A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

https://material.karlov.mff.cuni.cz/people/janecek/studenti/FyzMetNano/Estrin_AM61_2013_782.pdf

Extreme grain refinement by severe plastic deformation: A wealth of challenging science

https://iopscience.iop.org/article/10.1016/0169-5983(93)90106-K/pdf

Phenomena of liquid drop impact on solid and liquid surfaces

Single-bubble sonoluminescence occurs when an acoustically trapped and periodically driven gas bubble collapses so strongly that the energy focusing at collapse leads to light emission. Detailed experiments have demonstrated the unique properties of this system: the spectrum of the emitted light tends to peak in the ultraviolet and depends strongly on the type of gas dissolved in the liquid; small amounts of trace noble gases or other impurities can dramatically change the amount of light emission, which is also affected by small changes in other operating parameters (mainly forcing pressure, dissolved gas concentration, and liquid temperature). This article reviews experimental and theoretical efforts to understand this phenomenon. The currently available information favors a description of sonoluminescence caused by adiabatic heating of the bubble at collapse, leading to partial ionization of the gas inside the bubble and to thermal emission such as bremsstrahlung. After a brief historical review, the authors survey the major areas of research: Section II describes the classical theory of bubble dynamics, as developed by Rayleigh, Plesset, Prosperetti, and others, while Sec. III describes research on the gas dynamics inside the bubble. Shock waves inside the bubble do not seem to play a prominent role in the process. Section IV discusses the hydrodynamic and chemical stability of the bubble. Stable single-bubble sonoluminescence requires that the bubble be shape stable and diffusively stable, and, together with an energy focusing condition, this fixes the parameter space where light emission occurs. Section V describes experiments and models addressing the origin of the light emission. The final section presents an overview of what is known, and outlines some directions for future research.

/pdf/single-bubble-sonoluminescence-samrz97qyy.pdf

Single bubble sonoluminescence

Wear models and predictive equations: their form and content

Review of experimental techniques for high rate deformation and shock studies

This paper describes the response of explosives to stress and impact and in particular the mechanisms of ‘ hot-spot production. Samples in the form of single crystals, powder layers, pressed pellets, gels, polymer bonded explosives (PBXS) and propellants have been studied. Techniques used include a drop-weight facility with transparent anvils which allows photography at microsecond framing intervals, an instrumented drop-weight machine, a miniaturized Hopkinson bar system for high strain rate property measurement, laser speckle for studying the deformation and fracture of PBXS, an automated system for analysing speckle patterns and heat sensitive film for recording the positions and temperatures of hot spots. Polishing and staining methods have been developed to observe the microstructure of PBXS and failure during quasi-static loading. Ignition, when it occurred, took place at local hot-spot sites. Evidence is discussed for a variety of ignition mechanisms including adiabatic shear of the explosive, adiabatic heating of trapped gases during cavity collapse, viscous flow, friction, fracture and shear of added particles and triboluminescent discharge.

Hot-spot ignition mechanisms for explosives and propellants

The high strain rate compressive behaviour of polycarbonate and polyvinylidene difluoride

Experiments are described in which steel spheres were projected obliquely onto mild steel targets. It is shown that this successfully simulates a class of impact occurring during the erosion of metals by dust and sand particles. The dependence of the crater dimensions on impact angle and velocity is determined and, using high speed photography, the energy balance in the impact process is studied. A model of crater formation is proposed which accurately predicts the volume of material displaced and the energy lost by an impacting sphere. It is found that metal becomes detached along a band of intense subsurface shear; calculation shows that this is associated with the production of local high temperatures. The data and analysis presented provide a basis for assessing the role of the ploughing component of deformation in erosion.

Solid particle erosion of metals: the removal of surface material by spherical projectiles

A two-dimensional method was used to observe the interactions of plane shock waves with single cavities. This allowed study of processes occurring within the cavity during collapse. Results were obtained from high-speed framing photography. A variety of collapse shock pressures were launched into thin liquid sheets either by firing a rectangular projectile or by using an explosive plane-wave generator. The range of these shock pressures was from 0.3 to 3.5 GPa. Cavities were found to collapse asymmetrically to produce a high-speed liquid jet which was of approximately constant velocity at low shock pressures. At high pressures, the jet was found to accelerate and crossed the cavity faster than the collapse-shock traversed the same distance in the liquid. In the final moments of collapse, high temperatures were concentrated in two lobes of trapped gas and light emission was observed from these regions. Other cavity shapes were studied and in the case of cavities with flat rear walls, multiple jets were observed to form during the collapse.

John E. Field

Papers

Review of experimental techniques for high rate deformation and shock studies

Hot-spot ignition mechanisms for explosives and propellants

The high strain rate compressive behaviour of polycarbonate and polyvinylidene difluoride

Solid particle erosion of metals: the removal of surface material by spherical projectiles

Shock-induced collapse of single cavities in liquids