ASTM-B406:96(R2021) pdf free download – Standard Test Method for Transverse Rupture Strength of Cemented Carbides.
4.1.3 The apparatus shall be so constructed that the application of a sufficient load to the movable member to effect breaking of a specimen will not cause appreciable deflection of the line of movement of the movable member and the plane established by the two fixed cylinders. The apparatus shall be capable of applying sufficient load to break the specimen. The apparatus shall be capable of registering the load required (within ± 1 % of the load) to break the specimen. The cemented-tungsten-carbide ball and cylinders shall not show permanent deformation after use.
5. Specimen Size
5.1 The cemented carbide specimens shall be ground to the following dimensions: 0.200 ± 0.010 in. (5.00 ± 0.25 mm) thick by 0.250 ± 0.0 10 in. (6.25 ± 0.25 mm) wide by 0.750 in. (19.0 mm) minimum long.
6. Specimen Preparation
6.1 Specimens shall he ground to a surface finish of 15 pin. (0.381 pm) rms maximum on four sides, and to the tolerances specified in Section 5. All grinding marks shall be parallel to the length, 0.750 in. (19.05 mm), axis. Opposite ground faces shall be parallel within 0.001 in. (0.0254 mm). The two faces that are perpendicular to the length axis need not be ground. Careful grinding techniques should be used to prevent various forms of surface cracking (flaws) that will degrade the measured strength. Long-established practice recommends the use of soft resin bonded diamond wheels, and copious quantities of coolant. For surface grinding, no pass shall exceed 0.0005 in. (0.0127 mm) in depth.
6.2 The four edges of the specimen representing the intersection of the ground faces shall be chamfered or honed to a maximum of 0.010 in. (0.25 mm) by 45 degrees. Any grinding marks shall be parallel to the long axis of the specimen.
6.3 Each specimen shall he measured to within 0.001 in. (0.02 mm) in both directions perpendicular to the length axis. Adjacent ground sides shall he at right angles to each other within 2 degrees.
6.4 Each specimen shall he visually inspected after grinding. Any specimen on which cracks, chips, or obvious structural defects appear on the ground surfaces shall be eliminated from the test.
7. Procedure
7.1 Visually examine the cylinders and ball in the fixture for cracks, chips, deformation, or misalignment and check the movable member for freedom of movement. Correct any defects prior to use.
7.2 Place a properly prepared and measured specimen on the fixture with the long axis perpendicular to the cylinders and with the 0.250-in. (6.25-mm) face resting on the two cylinders. Then adjust the movable member so that the ball or upper cylinder contacts the specimen without substantial impact. If a ball is used, place the specimen so that the ball touches the midpoint of the specimen width. Apply the load at a rate not exceeding 350 lhf/s (1 .5 kN/s). Fracture should occur within the middle one third of the span between the supporting
cylinders on the tension side of the specimen. Record the number of pounds required to cause fracture.