Experimental Study Of Dynamic Response Of Two Layers Stacked Packaging Units

Stacked packaging units is the common form of products in the modern logistics. Because of unreasonable transport packaging design, stacked packaging in logistics which tends to damage or failure in function under the vibration and impact, caused huge economic loss. It is important to investigate the dynamic response of stacked packaging units in logistics for packaging designers to design protective packaging, so as to protect products better and reduce the packaging costs.This dissertation investigates the dynamic response of two layers stacked packaging units with different constraints conditions, different input spectral shape and different input intensity of acceleration power spectral density(modified ASTM D4169 Truck Level I-III, designed Level IV and designed band limited white noise I-IV). Experiment was designed according to the actual situation of goods transportation, and the sine sweep and random vibrations were conducted to stacked computers and stacked apples packaging respectively. Acceleration sensors and I-Scan system were respectively used to measure the acceleration response of products and the dynamic force between the stacked boxes. MATLAB was used to process the experimental data.Sine sweep experiment results show that the resonance frequency, resonance acceleration response of product and dynamic pressure ratio between boxes are obviously influenced by the constraint to stacked packaging units. Random vibration experiment results show that the acceleration PSD of upper products is mainly controlled by the first resonance frequency, and the acceleration PSD of lower products controlled together by the first and second resonance frequencies. The dynamic pressure PSD between boxes is mainly controlled by the first resonance frequency. The acceleration response of upper product in the area of first resonance frequency is much bigger than that of the lower product. The acceleration response of computers is increased, however the acceleration response of apples is decreased with the constraint strengthen. By comparing the responses of product under the action of two shapes of input acceleration spectrum, the dynamic characteristics of stacked packaging units can be interpreted as narrow band pass filter.Distribution diagram of dynamic force obtained from I-Scan system shows that dynamic force mainly exert on corner and short edge of boxes, the trajectory diagram of dynamic force shows that pitch motion of boxes was fade out with the constraint strengthen or decreasing of vibration level. According to the force level-crossing diagrams, the form of diagrams became more abrupt with the decreasing of vibration level, meaning a narrower dynamic force levels was experienced. The diagrams move right and become smoother with the constraint strengthen, meaning a lager and broader force levels was experienced. The probability density function of force level-crossing diagram between contact surfaces is of Weibull distribution. In the case of lower vibration levels, it is of normal distribution.