The Twist Compression Test is used to
evaluate lubricants and die materials for application in
metalforming processes.
The Twist Compression Test is a
tribometer designed to measure friction and evaluate adhesion in
metalforming. The TCT is effective because of several critical
features.
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Contact pressures can be set to
match the process
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Flat contact ensured through
self-aligning tooling
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Depletion of lubricant without
replenishment ensures boundary contact with liquid
lubricants
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Simple contact model allows
friction to be determined from Amonton’s laws of friction
“the Frictional force is proportional to normal force, and
it is independent of the size of the apparent contact area”
(Schey, Tribology in Metalworking)
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This test measures the transmitted
torque between a rotating annular cylinder and a lubricated flat
sheet specimen. The 25mm (1”) diameter annular cylinder is
driven by a hydraulic motor for smooth delivery of the applied
torque at speeds up to 30 RPM (90 inches/minute). The pressure
may be adjusted up to 35,000 psi to best duplicate the
tribological conditions of the metalforming process being
studied. Data is collected electronically and the coefficient of
friction is calculated from the ratio of transmitted torque to
applied pressure.
The TCT is best used as a
comparative rather than an absolute test. The simplicity of the
TCT and good laboratory practice minimizes variations. However,
it is advisable to include a reference for each series of
evaluations.
