河套蜜瓜静载蠕变特性的试验研究

Creep properties of Hetao muskmelon under static loading

为了解决河套蜜瓜储运过程中因承载造成的蠕变损伤而使果实品质下降的问题、了解河套蜜瓜静载蠕变特性,该文利用虚拟样机技术建立蠕变仿真模型、获得蠕变特性参数及本构方程并对影响因素进行了分析研究。结果表明,河套蜜瓜果实的硬度对蠕变变形恢复量、永久变形量及蠕变速度均有明显影响,温度对永久变形量、蠕变速度有明显影响,载荷对瞬时变形和蠕变速度有明显影响。低温储运时瞬时变形不会随成熟度提高而持续增加,而较高温储运时则相反。因变形恢复量受温度变化影响不明显,为减少永久变形对果实造成的蠕变损伤,针对成熟度较高的果实,应采取低温减轻重压的储运方式。针对成熟度较低的果实,从储运的经济性考虑可适当提高储运温度,但需减轻承重,以免蠕变变形持续发生。

The virtual prototyping technology on the platform of Automatic Dynamic Analysis of Mechanical System （ADAMS） software was applied combining with the experimental results to set up a simulated creep model and constitutive equation in order to solve the problem of creep damage and quality decline of Hetao muskmelon under static loading during postharvest storage and transportation. The creep parameters, such as instantaneous rigidity coefficient μ1, delay rigidity coefficient μ2, viscoce coefficient ηl and η2, and relay time Trel were all obtained through running the simulated creep model. The results show that the stiffness of fruit significantly affectes recovery of creep deformation, residual deformation and deforming rate. Temperature significantly affectes residual deformation and deforming rate, and static load significantly affectes instantaneous deformation and deforming rate. The results also indicate that there is not a continuous increase in instantaneous deformation with the increase of maturity of the fruits under low temperature but there is a continuous increase under high temperature. It is suggested that both low temperature and less loading should be taken during storage and transportation for the mature fruits in order to reduce the creep damage due to residual deformation. Either proper high temperature （such as room temperature） may be adapted for the less mature fruits out of an economical view, or less loading should be taken to avoid a continuous creep deformation during storage and transportation.