Question

In rolling, the term "frictional shear stress" is used to describe which of the following?

• A. The resistance of the workpiece to deformation during rolling
• B. The pressure exerted by the rolls on the material
• C. The tangential force at the work-roll interface causing plastic deformation
• D. The normal stress experienced by the workpiece as it enters the roll gap

Hint:

Frictional shear stress in rolling is the tangential stress at the roll-workpiece interface that helps grip and deform the metal — it's essential for effective rolling.

Answer 1

The Correct Option is C

In the rolling process, deformation of the workpiece occurs due to compressive forces applied by rotating rolls. However, for the material to enter the roll gap and be drawn through, there must be sufficient frictional force at the roll-workpiece interface.
The frictional shear stress refers to the tangential force per unit area acting at this interface. It enables the rolls to grip the workpiece and drag it through the roll gap, contributing to the plastic deformation process.
- It is not the resistance of the material itself to deformation (which is a material property), - Nor is it the normal pressure, which acts perpendicular to the surface.
Hence, the correct definition of frictional shear stress is the tangential force that facilitates plastic deformation at the contact surface between the roll and the material.