两端为任意椭圆的盘旋面展开CAD

本文提出用切平面遥近法构造两端为任意椭圆的盘旋面，介绍了这种曲面展开的计算原理和绘制方法，进而提供了利用该方法设计的绘图程序所绘制的展开图例。     

自由曲面最佳展开基点的几何属性

在分析自由曲面一般展开方法的基础上,提出了近似展开样板误差的评价方法。证实了展开基点对曲面近似展开结果具有较大的影响,并证明了最佳展开基点位置存在的客观性。进而利用等误差曲线的生成,实现了曲面片最佳展开基点位置的可视化,通过实验,得出了最佳展开基点位置与曲面片几何属性间的关系。最后通过曲面片的近似展开,验证了所得结论的正确性,也给出了最佳展开基点的搜索方法。     

曲面片的可展度及其最佳展开基点

本文通过对不可展曲面近似展开误差机理的分析研究，提出了曲面片最佳展开基点和曲面片可展度的概念和实现方法。     

提高曲面近似展开精度的方法与实现

通过对不可展曲面近似展开精度的研究，提出了根据曲面曲率的大小对曲面自动进行网格划分，通过对综合展开误差数据场进行数据拟合来选取最优展开基点，基于空间曲面与其展开图间近似的等距变换关系进行展开样形的误差矫正等3种方法，这几种方法的实现在不同程度上有效地减小了曲面的近似展开误差，提高了曲面的近似展开精度。     

基于Pro／E的钣金展开方法初探

通过对钣金件加工中Pro／E展开方法与传统展开方法的比较分析,阐明了钣金件Pro／E展开方法的优越性、实用性、经济性,总结了Pro／E钣金展开过程中应注意的事项,为钣金件展开加工提供了一种实用、高效的展开工具。     

回转曲面近似展开的数学模型

通过对不可展回转曲面近似展开方法的研究,得到了回转曲面近似展开,精度分析和误差矫正的数学模型。在回转曲面构件的金属加工中,该模型可作为展开样板计算机辅助设计与 基本算法。     

偏心大小头展开图的精确计算绘制法

偏心大小头展开图的精确计算绘制法张志发（浙江省工业设备安装公司）１９９３年《安装》第３期介绍了通过进行一些简单计算绘制偏心大小头展开图的方法，即在通过简单计算绘出正大小头展开图的基础上，再进行一些简单计算，绘制偏心大小头展开图的方法。按此方法下料，确...     

大型切割旋转抛物面展开结构的设计

 讨论近年来我们研究的一种特殊的展开结构,并成功设计出这种结构。     

椭圆形封头近似展开

为了更加精确地实现椭圆形封头的模压成型，基于画法几何原理，可将椭圆形封头等分成若干等份，然后取出其中任意一块曲面，建立该曲面边界曲线近似展开的数学模型，并使用Visual LISP语言编写该展开方法的AutoCAD自动绘图程序，从而实现了椭圆形封头展开后边界曲线的计算机自动绘制过程，并且用户可以在该程序中生成的对话框内输入不同的参数值，得到不同的展开曲线。     

航天器可展开支撑杆的研制及其收拢展开特性研究

复合材料豆荚杆是一种质量轻、刚度较大、收拢效率高、展开过程可靠的可展开管状杆结构。本工作对豆荚杆进行优化设计,并对多种豆荚杆试件进行性能测试与评估,选取其中综合性能优异的材料体系研制了2m长豆荚杆样机。利用研制的豆荚杆收展控制机构对豆荚杆的收拢-展开性能进行了测试,结果显示玻璃布/FEB豆荚杆可实现多次收拢-展开,其综合性能可基本满足空间可展开结构的性能需求。     

Solid-solid contacts due to surface roughness and their effects on suspension behaviour

Solid-solid contacts due to microscopic surface roughness in viscous fluids were examined by observing the translational and rotational behaviours of a suspended sphere falling past a lighter sphere or down an inclined surface. In both cases, a roll-slip behaviour was observed, with the gravitational forces balanced by not only hydrodynamic forces but also normal and tangential solid-solid contact forces. Moreover, the nominal separation between the surfaces due to microscopic surface roughness elements is not constant but instead varies due to multiple roughness scales. By inverting the system, so that the heavy sphere fell away from the lighter sphere or the plane, it was found that the average nominal separation increases with increasing angle of inclination of the plane or the surface of the lighter sphere from horizontal; the larger asperities lift the sphere up from the opposing surface and then gravity at large angles of inclination is too weak to pull the sphere back down to the opposing surface before another large asperity is encountered. The existence of microscopic surface roughness and solid-solid contacts is shown to modify the rheological properties of suspensions. For example, the presence of compressive, but not tensile, contact forces removes the reversibility of sphere-sphere interactions and breaks the symmetry of the particle trajectories. As a result, suspensions of rough spheres exhibit normal stress differences that are absent for smooth spheres. For the conditions studied, surface roughness reduces the effective viscosity of a suspension by limiting the lubrication resistance during near-contact motion, and it also modifies the suspension microstructure and hydrodynamic diffusivity.     

Wave slam on a sphere penetrating a free surface

Summary The problem of vertical motion of a sphere across an oscillating free surface is analysed by assuming the fluid to be inviscid and the free surface to be an equipotential surface. New analytical solutions for the added-mass coefficients of a double spherical bowl are derived. These are used in the derivation of the drag coefficient of a sphere during vertical entry and of the slamming coefficient of a fixed sphere which is exposed to wave action. An additional important parameter in hydroballistics is the wetting factor of a sphere penetrating a free surface for which a new analytic solution is also derived in this paper. A comparison between some experimental data and the analytic expressions for the slamming coefficient and the wetting factor, shows good agreement between theory and measurements.This work was sponsored by the Office of Naval Research, under contract N00014-76-C-0026, and by the National Science Foundation, under contract CME-79-21244.     

