Free quenching of automotive leaf springs is a new technology that has gradually started to be applied in the industry in China in recent years.Only a few manufacturers are applying it in the industry.Through more tha...Free quenching of automotive leaf springs is a new technology that has gradually started to be applied in the industry in China in recent years.Only a few manufacturers are applying it in the industry.Through more than half a year of on-site practice,the changes in the hot forming of spring plates before free quenching have been explored,and finally a heat treatment process that meets the production requirements of our company has been developed,achieving normal production.展开更多
Although the shell mould casting process has a wide range of application in many fields,the prediction of casting defects is still a problem.In the present work,a typical leaf spring bracket casting of ZG310-570 was f...Although the shell mould casting process has a wide range of application in many fields,the prediction of casting defects is still a problem.In the present work,a typical leaf spring bracket casting of ZG310-570 was fabricated by shell mold casting.The finite element model and ProCAST software were utilized for simulating the filling and solidification processes of the casting;and the formation mechanism of the gas pore,and shrinkage porosity defects were analyzed.The results indicate that the gas pore and shrinkage porosity defects are formed due to air entrapment,insufficient feeding and non-sequential solidification.Subsequently,through changing the position of risers,adding a connecting channel between the risers,and setting blind risers at the U-shaped brackets,an optimized gating and feeding system was established to improve the quality of the casting.After optimization,the gas pore and shrinkage porosity defects of the leaf spring bracket casting are effectively eliminated.The experiment results with the optimized casting process are in good agreement with the numerical simulation,which verifies the validity of the finite element model in the shell mould casting.展开更多
An adaptive dynamic vibration absorber(ADVA)is designed for lowfrequency vibration suppression.The leaf springs are applied as the tuning stiffness elements.The principle of variable stiffness is analyzed to obtain th...An adaptive dynamic vibration absorber(ADVA)is designed for lowfrequency vibration suppression.The leaf springs are applied as the tuning stiffness elements.The principle of variable stiffness is analyzed to obtain the effective range of the first natural frequency variation.A classic simply supported manipulator is selected as the controlled system.The coupled dynamic model of the manipulator-ADVA system is built to obtain the maximum damping efficiency and the vibration absorption capacity of the designed ADVA.An experimental platform is set up to verify the theoretical results.It is revealed that the ADVA can adjust the first natural frequency on a large scale by changing the curvature of the leaf springs.The amplitude of the manipulator is reduced obviously with the installation of the designed ADVA.Finally,based on the short-time Fourier transformation(STFT),a stepwise optimization algorithm is proposed to achieve a quick tuning of the natural frequency of the ADVA so that it can always coincide with the frequency of the prime structure.Through the above steps,the intelligent frequency tuning of the ADVA is realized with high vibration absorption performance in a wide frequency range.展开更多
common maize synthetic rate（ Photosynthetic characteristics were probed by sweet maize, waxy maize, high starch maize and The results revealed that leaf area index （LAI）, chlorophyll a content, chlorophyll b cont...common maize synthetic rate（ Photosynthetic characteristics were probed by sweet maize, waxy maize, high starch maize and The results revealed that leaf area index （LAI）, chlorophyll a content, chlorophyll b content,photo-PR） showed single peak curve at the whole growth stage. The stages of peak were different according to different varieties. NEAUS4 had the lowest peak and while SIDAN 19 had the highest among all stages. Ratio of chlorophyll a to b was low at seedling stage, reached the peak atjointing stage and then declined. SIDAN 19 had the lower level at the last stages.展开更多
气候变化背景下,为探索黄土高原半干旱区春玉米光合生理过程对土壤水分、温度变化的响应机制,以春玉米为研究对象,于2017年在中国气象局定西干旱气象与生态环境试验基地进行盆栽水分控制试验,在春玉米七叶期设置对照处理(Control,简称...气候变化背景下,为探索黄土高原半干旱区春玉米光合生理过程对土壤水分、温度变化的响应机制,以春玉米为研究对象,于2017年在中国气象局定西干旱气象与生态环境试验基地进行盆栽水分控制试验,在春玉米七叶期设置对照处理(Control,简称“CK处理”,土壤水分为田间持水量的80%)和控水处理(Water Stress,简称“WS处理”,土壤水分为田间持水量的45%~50%)以及3个叶片温度梯度,分别为适宜温度25℃、高温35℃及极端高温40℃(CK处理对应CK-25、CK-35及CK-40;WS处理对应WS-25、WS-35及WS-40),分析春玉米叶片气体交换参数和水分利用效率对土壤水分、温度变化的响应特征。结果表明:在一定的光合有效辐射(Photosynthetically Active Radiation,PAR)范围内,春玉米叶片净光合速率(Net Photosynthetic Rate,Pn)随PAR的增加逐渐增大。水分供给不足时,随着PAR不断增加,WS处理春玉米叶片气孔限制因素向非气孔限制因素转变,光合作用出现明显的光抑制,WS-35处理叶片Pn最大,WS处理叶片Pn在PAR高值区明显小于CK处理,且不同温度梯度下叶片达到光饱和的PAR下降;与CK-40处理相比,WS-40处理春玉米叶片Pn随PAR增大显著减小(P<0.05),光合作用表现出明显的光抑制。水分供给充足时,蒸腾速率(Transpiration Rate,Tr)随温度升高而增大;水分供给不足时,WS-40处理春玉米叶片Tr、气孔限制(Ls)较CK-40处理显著降低(P<0.05),胞间CO_(2)浓度(Ci)显著增加(P<0.05)。WS-40处理春玉米Tr随着PAR的增大而减小,水分利用效率(Water Use Efficiency,WUE)较CK处理高。该研究可为气候变化背景下黄土高原半干旱区春玉米应对极端气候生理特征变化提供参考。展开更多
文摘Free quenching of automotive leaf springs is a new technology that has gradually started to be applied in the industry in China in recent years.Only a few manufacturers are applying it in the industry.Through more than half a year of on-site practice,the changes in the hot forming of spring plates before free quenching have been explored,and finally a heat treatment process that meets the production requirements of our company has been developed,achieving normal production.
