Shock velocity, measurement

These are some of the oldest, yet still the most useful gauges in shock-wave research. They contribute mainly to shock-velocity measurements. In some cases, these gauges alone can provide accurate Hugoniot equation-of-state... 

The different pressure measurement techniques alluded to in Kamlet s complaint may be grouped into particle velocity measurements, transmitted shock velocity measurements, pres-... 

As the Hugoniot data are known from previous investigators, the pressure in the Plexiglas can be calcd directly from the shock velocity measurements as shown on p 856 of paper... 

The pressure obtd from equation in dynes/cm was divided by 10 to express it in kbars. It varied for Comp B from 62 to 173 kbar. A single point at 388 kbar was obtd from shock-velocity measurements on a thin aluminum foil placed in contact with the explosive. This point corresponds to the von Neumann "spike pressure ... 

Refs 1) S.A. Savitt R.H. Stresau, "Recent Air Shock Velocity Measurements Near Small Charges of Highly Confined Explosives , USNOL Rept 2442(1952)... 

Feb 1951) (in Ital) Engl abstract in Applied Mechanics Reviews 4, 517 (Sept 1951) (Theory of shock waves and the 2nd law of thermodynamics) 18a) J. Savitt R.H.F. Stresau, "Recent Air Shock Velocity Measurements Near Small Charges of Highly Confined Explosives , USNOL-NavOrdRept 2442(1952) 18b) Taylor... 

Yadav, H.S., and Kamath, P.V. Shock velocity measurement in water by sulphur probes. Propellants, Explosives, Pyrotechnics 11, 150-154 (1986). 

Prompt instrumentation is usually intended to measure quantities while uniaxial strain conditions still prevail, i.e., before the arrival of any lateral edge effects. The quantities of interest are nearly always the shock velocity or stress wave velocity, the material (particle) velocity behind the shock or throughout the wave, and the pressure behind the shock or throughout the wave. Knowledge of any two of these quantities allows one to calculate the pressure-volume-energy path followed by the specimen material during the experimental event, i.e., it provides basic information about the material s equation of state (EOS). Time-resolved temperature measurements can further define the equation-of-state characteristics. 

In principle, there is no upper bound in measurements of particle velocity (or stress) using laser velocity interferometry. In practice, very high-pressure shock fronts can cause copious jetting of microparticles from the free surface (Asay et al., 1976), obscuring the surface from the laser beam. To alleviate this, optically transparent materials can be bonded to the specimen, and particle velocity measurements are then made at the specimen/window interface. This has the added advantage of simulating in situ particle velocity... 

Shock-compression science originated during and after World War II when experimental facilities for creating planar shock waves were developed, along with prompt instrumentation techniques enabling shock velocity and particle velocity measurements to be made. The main thrust of shock-compression science is to understand the physics and to measure the material properties which govern the outcome of shock-compression events. Experiments involving planar shock waves are the most useful in shock-compression science. 

The diagnostics applied to shock experiments can be characterized as either prompt or delayed. Prompt instrumentation measures shock velocity, particle velocity, stress history, or temperature during the initial few shock transits of the specimen, and leads to the basic equation of state information on the specimen material. Delayed instrumentation includes optical photography and flash X-rays of shock-compression events, as well as post-mortem examinations of shock-produced craters and soft-recovered debris material. 

Figure 4.10. Type of Hugoniot necessary to produee a two-wave shoek strueture and resulting wave profile. This type of Hugoniot will in general give a loeus as shown, with a flat region of eonstant shock velocity. Point 2 will not be observed with techniques that measure only the first arrival of the shock wave. (After McQueen et al. (1970).)...

Calculate the final shock state pressure and density from the measured shock velocity of 5.77 km/s in a sample of glass (initial density 2.204 g/cm ) which is mounted onto a driver plate of pure Cu. The Cu driver plate is impacted at 4.5 km/s by a Ta flyer plate. Use the impedance match methods. 

