In current antivibration packaging designs, transport vibrations are generally assumed to be Gaussian random vibrations, and the cushioning material is designed so that the acceleration root mean square (RMS) transmitted to a product is low. However, transport vibrations are often non‐Gaussian random vibrations, and therefore, it is necessary to carry out antivibration packaging design, taking into consideration the non‐Gaussianity characteristics and acceleration RMS of the transport vibrations. In this study, a kurtosis response spectrum was proposed, which is an antivibration packaging design index, taking into account the non‐Gaussianity of transport vibrations. A kurtosis response spectrum is a plot of the kurtosis of the acceleration response for a series of single degree of freedom (SDOF) systems to the base acceleration input, assuming that the packaged product is the SDOF system. The kurtosis response spectrum was applied to the actual transportation data, and the results confirmed that the kurtosis of product response acceleration is different, depending on the natural frequency of the packaged product. Experiments were conducted using a dummy packaged product, and the experimental results showed good agreement with those of the kurtosis response spectrum analysis. It can be concluded that the kurtosis response spectrum is useful to clarify the effect of natural frequency on the kurtosis response. By referring to the kurtosis response spectrum, packaging engineers can obtain the necessary information to perform antivibration packaging design, taking into account the non‐Gaussianity of transport vibrations.
The mechanical‐shock fragility testing methods applied to packaging and product designs according to Japan Industrial Standards Z 0119:2002 incur some problems related to statistical analysis. One such problem is that the applied shock levels are increased in steps. We cannot determine the true fragility values for each sample. This is called interval‐censored data. If the maximum level of non‐damaging shock is selected for each sample, the calculated average will be too small. Another problem is that the number of shocks is limited to a maximum of 5 or 6, so as to minimize the effect of the accumulated fatigue. Therefore, if we determine the considerably high first shock level, initial‐censored data are obtained by the failure of the product when subjected to the planned first shock. If we determine the considerably low final shock level, final‐censored data are obtained when the product has not been damaged by the application of the planned final shock. These problems make statistical analysis difficult. We therefore propose an improved analysis method for data including interval‐censored, initial‐censored, and final‐censored data, and provide examples in which the method is applied to the results of a drop test. The results of the examples show that the proposed method is practical and that the censored data yields errors and loss of accuracy for the statistics. Finally, by means of a comparison between the staircase method of ISO 7765‐1:1988 and the method of JIS Z 0119:2002, we analyse the advantages and disadvantages of the respective methods. Copyright © 2017 John Wiley & Sons, Ltd.
Packaging vibration tests are used to evaluate the vibration durability of packaged products by simulating transport vibration. Currently, the vertical Gaussian random vibration test is commonly used. However, in actual transport vibration environments, non-Gaussian random vibration occurs along various axes simultaneously.To simulate actual transport vibration environments accurately and realistically, this study developed a simultaneous three-translational-axis vibration test that considers the three-axis simultaneity of shock events, which is unique to non-Gaussian vibration. In addition, to verify the effectiveness of the test, an experiment on the collapse of packaged products was performed by using three sets of vibration data (actual transport vibration data and vibration data with and without the three-axis simultaneity of shock events), and the collapse time for each dataset was measured. The collapse time obtained using the vibration data with the three-axis simultaneity of shock events was closer to the collapse time obtained using the actual transport vibration data than the collapse time obtained using the vibration data without the three-axis simultaneity of shock events. Therefore, the simultaneous three-translational-axis vibration test that does not consider the three-axis simultaneity of shock events may give different results from those obtained under actual transport vibration conditions. Therefore, to simulate actual transport vibration environments accurately and realistically, a simultaneous three-translationalaxis vibration test that considers the three-axis simultaneity of shock events should be performed.
An optimum cushioning package, which is neither excessive nor inadequate, must be designed to ensure cushioning performance that maintains an acceptable failure rate during transportation while also minimizing packaging costs. For this purpose, statistics pertaining to transport hazards and product shock strength must be engaged.The proposed study presents a test method to enhance the statistical accuracy of mechanical shock fragility of products. Sample statistics are invariably unknown; hence, optimum test-setting values cannot be determined at the beginning. The proposed test method has been devised for determining optimum test-setting values of the (n + 1)th sample using statistics of n samples being tested. An improvement in the estimation accuracy of the variation coefficient for the critical-velocity-change test was confirmed via simulations performed using the proposed method. Optimization of the test-setting value has also been experimentally confirmed. A comparison of histograms and statistics obtained using experimental results has demonstrated that the proposed method can better estimate distribution shapes compared with the simple method. An example of the application of experimental results to stress-strength models has also been described. The observed result has a considerable influence on the design of cushioning packages, thereby demonstrating effectiveness of the proposed method. KEYWORDScushioning package design, damage boundary curve, mechanical shock fragility test, shock test, statistical analysis | INTRODUCTIONPackaging costs are often required to be maintained as low as possible given the large quantity of mass-produced products being shipped.However, receipt frequent complaints pertaining to product damage during transportation is not acceptable. This necessitates optimization of the cushioning design to ensure optimum quality of transport packaging. Several cost-minimization techniques have been proposed in extant studies pertaining to quality assurance. 1-3 Quality costs can be classified into three major cost categories-prevention, appraisal, and failure. 1 As depicted in Figure 1, Juran demonstrated a trade-off relationship between the total prevention, appraisal, and failure costs.Prevention and appraisal costs are considered transport-packaging costs related to packaging materials and transportation as well as those concerning cushioning design and evaluation tests. Failure costs include damage claims during transportation caused by insufficient cushioning capacity and opportunity loss owing to loss in company reputation caused by damage during transport. The quality of transport packaging pertains to whether products can be transported without being damaged; hence, the optimum quality level that minimizes the quality cost can be determined in terms of the "failure rate during transportation." In other words, packaging designs with failure rates that minimize the quality cost during transportation are considered optimum.Designing optimum cushioning packages requires a methodology t...
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