Non-destructive evaluation of structural members

Abstract

Disclosed are testing apparatus and methods for estimating mechanical properties of nonhomogeneous materials, such as lumber and other wood materials and composite materials, particularly elongated slender members. The testing is appropriate for estimation of tensile and bending strength, tensile and bending moduli of elasticity and possibly other mechanical properties. The testing apparatus include a test specimen support which holds the specimen during testing in a manner which minimizes attenuation of the stress wave which is intentionally generated in the specimen to help predict the mechanical properties. The specimen supports also preferably include means for weighing the specimen which is combined with size information gathered through an optical scanning system thereby allowing the density to be obtained automatically. The specimens are impacted to produce a moving stress wave which is advantageously a longitudinal stress wave which moves longitudinally through the elongated slender members being reflected within the member preferably a number of times. The amplitude of the moving reflected stress wave is sensing with respect to time to allow the velocity and attenuation rate of the stress wave to be determined. The information is preferably communicated to a computer which automatically processes the sensed information and compares it to preprogrammed parameters which allow the accurate estimation of one or more of the predictable mechanical properties. The tested specimens are advantageously sorted according to the mechanical properties or appropriately marked to indicate the grade, strength or other appropriate measure of value of the specimen.