Plate-wave generation

The peak pressures attainable with explosive facilities can be greatly enhanced, and the initial peak pressure can be better sustained by using a plane-wave generator to accelerate a flyer plate, which then impacts a flat specimen as shown in Fig. 3.2. This technique will generate peak pressures up to a few hundred GPa. (McQueen and Marsh, 1960 McQueen et al., 1970). 

Figure 3.2. Explosive plane-wave generator used to accelerate a flyer plate for planar impact on a specimen.

The high explosives, baratol or Composition B-3, are used to produce the plane wave loading into the driver plates. These explosives have been widely studied in substantial work at Los Alamos. Plane waves are introduced into the explosive pads with either P-22 or P-40 plane-wave generators developed at Los Alamos. The Bear system is based on the 56 mm diameter of the P-22, while the larger sample size Bertha system is based on the 102 mmdiam of the P-40. More details on sample dimensions are reported by Graham [87G03]. 

By measuring the terminal velocity of a plate driven by a planar detonation one can, in principle, obtain y/2E for the driver expl by using Eqn (14). In practice, this approach is complicated by the necessity of using a plane wave generator to produce a planar detonation in the driver expl... 

Usually a plane wave generator (PWG) consists of several different expl components, some or all of which are likely to be different expls from the main driver charge. Obviously the PWG contributes energy to projecting the plate, and an estimate of its contribution must be made before one can determine y/2E for the main driver charge. The procedure adopted in Ref 14 for correcting for the presence of a PWG is as follows. Let and h be the respective thicknesses of the main driver charge and the metal plate and pc and pm their respective densities. 

This micro device for ultrasonic mixing was made from two plates, one of which has a shallow open volume to give a micro chamber after assembly (see Figure 1.31) [22], The area that actually covers the micro chamber is considerably thinned compared with the remaining thickness of the top plate. On this diaphragm, a thin PZT membrane is deposited, which acts as ultrasonic wave generator. The micro chamber is connected to two inlet channels and one outlet channel. 

In another approach, ultrasonic acoustic flexural plate waves (or Lamb waves) were used to generate fluid mixing motion of microspheres in water in a Si device. A 10-pm-thick piezoelectric ZnO film was deposited on the back side of a Si wafer (see Figure 3.48). This thickness is an odd-multiple of the acoustic half-... 

When the sound wave generated from the branched microcrack or reflected from the boundary of the plate interact with the crack, the singular stress fields at the tip of the crack are modulated in such form as given by Eqs. (25), which are proportional to cos((wr - P x). On the other hand the 1-st order fields consist of two terms which are proportional either to cos(o>r- p x) or sin(o>r-/5 jX). The latter term, for example, comes from the real part of such term. 

The system described here is based on the principles of ellipsometry (47). Figure 8 gives a block diagram of our experimental setup. The Psi-meter consists of a 2 mW helium-neon polarized laser source, a quarter wave retardation plate to generate circularly polarized light, a synchronously rotating polarizer to... 

Oblique ultrasonic waves sent to a composite at frequencies that excite plate wave modes induce the leaky lamb wave phenomenon. When the leaky Lamb wave is generated, the specular reflection is distorted. When the specular reflection and the leaky Lamb wave interfere, a phase cancellation occurs, and two components are generated with a phase between them. Because each type of defect has a unique response, this technique can be used to determine material eleastic constants and to estimate the volume content of resin as well as porosity content. Detection of transverse cracking and delamination in a 24-layer unidirectional graphite-epoxy laminate has also been reported [140], and oblique incidenee back-scattering techniques give accurate fiber orientation of the first composite layers [15],... 

We also need to analyze the case for the flexural-plate-wave flow in more detail and to simultaneously perform numerical simulations of the resultant flows. The results of the full numerical simulation may be used to prove that the steady flow components are generated by the mechanism known as the Stokes drift flow. 

Fig. 10.3 Generation of high dynamic pressures with chemical explosives (a) cylindrical scheme, (b) planar direct-contact scheme, (c) planar scheme with explosively accelerated impactor plate. 1 detonator, 2 explosive, 3 ampoule, 4 sample, 5 plane wave generator, 6 layer of inert material, 7 impactor plate...

Recent work by Lauterbom et al. [8] on high speed holography has produced pictures of the collapse of bubbles and the shock waves generated (see plates 1 and 2) by sonolysis of water. 

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