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Finite-element Simulation (finite-element + simulation)
Selected AbstractsImproved Design of Shearing Sections with New Calculation Models Based on 3D Finite-Element SimulationsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 11 2002Helmut Potente Abstract New models for the Maddock and spiral shearing sections have been developed, employing three-dimensional finite element analysis (3D FEA). These models describe the pressure-throughput and power consumption behavior of the shearing sections for both the extrusion and the injection molding process and have been implemented in the REX 6.0 and PSI 4.0 simulation software. As a consequence it is now possible to describe the process behavior of these shearing sections within just a few seconds with the accuracy of FEA calculations. Actual Maddock shearing section (left) and actual spiral shearing section (right). [source] Finite-element simulation of incompressible fluid flow in an elastic vesselINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2003Harry Y. H. Chen Abstract Finite-element simulation was performed to predict the incompressible Navier,Stokes flow in a domain, partly bounded by an elastic vessel, which is allowed to vary with time. Besides satisfying the physical conservation laws, both surface and the volume conservation laws are satisfied at the discrete level for ensuring the balance between physical and geometrical variables. Several problems which are amenable to analytical solutions were tested for validating the method. The simulated results are observed to agree favourably with analytical solutions. Having verified the applicability of the finite-element code to problems involving moving grids, we consider an incompressible fluid flow bounded by rigid and elastic vessel walls. Our emphasis was placed on the validation of the formulation developed within the moving-grid framework. Copyright © 2003 John Wiley & Sons, Ltd. [source] Probabilistic high cycle fatigue behaviour of nodular cast iron containing casting defectsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 4 2009A. NASR ABSTRACT Theoretical and experimental investigations were combined to characterize the influence of surface casting defects (shrinkages) on the high cycle fatigue (HCF) reliability. On fracture surfaces of fatigue samples, the defect is located at the surface. The shape used for the calculation is a spherical void with variable radius. Finite-element simulations were then performed to determine stress distribution around defects for different sizes and different loadings. Correlated expressions of the maximum hydrostatic stress and the amplitude of the shear stress were obtained by using the response surface technique. The loading representative point in the HCF criterion was then transformed into a scattering surface, which has been obtained by a random sampling of the defect sizes. The HCF reliability has been computed by using the Monte Carlo simulation method. Tension and torsion fatigue tests were conducted on nodular cast iron with quantification of defect size on the fracture surface. The S,N curves show a large fatigue life scattering; shrinkages are at the origin of the fatal crack leading to the final failure. The comparison of the computed HCF reliability to the experimental results shows a good agreement. The capability of the proposed model to take into account the influence of the range of the defect sizes and the type of its statistical distribution has been demonstrated. It is shown that the stress distribution at the fatigue limit is log-normal, which can be explained by the log-normal defect distribution in the nodular cast iron tested. [source] Isotropic "Islands" in a Cholesteric "Sea": Patterned Thermal Expansion for Responsive Surface Topologies,ADVANCED MATERIALS, Issue 14 2006E. Sousa A method to capture ordered and disordered regions in reactive mesogen films to take advantage of the anisotropic thermal properties and fabricate a thermally responsive patterned film is presented. The image shows white-light interferometer images of isotropic cylinders in cholesteric material. The underlying principle phenomenon observed here is well described by a finite-element simulation. [source] Analysis of the fluid,structure interaction in the optimization-based design of polymer sheeting diesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Qi Wang Abstract A polymer-sheeting-die-design methodology is presented that integrates a simulation of the polymer melt flow and die-cavity deformation with numerical optimization to compute a die-cavity geometry capable of giving a nearly uniform exit flow rate. Both the polymer melt flow and sheeting-die deformation are analyzed with a general-purpose finite-element program. The approach includes a user-defined element that is used to evaluate the purely viscous non-Newtonian flow in a flat die. The flow analysis, which is simplified with the Hele,Shaw