December 2009

December 2009

Machine Tool Virtual Model

Machine tool development for high speed and highly precise cutting demands employment of advanced simulation techniques, which can enable already in the machine tool design phase to model the feed drive dynamic properties and feed drive control. The paper describes the current state of feed drive complex models development in the RCMT. Influence of an appropriate approach to machine frame structure modelling on the feed drive dynamic properties prediction is discussed together with the influence of the ball screw feed drive mechanical structure parameters. Shown are examples of complex models application in the tasks of machine tool development and optimization. Vision of the machine tool virtual models development aims at the possibility to simulate the cutting process with the employment of the Hardware in the Loop systems and cutting process model.

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NUMERICAL AND EXPERIMENTAL ANALYSIS OF RESIDUAL STRESSES INDUCED BY CONTACT LOADING

The paper deals with numerical and experimental solution of residual stresses, which occurs due to a contact loading. The first solved case corresponds to frictionless contact in an indent test accepted from literature. In the finite element analysis, three material options with isotropic, kinematic and combined hardening were tested. The model of Calloch and Marquis, which was implemented into the Ansys FE program by user subroutine, shows the best correlation with experiments. The experimental results were obtained by two experimental methods, namely by the Neutron diffraction method and by the Contour method, which is not well known in the Czech Republic. Hence, this paper includes also a brief description of the new destructive method. Both methods can lead to prediction of full field residual stresses distribution. Some difficulties from application of the contour method to own experiment in rolling contact fatigue domain are also discussed.

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MACROSCOPIC RESIDUAL STRESSES IN STEELS GROUND UNDER VARIOUS CONDITIONS OF HEAT REMOVAL

Macroscopic residual stresses on the surface and their depth distributions in steels ground in various cooling environments represent the central issue of this contribution. The specimens were manufactured from three ferrous materials – carbon steel C45, low carbon Mn-Cr steel 16MnCr5 and corrosion-resistant chromium steel M300, and consequently ground with face grinding machine and corundum wheel in three regimes of heat removal: ambient air, emulsion of water and synthetic fluid for grinding operations and cooling air from Ranque –Hilsch vortex tube. Methods of X-ray diffraction (XRD) analysis were applied for evaluation of anisotropic state of triaxial residual stress. Since the XRD is sensitive to surface layers of only a few micrometers in thickness, electro-chemical etching had to be employed in order to obtain gradients of chosen components of macroscopic residual stress tensor.

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INVESTIGATION OF MACROSCOPIC RESIDUAL STRESSES DISTRIBUTION AFTER PROGRESSIVE MACHINING OF TOOL STEELS

HSC (High Speed Cutting) and EDM (Electro Discharge Machining) belong to the progressive and harsh machining operations. They differ markedly in the manner of material removal and, consequently, in the process of a final surface formation. While HSC represents the so called chip machining, EDM embodies a utilization of controlled thermal material reduction. With respect to the usage of these technologies, tool steels K110 and W300 were chosen for the experiments. Samples made from both the materials were primarily subjected to either HSC or EDM and residual stresses were investigated by means of X-ray diffraction, Barkhausen noise, hole-drilling, and layer removal methods.

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