The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform

P Vedrine - One of the best experts on this subject based on the ideXlab platform.

  • analysis of the low temperature dependent behaviour of a ductile adhesive under monotonic tensile compression shear loads
    International Journal of Adhesion and Adhesives, 2012
    Co-Authors: Claudiu Badulescu, Jeanyves Cognard, Romain Creachcadec, P Vedrine
    Abstract:

    Abstract Various models exist to describe the non-linear behaviour of an adhesive in an assembly, taking into account the two stress invariants, hydrostatic stress and von Mises equivalent stress, which can be explained by the nature of the adhesive, i.e., a polymer. The identification of the material parameters of such pressure-dependent constitutive models requires a large experimental database taking into account various tensile–shear loadings. Under quasi-static loadings at low temperature, for a given strain rate range, viscous effects can be neglected, but only a few experimental results are available to model the behaviour of an adhesive in a bonded assembly accurately under realistic loadings. Moreover, edge effects often have a large influence on the mechanical response. This paper presents the possibility of combining the use of a modified Arcan device, which strongly limits the influence of the stress concentrations, with a usual thermal chamber. Experimental results, underlining the temperature-dependent non-linear responses of an adhesive, are presented in the case of various tensile/compression–shear monotonic loadings for a temperature range between 20 °C and −60 °C. The analysis of experimental results, obtained in the load-Displacement Diagram, focuses herein on the modelling of the initial temperature-dependent yield surface; but such results are also useful for the development of the flow rules in the case of pressure-dependent models.

  • Analysis of the low temperature-dependent behaviour of a ductile adhesive under monotonic tensile/compression-shear loads
    International Journal of Adhesion and Adhesives, 2012
    Co-Authors: Claudiu Badulescu, Jeanyves Cognard, Romain Créac'hcadec, P Vedrine
    Abstract:

    Various models exist to describe the non-linear behaviour of an adhesive in an assembly, taking into account the two stress invariants, hydrostatic stress and von Mises equivalent stress, which can be explained by the nature of the adhesive, i.e., a polymer. The identification of the material parameters of such pressure-dependent constitutive models requires a large experimental database taking into account various tensile-shear loadings. Under quasi-static loadings at low temperature, for a given strain rate range, viscous effects can be neglected, but only a few experimental results are available to model the behaviour of an adhesive in a bonded assembly accurately under realistic loadings. Moreover, edge effects often have a large influence on the mechanical response. This paper presents the possibility of combining the use of a modified Arcan device, which strongly limits the influence of the stress concentrations, with a usual thermal chamber. Experimental results, underlining the temperature-dependent non-linear responses of an adhesive, are presented in the case of various tensile/compression-shear monotonic loadings for a temperature range between 20 °C and −60 °C. The analysis of experimental results, obtained in the load-Displacement Diagram, focuses herein on the modelling of the initial temperature-dependent yield surface; but such results are also useful for the development of the flow rules in the case of pressure-dependent models.

J Duszczyk - One of the best experts on this subject based on the ideXlab platform.

  • 3d fem simulation of the whole cycle of aluminium extrusion throughout the transient state and the steady state using the updated lagrangian approach
    Journal of Materials Processing Technology, 2003
    Co-Authors: J Zhou, J Duszczyk
    Abstract:

