采用常规PID（比例-积分-微分）控制和基于模糊自适应PID控制的智能控制方式分别进行了汽车齿圈40Cr Ni Mo钢连铸浇注温度的控制,并进行了试样的耐磨损性能测试与分析。结果表明：智能控制可以明显提高试样的耐磨损性能。与常规控制相比...采用常规PID（比例-积分-微分）控制和基于模糊自适应PID控制的智能控制方式分别进行了汽车齿圈40Cr Ni Mo钢连铸浇注温度的控制,并进行了试样的耐磨损性能测试与分析。结果表明：智能控制可以明显提高试样的耐磨损性能。与常规控制相比,智能控制试样的室温磨损体积从16.55×10-3mm3减小到11.38×10-3mm3,减小了31.24%;高温磨损体积从36.99×10-3mm3减小到20.00×10-3mm3,减小了45.93%。展开更多
To reduce the difficulty of material filling into the top region of tooth in hot precision forging of gears using the alternative die designs, relief-cavity designs in different sizes were performed on the top of die ...To reduce the difficulty of material filling into the top region of tooth in hot precision forging of gears using the alternative die designs, relief-cavity designs in different sizes were performed on the top of die tooth. The influences of the conventional process and relief-cavity designs on corner filling, workpiece stress, die stress, forming load and material utilization were examined. Finite element simulation for tooth forming, die stress and forming load using the four designs was performed. The material utilization was further considered, and the optimal design was determined. The tooth form and forming load in forging trials ensured the validity of FE simulation. Tooth accuracy was inspected by video measuring machine(VMM), which shows the hot forged accuracy achieves the level of rough machining of gear teeth. The effects of friction on mode of metal flow and strain distribution were also discussed.展开更多
Objective： To study the effect of surface configuration and roughness on the corrosion resistance of pure Titanium （Ti） after used in oral environment for half a year. Methods ：Three edentulous volunteers with hea...Objective： To study the effect of surface configuration and roughness on the corrosion resistance of pure Titanium （Ti） after used in oral environment for half a year. Methods ：Three edentulous volunteers with healthy oral mucosa participated in an in vivo study. Four kinds of pure Ti testing pieces with different surface roughness were fixed in the polished surface of upper complete dentures and the other in the tissue surface of the dentures. After 6-month wearing the denture, dynamic polarization curves were traced with electrochemical method. Results：Ep and Ip of specimen used in oral cavity was higher than that left in air,which meant corrosion resistance falling. Compared to plane one ,Ecorr of wrinkly specimen was more positive,and Ep and Ip were more higher,so its corrosion resistance reduced. With the increase of surface roughness,Ep and Ip increased from 0.937 V and 1.810μA （Group Ⅱ） to 1.701 V and 2.252μA （Group Ⅳ）respectively,there was even no passivation in Group Ⅲ （which was the most coarse）,so proneness to corrosion enhanced. For specimen with the same surface roughness ,Ep and Ip of Group Ⅳ （1.701 V and 2.252 μA respectively） ,which was placed on polished surface of denture base,was higher than that on tissue surface（Group V , 1. 304 V, 1. 946μA）. Conclusion： From the perspective of corrosion behavior, wrinkly surface should not be adopted when pure Ti prosthesis is used,and surface roughness on the polishing surface of pure Ti prosthesis should be paid more attention,especially on clasps and connectors, where there is often more force to be exerted.展开更多
Recent studies show an increase in the population of beavers, nutria and other rodents in vast regions of central Europe over the last 15 years. Unfortunately, this caused in many instances considerable damage on larg...Recent studies show an increase in the population of beavers, nutria and other rodents in vast regions of central Europe over the last 15 years. Unfortunately, this caused in many instances considerable damage on large rivers along dykes and earthworks in the floodplain areas, leading to an increased risk of bank failures. However, most of these mammals belong to protected species. This work is aimed at showing positive experience in cooperation with universities, research institutes and environmental agencies regarding measures to permanently safeguard the banks using composite erosion control systems with polymer coated steel wire net （as flexible reinforcement component） and a geosynthetic （to promote vegetation growth）. The steel mesh component works as an effective long-term barrier against the intrusion of mammals, discouraging them from digging inside the core of the dyke. An analysis of the sensitive areas to be protected led also to definition of the characteristics of these interventions （length, shape, escape ways, population areas, etc.）. The study will present several additional benefits when using polymer steel nets along dykes, such as： high and durable erosion protection in overflow areas, promotion of fast and effective vegetation growth （increasing stability）, surface protection against ice impacts （in northern regions）, ease of installation, maintenance, ability to conform to irregular shapes of the slope. This work will also present the positive outcome of research studies along dykes in Germany, Austria and in Italy.展开更多
Design of composites and usage of new polymer materials allows for improvement of constructional properties of belts. Different applications： transmission, conveying or controlling have different meshing in gear. The...Design of composites and usage of new polymer materials allows for improvement of constructional properties of belts. Different applications： transmission, conveying or controlling have different meshing in gear. The work presents meshing model between timing belt and pulley and constructional features of transmission timing belts depending on materials used for their production. While designing timing belt, much attention should be paid to selection of materials, which has significant influence on mechanical properties of belts. This paper attempts to identify the model material and the nature of cooperation of timing belt-pulley; this is basic knowledge for the development of timing belt gear.展开更多
