This paper proposes a multiscale isogeometric topology optimization(ITO)method where the configuration and layout of microstructures are optimized simultaneously.At micro scale,a shape deformation method is presented ...This paper proposes a multiscale isogeometric topology optimization(ITO)method where the configuration and layout of microstructures are optimized simultaneously.At micro scale,a shape deformation method is presented to transform a prototype microstructure(PM)for obtaining a series of graded microstructures(GMs),where microstructural skeleton based on the level set framework is applied to retain more topology features and improve the connectability.For the macro scale calculation,the effective mechanical properties can be estimated by means of the numerical homogenization method.By adopting identical non-uniform rational basis splines(NURBS)as basis functions for both parameterized level set model and isogeometric calculation model,the isogeometric analysis(IGA)is integrated into the level set method,which contributes to improving the accuracy and efficiency.Numerical examples demonstrate that,the proposed method is effective in improving the performance and manufacturability.展开更多
The formation and the thermal stability of a connected hard skeleton structure(CHSS) in the matrix of Mg-5Al-2Sn-5Ca(ATX525) alloy were investigated by using X-ray diffractometer, scanning electron microscopy, differe...The formation and the thermal stability of a connected hard skeleton structure(CHSS) in the matrix of Mg-5Al-2Sn-5Ca(ATX525) alloy were investigated by using X-ray diffractometer, scanning electron microscopy, differential scanning calorimeter, creep tester and isothermal treatment method. The results indicated that the CHSS composed of Mg2(Al,Ca) and Al2 Ca intermetallics was formed into a typical eutectic structure and no obvious change occurred when the samples were isothermally treated at 250 °C for 96 h and 350 °C for 72 h, respectively. It became a chained structure when isothermally treated at 450 °C for 48 h. The dissolution and reconstruction processes, however, were observed for the CHSS when the processing temperature was up to 550 °C. The creep life at the stress-temperature condition of 50MPa/200°C for the alloy treated at 450 °C for 48 h was as high as 510 h, and the strain at creep time of 100 h was as low as 0.03%, which indicated that the present alloy has not only a good thermal stability, but also a better heat resistance.展开更多
Optimizing highly porous fibrous ceramics, like bird’s nest structure, were obtained by vacuum impregnation method with mullite fibers and alumina sol as raw material. The influences of impregnation cycles on the pro...Optimizing highly porous fibrous ceramics, like bird’s nest structure, were obtained by vacuum impregnation method with mullite fibers and alumina sol as raw material. The influences of impregnation cycles on the property of the sample, such as porosity, compressive strength and room-temperature thermal conductivity were explored. The experimental results show that the 3D skeleton structure of the sample was constructed by the randomly arranged mullite fibers and inorganic particles. The content of alumina can be adjusted effectively by impregnation times and it increases with increasing impregnation cycles. The thermal conductivity and compressive strength can also be controlled via tailored impregnation cycles. The compressive strength of fibrous ceramic ranged from 1.03 MPa to 5.31 MPa, while the porosity decrease slightly from 85.3% to 73.8%. In the same time, the thermal conductivity increase from 0.037 W/(m·K) to 0.217 W/(m·K), indicating that the fibrous ceramic with high impressive and low thermal conductivity can be fabricated by impregnation method.展开更多
Inspired by the safe landing of a cat falling from a high altitude,a bio-inspired polygonal skeleton(BIPS) structure is proposed,and its nonlinear characteristics are systematically studied to explore its potential ap...Inspired by the safe landing of a cat falling from a high altitude,a bio-inspired polygonal skeleton(BIPS) structure is proposed,and its nonlinear characteristics are systematically studied to explore its potential application in the suppression of vibration. The polygon is formed by the skeleton structure of the cat’s entire body and the ground. The BIPS system consists of two symmetrical bionic legs with three robs(as skeleton) and four horizontal springs(as muscle). Two bionic legs are connected through the bearing platform(as spine),which could adjust the distance between the two bionic legs. A theoretical model is developed to characterize its stiffness nonlinearity through geometrical and mechanical analysis. Parameter analysis reveals that the BIPS structure has diverse stiffness,including nonlinear positive stiffness and negative stiffness. By imitating adjustment of leg posture and telescopic function of the spine(control the distance between legs),these flexible stiffness properties can be adjusted by structure parameters. In addition,the load capacity and working range can also be designed by the length of the bars,the initial angle,the mounting position,and the spring stiffness. The experimental setup is established,and the vibration isolation performance under various excitation is tested. The experimental results verify the accuracy of the dynamic model and also show that the proposed BIPS structure can suppress the vibration effectively under a variety of excitations. These peculiarities may provide potential possibility of an innovative approach to passive vibration control and isolation.展开更多
