Kinetic friction for multi-material arbitrary Lagrangian Eulerian extended finite element formulations

An extended finite element method (X-FEM) for classical kinetic friction laws in a multi-material arbitrary Lagrangian Eulerian (MMALE) formulation is presented. The velocities of the nodes containing more than one material in their support are updated through the nodal accelerations to account for the kinetic friction effects. Numerical results are presented and discussed. Army Research Organization; contract/grant number: DAAD19-02-1-0266.     

Consistent arbitrary Lagrangian Eulerian formulation for large deformation thermo-mechanical analysis

Arbitrary Lagrangian Eulerian (ALE) method is widely used for simulation of large deformation problems, such as metal forming. However, in many such applications, modeling of the heat generation and transfer in conjunction with the stress analysis is necessary. In this work, a fully coupled dynamic ALE formulation is developed. The ALE form of energy balance equation is derived, and is coupled with the dynamic, rate dependent ALE stress analysis. The proposed formulation is used for simulation of a few thermo-mechanical problems. The effectiveness and efficiency of the ALE method is verified by comparing the results of this simulation with available experimental and numerical results.     

Finite element simulation of combined buoyancy and thermocapillary driven convection in open cavities

Thermocapillary-induced and buoyancy-driven convective flows that commonly occur in crystal growth are numerically simulated using Galerkin finite element method. The physical domain comprises of a open cavity with aspect ratio one and differentially heated vertical walls. The top gas–melt interface is free to deform subject to 90° contact angle boundary conditions at the two vertical walls. The unsteady two-dimensional Navier–Stokes equations are discretized in time using Chorin-type splitting scheme and pressure is determined from the Poisson's equation. The free surface is taken to be resting on vertical spines and its evolution in time is determined from the kinematic free surface equation. The governing equations for heat and momentum are solved in the Arbitrary Lagrangian Eulerian frame of reference to handle the moving boundary. The influence of Grashof number, Marangoni number, Bond number, Ohnesorge number and Prandtl number on the flow field and heat transfer is investigated.     

T型管及管内流体动态响应仿真研究

根据实际物理实验,采用ALE有限元方法模拟了冲击情况下T型管及管内流体动态响应的水锤过程。经过对比关键点水压时程变化的仿真结果与实验数据,验证了ALE流固耦合有限元方法在水力瞬变仿真模拟方面的可行性。在此基础上,进一步分析了T型管的变形和动态周向应力。通过仿真发现管壁动态周向应力峰值大约是静周向应力的1.2～1.6倍。并且周向应力呈现与水锤压力变化一致的周期性,管壁动态周向应力主要受水锤的影响。这证明动态效应是导致更大动态应力的原因。这一结论与直管的结论一致。     

Effect of extrusion stem speed on extrusion process for a hollow aluminum profile

Extrusion stem speed is one of important process parameters during aluminum profile extrusion, which directly influences the profile quality and choice of extrusion equipments. In this paper, the extrusion process of a thin-walled hollow aluminum profile was simulated by means of the HyperXtrude commercial software. Through a serial of numerical simulation, the effects of stem speed on extrusion process, such as metal flow behavior at die exit, temperature distribution, extrusion force, and welding pressure, have been investigated. The numerical results showed that there existed an optimum value of stem speed for flow velocity distribution. With the increasing stem speed, the temperature of the extrudate and required extrusion force increased, and the welding quality of extrudate would be improved. Through comprehensive comparison and analysis, the appropriate stem speed could be determined for practical extrusion production. Thus, the research results could give effective guideline for determining initial billet and die temperature and choosing the proper extrusion press in aluminum profile industry.     

A Multiscale/stabilized Formulation of the Incompressible Navier–Stokes Equations for Moving Boundary Flows and Fluid–structure Interaction

This paper presents a multiscale/stabilized finite element formulation for the incompressible Navier–Stokes equations written in an Arbitrary Lagrangian–Eulerian (ALE) frame to model flow problems that involve moving and deforming meshes. The new formulation is derived based on the variational multiscale method proposed by Hughes (Comput Methods Appl Mech Eng 127:387–401, 1995) and employed in Masud and Khurram in (Comput Methods Appl Mech Eng 193:1997–2018, 2006); Masud and Khurram in (Comput Methods Appl Mech Eng 195:1750–1777, 2006) to study advection dominated transport phenomena. A significant feature of the formulation is that the structure of the stabilization terms and the definition of the stabilization tensor appear naturally via the solution of the sub-grid scale problem. A mesh moving technique is integrated in this formulation to accommodate the motion and deformation of the computational grid, and to map the moving boundaries in a rational way. Some benchmark problems are shown, and simulations of an elastic beam undergoing large amplitude periodic oscillations in a viscous fluid domain are presented.     

A thermodynamically compatible model for describing asphalt binders: solutions of problems

In this sequel to the first paper (Málek et al., 2014. International Journal of Pavement Engineering), in which we identified a generalisation of the model due to Burgers which was corroborated against two sets of experiments, including a challenging one showing distinctly different relaxation times for shear and normal stresses, we solve several time-dependent boundary value problems wherein the boundary of the material is deforming, that have relevance to applications involving asphalt. Problems wherein the boundary is subject to time-varying compressive loads such as those due to moving automobiles and the attendant rutting, and the compaction due to rollers are considered in additions to other problems.     

Numerical analysis of blast-induced wave propagation using FSI and ALEmulti-material formulations

As explosive blasts continue to cause casualties in both civil and military environments, there is a need to identify the dynamic interaction of blast loading with structures, to know the shock mitigating mechanisms and, most importantly, to identify the mechanisms of blast trauma. This paper examines the air-blast simulation using Arbitrary Lagrangian Eulerian (ALE) multi-material formulation. It will explain how the fluid–structure interaction (FSI) can be simulated using a coupling algorithm for the treatment of the fluid as a moving media by a moving mesh using ALE formulation and how the structure is treated on a deformable mesh using a Lagrangian formulation. To validate the numerical approach, as well as to prove its ability to simulate complicated scenarios, comparison of three distinct blast scenarios, i.e., blast from C-4 and TNT in open space and blast on a circular steel plate, with the experimental data was performed. The predicted numerical results match very well with those of experiments. This computational approach is able to accurately predict the relevant aspects of the blast–structure interaction problem, including the blast wave propagation in the medium and the response of the structure to blast loading.     

Modelling the structural response of GLARE panels to blast load

This paper deals with the structural response of fully-clamped quadrangular GLARE panels subjected to an intense air-blast load using the commercial finite element software, LS-DYNA. A cohesive tie-break algorithm is implemented to model interfacial debonding between adjacent plies. The blast loads was simulated using a ConWep blast algorithm and a multi-material ALE formulation with fluid–structure interaction to determine the performance of each method. Numerical model validation have been performed considering case studies of GLARE panels subjected to spherical explosive charges of C-4, for which experimental data on the back face-displacement and post-damage observations were available. Excellent agreement of mid-point deflections and evidence of severe yield line deformation were presented and discussed against the performed blast tests.