A model for measuring the maximum shear strength of polycrystalline materials has been developed and the soft impressor technique extended and used to study the effect of temperature on the flow stress of SYNDAX3. The soft impressor technique was first described by Brookes and Green in 1973 where they employed copper cones to deform (001) surfaces of single crystal magnesium oxide. The use of an etch pit technique revealed that a blunted copper cone produced a dislocated volume in the bulk of the magnesium oxide, demonstrating that harder surfaces can be plastically deformed by significantly softer materials under conditions of single point contact. This paper will give an account of the salient features of that process of deformation when applied to single crystal magnesium oxide and single crystal diamond and propose a method for the evaluation of the effect of temperature on the initial flow stress of SYNDAX3, a polycrystalline diamond material consisting of primary diamond particles (about 2-10 μm in diameter in the finished product) dispersed in a silicon carbide matrix.
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