Phd

Ph.D Thesis:

Title: Experimental investigations on influence of emulsifier content in cutting fluids on
machining performance and occupational environment

Abstract
The survival of present day industry is decided by its ability to produce high quality cost
effective products in order to meet the challenges. However, several factors that contribute to the
idle and down times associated with production processes have been hindrances in realizing this
dream. Machining is one of the key manufacturing processes and accounts for a majority of the
product cost. The down times in machining are mainly due to the frequent tool changes as it
wears off. Hence, estimation and remedial measures for tool wear are of prime interest to the
researchers.
Tool wear is dominantly affected by cutting temperatures and forces. Hence application of
cutting fluids that act as both lubricants and coolants is looked upon as one of the promising
solutions to reduce tool wear. Of the several choices available, water miscible oils are the most
popularly used cutting fluids owing to the confluence of cooling properties of water and
lubricating abilities of oil. Though much work is carried out on the performance of the fluids, the
influence of individual ingredients in the fluids on tool wear is not much investigated.
Further, the usage of the cutting fluids is limited by their vulnerability to microbial
contamination that causes several health hazards to the workers apart from disposal problems.
Though study of stored fluids for their shelf life is reported exhaustively in literature, working
fluids are hardly tested.
In the present work, cutting fluids of varying emulsifier content are formulated and are tested for
several basic properties that govern the effectiveness of fluids. Properties like thermal
conductivity, kinematic viscosity, pH value, water separability, flash and fire points are
estimated through series of standard tests. The measured properties provide basis for assessing
the machining performance and resistance to microbial contamination of the fluids. Microbial
contamination of the fluids under stored and simulated working conditions is measured over a
period of one month. Simulation of working conditions is done by a special set-up designed for
the purpose. The bacterium in the fluid is isolated and identified to decide on the remedial
actions. The performance of the fluids is assessed while machining AISI 1040 steel. Cutting
forces, cutting temperatures, surface roughness of the samples and tool wear are measured during
the machining tests. The effectiveness of the fluids with varying emulsifier contents as
quenchants is assessed by measuring the hardness of machined samples. The results are validated
by Jominy end quench test.
The experimental results clearly indicate the decisive role of emulsifier content in cutting fluids.
A mathematical model based on regression is proposed to estimate tool wear, under proposed
machining conditions with cutting fluids of varying emulsifier contents. The effect of emulsifier
content is included in the model. Analysis of variance is carried out to justify the selection of
variables considered in the model. To facilitate online estimation of tool wear, an artificial neural
network model is postulated. Both the models are validated by comparing the predicted values
with the experimental results.