USA As Represented by Secretary of the Navy

Walter M Madigosky

Gilbert F Lee

Material is periodically indented by a probe driven at an oscillation frency by a shaker regulated by an analyzer to which input measurement data is fed from a sensing head connecting the shaker to the probe for in situ measurement of material resistance to indentation to which such input data relates. A computer connected to the analyzer is programmed to calculate steady-state data on dynamic material properties as a time dependent function, from outputs of the analyzer restricted to limits determined from the input measurement data.

In situ dynamic material property measurement system

A fast and reliable method is disclosed for measuring the dynamic mechanical properties of a material, particularly its modulus of elasticity and loss factor. By this method the acoustic characteristics of a material can be determined. An elongate strip of material, whose properties are desired to be known, is provided with miniature accelerometers fixedly secured to its opposite ends. One end of the strip is excited by a random noise source which travels toward the other end where that end and accelerometer is allowed to move freely (unrestrained). The accelerometers measures the ratios of acceleration at two locations over an extended frequency range of 0.2 Hz to 25 KHz, and the information is processed through a fast fourier transform spectrum analyzer for determining amplitude of acceleration ratio and phase difference between the two accelerometers from which Young's modulus and loss factor for that material are determined.

Method for measuring material characteristics

A method and apparatus for measuring the dynamic material constants of rur compounds. The rubber compound is tested in strip form by attaching one end of the strip to an electromechanical shaker while the opposite end of the strip is suspended under constant tension. The electromechanical shaker propagates an acoustic wave in the test strip and a piezoelectric transducer positioned at a first point on the test strip measures the mechanical response of the strip for phase and amplitude. The shaker is programmed to step piecewise over the frequency range from 100 Hz to 40 KHz by a frequency synthesizer. The distance between the shaker and the transducer is changed and data is obtained for a second point on the strip. The test values obtained are used to calculate Young's Modulus and the loss factor for the rubber compound.

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Silver Spring, MD, United States of America

Walter M Madigosky