approximation, is coupled to a three-dimensional finite-element simulation for die deformation. In addition, shape optimization of a polymer sheeting die is performed by the incorporation of the coupled analyses in our constrained optimization algorithm. A sample problem is discussed to illustrate the die-design methodology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3994,4004, 2007 [source] Mixing efficiency in a pin mixing section for single-screw extrudersPOLYMER ENGINEERING & SCIENCE, Issue 6 2001W. G. Yao Non-Newtonian, non-isothermal, 3D finite-element simulation of mixing performance in a pin mixing section with different axial gaps in the pins has been carried out according to their realistic configurations. The quantitative evaluation of mixing ability was based on the theory of kinematics of fluid mixing. To learn and to compare the local mixing performance in a standard screw and a pin mixing section, the local mixing efficiency distribution proposed by Ottino was calculated. Also, the RTDs of these mixers were calculated in an attemt to measure mixing. The integration of the two, namely, the integrating local mixing efficiency along a number of particle pathlines from entrance to exit, together with statistical treatment, which was referred as integral mixing efficiency, then gives a quantitative judgment of the total mixing ability of a continuous mixer. The calculated results showed a nonlinear dependence of the mixing ability of a pin mixing section on the axial gap of the pins. Finally, the calculation results were compared with the experimental ones obtained in our previous study. [source] Cell Detachment Model for an Antibody-Based Microfluidic Cancer Screening SystemBIOTECHNOLOGY PROGRESS, Issue 5 2006Swapnil P. Wankhede We consider cells bound to the floor of a microfluidic channel and present a model of their flow-induced detachment. We approximate hydrodynamic force and cell elastic response using static finite-element simulation of a single cell. Detachment is assumed to occur when hydrodynamic and adhesive forces are roughly equal. The result is extended to multiple cells at the device level using a sigmoidal curve fit. The model is applied to a microfluidic cancer-screening device that discriminates between normal epithelial cells and cells infected with human papillomavirus (HPV), on the basis of increased expression of the transmembrane protein ,6 integrin in the latter. Here, the cells to be tested are bound to a microchannel floor coated with anti ,6 integrin antibodies. In an appropriate flow rate range, normal cells are washed away while HPV-infected cells remain bound. The model allows interpolation between data points to choose the optimal flow rate and provides insight into interaction of cell mechanical properties and the flow-induced detachment mechanism. Notably, the results suggest a significant influence of cell elastic response on detachment. [source] A unified continuum representation of post-seismic relaxation mechanisms: semi-analytic models of afterslip, poroelastic rebound and viscoelastic flowGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2010Sylvain Barbot SUMMARY We present a unified continuum mechanics representation of the mechanisms believed to be commonly involved in post-seismic transients such as viscoelasticity, fault creep and poroelasticity. The time-dependent relaxation that follows an earthquake, or any other static stress perturbation, is considered in a framework of a generalized viscoelastoplastic rheology whereby some inelastic strain relaxes a physical quantity in the material. The relaxed quantity is the deviatoric stress in case of viscoelastic relaxation, the shear stress in case of creep on a fault plane and the trace of the stress tensor in case of poroelastic rebound. In this framework, the instantaneous velocity field satisfies the linear inhomogeneous Navier's equation with sources parametrized as equivalent body forces and surface tractions. We evaluate the velocity field using the Fourier-domain Green's function for an elastic half-space with surface buoyancy boundary condition. The accuracy of the proposed method is demonstrated by comparisons with finite-element simulations of viscoelastic relaxation following strike-slip and dip-slip ruptures for linear and power-law rheologies. We also present comparisons with analytic solutions for afterslip driven by coseismic stress changes. Finally, we demonstrate that the proposed method can be used to model time-dependent poroelastic rebound by adopting a viscoelastic rheology with bulk viscosity and work hardening. The proposed method allows one to model post-seismic transients that involve multiple mechanisms (afterslip, poroelastic rebound, ductile flow) with an account for the effects of gravity, non-linear rheologies and arbitrary spatial variations in inelastic properties of rocks (e.g. the effective viscosity, rate-and-state frictional parameters and poroelastic properties). [source] | ||||||||||