Dynamic Modeling and Dynamic Analysis of the Boring Machining System

342 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1986.The boring operation is a metal cutting process widely used in industry. The inherent properties of the long, slender boring bar make it susceptible to self-excited chatter during machining. The main focus of this thesis is directed at developing a system model which correctly describes the boring operation, applying modern control theory to perform dynamic cutting analysis, and exploring a systematic approach to evaluate the machining performance of a boring bar for the purposes of optimal boring bar structural design and process planning.In the development of the system model, the dynamic cutting force equation uniquely defines the dynamic cutting force as a function of the status of the tool motion. The regenerative mechanism during machining is replaced by the residual chip load. These distinguishable steps greatly facilitate the dynamic cutting analysis.An instrumented boring bar transducer is designed and tested to demonstrate the capability of detecting the dynamic cutting forces. A mechanistic boring force model built on the measured cutting force data is used to obtain estimates of the system parameters.In the dynamic cutting analysis, three-dimensional stability border surfaces are constructed based on the concept of the system complex frequency response. A system performance index is proposed for optimization of either a boring bar structure design or a selection of cutting data.The study of random vibration during machining provides new insights into the mechanics of surface generation. The developed random excitation model representing the nonhomogeneity of micro-hardness of the material being cut not only relates the micro-structures of the material to the generation of surface irregularities, but also quantitatively evaluates the effect of the cutting parameters on such generation. The possibility of evaluating the surface roughness through a simulation process may become very attractive in the future.Upon replacing relevant time-invariant parameters by time-varying parameters, the system model can be used to study the dynamic characteristics of intermittent boring operations. The perturbation method is used to obtain the criterion for determining the stability boundary condition.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD