Breviary Technical Ceramics



 4-Point Bending Test

The test jig consists of two supports, as in the 3-point bending test, with identical specifications. Two loading pins, whose centres are separated by half of the distance between the supports (see table 33), are positioned symmetrically to an accuracy of ± 0.2 mm between the sample supports, and the force is introduced perpendicularly to the test piece. Both loading pins must be able to rotate freely and independently around their axes and in a direction parallel to the long axes of the test piece. In this manner, the optimal alignment between the loading pins and the support pins can be achieved.

Figure 213: Schematic illustration of the 4-point bending test

The test piece must prepared to the dimensions given in Table 33 and shown in Figure 213, according to their group classification (DIN EN 60 672-2 and DIN EN 843-1). The test piece must be made using the process from which the product is expected to be manufactured (see pp. 70-76). Any surface treatment such as grinding, polishing, etc. should be noted and be representative of the surface of the product, since the fracture strength of ceramic can be affected by the surface quality. The minimum number of test pieces for each test is 10.

Table 33: Sample and test instrument dimensions


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