Computational modelling of impact damage in brittle materials

Introduction Metal forming process Analysis and technology in metal forming Plasticity and viscoplasticity Methods of analysis The finite element method (1) The finite element method (2) Plane-strain problems Axisymmetric isothermal forging Steady state processes of extrusion and drawing Sheet metal forming Thermo-viscoplastic analysis Compaction and forging of porous metals Three dimensional problems Preform design in metal forming Solid formulation, comparison of two formulations, and concluding remarks Index.

/pdf/metal-forming-and-the-finite-element-method-5ev6lca5h5.pdf

Metal Forming and the Finite-Element Method

A new method of modeling material behavior which accounts for the dynamic metallurgical processes occurring during hot deformation is presented. The approach in this method is to consider the workpiece as a dissipator of power in the total processing system and to evaluate the dissipated power co-contentJ = ∫o σ e ⋅dσ from the constitutive equation relating the strain rate (e) to the flow stress (σ). The optimum processing conditions of temperature and strain rate are those corresponding to the maximum or peak inJ. It is shown thatJ is related to the strain-rate sensitivity (m) of the material and reaches a maximum value(J max) whenm = 1. The efficiency of the power dissipation(J/J max) through metallurgical processes is shown to be an index of the dynamic behavior of the material and is useful in obtaining a unique combination of temperature and strain rate for processing and also in delineating the regions of internal fracture. In this method of modeling, noa priori knowledge or evaluation of the atomistic mechanisms is required, and the method is effective even when more than one dissipation process occurs, which is particularly advantageous in the hot processing of commercial alloys having complex microstructures. This method has been applied to modeling of the behavior of Ti-6242 during hot forging. The behavior of α+ β andβ preform microstructures has been exam-ined, and the results show that the optimum condition for hot forging of these preforms is obtained at 927 °C (1200 K) and a strain rate of 1CT•3 s•1. Variations in the efficiency of dissipation with temperature and strain rate are correlated with the dynamic microstructural changes occurring in the material.

/pdf/modeling-of-dynamic-material-behavior-in-hot-deformation-3wt95ckgsf.pdf

Modeling of dynamic material behavior in hot deformation: Forging of Ti-6242

Asymmetric single point incremental forming of sheet metal

Meta-analysis of risk factors for cutaneous melanoma: III. Family history, actinic damage and phenotypic factors

Elastoplastic analysis of plane-strain and axisymmetric flat punch indentation by the finite-element method

Flank Friction Studies With Carbide Tools Reveal Sublayer Plastic Flow

In this study a new simplified 3-D numerical method and the associated computer program have been developed to simulate the shape rolling process. The 2-D rigid-plastic finite element method (FEM), used for the generalized plane-strain condition, is combined with the slab method. This method, called FSEM (finite and slab element method), reduces the computational effort without losing much accuracy obtained in the 3-D computer simulation of the shape rolling process. The FSEM has been used to develop a computer program, called TASKS for three-dimensional analysis of shape-rolling as a kinematically steady-state process. The program TASKS has been used to simulate the metal flow and the bulge profile in flat rolling of slabs, the shape rolling of a simple H section, and the rolling of a practical H-beam section. In flat rolling, predicted spreads agreed well with experimental results, given in the literature. The metal flow in rolling of a simple H section was compared with results of a full 3-D simulation, obtained by other investigators. The comparison indicated that the present predictions give quite good results. Finally, the predictions made for a practical pass, used in rolling H sections, also compared well with experimental data.

Shiro Kobayashi

Papers

Elastoplastic analysis of plane-strain and axisymmetric flat punch indentation by the finite-element method

Flank Friction Studies With Carbide Tools Reveal Sublayer Plastic Flow

Three-dimensional analysis and computer simulation of shape rolling by the finite and slab element method

The Effect of Anisotropy and Work-Hardening Characteristics on the Stress and Strain Distribution in Deep Drawing

Upper- and lower-bound solutions to axisymmetric compression and extrusion problems