ANALYSIS OF ELASTIC-WAVES IN NONUNIFORM RODS FROM 2-POINT STRAIN-MEASUREMENT

A method is established which permits evaluation of the histories of normal force and particle velocity at an arbitrary cross-section E of a non-uniform linearly-elastic rod from measured strain histories at two different cross-sections, A and B. Other quantities at E, such as stress, strain, displacement, acceleration and power transmission, can be determined in terms of the evaluated normal force and particle velocity. The method is an extension of that developed by Lundberg and Henchoz for uniform rods. Theoretical results, based on one-dimensional elastic wave theory, are provided for the general case as well as for cases of piecewise constant characteristic impedance. Experimental tests with different configurations of non-uniform rods and strain gauges show that the normal force histories determined at E with the present method (from measured strains at A and B) agree well with those obtained through direct strain measurement at E. © 1990.