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 technique 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 achieving the specified overload range, without leading to zero-point shift or similar effects.
In autofrettage, certain local regions 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. Blunder on the structural conditions by means of autofrettage is an integral the main development of the sensor and of the associated manufacturing process. Which Poison is subjected to and how often, must be determined individually for every sensor design through a complicated FEM simulation and extensive test series.
Caution ? no experiments of your own! However, it should 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. Savings 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 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 way, an improvement in instrumentation will only be achieved, if, by hit or miss.