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In the manufacturing operation of pressure sensors, autofrettage denotes the procedure of active ?overload? by subjecting the pressure sensor selectively once or several times to a pressure above the nominal pressure range. ไดอะแฟรม is applied, in order to achieve maximum stability, specifically of the zero point, in later operation. Assuming ไดอะแฟรม ซีล of the sensor, autofrettage enables many years of trouble-free operation of the sensors even at high load cycles achieving the specified overload range, without resulting in zero-point shift or similar effects.
In autofrettage, certain local regions of the sensor, in which through the selective overload the yield point of the sensor material is locally exceeded, become plasticised, producing a permanent change of the instrumentation characteristics. This selective effect on the structural conditions by means of autofrettage can be an integral the main development of the sensor and of the associated manufacturing process. Which pressure the sensor is subjected to and how often, must be determined individually for each sensor design through an elaborate FEM simulation and extensive test series.
Caution ? no experiments of your own! However, it must not be figured every sensor will automatically benefit from subjecting it to autofrettage. Autofrettage can only be utilized for ductile materials, but for no reason for brittle ones. Conditioning must be scheduled and carried out very selectively sufficient reason for great care during the production stages. Ill-considered ?overpressurising? of pressure sensors by laymen who like experimenting will not only damage the sensor permanently, but additionally result in 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.