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 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 many years 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 Document , 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. Worry 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, must be determined individually for every sensor design by means of an elaborate FEM simulation and extensive test series.
Caution ? no experiments of your! However, it should not be figured every sensor will automatically reap the benefits of subjecting it to autofrettage. Autofrettage can only be utilized for ductile materials, but for no reason for brittle ones. Conditioning should be scheduled and completed very selectively and with great care through the production stages. Ill-considered ?overpressurising? of pressure sensors by laymen who like experimenting will 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 manner, an improvement in instrumentation will only be achieved, if, by hit or miss.