Abstract
The influence of prestrain on the propagation of mechanical waves along a slender rod of low-density unoriented polyethylene was experimentally investigated. The investigation consisted of two major parts: first, a uniaxial continuous-wave technique was used to determine the dynamic mechanical properties of the polyethylene in the form of the frequency-dependent phase velocity and damping factor for frequencies spanning the audio spectrum and for levels of uniaxial static prestrain up to 10 percent. A linear incremental dynamic viscoelastic behavior about a state of finite-static prestrain was shown to obtain over the range of strains and frequencies used.
In the second part, the propagation of an incremental strain pulse along a slender rod of the same material used in the first part was investigated. With the rod in a state of static prestrain, an incremental impact-induced strain pulse was introduced into the polyethylene rod and monitored at two positions along the rod. Assuming a linear incremental dynamic viscoelastic behavior of the material, the equations necessary to describe the resulting uniaxial strain as a function of time and position along the rod are presented and the solution obtained by Fourier transform methods. The resulting Fourier inverse transform was numerically evaluated, using the material properties determined in the first part. The strain measured at the first position was used as the input boundary condition for computing the strain at the second position.
Results of the continuous-wave studies indicate that the phase velocity decreases and the damping factor increases with increasing prestrain in the range of prestrains used. The change in the phase velocity with prestrain is relatively uniform over the audio-frequency range. Good correlation of the leading edges of the experimentally measured and numerically synthesized strain pulses supports the high-frequency phase-velocity data of the first part.
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Stevens, A.L., Malvern, L.E. Wave propagation in prestrained polyethylene rods. Experimental Mechanics 10, 24–30 (1970). https://doi.org/10.1007/BF02320082
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DOI: https://doi.org/10.1007/BF02320082