Research On Mechanical Bruising And Protection Mechanism Of Typical Fruits

During the course of store and transport, fruits will suffer vibration, colliding, impact, static compressive and extrusion. These load could lead to mechanical bruising of fruits. This paper focuses on the creep state and multiple-impacts state with low energy of apple and pear. Besides, through the above-mentioned results, a new packaging method was proposed.As a typical viscoelastic objects, for reducing the damage during transportation and supplying basis of package design, research the creep state of fruits is very important. This paper focuses on the construction of fractional Kelvin model about the creep state of apple samples and pear samples in accordance of fractional order derivative. The result indicates fractional Kelvin model can characterize the situation of creep in apple samples and pear samples for a long time with a comparatively few of parameters.For the test of multiple-impacts, an instrumented pendulum was designed. For suitable many kinds of fruits, this instrumented pendulum has numbers of adjustable structures. And comparing with the accelerometer and rebound height of pendulously impact and free drop, found that the pendulously impact is similar to free drop.During the course of store and transport, fruits may suffer multiple-impacts. The relationship between fruits' mechanical characteristics (accelerometer, rebound height, absorbed energy accumulation) and the number of impact was discussed and the dynamic nonlinear constitutive model was established based on the experiment in which same contact areas on apples and pears were repeated impacted below the level of critical bruising drop height under single impacts. The results showed that the accelerometer, rebound height, bruise rate, cumulative absorbed energy all increased along with an growth in number of impact. But those increases gradually decreased and finally remained at some certain constant values. It also showed that the test results was great agreed with dynamic theoretical model which can ideally determine mechanical characteristics of apples and pears under multiple-impacts with low energy.Through the above-mentioned results, a new packing method was proposed. This paper analyzed the absorbed energy state under multiple-impacts with low energy of A-flute corrugated board and apples which were packed by the above-mentioned corrugated board. The absorbed energy models of the corrugated board and package system were established and the cumulative absorbed energy of packed apples was calculated too. Comparing with the bruise threshold value of apples under multiple-impacts with low energy, the bruise rates of packed apples were predicted. Besides, a new packaging method of fruits whose mechanical characteristics are similar to apples was proposed.