Abstract

A complete damping-stiffness characterization of a given medium can be derived from the development of a propagating stress pulse between two fixed locations. The extensional stiffness is determined by the phase velocity, whereas the damping is measured by the pulse attenuation [1]. Thus far this approach has been limited to axial impact of long, slender rods. The multiple frequency content of a rectangular-pulse restricts the test specimens to slender rods or fibers in order to avoid pulse dispersion as a result of lateral inertia effects [2]. An improved stress pulse method for more realistic damping measurements in a broader range of test specimens has been developed recently [3]. It is referred to as the “Sine-Pulse Propagation” technique since the commonly used impact pulse is replaced by a sine-shaped pulse, which usually contains one full cycle. Its main advantage as compared to traditional methods for damping characterization, such as the “Hysteresis Loop” approach, is that it minimizes the loss of vibratory energy in the testing apparatus, which is the main contaminating form of conventional damping data [4].

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