Mechanics of Advanced Materials and Structures, Jun 14, 2021
With the development of additive manufacturing (AM), research interest is currently focused on la... more With the development of additive manufacturing (AM), research interest is currently focused on lattice structures development due to their interesting mechanical properties. It implies the opportun...
In this paper, the surface integrity is studied when machining the aeronautical titanium alloys. ... more In this paper, the surface integrity is studied when machining the aeronautical titanium alloys. Surface roughness, lay, defects, microhardness and microstructure alterations are studied. The result of surface roughness judges that the CVD-coated carbide fails to produce better Ra value than the uncoated. Lay is characterized by cutting speed and feed speed directions. Feed mark, tearing surface, chip layer formation as built up layer (BUL), and deposited microchip are the defects. Microhardness is altered down to 350 microns beneath the machined surface. The first 50 microns is the soft sub-surface caused by thermal softening in ageing process. Microstructure alteration is observed in this sub-surface. Down to 200 microns is the hard sub-surface caused by the cyclic internal work hardening and then it is gradually decreasing to the bulk material hardness. It is concluded that dry machining titanium alloy is possible using uncoated carbide with cutting condition limited to finish or semi-finish for minimizing surface integrity alteration.
The paper presents a special clamp with high precision used in fixing plastic parts on the lower ... more The paper presents a special clamp with high precision used in fixing plastic parts on the lower mold of laminating tools or in prefixing devices. In most of cases in laminating tools is known that to fix a plastic part, in order to be covered with leather, on a heat lower laminating tool with suction cups is not a good idea because of high temperatures and additional systems needs. In solving this aspect was designed a pneumatic clamp with a special nose which fixed the plastic part with high precision. To achieve good results, the design was thoroughly checked in a software platform like COMSOL Multiphysics in terms of temperature and pressure. In this paper are also presented the main steps design, the results of clash assembly analysis, the results of temperature analysis and the results of pressure analysis.
L’objectif de nos travaux de recherches est d’homogénéiser la répartition des vitesses à la sorti... more L’objectif de nos travaux de recherches est d’homogénéiser la répartition des vitesses à la sortie des filières, par la maîtrise et l’optimisation des paramètres géométrique et opératoires. Une procédure d’optimisation, basée sur la méthode de surface de réponse, a été proposée. Toutes les fonctions sont écrites sous une forme explicite en utilisant soit l’approximation diffuse ou l’interpolation Krigeage. Compte tenu de la présence des contraintes non linéaires, un algorithme de type SQP, a été utilisé. Pour localiser l’optimum global avec précision, une procédure d’échantillonnage auto adaptatif de l’espace de recherche a été adoptée. Les résultats d’optimisation mettent en évidence l'intérêt de l’optimisation des paramètres géométriques et opératoires du procédé d’extrusion. Une filière optimisée numériquement pour une gamme différente de polymère a été réalisée et une comparaison expérimentale a permis de valider toute la procédure de simulation et d’optimisation mise en pla...
Biological structures and organisms are determined and optimized to adapt to changes and constrai... more Biological structures and organisms are determined and optimized to adapt to changes and constraints imposed by the environment. The multiple functionalities and properties exhibited by such structures are currently a source of inspiration for designers and engineers. Thus, biomimetic design has been increasingly used in recent years with the intensive development of additive manufacturing to deliver innovative solutions. Due to their multifunctional properties combining softness, high stiffness, and light weight, many potential applications can be seen in the medical, aerospace, and automotive sectors. This paper introduces a biomimetic design and geometric modeling method of 3D-printed lightweight structures based on L-systems generated and distributed along their principal stress lines. Numerical simulations and parametric optimization were conducted with three case studies to demonstrate the relevance and applicability of this method in adapting mechanical structures to various ...
This work deals with the use of a multi-objective optimization method using a hybrid statistic al... more This work deals with the use of a multi-objective optimization method using a hybrid statistic algorithm to improve the Friction Stir Welding of aluminum alloy AA2195-T8. The hybrid approach combines the Taguchi Method with the Relational Grey Analysis technic. In order to optimize the Friction Stir Welding process, the axial force, the rotational tool velocity, the welding velocity and the shoulder diameter were considered as input parameters while the heat input, the maximal temperature value and the Heat Affected Zone length were chosen as output parameters. In this method, the minimization of the heat input, the HAZ length and the temperature value in the stir zone is the main goal. In the process of improving the aluminum welding by FSW, the axial force is the most influential parameter with a contribution of 52.4%, followed by the rotational tool velocity with 37.4%, then the welding velocity with 6.3% and finally the tool diameter with a contribution of 3.6%. The obtained results from the application of three-dimensional numerical thermal model have confirmed the effectiveness and the robustness of the used optimization approach.
