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111.
为分析在激光冲击波作用下AZ31B镁合金薄板背面的动态响应,采用聚偏氟乙烯贴片传感器与数字示波器对强激光诱导的冲击波进行测量,得到压电波形,结合冲击波的传播特性,对弹塑性双波的传播规律进行了研究。结果表明:激光诱导的材料动态响应是快速的;压电波形图反映出的弹性前驱波与塑性加载波传播到靶材背面的时间与理论时间相符;弹性前驱波能量小引发的波形振幅较小,紧随着的塑性加载波能量大并引起较大振幅波动,弹塑性双波卸载过程与紧接着的加载过程导致了压电信号的波动振幅提高。 相似文献
112.
Nonlinear dynamic characteristics and optimal control of a giant magnetostrictive film-shaped memory alloy composite plate subjected to in-plane stochastic excitation 下载免费PDF全文
The nonlinear dynamic characteristics and optimal control of a giant magnetostrictive film(GMF)-shaped memory alloy(SMA) composite plate subjected to in-plane stochastic excitation are studied. GMF is prepared based on an SMA plate, and combined into a GMF–SMA composite plate. The Van der Pol item is improved to explain the hysteretic phenomena of GMF and SMA, and the nonlinear dynamics model of a GMF–SMA composite cantilever plate subjected to in-plane stochastic excitation is developed. The stochastic stability of the system is analyzed, and the steady-state probability density function of the dynamic response of the system is obtained. The condition of stochastic Hopf bifurcation is discussed, the reliability function of the system is provided, and then the probability density of the first-passage time is given. Finally, the stochastic optimal control strategy is proposed by the stochastic dynamic programming method.Numerical simulation shows that the stability of the trivial solution varies with bifurcation parameters, and stochastic Hopf bifurcation appears in the process; the system’s reliability is improved through stochastic optimal control, and the firstpassage time is delayed. A GMF–SMA composite plate combines the advantages of GMF and SMA, and can reduce vibration through passive control and active control effectively. The results are helpful for the engineering applications of GMF–SMA composite plates. 相似文献
113.
Droplets of Co-16%Cu and Co-71.6%Cu peritectic alloys were solidified during containerless processing in a 3_m drop tube. The microstructures of Co-16%Cu alloy droplets were characterized by dendritic or equiaxed α-Co phase with a small amount of Cu-rich solid solution distributed on α-Co phase boundaries. Two thresholds of droplet diameter were observed for Co-16%Cu alloy at which "equiaxed-dendritic-equiaxed" morphological transitions occur to primary α-Co phase. This conspicuous refinement of primary α-Co grains results from the fragmentation of α-Co dendrites caused by recalescence effect. For Co-71.6%Cu alloy, the primary α-Co phase forms as coarse columnar dendrites in large droplets and equiaxed dendrites in small droplets. Theoretical calculations indicate that Marangoni migration contributes more to the growth of disperse Co-rich spheres by stimulating collision and coalescence than Stokes motion caused by the residual gravity in the falling Co-71.6%Cu alloy droplets. 相似文献
114.
Spin‐polarized density functional theory is used to study the TiO2 terminated interfaces between the magnetic Heusler alloys Co2Si (M = Ti, V, Cr, Mn, and Fe) and the non‐polar band insulator SrTiO3. The structural relaxation at the interface turns out to depend systematically on the lattice mis‐ match. Charge transfer from the Heusler alloys (mainly the M 3d orbitals) to the Ti dxy orbitals of the TiO2 interface layer is found to gradually grow from M = Ti to Fe, resulting in an electron gas with increasing density of spin‐polarized charge carriers. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
115.
D. Dong 《Applied Surface Science》2009,255(15):7051-7055
Dispersible SiO2 nanoparticles were co-deposited with electroless Ni-P coating onto AISI-1045 steel substrates in the absence of any surfactants in plating bath. The resulting Ni-P/nano-SiO2 composite coatings were heat-treated for 1 h at 200 °C, 400 °C, and 600 °C, respectively. The hardness and wear resistance of the heat-treated composite coatings were measured. Moreover, the structural changes of the composite coatings before and after heat treatment were investigated by means of X-ray diffraction (XRD), while their elemental composition and morphology were analyzed using an energy dispersive spectrometer (EDS) and a scanning electron microscope (SEM). Results show that co-deposited SiO2 particles contributed to increase the hardness and wear resistance of electroless Ni-P coating, and the composite coating heat-treated at about 400 °C had the maximum hardness and wear resistance. 相似文献
116.
