Indentation

About: Indentation is a research topic. Over the lifetime, 13002 publications have been published within this topic receiving 340476 citations.

Surface characterization of 6H-SiC (0001) substrates in indentation and abrasive machining

Abstract: Surface characterization of 6H-SiC (0001) substrates in indentation and abrasive machining was carried out to investigate microfracture, residual damage, and surface roughness associated with material removal and surface generation. Brittle versus plastic deformation was studied using Vickers indention and nano-indentation. To characterize the abrasive machining response, the 6H-SiC (0001) substrates were ground using diamond wheels with grit sizes of 25, 15 and 7 μm, and then polished with diamond suspensions of 3 and 0.05 μm. It is found that in indentation, there was a scale effect for brittle versus plastic deformation in 6H-SiC substrates. Also, in grinding, the scales of fracture and surface roughness of the substrates decreased with a decrease in diamond grit size. However, in polishing, a reduction in grit size of diamond suspensions gave no significant improvement in surface roughness. Furthermore, the results showed that fracture-free 6H-SiC (0001) surfaces were generated in polishing with the existence of the residual crystal defects, which were associated with the origin of defects in single crystal growth.

Creep of a TiAl alloy: a comparison of indentation and tensile testing

Abstract: The present study compares the indentation and uniaxial creep behaviour of a near-γ-TiAl alloy with a duplex microstructure. Indentation creep tests were performed using a cylindrical indenter at temperatures between 750 and 1050 °C and net section stresses between 50 and 1430 MPa. A stress dependent stress exponent ranging from 3 for low net section stresses to 8 for high net section stresses was determined. The apparent activation energy of indentation creep was determined as 343±16 kJ mol −1 . The stress as well as the temperature dependence of the indentation and uniaxial creep data are in good agreement. The indentation experiments were also analysed with respect to the deformed volume in front of the indenter and the surface bulge that develops around the indenter. A simple dislocation model is proposed to rationalize volume and shape of the bulge around the indenter. The good agreement of creep parameters obtained by indentation and conventional uniaxial creep testing demonstrates that indentation creep tests are suitable to characterize creep.

Laser damage precursors in fused silica

Abstract: There is a longstanding, and largely unexplained, correlation between the laser damage susceptibility of optical components and both the surface quality of the optics, and the presence of near surface fractures in an optic. In the present work, a combination of acid leaching, acid etching, and confocal time resolved photoluminescence (CTP) microscopy has been used to study laser damage initiation at indentation sites. The combination of localized polishing and variations in indentation loads allows one to isolate and characterize the laser damage susceptibility of densified, plastically flowed and fractured fused silica. The present results suggest that: 1) laser damage initiation and growth are strongly correlated with fracture surfaces, while densified and plastically flowed material is relatively benign, and 2) fracture events result in the formation of an electronically defect rich surface layer which promotes energy transfer from the optical beam to the glass matrix.