Recently, a new method for residual stress measurement in thin films by using the focused ion beam (FIB) has been proposed by the authors. It is based on the combined capability of the FIB imaging system and of high-resolution strain mapping software (VIC-2D). A simple equation based on two-dimensional elasticity is used to evaluate the residual stress from the displacements due to introducing a slot. The slot length is assumed to be much larger than the slot width or depth. And the effect of the slot width was neglected. However, it is often hard, depending on film materials, to introduce a narrow and deep slot by FIB. In this work some practical issues regarding the slot geometry are addressed. Through two- and three-dimensional finite element analyses, it is explored how the slot length, width and measurement location affect the displacements which are the basic data for residual stress evaluation. As a result, the validity and limit of the equations based on two-dimensional elasticity are evaluated. Also, the effect of material dissimilarity between film and substrate is explored. Finally, examples for a diamond-like carbon film on glass substrate and an aluminum oxide film thermally grown upon an alloy are presented.
This paper addresses the creep behaviour of a woven SiCf–SiBC composite, tested in tension under a partial pressure of argon, between 1273 K and 1473 K. It appears that the creep strain begins from 1273 K and becomes larger at higher temperatures. Moreover, the shapes of the creep curves led to the assumption of the existence of two competing deformation mechanisms depending on the temperature domain. The creep mechanism involved is microcrack damage‐creep. From higher resolution studies at higher scales (scanning electron microscopy, transmission electron microscopy (TEM) and high resolution electron microscopy (HREM)), many types of damage were observed, for example matrix microcracking, fibre/matrix debonding and fibre/matrix sliding. The observations via TEM and HREM enabled us to specify the existence or not of the classical creep mechanism of the constituents of the composite, and also to characterize the behaviour and the role of the different interfaces and especially of the pyrocarbon interphase. These multiscale observations will be discussed in order to highlight the creep‐damage mechanism as a function of temperature of the SiCf‐SiBC composites.
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