1977 Volume 39 Issue 3 Pages 343-349
For the purpose of practising a resonable and effective simulated transportation test in the laboratory, vibrating characteristics and in-transit mechanical injury of lettuce filled in carton-boxes and stacked in seven layers were examined. The results were obtained as follows.
1. Transmissibility of acceleration and phase characteristics of the stacked carton-boxes.
(1) Transmissibility of acceleration of carton-boxes was affected by the banding and the location in the stack of carton-boxes.
(2) The maximum transmissibility was obtained at the top carton-box of the seven layers at the frequency of 8Hz for the unbanded and 13Hz for the banded stack of the carton-boxes. The frequency was considered to be resonant.
(3) The effect of banding on decreasing the acceleration in the carton-box was expected at the frequency lower than 10Hz.
(4) Phase difference between oscillating table and carton-boxes changed much due to the frequency, location in the stack and banding practice. The phase difference was minimized by banding at the frequency lower than 10Hz.
2. Transmissibility of acceleration and phase characteristics of lettuce filled in the carton-boxes.
(1) Resonant frequency of lettuce filled in the carton-box was in the vicinity of 28Hz.
(2) High acceleration which occured at the upper part of the stack was prevented by banding at the frequency lower than 10Hz.
(3) Phase difference between lettuce and carton-box was small at the frequency less than 10Hz, then increased with the increase of frequency although it was not affected by banding.
3. Factors affecting the damage of lettuce in the carton-box.
(1) Damage of lettuce, under the multi-stacked cartons, should be considered only at the frequency of about 10Hz.
(2) Lettuce was damaged by a free rotating motion in the-carton-box excited by the resonant frequency.
(3) The relation between G and N was obtained as follows.
G4·17·N=5.32×103
G: acceleration of lettuce in carton-box.
N: repeating number of vibration permissible from the point of marketability.
(4) Damage was reduced by filling the lettuce in the carton-box with cutting butt downward.
