ISO 14705:2016 pdf free

ISO 14705:2016 pdf free.Fine ceramics (advanced ceramics, advanced technical ceramics)一Test method for hardness of monolithic
ceramics at room temperature
Vickers indentation diagonal lengths are approximately 2,8 times shorter than the long diagonal of Knoop indentations, and the indentation depth is approximately 1,5 times deeper than Knoop indentations made at the same force. Vickers indentations are influenced less by the specimen surface flatness, parallelism of the diamond axis to the test piece surface normal, and surface finish than Knoop indentations, but these parameters should be considered nonetheless. Vickers indentations are much more likely to cause cracks in fine ceramics than Knoop indentations. Conversion between hardness scales shall not be made.
Vickers indentations on metallic materials are mainly formed by the plastic deformation. However,Vickers indentations on fine ceramics are formed by micro-cracking and micro-fracture, besides plastic deformation. This difference shall be noted for comparing the hardness of metals and ceramics.The principal errors arising in a Vickers hardness test on advanced monolithic technical ceramics vary in magnitude according to the size of the indentation, and thus the indentation force used. The Vickers diamond geometry was originally chosen because natural cleavage planes of the diamond were employed. Variations in geometry between indenters are therefore small, and can usually be ignored except when indentations are of less than 20 μm diagonal length where the tip and edges near the tip may be variable between indenters. In particular, the edges may have flats up to 1 μm across on them, and this has the effect of cutting the corners off the indentation. The error that this introduces is insignificant if the indentation is larger than about 30 um, but increases rapidly in importance as the size is reduced.
Determination of the diagonal lengths using cross-wires or other device attached to the instrument relies on the operator positioning them at the “true” opposing corners of the indentation. There is a subjective element in performing this task which increases with poor optical contrast and reducing size of the indentation. The possible errors can be reduced by experience, and by consistent use of high-hardness, preferably ceramic or hardmetal, test blocks to familiarize the eye at the start of measurement sessions.ISO 14705 pdf free.