The wear and fracture mechanisms of PCD cutters active during the core drilling of reinforced concrete have been documented. All have analogies with well known mechanisms from rotary and rotary-percussive rock drilling and also metal cutting (machining). At rotational velocities up to 5m/s and normal and cutting forces around 2000N per 5mm cutter (equating to principal stresses of around 500N/mm2 at the cutting edge), gross fracturing of relatively un-worn cutters early in drilling is the predominant failure mechanism. Chipping at various size scales is observed with approximately the same rate of occurrence as cutter wear, which is mainly caused by attrition abrasion in concrete and to a lesser extent by chemical (diffusive) wear in the reinforcement steel. Chipping occurs by brittle fracture (unstable crack growth) at the small- to mid-scale and by fatigue crack growth at the large scale.

High performance Brillouin spectroscopy (BS) has been used to study the elastic properties (static and dynamic) of the orientational glassy state of Na(CN)xCl1-x samples \(\)). The temperature behaviour of the elastic properties reveals a more complex scenario for the orientational glass transition than generally believed. The shear elastic constant shows the well-known c 44 (T) anomaly, indicated by a minimum, found in other cyanide mixed crystals. The results obtained for the hypersonic attenuation are in clear contradiction with the dynamic character of the c 44 (T)-minimum. The temperature behaviour of the longitudinal elastic constant c11 of very dilute \(\)Na(CN)xCl1-x samples shows two striking features: i) Similar to the anomalous temperature behaviour of c 44 (T), lowering the temperature c 11 (T) first decreases, goes through a minimum and then rises again. The minimum takes place at a temperature above the temperature, \(\), where c 44 (T) reaches its minimum value. ii) A kink-like anomaly of c 11 (T) is observed at lower temperatures. This second anomaly is similar to the classical one observed in canonical glasses at their glass transition temperature \(\).

High-resolution Brillouin spectroscopy has been used as a crucial experimental technique to investigate the nature of the thermal glass transition in an epoxy. In order to study the coupling between the alpha-relaxation process and the thermal glass transition around the quasi-static glass transition temperature T(g) we introduce the opto-acoustic dispersion function as a very sensitive measure of the alpha-relaxations and show that close to but above T(g) the related relaxation spectrum still contains components within the microwave frequency region which finally is truncated by the thermal glass transition.

We present a new top-loading vacuum insulated thermostat/cryostat for temperature-modulated differential scanning calorimetry (TMDSC) and DSC measurements covering an outstanding temperature range. TMDSC measurements are now possible down to 60 K. As a consequence of its construction features, contamination by moisture is completely eliminated. In particular, the important time domain technique can be applied without any time limit, thus allowing precise measurements even in the immediate vicinity of phase transitions. Experimental results are presented to show the performance of the modified TMDSC system.

Large monocrystalline domains of pentacosane (C25H52) have been prepared on nanostructured polytetrafluoroethylene films. The acoustic and thermal properties have been investigated around the various phase transitions of the crystalline state of pentacosane using high-performance Brillouin spectroscopy and modulated differential scanning calorimetry. In the crystalline orthorhombic phase the values of the elastic constants are c(22)=7 GPa, c(33)=35 GPa, c(44)=2 GPa. In the R-V orthorhombic rotator phase the elastic constants are c(22)=3.35 GPa, c(33)=3.67 GPa, c(44)< 0.05 GPa. The evidenced thermal and acoustic anomalies are discussed in the frame of the accompanying structural changes.

High performance Brillouin spectroscopy was used to investigate the temperature dependent behavior of the longitudinal acoustic mode, the refractive index, and the hypersonic longitudinal mode Grüneisen parameter around the quasi-static glass transition temperature Tg of Polyvinylacetate. In the glass transition zone the longitudinal mode Grüneisen Parameter γL shows an apparent anomaly with a step-like anomaly. Whereas the temperature position of this anomaly clearly depends on the thermal history of the sample, the amplitude ΔγL = γL(T>Tg)-γL(T

Highly crystalline and uniaxial-oriented polytetrafluoroethylene films, nanostructured in one dimension, were used to produce a fully crystalline, thermoreversible morphology in the ferroelectric copolymer poly[vinylidenefluoride-trifluoroethylene]. The resulting state is built up of regularly stacked lamellar crystals of about 100 nm thickness and lateral dimensions of about 6 mu m.

