Modeling of the cylinder boring process for prediction of cutting force, temperature and surface error
Subramani, Gnanasambandam
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https://hdl.handle.net/2142/22939
Description
Title
Modeling of the cylinder boring process for prediction of cutting force, temperature and surface error
Author(s)
Subramani, Gnanasambandam
Issue Date
1991
Doctoral Committee Chair(s)
DeVor, Richard E.
Kapoor, Shiv G.
Department of Study
Mechanical Science and Engineering
Discipline
Mechanical Science and Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Language
eng
Abstract
In this thesis, models are developed for characterization of the cylinder boring process, a process used for machining cylinder bores in cast engine blocks. The models are used for predicting the lack of cylindricity of machined cylinder bores, also called surface error, which results in poor engine performance and excessive wear of cylinders and pistons. Surface error arises from two causes, namely, the elastic deflection of the bore wall due to cutting forces and the thermal expansion of the cylinder bore during machining. The prediction of cutting forces is achieved through the development of a mechanistic model which accounts for the effect of cutting condition and tool geometry variables on chip load and the magnitude and orientation of cutting forces. Since during machining there is an inherent coupling between the cutting process and the structural vibration of the machining system due to cutting forces, a procedure for computation of process dynamics, using finite element analysis, is developed which invokes this coupling. The predicted cutting forces are used along with an influence coefficient database of the engine block and fixturing to calculate the component of surface error resulting from elastic deflections of the bore wall during machining.
The temperature field in the cylinder bore during machining is computed through the development of analytical solutions using the method of integral transforms. In this derivation, the tool-work interface is modeled as a helically moving volumetric heat source. The derived temperature field is used to compute the magnitude of surface error resulting from thermal expansion of the cylinder bore during machining. Experiments have been conducted on a cylinder boring test set-up to study the effect of cutting condition and tool geometry variables on cutting forces, bore temperatures, and surface error. The measured cutting force and temperature data have been used to calibrate and verify the developed models. Comparisons between measured and predicted cutting forces, bore temperatures, and surface error show very good agreement. Simulations performed to study the effect of cutting speed, feed, depth of cut, and tool rake angles on surface error show that feed and depth of cut significantly affect surface error. The use of the developed models for designing the process through sensitivity calculations is discussed.
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