Cushioning materials are used in order to protect products from shock and vibration during transportation. Normally, it is often difficult to achieve both cushioning and damping, because cushioning materials suitable for cushioning are different from ones suitable for damping. The maximum acceleration during an impact has been used as an index for cushioning, and the RMS value of acceleration during a vibration as an index for damping. If both the values can be reduced, it can achieve both of the above. In this paper, it was considered that both the values could be reduced by adding a feature to the shape of the stress-strain curve of cushioning materials. Here, based on a general stress-strain curve, the rise was changed to a steeper shape, and the changes of both the values were examined. As a result, it was found that the RMS value could be reduced, because the resonant frequency of packaged freights was higher than the dominant frequency band of truck bed. It was found that the appropriate shape change had almost no effect on the maximum acceleration. From these, it is considered that the steep rise of the stress-strain curve will help to achieve both of the above.

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In our previous research, we reported the effect of temperature and pressure (0.32, 0.42, and 0.52 MPa) on heat-sealing strength for two types of the heat-sealed sterilized bag. The first composed system was plastic film and sterilized paper. Another composed system was plastic film and polyethylene nonwoven fabric. As the result, sealing strength between plastic film and sterilized paper increased with increase of heat- sealing pressure. The sealing strength between plastic film and polyethylene nonwoven fabric did not increase with increase of heat-sealing pressure. In this study, we tried to evaluate the effect of heat-sealing temperature and lower pressure (0.1, 0.2,0.3 MPa) between plastic film and polyethylene nonwoven fabric. In this study sealing strength between plastic film and polyethylene nonwoven fabric increased at range of relative low sealing pressure, 0.1 to 0.3 MPa. From the results including previous studies sealing strength we concluded that existence of rigid and non-melt cellulose including in sterilized paper affects sealing property.

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Critical acceleration of inside product should be identified numerically for optimized package. JIS has a testing method for shock strength of product as Damage Boundary Curve, DBC, that requires multi-specimen and a specialized shock machine can generate the trapezoidal pulse. However this method is not spread widely due to their complex testing method. This paper considered a simple test method with single specimen only using the half-sine shock pulse. In this method, to reduce the number of specimen, the critical velocity change test was skipped. Instead of this test, the lowest value of critical velocity change in the practical range was applied to estimate DBC with more severe condition. Calculation method of DBC was considered using the natural frequency and the response acceleration of fragility part that calculated by the shock response spectrum with half sine pulse at the critical acceleration and critical velocity change. Suitable critical acceleration can be determined by derived DBC and the drop height of package drop test. Moreover, to lead the safest critical acceleration that can withstand toward any kinds of shock pulse, the calculation method was considered using the DBC by square shock pulse

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