A cutting tool is much harder than the workpiece. Yet the tool we
A. Extra hardness is imparted to the workpiece due to coolant used
B. Oxide layers on the workpiece surface impart extra hardness to it
C. Extra hardness is imparted to the workpiece due to the severe rate of strain
D. Vibration is induced in the machine tool
Please scroll down to see the correct answer and solution guide.
Right Answer is: C
SOLUTION
Concept:
Cutting action involves shear deformation of work material to form a chip, and a chip is removed, a new surface is exposed. Tool wear is a common phenomenon is metal cutting.
Major causes of tool wear are
(1) high contact temperatures at the tool-chip and tool–work-piece interfaces that lead to the softening of tool material and promote diffusion and chemical (oxidation) wear
(2) high contact pressures at these interfaces
(3) the cyclic nature of the chip formation process, which can cause cracking because of thermal fatigue
During machining, the strain also occurs in work material and strain hardening takes place of work and it becomes harder.
