Modelización de la evolución del desgaste en herramientas de corte

Resumen

In this Doctoral Thesis the time-space modeling of tool wear is studied. This work begins with a brief review of fundamentals on machining and wear. In this way it was achieved a general knowing about tool wear evolution and local variables behavior (normal stress ?n, slide velocity Vs and interface temperature Tint). It was made a chronological review of the most important tool wear models proposed trough the last 60 years. The most of the studied models depends only on local variables as interface temperature Tint. It also was observed that the Arrhenius' Equation is used into the most of characteristic wear equations. An analysis of sensitivity was made to study the Arrhenius' response to interface temperature Tint perturbations and to prove the effectiveness of this equation to model tool wear. Also an Arrhenius based wear model was used to simulate wear trends. The simulated results were compared to experimental ones. The sensitivity analysis showed that the Arrhenius' Equation presents a conditioned sensitivity to simulate correctly the changes observed in experimental tool wear rates. The results obtained by using the Arrhenius based model confirm the analytical conclusion and describe a constant tool wear rate. All of this suggests that tool wear models depending exclusively on local variables (i.e. Tint) are not able to simulate tool wear evolution. As a result of this analytical process it is proposed the fundamental hypothesis to model wear in this Doctoral Thesis: The wear rate is function of time and local variables. In order to apply the fundamental modeling hypothesis it has been developed a new methodology based on dimensional analisys (Vaschy-Buckingham Theorem), and the discretization of worn surface. As a result is obtained a differential equation wich describe the wear rate as a function of dimensionless variables ??, which combine the time and wear variables on contact interface (?n, Vs and Tint). To model tool wear by using the methodology proposed in this work it is necessary to know the local variables distribution on contact interface. This information has been obtained from numerical models for orthogonal cutting. To develop the numerical models it has been used the comercial code DEFORMTM- 2D/3D Ver 11.0. This models has been validated by using experimental values of cutting formces, contact length and tool temperatures. The experimental information has been taken from specialized literature. With the numerical information for local variables ?n, Vs and Tint it has been developed a new wear model for uncoated plain carbide tool (WC) and AISI 1018 steel as workpiece material. The wear model developed was validated for experimental trends of maximum crater KT and wear profiles for different cutting speed and feed. The results are satisfactories.