文摘采用常规PID（比例-积分-微分）控制和基于模糊自适应PID控制的智能控制方式分别进行了汽车齿圈40Cr Ni Mo钢连铸浇注温度的控制,并进行了试样的耐磨损性能测试与分析。结果表明：智能控制可以明显提高试样的耐磨损性能。与常规控制相比,智能控制试样的室温磨损体积从16.55×10-3mm3减小到11.38×10-3mm3,减小了31.24%;高温磨损体积从36.99×10-3mm3减小到20.00×10-3mm3,减小了45.93%。
基金Project(51375042)supported by the National Natural Science Foundation of ChinaProject supported by Beijing Laboratory of Modern Transport Metal Materials and Processing Technology,China
文摘To reduce the difficulty of material filling into the top region of tooth in hot precision forging of gears using the alternative die designs, relief-cavity designs in different sizes were performed on the top of die tooth. The influences of the conventional process and relief-cavity designs on corner filling, workpiece stress, die stress, forming load and material utilization were examined. Finite element simulation for tooth forming, die stress and forming load using the four designs was performed. The material utilization was further considered, and the optimal design was determined. The tooth form and forming load in forging trials ensured the validity of FE simulation. Tooth accuracy was inspected by video measuring machine(VMM), which shows the hot forged accuracy achieves the level of rough machining of gear teeth. The effects of friction on mode of metal flow and strain distribution were also discussed.
文摘Objective： To study the effect of surface configuration and roughness on the corrosion resistance of pure Titanium （Ti） after used in oral environment for half a year. Methods ：Three edentulous volunteers with healthy oral mucosa participated in an in vivo study. Four kinds of pure Ti testing pieces with different surface roughness were fixed in the polished surface of upper complete dentures and the other in the tissue surface of the dentures. After 6-month wearing the denture, dynamic polarization curves were traced with electrochemical method. Results：Ep and Ip of specimen used in oral cavity was higher than that left in air,which meant corrosion resistance falling. Compared to plane one ,Ecorr of wrinkly specimen was more positive,and Ep and Ip were more higher,so its corrosion resistance reduced. With the increase of surface roughness,Ep and Ip increased from 0.937 V and 1.810μA （Group Ⅱ） to 1.701 V and 2.252μA （Group Ⅳ）respectively,there was even no passivation in Group Ⅲ （which was the most coarse）,so proneness to corrosion enhanced. For specimen with the same surface roughness ,Ep and Ip of Group Ⅳ （1.701 V and 2.252 μA respectively） ,which was placed on polished surface of denture base,was higher than that on tissue surface（Group V , 1. 304 V, 1. 946μA）. Conclusion： From the perspective of corrosion behavior, wrinkly surface should not be adopted when pure Ti prosthesis is used,and surface roughness on the polishing surface of pure Ti prosthesis should be paid more attention,especially on clasps and connectors, where there is often more force to be exerted.
文摘Recent studies show an increase in the population of beavers, nutria and other rodents in vast regions of central Europe over the last 15 years. Unfortunately, this caused in many instances considerable damage on large rivers along dykes and earthworks in the floodplain areas, leading to an increased risk of bank failures. However, most of these mammals belong to protected species. This work is aimed at showing positive experience in cooperation with universities, research institutes and environmental agencies regarding measures to permanently safeguard the banks using composite erosion control systems with polymer coated steel wire net （as flexible reinforcement component） and a geosynthetic （to promote vegetation growth）. The steel mesh component works as an effective long-term barrier against the intrusion of mammals, discouraging them from digging inside the core of the dyke. An analysis of the sensitive areas to be protected led also to definition of the characteristics of these interventions （length, shape, escape ways, population areas, etc.）. The study will present several additional benefits when using polymer steel nets along dykes, such as： high and durable erosion protection in overflow areas, promotion of fast and effective vegetation growth （increasing stability）, surface protection against ice impacts （in northern regions）, ease of installation, maintenance, ability to conform to irregular shapes of the slope. This work will also present the positive outcome of research studies along dykes in Germany, Austria and in Italy.
文摘Design of composites and usage of new polymer materials allows for improvement of constructional properties of belts. Different applications： transmission, conveying or controlling have different meshing in gear. The work presents meshing model between timing belt and pulley and constructional features of transmission timing belts depending on materials used for their production. While designing timing belt, much attention should be paid to selection of materials, which has significant influence on mechanical properties of belts. This paper attempts to identify the model material and the nature of cooperation of timing belt-pulley; this is basic knowledge for the development of timing belt gear.
