Ball-on-three-balls test

The ball-on-three-balls test (B3B test) is a mechanical testing method for determining the biaxial strength of brittle materials. It involves placing a disc- or plate-shaped specimen on three supporting balls arranged in an equilateral triangle and applying a compressive force to the centre of the opposite face using a fourth ball. This setup produces a biaxial stress field that more closely simulates real-world multiaxial loading conditions compared to uniaxial tests, and it allows for testing of as-sintered or unpolished surfaces.

It is designed to simulate multiaxial stress conditions, offering a more application-relevant measure of strength than traditional uniaxial tests. Compared to conventional three- or four-point flexural tests, the B3B test offers several advantages, including reduced sensitivity to geometrical inaccuracies, minimal influence from edge defects, and low friction effects. These characteristics make it particularly suitable for testing small-sized specimens.^[2] Variations of the test were made, including the B3B-${\displaystyle K_{\text{Ic}}}$ test and the three-balls-on-three-balls (3-on-3) test. They are particularly used in ceramic engineering, electroceramics and dental materials.