DEVICE AND METHOD FOR INDICATING IF A FASTENING ELEMENT HAS REACHED A TENSILE YIELD LIMIT LOAD.

摘要

Device (1) and method for indicating if a fastening element (3) at fastening in a piece (5) has reached a tensile yield limit load. The fastening element comprises a threaded shaft (7) comprising a magnetostrictive material. The device comprises means (9, 12) for generating an alternating magnetic field that penetrates the shaft, means (9, 14) for measuring a physical quantity that depends on the momentary magnetic susceptibility of the shaft and a control unit (16) adapted to detect a significant change of the physical quantity and determine and indicate if the shaft of the fastening element has reached the tensile yield limit load.