Dynamic crushing behaviors and enhanced energy absorption of bio-inspired hierarchical honeycombs with different topologies

In order to pursue good crushing load uniformity and enchance energy absorption efficiency of conventional honeycombs, a kind of bio-inspired hierarchical honeycomb model is proposed by mimicking the arched crab shell structures. Three bio-inspired hierarchical honeycombs(BHHs) with different topologies are designed by replacing each vertex of square honeycombs with smaller arc-shaped structures. The effects of hierarchical topologies and multi-material layout on in-plane dynamic crushings and absorbed-energy capacities of the BHHs are explored based on the explicit finite element(FE) analysis.Different deformation modes can be observed from the BHHs, which mainly depend upon hierarchical topologies and impact velocities. According to energy efficiency method and one-dimensional(1D) shock theory, calculation formulas of densification strains and plateau stresses for the BHHs are derived to characterize the dynamic bearing capacity, which is consistent well with FE results. Compared with conventional honeycombs, the crushing load efficiency and energy absorption capacity of the BHHs can be improved by changing the proper hierarchical topology and multi-material layout. These researches will provide theoretical guidance for innovative design and dynamic response performance controllability of honeycombs.

Operation analysis and parameter optimization of the conveying device for uniform crushed straw throwing and seed-sowing machines

Uniform crushed straw throwing and seed-sowing machines can achieve the processes of straw chopping,straw transport,sowing,fertilization,and straw mulching at the same time,which is widely used in many areas of China.Conveying device is one of the important components used to convey,elevate and throw straw.However,the problems of high power consumption and congestion affect the promotion of the machine.Therefore,the conveying device of uniform crushed straw throwing and seed-sowing machine was analyzed in order to determine its device operation mechanism.Kinematic and dynamic analyses of particles of crushed rice straw during lifting and dispersion are used to develop a flexible-body model of rod-shaped and agglomerate-shaped crushed straw and a coupling model including the mechanical structure of the device.By integrating computational fluid dynamics and the discrete element method,the gas-solid coupling theory in numerical simulations and motion analysis of crushed straw particles is used to determine how the flow field and motion characteristics affect the conveying performance.Besides,regression equations to describe the relationships between the factors and each assessment index were established by using the regression analysis and response surface analysis with the software Design-Expert.The effect of throwing blade speed X_(1),conveying volume of crushed straw X_(2),and pipeline diameter X_(3) on the throwing speed of crushed straw Y_(1) and specific power consumption Y2 were investigated.The highest throwing speed of crushed straw and lowest specific power consumption are the optimization goal.The results of optimization showed that the predict the best optimal parameters were 2000 r/min throwing blade rotational speed,1.4 kg/s conveying volume,and 220 mm pipeline diameter,the planter achieved a throwing speed of 12.2 m/s and specific power consumption of 9179 m^(2)/s^(2).And then a field test verification was conducted.The planter achieved a throwing speed 12.4 m/s and specific power consumption 9070 m^(2)/s^(2) while selecting the best optimal parameters.Thus,the optimal parameters can provide a high-performance operation and satisfy the actual operation requirements The results provide a theoretical basis and data support for seeding technology innovation and equipment optimization to ensure uniform crushed straw throwing in dense rice stubble fields.