In the present paper, the direct coupling of a discrete element method (DEM) with polyhedral particles and smoothed particle hydrodynamics (SPH) is presented. The two simulation techniques are fully coupled in both ways through interaction forces between the solid DEM particles and the fluid SPH particles. Thus this simulation method provides the possibility to simulate the individual movement of polyhedral, sharp-edged particles as well as the flow field around these particles in fluid-saturated granular matter which occurs in many technical processes e.g. wire sawing, grinding or lapping. The coupled method is exemplified and validated by the simulation of a particle in a shear flow, which shows good agreement with analytical solutions.

The aim of this paper is to study the mechanical tensile properties of open-cell foam structures on the cell size variation by numerical simulations. For this purpose, random Laguerre tessellations were used, which allow the creation of foam structures with strongly varying cell sizes. First, a model was fitted to real open-cell foams based on x-ray computed tomography (XCT) scans by parameter optimization. Two more virtual foam models with different cell size variations were produced according to the first fitted one. Tensile properties of the model realizations were computed by finite- element analysis using beam elements. The numerical results were presented and discussed.

The material removal rate in the wire sawing technology depends on several features of the used abrasives and the complex process of particle movement and interaction inside the kerf. To investigate these micro-mechanical aspects of the wire sawing process, a numerical model is developed in the present paper. The model is based on the discrete element method adjusted to use sharp edged polygonal particles. The crucial procedure of material removal is implemented through concepts of the fracture mechanics of sharp edged indenters. The model allows to study the influence of essential parameters like wire speed, lapping pressure, particle shape, particle size distribution a.o. on the material removal process. A parametric study towards the influence of wire speed and lapping pressure on the amount of material removal is also presented. The parametric numerical studies carried out confirm the phenomenological law of Preston for the removal rate and enable correlations between the Preston coefficient and micro-mechanical process parameters.

Mechanical, thermo-mechanical, and fluid dynamic simulations of open-cell foams require an accurate geometry model. Usually, models are derived from computer- tomography (CT) data which do not allow analysing systematically variation and optimisation of the geometry. On the other hand, entirely computer generated models are mostly assembled of primitive objects like cylinders. This disregards strut thickness variations and node rounding which are observed in real open-cell foams. This paper presents an approach to generate models of ceramic open-cell foams using simple objects with variable thickness generated by implicit functions. This approach can also account for cavities within struts and nodes, which are observed in many real foam structures. The specific rounding at the foam nodes can be modelled by applying the transformation of BLINN. The quality of the generated foam models is verified using CT data of real foams. (C) 2012 Elsevier Ltd. All rights reserved.

The aim of the study is to clarify how far it is possible to describe the mechanical behavior of novel TRIP-Steel/Mg-PSZ composite open-cell foam structures using beam networks generated from random tessellations. Conventional compression tests were performed with various foam samples. Furthermore, the deformation of open-cell composite foams was observed as well by X-ray computed tomography (XCT). Up to a compressive strain of 20% different stages of deformation could be observed. Respective bulk samples were manufactured by powder metallurgy and tested in order to determine the mechanical properties of the bulk material. Numerical simulations were employed based on the suitable modeling of foams exposed to mechanical loading. The predictions of the simulation are compared with the results of the deformation experiments.

Based on experimental results, performed on an instrumented single wire saw, an analytical model for the macroscopic mechanical conditions in the wire sawing process is presented. The model describes the influence of important process parameters like wire velocity, feed velocity and tension force as well as geometric relations like ingot size and wire length to the lapping pressure and the shape of the formed wire bow. The model is based on macroscopic, measurable, machining parameters and uses the experimentally determined relation between pressure and removal rate according to Prestons law. The derived equations are used to study the influence of typical process parameters systematically and the results are exemplified for the production line of 6in solar wafers.

AbstractThe wire sawing technology plays an important role on the manufacturing of thin discs out of brittle materials and is used for example in the solar‐ and microelectronic industry. The surface of a wire sawn disc shows a characteristic geometry, which suggests the influence of oscillations during the slicing process. In order to examine the process a distinct‐element‐model is used to simulate the motion and the interaction of the abrasive particles with the moving wire and the workpiece. The simulation shows interesting phenomena like clustering of particles and reacting forces to the wire, which could be one reason for the observed oscillations in the process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)