Monitoring the Evolution of Damage in Packaging Systems under Sustained Random Loads

The ability of protective packaging systems to withstand dynamic loads during transportation is an important consideration when it comes to selecting a suitable material. The performance characteristics of packaging systems are best determined by subjecting the systems (such as cushioning materials and containers) to sustained random loads under controlled conditions. It is during these fatigue endurance tests that the loss of structural integrity of a material or an element needs to be quantified. The research presented herein uses two recently developed continuous structural integrity assessment techniques to evaluate variations in the mechanical properties (namely stiffness) of typical packaging elements. The first technique is based on the short‐time Fourier transform, and the other uses an adaptive digital finite impulse response (FIR) filter technique developed by the authors. The effectiveness and the limitations of the techniques were evaluated by undertaking selected controlled experiments during which damage was simulated by varying the length of a single degree‐of‐freedom vibratory system subjected to random base excitation. The materials used for the controlled experiments include steel, aluminium, acrylic and carbon fibre. Results show that, although both methods are capable of identifying the level of damage and the time at which it occurs, the FIR technique is generally more sensitive and better able to detect small changes in stiffness. Finally, the ability of integrity assessment techniques to monitor the progression of damage in real packaging elements, such as biodegradable air cushions and corrugated paperboard containers, was established. The analysis of real protective packaging elements subjected to random loads using both structural integrity assessment techniques yielded positive results. Generally, the adaptive FIR technique was found to be more sensitive in detecting small changes in system characteristics, even when the estimates were obtained with relatively coarse temporal resolution. Overall, the results presented in this study indicate that the adaptive FIR technique can be a practical and effective tool for establishing the ability of materials and structures to withstand sustained random loads. Copyright © 2011 John Wiley & Sons, Ltd.     

Monitoring the Condition of Non‐linear Packaging Materials Subject to Varying Excitation Levels Using a Reverse Multiple Input/Single Output Based Approach

During transportation, protective packaging is subjected to random dynamic compressive loads that arise from random vibrations generated by the vehicle. The ability of the protective packaging to withstand these dynamic compressive loads depends on the environmental vibration levels, the nominal stresses and the material's characteristics. Previous research has shown that cumulative damage, in the packaging system under random dynamic compression, will result in a change in the overall stiffness of the system. This change is manifested as a shift in the system's fundamental resonant frequency. Natural frequency estimates are often extracted using a least squares regression curve fit applied to an estimate of the system's frequency response function. Frequency response function estimates are generally obtained using the Fourier transform with a single input/single output (SISO). This approach is suitable for many applications; however, it is not well suited to non‐linear systems subjected to non‐stationary excitation where the vibration level (overall root‐mean‐square value) can vary. This paper investigates the use of an optimised reverse multiple input/single output algorithm for reliably tracking variations in the condition of packaging elements subjected to excitation with varying magnitude (root‐mean‐square). Results are presented from the analysis of physical experiments performed on expanded polystyrene cushions as well as empty corrugated paperboard containers. The experiments performed using the polystyrene samples were designed to limit natural variation in the system's natural frequency; whereas the paperboard samples were allowed to naturally damage under dynamic loading. Copyright © 2015 John Wiley & Sons, Ltd.     

The dynamic behaviour of stacked shipping units during transport. Part 1: model validation

This paper deals with the dynamic behaviour of stacked packaging units when subjected to vertical vibrational inputs as experienced in transport vehicles. Although the vibrational performance of single‐unit packaging systems has been thoroughly studied, the behaviour of stacked packaging units is not fully understood. The complexity of the problem is compounded when the effects of vertical restraints are taken into account. The paper presents the development of a numerical computer model designed to predict the dynamic response of stacked package systems when subjected to vertical vibrational excitation. Provisions have been made to account for the effects of vertical restraint tension and stiffness. In addition, a physical model representative of a generic stacked packaging system has been developed to assist in validating the numerical model. The paper includes results from preliminary experiments in which the frequency response functions of the models were evaluated and compared. The validity of the numerical model in the time domain was tested using random burst excitation signals. These preliminary experiments reveal that, when the effects of frictional damping are taken into account, the numerical model can be used to generate reasonably accurate predications of the dynamic behaviour of the equivalent physical system. Copyright © 2004 John Wiley & Sons, Ltd.     

