Optical interferometry technique

Compact tension tests on PMMA specimens give a value of 325 J m" for Gic at 23°C, for a crosshead speed of 5 mm min". The critical crack tip opening displacement 8, determined using an optical interferometry technique, is 4.2 m. Calculate the surface stress acting on the craze formed ahead of the crack tip. 

The duochromatic optical interferometry technique [19] was used to measure the shape and thickness of the lubricating film. A Xenon flash lamp with a flash... 

The effects of transversely oriented asperities passing through the EHL conjunction on micro-EHL films have been examined by direct observations using the optical interferometry technique. The main results obtained are as follows ... 

The advent of lasers allowed optical interferometry to become a useful and accurate technique to determine surface motion in shocked materials. The two most commonly used interferometric systems are the VISAR (Barker and Hollenbach, 1972) and the Fabry-Perot velocity interferometer (Johnson and Burgess, 1968 Durand et al., 1977). Both systems produce interference fringe shifts which are proportional to the Doppler shift of the laser light reflected from the moving specimen surface. Both can accommodate a speci-... 

With diblock copolymers, similar behavior is also observed. One component is enriched at the surface and depending on miscibility and composition a surface-induced ordered lamellar structure normal to the surface may be formed. Recent investigations include poly (urethanes) [111], poly(methoxy poly (ethyleneglycol) methacrylate)/PS [112] and PS/PMMA [113, 114]. In particular the last case has been extensively studied by various techniques including XPS, SIMS, NR and optical interferometry. PS is enriched at the surface depending on blockcopolymer composition and temperature. A well ordered lamellar structure normal to the surface is found under favourable conditions. Another example is shown in Fig. 6 where the enrichment of poly(paramethylstyrene), PMS(H), in a thin film of a di-... 

The cantilever bending-technique requires a sensitive displacement detection such as a capacitance probe (Klokholm 1976, 1977), optical interferometry (Sontag and Tam 1986), a tunnelling tip (Wandass et al. 1988) or angular detection (e.g. laser beam deflection, Son-tag and Tam 1986 Trippel 1977 Tam and Schroeder 1988 Betz 1997 Sander et al. 1998). 

A convenient technique for studying the crack tip craze propagation in amorphous polymers deals with optical interferometry. It has been applied to the examination of PMMA behaviour at various temperatures and crack speeds under conditions of stable propagation [44,45]. 

Piezoelectric Relaxation and Nonlinearity investigated by Optical Interferometry and Dynamic Press Technique... 

In summary, we can conclude that the optical interferometry can be a useful technique not only for routine piezoelectric measurements but that it can reveal crucial information on different mechanisms operating in the material. 

There are various surface techniques, eg., optical interferometry high frequency capacitance and resistance method, which demonstrate the build up of the physically and chemically reacted film during boundary lubrication in scuffing reactions (Anghel et al., 1997 Dowson et al., 1996 Smalley and Cameron, 1996). 

However, in an attempt to integrate the SFA and spectroscopic techniques, the use of silver for optical interferometry has been seen as a drawback due to the fact that it precluded sufficient excitation source intensity to illuminate the buried interface. In order to circumvent this problem Mukhopadhyay and co-workers in an experimental set-up where the SFA was combined with fluorescence correlation spectroscopy (FCS) used, instead of silver, multilayer dielectric coatings that allowed simultaneous interferometry and fluorescence measurements in different regions of the optical spectrum [75]. Using this set-up they succeeded in measuring diffusion in molecularly thin films with singlemolecule sensitivity. 

I. Optical interferometry, both heterodyne [12.13] and homodyne I4-I6 techniques. 

Crazing in anisotropic polymers has seldom been studied by means of optical interferometry. A block copolymer (Isoprene-Styrene) with a highly oriented fibrillar structure, and a PMMA oriented by means of drawing above Tg, have been studied so far. These results are reported in and The same subject has often been studied, however, using other experimental techniques... 

Like any experimental technique, optical interferometry suffers from limitations ... 

Ultrasonic interferometry, in which the travel time of high-frequency elastic waves through a sample is measured, also yields elastic moduli. Because it is a physical property measurement, rather than an optical spectroscopy, it can be used equally well on poly-crystalline samples as single-crystals, although polycrystalline measurements only yield the bulk elastic properties, bulk modulus and shear modulus, G. High-pressure ultrasonic interferometry techniques were initially developed in the piston cylinder... 

Tlie usual experimental techniques developed to study the optical Kerr effect in materials have already been described in a preceding chapter of this book. We only mention here the methods which have especially been used for nanocomposite materials as colloidal solutions or thin films Degenerate four-wave mixing (DFWM) and optical phase conjugation, which provide the modulus of x only and may be completed by Interferometry techniques to get its phase as well, optical limiting, optical Kerr shutter, and z-scan, which is probably the most common technique used in recent years due to its ability to provide simultaneously the nonlinear refraction and absorption coefficients of the same sample point [118],... 

The method which seems to be soundest and most free of empirical complications from the point of view of basic calibration is interferometry. The calibration is derived from fundamental optics. A technique for dealing with the effect of pressure on the refractive index of the fluid is available via the Lorenz equation. An implicit difficulty is the effect of temperature on the density of the fluid and thus on the evaluation of the Lorenz equation. The necessity of passing the light through a flat transparent plate to form the fringes imposes some limitations on the applicability of the method. 

Leisawitz et al. (2003) proposed an extension of the FOV by using a focal plane detector array for optical wavelengths, technique called Wide-Field Imaging Interferometry. However, direct detector arrays in the Far Infrared are still expensive and a similar approach is not straightforward. 

The above cantilever-bending technique requires a sensitive displacement detection [such as capacitance probe (Klokholm 1976, 1977), optical interferometry (Sontag and... 

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