In recent years there has been a very significant increase in parcel delivery shipments all over the world. Moreover, this mode of delivery, in some cases, is facing a very intensive flow of goods, such as in annual festive seasons or, for instance, in situations like COVID-19 when personal purchase of goods is strictly limited in malls. This often means that delivery vehicles operate at almost full capacity, and many same or different kinds of packages are therefore stacked in small delivery vehicles. In this study, we measured and analyzed the vibration levels that occur in smaller stacks of packages in parcel delivery shipments, paying particular attention to those circumstances such as stacking layers and free movement spaces that can affect the vibration in different layers of packages. The goal of this paper was to provide information about the vibration levels that occur in smaller stacks of packages that are not unitized and fixed, as is common in parcel transportation. The recorded vibration events were analyzed in terms of power spectral densities (PSDs) and supplied with statistical data of acceleration events to provide an understanding of the variability of intensity. Based on the results of this study, PSD spectra were developed for various free movement conditions, as well as spectra for each layer in the stacked parcel package shipment. The results showed that the vibration level increases in the stacked load upwards and with an increase of free space of possible movement. The results of this study can be used to simulate the measured vibration conditions in laboratory tests conducted on courier express parcel shipments.

In the last decade, there has been a significant increase in parcel delivery shipments all over the world due to online stores and consumer demand to receive the products in a shorter period of time. It is especially true when situations like COVID-19 limits personal purchases in shopping malls as well as grocery and pharmaceutical stores. This often means that courier operators try to deliver packages utilizing vehicles with racks or shelves, which during the COVID-19 epidemic are not there anymore. This study measured the vertical vibration levels that occur in stacked parcels during express delivery versus the simulation technique in the laboratory. The goal of this paper was to measure and compare the vibration levels between laboratory practice and field transportation. For the measurement a three-layer stacked unit was built to observe the vibration levels on different road conditions in a parcel delivery vehicle and ASTM vibration profile (ASTM International). Then the measured acceleration-time data were analyzed in terms of power spectral densities (PSD) and the presented statistical data provided an understanding of the variability of intensity in different levels in stacked unit. The results showed that the vibration level increases in the stacked load upwards and with worse road conditions, but even in the worst case it did not reach those vibration levels that the laboratory test showed. Moreover, the layers of the stacked unit are in out-of-phase motion in the field, while the stacked unit in the vibration simulation usually is in-phase motion. Results indicate that the proposed vibration simulation does not correlate well with typical field vibration. This is fundamentally true as during a forced vibration created by a single-axis shaker, do not account for additional inputs occurring simultaneously creating an off-balance to the loads and as a result are less severe than simulated conditions. These findings are limited to single axis vibration simulation and unsecured loads.

The unitized loads are the major form of the packed product transportation in logistics, and in most of the cases the packages are fixed to the pallet with straps, stretch film or these combinations to avoid the possible damages of products inside. During transportation various physical events such as vibration affect the product-packaging system. The nature of this vibration between the layers of stacked unit is not fully researched and understood. This paper focuses on the different motion of the layers in the unitized load in the function of the fixing modes using laboratory vibration simulations. Therefore, multiple unitized loads were built from the same quality corrugated paper boxes in three layers with various fixing modes to measure each layer motion separately. To carry out the simulation procedure, acceleration and vibration intensity on each layer was observed under sine and random vibration simulation. The recorded data shows, which layer motion is the most disparate from the excited motion, and which fixing variant causes this difference.