    Abstract Aluminium extrusion involves the generation of free surface, thermal effects, large deformations and complex geometries. The established finite element method (FEM)-based 3D simulation tools using the updated Lagrangian approach, or the Eulerian approach or the arbitrary Lagrangian Eulerian approach all have limitations in describing the process that develops from the transient state to the steady state before reaching the end when the steady state is disturbed. As a result, the simulation of aluminium extrusion performed so far has been restricted to simple geometries, small length-to-diameter (L/D) ratios, the beginning stage or steady-state conditions. This paper reports on an unprecedented attempt to simulate an entire cycle of aluminium extrusion from a billet with an L/D ratio of 4 to a solid cross-shaped profile, using the DEFORM 3D software based on the updated Lagrangian approach. Simulation successfully predicts a complete extrusion pressure/ram Displacement Diagram that begins with a pressure breakthrough and ends with another pressure rise due to the inhibition of metal flow by the rigid dummy block. The developments of velocity, effective strain and temperature inside the deforming billet indicate that the process is non-steady, even in the steady state, as a result of continuous heat generation and sticking condition at the billet–container interface. The non-steady characteristics are reflected in the expanding deformation zone and shrinking dead metal zone. Simulation also reveals the patterns of the maximum temperature variations in the workpiece and in the tooling, due to heat generation and exchange. Even at a relatively low ram speed of 2 mm/s, the maximum temperature of the workpiece, after an initial steep rise, increases gradually till the end of the process, which may well lead to the occurrence of hot shortness. On the basis of these results, a change of the conventional mode of aluminium extrusion is recommended, which at present operates almost all at a constant ram speed and often begins with a uniform billet temperature across the aluminium extrusion industry in the world.

I L Menezes-sobrinho - One of the best experts on this subject based on the ideXlab platform.

  • Fracture toughness in fibrous materials.
    Physical review. E Statistical nonlinear and soft matter physics, 2001
    Co-Authors: I L Menezes-sobrinho
    Abstract:

    In the present paper, a fiber bundle model in (1+1) dimensions that simulates the rupture process of a fibrous material pulled by an uniaxial force F is analyzed. In this model the load of a broken fiber is shifted in equal portions onto the nearest unbroken fibers. The force-Displacement Diagram is obtained for several traction velocities v and temperatures t. Also, it is shown how the fracture toughness K(c) changes with the traction velocity v and with the temperature t. In this paper it is shown that the rupture process is strongly dependent on temperature t and on velocity v.

Maki K. Rashid - One of the best experts on this subject based on the ideXlab platform.

  • Intelligent design of cutting tools using smart material
    International Journal of Mechanics and Materials in Design, 2006
    Co-Authors: Maki K. Rashid, Khalil Ibrahim Shihab
    Abstract:

    Shaving metal from a workpiece to produce desired geometric shape is carried out in turning machine tool. Attenuating a micro level vibration of a cutting tool using smart materials can save old machines and enhance flexibility in designing new generations of machine tools. The finite element method is employed to investigate structural stiffness, damping, and switching methodology using smart material in tool error attenuation. In this work, a dynamic force model is deployed to investigate the effectiveness of using such technique in toolpost dynamic control. Effects of short and open circuit conditions on tool critical frequencies for different structural stiffness ratios are assessed. In the transient solution for tool tip Displacement, the pulse width modulation (PWM) technique is implemented for smart material activation to compensate for the radial disturbing cutting forces. A Fuzzy Algorithm is developed to control actuator voltage level enhancing improved dynamic performance. The influence of minimum number of PWM cycles in each disturbing force cycle is investigated in controlling the tool error growth. A methodology is developed to utilize toolpost static force–Displacement Diagram to obtain required activation voltage to shrink error under different dynamic operating conditions. Time delay of applied voltage during error attenuation is evaluated at different frequencies.

  • Intelligent design of cutting tools using smart material
    International Journal of Mechanics and Materials in Design, 2006
    Co-Authors: Maki K. Rashid, Khalil Ibrahim Shihab
    Abstract:

    Shaving metal from a workpiece to produce desired geometric shape is carried out in turning machine tool. Attenuating a micro level vibration of a cutting tool using smart materials can save old machines and enhance flexibility in designing new generations of machine tools. The finite element method is employed to investigate structural stiffness, damping, and switching methodology using smart material in tool error attenuation. In this work, a dynamic force model is deployed to investigate the effectiveness of using such technique in toolpost dynamic control. Effects of short and open circuit conditions on tool critical frequencies for different structural stiffness ratios are assessed. In the transient solution for tool tip Displacement, the pulse width modulation (PWM) technique is implemented for smart material activation to compensate for the radial disturbing cutting forces. A Fuzzy Algorithm is developed to control actuator voltage level enhancing improved dynamic performance. The influence of minimum number of PWM cycles in each disturbing force cycle is investigated in controlling the tool error growth. A methodology is developed to utilize toolpost static force–Displacement Diagram to obtain required activation voltage to shrink error under different dynamic operating conditions. Time delay of applied voltage during error attenuation is evaluated at different frequencies.

