The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
K.s. See - One of the best experts on this subject based on the ideXlab platform.
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the effects of the disposition of sic particles on the Forgeability and mechanical properties of co sprayed aluminium based mmcs
Journal of Materials Processing Technology, 1997Co-Authors: K.s. See, T A DeanAbstract:Abstract An investigation of the Forgeability and mechanical properties of unworked and extruded co-sprayed metal matrix composites (MMCs) is reported in this paper. The materials investigated are mainly co-sprayed particulate SiC reinforced 2014 and 2618 aluminium-based MMCs. A similar powder metallurgy (PM) MMC and a co-sprayed monolithic aluminium alloy which is used as the matrix of one of the MMCs are investigated also for base-line comparisons. Forgeability tests were performed on a mechanical press with cylindrical test billets at temperatures ranging from 250 to 450°C. Tensile tests were performed at room temperature. The Forgeability and some tensile properties of co-sprayed MMCs were found to be affected greatly by a unique metallurgical pattern designated the tree ring structure (TRS). Metallurgical examination showed that the TRS comprises bands with high and low concentrations of SiC particles. Forged and tensile test specimens show that these bands are easy paths for fractures to propagate along. The more homogeneous distribution of the SiC particles in the PM MMC resulted in a Forgeability superior to that of the co-sprayed material.
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The effects of pre-forge processing on Forgeability and mechanical properties of co-sprayed aluminium-based MMCs
Journal of Materials Processing Technology, 1997Co-Authors: K.s. See, Trevor A. DeanAbstract:Abstract Pre-forge processes, comprising either extrusion or uniaxial/triaxial upset forging or pseudo-isostatic forging, were undertaken to reorganise the existing disposition of SiC particles known as TRS and/or eliminate residual porosity in co-sprayed aluminium-based MMCs. The objective of undertaking these processes is to improve Forgeability and mechanical properties. The materials investigated are co-sprayed 2014 and 2618 aluminium alloys reinforced by 15% (volume fraction) of SiC particles. Billets of these materials were pre-forge processed at elevated temperatures and specimens were cut from them for Forgeability and tensile tests performed at 450°C and room temperature, respectively. Forgeability and tensile properties depend on the orientation of the TRS and inherent cluster-pores relative to the direction of induced tensile stresses/strains. The pre-forge processes that increased Forgeability did not, therefore, necessarily have the same effect on tensile properties. Forgeability increased as a result of triaxial/uniaxial upset forging and pseudo isostatic forging. Significant increases in tensile properties were observed in extruded and triaxially upset forged material only.
Fang-guo Zhang - One of the best experts on this subject based on the ideXlab platform.
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Forgeability of Wang-Tang-Li’s ID-Based Restrictive Partially Blind Signature Scheme
Journal of Computer Science and Technology, 2008Co-Authors: Sheng-li Liu, Xiaofeng Chen, Fang-guo ZhangAbstract:Restrictive partially blind signature (RPBS) plays an important role in designing secure electronic cash system. Very recently, Wang, Tang and Li proposed a new ID-based restrictive partially blind signature (ID-RPBS) and gave the security proof. In this paper, we present a cryptanalysis of the scheme and show that the signature scheme does not satisfy the property of unForgeability as claimed. More precisely, a user can forge a valid message-signature pair (ID; msg; info′; σ′) instead of the original one (ID; msg; info; σ), where info is the original common agreed information and info′ ≠ info. Therefore, it will be much dangerous if Wang-Tang-Li's ID-RPBS scheme is applied to the off-line electronic cash system. For example, a bank is supposed to issue an electronic coin (or bill) of $100 to a user, while the user can change the denomination of the coin (bill) to any value, say $100 000 000, at his will.