The Statistical Characteristics of Maxima of Contact Force in Stacked Packaging Units under Random Vibration

Stacked packaging units are the major form when transporting packaged products. In these stacked packaging units, the maxima of contact force between boxes are closely related with fatigue, the main failure form of packaged products during transportation, which can be simulated by random vibration. Therefore, this paper proposes a probability density function (PDF) of maxima for stationary Gaussian random signal with non‐zero mean and non‐unit variance to study the statistical characteristics of the maxima of contact force in three‐layer stacked packaging units, which is of vital importance to the fatigue evaluation. The proposed PDF of maxima is controlled by three parameters: spectral width parameter ? , mean value μ_x and variance σ_x . These three parameters are obtained respectively under three different impact factors, namely, constraint, acceleration excitation and location of contact surface. Power spectrum density (PSD) of contact force and PSDs' Q factors are also calculated. Relations and variations of the three parameters of PDF of maxima, PSD and PSD's Q factor under different impact factors are discussed in detail. It is found that the system of the three‐layer stacked units with a wide‐band excitation (? → 1) as input and contact force (?< 1) as output can be regarded as a relatively narrow band system. And the proposed PDF of maxima proves to be an effective method to investigate the statistical characteristics of the maxima of contact force between boxes in the stacked packaging units. Copyright © 2017 John Wiley & Sons, Ltd.     

Estimation of the Dynamic Properties of Non‐linear Packaging Materials Using a Reverse Multiple Input/Single Output Based Approach

During the distribution phase, packaged consignments are exposed to a variety of environmental hazards (such as vibrations) that, if excessively severe, may cause damage to or even destroy the product. Structural deterioration can be tracked by monitoring variations in the packaging system's modal parameters, particularly its natural frequency (stiffness). Natural frequency estimates are often extracted using a least‐squares regression curve fit, applied to an estimate of the system's frequency response function (FRF). FRF estimates are generally obtained using the Fourier transform with a single input and single output (SISO). This approach is suitable for many applications; however, as the non‐linearity of the system under analysis increases, the ability of this technique to accurately monitor changes in the system will decrease. In addition, when the excitation to the non‐linear system is varied (increased or decreased amplitude), a SISO‐based approach may indicate a shift in natural frequency (as a result of the varied input) even though no change in the condition of the system has occurred. This paper discusses an approach that is designed to separate the linear component of the system's FRF using a reverse multiple input/single output (RMISO) algorithm. Such separation will allow traditional modal parameter extraction (curve fitting) techniques to be used to monitor the condition of non‐linear systems. The paper presents the results of experiments in which expanded polystyrene samples were subjected to broad‐band random base excitation with a free‐moving load placed atop the cushion sample. Continuous acceleration measurements of the vibration table and the free‐moving load were used to compute the FRFs of the cushions, and the differences between a conventional (SISO) approach and the proposed RMISO‐based parameter extraction technique were evaluated. Copyright © 2014 John Wiley & Sons, Ltd.     

Comparative Life Cycle Assessment of Packaging Systems for Extended Shelf Life Milk

The aim of this study is to carry out a comparative analysis of the environmental impact of different packaging systems used for extended shelf life milk. The analysis, carried out exploiting the life cycle assessment approach, takes into account the packaging manufacturing process, the food packaging process, the transport phases and the end‐of‐life management of the different packaging systems. The packaging end‐of‐life is modelled by considering three possible options, such as recycling, thermo‐valorization with energy recovery and landfill. One litre of extended shelf life milk is used as the reference unit, while multilayer cartons, polyethylene terephthalate bottles labelled with shrink sleeve film and high‐density polyethylene bottles are analysed as the packaging types. The key characteristics of each component of the three packaging systems were either provided by packaging manufacturers or derived from data available in literature. The evaluation of the end‐of‐life impact was performed considering the Italian scenario, exploiting, in particular, the data provided by specific Italian consortia. Other data for the inventory analysis phase were extrapolated from the SimaPro databases (e.g. Ecoinvent or Plastic Europe Database). Cumulative energy demand and CML2001 were adopted as the impact assessment methods. The results obtained show that the multilayer carton system is the less environmentally impactful option for almost all the considered impact categories and that its environmental impacts are, on average, more than 12% lower than high‐density polyethylene system and more than 34% lower than polyethylene terephthalate with shrink sleeve label. Copyright © 2016 John Wiley & Sons, Ltd.     

