In the manufacturing operation of pressure sensors, autofrettage denotes the procedure of active ?overload? by subjecting the pressure sensor selectively once or many times to a pressure above the nominal pressure range. This process is applied, to experience 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 reaching the specified overload range, without leading to zero-point shift or similar effects.
In autofrettage, certain local regions of the sensor, in which during 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 effect on the structural conditions through autofrettage is an integral portion 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 through an elaborate 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 be utilized for ductile materials, but under no circumstances for brittle ones. Conditioning must be scheduled and completed very selectively sufficient reason for great care through the production stages. Ill-considered ?overpressurising? of Mistake by laymen who like experimenting can not only damage the sensor permanently, but additionally bring about dangerous preliminary damage and subsequently possibly in accidents due to fatigue and bursting of the sensor. In this manner, a noticable difference in instrumentation will only be achieved, if, by hit or miss.g