Indentation Fracture Toughness

Bulk density of specimens was measured by the Archimedes principle. The Vickers hardness as well as indentation fracture toughness were determined at room temperature using a Vickers diamond indenter at a 10 kg load for 10 s. Microstructure observation was performed under a transmission electron microscope (TEM JEOL, Tokyo, Japan JEM-2010/200CX/21 OOF). Optical transmissions of the translucent samples in wavelength of 2.5-6.5pm were measured by FTIR spectrometer (EQU1NOX55, Bruker, Billerica, MA). 

A. Muchtar and L. C. Lim, Indentation fracture toughness of high purity submicron alumina, Acta Mater. 1998, 46, 1683-1690. 

TABLE 4. Grain size distributions for the Si3N4-BAS composite from different ratio of starting silicon nitride powders with their indentation fracture toughness and flexural strength... 

Until now, no details have been reported of indentation fracture toughness (K c-ICL) measurements on pure y-Si3N4. However, in the case of the spinel-sialon y-Si2A10N3, mean Kic-ICL values of 4.6MPam were reported at indentation loads of 0.5 and 1.0 kg [51]. 

In order to overcome many of the difficulties associated with the indentation fracture toughness measurement as noted above, the single-edged notched beam (SENB) test - which often is used for metallic and polymeric materials - has been adapted to suit ceramics [24]. For this, a bar of ceramic, usually in the order of 3 x 4 mm cross-section and 25-45 mm length, has a notch introduced on one side. The bar is then loaded in four-point bending and the fiacture toughness determined from the failure load, Pm> as per ... 

Tanaka, K., Elastic/Plastic Indentation Hardness and Indentation Fracture Toughness the Inclusion Core Model, J. Mater. Sci., 1987, 22, 1501. 

The glass density (d) was measured on powdered samples by the pycnometry method with an accuracy of 0.005 g cm Young s modulus ( ) and Poisson s ratio (y) were measured by the pulse-echo technique on 4 mm thick rectangular specimen. Vickers indentations (load of 9.8 N apphed during 15 s), were performed to estimate both Meyer s hardness (H) and the indentation fracture toughness (Kc) by means of the following equations ... 

A.S. Rizkalla and D. W. Jones. (2004) Indentation fracture toughness and dynamic elastic moduli for commercial feldspathic dental porcelain materials. Dent Mater. 20 198-206. 

Using the dimensions of radial craclcs, the apparent indentation fracture toughness Kc of a glass can be determined as proposed originally by Anstis et al. (1981). The relation between Kc and the half of the mean size of the two cracks c is given by (Figure 8.10)... 

Cie] observed Portevin-Le Chatelier Effect in biaxially strained Al-Fe-Si foils. This effect is attributed to the diffusion of Si rather than Fe, as the latter has much slower diffusivity and low solubiUty in (Al). [2003Mur] reported the hardness and indentation fracture toughness of T2 and T5 phases, both have hardness much higher than binary aluminides and they have very similar indentation fracture toughness. 

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