A refined beam theory that takes the thickness-stretching into account is presented in this study... more A refined beam theory that takes the thickness-stretching into account is presented in this study for the bending vibratory behavior analysis of thick functionally graded (FG) beams. In this theory, the number of unknowns is reduced to four instead of five in the other approaches. Transverse displacement is expressed through a hyperbolic function and subdivided into bending, shear, and thickness-stretching components. The number of unknowns is reduced, which involves a decrease in the number of the governing equation. The boundary conditions at the top and bottom FG beam faces are satisfied without any shear correction factor. According to a distribution law, effective characteristics of FG beam material change continuously in the thickness direction depending on the constituent’s volume proportion. Equations of motion are obtained from Hamilton’s principle and are solved by assuming the Navier’s solution type, for the case of a supported FG beam that is transversely loaded. The num...
This works deals with the determination of the optimized parameters in friction stir welding (FSW... more This works deals with the determination of the optimized parameters in friction stir welding (FSW) process; this through the determination of the optimal operating conditions (the welding velocity and power) necessary for welding a typical Aluminum alloy material AA2195-T8. A physical model based on the Lagrangian formulation considering a surfacic heat source that moves during the welding process, was applied. The used model predicts the evolution of the thermal field and the maximum temperature over time. Sequential quadratic programming (SQP) was used to solve the constrained multi-objectives optimization problem, in which the objective functions consist to minimize the dissolution time into heat affected zone (HAZ) and the length heat affected zone. In which, the simulated temperature profiles and the natural aging kinetics have been correlated to predict the hardness profiles in the FSW workpiece. The good agreement between the results of the two approaches would it possible to use the proposed numerical model to predict the thermal field and the maximum value of the temperature. The optimization process has demonstrated its robustness and the main results obtained are: the optimal parameters show a reduction of 13.44% in the temperature value at HAZ compared to the initial case, while a reduction of 46.5% in the dissolution time was recorded. The lower hardness zone in the optimal case retracted to the weld midline, the minimum hardness value at the thermal affected zone increases compared to the initial case.
Mechanics of Advanced Materials and Structures, Jun 14, 2021
With the development of additive manufacturing (AM), research interest is currently focused on la... more With the development of additive manufacturing (AM), research interest is currently focused on lattice structures development due to their interesting mechanical properties. It implies the opportun...
In this paper, the surface integrity is studied when machining the aeronautical titanium alloys. ... more In this paper, the surface integrity is studied when machining the aeronautical titanium alloys. Surface roughness, lay, defects, microhardness and microstructure alterations are studied. The result of surface roughness judges that the CVD-coated carbide fails to produce better Ra value than the uncoated. Lay is characterized by cutting speed and feed speed directions. Feed mark, tearing surface, chip layer formation as built up layer (BUL), and deposited microchip are the defects. Microhardness is altered down to 350 microns beneath the machined surface. The first 50 microns is the soft sub-surface caused by thermal softening in ageing process. Microstructure alteration is observed in this sub-surface. Down to 200 microns is the hard sub-surface caused by the cyclic internal work hardening and then it is gradually decreasing to the bulk material hardness. It is concluded that dry machining titanium alloy is possible using uncoated carbide with cutting condition limited to finish or semi-finish for minimizing surface integrity alteration.
The paper presents a special clamp with high precision used in fixing plastic parts on the lower ... more The paper presents a special clamp with high precision used in fixing plastic parts on the lower mold of laminating tools or in prefixing devices. In most of cases in laminating tools is known that to fix a plastic part, in order to be covered with leather, on a heat lower laminating tool with suction cups is not a good idea because of high temperatures and additional systems needs. In solving this aspect was designed a pneumatic clamp with a special nose which fixed the plastic part with high precision. To achieve good results, the design was thoroughly checked in a software platform like COMSOL Multiphysics in terms of temperature and pressure. In this paper are also presented the main steps design, the results of clash assembly analysis, the results of temperature analysis and the results of pressure analysis.
