Novel friction sensors for bulk and sheet metal forming

Three novel friction sensors designs for bulk and sheet metal forming processes were developed, optimised, prototyped and tested.; The first design was of a diaphragm sensor which consisted of a diaphragm whose outer surface was flush with the surface of the tool and whose inner surface was instrumented with strain gauges. Normal and shear loadings could be evaluated from strain gauges signals. The sensor was tested using a special test rig that was able to apply known normal and shear loads independently.; The second design was of sealed strain gauges sensor which consisted of a cantilever with a cap at its top that was flush with the tool's surface. Normal and shear loadings could be evaluated from the signals of strain gauges at the cantilever. The sensor was tested in an experimental metal roll where the applied torque and roll separating force could be used to validate the sensor output for shear and normal loads.; The third design was of sealed piezo ceramics sensor which consisted of a metal post supported at its base by piezo ceramic elements. Normal and shear loadings could be evaluated from the piezo signals. The sensor was tested in a cup draw die plate using a hydraulic press and dead weights to apply known normal and shear loads respectively.; All sensors had continuous surfaces at the interface with the workpiece so as to achieve minimum effect both on the friction regime and on the workpiece. The sensors were able to measure normal and friction forces. Further enhancements of the sensors are needed to reduce size and to increase sensitivity and spatial resolution.