| According to the problems on declining watermelon quality caused by transportation vibration, a new evaluation method was put forward in this paper:the intact watermelon under the natural status was studied by sweep test, modal analysis, vibration test, and the relation between the quality indicators and vibration parameters as well as the mechanism of fracture damage caused by vibration were analyzed. Specific research process and conclusions are as follows:1. The study on vibration characteristics of watermelonSweep test of watermelon was conducted, and vibration acceleration of watermelon was measured, as well as acceleration transmissibility curve was obtained. According to acceleration transmissibility curve, one and two order natural frequencies of watermelon were gotten 35.125Hz and 71.034Hz, respectively. A finite element analysis model of watermelon was established by the finite element method, and modal analysis of watermelon was carried out. The results show:Watermelon 1st order resonance frequency range is 5.491～36.298Hz,2nd order resonance frequency range is 77.511-79.211Hz. Test data and simulation data of Watermelon were compared, which found that there is a good fit, and proved that watermelon finite element model established is meaningful.2. The study on the relation between watermelon quality index and vibration factorWatermelon vibration orthogonal experiment was conducted, and the hardness of and sugar content of watermelon was measured, as well as the correlation between quality indicators and vibration factors (ANOVA) was analyzed, which found that there is significant relationship among the two indicators and vibration frequency, vibration acceleration, packaging ways; A predictive equation (regression analysis) was established between quality indicators and vibration factors; based on damage theory, macro fracture injury were explored and fracture damage distribution table on watermelon was gotten. |
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