A new damping modelling approach and its application in thin wall machining

In this paper, a new approach to modelling the damping parameters and its application in thin wall machining is presented. The approach to predicting the damping parameters proposed in this paper eliminates the need for experiments otherwise used to acquire these parameters. The damping model proposed was compared with available damping models and experimental results. A finite element analysis and Fourier transform approach has been used to obtain frequency response function (FRF) needed for stability lobes prediction. Several predicted stable regions using both experimental and numerical FRF’s for various examples gave a good comparison.Engineering and Physical Sciences Research Counci

Dimensional variation of die-pressed ceramic green compacts: Comparison of a finite element modelling with experiment

The dimensional variation of simple die-pressed ceramic green compacts is analysed by elasto-plastic numerical modelling with the finite element method and also by experimental investigations. For the experimental investigations, the shape of a cylindrical alumina compact, obtained by using a single-acting punch dee pressing system, was measured by means of non-contacting laser profilometry. To facilitate the numerical modelling, the Drucker-Prager/cap elasto-plasticity model was used in conjunction with the finite element code ABAQUS. Computed internal stress distributions are reported at various stages of the compaction. also, the final geometry of the compacted green component was predicted. The origins of the dimensional variation of the ceramic green compacts are discussed. It is shown that the predicted shape results, obtained from the numerical model, agree well with the corresponding experimental results. (C) 1997 Elsevier Science Limited

The internal form of compacted ceramic components: A comparison of a finite element modelling with experiment

This paper is concerned with the internal form of compacted ceramic green components. The structural inhomogeneity of alumina specimens, compressed in a top pressed cylindrical die, is studied experimentally, by using lead balls as tracers to detect the densification, as well as by numerical computation. The flow behaviour of a ceramic powder, an agglomerated alumina, is described by the modified Drucker-Prager/cap elasto-plasticity material model developed for powder applications. The modified Drucker-Prager/cap constitutive model, implemented by using the finite element code ABAQUS, is discussed. The procedure for selecting the necessary material parameters by the inclusion of material response data and assumptions made in the implementation of the numerical model are described. The accuracy of the presented numerical method is evaluated by comparing the simulation results with experimental data obtained from density measurements. The evolution of the density distributions during the entire compaction process is predicted. The determining step for the formation of the subtle density variations on the central axis of the green ceramic compacts was found, from the modified Drucker-Prager/cap finite element analysis, to be the unloading step of the compaction process. In this respect, a comparison of the finite element and experimental results showed good mutual agreement

A finite-element approach for the shape prediction of ceramic compacts during sintering

This paper describes and demonstrates the effectiveness of a finite-element procedure to predict the shape changes of "green powder compacts" during sintering processes. The approach is based on the conservation-of-mass principle and requires for its implementation (i) descriptions of the finite-element meshes of the original form (powder bed) and the green bodies when ejected from the die (thus, descriptions of the geometries of the compact before and after the compaction process) and (ii) the densities of the compacts before the compaction and after the sintering processes. Numerical shape predictions have been compared with experimental data, for all the external surfaces that are obtained from sintered, cylindrical alumina specimens. The overall predicted diametric dimensional-variation changes correlate with the corresponding measured data; both indicate a "barrel" shape, The comparisons reveal that the quantitative predictions in regard to the height and diameter range correlate closely with the measured values; the differences are <1.6% and 0.4%-0.08%, respectively. The overall predicted deviation changes of the end surfaces of the sintered compacts correlate,vith the corresponding measured data; both indicate a "concave" shape, with reference to the horizontal plane, as viewed from the compaction direction. The quantitative shape comparisons for the top and bottom surfaces are <18.9% and <65.84%, respectively. The qualitative predictions at the top and bottom surfaces are considered to be in good agreement, for most practical purposes