We have used pulse time-of-flight techniques to examine the phonon emission from an optically excited GaAs/AlAs superlattice structure. For laser excitation wavelengths shorter than 767 nm ~the energy of E1HH1 transition!, we detect a significant longitudinal acoustic phonon component directed in a narrow beam normal to the structure. Under identical excitation conditions, generation of coheren...

Radiation from relativistic runaway electrons is considered as a source for plasma frequency radiation in tokamaks. Two specific emission mechanisms, Cerenkov emission, and radiation produced by nonlinear coupling of plasma and acoustic waves, are studied. In many cases the Cerenkov emission provides a reasonable spectral fit. It can also be used to measure the runaway current, and to est'imate...

Introduction Transverse matrix cracking in cross-ply gr/ep laminates was studied with advanced acoustic emission (AE) techniques. The primary goal of this research was to measure the load required to initiate the first transverse matrix crack in cross-ply laminates of different thicknesses. Other methods had been previously used for these measurements including penetrant enhanced radiography, o...

Acoustic Emission (AE) Technique is a unique Non Destructive Testing method being used as a global online monitoring tool for detection, location and characterization of various kinds of active defects. This paper illustrates the attempt to find the AE response of Ti6Al4V Alloy in different heat treatment conditions during tensile testing. Ti6Al4V alloy is tested in mill annealed, beta annealed...

Non-Destructive Testing & Evaluation methods are developed to inspect and investigate materials and structures. Ultrasonic Testing is an NDT method can be used for measuring the thickness of objects, as one of its significant applications. The objective of this paper is designing and applying an intelligent UT fuzzy control system for evaluating the thickness of thin metal objects in a range of...

The physics of ultrasonic acoustic emissions ( A E s ) was investigated for AE transmission through w o o d and transducers. The physical properties measured were velocity, attenuation and frequeney composition ol" AEs produced by two sources: cavitation events in xylem and peticil lead breaks. T h e authors also measured the relative sensitivity of var ious combinations of ultrasound transduce...

BACKGROUND This study investigates CAD/CAM ceramic cusp-replacing restoration resistance with and without buccal cusp replacement under static and dynamic cyclic loads, monitored using the acoustic emission (AE) technique. METHOD The cavity was designed in a typical MODP (mesial-occlusal-distal-palatal) restoration failure shape when the palatal cusp has been lost. Two ceramic restorations [w...

The John F. KennedyMemorial Bridge, a large cantilever through truss opened in 1963, carries Interstate 65 across the Ohio River between Louisville, Kentucky and Jeffersonville, Indiana. According to a 2003 count, the bridge carries over 120,000 vehicles per day [1]. Inspections revealed a five-inch full-depth transverse crack in the horizontal web in a tension region of the top chord on the ea...

Wear tests were carried out on different DLC coatings under lubricated and dry slip-rolling friction in a Twin-Disc Testing rig. The analysis of Acoustic Emission (AE) provided an easy and comfortable tool for monitoring the wear life of DLC coatings. A DLC coating in-service was indicated by the appearance of no or just single AE events due to single damages (crack, small spallings, etc.) to t...

Prompted by intriguing events observed in certain particle-physics searches for rare events, we study light and acoustic emission simultaneously in some inorganic scintillators subject to mechanical stress. We observe mechanoluminescence in Bi4Ge3O12, CdWO4, and ZnWO4, in various mechanical configurations at room temperature and ambient pressure. We analyze the temporal and amplitude correlatio...