In the manufacturing operation of pressure sensors, autofrettage denotes the process of active ?overload? by subjecting the pressure sensor selectively once or several times to a pressure above the nominal pressure range. This process is applied, in order to achieve maximum stability, in particular 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 reaching the specified overload range, without resulting in zero-point shift or similar effects.
In Security , certain local areas of the sensor, where 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 by way of autofrettage is an integral part 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 a complicated FEM simulation and extensive test series.
Caution ? no experiments of your! However, it must not be concluded that every sensor will automatically reap the benefits of subjecting it to autofrettage. Autofrettage can only just be used for ductile materials, but for no reason for brittle ones. Conditioning should be scheduled and carried out very selectively and with great care through the production stages. Ill-considered ?overpressurising? of Promising 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, an improvement in instrumentation will only be achieved, if, by hit or miss.g