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| 1 | Development of a Bird-like Flapping-wing Aerial Vehicle with Autonomous Take-off and Landing Capabilities显示文摘The lack of autonomous take-off and landing capabilities of bird-like flapping-wing aerial vehicles(BFAVs)seriously restricts their further development and application.Thus,combined with the current research results on the autonomous take-off and landing technology of unmanned aerial vehicles,four types of technologies are studied,including jumping take-off and landing technology,taxiing take-off and landing technology,gliding take-off and landing technology,and vertical take-off and landing(VTOL)technology.Based on the analytic hierarchy process(AHP)-comprehensive evaluation method,a fuzzy comprehensive evaluation model for the autonomous take-off and landing scheme of a BFAV is established,and four schemes are evaluated concretely.The results show that under the existing technical conditions,the hybrid layout VTOL scheme is the best.Furthermore,the detailed design and development of the prototype of a BFAV with a four-rotor hybrid layout are carried out,and the vehicle performance is tested.The results prove that through the four-rotor hybrid layout design,the BFAV has good autonomous take-off and landing abilities.The power consumption analysis shows that for a fixed-point reconnaissance mission,when the mission radius is less than 3.38 km,the VTOL type exhibits longer mission duration than the hand-launched type. | Dongfu Ma Bifeng Song Zhihe Wang Jianlin Xuan Dong Xue | 2021 | Journal of Bionic Engineering2021，18，6： | 1 |
| 2 | In Situ Investigation of Si-Poisoning Effect in Al-Cu-Si Alloys Inoculated by Al-5Ti-1B显示文摘In situ synchrotron X-radiography was carried out on Al-13 Cu and Al-13 Cu-7 Si alloys with and without addition of Al-5 Ti-1 B master alloy.The effects of Si content on grain growth and the solute-suppressed nucleation zone(SSNZ)were quantitatively studied.The average grain size can be refined to 164μm of Al-13 Cu alloy inoculated by Al-5 Ti-1B.After addition of 7%Si content,a large number of TiB 2 sites in the melt lost the inoculating ability due to'Si poisoning.'The radius of the dendrite tip curvature of Al-13 Cu is more than two times as large as that of Al-13 Cu-7 Si.The sharper tip is able to disperse the solute more effectively and thus grains can grow more rapidly.This causes that the dendrite arm growth rate with addition of 7%Si solute is about 2.6 times that of no Si addition.In addition,the solute enrichment in the SSNZ of Al-13 Cu is faster,and the area change of SSNZ is slower than that of Al-13 Cu-7 Si.Thus more nucleation sites in the SSNZ cannot be activated with addition of Si.This study will shed light on the understanding of Si poisoning in casting Al-Cu-Si alloys. | Yiwang Jia Dongfu Song Nan Zhou Kaihong Zheng Yanan Fu Da Shu | 2022 | Acta Metallurgica Sinica(English Letters)2022，35，1： | 0 |
| 3 | Nucleation and growth of Fe-rich phases in Al-5Ti-1B modified Al-Fe alloys investigated using synchrotron X-ray imaging and electron microscopy显示文摘Plate-like Fe-rich intermetallic phases directly influence the mechanical properties of recycled Al alloys;thus, many attempts have been made to modify the morphology of these phases. Through synchrotron X-ray imaging and electron microscopy, the underlying nucleation and growth mechanisms of Fe-rich phases during the solidification of Al-5 Ti-1 B-modified Al-2 Fe alloys were revealed in this study. The results showed that the Al-5 Ti-1 B grain refiner as well as the applied pressure both resulted in reduction of the size and number of primary Al_(3)Fe phases and promoted the formation of eutectic Al_(6)Fe phases.The tomography results demonstrated that Al-5 Ti-1 B changed the three-dimensional(3 D) morphology of primary Fe-rich phases from rod-like to branched plate-like, while a reduction in their thickness and size was also observed. This was attributed to the fact that Ti-containing solutes in the melts inhibit the diffusion of Fe atoms and the Al_(3)Fe twins produce re-entrant corner on the twin boundaries along the growth direction. Moreover, the TiB_(2) provides possible nucleation sites for Al_6Fe phases. The nucleation mechanism of Fe-rich phases is discussed in terms of experimental observations and crystallography calculations. The decrease in the lattice mismatch between TiB_(2) and Al_(6)Fe phases was suggested, which promoted the transformation of Al_(3)Fe to Al_(6)Fe phases. | Yuliang Zhao Weiwen Zhang Dongfu Song Bo Lin Fanghua Shen Donghai Zheng ChunXiao Xie Zhenzhong Sun Yanan Fu Runxia Li | 2021 | Journal of Materials Science & Technology2021，，21： | 0 |
| 4 | Influence of Fe-rich phases and precipitates on the mechanical behaviour of Al-Cu-Mn-Fe-Sc-Zr alloys studied by synchrotron X-ray and neutron显示文摘A multiscale methodology using scanning and transmission electron microscope,synchrotron X-ray nano-tomography and micro-tomography,small angle neutron scattering,and in situ synchrotron X-ray diffrac-tion has been used,to reveal the effect of Fe-rich phases and precipitates on the mechanical behaviour of an Al-Cu-Mn-Fe-Sc-Zr alloy.Theα-Al grains size is reduced from 185.1μm(0 MPa)and 114.3μm(75 MPa)by applied pressure.Moreover,it has been demonstrated that suitable heat treatments modify the 3D morphology of Fe-rich phases from interconnected to a disaggregated structure that improves the mechanical properties of the alloy.The size and morphology evolution of fine precipitates under differ-ent ageing temperature and time are revealed.At ageing temperature of 160℃,the precipitates change from GP zones toθ’(around 75 nm in length)with ageing time increasing from 1 h to 24 h;the Vick-ers hardness increases from 72.0 HV to 110.7HV.The high ductility of the Sc,Zr modified Al-Cu alloy is related to the complex shape and the loss of interconnectivity of the Fe-rich particles due to the heat treatment.The evolution of the crystal lattice strains inα-Al,andβ-Fe calculated during tensile test us-ing in-situ synchrotron X-ray diffraction corroborates the influence of the microstructure in the ductility of the modified alloy. | Yuliang Zhao Dongfu Song Shengchuan Wu Shunfu Xie Haoliang Wang Mengmeng Wang Weiwen Zhang Zhenzhong Sun Yubin Ke Shanfeng Wang Wanxia Huang Ricardo Fernández | 2023 | Journal of Materials Science & Technology2023，，27： | 0 |
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