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Browsing by Author "Molina Montoya, Eduardo"

Now showing 1 - 5 of 5
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    Evaluation of Unit Load Stability Under Dynamic Forklift Handling Conditions
    Capizzi, Seth (Virginia Tech, 2024-06-12)
    A vast amount of goods and products are transported in bulk as palletized unit loads, where the pallet is the base of the unit load. Material handling systems represent the physical environment in which unit loads are transported through supply chains. Material handling systems include different transportation modes and storage conditions, many of which are well researched. While industrial forklifts are paramount to material handling systems, the physical effect they have on load systems is not well understood. The weight of the unit load causes the pallets to deflect, and previous research has revealed that forklift vibration amplifies pallet deflection. The effects of forklift vibration on pallet deflection are not considered in international standards used to determine pallet load capacities. Standards such as ISO 8611 and ASTM D1185 provide deflection limits that are used to determine pallet load capacities, yet there is a lack of understanding and justification on these deflection limits related to forklift support conditions. A comprehensive understanding of the effects of forklift vibration on unit load performance is necessary to produce accurate and safe load capacity ratings. In this research, two studies were completed to gain further understanding on unit load performance and stability in forklift handling conditions. The first study evaluated pallet deflection and unit load stability of unbound unit loads designed with a 20 mm. performance limit (ISO 8611, 2011). Common forklift handling factors were investigated and included fork tine angle (level and 4-degree incline) and pallet orientation (racked across the width and across the length). The results showed that the dynamic environment of forklift handling created unstable unit loads. The second study of this research project investigated unit load performance against unit load design factors of load capacity (500 lbs., 750 lbs., 900 lbs.) and box size (8 in., 12 in., 16 in.). The results showed that unit load instability occurred at all load levels and all box sizes. Additionally, an increase in box size decreased load bridging for unit loads under fork tine support conditions. Furthermore, the time to instability was used to calculate projected forklift travel distances that can be used to further optimize material handling systems.
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    Finite Element Modeling of Plastic Pails when Interacting with Wooden Pallets
    Alvarez Valverde, Mary Paz (Virginia Tech, 2024-06-04)
    The physical supply chain relies on three components to transport products: the pallet, the package, and unit load stabilizers. The interactions between these three components can be investigated to understand the relationship between them to find potential optimization strategies. The relationship between corrugated boxes and pallets have been previously investigated and have found that the relationship can be used to reduce the quantity of material used in unit loads and can also reduce the cost per unit load if the package and pallet are designed using a systems approach. Although corrugated boxes are a common form of packaging, plastic pails are also used in packaging for liquids and powders, but they have not been previously investigated. To understand the interactions between the wooden pallet and plastic pails, physical tests were conducted and then used to create and validate a finite element model. The experiments were carried out in three phases. The first phase included physical testing of plastic pails where the deckboard gap and overhang support conditions would be isolated by using a rigid deckboard scenario. The second phase also used physical tests to investigate plastic pails but instead used flexible deckboards and used an overhang support condition and a 3.5 in. gap support condition. The third phase of experiments would develop and validate a finite element model to further understand the impact of deckboard gaps and overhang depending on the location of the gap. Previous physical experiments were used to create and validate the finite element model. Nonlinear eigen buckling analysis was used to model the plastic pail buckling failure that was seen in physical testing. The model based on the physical experiments was able to predict the behavior of the plastic pail within a range of 5-12% variation with higher variation being introduced when the flexible deckboard is introduced. The finite element model was then used to model a range of deckboard gap sizes and overhang sizes as well as different locations for deckboard gaps. The results of the experiments indicate that the percent of pail perimeter that is supported directly on the pallet impacts the compression strength of the plastic pail. Decreasing the quantity of support decreases the compression strength of the plastic pail in a linear pattern. The location of the deckboard gap also influenced the compression strength because of the quantity of pail being supported being altered. The results of the experiments can be used by industry members to provide guidelines on unit load design to prevent plastic pail failure. Industry members can also use the results as a baseline investigation and further the finite element model by incorporating their own plastic pail design.
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    Investigation of Pallet Stacking Pattern on Unit Load Bridging
    Molina Montoya, Eduardo (Virginia Tech, 2017-05-04)
    The optimization of pallet design in today’s competitive supply chain is imperative to reduce costs and improve sustainability. With over two billion pallets in circulation in the United States, most packaged products are handled using unit loads and the interactions between the unit load components are not being considered in the pallet design process. This study aims to investigate the effect of the interlocking of layers and the pallet stacking patterns on pallet bending. This effect is part of a greater encompassing observed behavior known as load bridging, where a redistribution of the stresses on the pallet dependent on the characteristics of the load is generated. The bending of the unit load was measured under four common support conditions, warehouse racked across the width and length, fork tine support across the width and floor stacking. Five different pallet stacking patterns were then analyzed, comparing different interlocking levels, from column stacking to fully interlocking. It was identified that interlocking the layers causes a reduction in pallet deflection of up to 53% versus column stacking, and is more significant on lower stiffness pallets. The stacking patterns and interlocking levels also presented an effect on pallet deflection, albeit only for very low stiffness pallets when supported on its weakest components. A relationship between the observed results and a ratio of load and pallet stiffness was conducted, suggesting that when the load on the pallet is not significantly high in relation to the stiffness, load bridging won’t be observed. These results provide a guideline on improving pallet design and help furthering the understanding of the load bridging effect.
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    Modeling of the fundamental mechanical interactions of unit load components during warehouse racking storage
    Molina Montoya, Eduardo (Virginia Tech, 2021-02-04)
    The global supply chain has been built on the material handling capabilities provided by the use of pallets and corrugated boxes. Current pallet design methodologies frequently underestimate the load carrying capacity of pallets by assuming they will only carry uniformly distributed, flexible payloads. But, by considering the effect of various payload characteristics and their interactions during the pallet design process, the structure of pallets can be optimized. This, in turn, will reduce the material consumption required to support the pallet industry. In order to understand the mechanical interactions between stacked boxes and pallet decks, and how these interactions affect the bending moment of pallets, a finite element model was developed and validated. The model developed was two-dimensional, nonlinear and implicitly dynamic. It allowed for evaluations of the effects of different payload configurations on the pallet bending response. The model accurately predicted the deflection of the pallet segment and the movement of the packages for each scenario simulated. The second phase of the study characterized the effects, significant factors, and interactions influencing load bridging on unit loads. It provided a clear understanding of the load bridging effect and how it can be successfully included during the unit load design process. It was concluded that pallet yield strength could be increased by over 60% when accounting for the load bridging effect. To provide a more efficient and cost-effective solution, a surrogate model was developed using a Gaussian Process regression. A detailed analysis of the payloads' effects on pallet deflection was conducted. Four factors were identified as generating significant influence: the number of columns in the unit load, the height of the payload, the friction coefficient of the payload's contact with the pallet deck, and the contact friction between the packages. Additionally, it was identified that complex interactions exist between these significant factors, so they must always be considered.
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