Issue link: http://cp.revolio.com/i/399448
While this complex dynamic behavior can drastically alter the behavior of a packaging system it is not "easy" to capture experimentally. Currently there is no industry standard technique for the characterization of cushion system frequency response. Common techniques assume only a linear response and are unable to capture the "bending" behavior. However, techniques common in the study of nonlinear systems in other fields can be adapted to experimentally characterize the response. One such technique is referred to as the Step-Sine technique. The apparatus represents a simplified packaging system with the mass representing the product and the rod of foam is the protective packaging. The system is excited at a set acceleration level and frequency until the top-mass reaches steady state. Once at a steady state, the magnitude and phase are recorded. The input frequency is then increased by a small increment, typically ΒΌ Hz, and allowed to dwell until steady state, and the magnitude and phase are recorded. This process is repeated, stepping up in frequency from below resonance to above and then the direction is reversed. The process generates frequency response curves as illustrated in Fig. 2 in which three curves were produced for the same foam sample at various input acceleration levels. Figure 1: Typical linear (a) and nonlinear (b) frequency response plots. Figure 2: Typical nonlinear experimental frequency response of foam at various input acceleration levels. 8 Newsline