WorldWideScience
 
 
1

Investigation of Al{sub 2}O{sub 3}- and SSiC-ceramic under lubricated, reciprocating sliding contact and cavitation erosion  

Energy Technology Data Exchange (ETDEWEB)

Tribological performance of alumina and silicon carbide ceramics as well as of the hardened steel 100Cr6 for reference was studied during reciprocating sliding and cavitation erosion in isooctane as substitute of gasoline and in distilled water. It was the aim to characterize effects of surface finish of the specimens and the liquid media on friction, resistance to sliding wear and cavitation erosion. Sliding wear tests were run on the self-mated ceramics and ceramic/steel pairs under conditions of boundary lubrication using a laboratory tribometer with cylinder-on-plate geometry. Vibratory cavitation erosion tests were conducted according to ASTM G 32-92. High initial surface roughness of coarse ground specimens led to a distinct running-in period during sliding contact with a transition from high to low values of friction coefficient and wear intensity. Incubation time was reduced with increasing surface roughness in the cavitation tests. Depending on the materials investigated, the ...

2005-03-01

2

Stress intensity factors of cracks in material compounds near boundary surfaces with mechanical and thermal loading; Spannungsintensitaetsfaktoren von Rissen in Stoffverbunden in der Naehe von Grenzflaechen bei mechanischer und thermischer Belastung  

Energy Technology Data Exchange (ETDEWEB)

A singular stress field can occur at the edge of the joint plane in a thermally or mechanically loaded material compound. This stress field was calculated analytically and was compared with the results from the finite element method. If one of the two partners consists of ceramic material, unstable crack spread starting from faults in this strongly stressed area can lead to failure. In linear elastic material, the behaviour of a crack is clearly described by the stress intensity factors. These can be calculated for a known stress distribution in the uncracked structure by the method of the weight function. The corresponding weight functions for surface cracks parallel to the boundary surface were determined with the aid of suitable reference load cases. The effect of the position of the crack in the compound and the elastic constants of the compound are discussed. For examples, the stress intensity factors for cracks in a thermally stressed material compound were determined by the ...

1995-03-01