An attempt to unify the Brinell, Janka and Monnin hardness of wood on the basis of Meyer law

Abstract

This work concerns basic research on the concept of wood hardness in a sense similar to Brinell or in the modified sense of Monnin. The experimental part of this article is based on research carried out on beech wood with six indenters: three ball indenters of 10, 15 and 30 mm and three cylindrical indenters of 10, 15 and 30 mm. On the basis of measurements for a wide range of loads, relations analogous to Meyer power law of were obtained, with the exponent determined both for balls equal to 5/2 and for cylinders equal to 3/2. These exponents turned out to be exactly the arithmetic mean of exponents for ideally elastic and ideally plastic bodies. On this basis, new hardness formulae were proposed, taking into account Meyer law and the diameters of indenters. Therefore, the proposed two hardness formulae (for the ball and cylinder) are a generalization and development of Meyer hardness law.