We exploited a unique porous structure of the nano-covalent triazinepolymer(NCTP)containing aggregation-induced emission(AlE)group to achievecontrolled release and drug tracking in tumor acidic microenvironment.NCTP w...We exploited a unique porous structure of the nano-covalent triazinepolymer(NCTP)containing aggregation-induced emission(AlE)group to achievecontrolled release and drug tracking in tumor acidic microenvironment.NCTP wassynthesized by the Friedel-Crafts alkylation and the McMurry coupling reaction.It notonly had strong doxorubicin(DOX)-loading capacity due to its high specific surface areaand large pore volume,but also showed the significant cumulative drug release as aresult of the pH response of triazine polymers.NCTP was induced luminescence aftermass accumulation near tumor cells.Besides,it had excellent biocompatibility andobvious antineoplastic toxicity.The results demonstrate that NCTP as a utility-type drugcarrier provides a new route for designing the multi-functional drug delivery platform.展开更多
The cause of the premature failure of 304 stainless steel tube heat exchanger was investigated.The unique skeleton structure inside the leakage point reveals that this is a new damage mechanism caused by a δ+γ two-p...The cause of the premature failure of 304 stainless steel tube heat exchanger was investigated.The unique skeleton structure inside the leakage point reveals that this is a new damage mechanism caused by a δ+γ two-phase structure and crevice corrosion.The three-dimensional structure of the leakage point was demonstrated using X-ray diffraction topography.The results of scanning electron microscope examination show the microstructure of the weld to be columnar and dendritic.It is found by electron probe microscope analysis and transmission electron microscopy that columnar dendrites consisted of γ-dendrite and an amount of δ-ferrite phases at the dendrite trunk.Simulated corrosion test results confirmed that the corrosion medium was the chloride ion.Crevice corrosion of chloride ions occurred at weld defects on the inner wall thus forming a concentration cell.Grains of columnar dendrites were then corroded by chloride ions and δ-ferrite phases on the grain boundaries were retained,which formed the particular skeleton corrosion structure.As a result,it led to leakage when the corrosion of weld occurred from the inner wall to the outer wall.展开更多
基金National Key R&D Program of China(2018YFB1700803,2018YFB1700804).
文摘This paper proposes a multiscale isogeometric topology optimization(ITO)method where the configuration and layout of microstructures are optimized simultaneously.At micro scale,a shape deformation method is presented to transform a prototype microstructure(PM)for obtaining a series of graded microstructures(GMs),where microstructural skeleton based on the level set framework is applied to retain more topology features and improve the connectability.For the macro scale calculation,the effective mechanical properties can be estimated by means of the numerical homogenization method.By adopting identical non-uniform rational basis splines(NURBS)as basis functions for both parameterized level set model and isogeometric calculation model,the isogeometric analysis(IGA)is integrated into the level set method,which contributes to improving the accuracy and efficiency.Numerical examples demonstrate that,the proposed method is effective in improving the performance and manufacturability.
文摘The formation and the thermal stability of a connected hard skeleton structure(CHSS) in the matrix of Mg-5Al-2Sn-5Ca(ATX525) alloy were investigated by using X-ray diffractometer, scanning electron microscopy, differential scanning calorimeter, creep tester and isothermal treatment method. The results indicated that the CHSS composed of Mg2(Al,Ca) and Al2 Ca intermetallics was formed into a typical eutectic structure and no obvious change occurred when the samples were isothermally treated at 250 °C for 96 h and 350 °C for 72 h, respectively. It became a chained structure when isothermally treated at 450 °C for 48 h. The dissolution and reconstruction processes, however, were observed for the CHSS when the processing temperature was up to 550 °C. The creep life at the stress-temperature condition of 50MPa/200°C for the alloy treated at 450 °C for 48 h was as high as 510 h, and the strain at creep time of 100 h was as low as 0.03%, which indicated that the present alloy has not only a good thermal stability, but also a better heat resistance.
