June 2010

CALCULATION OF SPINDLE COMPLIANCE CONSIDERINGS IT ́S INTERACTION WITH MACHINE FRAME

MM (Modern Machinery) Science Journal, June 2010
M. Sulitka, P. Kolar
Research Center for Manufacturing Technology
Faculty of Mechanical Engineering, CTU in Prague, Czech Republic
Abstract

The calculation of spindle dynamic compliance is usually performed taking into account only the mechanical system of the spindle and tool, while the influence of the machine tool frame is neglected. However, when performing machining operations characterized by high cutting forces – which typically arise e.g. during roughing – machine frame vibration may be induced. Under such conditions, a model of the spindle alone is not sufficient to predict the dynamic behaviour of the spindle; therefore, coupled models of the spindle and machine frame system need to be created. The paper presents two possible approaches that can be used for such tasks. The first approach consists in modelling the whole mechanical system in the Finite Element (FE) environment; the second one employs the technique of coupling modally reduced separate models of flexible bodies. The application of both approaches and their comparison is illustrated by an example of a real machine tool model. The influence of the machine tool frame on the spindle dynamic compliance is demonstrated using the machine tool coupled models.

Keywords: Spindle dynamic properties, Coupled models of spindle and machine frame, Modal decomposition, Modal reduction, FEM
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IDENTIFICATION OF MATERIAL PARAMETRES BY FEM

MM (Modern Machinery) Science Journal, June 2010
J. Rojicek
Department of Mechanics of Materials
VSB-Technical University of Ostrava, Czech Republic
Abstract

The article describes an identification of material parameters from set of experiments. The experiments were made with hollow cylindrical specimens. The specimens were fabricated from the steel (11375). In this study are used the data obtained from 5 experiments (axis force, torque and their combination). Software ANSYS v.11.0 based on Finite Element Method (FEM) was used as a tool for the identification of the material parameters (inverse algorithm). There were implemented many material models in the software. The article uses Multilinear material model, rate independent and Ramberg-Osgood approximation of constitutive equations (3. material parameters) for the problem solution. The data correlations and data dispersions were used for estimating new values of material parameters. The solutions were found by FEM (for selected material model, 3. material parameters) and were compared with the experimental data.

Keywords: inverse algorithm, FEM, experiments, tension, torsion, multilinear isotropic, material parameters
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SOFTWARE ARCHITECTURE FOR PARALLEL SIMULATION OPTIMIZATION

MM (Modern Machinery) Science Journal, June 2010
P. Horejsi
Department of Industrial Engineering and Management
Faculty of Mechanical Engineering
University of West Bohemia, Plzen, Czech Republic
Abstract

Manufacturing simulation issues can be solved in a variety of different COTS (Commercial off The Shelf) simulation software – for example ARENA, QUEST, SIMUL8, Siemens PlantSimulation, etc. The input and output values can be stored in databases, but the interface has to be implemented by a developer. The output values (such as manufacturing time, average time of product waiting, etc.) from one simulation run (simulator) are not the optimized values, but only the result from a particular run. The optimized values can be found after performing more simulation experiments. The number of experiments required increases with the complexity of the model and the independent input values. There is also the need to set up new input parameters correctly with consideration of optimization gradient prediction. If the model is very simple and accuracy is not important, the input settings can be made manually. For common cases this process must be automated. A software solution for the automation of the simulation optimization process in parallel logic SIMD (Single Instruction – Multiple Data Stream) was developed using Rockwell ARENA simulation software. The simulation can be speeded up rapidly with the aid of a parallel approach. This software also supports networking and also acts as the reference for further work on methodology for the optimization method and its choice of presets.

Keywords: Simulation, optimization, simulation optimization, optimization algorithm, ARENA
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ANALYSIS OF DELAMINATION IN DRILLING OF COMPOSITE MATERIALS

MM (Modern Machinery) Science Journal, June 2010
J. Sedlacek, M. Slany
Brno UT, Faculty of Mechanical Engineering Brno, Czech Republic
Abstract

The aim of this work is to clarify the interaction mechanisms between the drilling tool and material. Among the defects caused by drilling, delamination appears as to be of the most critical and may occurs at both the entrance and exit plane. This paper presents a prediction Hocheng-Dharan model of thrust force for drilling without delamination. HSS twist drills with different geometry were used for drilling of carbon/epoxy composites. Experiments were performed to validate physical model of delamination and investigate the effect of tool geometry and drilling paramenters on delamination. The results showed that proposed delamination model is adequate and that damage around drilling hole can be reduced significantly by proper selection of drilling conditions.

Keywords: composite materials, delamination, drilling, tool wear
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