Mesoscopic modeling of the rtm process for homogenization

Intrinsic hybrids can be manufactured in a modified resin transfer molding (RTM) process for fibre reinforced polymers. Our work concentrates on mesoscopic modeling for temperature-dependent visco-elastic effects accompanied by curing within the RTM process. During hybridization and later thermal loading the periodic mesostructure defined by resin and fibres is taken into account as a representative volume element (RVE) subjected to thermo-mechanical loading. Homogenization leads to results on the less resolved macroscale. In the examples we illustrate the characteristic behavior of the mesoscopic model, such as shrinking due to curing and temperature dependence and simulate the RTM process as well as thermal loading of the cured composite with the finite-element-method

Two Scale FE Simulation of Coated Forming Tools under Thermo-Mechanical Loading

Modern trends and challenges in manufacturing processes have led to an increasing complexity of hybrid forming processes in the last couple of years. Besides the improvement of the thermo-mechanical process chain the application of coated forming tools plays a crucial role in actual developments. Considering machining processes in general the investigation of tools experienced a secondary role in the past. For example, in numerical simulations of manufacturing processes tools are often modelled as rigid bodies. To remedy, this paper introduces a two scale finite element model for the coating system of a coated hybrid forming tool. Within this concept individual coating layers are considered on the mesocale and macroscopic results for the coating elements are obtained using volume averaging procedures. Two numerical examples using an implicit and an explicit integration scheme show the capability of the model to be applied for a coated forming tool subjected to thermo-mechanical loading conditions

The Limits of Transformation

In the shadow of the recent Iraq war, it is easy to accept that “growth and diffusion of stealth, precision, and information technology” has truly heralded the long-awaited revolution in military affairs. American leaders—from the President to the Pentagon military and civilian leadership—have called for dramatic transformation of each of the services to fit this revolution. In many ways, this is a far harder task.https://digital-commons.usnwc.edu/usnwc-newport-papers/1015/thumbnail.jp

A Stochastic Finite Element Method with a Deviatoric-volumetric Split for the Stochastic Linear Isotropic Elasticity Tensor

This paper presents a numerical method for solution of a stochastic partial differential equation (SPDE) for a linear elastic body with stochastic coefficients (random variables and/or random fields). To this end the stochastic finite element method (SFEM) is employed, which uses WIENER’S polynomial chaos expansion in order to decompose the coefficients into deterministic and stochastic parts. As a special case, we consider isotropic material behavior with two fluctuating parameters. Computational approaches involving GALERKIN projection are applied to reduce the SPDE into a system of deterministic PDEs. Furthermore, we consider normally distributed random variables, which are assumed to be stochastically independent, and which establish the number of stochastic dimensions. Subsequently, the resulting finite element equation is solved iteratively. Finally, in a representative example for a plate with a ring hole we study the influence of different variances for material parameters on the variances for the finite element results

Thermoviscoplastic modelling of asymmetric effects for polymers at large strains

AbstractGlassy polymers such as polycarbonate exhibit different behaviours in different loading scenarios, such as tension and compression. To this end a flow rule is postulated within a thermodynamic consistent framework in a mixed variant formulation and decomposed into a sum of weighted stress mode related quantities. The different stress modes are chosen such that they are accessible to individual examination in the laboratory, where tension and compression are typical examples. The characterisation of the stress modes is obtained in the octahedral plane of the deviatoric stress space in terms of the Lode angle, such that stress mode dependent scalar weighting functions can be constructed. Furthermore the numerical implementation of the constitutive equations into a finite element program is briefly described. In a numerical example, the model is used to simulate the laser transmission welding process

Electronic structure of intermetallics based on a rare earth element and a transition or noble metal

The results of ab initio study of resonant surface states genesis in the vicinity of Γ point for GdRh[2]Si[2] are presented in this work. Our electronic band structure calculations have shown that the resonant surface states are already formed in three atomic layer slab Si-Rh-Si. The states localization within three layer slab causes its resonant nature and presence of these states on Si- and Gd- termination surfaces

Mesh- and model adaptivity for elasto-plastic mean-field and full-field homogenization based on downwind and upwind approximations

Materials such as composites are heterogeneous at the micro-scale, where several constituents with different material properties can be distinguished like elastic inclusions and the elasto-plastic matrix with isotropic hardening. One has to deal with these heterogeneities on the micro-scale and then perform a scale transition to obtain the overall behavior on the macro-scale, which is often referred to as homogenization. The present contribution deals with the combination of numerically inexpensive mean-field and numerically expensive full-field homogenization methods in elasto-plasticity coupled to adaptive finite element method (FEM) which takes into account error generation and error transport at each time step on the macro-scale. The proposed adaptive procedure is driven by a goal-oriented a posteriori error estimator based on duality techniques. The main difficulty of duality techniques in the literature is that the backwards-in-time al gorithm has a high demand on memory capacity since additional memory is required to store the primary solutions computed over all time steps. To this end, several down wind and upwind approximations are introduced for an elasto-plastic primal problem by means of jump terms [1]. Therefore, from a computational point of view, the forwards-in time duality problem is very attractive. A numerical example illustrates the effectiveness of the proposed adaptive approach based on forwards-in-time method in comparison to backwards-in-time method

Unique Multiorganizational Collaborative Proves Effective in Delivering 2014 Farm Bill Education

The Agricultural Act of 2014 is critical to the economic safety net for U.S. producers. This act represented a major change in philosophy, requiring producers to make key decisions about their options on the basis of risk management. To add to the complexity of the issue, the time period for delivering applicable education to landowners before sign-up deadlines was relatively short. This article highlights a unique multiorganizational statewide approach to delivering the applicable education. It involved University of Minnesota Extension, the Center for Farm Financial Management, the U.S. Department of Agriculture, and banks and resulted in substantive evaluative outcomes