L’objectif de nos travaux de recherches est d’homogénéiser la répartition des vitesses à la sorti... more L’objectif de nos travaux de recherches est d’homogénéiser la répartition des vitesses à la sortie des filières, par la maîtrise et l’optimisation des paramètres géométrique et opératoires. Une procédure d’optimisation, basée sur la méthode de surface de réponse, a été proposée. Toutes les fonctions sont écrites sous une forme explicite en utilisant soit l’approximation diffuse ou l’interpolation Krigeage. Compte tenu de la présence des contraintes non linéaires, un algorithme de type SQP, a été utilisé. Pour localiser l’optimum global avec précision, une procédure d’échantillonnage auto adaptatif de l’espace de recherche a été adoptée. Les résultats d’optimisation mettent en évidence l'intérêt de l’optimisation des paramètres géométriques et opératoires du procédé d’extrusion. Une filière optimisée numériquement pour une gamme différente de polymère a été réalisée et une comparaison expérimentale a permis de valider toute la procédure de simulation et d’optimisation mise en pla...
Biological structures and organisms are determined and optimized to adapt to changes and constrai... more Biological structures and organisms are determined and optimized to adapt to changes and constraints imposed by the environment. The multiple functionalities and properties exhibited by such structures are currently a source of inspiration for designers and engineers. Thus, biomimetic design has been increasingly used in recent years with the intensive development of additive manufacturing to deliver innovative solutions. Due to their multifunctional properties combining softness, high stiffness, and light weight, many potential applications can be seen in the medical, aerospace, and automotive sectors. This paper introduces a biomimetic design and geometric modeling method of 3D-printed lightweight structures based on L-systems generated and distributed along their principal stress lines. Numerical simulations and parametric optimization were conducted with three case studies to demonstrate the relevance and applicability of this method in adapting mechanical structures to various ...
This work deals with the use of a multi-objective optimization method using a hybrid statistic al... more This work deals with the use of a multi-objective optimization method using a hybrid statistic algorithm to improve the Friction Stir Welding of aluminum alloy AA2195-T8. The hybrid approach combines the Taguchi Method with the Relational Grey Analysis technic. In order to optimize the Friction Stir Welding process, the axial force, the rotational tool velocity, the welding velocity and the shoulder diameter were considered as input parameters while the heat input, the maximal temperature value and the Heat Affected Zone length were chosen as output parameters. In this method, the minimization of the heat input, the HAZ length and the temperature value in the stir zone is the main goal. In the process of improving the aluminum welding by FSW, the axial force is the most influential parameter with a contribution of 52.4%, followed by the rotational tool velocity with 37.4%, then the welding velocity with 6.3% and finally the tool diameter with a contribution of 3.6%. The obtained results from the application of three-dimensional numerical thermal model have confirmed the effectiveness and the robustness of the used optimization approach.
A refined beam theory that takes the thickness-stretching into account is presented in this study... more A refined beam theory that takes the thickness-stretching into account is presented in this study for the bending vibratory behavior analysis of thick functionally graded (FG) beams. In this theory, the number of unknowns is reduced to four instead of five in the other approaches. Transverse displacement is expressed through a hyperbolic function and subdivided into bending, shear, and thickness-stretching components. The number of unknowns is reduced, which involves a decrease in the number of the governing equation. The boundary conditions at the top and bottom FG beam faces are satisfied without any shear correction factor. According to a distribution law, effective characteristics of FG beam material change continuously in the thickness direction depending on the constituent’s volume proportion. Equations of motion are obtained from Hamilton’s principle and are solved by assuming the Navier’s solution type, for the case of a supported FG beam that is transversely loaded. The num...
This works deals with the determination of the optimized parameters in friction stir welding (FSW... more This works deals with the determination of the optimized parameters in friction stir welding (FSW) process; this through the determination of the optimal operating conditions (the welding velocity and power) necessary for welding a typical Aluminum alloy material AA2195-T8. A physical model based on the Lagrangian formulation considering a surfacic heat source that moves during the welding process, was applied. The used model predicts the evolution of the thermal field and the maximum temperature over time. Sequential quadratic programming (SQP) was used to solve the constrained multi-objectives optimization problem, in which the objective functions consist to minimize the dissolution time into heat affected zone (HAZ) and the length heat affected zone. In which, the simulated temperature profiles and the natural aging kinetics have been correlated to predict the hardness profiles in the FSW workpiece. The good agreement between the results of the two approaches would it possible to use the proposed numerical model to predict the thermal field and the maximum value of the temperature. The optimization process has demonstrated its robustness and the main results obtained are: the optimal parameters show a reduction of 13.44% in the temperature value at HAZ compared to the initial case, while a reduction of 46.5% in the dissolution time was recorded. The lower hardness zone in the optimal case retracted to the weld midline, the minimum hardness value at the thermal affected zone increases compared to the initial case.
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