohd Tahir, A K AriffinAbstract:This paper presents a preliminary assessment and qualitative analysis on Fracture criterion and crack growth in metal powder compact during the cold compaction process. Based on the Fracture criterion of granular materials in compression, a displacement based finite element model has been developed to analyse Fracture initiation and crack growth in metal powder compact. Approximate estimation of Fracture Toughness Variation with relative density is established in order to provide the Fracture parameter as compaction proceed. A single crack initiated from the boundary of a multi-level component made of iron powder is considered in this work. The finite element simulation of the crack propagation indicates that shear crack grows during the compaction process and propagates in the direction of higher shear stress and higher relative density. This also implies that the crack grows in the direction where the compaction pressure is much higher, which is in line with the conclusion made by previous researchers on shear crack growth in materials under compression. In agreement with reported work by previous researchers, high stress concentration and high density gradient at the inner corner in multi-level component results in Fracture of the component during preparation.
Patrick S. Nicholson - One of the best experts on this subject based on the ideXlab platform.
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Electrophoretic forming of functionally-graded materials
1997Co-Authors: Partho Sarkar, Someswar Datta, Patrick S. NicholsonAbstract:Electrophoretic deposition (EPD) is a colloidal forming process where electrically charged particles are deposited onto an oppositely-charged electrode from an electrostatically stabilized suspension by the application of a dc electric field. It is a cheap and facile technique to fabricate complicated ceramic shapes. EPD is very effective method to synthesize ceramic/ceramic and metal/ceramic composites, eg.; dispersed, laminar, fibre reinforced, and functionally graded materials (FGM) etc. By EPD it is possible to synthesize step FGMs and continuous profile FGMs. The compositional profile of the FGM can be controlled by deposition current density, second component flow rate, suspension concentration etc. Step and continuous profile Al{sub 2}O{sub 3}/YSZ and continuous profile Al{sub 2}O{sub 3}/MoSi{sub 2}, Al{sub 2}O{sub 3}/Ni and YSZ/Ni fabrication is reported herein. The microstructures of the FGMs produced were characterized by optical/electron microscopy and micro-indentation was used to quantify the Vicker`s hardness and Fracture Toughness Variation across The FGM sections.
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Functionally graded ceramic/ceramic and metal/ceramic composites by electrophoretic deposition
Composites Part B: Engineering, 1997Co-Authors: Partho Sarkar, Someswar Datta, Patrick S. NicholsonAbstract:Constant current electrophoretic deposition (EPD) has been used to synthesise Al2O3/YSZ,Al2O3/MoSi2, A12O3/Ni and YSZ/Ni functionally graded materials (FGM). EPD is a cheap and simple technique to fabricate complicated ceramic shapes. By this technique it is possible to synthesize step FGMs as well as continuous-profile FGMs. The profile can be controlled precisely by controlling the deposition current density, second component flow rate, suspension concentration, etc. The microstructures of the FGMs produced were characterized by optical and electron microcopy and micro-indentation was used to track the Vicker's hardness and Fracture Toughness Variation across the composition profiles.
Andrade Carmen - One of the best experts on this subject based on the ideXlab platform.
