Pear fruit is susceptible to bruising from mechanical impact during field harvesting operations and at all stages of postharvest handling.The postharvest shelf life of bruised fruits were shorter,and they softened rap...Pear fruit is susceptible to bruising from mechanical impact during field harvesting operations and at all stages of postharvest handling.The postharvest shelf life of bruised fruits were shorter,and they softened rapidly under cold storage compared with non-bruised samples.Developing strategies for reducing bruising during the supply chain requires an understanding of fruit dynamic behavior to different enforced loadings.Finite Element Method(FEM)is among the best techniques,in terms of accuracy and cost-efficiency,for studying the factors effective in impact-induced bruising.In this research,the drop test of pear sample was simulated using FEM.The simulation was conducted on a 3D solid model of the pear that was created by using non-contact optical scanning technology.This computer-based study aimed to assess the stress and strain distribution patterns within pear generated by collision of the fruit with a flat surface made of different materials.The contact force between two colliding surfaces is also investigated.The simulations were conducted at two different drop orientations and four different impact surfaces.Results showed that,in both drop orientations,the largest and smallest stresses,strains and contact forces were developed in collision with the steel and rubber surfaces,respectively.In general,these parameters were smaller when fruit collided with the surfaces along its horizontal axis than when collided along its vertical axis.Finally,analyses of stress and strain magnitudes showed that simulation stress and strain values were compatible with experiments data.展开更多
The spacer used in gas insulated switchgear(GIS)plays a vital role in its safe operation.The mismatch of mechanical properties between conductor and insulating material in spacers results in stress concentration at th...The spacer used in gas insulated switchgear(GIS)plays a vital role in its safe operation.The mismatch of mechanical properties between conductor and insulating material in spacers results in stress concentration at the interface between them.During a hydrostatic test,mechanical damages are often initiated from the interface.In this paper,the stress between aluminum conductors and epoxy resin is studied by using a simplified coaxial structure specimen.The measurement system and finite element simulation are used to explore the generation of stress and strain during curing and shrinkage.The real-time measurement of strain at the interface shows that the residual strain in the entire process is primarily generated during the cooling stage.Consequently,the temperature and stress/strain distribution at the interface during the cooling stage are further studied,and combined with experiments and simulations.The consistency between the finite element simulation and the experimental measurement results verifies the validity of the simulation method used.The results show that the maximum of the first principal stress generated during the cooling stage of the production process is concentrated on the upper and lower edges of the interface which is critical to the impact of the production quality of the spacer.展开更多
文摘Pear fruit is susceptible to bruising from mechanical impact during field harvesting operations and at all stages of postharvest handling.The postharvest shelf life of bruised fruits were shorter,and they softened rapidly under cold storage compared with non-bruised samples.Developing strategies for reducing bruising during the supply chain requires an understanding of fruit dynamic behavior to different enforced loadings.Finite Element Method(FEM)is among the best techniques,in terms of accuracy and cost-efficiency,for studying the factors effective in impact-induced bruising.In this research,the drop test of pear sample was simulated using FEM.The simulation was conducted on a 3D solid model of the pear that was created by using non-contact optical scanning technology.This computer-based study aimed to assess the stress and strain distribution patterns within pear generated by collision of the fruit with a flat surface made of different materials.The contact force between two colliding surfaces is also investigated.The simulations were conducted at two different drop orientations and four different impact surfaces.Results showed that,in both drop orientations,the largest and smallest stresses,strains and contact forces were developed in collision with the steel and rubber surfaces,respectively.In general,these parameters were smaller when fruit collided with the surfaces along its horizontal axis than when collided along its vertical axis.Finally,analyses of stress and strain magnitudes showed that simulation stress and strain values were compatible with experiments data.
基金supported in part by the National Natural Science Foundation of China(No.51707155)China Postdoctoral Science Foundation(No.2020M673450)。
文摘The spacer used in gas insulated switchgear(GIS)plays a vital role in its safe operation.The mismatch of mechanical properties between conductor and insulating material in spacers results in stress concentration at the interface between them.During a hydrostatic test,mechanical damages are often initiated from the interface.In this paper,the stress between aluminum conductors and epoxy resin is studied by using a simplified coaxial structure specimen.The measurement system and finite element simulation are used to explore the generation of stress and strain during curing and shrinkage.The real-time measurement of strain at the interface shows that the residual strain in the entire process is primarily generated during the cooling stage.Consequently,the temperature and stress/strain distribution at the interface during the cooling stage are further studied,and combined with experiments and simulations.The consistency between the finite element simulation and the experimental measurement results verifies the validity of the simulation method used.The results show that the maximum of the first principal stress generated during the cooling stage of the production process is concentrated on the upper and lower edges of the interface which is critical to the impact of the production quality of the spacer.
