微振动环境下反射镜的微转角测量

为了测量微振动环境条件下反射镜的微小转角,根据结构随机振动加速度的频域数据与转角均方根响应的数学关系,提出了一种经济且简单易行的间接测量结构微转角的方法。并且以一个大型反射镜架为例,通过实验分析得到了其在大厅空调运行与关闭微振动环境下镜片的相对转角响应。实验表明,此方法操作简单、测量精度高,具有广阔的应用前景。

一种微转角机构设计

由于陀螺瞄准仪在进行功能测试前,需要对陀螺摆的微小转角与PSD(位置探测器)输出电压值进行标定,因此设计了一种可以模拟陀螺摆微转角的实用机构。这种微转角机构是利用比例弹簧技术和螺纹传动技术来实现陀螺摆转角与PSD输出电压值对应关系的标定。详细介绍了转角机构的工作原理和设计计算方法,经过实际检测,验证了该机构设计的合理性。

纯镁等通道转角微挤压成型工艺及摩擦效应研究

以99.95%的高纯镁为研究对象,借助有限元分析软件DEFORM对等通道转角微挤压(equal channel angular micro pressing,M-ECAP)过程进行数值模拟,优化等通道微挤压(简称M-ECAP)变形的成形工艺,讨论变形过程中的材料流动、挤压载荷变化规律、等效应力应变分布规律、摩擦效应对M-ECAP变形过程的影响。结果表明:试样等效应变趋于均匀,累积应变量增加,晶粒细小且均匀,塑性得到有效提高;随着摩擦因子的增大,载荷逐渐增大,最大等效应变变化不明显、最大等效应力小幅减小。

Modeling and solving for transverse vibration of gear with variational thickness

A analyzed model of gear with wheel hub, web and rim was derived from the Mindlin moderate plate theory. The gear was divided into three annular segments along the locations of the step variations. Traverse displacement, rotation angle, shear force and fiexural moment were equal to ensure the continuity along the interface of the wheel hub, web and rim segments. The governing differential equations for harmonic vibration of annular segments were derived to solve the gear vibration problem. The influence of hole to diameter ratios, segment thickness ratios, segment location ratios, Poisson ratio on the vibration behavior of stepped circular Mindlin disk were calculated, tabletted and plotted. Comparisons were made with the frequencies arising from the presented method, finite elements method, and structure modal experiment. The result correlation among these three ways is very good. The largest error for all frequencies is 5.46%, and less than 5% for most frequencies.

Combined effects of ECAP and subsequent heating parameters on semi-solid microstructure of 7075 aluminum alloy

The combined effects of equal channel angular pressing (ECAP) and subsequent heating to a semi-solid temperature on the microstructural characteristics of the 7075 aluminum alloy were investigated. The microstructure is influenced by several parameters including the number of ECAP passes, ECAP route, consequent heating temperature, and holding time. The effects of these parameters on the microstructural characteristics including grain size and shape factor of the 7075 aluminum alloy were studied using experimental tests and Taguchi method. The results indicate that five-pass ECAP in route BA and subsequent isothermal holding at 630 °C for 15 min are more appropriate for achieving a semi-solid microstructure. The processing route and holding time have the highest impact on the grain size while the number of ECAP passes and heating temperature have the least impact on the grain size. Meanwhile, the shape factor is significantly influenced by the processing route, holding time and heating temperature while it is less influenced by the number of ECAP passes.

Relationship Between Differential Interference Angle and Parameter of Experiment in Molecular Beam

Collisional quantum interference （CQI） was observed in the intramolecular rotational energy transfer in the experiment of the static cell, and the integral interference angles were measured. To observe more precise information, the experiment in the molecular beam should be taken,from which the relationship between the differential interference angle and the scattering angle can be obtained. In this paper, the theoretical model of CQI is described in an atom-diatom system in the condition of the molecular beam, based on the first-Born approximation of time-dependent perturbation theory, taking into accounts the long-range interaction potential. The method of observing and measuring correctly the differential interference angle is presented. The changing tendency of the differential interference angle with the impact parameter and relative velocity is discussed. The changing tendencies of the differential interference angle with the parameter of experiment in the molecular beam, including the impact parameter and the velocity are discussed. This theoretical model is important to understand or perform the experiment in the molecular beam.

Stereodynamics of O（^3P）＋H2 at Scattering Energies of 0.5, 0.75, and 1.0 eV

Quasiclassical trajectory calculation of the title reaction O（^3P）＋H2→OH＋H at three different scattering energies of 0.5, 0.75, and 1.0 eV on the lowest electronic potential energy surface 1^3A＂ has been done. Distribution P（θr） of polar angles between the relative velocityk of the reactant and rotational angular momentum vector j＇ of the product, distribution P（φr） of the azimuthal as well as dihedral angles correlating k-k＇-j＇, 3-dimensional distri-bution, and polarization-dependent differential cross sections （PDDCSs）dependent upon the scattering angle of the product molecule OH between the relative velocity k of the reactant and k＇ of the product at different scattering energies of 0.5, 0.75, and 1.0 eV are presented and discussed.

Influence of the instability of angular velocity of the rotating carrier itself on the stability of silicon micromachined gyroscope

In order to find out the influence of the instability of angular velocity of the rotating carrier itself on the stability of silicon micromachined gyroscope, the digital models for relative error of the high and low damping gyroscope's output signal are given respectively, based on the motion equations of the silicon micromachined gyroscope. Theory proves that the output signal error of the silicon micromachined sensor is mainly caused by the instability of damping factor and the angular velocity of the rotating carrier itself. The experiment result indicates that the error of proportionality coefficient of output voltage which is caused by the instability of the angular velocity of the rotating carrier itself reaches to 4.1 %. Theoretical demonstration and experimental verification show that the instability of angular velocity of the rotating carrier itself has an important effect on the stability of low damping silicon micromachined gyroscope.

Microstructural evolution and mechanical properties of AZ31 Mg alloy fabricated by a novel bifurcation-equal channel angular pressing

In this work,a novel type of short-process deformation technology of Mg alloys,bifurcation-equal channel angular pressing(B-ECAP),was proposed to refine grain and improve the basal texture.The cylindrical billets were first compressed into the die cavity,then sequentially flowed downward through a 90°corner and two 120°shear steps.The total strain of B-ECAP process could reach 3.924 in a single pass.The results of microstructure observation showed that DRX occurred at upsetting process in the die cavity and completed at position D.The grains were refined to 6.3μm at being extruded at 300℃ and grew obviously with the extrusion temperature increase.The shear tress induced by 900 corner and two 120°shear steps resulted in the basal poles of most grains tilted to extrusion direction(ED)by±25°.Compared with the original billets,the extruded sheets exhibited higher yield strengths(YS),which was mainly attributed to the grain refinement.The higher Schmid factor caused by ED-tilt texture resulted in a fracture elongation(FE)more than that of the original bar in ED,while was equivalent to that in transverse direction(TD).As the extrusion temperature increased,the variation of UTS and YS in ED and TD decreased gradually without ductility obviously decrease.

VARIABILITY SETS AND HAMILTON SEQUENCES

This paper studies extremal quasiconformal mappings. Some properties of the variability set are obtained and the Hamilton sequences which are induced by point shift differentials are also discussed.