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High Strength Steels Fracture Toughness Variation by the Media
2020Co-Authors: Sánchez J., Fullea J., Andrade CarmenAbstract:The stress corrosion cracking process is at this moment an unknown mechanism of deterioration. It is a process that implies the joint action of the media, the presence of corrosion or a surface defect and of stress in the metal. Prestressing tendons can suffer SCC jointly with hydrogen embrittlement which dramatically changes not only the type of Fracture (from ductile to brittle) but also the kinetics of the process leading to unexpected collapses. The metal should be resistant to this type of process which can be characterized by its Toughness and therefore by its damage tolerance. This research shows that the Fracture Toughness change when the steel corrodes, questioning the idea that is an intrinsic characteristic of the material. The reduction in the Fracture Toughness of steel wires when they are in contact to aggressive media involve that the material Fractures with a lower crack depth for the same stress level. That means that the material becomes less damage tolerant, which implies that it is necessary to detect defects of smaller size, as for example, small notch, pits or superficial cracks. In the paper some results of the percentage of decrease of the Toughness of prestressing wires suffering corrosion are presente
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Stress corrosion cracking and Fracture Toughness Variation of High Strength Steels
2020Co-Authors: Sánchez Javier, Fullea J., Andrade CarmenAbstract:The stress corrosion cracking (SCC) process is at present a not fully elucidated mechanism of deterioration. It is a surface process that implies a corrosion and stress synergy, but the most practical consequence is that stress corrosion cracking can modify the mechanical characteristics of the metal causing brittle failure. Previously, we present some results about stress corrosion cracking, crack propagation rate or, even, crack arrest conditions in High Strength Steels. This kind of steels is usually used in prestressed and postensioned structures. These wires are of eutectoid composition and cold drawn. It is well established that failures occur when the wires are in contact with electrolytes of specific compositions while under stress. In the case of concrete, the electrolyte is its pore solution and the stress levels result from the different loads applied due to structural requirements. In this work we suggest some improvements of the Mechanism of SCC based in the Surface Mobility of vacancies on the crack surface proposed by Galvele. Improvements consist in incorporating the electrochemical corrosion as one of the sources for the creation of vacancies and some mechanical effects, both produce synergic effect in the crack propagation rate and they are important for a more comprehensive explanation of the process. On the other hand, the Fracture Toughness change when the steel corrodes, questioning the idea that is an intrinsic characteristic of the material. The reduction in the Fracture Toughness of steel wires when they are in contact to aggressive media involve that the material becomes less damage tolerant, which implies that it is necessary to detect defects of smaller size, as for example, small notch, pits or superficial cracks
Carmen Andrade - One of the best experts on this subject based on the ideXlab platform.
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Stress corrosion cracking and Fracture Toughness Variation of high strength steels
2011Co-Authors: Javier Sánchez-montero, J. Fullea, Carmen AndradeAbstract:The stress corrosion cracking process is at this moment an unknown mechanism of deterioration. It is a process that implies the joint action of the media, the presence of corrosion or a surface defect and of stress in the metal. Prestressing tendons can suffer SCC jointly with hydrogen embrittlement which dramatically changes not only the type of Fracture (from ductile to brittle) but also the kinetics of the process leading to unexpected collapses. The metal should be resistant to this type of process which can be characterized by its Toughness and therefore by its damage tolerance. This research shows that the Fracture Toughness change when the steel corrodes, questioning the idea that is an intrinsic characteristic of the material. The reduction in the Fracture Toughness of steel wires when they are in contact to aggressive media involve that the material Fractures with a lower crack depth for the same stress level. That means that the material becomes less damage tolerant, which implies that it is necessary to detect defects of smaller size, as for example, small notch, pits or superficial cracks. In the paper some results of the percentage of decrease of the Toughness of prestressing wires suffering corrosion are presented.
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Fracture Toughness Variation of Prestressing Steels by Bicarbonate Solutions
Brittle Matrix Composites 8, 2006Co-Authors: Javier Sánchez, J. Fullea, Carmen AndradeAbstract:The stress corrosion cracking process developing in metals is at present an unknown mechanism of deterioration. It is a surface process that implies a corrosion and stress synergy, but the most practical consequence is that stress corrosion cracking can modify the mechanical characteristics of the metal. Due to it leads into brittle faliures, it generally involves high level of uncertainty in the prediction. This research deals with steels for prestressed concrete and has the aim to show that the Fracture Toughness changes when the steel is susceptible to stress corrosion cracking, questioning the idea that the Toughness is an intrinsic characteristic of the material. The reduction in the Fracture Toughness of prestressing steels when they are in contact with aggressive media, involves that the material, for the same stress level, may reach a Fracture having a lower crack size. That means the material becomes less damage tolerant, which implies that it is necessary to develop techniques able to detect defects of smaller size, as for example, small notch, pits or superficial cracks.
