Mechanical design and performance evaluation of ventilated packages

Fadiji, Tobi Samuel (2015-03)

Thesis (MEng)--Stellenbosch University, 2015.

Thesis

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.

AFRIKAANSE OPSOMMING: Geventileerde geriffelde kartonverpakkingsakke (ventilated corrugated paperboard (VCP)) word algemeen in die vrugtebedryf gebruik om skade aan die vrugte te beperk en lugvloei tussen die vrugte te fasiliteer asook die koue ketting te handhaaf. In die vrugte se reis vandat dit geoes is, word hierdie sakke onderwerp aan verskeie dinamiese en statiese kragte, soos impak, samedrukking en vibrasie, wat lei tot skade en sodoende word die kwaliteit van die verpakte vrugte verlaag. Hierdie tesis het ten doel om ’n beproefde/geldige eindige element analise (EEA) model te ontwikkel om te help in die meganiese ontwerp van die sakke. Nog ’n doel van die tesis is om die doeltreffendheid van appel-vrug verpakking te bepaal deur die weerstand van die sakke gedurende die tyd na die oes te ondersoek, en ook die moontlikheid van kneusing binne die verpakking te bepaal. ’n Geldige EEA model is gebruik om die effek van luggat-hoogte, vorm, oriëntasie, getal luggate en area op die sterkte van die sakke. Resultate het gewys dat raakpunte en vatbaarheid vir kneusing van die vrug geaffekteer is deur die ontwerp van die sakke wanneer dit onderwerp word aan impak, samedrukking en vibrasie-kragte. Daar was meer kneusing met ’n toename in val-hoogte, en die kneusing het noemenswaardig toegeneem (rondom 50%) toe die val-hoogte verhoog is van 30 cm na 50 cm. Die onderste laag van die verpakking is meer vatbaar vir kneusing as dit onderwerp word aan impak. Die meeste kneusing, met vibrasie-kragte, is waargeneem by ’n frekwensie van 12 Hz, met die hoogste verpakkings-oordraagbaarheid van 243% wat waargeneem is. Die boonste lae van die verpakking was meer vatbaar vir kneusing met vibrasie-kragte. Samedrukking-sterkte van die verpakking is met ongeveer 16% verlaag toe die omgewingsfaktore verander is van standaardtoestand (23℃ and 50% RH) na verkoelde toestand (0℃ and 90% RH). Onder samedrukkingskrag het die hoogste en laagste voorkoms van kneusing onderskeidelik voorgekom op die boonste en onderste lae van die verpakking, ongeag die ontwerp van die verpakking. Die aanvanklike buigingslading van die verpakking soos waargeneem in die EEA model kon die eksperimentele waarde akkuraat voorspel soos gesien in die samedrukkingstoets. Die verskil tussen die numeriese en eksperimentele waardes was nie meer as 9% nie. Deur die luggat groter te maak met tussen 2 en 7% is die buigingslading verlaag met sowat 12%. Die hoeveelheid luggate, oriëntasie en vorm affekteer die buigingslading van die verpakking. Reghoekige luggate het beter vorm behou as sirkelvormige luggate. Die hoogte van die luggate het die buigingslading noemenswaardig verminder. Die resultate verkry uit hierdie navorsing bied praktiese riglyne vir die verbetering van toekomstige ontwerpe van verpakkings vir die Suid-Afrikaanse vrugte-industrie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/96640
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