GB512035A - Improvements relating to fatigue-testing machines for materials - Google Patents

Abstract

512,035. Testing fatigue of materials. DE HAVILLAND AIRCRAFT CO., Ltd., and CLARKE, K. W. Feb. 25, 1938, No. 6036. [Class 106 (ii)] The test piece is held in chucks' one at least is oscillated to produce repeated bending while another is oscillated to produce repeated torsion. A bed 10 is provided with a longitudinal T-shaped groove along which slide stocks 12, 13. The stock 12 has ball bearings 14, 15 for a shaft 16 connected by a coupling 17 with a shaft 18 driven by an electric motor. The stock 13 has bearings 19, 20 for a shaft 21 which is connected by a coupling 22 with the part 16A of shaft 16. The coupling is splined and allows for adjustment of the stocks nearer and further apart and also of the adjustment of the relative phasing of the shafts. The stock 12 is formed with brackets 23 supporting a shaft 24 transverse to the shaft 16. A block 27 is mounted on the shaft 24 provided 'at one end with a chuck 28 for gripping a specimen 54. A spigot 30 on the chuck engages a recess in the block a compression spring 31 being arranged between a flange 32 and an inwardly directed flange closing the recess. A flat lip 34 co-operates with the flat top of the block to prevent rotation of the chuck on the block. At the other end of the block is a pin 35 upon which is mounted an annular bearing race with an outer spherical surface co-operating with a ball race on the lever 36. This allows pivoting of the block 27 about the shaft 24. The lower end of lever 36 is borne in a similar bearing on a crank pin 38 the ends of which are engaged in slots 39, 40 in bosses 41, 42 secured to the extremities of shafts 16, 16A. The pin 38 is located eccentrically of the shafts and the eccentricity may be adjusted by screws 43 to alter the stroke of the lever 36. The stock 13 has brackets 44, 45 supporting a shaft 48 extending from the end of the block 49 having a lug 50 forming a pivot bearing for a lever 51.. The block is apertured at 52 to accommodate the upper end of the bracket 45' on which is formed a bearing 47 for the end of the block 49 in alignment with shaft 48. The end of the block is formed as a specimen grip. The lower end of rod 51 finds a ball bearing on an adjustable eccentric pin 57. The rocking of block 27 submits the specimen 54 to bending while the rocking of 49 at the same time submits it to torsion. Electric contacts may be arranged in connection with the spring chuck to stop the motor on failure of the test piece. There may be three stocks the centre one applying torsion and the outer ones bending. Gearing may be introduced to vary the frequency of the torsional vibration relative to bending.