基金Funded by the National Natural Science Foundation of China(No.51772139)
文摘Optimizing highly porous fibrous ceramics, like bird’s nest structure, were obtained by vacuum impregnation method with mullite fibers and alumina sol as raw material. The influences of impregnation cycles on the property of the sample, such as porosity, compressive strength and room-temperature thermal conductivity were explored. The experimental results show that the 3D skeleton structure of the sample was constructed by the randomly arranged mullite fibers and inorganic particles. The content of alumina can be adjusted effectively by impregnation times and it increases with increasing impregnation cycles. The thermal conductivity and compressive strength can also be controlled via tailored impregnation cycles. The compressive strength of fibrous ceramic ranged from 1.03 MPa to 5.31 MPa, while the porosity decrease slightly from 85.3% to 73.8%. In the same time, the thermal conductivity increase from 0.037 W/(m·K) to 0.217 W/(m·K), indicating that the fibrous ceramic with high impressive and low thermal conductivity can be fabricated by impregnation method.
基金This work was supported by the National Science Fund for Distinguished Young Scholars(Grant No.11625208)the Innovation Program of Shanghai Municipal Education Commission(Grant No.2019-01-07-00-02-E00030)the Program of Shanghai Academic/Technology Research Leader(Grant No.19XD1421600)。
文摘Inspired by the safe landing of a cat falling from a high altitude,a bio-inspired polygonal skeleton(BIPS) structure is proposed,and its nonlinear characteristics are systematically studied to explore its potential application in the suppression of vibration. The polygon is formed by the skeleton structure of the cat’s entire body and the ground. The BIPS system consists of two symmetrical bionic legs with three robs(as skeleton) and four horizontal springs(as muscle). Two bionic legs are connected through the bearing platform(as spine),which could adjust the distance between the two bionic legs. A theoretical model is developed to characterize its stiffness nonlinearity through geometrical and mechanical analysis. Parameter analysis reveals that the BIPS structure has diverse stiffness,including nonlinear positive stiffness and negative stiffness. By imitating adjustment of leg posture and telescopic function of the spine(control the distance between legs),these flexible stiffness properties can be adjusted by structure parameters. In addition,the load capacity and working range can also be designed by the length of the bars,the initial angle,the mounting position,and the spring stiffness. The experimental setup is established,and the vibration isolation performance under various excitation is tested. The experimental results verify the accuracy of the dynamic model and also show that the proposed BIPS structure can suppress the vibration effectively under a variety of excitations. These peculiarities may provide potential possibility of an innovative approach to passive vibration control and isolation.
基金supported by the Corps DivisionDevelopment and Innovation Support Program(2017BA041)the National Natural Science Foundation of China(Grant Nos.21866028 and 51662036)+1 种基金the Engineering Research Center of Materials-Oriented Chemical Engineering of Xinjiang Bintuan(2016BTRCO08 and 2016BTRCO05)the Natural Science Foundation of Shihezi University(ZZZC201922A).
文摘We exploited a unique porous structure of the nano-covalent triazinepolymer(NCTP)containing aggregation-induced emission(AlE)group to achievecontrolled release and drug tracking in tumor acidic microenvironment.NCTP wassynthesized by the Friedel-Crafts alkylation and the McMurry coupling reaction.It notonly had strong doxorubicin(DOX)-loading capacity due to its high specific surface areaand large pore volume,but also showed the significant cumulative drug release as aresult of the pH response of triazine polymers.NCTP was induced luminescence aftermass accumulation near tumor cells.Besides,it had excellent biocompatibility andobvious antineoplastic toxicity.The results demonstrate that NCTP as a utility-type drugcarrier provides a new route for designing the multi-functional drug delivery platform.
文摘The cause of the premature failure of 304 stainless steel tube heat exchanger was investigated.The unique skeleton structure inside the leakage point reveals that this is a new damage mechanism caused by a δ+γ two-phase structure and crevice corrosion.The three-dimensional structure of the leakage point was demonstrated using X-ray diffraction topography.The results of scanning electron microscope examination show the microstructure of the weld to be columnar and dendritic.It is found by electron probe microscope analysis and transmission electron microscopy that columnar dendrites consisted of γ-dendrite and an amount of δ-ferrite phases at the dendrite trunk.Simulated corrosion test results confirmed that the corrosion medium was the chloride ion.Crevice corrosion of chloride ions occurred at weld defects on the inner wall thus forming a concentration cell.Grains of columnar dendrites were then corroded by chloride ions and δ-ferrite phases on the grain boundaries were retained,which formed the particular skeleton corrosion structure.As a result,it led to leakage when the corrosion of weld occurred from the inner wall to the outer wall.
