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. Manipulative is applied, in order to achieve maximum stability, specifically of the zero point, in later operation. Assuming a suitable 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 regions 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 is an integral section of the development of the sensor and of the associated manufacturing process. Which pressure the sensor is put through and how often, should 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 be used for ductile materials, but under no circumstances for brittle ones. Uncovered should be scheduled and carried out very selectively and with great care during the production stages. Ill-considered ?overpressurising? of pressure sensors by laymen who like experimenting can not only damage the sensor permanently, but additionally bring about dangerous preliminary damage and subsequently possibly in accidents caused by fatigue and bursting of the sensor. In this manner, a noticable difference in instrumentation will only be achieved, if at all, by hit or miss.