Papers by Keyword: Cushioning

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Authors: Michael A. Sek, Vincent Rouillard
Abstract: This paper presents some of the latest results of a research project aimed at using composite corrugated paperboard structures for protection of products against mechanical shocks and vibration during transportation and handling. Specifically, the behaviour of multi-layered corrugated paperboard (MCPB) under shock loading is investigated. Conventionally, packaging cushion design requires the determination of the maximum expected shock levels or equivalent drop which are usually determined from statistical analysis of original field measurements. With this approach, it is generally acknowledged that the cushioning element is engineered to provide adequate protection for statistically likely events but not for extreme events with low statistical likelihood. It is reluctantly accepted that, should it occur, the latter will result in damage to the product. MCPB can be formed with a broad range of compressive characteristics and with various proportions of elastic and plastic behaviour. The objective of this experimental investigation was to determine the optimum elastic/plastic proportion to extend the protective range to include large shock levels. The experimental results obtained include the effects of compression history on the stress-strain properties of MCPB as well as the behaviour of the material in both virgin and pre-compressed form under impulsive loads. The mechanism of deformation of the corrugations (flutes) was studied using high-speed video equipment. The complex acceleration signals produced during deformation of the composite corrugated paperboard cushions under shock loading were analysed by means of the shock response spectrum. Experiments have shown that inserting a sacrificial crumple element of virgin corrugated paperboard at the optimum contact area ratio dramatically lowers the overall level of the resulting shock response spectrum. This has the effect of increasing the allowable drop height for a limited number of extreme events. The main conclusion of the research is that MCPB in both virgin and pre-compressed forms can be combined to provide significantly enhanced protection to products against mechanical hazards during distribution.
Authors: M.A. Garcia-Romeu-Martinez, Michael A. Sek, Vincent Rouillard, V.A. Cloquell-Ballester
Abstract: During distribution, consignments undergo numerous handling processes both mechanized and manual. These operations are known to produce drops and impacts of varying severity which have a potential to cause damage to the product. These shocks are the main parameters required for the optimum design of protective packaging systems. The severity of the shocks is often described in terms of their effective (free-fall equivalent) drop height (EDH) and impact orientation, in order to facilitate the laboratory testing conducted on a free-fall apparatus. The preferred approach is to survey the shocks with self-contained tri-axial shock recorders and process the data in such a way that statistical distributions of expected drop heights and orientations are obtained. On the other hand the Real Drop Height (RDH) method, based on the measurement of free fall time, is also used, mainly to discriminate between free-fall events and more commonly occurring complex causes of shocks, primarily for the quality control of distribution environment. The focus of the paper is on the EDH method and on the use of characteristic parameters of the tri-axial acceleration shock pulse to determine the EDH. An accurate estimate of the coefficient of restitution between the instrumented test package and the impact surface must be known and this poses a problem as it cannot always be established for every event during distribution. Consequently, the adopted approach is to calibrate an instrumented test package and obtain an estimate of the coefficient of restitution between the package and a test impact surface which is generally assumed to be hard relative to the cushioned package. The paper addresses the pitfalls and investigates various algorithms of determining the EDH from recorded shock data. It presents an analysis of the influence and errors associated with various methods used to estimate velocity change from characteristic parameters of a shock pulse such as the pulse width, the peak acceleration and its temporal location. The effects of analyzing the orthogonal acceleration vectors separately, as opposed to the resultant vector, are discussed. The results of a number of free-fall experiments, undertaken in controlled conditions, are used to validate and calibrate the proposed method for determining the EDH for free-fall drops on hard surfaces.
Authors: Man Ru Chen, Ju Fei Zhang
Abstract: In the paper, the monolithic design of cushion package for airdrop system is summarized. In the meantime, the author improves the former package in the foundation of entire recognizing and introduction of the former research. The airdrop package not only effectively overcomes the wallop of ground, but also prevents the rebounding and side rolling when the system fall into the ground, which really has an effect on the airdrop system.
Authors: Chen Zhong, Katsuhiko Saito
Abstract: To evaluate quantitatively the performance of cushioning materials, a cushion curve is indispensable. However, the desired cushioning effect may sometimes be absent when we use the cushion curve to design a transport package. In addition, to plot the cushion curve, massive dynamic compression tests are traditionally necessary. Thus, large amounts of labor and material resources are required. Therefore, we used expanded polyethylene and laminated-board cushion as test materials to represent typical cushioning materials, and proposed simplified performance evaluation methods based on certain dynamic compression tests. An analysis of the experimental results showed that to obtain a more accurate packaging design, the shearing effect must be taken into account when using the cushion curve; For both plastic and paper cushions, new proposed performance evaluation methods significantly reduce the number of dynamic compression tests needed to accurately evaluate an actual packaging design.
Authors: Wei Hao Xie, Bin Zhou, En Xiao Liu, Yuan Geng Zhang
Abstract: The aircraft recovery systems have been drawn more attention for its ability on offering cushioning landing in recent years. However, many previous researches mainly focus on the cylinder or rectangle air bags where the upper surface is orthogonal to the flank side. This kind of airbag will not meet the requisite stability and security because it might be bended by payload under the misalignment forces. In this light, a more stable frustum of cone parachute-airbag system is proposed and the cushioning mathematical model is established. Based on the theories of thermodynamics and mechanics, the expressions of velocity and deceleration are derived. The effects of initial parameters on airbag cushioning properties are analyzed and the simulation results are shown. The results can provide references for the future design of aircraft recovery system.
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