The temperature dependence of elastic properties in a common epoxy prepolymer was investigated using Brillouin scattering and ultrasonic pulse spectroscopy. In the GHz region, the Brillouin shift frequency curve showed a sharp kink at about 250 K, which was in good accordance with T g observed by DSC. The D 90R function calculated from the Brillouin shift frequency showed a clear dispersion at temperatures near 350 K, at which a broad peak of the Brillouin linewidth was observed. In the MHz region, ultrasonic wave attenuation also showed a peak near 285 K. Assuming that these changes result from the α relaxation in the glass transition region, the frequency-temperature behavior of the peaks was discussed in connection with the α relaxation in fully cured epoxy resin.

Modulated DSC was used to investigate the specific heat around ferroelectric phase transitions. This method has been extended to investigations of slow relaxations within the time domain. For this purpose a suitable cooling assembly is proposed working with liquid nitrogen as well as with liquid helium as a coolant.

Taking advantage of the surface-induced orientation of linear molecules on highly oriented nanostructured polytetrafluoroethylene, we were able to grow macroscopic single crystals of (pentacosane). Using high-performance Brillouin spectroscopy, we determined for the first time the complete elastic tensor of an n-alkane.

Time domain Brillouin spectroscopy has been used as a definitive experimental approach to demonstrate the intrinsic nature of the thermal glass transition in Polyvinylacetate. The transition from the equilibrium liquid to the ideal glassy state appears at the ultimate temperature T-gs.

Brillouin spectroscopy, dilatometry and calorimetry results have been used to investigate the temperature anomaly of the mode and thermal Grüneisen parameters around the glass transition of the fragile liquid poly(vinyl acetate). These results are compared with those of the strong liquids and 4-cyano-4-6-alkylbiphenyl.

Brillouin spectroscopy was used to investigate the temperature dependence of the longitudinal acoustic mode, the refractive index, the density and the hypersonic mode Gruneisen parameter around the glass transition of polyvinylacetate. In the glass-transition zone The mode Gruneisen parameter shows an apparent weak anomaly and an extrapolated weak discontinuity of about 60%. The temperature position of this apparent anomaly depends on the thermal history of the sample, whereas the strength of it does not.

The room temperature phase of the physical/chemical vapor-deposited statistical co-oligomer VDF/TrFE(70/30) has been characterized by different experimental methods such as small-angle x-ray scattering, wide-angle x-ray diffraction, size-exclusion chromatography, infrared absorption and optical refractometry. The characterization of the elastic properties was carried out using high-performance Brillouin spectroscopy in connection with special scattering geometries. The co-oligomer VDF/TrFE(70/30) was obtained by cracking the parent statistical copolymer and subsequently vapor depositing the shortened chains on highly oriented PTFE substrates (PIA-technique). The room temperature phase of the resulting oriented waxy crystal mats of VDF/TrFE(70/30) is predominantly ferroelectric. The physical properties are very different to those of similarly PIA-prepared n-alkanes, perfluoroalkanes, and blockfluoroalkanes. The microstructure of VDF/TrFE(70/30) is interpreted in terms of partially crystalline nano-sized structures giving rise to a marked freezing process below room temperature. (C) 1995 John Wiley and Sons, Inc.

The rotator phase of ${\mathrm{C}}_{24}$${\mathrm{F}}_{50}$ has been characterized in its calorimetric as well as in its elastic properties. To perform the elastic characterization we took advantage of a polytetrafluoroethylene-induced-alignment crystal-growth technique. Special interest is paid to the rotator phase and the premelting behavior therein as reflected by the elastic stiffness coefficients ${\mathit{c}}_{33}$ and ${\mathit{c}}_{44}$. The anomalous elastic behavior is interpreted in the frame of the Landau theory. The premelting process is related to molecular conformational defects.

