ISO 21618:2019 pdf free

ISO 21618:2019 pdf free.Fine ceramics (advanced ceramics, advanced technical ceramics)
This document is for material development, material comparison, quality assurance, characterization and reliability data generation of dense monolithic ceramics. The method determines the indentation fracture resistance value, K,IFR, from the elastic modulus and indentation force by forcing a Vickers indenter (diamond pyramid) into the surface of a test piece and measuring the lengths of both the diagonals and the associated cracks of the indentation that are left in the surface after removal of the indenter (see Figure 1)[4]. The method is applicable to the half-penny-crack type but not to the Palmqvist type. The two types of crack profile can be estimated using the ratio of the crack length, 2c, to the diagonal length,2a. If 2c/2a is more than 2,5, the crack is half-penny type. But the critical 2c/2a values can be smaller than 2,5 for some ceramics. In such cases, direct observation of crack morphology by the decoration technique or serial sectioning of the indented surface is also useful to differentiate the two crack profiles.The measurement of the crack length and the observation of the crack tips are performed separately in order to improve the accuracy. The crack length should not be measured in a single optical image because doing so inevitably limits the magnification that can be used. Travelling microscopy is a solution that allows both reading of the crack length and detection of the crack tips to be performed at high resolution,albeit separately. Both an objective lens of 40 x or higher and a calibrated optical stage shall be employed to ensure reliability. Both international and domestic interlaboratory comparison study (round robin) projects on the advanced IF method are described in Annex C (see References [5] to [8]).
Specimens shall have a ground and polished surface so that the crack lengths can be measured accurately. The surface roughness, Ra, as defined in ISO 4287, shall be not more than 0,1 μm. Any grinding-induced damage layer at the surface shall be removed completely by polishing so that the crack lengths are not affected by any residual stress at the surface layer. The area fraction of tiny pits due to dropout of a grain or fragmentation shall be as small as possible to enable the precious crack-length measurement.
NOTE Annex A provides further information about a typical machining procedure.ISO 21618 pdf free download.