Packaging systems always endure some type of damage during transportation, and Wöhler curves are typically used to determine the mechanical wear evolution of a packaging system. Damage estimations can be performed using a Rainflow method, but continuous stress recording is required. However, this recording is not always possible, so global transportation vibrations are represented by the power spectral density (PSD). In this paper, the damage of a system according to the Wöhler curve was studied. The Basquin model was used to determine the mechanical wear evolution of the system, and the mechanical behaviour was established by extracting the Basquin coefficient b and the constant system C from the Wöhler curves. A Wöhler curve was further realized for a packaging system, and its Basquin coefficient b and system constant C were also extracted. Damage is estimated by the accumulation of the stress cycles using the PalmgrenMiner rules. In this paper, the maximum peaks of the cycle were detected in a signal. The density probability of the maximum stress apparition was also constructed from a multivariate Gaussian model. PSDs have the same statistical properties as the corresponding temporal events, so these statistical properties were extracted by the spectral moment method. Furthermore, a damage equation was proposed using the PSD, and the damage induced by different PSDs was determined from the damage equation and compared with the actual duration on a vibration table. INTRODUCTIONThe global road network is growing each year, and it is composed of millions of kilometres. Various types of roads or road conditions are often encountered with longer travel distances with countless stress possibilities. The study of these stresses is a crucial point for determining the viability of products. It is also important to design product packaging with transportation in mind.Many packaging solutions exist to protect goods against transportation hazards, but these stresses induce some modifications to the mechanical properties of these systems by damage accumulation. If the damage accumulation is too important, then the packaging system cannot properly protect the packaged goods.Some damage measurement approaches were proposed in the literature, but they are mainly based on continuous acceleration recording 1 or on the consideration of a particular parameter or phenomenon of a packaging system. 2,3 This method uses continuous signal recording. The most widely used method to estimate damage from a continuous recording is based on the study of the evolution of the mechanical properties by accumulating the cycle stress. This method uses the Wöhler curves.These curves describe the damage wear evolution of a system by counting the number of stress cycles for a particular magnitude until the cycle breaks. The system mechanical wear evolution knowledge is based on a temporal cycle extraction method, such as Rainflow, for determining the global damage.In transportation studies, power spectrum densities (PSDs) are traditionally used to ...
In packaging science, the study of transport is important in determining the viability of a package/product pair. Many load breaks occur (e.g. handling and storage) along a supply chain. Transport also generates various physical stresses (e.g. shocks, shakes and vibrations). These physical phenomena can be recorded using a variety of customized sensors (e.g. tri-axial accelerometers, temperature sensors and pressure sensors). This study focuses on a transport phase that has not been studied in depth to date. Transportation operations on tarmacs include many handling and transportation machines, which are characterized by typical constraints that are often more stringent than airlift phase constraints. For comparison, acceleration distributions were estimated and analysed for the tarmac phase and road phase. Severity indicators were calculated based on existing methods. The second part of this study addresses the study of shakes. The shake distributions at 90 and 95% were another indicator of the shakes' severity and probability of occurrence. These elements allow us to characterize the impact of the tarmac area during air transport.
Nowadays, product protection during transportation has become essential as import-export is increasing drastically. As a result, wrapping is used to stabilize and protect the goods and must be performed properly. The most commonly used wrapping material is the linear low-density polyethylene (LLDPE), either manually or through a mechanical equipment. This study will focus on the adequation of stretch film standard to wrapping and transport applications. Both manual and mechanical films were analysed. The anisotropy of the materials was investigated. Characterization of the material was focused on tensile properties, elastic recovery, permanent deformation and stress retention in order to correspond to pallet wrapping applications. It was found that both materials showed anisotropic behaviours. Standard testing conditions were found to not be described properly transport wrapping applications. Relaxation time and extension speed were found to significantly affect hysteresis properties.
The usual method to simulate vertical vibrations generated by road transport in laboratory is to use the average power spectral density. With this method, the distribution of the acceleration levels throughout the test is a Gaussian which does not conform to the reality of a transport. This study proposes an improvement of the classical method; this improvement permits to simulate the power spectral density and the distribution of acceleration levels by using a conventional device. The main idea of this method is to decompose the distribution of an actual road transport by using a sum of weighted Gaussians. Then, we apply the power spectral density with the root mean square acceleration (grms) level and duration corresponding to each Gaussian calculated from the weighted sum. We show that the weighting coefficients correspond to the time fraction of the test. Over the total duration of the test, we then retrieve the acceleration levels distribution of the actual transport. This new test method is experimentally validated with 2 examples of actual transports.
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