GB1275262A - Apparatus for estimating stress relaxation and variation in modulus of materials - Google Patents

Abstract

1275262 Testing materials B P CHEMICALS INTERNATIONAL Ltd 17 June 1969 [19 June 1968] 29098/68 Addition to 1123213 Heading G1S An apparatus for estimating relaxation and variation in the modulus of materials comprises a pivoted balance arm 4 having means 2 to hold the test material 3, means 6 for applying tension to the arm, means for increasing and decreasing the applied tension to return the arm to the undisplaced position and means for recording the tension. The tension of spring 6 is varied by movement of nut 7 along threaded rod 8 which may be turned in either direction by reversible motor 9. The motor may only stop when beam 13 interrupts light from 12 passing to photo-cell 32 so that the tension is varied in equal steps corresponding to one revolution of the shaft of motor 10, the number of units of tension being recorded on counter 14. Arm 4 carries a piece 18 which interrupts light from source 16 to photo-cell 15 when the arm 4 is in a displaced position, causing the control circuit to energise motor 10. To measure relaxation, specimen 3 surrounded by oven 11 is stressed by action of fluid activated piston 33 in cylinder 19, causing part 18 to activate motor 10 until the arm is returned to the undisplaced position by increase of tension in spring 6. As specimen 3 extends due to relaxation, part 18 again activates motor 10, which turns one revolution which is sufficient to withdraw part 18 from the light path thus decreasing the tension by one unit. The tension and the time are printed out in recorder 14 at each reduction of tension. To measure the modules of specimen 3, at times determined by timer 23, a predetermined strain is applied to specimen 3 and the arm balanced as above. The time and stress are then printed out, and the strain removed from the specimen. The control circuit allows the measurements to be carried out automatically. A transducer may be attached to the arm pivot 5, or to depending arm 17 and coupled via a suitable conditioning device to a recorder to record the movement of the arm.