Large Deformation Finite Element Code Research Articles

Numerical prediction of soil compaction in geotechnical engineering

Soil compaction involves a reduction in volume of the soil mass instead of settlement, which has been considered as one of the most important methods to increase geomaterials' strength in geotechnical engineering practice. This paper presents a numerical model to simulate soil compaction using the finite-element method with finite deformation. The fundamental formulations for soil compaction are introduced first. Then the model is employed to simulate the compaction process and predict spatial density, in which the soil is modeled as elastoplastic material. The Drucker–Prager/Cap model is integrated in the large-deformation finite-element code and used to model the gradual compaction process of soil. Representative simulations of practical applications in geotechnical/pavement engineering are provided to demonstrate the feasibility of predicting soil compaction density using the proposed large-deformation finite-element model.

A large deformation finite element model for soil compaction

Soil compaction involves a reduction in volume of the soil mass, which has been considered as one of the most important methods to increase geomaterials' strength in geotechnical engineering practice. This paper presents a numerical model to simulate soil compaction using a finite deformation finite element approach. The fundamental formulations for soil compaction are introduced first. Then the model is employed to simulate the compaction process and predict spatial density, in which the soil is modelled as elastoplastic material. The Drucker-Prager/Cap model is integrated in the large deformation finite element code and used to model the gradual compaction process of soil. Representative simulations of practical applications in geotechnical/pavement engineering are provided to demonstrate the feasibility of predicting soil compaction density using the proposed large deformation finite element model.

Three dimensional large deformation analysis of phase transformation in shape memory alloys

Shape memory alloys (SMAs) have been explored as smart materials and used as dampers, actuator elements, and smart sensors. An important character of SMAs is its ability to recover all of its large deformations in mechanical loading-unloading cycles without showing permanent deformation. This paper presents a stress-induced phenomenological constitutive equation for SMAs, which can be used to describe the superelastic hysteresis loops and phase transformation between Martensite and Austenite. The Martensite fraction of SMAs is assumed to be dependent on deviatoric stress tensor. Therefore, phase transformation of SMAs is volume preserving during the phase transformation. The model is implemented in large deformation finite element code and cast in the updated Lagrangian scheme. In order to use the Cauchy stress and the linear strain in constitutive laws, a frame indifferent stress objective rate has to be used. In this paper, the Jaumann stress rate is used. Results of the numerical experiments conducted in this study show that the superelastic hysteresis loops arising with the phase transformation can be effectively captured.

Recent developments in DYNA3D for impact problems

DYNA3D is an explicit, large deformation finite element code which is widely used for modeling complex impact problems. Recent research and development activities at LLNL have yielded a number of improvements to DYNA3D, including a new shell element, a new material model for concrete, sand, and rock, a new set of anisotropic plasticity models for both solid and shell elements, a material model driver with interactive graphics, and others. This paper opens with an overview of the current capabilities of DYNA3D. Next, some new results in the finite element formulation of elastoplastic shell problems are presented. Then, recent developments on a new, fully vectorized two-invariant extended cap model are described. Two large-scale example problems are then presented which illustrate the application of DYNA3D to production impact analysis. The paper closes with a brief discussion of future research and development directions.