Scanning electron acoustic microscopy of indentation-induced cracks and residual stresses in ceramics

Abstract

The ability of scanning electron acoustic microscopy (SEAM) to characterize ceramic materials is assessed. SEAM images of Vickers indentations in SiC whisker-reinforced alumina clearly reveal not only the radial cracks, the length of which can be used to estimate the fracture toughness of the material, but also reveal strong contrast, interpreted as arising from the combined effects of lateral cracks and the residual stress field left in the SiC whisker-reinforced alumina by the indenter. The strong contrast is removed after the material is heat treated at 1000 °C to relieve the residual stresses around the indentations. A comparison of these observations with SEAM and reflected polarized light observations of Vickers indentations in soda-lime glass both before and after heat treatment confirms our interpretation of the strong contrast.

Theoretical and experimental investigation of the photoacoustic effect in solids with residual stresses

“…An important peculiarity of these images is the presence of regions with large signal amplitude located near the ends of the radial cracks. Previously, analogous features have been reported for the images of Vickers indentations obtained by electron-acoustic microscopy [2]. We have also observed this feature during the PA piezoelectric study of Al 2 O 3 -SiC-TiC ceramics [23,24].…”

“…Note that this result must be valid also for the electron-acoustic signal when special details of thermal wave generation by the electron beam are not important. This fact may explain the great similarity between the PA [3,4,6] and electron-acoustic [2], [11]- [13] images of areas near Vickers indentations.…”

“…The problem of residual and mechanical ¤ E-mail: klm@holo.io¬e.rssi.ru Unauthenticated Download Date | 5/11/18 3:26 PM stress detection in solids by the photoacoustic (PA) method has been investigated for about twelve years. The¯rst PA detection of residual stress was made in the papers [1,2]. Since then a number of similar applications of the PA e®ect [3]- [10] and electron-acoustic e®ect [11,12] has been performed.…”

Three-dimensional simulation of electron-acoustic detections

“…Since then, the applications of SEAM for characterizing the microstructures of materials and devices have been widely developed, such as doping regions in semiconductors, 3 magnetic domains in ferromagnetic and microwave materials, 4 ferroelectric domains in ferroelectric ceramics, 5 residual stresses in ceramics 6 and metals, 7 surface and subsurface structures in biological materials, [8][9][10] and so on. The advantages of SEAM are the special imaging abilities for local different thermal or elastic features of surface and subsurface structures with high resolution, by which laminated images of micro-inhomogeneous materials can be obtained nondestructively.…”

<title>Comparison of application of photoacoustics and thermoelastic stress analysis methods for detection of mechanical stresses</title>

“…The PA methods have micrometer resolution, are non-destructive and appeared to be useful for the detection of cracks and voids, delaminations and possible second phase material inclusions in the near surface layer of components. The first PA detection of residual stress took place about sixteen years ago [4]. Since then, there were a number of attempts for similar applications of the PA effect [5][6][7][8][9].…”