Simulated In-transit Vibration Damage to Watermelons

Vibration generated by vehicles during road transport has an important effect on the agricultural products damage process, particularly vegetable and fruit. Modulus of elasticity is one of the most important mechanical properties of fruits and its variation can be described as one of the damage criteria during transportation. This research was conducted to evaluate the effects of vibration parameters (frequency, acceleration and duration) and fruit position in the bin, on watermelon damage. At first, vibration frequency and acceleration were measured on the different points of a truck-bed in order to obtain the range of vibration frequency and acceleration distribution during transportation. Second, a laboratory vibrator was used to obtain some factors influencing damage during watermelons transportation. The damage was described as a difference in the modulus of elasticity of the watermelon (flesh and hull) before and after the test. According to the results measured on the truck-bed, the vibration frequency mean values were ۷.۵۰ Hz and ۱۳.۰ Hz for ۵-۱۰ Hz and ۱۰-۱۵ Hz frequency intervals, respectively. Furthermore, vibration acceleration mean values were ۰.۳۰ g and ۰.۷۰ g for ۰.۲۵-۰.۵۰ g and ۰.۵۰-۰.۷۵ g intervals, respectively. Vibration frequency and acceleration mean values were used for vibration simulation. Vibration durations were ۳۰ and ۶۰ minutes and damage was measured for watermelons at the top, middle and bottom positions in the bin. Laboratory studies indicated that, vibration frequency, vibration acceleration, vibration duration, and fruit position, which were taken into consideration as controlled variable parameters, significantly affected the damage (P< ۰.۰۱). Damage to the watermelon flesh was higher than watermelon hull. Vibration with a frequency of ۷.۵ Hz, acceleration of ۰.۷۰ g, and duration of ۶۰ minutes caused higher damage levels. Fruits located at the top of the bin showed more damage than those in middle and bottom positions (P< ۰.۰۵).

کلیدواژه ها:

Acceleration ، Frequency ، Mechanical damage ، Modulus of elasticity ، Vibration ، Watermelon