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Papers by Ridha Ben Yedder
Hybrid Approach for Modeling of Parison Extrusion in Blowmolding
Journal of Polymer Engineering, 2000
Polymer Engineering & Science, 2007
In this work, we consider a nonisothermal finite-element analysis approach using an explicit dyna... more In this work, we consider a nonisothermal finite-element analysis approach using an explicit dynamic procedure for the forming of a polyethylene terephthalate (PET) sheet subjected to air-flow loading. The dynamic pressure load is thus deduced from the van der Waals equation of state. The effect of the radiative-conduction heat transfer during the reheating stage, the stress-deformation behavior during the incomplete forming stage, and the solidification during the cooling stage are simulated. The viscohyperelastic behavior of the Christensen-Yang-like model is considered. The Lagrangian formulation, together with the assumption of the membrane shell theory, is used. The viscohyperelastic model is validated with the equibiaxial stretching tests. Also, temperature validation is performed by comparing the computed, the theoretical, and the experimental temperature profiles obtained from measuring the inside and outside PET sheet surface. An example of thermoforming a PET part is presented. In this example, the influence of the air-flow on the thickness and the stress distribution is presented. POLYM. ENG. SCI.,
International Journal of Heat and Mass Transfer, 2009
Natural convection in an air-filled (Prandtl number = 0.7) porous cavity with profiled side cooli... more Natural convection in an air-filled (Prandtl number = 0.7) porous cavity with profiled side cooling and constant bottom heating is investigated over the Rayleigh number range of 1 Â 10 4 to 1 Â 10 8 at two Darcy numbers: 1 Â 10 À4 and 1 Â 10 À6 . The aspect ratio based on cavity height was varied from 0.5 to 0.1 to investigate penetration length according to linear or sinusoidal temperature profile. The general non-Darcy model adopted in this work was validated against experimental and theoretical results in the literature and Nusselt number was predicted within less than 3% in the worst case. The effect of left wall imposed temperature profile was investigated in detail. Different convective regimes were observed depending on the imposed profile. An active region was found to take place with the linear temperature profile and with extent proportional to Rayleigh number as predicted by scale analysis.
Hybrid Approach for Modeling of Parison Extrusion in Blowmolding
Journal of Polymer Engineering, 2000
Polymer Engineering & Science, 2007
In this work, we consider a nonisothermal finite-element analysis approach using an explicit dyna... more In this work, we consider a nonisothermal finite-element analysis approach using an explicit dynamic procedure for the forming of a polyethylene terephthalate (PET) sheet subjected to air-flow loading. The dynamic pressure load is thus deduced from the van der Waals equation of state. The effect of the radiative-conduction heat transfer during the reheating stage, the stress-deformation behavior during the incomplete forming stage, and the solidification during the cooling stage are simulated. The viscohyperelastic behavior of the Christensen-Yang-like model is considered. The Lagrangian formulation, together with the assumption of the membrane shell theory, is used. The viscohyperelastic model is validated with the equibiaxial stretching tests. Also, temperature validation is performed by comparing the computed, the theoretical, and the experimental temperature profiles obtained from measuring the inside and outside PET sheet surface. An example of thermoforming a PET part is presented. In this example, the influence of the air-flow on the thickness and the stress distribution is presented. POLYM. ENG. SCI.,
International Journal of Heat and Mass Transfer, 2009
Natural convection in an air-filled (Prandtl number = 0.7) porous cavity with profiled side cooli... more Natural convection in an air-filled (Prandtl number = 0.7) porous cavity with profiled side cooling and constant bottom heating is investigated over the Rayleigh number range of 1 Â 10 4 to 1 Â 10 8 at two Darcy numbers: 1 Â 10 À4 and 1 Â 10 À6 . The aspect ratio based on cavity height was varied from 0.5 to 0.1 to investigate penetration length according to linear or sinusoidal temperature profile. The general non-Darcy model adopted in this work was validated against experimental and theoretical results in the literature and Nusselt number was predicted within less than 3% in the worst case. The effect of left wall imposed temperature profile was investigated in detail. Different convective regimes were observed depending on the imposed profile. An active region was found to take place with the linear temperature profile and with extent proportional to Rayleigh number as predicted by scale analysis.