Green strength testing of pressed compacts: An analysis of the different methods

This paper presents a comparative study of three- and four-point bending tests and diametral compression (DC) tests, used to measure the mechanical strength of green pressed compacts. The study has been conducted on pressed ceramic test pieces, formed at different pressing conditions. It was found that Weibull statistics largely explained the differences in the results of the three-point and four-point bending tests. However, Weibull statistics could not explain the much lower mechanical strength obtained with the diametral compression tests. The study establishes a correlation between the bending and DC tests; however, this correlation depends on moisture content, which is directly related to the plasticity of the piece. This finding confirms that the types of mechanical tests studied do not have the same sensitivity to the factors that lead to fracture. The differences in mechanical strength between the bending and DC tests were explained using a suitable fracture criterion (based on maximum strain) and plastic deformation.