The damage tolerance for pipe/rod bar in the auxiliary power units （APUs） support system is studied. The main objective is to study whether planes can safely land when the fatigue crack appears on the bar. Firstly, ...The damage tolerance for pipe/rod bar in the auxiliary power units （APUs） support system is studied. The main objective is to study whether planes can safely land when the fatigue crack appears on the bar. Firstly, the stress intensity factors （K~） of two bar structures are computed, and the iso-stress intensity factor （iso-Kl） model is presented. The model uses the finite element model （FEM） instead of the parameters of material to com- pute the crack propagation. Then, the general relations between Kt vs crack size are obtained for different mate- rials, inner to outer diameter ratios （D^n/Dout） and external crack propagation angles （0）. Finally, the FEM anal- ysis results are input to the ANSYS parametric design language（ANSYS-APDL） software. And the fatigue life of damaged bar is estimated under the condition of loading spectrum.展开更多
In this paper we focus ourselves on the positive cone of the locally solid Riesz spaces to characterize the fundamentality. From one example the article indicates that the fundamentality of the locally solid Riesz spa...In this paper we focus ourselves on the positive cone of the locally solid Riesz spaces to characterize the fundamentality. From one example the article indicates that the fundamentality of the locally solid Riesz space is independent from the Lebesgue property.展开更多
Stiffening-ribbed-hollow-pipe cast-in place reinforced concrete girderless floor is a new-style hollow girderless floor system. Model experimental researches of simply-supported floor and four-corners bearing floor ha...Stiffening-ribbed-hollow-pipe cast-in place reinforced concrete girderless floor is a new-style hollow girderless floor system. Model experimental researches of simply-supported floor and four-corners bearing floor have been done on this new kind of floor system in this paper. The experiment results show that the floor system has good mechanical property such as high bearing capacity, big rigidity and good tensility. A theoretical method is presented in this paper that the stiffening-ribbed-hollow-pipe girderless floor can be analyzed by being converted equivalently to orthotropic solid slab. It is indicated that the method is correct and reasonable according to the contrast between theoretical calculated results and experimental measured results. The theoretical results coincide with the measured results well.展开更多
A LM-2F launch vehicle lifted off from the Jiuquan Satellite Launch Center at22：04 Beijing time on September 15,putting China’s first space laboratory Tiangong 2 into space.575 seconds after the liftoff,Tiangong 2 s...A LM-2F launch vehicle lifted off from the Jiuquan Satellite Launch Center at22：04 Beijing time on September 15,putting China’s first space laboratory Tiangong 2 into space.575 seconds after the liftoff,Tiangong 2 separated from the carrier rocket and entered its preset orbit.The launch achieved complete success.展开更多
The centrifugal air compressor outlet pipeline vibration was not decreased after barrel viscous dampers were installed in a petrochemical plant in Tianjin.A pipeline-damper experiment apparatus was built for studying ...The centrifugal air compressor outlet pipeline vibration was not decreased after barrel viscous dampers were installed in a petrochemical plant in Tianjin.A pipeline-damper experiment apparatus was built for studying the influence factors of the barrel viscous damper and pipe hoop in pipeline vibration reduction.The performance of the damper under different frequency and amplitude was researched respectively,the results showed that damping effect dependsed mainly on frequency and was not related to amplitude.Damper will fail when its vibration frequency exceeds its limit working frequency which was 40 Hz in test.The mechanical properties and energy dissipation were analyzed by using the Maxwell model,which explains experimental results well.According to damping effect and calculation of stiffness with ANSYS in different hoop width,hoop stiffness should match pipe stiffness and keep uniform along transfer path.Damping effect will get worse when local stiffness is too small or too large.Finally,the outlet pipeline vibration was decreased by 70%after using appropriate pipe hoop width and replacing the original damping liquid.展开更多
To reduce the influence of adverse flow conditions at the fan hub and improve fan aerodynamic performance, a modification of conventional axial fan blades with numerical and experimental investigation is presented. Ho...To reduce the influence of adverse flow conditions at the fan hub and improve fan aerodynamic performance, a modification of conventional axial fan blades with numerical and experimental investigation is presented. Hollow blade root is manufactured near the hub. The numerical and experimental results show that hollow blade root has some effect on the static performance. Static pressure of the modified fan is generally the same with that of the datum fan, while, the efficiency curve of the modified fan has a different trend with that of the datum fan. The highest efficiency of the modified fan is 10% greater than that of the datum fan. The orthogonal experimental re- suits of fan noise show that hollow blade root is a feasible method of reducing fan noise, and the maximum value of noise reduction is about 2 dB. The factors affecting the noise reduction of hollow blade root are in the order of importance as follows： hollow blade margin, hollow blade height and hollow blade width. The much smoother pressure distribution of the modified fan than that of the datum fan is the main mechanism of noise reduction of hollow blade root. The research results will provide the proof of the parameter optimization and the structure de- sign for high performance and low noise small axial fans.展开更多
文摘The damage tolerance for pipe/rod bar in the auxiliary power units （APUs） support system is studied. The main objective is to study whether planes can safely land when the fatigue crack appears on the bar. Firstly, the stress intensity factors （K~） of two bar structures are computed, and the iso-stress intensity factor （iso-Kl） model is presented. The model uses the finite element model （FEM） instead of the parameters of material to com- pute the crack propagation. Then, the general relations between Kt vs crack size are obtained for different mate- rials, inner to outer diameter ratios （D^n/Dout） and external crack propagation angles （0）. Finally, the FEM anal- ysis results are input to the ANSYS parametric design language（ANSYS-APDL） software. And the fatigue life of damaged bar is estimated under the condition of loading spectrum.
