Knowledge of tool/material contact stresses, especially in thetool design stage, is important in order to evaluate the dimensionalaccuracy of the part being produced and reduce the risk of tooldamage. The intensity and distribution of contact stresses producevariable frictional resistance at the tool/material interface andhence influence the mode of plastic deformation. Using pressure pins,experimental techniques however enable the measurement of normalpressure and in some cases the friction resistance at the interface.This paper describes an experimental methodology suitable for themeasurements of contact stresses and friction forces at thetool/material interface under hot working conditions. It employs anewly designed thermal pin which incorporates a column of zerconiathat acts as a thermal break between the deforming material thermalconditions and the sensitive measuring device. The mechanism offorces at the interface is measured using three pins mounted atdifferent orientation to the tool surface. Results from experimentsare also compared with theoretical predictions in order to examinethe progress of stress intensity along the tool/material interface.
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