  • Fuzzy algorithm and structural stiffness in error attenuation of intelligent toolpost
    Journal of Intelligent Manufacturing, 2005
    Co-Authors: Maki K. Rashid
    Abstract:

    Vibration suppressions techniques in cutting tools can save old machines and enhance design flexibility in new manufacturing systems. The finite element method is employed to investigate structural stiffness, damping, and switching methodology under the use of smart material in tool error attenuation. This work discusses the limitations of using lumped mass modeling in toolpost dynamic control. Transient solution for tool tip Displacement is obtained when pulse width modulation (PWM) is used for smart material activation during the compensation of the radial disturbing cutting forces. Accordingly a Fuzzy algorithm is developed to control actuator voltage level toward improved dynamic performance. The required minimum number of PWM cycles in each disturbing force period is investigated to diminish tool error. Time delay of applied voltage during error attenuation is also evaluated. Toolpost static force–Displacement Diagram as required to predict voltage intensities for error reduction is tested under different dynamic operating conditions.

Claudiu Badulescu - One of the best experts on this subject based on the ideXlab platform.

  • analysis of the low temperature dependent behaviour of a ductile adhesive under monotonic tensile compression shear loads
    International Journal of Adhesion and Adhesives, 2012
    Co-Authors: Claudiu Badulescu, Jeanyves Cognard, Romain Creachcadec, P Vedrine
    Abstract:

    Abstract Various models exist to describe the non-linear behaviour of an adhesive in an assembly, taking into account the two stress invariants, hydrostatic stress and von Mises equivalent stress, which can be explained by the nature of the adhesive, i.e., a polymer. The identification of the material parameters of such pressure-dependent constitutive models requires a large experimental database taking into account various tensile–shear loadings. Under quasi-static loadings at low temperature, for a given strain rate range, viscous effects can be neglected, but only a few experimental results are available to model the behaviour of an adhesive in a bonded assembly accurately under realistic loadings. Moreover, edge effects often have a large influence on the mechanical response. This paper presents the possibility of combining the use of a modified Arcan device, which strongly limits the influence of the stress concentrations, with a usual thermal chamber. Experimental results, underlining the temperature-dependent non-linear responses of an adhesive, are presented in the case of various tensile/compression–shear monotonic loadings for a temperature range between 20 °C and −60 °C. The analysis of experimental results, obtained in the load-Displacement Diagram, focuses herein on the modelling of the initial temperature-dependent yield surface; but such results are also useful for the development of the flow rules in the case of pressure-dependent models.

  • Analysis of the low temperature-dependent behaviour of a ductile adhesive under monotonic tensile/compression-shear loads
    International Journal of Adhesion and Adhesives, 2012
    Co-Authors: Claudiu Badulescu, Jeanyves Cognard, Romain Créac'hcadec, P Vedrine
    Abstract:

    Various models exist to describe the non-linear behaviour of an adhesive in an assembly, taking into account the two stress invariants, hydrostatic stress and von Mises equivalent stress, which can be explained by the nature of the adhesive, i.e., a polymer. The identification of the material parameters of such pressure-dependent constitutive models requires a large experimental database taking into account various tensile-shear loadings. Under quasi-static loadings at low temperature, for a given strain rate range, viscous effects can be neglected, but only a few experimental results are available to model the behaviour of an adhesive in a bonded assembly accurately under realistic loadings. Moreover, edge effects often have a large influence on the mechanical response. This paper presents the possibility of combining the use of a modified Arcan device, which strongly limits the influence of the stress concentrations, with a usual thermal chamber. Experimental results, underlining the temperature-dependent non-linear responses of an adhesive, are presented in the case of various tensile/compression-shear monotonic loadings for a temperature range between 20 °C and −60 °C. The analysis of experimental results, obtained in the load-Displacement Diagram, focuses herein on the modelling of the initial temperature-dependent yield surface; but such results are also useful for the development of the flow rules in the case of pressure-dependent models.