The Experts below are selected from a list of 23091 Experts worldwide ranked by ideXlab platform
Muhammad Imran - One of the best experts on this subject based on the ideXlab platform.
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extended gurson tvergaard Needleman model for damage modeling and control in hot forming
Cirp Annals-manufacturing Technology, 2019Co-Authors: Markus Bambach, Muhammad ImranAbstract:Abstract During hot working, internal damage of the workpiece is not only controlled by the stress state, but also by time- and temperature-dependent softening processes such as recovery and recrystallization. These processes may be used to delay or prevent damage initiation and hence to improve part performance. This work proposes an extended Gurson–Tvergaard–Needleman damage model for hot forming which couples softening processes to void formation at inclusions. Based on this model, optimal control problems are solved to find optimal ram speed profiles in hot working reducing damage in the workpiece or reducing process time while controlling damage.
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towards the damage evaluation using gurson tvergaard Needleman gtn model for hot forming processes
AIP Conference Proceedings, 2018Co-Authors: Muhammad Imran, Markus BambachAbstract:In the production of semi-finished metal products, hot forming is used to eliminate the pores and voids from the casting process under compressive stresses and to modify the microstructure for further processing. In the case of caliber and flat rolling processes, tensile stresses occur at certain roll gap ratios which promote pore formation on nonmetallic inclusion. The formation of new pores contributes to ductile damage and reduces the load carrying capacity of the material. In the literature, the damage nucleation and growth during the hot forming process are not comprehensively described. The aim of this study is to understand the damage initiation and growth mechanism during hot forming processes. Hot tensile tests are performed at different temperatures and strain rates for 16MnCrS5 steel. To investigate the influence of geometrical variations on the damage mechanism, specimens with different stress triaxiality ratios are used. Finite element simulations using the Gurson-Tvergaard-Needleman (GTN) damage model are performed to estimate the critical void fraction for the damage initiation and the evolution of the void volume fraction. The results showed that the GTN model underestimates the softening of the material due to the independence of the temperature and the strain rate.In the production of semi-finished metal products, hot forming is used to eliminate the pores and voids from the casting process under compressive stresses and to modify the microstructure for further processing. In the case of caliber and flat rolling processes, tensile stresses occur at certain roll gap ratios which promote pore formation on nonmetallic inclusion. The formation of new pores contributes to ductile damage and reduces the load carrying capacity of the material. In the literature, the damage nucleation and growth during the hot forming process are not comprehensively described. The aim of this study is to understand the damage initiation and growth mechanism during hot forming processes. Hot tensile tests are performed at different temperatures and strain rates for 16MnCrS5 steel. To investigate the influence of geometrical variations on the damage mechanism, specimens with different stress triaxiality ratios are used. Finite element simulations using the Gurson-Tvergaard-Needleman (GTN) da...
Markus Bambach - One of the best experts on this subject based on the ideXlab platform.
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extended gurson tvergaard Needleman model for damage modeling and control in hot forming
Cirp Annals-manufacturing Technology, 2019Co-Authors: Markus Bambach, Muhammad ImranAbstract:Abstract During hot working, internal damage of the workpiece is not only controlled by the stress state, but also by time- and temperature-dependent softening processes such as recovery and recrystallization. These processes may be used to delay or prevent damage initiation and hence to improve part performance. This work proposes an extended Gurson–Tvergaard–Needleman damage model for hot forming which couples softening processes to void formation at inclusions. Based on this model, optimal control problems are solved to find optimal ram speed profiles in hot working reducing damage in the workpiece or reducing process time while controlling damage.
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towards the damage evaluation using gurson tvergaard Needleman gtn model for hot forming processes
AIP Conference Proceedings, 2018Co-Authors: Muhammad Imran, Markus BambachAbstract:In the production of semi-finished metal products, hot forming is used to eliminate the pores and voids from the casting process under compressive stresses and to modify the microstructure for further processing. In the case of caliber and flat rolling processes, tensile stresses occur at certain roll gap ratios which promote pore formation on nonmetallic inclusion. The formation of new pores contributes to ductile damage and reduces the load carrying capacity of the material. In the literature, the damage nucleation and growth during the hot forming process are not comprehensively described. The aim of this study is to understand the damage initiation and growth mechanism during hot forming processes. Hot tensile tests are performed at different temperatures and strain rates for 16MnCrS5 steel. To investigate the influence of geometrical variations on the damage mechanism, specimens with different stress triaxiality ratios are used. Finite element simulations using the Gurson-Tvergaard-Needleman (GTN) damage model are performed to estimate the critical void fraction for the damage initiation and the evolution of the void volume fraction. The results showed that the GTN model underestimates the softening of the material due to the independence of the temperature and the strain rate.In the production of semi-finished metal products, hot forming is used to eliminate the pores and voids from the casting process under compressive stresses and to modify the microstructure for further processing. In the case of caliber and flat rolling processes, tensile stresses occur at certain roll gap ratios which promote pore formation on nonmetallic inclusion. The formation of new pores contributes to ductile damage and reduces the load carrying capacity of the material. In the literature, the damage nucleation and growth during the hot forming process are not comprehensively described. The aim of this study is to understand the damage initiation and growth mechanism during hot forming processes. Hot tensile tests are performed at different temperatures and strain rates for 16MnCrS5 steel. To investigate the influence of geometrical variations on the damage mechanism, specimens with different stress triaxiality ratios are used. Finite element simulations using the Gurson-Tvergaard-Needleman (GTN) da...