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on the Forgeability of wang tang li s id based restrictive partially blind signature
IACR Cryptology ePrint Archive, 2007Co-Authors: Sheng-li Liu, Xiaofeng Chen, Fang-guo ZhangAbstract:Restrictive partially blind signature (RPBS) plays an important role in designing secure electronic cash system. Very recently, Wang, Tang and Li proposed a new ID-based restrictive partially blind signature (ID-RPBS) and gave the security proof. In this paper, we present a cryptanalysis of the scheme and show that the signature scheme does not satisfy the property of unForgeability as claimed. More precisely, a user can forge a valid message-signature pair (ID, msg, info, σ) instead of the original one (ID, msg, info, σ), where info is the original common agreed information and info′ 6= info. Therefore, it will be much dangerous if Wang-Tang-Li’s ID-RPBS scheme is applied to the off-line electronic cash system. For example, a bank is supposed to issue an electronic coin (or bill) of $100 to a user, while the user can change the denomination of the coin (bill) to any value, say $100, 000, 000, at his will.
T A Dean - One of the best experts on this subject based on the ideXlab platform.
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the effects of the disposition of sic particles on the Forgeability and mechanical properties of co sprayed aluminium based mmcs
Journal of Materials Processing Technology, 1997Co-Authors: K.s. See, T A DeanAbstract:Abstract An investigation of the Forgeability and mechanical properties of unworked and extruded co-sprayed metal matrix composites (MMCs) is reported in this paper. The materials investigated are mainly co-sprayed particulate SiC reinforced 2014 and 2618 aluminium-based MMCs. A similar powder metallurgy (PM) MMC and a co-sprayed monolithic aluminium alloy which is used as the matrix of one of the MMCs are investigated also for base-line comparisons. Forgeability tests were performed on a mechanical press with cylindrical test billets at temperatures ranging from 250 to 450°C. Tensile tests were performed at room temperature. The Forgeability and some tensile properties of co-sprayed MMCs were found to be affected greatly by a unique metallurgical pattern designated the tree ring structure (TRS). Metallurgical examination showed that the TRS comprises bands with high and low concentrations of SiC particles. Forged and tensile test specimens show that these bands are easy paths for fractures to propagate along. The more homogeneous distribution of the SiC particles in the PM MMC resulted in a Forgeability superior to that of the co-sprayed material.
Trevor A. Dean - One of the best experts on this subject based on the ideXlab platform.
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Incremental deformation and the Forgeability of γ titanium aluminide
International Journal of Machine Tools & Manufacture, 2001Co-Authors: B Pan, D.j. Kim, B.m. Kim, Trevor A. DeanAbstract:Abstract Hot die forging has been undertaken on cube shaped workpieces of cast two-phase γ titanium aluminide. The inhomogeneous as-cast microstructure causes non-uniform deformation and low ductility. Incremental deformation using hot dies aims to break down large α2+γ lamellae in the structure by using an accumulation of small amounts of deformation with interspersed with periods for material recovery. The effect of various forms of incremental deformation, with or without subsequent isothermal forging, on microstructure is discussed. It is shown that the use of hot-die forging to refine microstructure is limited by chilling of the workpiece and loss in ductility.
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The effects of pre-forge processing on Forgeability and mechanical properties of co-sprayed aluminium-based MMCs
Journal of Materials Processing Technology, 1997Co-Authors: K.s. See, Trevor A. DeanAbstract:Abstract Pre-forge processes, comprising either extrusion or uniaxial/triaxial upset forging or pseudo-isostatic forging, were undertaken to reorganise the existing disposition of SiC particles known as TRS and/or eliminate residual porosity in co-sprayed aluminium-based MMCs. The objective of undertaking these processes is to improve Forgeability and mechanical properties. The materials investigated are co-sprayed 2014 and 2618 aluminium alloys reinforced by 15% (volume fraction) of SiC particles. Billets of these materials were pre-forge processed at elevated temperatures and specimens were cut from them for Forgeability and tensile tests performed at 450°C and room temperature, respectively. Forgeability and tensile properties depend on the orientation of the TRS and inherent cluster-pores relative to the direction of induced tensile stresses/strains. The pre-forge processes that increased Forgeability did not, therefore, necessarily have the same effect on tensile properties. Forgeability increased as a result of triaxial/uniaxial upset forging and pseudo isostatic forging. Significant increases in tensile properties were observed in extruded and triaxially upset forged material only.