Integrated optoelectronics for optical interconnections and optical processing

Integrated optoelectronics using III–V compound semiconductor technology has so far shown exciting advances for application in optical telecommunication systems. New applications of this technology are in optical interconnections and signal processing systems. The technology is expected to be very effective in solving the wiring limit in data transmission within electronic systems, using the advantages of optical techniques such as high data transmission rate and high parallelism, and thus improve the performance of overall systems. Optical interconnection devices currently being developed aim both at multiplexing vast amounts of data and exhibiting flexible interconnection functions using the advantageous characteristics of light. Future research is expected to explore new techniques such as that for multiplexing and processing data in the wavelength division as well as for integrating functional devices in two-dimensions. Synergetic collaboration among materials and processing, design and fabrication, and packaging areas is extremely important and this will lead to practical optical interconnections and signal processing systems.     

A Productivity Study of Digital Printing in the Packaging Industry

In this study, the suitability of digital printing is evaluated in short runs in packaging industry. The image quality of digital printing is high enough to be used in packaging. The advantages of digital printing and modern converting processes include e.g. the possibilities of using variable data, on‐demand manufacturing and cost‐effectiveness within short print runs. The limitations may include a smaller colour gamut compared to traditional presses, format size, productivity and lower printing speed. In addition, the variety of substrates for use is smaller than in traditional printing. The productivity of the world's first integrated digital printing line designed for short runs was tested by simulating various packaging runs in production. For further analysis, an MS Excel calculation tool was developed. In the calculations, the productivity of a digital packaging line was compared with that of a standard packaging line based on an offline offset printing technique. The cost advantages to be achieved by digital printing techniques in short runs are discussed in two scenarios. The scenarios address the subjects' break‐even point and inline production process. The results of the study show that it is possible to achieve significant cost savings using the inline digital printing and converting systems when compared with traditional offline manufacturing systems in short runs. However, as there are numerous variables included to the production process, it is impossible to present any exact numbers for the break‐even point. In this study, the break‐even point calculated is estimated to be in the range of 4000–8000 packages, depending on the package and sheet sizes. The greatest difference in price per package occurs when the runs are below 2000 packages. Based on the calculations, the inline process itself can decrease the payback time for the machine line as much as 20–35%. One significant factor to be mindful of is that when digital printing is used in the short runs, it often releases machine time from the traditional presses. This part of the analysis has not been included in this study, but using the calculation tool, it is easy to simulate different scenarios and perform further analyses on the systems. Copyright © 2011 John Wiley & Sons, Ltd.     

不同内容物的包装容器振动特性试验

目的探讨包装容器的扫频特性以及随机激励下的频域和时域特征,讨论不同内容物对包装容器振动特性的影响。方法针对液体、固体不同内容物对包装容器进行扫频和随机振动试验,以振动强度,内容物体积为变量对比分析不同容器加速度响应,频域分布特点和响应能量。结果在扫频试验中,内容物为固体时,共振频率集中在50 Hz附近;内容物为液体时,当其体积占包装容器总容积体积的比值为50%、80%时,容器一阶共振频率在20 Hz附近。在随机试验中,内容物为液体时包装容器响应加速度功率谱密度分布较固体时分散,加速度响应能量整体较固体大,在内容物占包装总容积体积的比值为50%时响应能量最大,激励强度增加对内容物为液体的包装容器响应影响明显,正态分布能很好地描述了包装容器的随机振动响应时域分布;内容物为液体时加速度响应分布与高斯分布偏离明显。结论内容物不同会造成包装容器共振频率、响应加速度、功率谱密度分布等的显著差异。