System and method to provide material property measurement using re-entrant ultrasound

A method of measuring variations in material properties in a specimen, comprising the steps of:

• A) transmitting an acoustic signal to establish an acoustic wave on a surface of the specimen over a material volume of length L;
• B) receiving the acoustic signal at the end of the length L;
• C) amplifying the acoustic signal received in step B);
• and
• D) repeating steps A) through C) N times, where N is greater than 1, with the acoustic signal amplified in step C) to establish an oscillating acoustic circuit including as a component thereof the material volume of length L;
• E) repeating steps A) through D) at different locations on the specimen;
• and
• F) mapping material property variations at the different locations on the specimen.

A method of measuring variations in material properties in a specimen, comprising the steps of:

• A) transmitting an acoustic signal to establish an acoustic wave on a surface of the specimen over a material volume of length L;
• B) receiving the acoustic signal at the end of the length L;
• C) amplifying the acoustic signal received in step B);
• and
• D) repeating steps A) through C) N times, where N is greater than 1, with the acoustic signal amplified in step C) to establish an oscillating acoustic circuit including as a component thereof the material volume of length L;
• and
• wherein the length L is approximately one wavelength of the acoustic signal in extent.

A method of recovering stamped and engraved serial number information from a specimen that has had the serial number information removed therefrom by machining, comprising the steps of:

• A) positioning a pair of ultrasonic transducers at a location over the specimen from which the serial number information has been removed;
• B) transmitting an acoustic signal from one of the ultrasonic transducers to establish an acoustic wave on a surface of the specimen;
• C) receiving the acoustic signal by the other of the ultrasonic transducers;
• D) re-transmitting the acoustic signal received by the other of the ultrasonic transducers to establish an oscillating circuit, the oscillating circuit including as a component thereof the specimen;
• E) monitoring the acoustic signal at a time exceeding the transit time of the acoustic signal from one transducer to the other transducer to determine a material property at the location;
• F) moving the pair of ultrasonic transducers to a different location of the specimen;
• G) repeating steps B) through F) to establish a mapping of material properties at the different locations of the specimen from which the serial number information has been removed.

An electro-acoustic oscillator for providing high-sensitivity acoustic property measurements with high spatial resolution within a small material volume of a specimen at various locations of the specimen, comprising:

• a pair of transducers positioned in relation to one another such that an acoustic signal transmitted by one transducer and establishing a surface acoustic wave in the small material volume of the specimen is received by the other transducer, the pair of transducers being movable in relation to the specimen;
• an amplifier having an input coupled to an output of the transducer that is positioned to receive the acoustic signal, and an output coupled to an input of the transducer that is positioned to transmit the acoustic signal;
• and
• acoustic signal monitoring equipment coupled between the pair of transducers, the acoustic signal monitoring equipment operable to monitor the acoustic signal for a period longer than a transit time of the acoustic signal through the specimen;
• and
• wherein the pair of transducers and the amplifier are operable to establish an oscillating acoustic circuit having as a component thereof the specimen, the one transducer re-transmitting the acoustic signal received by the other transducer N times, wherein N is greater than 1.