Rafiq Muhammad - One of the best experts on this subject based on the ideXlab platform.
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Experimental & Numerical Study of the Hot Upsetting of Weld Cladded Billets
'Trans Tech Publications Ltd.', 2013Co-Authors: Wang Jingcai, Rafiq Muhammad, Bigot Régis, Langlois Laurent, Lu HaoAbstract:International audienceThe presented work is dedicated to studying the Forgeability of bimaterial cladded billet. Hot upsetting tests of cylindrical low carbon steel (C15) billets weld cladded (MIG) by stainless steel (SS316L) are experimentally and numerically studied. Upsetting tests with different upsetting ratios are performed in different tribology conditions at 1050°C which is within the better Forgeability temperature range of both substrate and cladding materials[ 1 ]. Slab model and finite-element simulation are conducted to parametrically study the potential Forgeability of the bimaterial cladded billet. The viscoplastic law is adopted to model the friction at the die/billet interface. The friction condition at the die/billet interface has a great impact on the final material distribution, forging effort and cracking occurrence. With Latham and Cockcroft Criterion, the possibility and potential position of cracks could be predicted
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Etude de mise en forme de pièces rechargées par forgeage à chaud
HAL CCSD, 2011Co-Authors: Rafiq MuhammadAbstract:The thesis presented is dedicated to the forming of the weld cladded work pieces. The proposed idea is based on reversing the classical fabrication layout of simple cladded preforms by performing the hot forging process after the weld cladding. The expected benefits are structural refinement of fusion weld solidification by hot forging structure and the ease of automation of MIG cladding on simple preforms. Initially a methodology is setup for the MIG cladding process on simple shapes which is based on two approaches: the statistical experimental study of a single bead cladding and the determination of the optimum bead overlapping by using two overlapping models to setup the link between dilution rate, nominal energy of welding and metallurgical quality of the stainless steel cladding on mild steel substrate. In a second step, the focus is on the hot forging behavior of the cladded work piece. Keeping in view the following three aspects: the intrinsic Forgeability of each material, the Forgeability of the structure composed of the cladding and the substrate part near the interface and the ability to control the overall material distribution during the forming process. This work is the result of an initial feasibility study for reversing the classical manufacturing layout and clad a simple shape and get in shape by hot forging which are considered ideal for obtaining complex shapes. The analytical, numerical and experimental trials are carried out to evaluate the Forgeability of bi-material. The aim is to assess the Forgeability of the multi-material keeping in mind to what extent are we able to find conditions for implementation of the forming that allows us from a rough cladding to get a defect free part with the desired distribution of materials.Le travail de thèse présenté est dédié à la mise en forme des pièces rechargées. L'idée initiale est d'inverser la gamme de fabrication " conventionnelle " consistant à recharger une pièce pré-ébauchée en faisant la mise en forme d'un " lopin " préalablement rechargé. Les avantages escomptés de cette gamme vient dans un premier temps de ce qu'on recharge une forme simple. Ceci devrait faciliter l'automatisation du rechargement et également le amélioration les structures métallurgiques de solidification issues du soudage. Les travaux concernent dans un premier temps la mise en place d'une méthodologie pour la maîtrise de l'opération de rechargement sur des formes simples pour mettre en place le lien entre le taux de dilution, l'énergie nominale de soudage et la qualité métallurgique des revêtements obtenus. Dans un deuxième temps, le travail s'est concentré sur l'étude du comportement en mise en forme des pièces rechargées. La difficulté provient du fait que le comportement du revêtement n'est pas connu. Deux essais de caractérisation ont été étudiés, le pliage à chaud et l'essai d'écrasement. Cette étude a consisté à estimer leur aptitude à évaluer la forgeabilité d'un multi matériaux concernant les trois échelles de forgeabilité: l'échelle du revêtement correspondant au comportement rhéologique du matériau du revêtement incluant sa limite de ductilité à chaud, l'échelle du revêtement incluant le revêtement et la partie proche du substrat et l'échelle de la pièce. Les simulations à partir de modèle analytique ou numérique par éléments finis ainsi que les essais expérimentaux ont permis d'évaluer la forgeabilité du bi-matériau. Les essais expérimentaux de forgeabilité devront également caractériser les transformations métallurgiques se produisant dans le revêtement et le substrat pour qualifier et quantifier le gain potentiel
