Traditional gear weight optimization methods consider gear tooth number, module, face width or other dimension parameters of gear as design variables. However, due to the complicated form and geometric features peculi...Traditional gear weight optimization methods consider gear tooth number, module, face width or other dimension parameters of gear as design variables. However, due to the complicated form and geometric features peculiar to the gear, there will be large amounts of design parameters in gear design, and the influences of gear parameters changing on gear trains, transmission system and the whole equipment have to be taken into account, which increases the complexity of optimization problem. This paper puts forward to apply functionally graded materials(FGMs) to gears and then conduct the optimization. According to the force situation of gears, the material distribution form of FGM gears is determined. Then based on the performance parameters analysis of FGMs and the practical working demands for gears, a multi-objective optimization model is formed. Finally by using the goal driven optimization(GDO) method, the optimal material distribution is achieved, which makes gear weight and the maximum deformation be minimum and the maximum bending stress do not exceed the allowable stress. As an example, the applying of FGM to automotive transmission gear is conducted to illustrate the optimization design process and the result shows that under the condition of keeping the normal working performance of gear, the method achieves in greatly reducing the gear weight. This research proposes a FGM gears design method that is able to largely reduce the weight of gears by optimizing the microscopic material parameters instead of changing the macroscopic dimension parameters of gears, which reduces the complexity of gear weight optimization problem.展开更多
Light-weight,high-strength metamaterials with excellent specific energy absorption(SEA)capabilities are sig-nificant for aerospace and automobile.The SEA of metamaterials largely depends on the material and structural...Light-weight,high-strength metamaterials with excellent specific energy absorption(SEA)capabilities are sig-nificant for aerospace and automobile.The SEA of metamaterials largely depends on the material and structural design.Herein,inspired by the superior impact resistance of pomelo peel for protecting the pulp and the elevated SEA ability of a functionally graded structure,a graded bionic polyhedron metamaterial(GBPM)was designed and realized by 3D printing using a soft material(photosensitive resin)and a hard material(Ti-6Al-4V).Guided by compression tests and numerical simulations,the elevated SEA ability was independent of the materials.The fluctuation region appeared in hard-material-fabricated bionic polyhedron metamaterial(BPMs)and was absent in soft-material-fabricated BPMs in the stress-strain curves,resulting in the growth rate of the SEA value of the soft-material-fabricated GBPM being enhanced by 5.9 times compared with that of the hard-material-fabricated GBPM.The SEA values of soft-and hard-material-fabricated GBPM were 1.89 and 44.16 J/g,which exceed those of most soft-and hard-material-fabricated metamaterials reported in previous studies.These findings can guide the design of metamaterials with high energy absorption to resist external impacts.展开更多
What is spinal concussion?Spinal cord concussion is a variant of mild spinal cord injury,clinically designated as transient paraplegia or neurapraxia,and characterized by variable degrees of sensory impairment and mo...What is spinal concussion?Spinal cord concussion is a variant of mild spinal cord injury,clinically designated as transient paraplegia or neurapraxia,and characterized by variable degrees of sensory impairment and motor weakness that typically resolve within 24–72 hours without permanent deficits(Del Bigio and Johnson,1989;Zwimpfer and Bernstein,1990;Torg et al.,1997).展开更多
基金Supported by National Hi-tech Research and Development Program of China(863 Program,Grant No.2015AA042505)
文摘Traditional gear weight optimization methods consider gear tooth number, module, face width or other dimension parameters of gear as design variables. However, due to the complicated form and geometric features peculiar to the gear, there will be large amounts of design parameters in gear design, and the influences of gear parameters changing on gear trains, transmission system and the whole equipment have to be taken into account, which increases the complexity of optimization problem. This paper puts forward to apply functionally graded materials(FGMs) to gears and then conduct the optimization. According to the force situation of gears, the material distribution form of FGM gears is determined. Then based on the performance parameters analysis of FGMs and the practical working demands for gears, a multi-objective optimization model is formed. Finally by using the goal driven optimization(GDO) method, the optimal material distribution is achieved, which makes gear weight and the maximum deformation be minimum and the maximum bending stress do not exceed the allowable stress. As an example, the applying of FGM to automotive transmission gear is conducted to illustrate the optimization design process and the result shows that under the condition of keeping the normal working performance of gear, the method achieves in greatly reducing the gear weight. This research proposes a FGM gears design method that is able to largely reduce the weight of gears by optimizing the microscopic material parameters instead of changing the macroscopic dimension parameters of gears, which reduces the complexity of gear weight optimization problem.
基金supported by Guangdong Provincial Key-Area Research and Development Program of China(Grant No.2020B090923001)National Natural Science Foundation of China(Grant Nos.51922044,52205358)Central Universities Funda-mental Research Funds of China(Grant No.HUST:2022JYCXJJ021).
文摘Light-weight,high-strength metamaterials with excellent specific energy absorption(SEA)capabilities are sig-nificant for aerospace and automobile.The SEA of metamaterials largely depends on the material and structural design.Herein,inspired by the superior impact resistance of pomelo peel for protecting the pulp and the elevated SEA ability of a functionally graded structure,a graded bionic polyhedron metamaterial(GBPM)was designed and realized by 3D printing using a soft material(photosensitive resin)and a hard material(Ti-6Al-4V).Guided by compression tests and numerical simulations,the elevated SEA ability was independent of the materials.The fluctuation region appeared in hard-material-fabricated bionic polyhedron metamaterial(BPMs)and was absent in soft-material-fabricated BPMs in the stress-strain curves,resulting in the growth rate of the SEA value of the soft-material-fabricated GBPM being enhanced by 5.9 times compared with that of the hard-material-fabricated GBPM.The SEA values of soft-and hard-material-fabricated GBPM were 1.89 and 44.16 J/g,which exceed those of most soft-and hard-material-fabricated metamaterials reported in previous studies.These findings can guide the design of metamaterials with high energy absorption to resist external impacts.
基金supported by NIH PO1 NS055976Craig H.Neilsen Foundation
文摘What is spinal concussion?Spinal cord concussion is a variant of mild spinal cord injury,clinically designated as transient paraplegia or neurapraxia,and characterized by variable degrees of sensory impairment and motor weakness that typically resolve within 24–72 hours without permanent deficits(Del Bigio and Johnson,1989;Zwimpfer and Bernstein,1990;Torg et al.,1997).