C) Dunkle s Syllabus (1960-1961), p 13a (Stein found the rifle-bullet sensitivity of expls to increase with increasing thickness of confinement. For equivalent thickness, the expls were more bullet-sensitive in steel than in A1 bombs. As a quantitative test of deton of the expl, measurements by means of piezoelectric shock-velocity gages showed promise. When there was no firm indication... 

The various shock-producing systems were calibrated by using free-surface velocity measurements of specimen plates and corresponding shock-wave velocities obtd from the known equations of state of the specimen plate materials. Accdg to Footnote 4 on p 1931 of Ref 15a, the free-surface velocity for a plane shock wave is almost twice the particle velocity"... 

The measured driver plate impact velocity or the shock velocity in the target plate, whose shock properties are known, defined the incident shock strength. An impedance match at the target plate-explosive interface using the measured overdriven deton velocity then defined the corresponding detonation pressure and particle velocity... 

The properties of reflected waves in the deton products were detd by a similar impedance match at the explosive-backing plate interface using the measured transmitted shock velocity in the backing plate whose Hugoniot curve was known. This technique was described by Al tschuler et al (Addnl Ref Fj) for detg the shock properties of inert solids... 

Detailed description of "calibration procedure is given on pp 4-26. Fig 2A, p 6 (not reproduced here) illustrates the "Test Set-Up for Obtaining the Shock Velocity with a Smear Camera and Fig 3A, p 8 "Smear-Camera Set-Up for Measuring Free-Surface Velocity , "Summary and Conclusions are given on pp 24-6 and Refs on pp 27-8 of the report... 

In Appendix B is described on p 45, the "Measurement of Shock Velocity" on p 46 is given "Shock Velocity as a Function of Distance", when the shock has travelled in PMMA for SSGT (Table Bl) on p 47, Fig B, a curve representing "Shock Velocity vs Distance in PMMA for the SSGT and on p 48 is a curve showing "PMMA Hugoniot Data Obtained in Calibration of SSGT"]... 

H. Knight R. Duff, PhysRev 94, 784 ff (1954) (Precision measurement of deton and strong shock velocity in gases)... 

Boyle et al (Ref 5, p 855) stated that direct measurements of particle velocity, density and pressure are not feasible at present and the indirect methods must be used. They describe a method using determination of the shock velocities in an explosive (such as Comp B) and in a Plexiglas plate placed in contact with the explosive [See under Detonation (and Explosion), Pressure of ]... 

For more detailed description of particle-velocity measurements, see "Detonation, Particle Velocity in and Its Determination Andreev Belyaev (Ref 44, pp 247-49) describe a method of experimental determination of pressure of detonation, using the arrangement shown in Fig B, Here 1 is charge of an explosive enclosed in a metallic container, and 2 is a metallic (usually aluminum) plate, 1-2mm thick, firmly inserted as a cover at the end of cartridge opposite detonator, 3. On initiation of charge, a shock wave will spread to plate 2 and, when the wave reaches the outer surface of the plate, it will start to move with initial velocity VH (here H is nachaT-naya, which means initial). After determining this velocity experimentally, the... 

The transmitted wave has a shock velocity Dm and a particle velocity Wm related thru conservation laws to velocity D and particle velocity W in the explosive. Upon reaching the free surface of the metal the shock is reflected as a rarefaction wave and the free surface acquires a velocity Vj of approx twice Wm. Hence, the measurement of Vj and gives a means of determining Wffl and pressure of shock p thru the equations ... 

The essential advantage of shock tubes over electric discharge devices is the capability of producing a homogeneous gas sample (HGS) with enthalpy and pressure which can be dependably calculated from the measured shock velocity and the conservation laws. 

Reversal-temperature measurements of the Na and Cr lines in simple molecular gases, shock-heated to 2000-3000°K and to 0,2-2 atmospheres agree excellently with temperatures calculated from the measured shock velocity. Thus in these cases, collision processes are rapid enough to maintain effective equilibrium between ground and excited state populations despite radiatio n losses. In some shock tube work, however, the reversal temperature is initially above the equilibrium value, probably owing to delay in dissociation of the molecules, so that the temperature in translation and in internal degrees of freedom of the molecules is initially too high... 

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