BS 843-7:2010 pdf download – Advanced technical ceramics — Mechanical properties of monolithic ceramics at room temperature Part 7: C-ring tests

BS 843-7:2010 pdf download – Advanced technical ceramics — Mechanical properties of monolithic ceramics at room temperature Part 7: C-ring tests 6.4 Mechanical testing machine A mechanical testing machine capable of applying a force to the test jig at a constant displacement rate or at constant loading rate. The testing machine shall be equipped for recording the load applied to the test jig at any point in time. The accuracy and calibration of the testing machine shall be in accordance with EN ISO 7500-1:2004, Grade 1 (1 % of indicated load). For Method A, the testing machine shall be equipped with hard flat anvils with faces either fixed parallel to within 0,05 mm over the area to be used for testing, or self-aligning during testing. For Method B, the testing machine shall be equipped with a device for permitting two hard steel rollers to be inserted through the ring and supported at each end by yokes connected to the testing machine which permit a tensile force to be applied. Universal joints shall be incorporated into the load train to permit alignment and to minimise stress concentrations towards one face or other of the ring. NOTE Any suitable alternative arrangement may be used in which the load can be applied in compression mode using a lever system containing the loading rollers. Precautions shall be taken to avoid flying fragments from the test-piece during fracture. 6.5 Interface material Thin, compliant materials such as cardboard, metal foil or rubber sheet, to be placed between the test piece and the compression anvils (Method A) or steel rollers (Method B). 7 Test pieces Test pieces or test material shall be selected in accordance with the guidelines in EN 1006. If the test rings are to be cut from tube stock, select stock which is acceptably round and straight. This standard does not prescribe any particular dimensions for test pieces, but the following size ratios are recommended to avoid problems with alignment or validity of the calculation equations: a) 0,05 < (wall thickness/outer ring radius) < 0,5; b) 0,2 < (axial length/outer ring radius) < 1,0; c) 1,0 < (axial length/wall thickness) < 4,0. Cut or otherwise machine the side faces of the test pieces to a parallelism of better than 0,015 mm using a diamond saw with or without additional machining by lapping or surface grinding. This process shall introduce a minimum of damage such...