Magnetic alloy(MA)-loaded cavities have been widely used in compact proton and heavy-ion synchrotrons,and the MA core is the key issue in their development.Chinese-produced MA has never yet been adopted as core material for an MA-loaded cavity.To use Chinese-produced MA as the core material,it is necessary to study its properties,and compare with MA material produced elsewhere.In this paper,the properties of several MA cores made of Chinese-produced material are measured.Based on the measured results,a schematic design is produced for a cavity which could obtain 1 kV gap voltage with less than 1.5 kW power dissipation in the frequency range of0.5-7 MHz.The difference between resonant frequencies obtained from simulation and analytical results is less than10%. 相似文献
117.
Zubair Ahmad Tianyu Ma Shan TaoMi Yan 《Journal of magnetism and magnetic materials》2012,324(8):1534-1538
The Fe63B23Nd7Y3Nb3Cr1 nanocomposite magnets in the form of sheets have been prepared by copper mold casting technique. The phase evolution, crystal structure, microstructural and magnetic properties have been investigated in the as-cast and annealed states. The as-cast sheets show magnetically soft behaviors which become magnetically hard by thermal annealing. The optimal annealed microstructure was composed of nanosize soft magnetic α-Fe (19-29 nm) and hard magnetic Nd2Fe14B (45-55 nm) grains. The best hard magnetic properties such as intrinsic coercivity, jHc of 1119 kA/m, remanence, Br of 0.44 T, magnetic induction to saturation magnetization ratio, Mr/Ms=0.61 and maximum energy product, (BH)max of 55 kJ/m3 was obtained after annealing at 680 °C for 15 min. The annealing treatment above 680 °C results in non-ideal phase grains growth, which degrade the magnetic properties. 相似文献
118.
119.
Copper (titanium) [Cu(Ti)] films with low titanium (Ti) concentration were found to form thin Ti-rich barrier layers at the
film/substrate interfaces after annealing, which is referred to as self-formation of the barrier layers. This Cu(Ti) alloy
was one of the best candidates for interconnect materials used in next-generation ultra-large-scale integrated (ULSI) devices
that require both very thin barrier layers and low-resistance interconnects. In the present paper, in order to investigate
the influences of annealing ambient on resistivity and microstructure of the Cu alloys, the Cu(7.3at.%Ti) films were prepared
on the SiO2 substrates and annealed at 500°C in ultra-high vacuum (UHV) or argon (Ar) with a small amount of impurity oxygen. After annealing
the film at 500°C in UHV, the resistivity was not reduced below 16 μΩ-cm. Intermetallic compounds of Cu4Ti were observed to form in the films and believed to cause the high resistivity. However, after subsequently annealing in
Ar, these compounds were found to decompose to form surface TiO
x
and interfacial barrier layers, and the resistivity was reduced to 3.0 μΩ-cm. The present experiment suggested that oxygen
reactive to titanium during annealing played an important role for both self-formation of the interfacial barrier layers and
reduction of the interconnect resistivity. 相似文献
120.
通过改变溅射功率以磁控溅射法制备了Cu/Cr合金催化剂,研究了化学气相沉积法制备的碳纳米管(CNTs)作为大电流密度场发射阴极的场发射性能。采用扫描电镜和场发射测试仪分别对不同功率催化剂制备的CNTs进行了形貌及性能分析。结果表明,根据溅射功率与催化剂颗粒的关系,可以通过调节溅射功率改变CNTs的长径比及密度,在250WCu/Cr催化剂制备的CNTs薄膜具备了良好的场发射性能,阴极电子发射的开启电场仅为1.47V/μm,当电场为3.23V/μm,发射电流密度可高达3259μA/cm2。 相似文献