TIRING TESTING STAND

The invention relates to a fatigue test bench for collets with ribs used in the manufacturing of self-centred devices in the field of machine engineering. In accordance with the invention, the fatigue test bench consists of a lower pressure plate (15) and a pin (13) on which a test sample is placed. The lower pressure plate (15) is equipped with a helical groove (b) on which the lower end of a coil spring (16) is wound up. The upper end of the coil spring (16) is wound up on another helical groove (c) located in an upper pressure plate (17). The force generated by the coil spring (16) and the stress force of the fatigue test sample are adjusted through a dowel pin (18) and blocked by means of a nut (19). The dowel pin (18) operates an inside threaded bushing (20) supported by the upper pressure plate (17,) through a pressure bearing (21). The bushing (20), through the inside thread, moves a threaded rod (22), which, at its turn, moves the lower pressure plate (15), which results in the coil spring (16) compression. The axial stress of the test sample is applied by a gliding slide (11) that glides on guides (a). The gliding slide (11) may be moved using a radial ball bearing (9) connected to an eccentric (8). The actual stress on the test sample is equal to the difference between the force generated by an eccentric (8) and the force generated by the coil spring (16).