苹果采后加工碰撞损伤影响因素研究

针对苹果在清洗、分级和包装等采后加工过程中损伤率较高的问题,以红富士苹果为试验材料,利用自制的苹果跌落试验台,研究跌落高度、果实质量、碰撞材料对苹果碰撞损伤的影响。通过3因素3水平正交试验,分析试验因素对苹果碰撞损伤体积影响显著性;并通过试验确定苹果在2种碰撞材料下的碰撞损伤临界跌落高度。试验结果表明:影响苹果碰撞损伤体积的因素显著性由高到低依次为跌落高度、碰撞材料、果实质量;3种质量苹果与2种碰撞材料的碰撞损伤临界跌落高度为150 g苹果与普通碳素钢、PE板碰撞损伤临界跌落高度值分别为59.06 mm和70.93 mm;200 g苹果与普通碳素钢、PE板碰撞损伤临界跌落高度值分别为51.70 mm和63.03 mm;250 g苹果与普通碳素钢、PE板碰撞损伤临界跌落高度值分别为41.65 mm和49.88 mm。

Soliton—Like Pulses in Vertical Granular Chain Under Gravity：Particle—Like or Wave—Like

We numerically study the propagation, reflection and collision of soliton-like pulses in the vertical granular chain under gravity. For the pure granular chain system, during the propagation and reflection processes at the fixed end, it behaves like a particle. When it is reflected at the free end, it behaves as neither particle-like nor wave-like. When the strengths of the two colliding soliton-like pulses are close, they collide just like particles. When their strengths are greatly different, they collide just like waves. For the soliton behavior in the collision process, from particle-like to wave-like, there is a critical value for the ratio of the strengths of the two initial pulses. For the two-layer granular chain, if the mass of the grains in the second layer is less than that in the first layer, the soliton-like pulse in the first layer usually excites about soliton-like pulses in the second layer.

Collision performance of bitubular tubes with diaphragms

A numerical study of bitubular tubes with diaphragms compared with single and bitubular tubes subjected to dynamic axial impact force was presented. At first, the energy absorption response of the composite structure under axial loading was analyzed by finite element simulation. The results show that the efficiency of energy absorption can be improved by introducing diaphragms to the double-walled columns. Then, the effect of the amount and location of diaphragms, the shape and the size of the inner tubes, and the thickness of the composite structures were also studied numerically. The collision performance of the composite structure is affected by the deformation of diaphragms, as well as the interaction of outer and inner tube. The non-uniform distribution of diaphragms can improve the energy absorption efficiency of structures for a constant number of diaphragms. The specific energy absorption of the hexagonal inner tube is the highest, followed by the circular, octagonal and square ones.

Collapse behavior evaluation of hybrid thin-walled member by stacking condition

The recent trend of vehicle design aims at crash safety and environmentally-friendly aspect. For the crash safety aspect, the energy absorbing members should absorb collision energy sufficiently but for the environmentally-friendly aspect, the vehicle structure must be light weight in order to improve the fuel efficiency and reduce the tail gas emission. Therefore, the light weight of vehicle must be achieved in a securing safety status of crash. An aluminum or carbon fiber reinforced plastics (CFRP) is representative one of the light-weight materials. Based on the respective collapse behavior of aluminum and CFRP member, the collapse behavior of hybrid thin-walled member was evaluated. The hybrid members were manufactured by wrapping CFRP prepreg sheets outside the aluminum hollow members in the autoclave. Because the CFRP is an anisotropic material whose mechanical properties, such as strength and elasticity, change with its stacking condition, the effects of the stacking condition on the collapse behavior evaluation of the hybrid thin-walled member were tested. The collapse mode and energy absorption capability of the hybrid thin-walled member were analyzed with the change of the fiber orientation angle and interface number.

An Elastic-Plastic Iceberg Material Model Considering Temperature Gradient Effects and its Application to Numerical Study

To simulate the FPSO-iceberg collision process more accurately, an elastic-plastic iceberg material model considering temperature gradient effects is proposed and applied. The model behaves linearly elastic until it reaches the ‘Tsai-Wu’ yield surfaces, which are a series of concentric elliptical curves of different sizes. Decreasing temperature results in a large yield surface. Failure criteria, based on the influence of accumulated plastic strain and hydrostatic pressure, are built into the model. Based on published experimental data on the relationship between depth and temperature in icebergs, three typical iceberg temperature profiles are proposed. According to these, ice elements located at different depths have different temperatures. The model is incorporated into LS-DYNA using a user-defined subroutine and applied to a simulation of FPSO collisions with different types of icebergs. Simulated area-pressure curves are compared with design codes to validate the iceberg model. The influence of iceberg shape and temperature on the collision process is analyzed. It is indicated that FPSO structural damage not only depends on the relative strength between the iceberg and the structure, but also depends on the local shape of the iceberg.