To improve the mechanical properties of Ti6Al4V alloy prepared by selective laser melting(SLM)process,the precision forging was conducted at950°C and different strains and strain rates.The microstructure evolutio...To improve the mechanical properties of Ti6Al4V alloy prepared by selective laser melting(SLM)process,the precision forging was conducted at950°C and different strains and strain rates.The microstructure evolution of as-built samples and forged samples in both horizontal and vertical sections was visualized and analyzed by optical microscope and X-ray diffraction.The microstructure was improved by the precision forging and subsequent water quenching.The porosity in each section was accounted.It can be seen that high strain rate and large deformation result in low porosity,consequently contributing to a better fatigue performance.The micro-hardness was lowered after precision forging and water quenching,while the difference of microhardness between the horizontal and vertical sections became smaller,which illustrated that this process can improve the anisotropy of structural components fabricated by SLM.展开更多
3D numerical simulations of dynamical tensile response of hybrid carbon nanotube(CNT)and SiC nanoparticle reinforced AZ91D magnesium(Mg)based composites considering interface cohesion over a temperature range from 25 ...3D numerical simulations of dynamical tensile response of hybrid carbon nanotube(CNT)and SiC nanoparticle reinforced AZ91D magnesium(Mg)based composites considering interface cohesion over a temperature range from 25 to 300℃ were carried out using a 3D representative volume element(RVE)approach.The simulation predictions were compared with the experimental results.It is clearly shown that the overall dynamic tensile properties of the nanocomposites at different temperatures are improved when the total volume fraction and volume fraction ratio of hybrid CNTs to SiC nanoparticles increase.The overall maximum hybrid effect is achieved when the hybrid volume fraction ratio of CNTs to SiC nanoparticles is in the range from 7:3 to 8:2 under the condition of total volume fraction of 1.0%.The composites present positive strain rate hardening and temperature softening effects under dynamic loading at high temperatures.The simulation results are in good agreement with the experimental data.展开更多
Battlefield internal medicine aims at the treatment of combatants and noncombatants with various internal diseases on the battlefield.The military medical research on battlefield internal diseases focuses on the patho...Battlefield internal medicine aims at the treatment of combatants and noncombatants with various internal diseases on the battlefield.The military medical research on battlefield internal diseases focuses on the pathogenesis,clinical management,and prevention of internal diseases under military war conditions.In both wartime and peacetime,the soldiers suffer from more internal diseases than surgical wounds.With the introduction of high-tech weapons,including chemical,physical,and biological agents,a large number of special internal illnesses and casualties will appear in future wars.The battles often occur in special environments,such as high or low temperatures,plateau or polar areas,and micro-or hyper-gravity.The current theories of battlefield internal medicine are mainly derived from wars decades ago and cannot meet the needs of military medical support under the conditions of modern warfare.Therefore,the military medical research on battlefield internal medicine should be based on contemporary military situations,focus on the purpose of treating battlefield internal diseases,and adhere to the actual needs of the troops in peacetime and wartime.We should investigate the pathogenesis of battlefield internal diseases and explore the threats that may arise in future wars to ensure the advancement of battlefield internal medicine.This review highlights new concepts,demands,challenges,and opportunities for the further development of military medical research on battlefield internal medicine.展开更多
基金Project(50975222)supported by the National Natural Science Foundation of ChinaProject(2014ko8-34)supported by the Industrial Research Project of Shaanxi Province,China
文摘To improve the mechanical properties of Ti6Al4V alloy prepared by selective laser melting(SLM)process,the precision forging was conducted at950°C and different strains and strain rates.The microstructure evolution of as-built samples and forged samples in both horizontal and vertical sections was visualized and analyzed by optical microscope and X-ray diffraction.The microstructure was improved by the precision forging and subsequent water quenching.The porosity in each section was accounted.It can be seen that high strain rate and large deformation result in low porosity,consequently contributing to a better fatigue performance.The micro-hardness was lowered after precision forging and water quenching,while the difference of microhardness between the horizontal and vertical sections became smaller,which illustrated that this process can improve the anisotropy of structural components fabricated by SLM.
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(11672055,11272072).
文摘3D numerical simulations of dynamical tensile response of hybrid carbon nanotube(CNT)and SiC nanoparticle reinforced AZ91D magnesium(Mg)based composites considering interface cohesion over a temperature range from 25 to 300℃ were carried out using a 3D representative volume element(RVE)approach.The simulation predictions were compared with the experimental results.It is clearly shown that the overall dynamic tensile properties of the nanocomposites at different temperatures are improved when the total volume fraction and volume fraction ratio of hybrid CNTs to SiC nanoparticles increase.The overall maximum hybrid effect is achieved when the hybrid volume fraction ratio of CNTs to SiC nanoparticles is in the range from 7:3 to 8:2 under the condition of total volume fraction of 1.0%.The composites present positive strain rate hardening and temperature softening effects under dynamic loading at high temperatures.The simulation results are in good agreement with the experimental data.
基金the National Natural Science Foundation of China(81871516 and 81571841)the Youth Special Project of Chinese PLA General Hospital(QNC19052).
文摘Battlefield internal medicine aims at the treatment of combatants and noncombatants with various internal diseases on the battlefield.The military medical research on battlefield internal diseases focuses on the pathogenesis,clinical management,and prevention of internal diseases under military war conditions.In both wartime and peacetime,the soldiers suffer from more internal diseases than surgical wounds.With the introduction of high-tech weapons,including chemical,physical,and biological agents,a large number of special internal illnesses and casualties will appear in future wars.The battles often occur in special environments,such as high or low temperatures,plateau or polar areas,and micro-or hyper-gravity.The current theories of battlefield internal medicine are mainly derived from wars decades ago and cannot meet the needs of military medical support under the conditions of modern warfare.Therefore,the military medical research on battlefield internal medicine should be based on contemporary military situations,focus on the purpose of treating battlefield internal diseases,and adhere to the actual needs of the troops in peacetime and wartime.We should investigate the pathogenesis of battlefield internal diseases and explore the threats that may arise in future wars to ensure the advancement of battlefield internal medicine.This review highlights new concepts,demands,challenges,and opportunities for the further development of military medical research on battlefield internal medicine.
