Evaluation by Vickers indentation of fracture toughness of a phosphate biodegradable glass

Indentation tests are commonly used for the evaluation of fracture toughnes s of brittle materials, particularly glasses and ceramics, because this tec hnique requires only a small polished area on the specimen surface from whi ch a large number of data points can be generated rapidly. However, a wide variety of equations for the calculation of fracture toughness of ceramic m aterials by means of Vickers indentation are available. Such equations are obtained phenomenologically and their parameters adjusted in such a way tha t the K-IC values obtained are in good agreement with those obtained by con ventional methods. This is the reason why it is necessary to check which ty pe of equation reproduces more accurately the results obtained by means of conventional methods for the material which is going to be investigated. In the present work seven different fracture toughness equations widely used in glass and ceramic studies are considered and the results are compared wi th those obtained by conventional methods, such as single-edge notch beam ( SENB) specimens tested in three-point bending. The role played by the appli ed indentation load is considered. (C) 1999 Kluwer Academic Publishers.