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Eibar, Spain

Arnaud L.,National Engineering School of Tarbes | Gonzalo O.,Fundacion TEKNIKER IK4 | Seguy S.,INSA Toulouse | Jauregi H.,Fundacion TEKNIKER IK4 | Peigne G.,Ecole Centrale Nantes
International Journal of Advanced Manufacturing Technology

The aim of this study is to evaluate the modelling of machining vibrations of thin-walled aluminium workpieces at high productivity rate. The use of numerical simulation is generally aimed at giving optimal cutting conditions for the precision and the surface finish needed. The proposed modelling includes all the ingredients needed for real productive machining of thin-walled parts. It has been tested with a specially designed machining test with high cutting engagement and taking into account all the phenomena involved in the dynamics of cutting. The system has been modelled using several simulation techniques. On the one hand, the milling process was modelled using a dynamic mechanistic model, with time domain simulation. On the other hand, the dynamic parameters of the system were obtained step by step by finite element analysis; thus the variation due to metal removal and the cutting edge position has been accurately taken into account. The results of the simulations were compared to those of the experiments; the discussion is based on the analysis of the cutting forces, the amplitude and the frequency of the vibrations evaluating the presence of chatter. The specific difficulties to perfect simulation of thin-walled workpiece chatter have been finely analysed. © Springer-Verlag London Limited 2010. Source

Gonzalo O.,Fundacion TEKNIKER IK4 | Quintana I.,Fundacion TEKNIKER IK4 | Etxarri J.,Fundacion TEKNIKER IK4
Advanced Materials Research

This paper presents a methodology to design and manufacture a chip breaker in a PCD turning tool. The objective is to avoid the surface roughness and chip evacuation problems produced by long chips in turning processes. An analysis of the process is made to design a suitable chip breaker shape for semi-roughing and finishing operations in aluminum turning. FEM simulation and experimental test are used to understand the chip formation and breakage processes leading to improved chip breaker geometry. The new designed geometries are micromachined with laser in the PCD tools, and the improvement in the chip control is proved experimentally. © (2011) Trans Tech Publication. Source

Tellaeche A.,Fundacion TEKNIKER IK4 | Robles B.,Fundacion TEKNIKER IK4
Proceedings of the 15th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2010

The exhaustive quality control is becoming very important in the world's globalized market. One of these examples where quality control becomes critical is the percussion cap mass production. These elements must achieve a minimum tolerance deviation in their fabrication. This paper outlines a machine vision development using a 3D camera for the inspection of the whole production of percussion caps. This system presents multiple problems, such as metallic reflections in the percussion caps, high speed movement of the system and mechanical errors and irregularities in percussion cap placement. Due to these problems, it is impossible to solve the problem by traditional image processing methods, and hence, a neural network has been tested to provide a feasible classification of the possible errors present in the percussion caps. ©2010 IEEE. Source

Sanda A.,Fundacion TEKNIKER IK4 | Garcia Navas V.,Fundacion TEKNIKER IK4 | Gonzalo O.,Fundacion TEKNIKER IK4
Materials and Design

Plates of Inconel 718 in precipitated state have been subjected to ultrasonic shot peening (USP), varying the distance from the radiating surface of the booster to the sample, the processing time and the material (WC/Co and steel) and number of shot balls, in order to study the effect of these parameters on the final state generated by the USP process. A change to more compressive residual stresses at the surface of the treated parts has been measured in all cases. For higher USP processing times and/or lower booster-sample distances, the degree of plastic deformation in the treated material increases, leading to a change to more compressive surface stresses and a higher density of impact marks in the treated surface. The same occurs when WC/Co balls are used instead of steel balls. The tendency to more compressive stresses reaches a saturation level after a certain processing time, when the system is not able to force the material to continue with more plastic deformation. If a higher quantity of balls is used, there will be less impacts of the shots with the surface and their energy will be lower (due to losses of energy after inelastic collisions). This diminishes the effect of the impacts in introducing compressive stresses and leads to less and shallower impact marks in the treated surface. © 2010 Elsevier Ltd. Source

Navas V.G.,Fundacion TEKNIKER IK4 | Gonzalo O.,Fundacion TEKNIKER IK4 | Bengoetxea I.,Fundacion TEKNIKER IK4
International Journal of Machine Tools and Manufacture

Machining processes induce a residual stress state in the machined part that, depending on its magnitude and sign, can be very detrimental to the service life of the machined components. This way, tensile residual stresses favour crack nucleation and propagation, leading to a reduction of fatigue life and corrosion and wear resistance. The final residual stress state in a piece depends on the material of the component and on the cutting parameters employed: cutting speed, cutting feed, depth of cut, kind of cutting tool (geometry, coating of the tool, etc), wear of the tool, lubrication, etc. Nevertheless, there is some lack of agreement in the literature regarding the specific tendency of residual stresses with each cutting parameter (feed and cutting speed) and there is not much literature about the effect of tool geometry and tool characteristics (coating). The present paper aims to put some light in this lack of agreement and complement the studies found in the literature. In this work, it has been studied the effect on the final surface stress state in AISI 4340 steel of cutting speed, feed, tool nose radius, geometry of the tool chip breaker and coating of the cutting tool. For this study surface residual stresses have been measured, by means of X-ray diffraction, in AISI 4340 steel bars subjected to turning tests using different cutting speeds (between 200 and 300 m/min), different cutting feeds (between 0.075 and 0.200 mm/rev), and cutting tools with two nose radius (0.4 and 0.8 mm), two different surface states (one coated by CVD and the other without coating) and two different geometries of the chip breaker. In all cases surface tensile residual stresses have been measured, tending to be more or less tensile (and consequently more or less detrimental to the service life of the machined component) depending on the cutting conditions and the characteristics of the cutting tool. In this work, not only the magnitude but also the orientation of the principal residual stresses has been determined. This is not commonly encountered in the literature, in spite of its significance: the direction of maximum residual stress is a critical direction because if it coincides with the direction of the stresses acting on the component as a result of the nominal load (load suffered by the component during its normal service), the service life of the part will be significantly affected, leading to possible premature failure of the component. That is the reason why knowing the orientation and not only the magnitude of principal residual stresses is of huge importance. © 2012 Elsevier Ltd. All rights reserved. Source

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