In the manufacturing operation of pressure sensors, autofrettage denotes the procedure of active ?overload? by subjecting the pressure sensor selectively once or several times to a pressure above the nominal pressure range. diaphragm seal is applied, to experience maximum stability, specifically of the zero point, in later operation. Assuming the right design of the sensor, autofrettage enables a long time of trouble-free operation of the sensors even at high load cycles achieving the specified overload range, without leading to zero-point shift or similar effects.
In autofrettage, certain local areas of the sensor, in which through the selective overload the yield point of the sensor material is locally exceeded, become plasticised, resulting in a permanent change of the instrumentation characteristics. This selective influence on the structural conditions through autofrettage can be an integral part of the development of the sensor and of the associated manufacturing process. Which pressure gauge octa is put through and how often, must be determined individually for each sensor design by means of an elaborate FEM simulation and extensive test series.
Caution ? no experiments of your! However, it must not be concluded that every sensor will automatically benefit from subjecting it to autofrettage. Autofrettage can only just be utilized for ductile materials, but for no reason for brittle ones. Conditioning must be scheduled and carried out very selectively sufficient reason for great care through the production stages. Ill-considered ?overpressurising? of pressure sensors by laymen who like experimenting will not only damage the sensor permanently, but also bring about dangerous preliminary damage and subsequently possibly in accidents caused by fatigue and bursting of the sensor. In this manner, an improvement in instrumentation is only going to be achieved, if at all, by hit or miss.