BS ISO 28704:2011 pdf download – Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for cyclic bending fatigue of porous ceramics at room temperature 5 Test piece 5.1 Test piece size The shape of a test piece shall be a beam of uniform rectangular cross-section. Its standard dimensions shall be 70 mm ± 0,5 mm in total length, 8,0 mm ± 0,1 mm in width, and 6,0 mm ± 0,1 mm in thickness. The parallelism between the upper and lower surfaces of the test piece shall be better than 0,02 mm, as specifed in ISO 1101. The longer edges shall be rounded or chamfered by an amount of 0,1 mm to 0,3 mm, as given in Figure 4. This chamfering shall be carried out with caution so as not to introduce defects resulting in a fracture initiation site. The chamfering is not necessary when the grain size of material is larger than 0,1 mm. Before carrying out the test, the width and thickness of the test piece shall be measured to the nearest 0,1 mm by using micrometer callipers (4.4). If, for any reason, different test piece dimensions have to be used, they shall be stated in the test report. 5.2 Test piece preparation The surface shall be fnished by grinding with a wheel of grain size 20 µm or smaller. The contamination by wax, if any, should be removed by organic solution or by heating at 773 K (500 °C) for 1 h to evaporate wax. 6 Test method 6.1 Waveform of loading stress The waveform shall be sinusoidal and the ratio of minimum to maximum stress R = 0,1. The frequency shall be selected by agreement between parties, with 20 Hz being recommended. For other cases, the waveform of the loading stress shall be stated in the test report. A series of tests shall be carried out using the same stress waveform. 6.2 Loading method 6.2.1 The distances between internal support points and external support points shall be measured by a calliper before the tests. 6.2.2 The test piece shall be centrally positioned in the test fxture. 6.2.3 The number of cycles from the start of loading to the end of adjusting to a specifc cyclic loading stress shall be as few as possible. In this case, the stress during initial adjusting shall not exceed the specifc maximum stress. 6.2.4 The test shall, as a rule,...
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