Patent GB-729179-A (GB)
Title: Improvements in or relating to apparatus for testing metals by alternate bending
Inventor: MIRONOFF NICOLAS
IPC: G01N3/34
Filed: 1953-02-26
Abstract: 729,179. Testing physical qualities of materials. TELEFONAKTIEBOLAGET L. M. ERICSSON. Feb. 26, 1953, No. 5425/53. Class 106 (2). In a testing apparatus for alternate bending of a test piece 33 between two pairs of jaws, one 6, 7 for clamping and the other 16, 17 for guiding the test piece, each jaw is supported on a separate plate and the two plates 1, 2 are pivotally connected together; the two parts of the guiding jaw are adapted to reciprocate in opposite directions, their relative relationship being controlled by a lever in accordance with the angular displacement of the plates about their pivot. The mechanism causing sliding of the two parts of the guiding jaws is also such that the distance between the supporting points of the two jaws, between which points the bending of the test piece is carried out, is varied with the angular displacement of the plates to maintain a constant length of deformation of the test piece whatever the bending angle of the latter. In addition, the mechanism is adjustable to modify the distance between the supporting points as a function of the thickness of the test piece and for preserving a certain ratio between the length of the deformed zone and the thickness of the test piece. Two plates 1 and 2, Figs. 1 and 2, are pivoted at 5 and have handles 3 and 4. The gripping jaws 6, 7 which are pivoted at 10 and 11 respectively can be acted on by a screw 12a to cause them to grip the test piece. The guiding jaws 16, 17 are slidable in guides 18, 19 pivoted at one end on pins 20, 21 and at the other end on pins 22, 23 eccentrically mounted in journals 24 and 25 turning'in openings in the plate 1. These journals are fast with the arms of levers 28 and 29 respectively interconnected by a rod 30. When the journals 24 and 25 are displaced angularly in one direction or the other under the control of an extension 28a of the lever 28, the slides 18 and 19 are simultaneously opened and closed, see Figs. 5 and 6. After adjustment of the spacing of the slides 18 and 19, according to the thickness of the test piece, the slides are locked in position by nuts on the pivot pins 22 and 23. The jaws 16 and 17 are -interconnected by a lever 36. Reciprocating motion is imparted to the jaws 16 and 17 by a cranked lever having arms 37 and 38, the lever being pivoted at 39 to the plate 1. The arm 37 has a slot 40, Fig. 8, engaging a pivot 41 fast with the plate 2. A slot 42 in the arm 38 houses a pivot 43 on a rod 44. Rod 44 is pivoted at one end to the sliding jaw 16, while its other end has a slot 46 engaging a pivot 47 on the rod 30. Reciprocating motion of jaws 16 and 17. When the plates 1 and 2 carry out relative angular movements about the pivot 5 the angular displacement of the pivot 41 fast with the plate 2 will cause the cranked lever 37, 38 to turn about its pivot 39 and thereby displace the rod 44, the sliding jaw 16 and consequently the jaw 17, by the action of the compensating lever 36. Also, for a given spacing between the jaws 16 and 17, by means of the lever 28a, the position of the pivot 43 of the rod 44 will be brought more or less closer to the pivot 39 and the amplitude of the longitudinal movement of the sliding jaws will be larger or smaller; in other words, the greater the spacing of the jaws 16, 17 the more the pivot 43 will be spaced from pivot 39 and the larger will be the longitudinal displacement of the jaws 16 and 17. To vary the length of the deformed zone of the test piece and to adapt the apparatus to different lengths of this zone with respect to the thickness of the test piece, the pivot 41, Fig. 10, may be adjustable in a slot 49 in a lever 48 fast with the plate 2. The value of the distance between the pivot centre of the shaft 5 and the pivot 41 has the effect of modifying the amplitude of the longitudinal displacements of the guide jaws 16 and 17. Bending action of apparatus. Figs. 11 to 14 show diagrammatically the movement of the jaws in bending a test piece first from a straight stage to maximum deflection in one direction, see Figs. 11 and 12, then the movements involved in bending the test piece back in a straightening stage, see Figs. 13 and 14, and finally the movements in bending the test piece to a maximum deflection in the reverse direction, see Figs. 15 and 16. In all the stages shown, the deformation zone " Z," measured by the length of the mean fibre "A," remains the same, whatever may be the bending angle. Figs. 17 and 18 show the bending conditions of two test pieces of different thicknesses. In these two cases, the sliding of the guide jaw 16 is strictly set according to the thickness of the test piece, so that the distance of the test piece end (point " a ") from the centre " o " of rotation of the jaws is such that a deformation in which the ratio of the length of the average fibre " A " to the thickness " E " of test piece 33 remains constant.