Papers by Author: V.A. Cloquell-Ballester

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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: M.A. Garcia-Romeu-Martinez, Vincent Rouillard, Michael A. Sek, V.A. Cloquell-Ballester
Abstract: During the transportation phase of the distribution cycle, packaging systems are subjected to random dynamic compressive loads that arise from vibrations generated by the vehicle. The level and severity of these dynamic compressive loads are generally a function of the vibration levels, the stack configuration and stack weight. The container’s ability to withstand these compressive loads for sufficiently long periods depends on the material’s characteristics as well as the container design. The research presented herein tests the hypothesis that cumulative damage in the material under random dynamic compression will result in a reduction in the overall stiffness as well as an increase in the overall damping of the element. These are expected to be manifested, respectively, as a shift in the fundamental resonant frequency as well as an increase in the bandwidth of the frequency response function of the material at resonance when configured as a single degree of freedom system. The paper presents the results of preliminary experiments in which a number of corrugated paperboard samples were subjected to dynamic compressive loads by means of broadband random base excitation with a vibration table coupled with a guided dead-weight arrangement. The level of cumulative damage in the sample was continuously evaluated by monitoring the stiffness and overall damping of the sample which were extracted from the Frequency Response Function (FRF) of the system. This was obtained from continuous acceleration measurements of the vibration table and the guided dead weight.
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