Browsing by Author "Fadiji, Tobi Samuel"

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    Mechanical design and performance evaluation of ventilated packages
    (Stellenbosch : Stellenbosch University, 2015-03) Fadiji, Tobi Samuel; Coetzee, Corne; Opara, Umezuruike Linus; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: Ventilated corrugated paperboard (VCP) packages are used extensively in the fruit industry to minimize damage and facilitate airflow around the produce to maintain the cold chain. In the postharvest journey of fruit, these packages are subjected to a multitude of dynamic and static forces such as impacts, compression and vibration which results in damage and reduces the quality of the packaged fruit. This thesis aims to develop a validated finite element analysis (FEA) model to assist in the mechanical design of VCP packages. Another aim is to evaluate the performance of apple fruit packaging by investigating the resistance of the packages to the forces they are subjected to during postharvest handling, and characterising the bruise susceptibility of the fruit inside the packages. A validated FEA model was used to study the effect of vent height, shape, orientation, number of vents and area on the strength of the packages. Results showed that incidence and susceptibility to bruise damage of the apple fruit was affected by package design when subjected to impact, compression and vibration loads. Bruise damage increased with an increase in drop height with a significant increase of about 50% when the package drop height increased from 30 cm to 50 cm. The bottom layer of the package was more susceptible to bruise damage when subjected to impact load. Under vibration load, the highest bruise damage was observed at a frequency of 12 Hz, where the greatest packaging transmissibility of 243% occurred. The top layers of the package were prone to bruise damage under vibration load. Compression strength of the packages reduced by about 16% when environmental condition was changed from standard condition (23℃ and 50% RH) to refrigerated condition (0℃ and 90% RH). Under compression load, irrespective of package design, the highest and lowest bruise incidence of bruise damage occurred at the top and bottom layers of the package, respectively. The incipient buckling load of the package obtained from the FEA model could accurately predict the experimental value obtained during the compression test. The difference between the numerical and experimental values was within 9%. Increasing the vent area from 2 to 7% reduced the buckling load with about 12%. Vent number, orientation, and shape affected the buckling load of the packages. Rectangular vent holes better retained the strength of the packages compared to circular vent holes. Vent height significantly reduced the buckling load of the packages. The results obtained from this research provided practical guidelines for improving future design of packages for the South African fruit industry.
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    Numerical and experimental performance evaluation of ventilated packages
    (Stellenbosch : Stellenbosch University, 2019-04) Fadiji, Tobi Samuel; Coetzee, Corne; Opara, Umezuruike Linus; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering (CRSES)
    ENGLISH ABSTRACT: Packaging serves a crucial role in reducing postharvest losses, particularly in the handling of fresh horticultural produce, and would be difficult to do without. Packaging protects the produce against mechanical hazards such as compression, impact, drop or vibration during distribution, ensuring its safe delivery to the consumers in a sound condition, at a minimum cost. Ventilated corrugated paperboard (VCP) packaging is being used extensively for handling fresh produce due to its capability to promote uniform and rapid cooling. However, the presence of ventilation openings jeopardises the strength of the package which could result in produce damage. As it is of utmost importance to ensure that the produce reaches its final destination without damage, continuous improvement in the package strength is paramount. Hence, this project aimed to gain a better understanding of the structural performance of VCP packaging to enhance the development of better and improved package designs. Firstly, a validated finite element analysis (FEA) model was developed to study the structural performance of an existing VCP package. This model incorporated some geometrical nonlinearities of the package. Paper and paperboard characterisations were done to determine the tensile properties, edge compression resistance and flat crush resistance. The tensile properties were used as input parameters in the model. The model was able to predict the compression strength of the package, and showed good agreement with experimental results, within 10%. Package liner thickness had a linear relationship with the compression strength. The stress in the package was found to be concentrated and a maximum at the corners. Subsequently, the FEA model was used to assess the strength of different package designs with emphasis on the influence of different geometrical configuration. The model was validated with experimental results. Increasing the vent area of the package reduced its compression strength. Packages manufactured with double-walled corrugated board performed better than single-walled board irrespective of the design, with the difference in strength as high as 72%. This study showed the importance of knowing the paperboard properties in the design of a package to improve its strength. Furthermore, the creep behaviour of different package designs was evaluated, and results showed load and environment conditions as significant factors affecting the creep rate. Increasing the applied load and relative humidity (RH) as well as reducing the temperature, accelerated the creep rate of the package. Also, package configuration also had a significant effect on the creep rate. Finally, to understand the deformation phenomenon of packages subjected to compression load, the displacement field of different designs was studied using digital image correlation (DIC), a full-field non-contact optical measurement technique. Findings showed that the distribution of the package displacement is largely heterogeneous. The displacement field in the out-of-plane direction was the largest while that in the horizontal direction was the smallest. Buckling was found to be a predominant phenomenon occurring at the centre of the package panels. Overall, this study provided empirical and numerical evidence for the design of improved packages, balancing the need for adequate structural performance and optimum cooling functionalities of the package.