Sidahmed Slimane - One of the best experts on this subject based on the ideXlab platform.
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parametric study of the ductile damage by the gurson tvergaard Needleman model of structures in carbon steel a48 ap
Journal of materials research and technology, 2015Co-Authors: Abdelkader Slimane, Benattou Bouchouicha, M Benguediab, Sidahmed SlimaneAbstract:Abstract This part of study is devoted to the numerical simulation of axisymmetric notched specimens in order to study the phenomenon of nucleation by Gurson–Tvergaard–Needleman model (GTN). The numerical simulations were performed to describe the damage of the materials using GTN model, which involves the stress triaxiality. The specimens chosen are somewhat axisymmetric notched (AN): hence, this choice was motivated by the symmetry of these specimens, and also by the existence of notches that make them interesting in the case of fracture mechanics.
Zhihua Du - One of the best experts on this subject based on the ideXlab platform.
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improvement of the Needleman wunsch algorithm
Lecture Notes in Computer Science, 2004Co-Authors: Zhihua DuAbstract:This paper provides a novel approach to improve the Needleman-Wunsch algorithm, one of the most basic algorithms in Protein or DNA sequence pairwise alignment. In the first part, the problem of this algorithm is outlined. Later, a general introduction of related work is described. Finally, a modified Needleman-Wunsch algorithm and experimental results are presented. The importance of this process lies on its effect of keeping common patterns in sequences to be aligned accurately.
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Rough Sets and Current Trends in Computing - Improvement of the Needleman-Wunsch Algorithm
Lecture Notes in Computer Science, 2004Co-Authors: Zhihua DuAbstract:This paper provides a novel approach to improve the Needleman-Wunsch algorithm, one of the most basic algorithms in Protein or DNA sequence pairwise alignment. In the first part, the problem of this algorithm is outlined. Later, a general introduction of related work is described. Finally, a modified Needleman-Wunsch algorithm and experimental results are presented. The importance of this process lies on its effect of keeping common patterns in sequences to be aligned accurately.
S J Yuan - One of the best experts on this subject based on the ideXlab platform.
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analysis of corner filling behavior during tube hydro forming of rectangular section based on gurson tvergaard Needleman ductile damage model
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2015Co-Authors: Weiwei Zhang, X S Wang, S J YuanAbstract:Friction plays an important role in the corner filling behavior during hydro-forming of rectangular section. In order to study the variation in corner filling behavior with internal pressure under the condition of different coefficients of friction, Gurson–Tvergaard–Needleman ductile damage model was used to describe material deformation involving damage evolution. First, an experimental–numerical hybrid method was applied to determine the parameters of critical porosity and failure porosity in Gurson–Tvergaard–Needleman ductile damage model. Second, a model describing the deformation behavior was established, in which the deformation zone was divided into three parts: sticking zone, sliding zone and corner zone. Third, the effect of coefficient of friction on the corner filling process was studied through simulation and experiments. The results show that as the internal pressure increases, the sticking zone starts at certain pressure and increases rapidly until taking over the whole contact length. Stick...
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Analysis of corner filling behavior during tube hydro-forming of rectangular section based on Gurson–Tvergaard–Needleman ductile damage model
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2014Co-Authors: Weiwei Zhang, X S Wang, S J YuanAbstract:Friction plays an important role in the corner filling behavior during hydro-forming of rectangular section. In order to study the variation in corner filling behavior with internal pressure under the condition of different coefficients of friction, Gurson–Tvergaard–Needleman ductile damage model was used to describe material deformation involving damage evolution. First, an experimental–numerical hybrid method was applied to determine the parameters of critical porosity and failure porosity in Gurson–Tvergaard–Needleman ductile damage model. Second, a model describing the deformation behavior was established, in which the deformation zone was divided into three parts: sticking zone, sliding zone and corner zone. Third, the effect of coefficient of friction on the corner filling process was studied through simulation and experiments. The results show that as the internal pressure increases, the sticking zone starts at certain pressure and increases rapidly until taking over the whole contact length. Stick...
