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Title:Evaluation of the atomization-based cutting fluid spray system in milling of titanium alloy
Author(s):Ganguli, Surojit
Advisor(s):Kapoor, Shiv G.
Department / Program:Mechanical Science & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Atomized droplets
Titanium alloy
Machining performance
Abstract:Titanium alloys are considered difficult to machine materials because of poor thermal conductivity and long elongation to break ratio, which makes it difficult to dissipate heat generated during cutting process. Therefore, effective cooling and lubrication effects are vital during machining of these alloys. Recently, it has been shown that an atomization-based cutting fluid (ACF) spray system can effectively cool and lubricate the cutting zone during turning of Ti-6Al-4V, leading to significant improvement in machinability of titanium alloys. However, the efficacy of the ACF spray system is yet to be tested for other machining operations that are different from turning, like milling. The droplet impingement dynamics in milling are different than that in turning because of the presence of a rotating cutting tool as opposed to a stationary single point cutting tool in turning. Also, milling is an intermittent cutting process that gets affected by thermal shock caused by cutting fluid. The research presented in this thesis investigates the effectiveness of the ACF spray system in end-milling of a titanium alloy, Ti-6Al-4V. To accomplish this, an experimental study has been conducted in two phases. During the first phase, the experiments are conducted to study the role of various combinations of spray parameters on cutting forces and select the one that has the least cutting forces. In the second phase, machining experiments are conducted, using the spray parameters selected in phase one, to assess the machinability of titanium alloy for different cutting fluid application methods,viz., ACF system, flood cooling and dry cutting, and evaluate the effectiveness of ACF spray system for different machining conditions. It is concluded from Phase 1 experiments that the cutting forces are the least for those spray parameters for which the velocity of the droplets is well within the spreading regime. Furthermore, a numerical model, based on Discrete Phase Modeling approach and Eulerian Wall Film model, of an ACF spray system has been developed and used to simulate the liquid film formation on a rotating cylindrical surface, to explain the variation in the experimentally observed cutting forces for different combinations of spray parameters. The end-milling experiments show that the presence of carbon dioxide in the droplet carrier gas is responsible for cooling the cutting zone more effectively in milling than what could be achieved in its absence. As a result, tool life increases by 50% when the droplet carrier gas is a mixture of air and carbon dioxide as compared to the case where droplet carrier gas has only air. Tool life experiments show that the ACF spray system outperforms other cutting methods, in three areas critical to access machinability, namely cutting forces, surface roughness and tool wear. Using the ACF spray system leads to uniform tool flank wear, which results in lower cutting forces and higher surface finish, and the tool life extends upto 75% over flood cooling. Additionally, chip morphology analysis reveals that using ACF spray system leads to the formation of shorter and thinner chips, as compared to that when flood cooling is used.
Issue Date:2015-07-23
Rights Information:Copyright 2015 Surojit Ganguli
Date Available in IDEALS:2015-09-29
Date Deposited:August 201

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