Measuring and testing – Vibration – Resonance – frequency – or amplitude study
Patent
1979-06-22
1981-12-29
Kreitman, Stephen A.
Measuring and testing
Vibration
Resonance, frequency, or amplitude study
73799, G01H 1300, G01N 332
Patent
active
043076106
ABSTRACT:
A method for measuring crack propagation in samples as a function of the number of load cycles is proposed wherein changes in the frequency response of a mechanical impedance of a sample which is to be tested is registered. At a pulsation frequency, which corresponds to the resonant frequency of the sample, there is a rise in the resonance of the mechanical impedance, defined as the quotient of the speed of movement of the sample and the applied pulsating force. Since, when a crack grows in the sample, its elastic constant decreases along with the cross-sectional area, the frequency response of the sample shifts towards lower frequences. To carry out the process of the invention it is suggested that the phase of the above mentioned impedance or an impedance which is dependent on it should be detected, or else to register the impedance magnitude whilst keeping the force acting on the sample or the speed of movement constant, or else to register the force or speed of movement as a function of the number of load cycles and standardized with respect to the appropriate values of momentary load or speed of movement.
REFERENCES:
patent: 3622404 (1971-11-01), Thompson
patent: 4003246 (1977-01-01), Cain
patent: 4026142 (1977-05-01), Jacobs
patent: 4128011 (1978-12-01), Savage
Kreitman Stephen A.
Swiss Aluminium Ltd.
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