基金the Research Fund for the Doctoral Program of Higher Education(20010055013)
文摘In this paper we focus ourselves on the positive cone of the locally solid Riesz spaces to characterize the fundamentality. From one example the article indicates that the fundamentality of the locally solid Riesz space is independent from the Lebesgue property.
文摘Stiffening-ribbed-hollow-pipe cast-in place reinforced concrete girderless floor is a new-style hollow girderless floor system. Model experimental researches of simply-supported floor and four-corners bearing floor have been done on this new kind of floor system in this paper. The experiment results show that the floor system has good mechanical property such as high bearing capacity, big rigidity and good tensility. A theoretical method is presented in this paper that the stiffening-ribbed-hollow-pipe girderless floor can be analyzed by being converted equivalently to orthotropic solid slab. It is indicated that the method is correct and reasonable according to the contrast between theoretical calculated results and experimental measured results. The theoretical results coincide with the measured results well.
文摘A LM-2F launch vehicle lifted off from the Jiuquan Satellite Launch Center at22：04 Beijing time on September 15,putting China’s first space laboratory Tiangong 2 into space.575 seconds after the liftoff,Tiangong 2 separated from the carrier rocket and entered its preset orbit.The launch achieved complete success.
基金Supported by the National Basic Research Program of China(No.2012CB026000)the Beijing Education Commission Special Fund andDoctoral Degree Fund(No.20110010110009)
文摘The centrifugal air compressor outlet pipeline vibration was not decreased after barrel viscous dampers were installed in a petrochemical plant in Tianjin.A pipeline-damper experiment apparatus was built for studying the influence factors of the barrel viscous damper and pipe hoop in pipeline vibration reduction.The performance of the damper under different frequency and amplitude was researched respectively,the results showed that damping effect dependsed mainly on frequency and was not related to amplitude.Damper will fail when its vibration frequency exceeds its limit working frequency which was 40 Hz in test.The mechanical properties and energy dissipation were analyzed by using the Maxwell model,which explains experimental results well.According to damping effect and calculation of stiffness with ANSYS in different hoop width,hoop stiffness should match pipe stiffness and keep uniform along transfer path.Damping effect will get worse when local stiffness is too small or too large.Finally,the outlet pipeline vibration was decreased by 70%after using appropriate pipe hoop width and replacing the original damping liquid.
基金supported by National Natural Science Foundation of China(No.51249003,No.51006090)Major Special Project of Technology Office in Zhejiang Province(No.2011C16038,No.2011C11073)
文摘To reduce the influence of adverse flow conditions at the fan hub and improve fan aerodynamic performance, a modification of conventional axial fan blades with numerical and experimental investigation is presented. Hollow blade root is manufactured near the hub. The numerical and experimental results show that hollow blade root has some effect on the static performance. Static pressure of the modified fan is generally the same with that of the datum fan, while, the efficiency curve of the modified fan has a different trend with that of the datum fan. The highest efficiency of the modified fan is 10% greater than that of the datum fan. The orthogonal experimental re- suits of fan noise show that hollow blade root is a feasible method of reducing fan noise, and the maximum value of noise reduction is about 2 dB. The factors affecting the noise reduction of hollow blade root are in the order of importance as follows： hollow blade margin, hollow blade height and hollow blade width. The much smoother pressure distribution of the modified fan than that of the datum fan is the main mechanism of noise reduction of hollow blade root. The research results will provide the proof of the parameter optimization and the structure de- sign for high performance and low noise small axial fans.
