Propagating stress waves

The common civil engineering seismic testing techniques work on the principles of ultrasonic through transmission (UPV), transient stress wave propagation and reflection (Impact Echo), Ultrasonic Pulse Echo (UPE) and Spectral Analysis of Surface Waves (SASW). 

The objective in these gauges is to measure the time-resolved material (particle) velocity in a specimen subjected to shock loading. In many cases, especially at lower impact pressures, the impact shock is unstable and breaks up into two or more shocks, or partially or wholly degrades into a longer risetime stress wave as opposed to a single shock wave. Time-resolved particle velocity gauges are one means by which the actual profile of the propagating wave front can be accurately measured. 

The gauge element in the form of a foil (50 ohms) is normally embedded in materials such that the active gauge element is normal to the stress-wave propagation direction. Manganin is the only in situ stress gauge available for... 

Steady-propagating plastic waves [20]-[22] also give some useful information on the micromechanics of high-rate plastic deformation. Of particular interest is the universality of the dependence of total strain rate on peak longitudinal stress [21]. This can also be expressed in terms of a relationship between maximum shear stress and average plastic shear strain rate in the plastic wave... 

G.E. Duvall, Propagation of Plane Shock Waves in a Stress-Relaxing Medium, in Stress Waves in Anelastic Solids (edited by H. Kolsky and W. Prager), Springer-Verlag, Berlin, 1964, pp. 20-32. 

Herrman, W., Nonlinear Stress Waves in Metals, in Wave Propagation in Solids (edited by Miklowitz, J.), American Society of Mechanical Engineers, New York, 1969, pp. 129-183. 

Gurtman, G.A., Review of Techniques Used to Analyze Stress Wave Propagation in Composites, Systems, Science and Software Report No. 3SR-154, Part II, La Jolla, CA, 40 pp., December 1969. 

Seaman, L., SRIPUFF 3 Computer Code for Stress Wave Propagation, Air Force Weapons Laboratory Technical Report No. AFWL-TR-70-51, Kirtland AFB, NM, 370 pp., September 1970. 

Fig. 2.3. Experimental determination of shock-stress versus volume compression from propagating shock waves is accomplished by a series of experiments carried out at different loading pressures. In the figure, the solid lines connect individual pressure-volume points with the initial condition. These solid straight lines are Rayleigh lines. The dashed line indicates an extrapolation into an uninvestigated low pressure region. Such extrapolation is typical of much of the strong shock data.

The technique utilises arrays of transducers attached to the external surfaces of the equipment, which detect small-amplitude elastic stress waves emitted when defects propagate . Using sophisticated computational techniques, events can be characterised in terms of their severity and location. 

Davids, N. (ed.), International Symposium on Stress Wave Propagation in Materials, Interscience Publishers, New York,... 

The analysis of propagating acoustic waves in an elastic medium allows its characterization by means of strain-stress relationships. The stress ay is defined as the ratio of an external force F parallel to a direction i (x,y or z) to a surface S perpendicular to the direction j. 

A Computer Program SRATE for the Study of Sttain-Rate Sensitive Stress Wave Propagation , SandiaCorpRept SC-RR-65-298(1965)... 

When the intensity of the stress waves is reduced so that there is no permanent deformation of the rock, the stress wave propagates thru the rock in an elastic manner, that is, in such a manner that the rock particles are returned to their original position following the passage of the stress wave... 

When the energy accumulated in a stressed body is released, because of e.g. body destruction, the stress waves are generated. The waves propagating through the body create acoustic signals that arrive at the boundary surface where they can be monitored. The intensity of these signals and their energy may supply important information on destructive processes that occur inside the material. 

L. B. Freund, Crack Propagation in an Elastic Solid Subjected to General Loading IV-Stress Wave Loading, Journal of Mechanics and Physics of Solids, 21, 47-61 (1973). 

A new rheo-photoacoustic Fourier transform infrared cell has been developed to perform stress-strain studies on polymeric materials. The rheo-photoacoustic measurements lead to the enhancement of the photoacoustic signal and allow one to monitor the effect of elongational forces on the molecular structure of polymers. Propagating acoustic waves are detected as a result of infrared reabsorption and the deformational and thermal property changes upon the applied stress. 

Propagation Model. The propagation of a pressure or stress wave through a compressible medium is described by the laws of conservation of mass and momentum and the equation of state which relates the pressure or stress in the medium to the strain and its material properties (j ). 

KC Valanis, S Chang. Stress wave propagation in a finite viscoelastic thin rod with a constitutive law of the hereditary type. In TC Huang, MW Johnson, eds. Developments in Theoretical and Applied Mechanics. New York Wiley, 1965. 

As we have seen in the previous section, the density of the sample included on the right-hand side of the equation of motion gives, as a solution of the problem, the propagation of the stress wave through the sample. In the present context, this part of the phenomenon is of limited... 

The effective P may be determined with the electron beam apparatus. When the sample (slab geometry) is thick enough to absorb all of the incident electrons, a compressive stress wave propagates from the irradiated region into the sample bulk. A transducer, located just beyond the deposition depth, may be used to record the stress pulse. Alternatively, the displacement or velocity of the rear surface of sample may be observed optically and used to infer the initial pressure distribution from the experimentally measured stress history. Knowledge of the energy-deposition profile then permits the determination of the Gruneisen coefficient. 

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