Finite element simulation of the thermal conductivity of perforated hollow sphere structures (PHSS): Parametric study

This paper investigates the thermal properties of a new type of hollow sphere structures. For this new type, the sphere shell is perforated by several holes in order to open the inner sphere volume and surface. The effective thermal conductivity of perforated sphere structures in a primitive cubic arrangement is numerically evaluated for different hole diameters and different dimensions of the joining elements.     

Braking of a “Magnetized” Sphere in a Hypersonic Rarefied Plasma Flow

The dependence of the drag coefficient of a “magnetized” (with a self-generated magnetic field) sphere on the ratio of the magnetic pressure to the gas dynamic pressure in a hypersonic rarefied plasma flow is determined experimentally. The dependences are obtained for a wide range of angles between the vectors of the incident flow velocity and the magnetic field, as well as between the velocity vectors of the incident hypersonic plasma flow and a subsonic plasma jet injected from the surface of the sphere. It is shown that the injection of a subsonic plasma jet from the surface of a “magnetized” sphere in a hypersonic rarefied plasma flow increases its drag coefficient by several times in comparison with an “unmagnetized” sphere.     

Condensation of steam on a vertical tube in a granulated material

The heat transfer enhancement was studied during condensation of steam on a chilled vertical surface of a tube packed into a granulated material with different contact angles of wetting. The dimensionless values of heat transfer at condensation on a surface in filling, obtained for a vertical tube in the range of Reynolds numbers from 70 up to 400, exceed Nu* values for a smooth tube by the factor of 2–3. The intensification of heat transfer on a vertical tube, housed in a granulated layer, is conditioned by the several interdependent phenomena: 1 — capillary ascent of some liquid near the meniscuses, and as a consequence, reduction of the mean film thickness; 2 — burble of a film at the points of sphere contact with a surface of condensation at Re>10; 3 — removal of some film liquid by a granulated layer; accompanied by simultaneous film burble at the points of sphere contact with a cooling surface at Re>83. Results of the current research can be used for the development of heat exchanging devices under the conditions of microgravitation.     

Motion of a solid sphere in a general flow near a plane boundary at zero Reynolds number

It is demonstrated how the hydrodynamic force and moment of force acting on a solid sphere may be calculated when it is placed at rest at an arbitrary position in a two dimensional flow at zero Reynolds number in which the region of flow is bounded by either an undeformable planar free surface or by a plane solid wall. The results so obtained are used to calculate the motion of a freely moving solid sphere in an asymmetric vortex in the presence of an underformable free surface. It is seen that the sphere, depending on the direction of the undisturbed flow, will either spiral into or out of the vortex. This implies that when a dilute suspension of such spherical particles undergoes such a vortex motion in the presence of the free surface, the vortex will either fill up with particles from the surrounding flow or become devoid of particles.Deceased, July 31, 1995     

Nonequilibrium effects accompanying condensation at a black sphere

A Monte Carlo simulation is used to make a detailed analysis of the nonequilibrium zone formed near the surface of a condensing sphere. Significant directional anisotropy of the temperature was observed. It was established that the nonequilibrium near an absolutely black sphere is responsible for the difference between the calculated values of the specific mass flow in comparison with the published data obtained assuming little difference between the vapor state at infinity and temperature saturation conditions at the surface of the sphere. Pis’ma Zh. Tekh. Fiz. 25, 43–48 (January 26, 1999)     

Testing aspheric surfaces: simple method with a circular stop

As an extension of the knife-edge test, a noninterferometric method for inspecting circularly symmetric aspheres is proposed in which the test surface is illuminated by a spherical wave. When a small circular stop is placed around the curvature center of the best-fitting sphere, only rays characteristic for the deviation from a perfect sphere remain unobstructed. An image of the tested surface is thereby obtained, showing light and dark regions whose boundaries are correlated to the surface profile, the stop size, and the stop position along the symmetry axis. The experiment has been carried out with a paraboloid.     

Preparation and characterization of optical-functional diblock copolymer brushes on hollow sphere surface via atom transfer radical polymerization

The optical-functional poly(methyl methacrylate)-block-Tb complex diblock copolymer brushes grafted from hollow sphere surface via atom transfer radical polymerization were investigated in this work. A sufficient amount of azo initiator was introduced onto hollow sphere surface firstly. Then the monomer methyl methacrylate was polymerized via surface-initiated reverse atom transfer radical polymerization using azo group modified hollow sphere as initiator. Following, the poly(methyl methacrylate) modified hollow sphere was used as maroinitiator for surface-initiated atom transfer radical polymerization of Tb complex. The samples were characterized by Fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance, gel permeation chromatographer and transmission electron microscopy, respectively. The results indicated that the poly(methyl methacrylate) had grafted from hollow sphere surface and the average diameter of hollow core was about 1 μm. The optical properties of the poly(methyl methacrylate)-block-Tb copolymer modified hollow sphere were also reported.     

三角网格曲面的球面参数化

提出了一种球面参数化三角网格曲面的方法。结合平面凸参数化和球面参数化,计算出封闭网格的切割线边界,网格边界映射到球面的凸区域边界上。然后分别参数化各子网格,最后将三角网格内部点映射到球面上。并用实例验证了此方法的可行性和有效性。