Date of Award

5-2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Mechanical Engineering

Advisor

Huang, Yong

Committee Member

Fadel , Georges

Committee Member

Kurfess , Thomas

Committee Member

Ziegert , John

Abstract

Machining is the most widely used and efficient material removal process, and tool wear in machining is usually of great interest in order to improve machining efficiency and effectiveness. Cutting tool wear patterns such as the flank and crater wear and the dead metal zone (DMZ) may induce the cutting tool geometry variation in machining. As a result, cutting forces may increase or decrease due to the change of tool effective cutting geometry during machining operations. A quantitative understanding of and the ability to predict cutting forces in relation to tool wear are important to the tool life estimation, chatter prediction, and tool condition monitoring. Most available force models are limited to fresh tool conditions or worn tool conditions only considering the flank wear. Furthermore, the effect of DMZ on cutting forces, especially when a chamfered tool is used, is frequently ignored. The objective of this dissertation is to analytically model the combined effect of the crater and flank wear as well as the effect of DMZ on cutting forces in 2D and 3D turning.
Using turning as the most common machining example, analytical 2D and 3D force models are first proposed to model cutting forces under worn tool conditions with both crater and flank wear presented using the slip-line based plasticity theory. An uncertainty study is further proposed to validate the proposed 2D force model using the noninformative Bayesian linear regression approach in cutting CK45 steels. The validated 2D force model is further extended for 3D oblique cutting by using the geometric and coordinate transformations based on the cutting chip discretization, and thedeveloped 3D force model is validated in hard turning of hardened 52100 bearing steels. The effect of stagnant DMZ on cutting forces is studied based on a three-zone model. The total energy consumption under the DMZ zone is modeled due to excess, extrusion, and friction using a slip-line approach. Satisfactory match between the predictions and the measurements has been achieved in turning of P20 mold steels. An improved modeling accuracy is also observed when compared with a previous modeling effort.
This study leads to a new turning force models under the combined effect of flank and crater wear in 2D and 3D cutting, a new Bayesian analysis-based methodology to evaluate force measurements and predictions, and a new approach to model the effect of DMZ on cutting forces in using chamfered or worn tools.

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