The ball-on-three balls (B3B) test is a new procedure for biaxial strength testing of brittle materials. A disc-shaped specimen is supported by three balls on one side and loaded by a fourth ball on the other side. This mechanically well-defined loading situation enables a quick biaxial strength test even for specimens that are not perfectly flat. Therefore, testing of as-sintered ceramic specimens is possible. In recent investigations of the authors the test has been performed on several ceramic materials, with strengths ranging from low (around 100 MPa) to high (more than 1000 MPa) values. The applicability of the test could be proven. As predicted by Weibull theory, the materials showed a pronounced size effect on strength. If this effect is taken into account, the B3B test results fit well to the ones determined by conventional bending tests.The load transfer via the balls into the specimens occurs in relatively small areas, which can be determined by an elastic Hertz analysis. It is well known that around the Hertzian contact zones tensile stresses exist, which may cause the occurrence of Hertzian ring cracks. In this paper the question is addressed if such cracks can be come into existence during B3B testing and if contact cracks - if they exist - have an influence on the determined strength values.
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