Abstract
The damage characteristics of five layers of Japanese radishes stacked in a triple-wall fiberboard box under a vibration treatment (2～30Hz, 0.6G), which was considered a transport model of a newly developed bulk container, are investigated. The differences in the vibration treatment period (0.5, 3, 5, 10, 20, and 40min) and the position of the Japanese radishes in the stack significantly affected the type and the severity of the damage. Various types of damage, including abrasion, peeling, and bruising of Japanese radishes, are observed differently, depending on the stacking layers. Abrasion and peeling symptoms are found on the upper layers of the stack of the Japanese radishes owing to a non-synchronized movement, whereas bruise symptoms are found on the lower layers. Further, the acceleration transmissibility test of the Japanese radishes against a vibrating table revealed resonant frequencies close to 15Hz in all the layers. The higher the stacking layer, the higher is the acceleration transmissibility. Moreover, the contact stress index obtained from a multipoint pressure sensor revealed that both the maximum and the minimum values at the lower layers are significantly higher than those at the upper layers (maximum value: P＜0.05 (15Hz, 20Hz, and 25Hz are excluded) ; minimum value: P＜0.01). A reduction in the load from the upper layers, caused by the non-synchronized movement, most likely results in lower values of the contact stress index of the Japanese radishes in the middle/upper layers. Overall, it appears that the restriction of the free movement of Japanese radishes in the upper layer without any additional stress facilitates the prevention of damages such as abrasion and peeling. Moreover, we need to find an acceptable stacking height to avoid bruising in the lower layers. Further research on the design of packaging conditions for the actual transport condition will enable us to distribute Japanese radishes by using the newly developed bulk container without any unacceptable damages.