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Etude de mise en forme de pièces rechargées par forgeage à chaud
2011Co-Authors: Rafiq Muhammad, Bigot Régis, Langlois LaurentAbstract:Le travail de thèse présenté est dédié à la mise en forme des pièces rechargées. L'idée initiale est d'inverser la gamme de fabrication " conventionnelle " consistant à recharger une pièce pré-ébauchée en faisant la mise en forme d'un " lopin " préalablement rechargé. Les avantages escomptés de cette gamme vient dans un premier temps de ce qu'on recharge une forme simple. Ceci devrait faciliter l'automatisation du rechargement et également le amélioration les structures métallurgiques de solidification issues du soudage. Les travaux concernent dans un premier temps la mise en place d'une méthodologie pour la maîtrise de l'opération de rechargement sur des formes simples pour mettre en place le lien entre le taux de dilution, l'énergie nominale de soudage et la qualité métallurgique des revêtements obtenus. Dans un deuxième temps, le travail s'est concentré sur l'étude du comportement en mise en forme des pièces rechargées. La difficulté provient du fait que le comportement du revêtement n'est pas connu. Deux essais de caractérisation ont été étudiés, le pliage à chaud et l'essai d'écrasement. Cette étude a consisté à estimer leur aptitude à évaluer la forgeabilité d'un multi matériaux concernant les trois échelles de forgeabilité: l'échelle du revêtement correspondant au comportement rhéologique du matériau du revêtement incluant sa limite de ductilité à chaud, l'échelle du revêtement incluant le revêtement et la partie proche du substrat et l'échelle de la pièce. Les simulations à partir de modèle analytique ou numérique par éléments finis ainsi que les essais expérimentaux ont permis d'évaluer la forgeabilité du bi-matériau. Les essais expérimentaux de forgeabilité devront également caractériser les transformations métallurgiques se produisant dans le revêtement et le substrat pour qualifier et quantifier le gain potentielThe thesis presented is dedicated to the forming of the weld cladded work pieces. The proposed idea is based on reversing the classical fabrication layout of simple cladded preforms by performing the hot forging process after the weld cladding. The expected benefits are structural refinement of fusion weld solidification by hot forging structure and the ease of automation of MIG cladding on simple preforms. Initially a methodology is setup for the MIG cladding process on simple shapes which is based on two approaches: the statistical experimental study of a single bead cladding and the determination of the optimum bead overlapping by using two overlapping models to setup the link between dilution rate, nominal energy of welding and metallurgical quality of the stainless steel cladding on mild steel substrate. In a second step, the focus is on the hot forging behavior of the cladded work piece. Keeping in view the following three aspects: the intrinsic Forgeability of each material, the Forgeability of the structure composed of the cladding and the substrate part near the interface and the ability to control the overall material distribution during the forming process. This work is the result of an initial feasibility study for reversing the classical manufacturing layout and clad a simple shape and get in shape by hot forging which are considered ideal for obtaining complex shapes. The analytical, numerical and experimental trials are carried out to evaluate the Forgeability of bi-material. The aim is to assess the Forgeability of the multi-material keeping in mind to what extent are we able to find conditions for implementation of the forming that allows us from a rough cladding to get a defect free part with the desired distribution of materials.PARIS-Arts et Métiers (751132303) / SudocCACHAN-ENS (940162301) / SudocSudocFranceF