Abstract: Acoustic emission apparatus methods for detecting termite infestation including a probe and signal processing circuitry. The probe includes an piezoelectric transducer and is adapted to be inserted into a bore-hole of the wood under test. The waveguide intersects the high frequency extensional and shear waves produced by feeding and movement of termite propagating along the grain of the wood. The transducer output signal is filtered through high (HF) and low (LF) bandbase filters. Selected HF/LF values produce a signal which substantially eliminates extraneous Out-Of-Plane acoustic noise. One embodiment includes a multiple channel multiplexing system for monitoring insect treatment processes in structures such as homes and other buildings. The real time data is used to determine the effectiveness of treatments as well as the time required to produce an effective treatment for termite eradication.

Abstract: Acoustic emission apparatus methods for detecting termite infestation including a probe and signal processing circuitry. The probe includes an piezoelectric transducer and is adapted to be inserted into a bore-hole of the wood under test. The waveguide intersects the high frequency extensional and shear waves produced by feeding and movement of termite propagating along the grain of the wood.

Abstract: A method for measuring surface roughness during formation of the surface due to grinding, polishing, and machining operations is described. It is also shown that the same technique can be used to measure the surface roughness after it has been formed. The measurement is accomplished by acoustically coupling a broadband piezoelectric transducer to the surface of the plate being measured by the use of petroleum jelly or other liquids that will eliminate an air interface between the surface to be measured and the transducer. Stress waves are generated in the plate by grinding or polishing operations. These same types of waves are generated by moving an object over a given surface (for example the human finger). Signals received by the transducer are split into two frequency ranges. One part of the signal is hi-pass filtered above 100 KHz, the other part of the signal is band-pass filtered between 20-60 Khz.

Abstract: A method for measuring surface roughness during formation of the surface due to grinding, polishing, and machining operations is described. It is also shown that the same technique can be used to measure the surface roughness after it has been formed. The measurement is accomplished by acoustically coupling a broadband piezoelectric transducer to the surface of the plate being measured by the use of petroleum jelly or other liquids that will eliminate an air interface between the surface to be measured and the transducer. Stress waves are generated in the plate by grinding or polishing operations. These same types of waves are generated by moving an object over a given surface (for example the human finger). Signals received by the transducer are split into two frequency ranges. One part of the signal is hi-pass filtered above 100 KHz, the other part of the signal is band-pass filtered between 20-60 Khz.

Abstract: A method and an apparatus for detecting and measuring cracks in plate-like structures using acoustic emission technique are disclosed. A false aperture transducer is designed to provide a criterion for filtering out extraneous noise in the acoustic emission signal based on modal analysis by computing the ratio of the high-frequency peak amplitude to low-frequency peak amplitude of the signal. A calibration curve correlating crack depth to the amplitude ratio can be obtained by simulating crack growth in a fracture specimen coupled to a test structure or field structure, and measuring acoustic emission signal in the structure by the false aperture transducer. The calibration curve correlates simulated crack depth percentage with computed peak amplitude ratio of the measured signal.

Abstract: A method and an apparatus for detecting and measuring cracks in plate-like structures using acoustic emission technique are disclosed. A false aperture transducer is designed to provide a criterion for filtering out extraneous noise in the acoustic emission signal based on modal analysis by computing the ratio of the high-frequency peak amplitude to low-frequency peak amplitude of the signal. A calibration curve correlating crack depth to the amplitude ratio can be obtained by simulating crack growth in a fracture specimen coupled to a test structure or field structure, and measuring acoustic emission signal in the structure by the false aperture transducer. The calibration curve correlates simulated crack depth percentage with computed peak amplitude ratio of the measured signal.

Abstract: A method and an apparatus for detecting and measuring cracks in plate-like structures using acoustic emission technique are disclosed. A false aperture transducer is designed to provide a criterion for filtering out extraneous noise in the acoustic emission signal based on modal analysis by computing the ratio of the high-frequency peak amplitude to low-frequency peak amplitude of the signal. A calibration curve correlating crack depth to the amplitude ratio can be obtained by simulating crack growth in a fracture specimen coupled to a test structure or field structure, and measuring acoustic emission signal in the structure by the false aperture transducer. The calibration curve correlates simulated crack depth percentage with computed peak amplitude ratio of the measured signal.

Abstract: An apparatus for detecting and measuring cracks in plate-like Structures using acoustic emission technique is disclosed. A transducer coupled with the structure is equally sensitive to in-plane and out-of-plane acoustic emission signals. A splitter receives the output signal of the transducer and divides the acoustic emission signal into a high-frequency signal and a low-frequency signal. A circuit generates a high-frequency peak amplitude and a low-frequency amplitude from there high-frequency and low-frequency signals. A computer computes the ratio of the high-frequency peak amplitude to the low-frequency peak amplitude.

Abstract: A method and an apparatus for detecting and measuring cracks in plate-like structures using acoustic emission technique are disclosed. A false aperture transducer is designed to provide a criterion for filtering out extraneous noise in the acoustic emission signal based on modal analysis by computing the ratio of the high-frequency peak amplitude to low-frequency peak amplitude of the signal. A calibration curve correlating crack depth to the amplitude ratio can be obtained by simulating crack growth in a fracture specimen coupled to a test structure or field structure, and measuring acoustic emission signal in the structure by the false aperture transducer. The calibration curve correlates simulated crack depth percentage with computed peak amplitude ratio of the measured signal.

Abstract: An apparatus for detecting and measuring cracks in plate-like structures using acoustic emission technique is disclosed. A false aperture transducer is formed by bonding a mass-loading component to and partially covering a small circular portion of the center surface of a larger aperture piezoelectric disk. In this manner, only a small part of the piezoelectric material in the center of the disk is mass-loaded and very sensitive to low frequency flexure waves created by out-of-plane sources while the remainder of the disk is unloaded and sensitive to high frequency extensional and shear waves created by in-plane sources.

Abstract: The invention simulates acoustic emission signals produced by crack growth within a structure so that listening equipment may properly be calibrated to listen for acoustic emission signals from actual structural crack growth. The invention has several embodiments which generate acoustic emission signals from a crack growing in a specimen such that the acoustic emission signals have a broad bandwidth as the crack grows. The acoustic emission signals produced by the growing crack can be introduced into a structure being monitored through a cone-shaped portion which is bonded to the structure being monitored.