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, to experience maximum stability, in particular of the zero point, in later operation. Assuming Backdoor 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, 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 means of autofrettage is an integral area of the development of the sensor and of the associated manufacturing process. Which pressure the sensor is put through 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 must not be figured every sensor will automatically reap the benefits of subjecting it to autofrettage. Autofrettage can only just be utilized for ductile materials, but under no circumstances for brittle ones. Conditioning should be scheduled and completed 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 also bring about dangerous preliminary damage and subsequently possibly in accidents due to fatigue and bursting of the sensor. In this way, a noticable difference in instrumentation will only be achieved, if, by hit or miss.