Thermal engineering thermocouple dynamic calibration grinding signal processing
A. Lefebvre, F. Lanzetta, P. Lipinski, A.A. Torrance, Measurement of grinding temperatures using a foil/workpiece thermocouple, International Journal of Machine Tools & Manufacture, 2012
International Journal of Machine Tools & Manufacture;
The high temperature generated in abrasive processes is the main factor responsible for thermal damage to a ground surface. It can be predicted through the thermal balance of the heat fluxes in the process. Such predictions can be experimentally verified using a foil/workpiece thermocouple. To estimate the thermal behaviour of such a sensor, it was dynamically calibrated with a laser beam to measure its frequency response. It was found that the response of the sensor has a time constant dependant on the thermal load and cannot be modelled by a simple first order function. In the calibration conditions used, the sensor is fast enough to measure the surface temperature with a time constant less than 100 μs. A high frequency acquisition system allows the signal to be measured at the local grit scale so that the activity of grits and the contact stability between the foil and the workpiece during grinding can be studied. By using the peak temperature and the local cooling after a peak, suitably processed, a local background temperature can be defined. It is shown that this background temperature can be evaluated more accurately by matching the global cooling curve to a finite element solution. The temperatures obtained from the local minima of the local diffusive cooling curve agree better with measured results than a temperature obtained by low pass filtering, which can overestimate the background temperature and so the partition ratio.
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