Department of Mechanical and Mechatronic Engineering

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Browsing Department of Mechanical and Mechatronic Engineering by browse.metadata.advisor "Berry, TM"

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    Defining citrus pallet stability and modes of failure: developing tools to make stronger and cheaper cartons.
    (Stellenbosch : Stellenbosch University, 2024-02) Erasmus, NJ; Coetzee, CJ; Berry, TM; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: The export of horticultural produce, especially citrus, is an ever-evolving and dynamic industry with constant regulation changes in terms of carton design and post-harvest management. This dynamic, however, offers opportunities for carton design innovations. Extensive research has been conducted to predict the structural integrity of cartons, using combined analytical-empirical and finite element methods. However, the load acting on a carton, when stacked on a pallet, has not yet been measured and is largely unknown. The numerical models assume that the load is evenly distributed and that the cartons are perfectly aligned. Furthermore, the stability of a stacked pallet under dynamic loading has been investigated for general goods, but not for horticultural produce. This work aimed at developing experimental tools to measure the load distribution acting on individual cartons inside a stacked pallet, as well as the whole pallet stability under dynamic load conditions. The tools include the A15C Load Measurement Device (A15C-LMD) and the Pallet Lateral Acceleration Tester (PLAT). The A15C-LMD was developed to have the same geometric dimensions as a standard A15C citrus carton and was equipped with four load cells. Replacing a carton with this device, allowed for measuring the static and dynamic load distribution acting on cartons at strategic positions in the stack. The PLAT was developed to enable repeatable dynamic testing, as described by EUMOS 40509, which is a standard for pallet stability and safe goods transportation. The dynamic tests simulated the acceleration and deceleration of a truck under normal driving conditions. These two tools were used in unison to quantify the dynamic loading on a carton, as well as the whole pallet stability, for different stacking configurations (standard and brick). The carton load under static conditions for the standard configuration was observed to be evenly distributed across cartons on a single level, with a peak carton load of 1.6 kN. However, the load distribution on a single carton was observed to be asymmetrical with a peak corner load of 0.8 kN. The load distribution for the brick configuration was, however, the inverse of that of the standard configuration. The load distribution across cartons on a single level was uneven with a peak carton load of 3.7 kN, whereas the load distribution on a single carton was evenly distributed with a peak corner load of 1.1 kN. The stability behaviour of the standard configuration was similar to a highly damped system with a peak elastic displacement of 171 mm. The brick configuration behaved more like an under-damped system with a peak elastic displacement of 54 mm. These displacements were well below the limit of 233 mm set by the EUMOS standard. Thus, both pallet stack configurations were deemed stable under a lateral acceleration of 0.5g. The dynamic condition had a significant effect on the carton load for both stack configurations. In the standard configuration, a peak carton load of 3.6 kN and a peak corner load of 1.7 kN were recorded. In the brick configuration, a peak carton load of 3.8 kN and a peak corner load of 1.5 kN were recorded. The strength of a new carton and a used carton from the stack, after being subjected to a dynamic load, was measured in a box compression test (BCT). These strengths were used to introduce two safety factors. The safety factor of the new carton was similar for the standard and brick stack configurations i.e., 2.34 to 2.19. However, the safety factor reduced to 0.91 after being loaded in the standard configuration. The developed tools aided in the quantification of the dynamic carton loading and stacked pallet stability for the different stack configurations. The research contributes towards the future improvement of corrugated carton design.
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    Designing integrated corrugated paperboard packaging systems for enhanced cold treatments.
    (Stellenbosch : Stellenbosch University, 2024-02) Chung, SH; Coetzee, CJ; Berry, TM; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: South Africa is the world's second-largest citrus exporter, and heavily relies on citrus packaging for efficient transportation, protection, and cooling of its produce across the global supply chain. Currently, the South African citrus industry is grappling with stringent phytosanitary cooling regulations, which are exerting considerable pressure on its cold storage infrastructure. The effectiveness of cooling processes is deeply influenced by the design of packaging systems. However, there is a notable lack of a simple, systematic approach to characterising these packaging designs. In response to this challenge, this study introduces a robust method to evaluate airflow resistance in fruit packaging systems, incorporating a circuit model perspective. This innovative approach, which assesses both the overall system and its individual components, offers a practical tool for industry stakeholders. It allows for the effective evaluation and comparison of new packaging designs against existing on(S and provides detailed insights into the impact of each component, within the packaging. This circuit model-based method meets the citrus industry's need for a measurable parameter that helps select market-specific packaging. This packaging must not only adhere to the unique phytosanitary and cold treatment standards for export but also alleviate the stress on the limited cold storage facilities. The circuitry model approach was applied using numerical simulations on a conceptual basis and validated using experimental data. The process then followed experimental characterisations. A survey of the industry was performed, whereafter the pallet stack is described in terms of its ventilation to capture the effect of changing the design quantitatively and resistance to airflow. New carton designs were recommended based on their lower resistance to airflow values, which would allow fruit to cool faster, and increase the throughput of the fruit. It was found that the circuitry model could be adequately used to predict the performance of a full pallet based on the comprised components, such as using the resistance of a layer of the pallet stack. This innovative method could be used in the future to rapidly develop new designs that could optimise the performance testing, and performance of a pallet stack in terms of its resistance to airflow (RTA). The RTA was found to be a good metric for which the standardisation of the performance of pallet stacks using common packaging designs could be found. In addition, the RTA was found to be favourable in terms of the South African context of providing fruit that meet quality and phytosanitary expectations for export markets. The study thus provides an initial performance baseline for the industry's two most commonly exported carton designs, with respect to their components and the whole pallet stack.