基金financially supported by the Major Science and Technology Projects in Anhui Province (No. 18030901097)the Natural Science Foundation of Anhui Province (No.1908085QE197)the Fundamental Research Funds for the Central Universities (JZ2018HGBZ0133, JZ2019HGTA0043)
文摘Although the shell mould casting process has a wide range of application in many fields,the prediction of casting defects is still a problem.In the present work,a typical leaf spring bracket casting of ZG310-570 was fabricated by shell mold casting.The finite element model and ProCAST software were utilized for simulating the filling and solidification processes of the casting;and the formation mechanism of the gas pore,and shrinkage porosity defects were analyzed.The results indicate that the gas pore and shrinkage porosity defects are formed due to air entrapment,insufficient feeding and non-sequential solidification.Subsequently,through changing the position of risers,adding a connecting channel between the risers,and setting blind risers at the U-shaped brackets,an optimized gating and feeding system was established to improve the quality of the casting.After optimization,the gas pore and shrinkage porosity defects of the leaf spring bracket casting are effectively eliminated.The experiment results with the optimized casting process are in good agreement with the numerical simulation,which verifies the validity of the finite element model in the shell mould casting.
基金supported by the National Natural Science Foundation of China(Nos.11772010 and 11832002)the State Key Laboratory of Mechanical System and Vibration of China(No.MSV202004)。
文摘An adaptive dynamic vibration absorber(ADVA)is designed for lowfrequency vibration suppression.The leaf springs are applied as the tuning stiffness elements.The principle of variable stiffness is analyzed to obtain the effective range of the first natural frequency variation.A classic simply supported manipulator is selected as the controlled system.The coupled dynamic model of the manipulator-ADVA system is built to obtain the maximum damping efficiency and the vibration absorption capacity of the designed ADVA.An experimental platform is set up to verify the theoretical results.It is revealed that the ADVA can adjust the first natural frequency on a large scale by changing the curvature of the leaf springs.The amplitude of the manipulator is reduced obviously with the installation of the designed ADVA.Finally,based on the short-time Fourier transformation(STFT),a stepwise optimization algorithm is proposed to achieve a quick tuning of the natural frequency of the ADVA so that it can always coincide with the frequency of the prime structure.Through the above steps,the intelligent frequency tuning of the ADVA is realized with high vibration absorption performance in a wide frequency range.
文摘common maize synthetic rate（ Photosynthetic characteristics were probed by sweet maize, waxy maize, high starch maize and The results revealed that leaf area index （LAI）, chlorophyll a content, chlorophyll b content,photo-PR） showed single peak curve at the whole growth stage. The stages of peak were different according to different varieties. NEAUS4 had the lowest peak and while SIDAN 19 had the highest among all stages. Ratio of chlorophyll a to b was low at seedling stage, reached the peak atjointing stage and then declined. SIDAN 19 had the lower level at the last stages.
基金the National Key Basic Research Special Foundation (NKBRSF) of China (No.G2000018603)and the National High Technology Research and Development Program (863 Program) of China (No.2002AA2Z4191).
文摘气候变化背景下,为探索黄土高原半干旱区春玉米光合生理过程对土壤水分、温度变化的响应机制,以春玉米为研究对象,于2017年在中国气象局定西干旱气象与生态环境试验基地进行盆栽水分控制试验,在春玉米七叶期设置对照处理(Control,简称“CK处理”,土壤水分为田间持水量的80%)和控水处理(Water Stress,简称“WS处理”,土壤水分为田间持水量的45%~50%)以及3个叶片温度梯度,分别为适宜温度25℃、高温35℃及极端高温40℃(CK处理对应CK-25、CK-35及CK-40;WS处理对应WS-25、WS-35及WS-40),分析春玉米叶片气体交换参数和水分利用效率对土壤水分、温度变化的响应特征。结果表明:在一定的光合有效辐射(Photosynthetically Active Radiation,PAR)范围内,春玉米叶片净光合速率(Net Photosynthetic Rate,Pn)随PAR的增加逐渐增大。水分供给不足时,随着PAR不断增加,WS处理春玉米叶片气孔限制因素向非气孔限制因素转变,光合作用出现明显的光抑制,WS-35处理叶片Pn最大,WS处理叶片Pn在PAR高值区明显小于CK处理,且不同温度梯度下叶片达到光饱和的PAR下降;与CK-40处理相比,WS-40处理春玉米叶片Pn随PAR增大显著减小(P<0.05),光合作用表现出明显的光抑制。水分供给充足时,蒸腾速率(Transpiration Rate,Tr)随温度升高而增大;水分供给不足时,WS-40处理春玉米叶片Tr、气孔限制(Ls)较CK-40处理显著降低(P<0.05),胞间CO_(2)浓度(Ci)显著增加(P<0.05)。WS-40处理春玉米Tr随着PAR的增大而减小,水分利用效率(Water Use Efficiency,WUE)较CK处理高。该研究可为气候变化背景下黄土高原半干旱区春玉米应对极端气候生理特征变化提供参考。
