Some Physics Relevant to Acoustic (Shock Wave) Impedance Calculations.
Abstract
The problem of energy transmission across a boundary separating acoustically linear and nonlinear media is considered to third order in the strain (third order elastic constant). The study proceeds via the contribution of the first harmonic (the input signal being the fundamental) to the stress tensor. It is concluded that the nonlinearity introduces a correction of approximately a few percent (for most crystalline materials), at ten kilobars input amplitude, in comparison to the infinitesimal amplitude impedance matching relations. Special materials, such as potassium iodide (KI), are found to have a twenty-seven percent nonlinearity correction at ten kilobars. The problem of relaxation (both thermal and mechanical) contributions to the propagation velocity of a strain-driven thermal disturbance is considered. It is shown that the relaxation model employed plays a significant role in determining the magnitude of the propagation velocity as a function of time (as compared to the magnitude of the relaxation time). The relaxation mechanism considerations have possible bearing upon the existence of nonsteady-state shock effects as predicted by Tsai and co-workers. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1975
- Accession Number
- ADA021089
Entities
People
- Paul Harris
Organizations
- Picatinny Arsenal