Within this work we present Brillouin and ultrasonic investigations performed on the liquid crystals p-methoxybenzylidene p-(n-butylaniline) (MBBA), p-azoxyanisol (PAA), 4-cyano-4-n-alkylbiphenyles (nCB), and 4-n-pentoxybenzylidene-4'-n-octoaniline (5O.8). Special attention has been paid to the evolution of a significant splitting of the two longitudinal polarized acoustic modes within the nematic phase. Angle-resolving Brillouin spectroscopy allowed the determination of the complete stiffness tensors and hence a discussion of the propagation of quasitransverse polarized acoustic modes in the nematic state of liquid crystals. We analyze the behavior of the eigenvectors of the relevant acoustic modes and discuss their significance for the propagation of quasishear modes. For 5O.8 we report an acoustic instability within its nematic state. We confirm the existence of a universal thermal relaxation mechanism of weak activation energy for the nematic state of classical liquid crystals. The observed hypersonic anisotropy is discussed in terms of that relaxation mechanism and is compared with that of glass-forming liquid crystals.

Within this work we present comparative Brillouin and ultrasonic investigations of p-methoxybenzylidene p-(n-butylaniline), p-azoxyanisol, and 4-cyano-4'-pentyl-biphenyl performed in the vicinity of the nematic-isotropic transition. We confirm the existence of a universal hypersonic relaxation mechanism of weak activation energy and a related significant splitting of the two principal longitudinal acoustic modes within the nematic phase. Brillouin refractometry is proposed as a method to determine the magnitude of the nematic order parameter simultaneously with the second-order elastic stiffness constants. The origin of the hypersonic anisotropy is discussed in terms of thermal relaxations and the evolution of the nematic order parameter.

Frozen-in trans and gauche conformational disorder of symmetrical difluorotetrachloroethane (DFTCE) produces the tendency of this plastic crystal to form an orientational glassy state on cooling below T(g) = 86 K. To throw light upon the freezing mechanism in DFTCE neutron diffraction and Brillouin scattering as well as infrared and dielectric measurements are employed. The overall picture of the results obtained can be characterized in terms of a classical glass-transition process with a relaxation frequency obeying the Vogel-Fulcher law. However, a more sophisticated picture of the freezing process is indicated by a quantitative analysis of the new Brillouin data, e.g. the temperature dependence of the sound velocity. The behaviour could be understood on the basis of a mode-coupling theory.

The elastic and opto-acoustic properties of sodium cyanide crystals NaCN and sodium cyanide--sodium chloride mixed crystals Na(CN${)}_{\mathit{x}}$${\mathrm{Cl}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$ (1\ensuremath{\ge}x\ensuremath{\ge}0.63) were investigated below room temperature using high-resolution Brillouin spectroscopy. Employing special scattering techniques, we were able to measure the elastic behavior in both the high- and low-temperature phases. Changing from systems with high ${\mathrm{CN}}^{\mathrm{\ensuremath{-}}}$ concentrations, which undergo structural phase transitions of first order, to systems with low ${\mathrm{CN}}^{\mathrm{\ensuremath{-}}}$ concentrations, which show glass transitions, the discontinuities of the extremely soft shear stiffness of these cubic crystals gradually vanish. Using a space- and angular-resolving Brillouin technique, we report data on the inhomogeneity of the Czochralski-grown mixed crystals. The consequences of these inhomogeneities for the phase-transition behavior have been studied by thermal analyses. We try to describe our shear elastic stiffness data in the framework of current theoretical approaches.

High peformance Brillouin spectroscopy was applied to study the static and dynamic elastic behaviour of the mixed crystals Na(CN)xCl1−x around the critical concentration (xc%0.63), particularly as a function of temperature. By that means information is obtained about spatial concentration distributions, ferroelastic phases, glass-like phases and hypersonic dynamics.