Measurement and modeling of strength distributions associated with grinding damage

Conference · Tue Aug 01 04:00:00 EDT 1995

OSTI ID:83229

Salem, J A; Nemeth, N N; Powers, L M ^[1]

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1. NASA, Cleveland, OH (United States); and others

The strength of ceramic material is typically measured in accordance with ASTM C1161 which specifies the machined specimens be ground uniaxially in the longitudinal direction and tested so that the maximum principal stress is longitudinal. Such a grinding process typically induces minimal damage in the transverse direction, but significant damage in the longitudinal direction, resulting in an anisotropic flaw distribution on the surface of the specimen. Additionally, investigations of the strength anisotropy due to grinding may provide a means to measure a materials strength response under mixed mode (I & II) conditions, thereby providing information that can be applied to isotropic cases (e.g. polished or as-processed material). The objective of this work was to measure and model the effects of a typical, uniaxial grinding process on the strength distribution of a ceramic material under various lading conditions. The fast-fracture strength of a sintered alpha silicon carbide was measured in four-point flexure with the principal stress oriented at angles between 0 and 90{degrees} relative to the grinding direction. Also, uniaxially ground plate specimens were loaded biaxial flexure. Finally, flexure specimens were tested in an annealed condition to determine if the machining damage could be healed. Modeling of the strength distributions was done with two and three parameter Weibull models and shear sensitive and insensitive models. Alpha silicon carbide was chosen because it exhibits a very low fracture toughness, no crack growth resistance, high elastic modulus and a very low susceptibility to slow crack growth (static fatigue). Such properties should make this an ideal ceramic for the verification of fast fracture reliability models and codes.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 83229
• Report Number(s): CONF-940416--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
99 GENERAL AND MISCELLANEOUS
CRACK PROPAGATION
FRACTURE PROPERTIES
GRINDING
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
SILICON CARBIDES