Transmission and Reflection of Extensional Stress Pulses at the Junction of a Straight Bar and a Helix

We present the analytical and experimental study of a mechanical pulse filter. The filter is an unbounded assembly composed of a straight bar joined tangentially to a helix. The Fourier time transform of the pulses and the complex frequency response of the assembly are employed to obtain the analytical solutions. It is shown that for the assembly to be effective as an extensional pulse filter, the pulse duration should be longer than the ring mode period, i.e., the time required for a pulse traveling with the extensional bar velocity to travel around one turn of the helix. Experimental results are presented which verify the analytical solution.