Explicit Finite Research Articles

Volume-Filling Effects on Sloshing Frequency in Simplified and Explicit Dynamic Finite Element Models of Tank Wagons during Braking and Turning

Volume-Filling Effects on Sloshing Frequency in Simplified and Explicit Dynamic Finite Element Models of Tank Wagons during Braking and Turning

Evaluation of Deformation Characters in Edgesof Hot Rolled Slab by Lode Parameter

The hot rolling processes of slabs have been simulated by 3-D explicit dynamics Thermal-mechanical Finite Element Model (FEM) to solve the problems of edge defects. It can analyze the deformation characteristics of rolling slabs, calculate Lode parameter values in rolling deformation zone and analyze the stress-strain state in the entrance and exit of the slabs edge. Because there are the relationship between plastic deformation types and Lode parameter, and the quantitative relation metal flow and various Lode parameter. Results showed that there are complicated metal flow and various Lode parameter values in the edge of rolling deformation zone. Although there stress-strain states are various in the entrance and exit of the slab edges the μdε<0, the tensile strain increment in the direction of max principle strain was bigger than another two directions and the edges had the character of tensile deformation. This is the major cause that edge of slab is more defects than other zone.

Explicit Dynamic Finite Element Method for Predicting Implosion/Explosion Induced Failure of Shell Structures

A simplified implementation of the conventional extended finite element method (XFEM) for dynamic fracture in thin shells is presented. Though this implementation uses the same linear combination of the conventional XFEM, it allows for considerable simplifications of the discontinuous displacement and velocity fields in shell finite elements. The proposed method is implemented for the discrete Kirchhoff triangular (DKT) shell element, which is one of the most popular shell elements in engineering analysis. Numerical examples for dynamic failure of shells under impulsive loads including implosion and explosion are presented to demonstrate the effectiveness and robustness of the method.

Numerical Simulation and Testing of Water Impact of Structural Attachment Elements of a Reusable Thermal Protection System

Multiple mission reuse capability has become extremely important, towards reducing costs of space transportation. Carbon / Carbon (C/C) composites are well proven, functionally, for repeated use in re-entry missions. A re-entry capsule with sphere-cone-flare external shape, currently under realisation, will fly with C/C Thermal Protection System (TPS) in its peak heating region. The biggest challenge in design of such a reusable hot structure TPS is the management of thermo-structural loads. Differential Coefficient of Thermal Expansion (CTE) is the main cause of stress on the structural assembly elements. A set of flexible super alloy attachment brackets have been configured to take care of this differential thermal expansion of various TPS elements. The brackets also have to survive the impact transient load, on splashdown. This load was estimated using explicit non linear Finite Element method by considering the whole structure a rigid body. A separate FE model with actual stiffness of the structural attachments and the hot structure was generated, to predict the stresses caused by the load. In order to demonstrate the margins and survivability of the assembly, as a whole, a water impact test with actual qualification model of the assembly was carried out in a 10 m deep shock tank. The test also helped to validate the prediction. Considering factors such as cost, time and process constraints involved in realising C/C TPS for the test, it was decided to replace the same with an equivalent structure that satisfied all design and functional requirements. The test article was dropped vertically to simulate an impact velocity of 12 m/s and was adequately instrumented with accelerometers and strain gauges. The test results correlate reasonably well with the prediction.

Unsteady Magneto-Hydrodynamic (MHD) flow of a uniformly stretched vertical permeable surface I in the presence of heat generation/absorption and a first order chemical reaction.

Numerical results are presented for the transient and steady state Velocity, Temperature and Concentration fields. These results are obtained by solving the partial differential equations describing the conservation, momentum energy and species concentration by an explicit finite – difference method in time – dependent form. It was discovered that a maximum exist which confirm that maximum velocity and temperature occur in the body of the fluid and not in the surface as previously reported. A parametric study was conducted and the results were presented and discussed. Journal of the Nigerian Association of Mathematical Physics Vol. 10 2006: pp. 503-510

Explicit Finite Difference Solution of Heat Transfer Problems of Fish Packages in Precooling

The present work aims at finding an optimized expli cit finite difference scheme for the solution of problems involving pure heat transfer f rom the surfaces of Pangasius Sutchi fish samples suddenly exposed to a cooling environment. Regular shaped packages in the form of an infinite slab were considered and a generalized mathematical model was written in dimensionless form. An accurate sample of the data set was chosen from the experimental work and was used to seek an optimized scheme of solutions. A fully explicit fin ite difference scheme has been thoroughly studied from the viewpoint of stability, the required time for execution and precision. The characteristic dimension (half thickness) was divided into a numbe r of divisions; n = 5, 10, 20, 50 and 100 respectively. All the possible options of dimension less time (the Fourier number) increments were taken one by one to give the best convergence and t runcation error criteria. The simplest explicit fin ite difference scheme with n = (10) and stability facto r (ΔX) 2 /Δτ = 2) was found to be reliable and accurate for prediction purposes.

Topical cardiac cooling—computer simulation of myocardial temperature changes

Topical cardiac cooling (TC) is often used in cardiac surgery. We used a computer simulation to study temperature changes in the heart, especially in the right ventricular wall. A three-dimensional computer heart model, derived from Visible Human Data set, National Library of Medicine was used. The model is made from cubes, with spatial resolution of 1 mm . Explicit Finite Different method and temperature diffusion equation were used to calculate new temperatures. Three different simulations were performed and simulated temperatures were drawn on a cross-section of heart model in different colors. The results show that areas not immersed into TC solution are less protected against ischemia. It is important not to rely solely on topical cooling but use appropriate method of myocardial protection technique.

Natural convection heat transfer from a thin rectangular fin with a line source at the base — a finite difference solution

This paper presents an analysis of the problem of a thin fin of finite thermal conductivity, with an isothermal line source at the base, dissipating heat to the surrounding air by natural convection. The horizontal surface to which the fin is attached is adiabatic so that heat is dissipated only through the fin. The temperature and velocity distributions in the field, the temperature profile in the fin, local Nusselt numbers along the fin and the average heat transfer coefficient of the fin are obtained by solving the governing equations in the field and the heat transfer equation in the fin simultaneously, using an explicit unsteady Finite Difference formulation leading to the steady state result. Numerical experiments are performed to study the influence of parameters namely the fin height, temperature of the heating source and the fin material on the average heat transfer coefficient. Comparison is made with fins of infinite thermal conductivity and the vertical isothermal flat plate.