Generalized physically based modeling of machining processes and its verification.

摘要

The capability to analytically predict output parameters of machining processes such as the chip flow angle and cutting forces for any sets of operating conditions will lead to optimization and development of machining operations. A physically based model is developed for the analysis of commonly encountered 3D metal cutting processes using arbitrarily oriented flat-faced tools.; In the upper bound analysis module, the projection of the uncut chip area on the rake face is divided into a number of elements parallel to an assumed chip flow direction. The area of each of these elements is used to find the area of the corresponding element on the shear surface using the ratio of the shear velocity to the chip velocity. Summing up the area of the elements along the shear surface, the total shear surface area is obtained. A new approach is introduced to obtain the friction area keeping the tool-chip contact length the same as in an orthogonal machining process, rather than keeping the tool-chip contact area constant as previously done. The cutting power is obtained by summing the shear power and the friction power. The actual chip flow angle and chip velocity are obtained by minimizing the cutting power with respect to both these variables. Unlike most of the previous studies that consider small values of the rake and inclination angles, a general formulation valid for arbitrary values of the inclination and rake angles is presented. The shape of the curved shear surface, the chip cross section and the cutting force obtained from this model are also presented. It is found that using this upper bound model, the chip flow angle is predicted accurately, but contact length and cutting forces are underpredicted.; In the 2D machining analysis module, Oxley's analysis of machining the most complete machining theory presented to date, has been extended to a broader class of constitutive equations and materials. The Johnson-Cook material model, Maekawa's history dependent power law material model and the MTS model are used to represent the mechanical properties of the material being machined as a function of strain, strain rate and temperature. A few changes are introduced into Oxley's analysis to improve the consistency between the various assumptions.; To improve the force prediction capability of the generalized upper bound model, a hybrid model is presented, wherein the upper bound analysis module is used for prediction of the chip flow angle, and is followed by application of the extended Oxley's analysis in the equivalent plane to predict cutting forces. (Abstract shortened by UMI.)