With the combination of 3D printing and electroplating technique,metal-coated resin lattice is a viable way to achieve lightweight design with desirable responses.However,due to high structural complexity,mechanical a...With the combination of 3D printing and electroplating technique,metal-coated resin lattice is a viable way to achieve lightweight design with desirable responses.However,due to high structural complexity,mechanical analysis of the macroscopic lattice structure demands high experimental or numerical costs.To efficiently investigate the mechanical behaviors of such structure,in this paper a multiscale numerical method is proposed to study the effective properties of the metal-coated Body-Centered-Cubic(BCC)lattices.Unlike studies of a similar kind in which the effective parameters can be predicted from a single unit cell model,it is noticed that the size effect of representative volume element(RVE)is severe and an insensitive prediction can be only obtained from models containing multiple-unit-cells.To this end,the paper determines the minimum number of unit cells in single RVE.Based on the proposed method that is validated through the experimental comparison,parametric studies are conducted to estimate the impact of strut diameter and coating film thickness on structural responses.It is shown that the increase of volume fraction may improve the elastic modulus and specific modulus remarkably.In contrast,the increase of thickness of coating film only leads to monotonously increased elastic modulus.For this reason,there should be an optimal coating film thickness for the specific modulus of the lattice structure.This work provides an effective method for evaluating structural mechanical properties via the mesoscopic model.展开更多
Effects of densification of poplar wood（Populus nigra） impregnated with nano-aluminum oxide（NA） and pre-treated with water vapor for 4 and 6 h were investigated in the present study. Physical and mechanical proper...Effects of densification of poplar wood（Populus nigra） impregnated with nano-aluminum oxide（NA） and pre-treated with water vapor for 4 and 6 h were investigated in the present study. Physical and mechanical properties of treated poplar wood were measured according to the ASTM D-143 standard specifications, and then compared with the untreated specimens. Results showed significant improvement in all properties as a result of densification. A 4-h vapor pre-treatment improved effects on both physical and mechanical properties. When the duration of vapor-treatment increased to 6 h, wood polymers degraded to the extent that the improvements due to the vapor pre-treatment decreased substantially, though the final results were still significant improvements compared with the control specimens. High thermal conductivity coefficient of NA slightly but not significantly improved properties. Due to the high spring-back after 15 days,densified poplar is not recommended for applications in which densified wood will be exposed for long periods to high humidity or to direct water.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.61974025,61504024)National International Science and Technology Cooperation Base on Railway Vehicle Operation Engineering of Beijing Jiaotong University(Grant Nos.BMRV21KF07,BMRV20KF03)XJTLU Research Development Fund of China(Grant Nos.RDF-17-02-44,RDF-SP-122).
文摘With the combination of 3D printing and electroplating technique,metal-coated resin lattice is a viable way to achieve lightweight design with desirable responses.However,due to high structural complexity,mechanical analysis of the macroscopic lattice structure demands high experimental or numerical costs.To efficiently investigate the mechanical behaviors of such structure,in this paper a multiscale numerical method is proposed to study the effective properties of the metal-coated Body-Centered-Cubic(BCC)lattices.Unlike studies of a similar kind in which the effective parameters can be predicted from a single unit cell model,it is noticed that the size effect of representative volume element(RVE)is severe and an insensitive prediction can be only obtained from models containing multiple-unit-cells.To this end,the paper determines the minimum number of unit cells in single RVE.Based on the proposed method that is validated through the experimental comparison,parametric studies are conducted to estimate the impact of strut diameter and coating film thickness on structural responses.It is shown that the increase of volume fraction may improve the elastic modulus and specific modulus remarkably.In contrast,the increase of thickness of coating film only leads to monotonously increased elastic modulus.For this reason,there should be an optimal coating film thickness for the specific modulus of the lattice structure.This work provides an effective method for evaluating structural mechanical properties via the mesoscopic model.
基金supported by Shahid Rajaee Teacher Training University under contract No.22927
文摘Effects of densification of poplar wood（Populus nigra） impregnated with nano-aluminum oxide（NA） and pre-treated with water vapor for 4 and 6 h were investigated in the present study. Physical and mechanical properties of treated poplar wood were measured according to the ASTM D-143 standard specifications, and then compared with the untreated specimens. Results showed significant improvement in all properties as a result of densification. A 4-h vapor pre-treatment improved effects on both physical and mechanical properties. When the duration of vapor-treatment increased to 6 h, wood polymers degraded to the extent that the improvements due to the vapor pre-treatment decreased substantially, though the final results were still significant improvements compared with the control specimens. High thermal conductivity coefficient of NA slightly but not significantly improved properties. Due to the high spring-back after 15 days,densified poplar is not recommended for applications in which densified wood will be exposed for long periods to high humidity or to direct water.
