Aiming at the problem of large differences in the laying angle and posture of plants cut by the hemp harvester,which is unfavorable for the subsequent picking-up,this paper analyzed the laying process and laying angle...Aiming at the problem of large differences in the laying angle and posture of plants cut by the hemp harvester,which is unfavorable for the subsequent picking-up,this paper analyzed the laying process and laying angles,and built a conveyorplant rigid-flexible coupling model for simulating the laying of hemp plant.Moreover,the operating parameters were tested and optimized based on the central composite design theory,and carried out multi-objective optimization with the minimum laying angle as the response index.Firstly,the formation mechanism of the laying angle of hemp harvester was studied.Secondly,a test was designed with the quadratic orthogonal rotational combination test method,with the data being processed by Design-Expert.A regression mathematical model of the laying angle was built,and the influence of the interactions between factors on the laying angle was analyzed with the response surface method.Furthermore,multi-objective optimization was conducted on the regression model according to the actual production design requirements.As a result,the best combination was obtained,that is,when the forward speed is 0.7 m/s,speed ratio 1.40,and stubble height 95 mm,the minimum laying angle can be obtained,namely 124.9°.The optimization parameters were verified by the simulation and field tests.The simulation test showed that the simulated laying angle is 125.2°,with a relative error of 0.24%from the theoretical value,under the best combination of parameters.The field test showed that the average laying angle of hemp plant is 121.8°,with a relative error of 2.5%from the theoretical value,under the best combination of parameters.The results may provide a reference for the structural improvement and operating parameter control of hemp harvesters.展开更多
The fracture toughness of carbon fiber reinforced epoxy composite(CFRP)was investigated through mode I and mode II shaped fracture system in this paper.A novel polyimide with trifluoromethyl groups and grafted nanosil...The fracture toughness of carbon fiber reinforced epoxy composite(CFRP)was investigated through mode I and mode II shaped fracture system in this paper.A novel polyimide with trifluoromethyl groups and grafted nanosilica were used to modify epoxy resin.Effect of modified resin and unmodified resin on fracture toughness of CFRP was compared and discussed.Lay-up angles and thicknesses effects on fracture toughness of composites were also investigated.The fracture toughness of CFRP was obtained through double cantilever beam(DCB)and end notched flexure(ENF)tests.The results showed that the composites prepared by modified resin exhibited high fracture toughness compared with unmodified composites.The fracture toughness value of mode I increased from 1.83 kJ/m2 to 4.55 kJ/m2.The fracture toughness value of mode II increased from 2.30 kJ/m2 to 6.47 kJ/m2.展开更多
基金supported by the Open Project of the Key Laboratory of Modern Agricultural Equipment and Technology,Ministry of Education of the PRC(Grant No.MAET202107)NSFC(52005274)+1 种基金China Agriculture Research System of MOF and MARA,Agricultural Science and Technology Independent Innovation Fund Project of Jiangsu Province(CX(22)3096)The Agricultural Science and Technology Innovation Program of Chinese Academy of Agricultural Sciences(ASTIP,CAAS).
文摘Aiming at the problem of large differences in the laying angle and posture of plants cut by the hemp harvester,which is unfavorable for the subsequent picking-up,this paper analyzed the laying process and laying angles,and built a conveyorplant rigid-flexible coupling model for simulating the laying of hemp plant.Moreover,the operating parameters were tested and optimized based on the central composite design theory,and carried out multi-objective optimization with the minimum laying angle as the response index.Firstly,the formation mechanism of the laying angle of hemp harvester was studied.Secondly,a test was designed with the quadratic orthogonal rotational combination test method,with the data being processed by Design-Expert.A regression mathematical model of the laying angle was built,and the influence of the interactions between factors on the laying angle was analyzed with the response surface method.Furthermore,multi-objective optimization was conducted on the regression model according to the actual production design requirements.As a result,the best combination was obtained,that is,when the forward speed is 0.7 m/s,speed ratio 1.40,and stubble height 95 mm,the minimum laying angle can be obtained,namely 124.9°.The optimization parameters were verified by the simulation and field tests.The simulation test showed that the simulated laying angle is 125.2°,with a relative error of 0.24%from the theoretical value,under the best combination of parameters.The field test showed that the average laying angle of hemp plant is 121.8°,with a relative error of 2.5%from the theoretical value,under the best combination of parameters.The results may provide a reference for the structural improvement and operating parameter control of hemp harvesters.
基金National Natural Science Foundation of China(No.11802192)Natural Science Foundation of Jiangsu Province,China(No.BK20180244)Nantong Science and Technology Project,China(No.JC2019012)。
文摘The fracture toughness of carbon fiber reinforced epoxy composite(CFRP)was investigated through mode I and mode II shaped fracture system in this paper.A novel polyimide with trifluoromethyl groups and grafted nanosilica were used to modify epoxy resin.Effect of modified resin and unmodified resin on fracture toughness of CFRP was compared and discussed.Lay-up angles and thicknesses effects on fracture toughness of composites were also investigated.The fracture toughness of CFRP was obtained through double cantilever beam(DCB)and end notched flexure(ENF)tests.The results showed that the composites prepared by modified resin exhibited high fracture toughness compared with unmodified composites.The fracture toughness value of mode I increased from 1.83 kJ/m2 to 4.55 kJ/m2.The fracture toughness value of mode II increased from 2.30 kJ/m2 to 6.47 kJ/m2.