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Apr 1991

Volume 89, Issue 4B, pp. 1851-2015

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back to top Session 6ED: Education in Acoustics: Undergraduate Projects in Acoustics (Poster Session)
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Diagnostic study of vibrational signals from a drill press (A)

P. C. Marks, S. H. Angermund, V. Arya, S. D. Patel, M. G. Prasad, and C. Chassapis

J. Acoust. Soc. Am. Volume 89, Issue 4B, pp. 1945-1945 (1991); (1 page)

Online Publication Date: 14 Aug 2005

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The objective of this study was to measure the vibration of a drill press in order to detect the onset of chatter and to evaluate the use of vibrational measurements in a control system design. Chatter is unwanted vibration caused by the interference of the flank face of the bit with the bottom of the drilled hole which can be brought upon either by excessive feedrate or excessive drilling speed. Chatter is a major source of tool wear, which serves to increase machine downtime, thereby reducing productivity. Data were acquired in order to determine the baseline amplitude at which chatter occurs. Measurements were taken at feedrates varying from 9.4 mm/min, to 94.7 mm/min and with varying drill bit diameters. Chatter was seen to occur at feedrates over 65.8 mm/min for a worn bit and at over 94.7 mm/min for a new bit with an aluminum workpiece in a frequency range between 1400 and 2000 Hz. In a wood workpiece, no chatter was observed throughout the entire range of feedrates. This study would be useful in the development of a feedback control system which would provide for drilling at the optimum feedrate for a given work piece based on chatter detection.
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Prototype and feasibility study of a PVDF infant health monitor (A)

Joe Higgins and E. Carr Everbach

J. Acoust. Soc. Am. Volume 89, Issue 4B, pp. 1945-1945 (1991); (1 page)

Online Publication Date: 14 Aug 2005

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Piezoelectric polymer sheets, placed on the floor of a crib, can produce an output voltage that provides information about the heart and breathing rates of an infant in the crib. Such a device could be useful in detecting Sudden Infant Death Syndrome or other infant health problems. A prototype device has been developed with conditioning and detection electronics to isolate the contributions of each signal, and a feasibility study was developed to indicate whether such a device could be made cheaply and reliably enough to be commercially available to a wide population of consumers.
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Wave propagation in solids: Computation versus experiment (A)

Ali Usman and E. Carr Everbach

J. Acoust. Soc. Am. Volume 89, Issue 4B, pp. 1946-1946 (1991); (1 page)

Online Publication Date: 14 Aug 2005

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Via two complementary methods, compressive and shear wave propagation in solids possessing complex geometries have been investigated. First, the finite‐element package ANSYS was adapted to determine the stress field as a function of time due to a known excitation in solids with specified material properties. Then solids were constructed with the same properties and the strain field was measured as a function of time using fast strain gauges and laser interferometry. The results of these computational and experimental determinations will be compared.
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A computer controlled apparatus for measuring the angular scattering of ultrasound from a random medium (A)

David R. Leroux and Murray S. Korman

J. Acoust. Soc. Am. Volume 89, Issue 4B, pp. 1946-1946 (1991); (1 page)

Online Publication Date: 14 Aug 2005

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Measurements of the scattered sound intensity, I(θ), versus angle θ from submerged targets (such as a bubble cloud) require long tedious data runs. The task of generating a family of intensity curves (allowing for the adjustable parameters of a target) becomes insurmountable. An Apple IIe computer with an IEEE‐488 instrument bus is programmed to control a digital oscilloscope (for data acquisition) and a stepper motor rotational unit (for angular positioning of the transmitting transducer). Typically, an average of 32 trials is used to measure the incoherent scattered energy from the received pulses at any particular angle. Scattering results from a cylindrical air bubble column are presented along with some theoretical predictions. [Work supported by the Naval Acad. Res. Council.]
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Scattering of sound by bubble clouds (A)

Karin M. Hogan, Katherine L. Banta, and Murray S. Korman

J. Acoust. Soc. Am. Volume 89, Issue 4B, pp. 1946-1946 (1991); (1 page)

Online Publication Date: 14 Aug 2005

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Experimental results are shown for the scattering of ultrasonic pulses by a small volume of air bubbles in water. Two different types of bubblemakers are used to generate the bubble clouds. The first one uses an array of short wires spaced uniformly over a horizontal square area. A transient electronic pulse (of width τ) which has a period T, is simultaneously sent to each individual wire to generate microbubbles through electrolysis. The individual bubble radius generated at each wire is found to depend on the period of the repeated transient pulse. This bubblemaker is used to generate a vertical column of bubbles. The second bubble maker involves the regulation of a transiting volume of air stored in a chamber placed between two solenoid valves. The air escapes through a fine pore fritted disk to produce a transient bubble cloud. Preliminary scattering measurements are presented. Comparisons with theory are made from estimates of the void fraction β, the average bubble radius r0, and other geometrical parameters of the cloud. [Work supported by the Naval Acad. Res. Council.]
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