Marginal oscillator for acoustic monitoring of curing of plastics

Changes in the ultrasonic properties of fiber-reinforced plastics during the curing process are monitored by a marginal oscillator to determine the degree of cure. The plastic sample and transmitting and receiving transducers serve as a narrowband acoustic resonator and are placed in the feedback lo...

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Bibliographische Detailangaben
Hauptverfasser:	THOMAS, III, LEWIS J
Format:	Patent
Sprache:	eng
Schlagworte:	AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F,C08G AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING BASIC ELECTRONIC CIRCUITRY CHEMISTRY COMPOSITIONS BASED THEREON ELECTRICITY GENERAL PROCESSES OF COMPOUNDING GENERATION OF NOISE BY SUCH CIRCUITS GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING,BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN ANON-SWITCHING MANNER INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIRCHEMICAL OR PHYSICAL PROPERTIES MEASURING METALLURGY ORGANIC MACROMOLECULAR COMPOUNDS PERFORMING OPERATIONS PHYSICS SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDEDFOR SHAPING OR JOINING OF PLASTICS TESTING THEIR PREPARATION OR CHEMICAL WORKING-UP TRANSPORTING WORKING OF PLASTICS WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL WORKING-UP
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Beschreibung
Zusammenfassung:	Changes in the ultrasonic properties of fiber-reinforced plastics during the curing process are monitored by a marginal oscillator to determine the degree of cure. The plastic sample and transmitting and receiving transducers serve as a narrowband acoustic resonator and are placed in the feedback loop of a variable gain amplifier; using gain control the system is allowed to marginally oscillate. The resonant frequency of the sample and amplifier gain are related to the velocity and attenuation of sound in the plastic and are determined by measuring the received signal frequency and amplifier gain control voltage. The system has frequency locking means to track changes in resonant frequency during the cure cycle.