Measuring and testing – Vibration – By mechanical waves
Patent
1991-09-20
1993-08-24
Chapman, John E.
Measuring and testing
Vibration
By mechanical waves
73598, 73600, 73618, G01N 2904
Patent
active
052378705
ABSTRACT:
Method and apparatus are described for using stress wave measurements in the estimation of quality of finger joints in wood and quality of lumber, where quality is typically defined as strength. Application and measurement of stress waves in the transverse direction of the material allows localized measurements to be made, and features developed from this information are used in the quality estimation. A feature is a quantifiable characteristic developed from stress wave signals which can be used either by itself or in combination with other features to estimate quality. Examples of features include the propagation velocity of a stress wave, the attenuation of a stress wave, the difference in stress wave propagation times measured at different locations along the lumber, and the effects on amplitude and phase of frequency components of a stress wave. Treating features together as a feature vector and as input to an estimator function, estimated quality can be evaluated. The ability of the method and apparatus can be improved in some cases by performing the stress wave measurements in the presence of externally applied bending, tensile or torsional stress.
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Bechtel Friend K.
Fry Ray L.
Logan James D.
Chapman John E.
Metriguard Inc.
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