Mechanical Crush Gauge and Method of Using Same to Measure Free-Field Energy Flux Density
Patent application, filed 30 Sep 97
DEPARTMENT OF THE NAVY WASHINGTON DC
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A mechanical crush gauge has a housing defining a fixed diameter hole that holds a sample of deformable material and an indentor having a flat end and a spherically-shaped end opposite the flat end. The indentor has its flat end flush with the surface of the housing and its spherically-shaped end in tangential contact with the sample. The indentor is made from a material having a yield strength orders of magnitude greater than that of the sample. Energy absorbed by the flat end is converted into kinetic energy that forces the spherically-shaped end against the sample to form a spherical dent therein indicative of energy flux density. In use, the diameter of the spherical dent is measured and converted to an energy value indicative of energy absorbed by the sample per unit area of the flat end of the indentor. The energy value is then calibrated by a correction factor that accounts for an acoustic impendance mismatch between the mechanical crush gauge and the medium of energy transmission in order to arrive at the free-field energy in the medium.