回转曲面的可展切曲面

论文系统地提出了构造回转曲面的可展切曲面及它们间映射分析的理论与方法,建立了回转曲面可展切柱面和可展切锥面的数学模型以及曲面间的映射关系。根据回转曲面及其可展切曲面间微分长度比的理论分析,推出了映射中极值映射曲线和等距映射曲线的微分方程,通过整体和局部的变形分析,可以准确地掌握回转曲面与其可展切曲面间映射中的变形情况。     

曲面片的可展性能及其应用

通过对曲面片可展性能及其应用的研究，在文献[1]的基础上更准确地给出了可展度定量度量曲面片可展性能的概念和方法，同时给出了可展角在不可展曲面近似展开中的应用，一方面可以在曲面展开之前估计近似展开的误差，从而合理选择展开范围，另一方面，基于最佳展开基点均匀分割曲面片可展度的假设，实现了近似展开中最佳展开基点的选取。     

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。     

不可展回转曲面近似展开的精度分析

本文通过对不可展曲面近似展开的整体及局部的误差分析，准确地掌握曲面近似展开的变形规律。为提高展开样板的精度提供了理论依据，本文提出的分析方法对一般规则的曲面近似展开的精度分析也是适用的。     

斜等距曲面及其性质

详细介绍了斜等距曲面的概念及相关公式,证明了锥面和切线曲面的斜等距曲面具有有一些主要性质。     

基于映射理论的曲面雕塑技术

本文描述了一种建立在映射基础上的曲面雕塑技术，给出了相应的理论推导和实验图形。任意曲面的雕塑造型一直是图形学中的一个难，久，这里提出的映射方法易于实现，且保持曲面原有的几何属性及其数学上的严密性，这种数据场的映射造型技术可以实现许多复杂的形体造型，如古董、艺术、人体模型等等，更重要的是通过这种数据场变化对形体的作用及其运动过程的控制或显示起到很好的效果。     

考虑弹性变形的可展杆系结构展开分析

为了保证空间可展结构可靠运行,在展开过程分析中需同时考虑机构运动和弹性变形。首先建立可展杆系结构展开分析的基础方程式,然后基于广义逆矩阵的理论提出了空间可展杆系结构机构运动与弹性变形的混合分析新方法,解决了机构运动与弹性变形的耦合问题,取得了较好的展开分析精度。与传统的柔性多体动力学方法相比,其优点是建模简单,能够有效地跟踪大型可展杆系结构的复杂运动。编制了仿真程序进行了算例分析,验证了分析方法的有效性。     

复杂曲面铣削加工变形误差分析及切痕测量仪器开发

随着航空航天、国防等领域的装备制造要求不断提高,一大批具有复杂曲面且制造精度要求高的零件逐渐涌现.复杂曲面的加工能力已经成为检验五轴数控机床加工性能的重要指标.S形检验试件作为一种具有复杂曲面的典型试件,在其加工过程中,试件表面往往存在一定量的弹性变形误差.文章基于S试件,提出一种结合机床综合刚度的复杂曲面铣削受力变形...     

曲面映射法生成等残留环切加工刀具轨迹

在数控加工中，对组合曲面的高速加工变得越来越重要。高速加工是一种高质量和高效率的制造技术，但是传统的刀具轨迹生成方法并不能满足高速加工的需要。曲面映射法是依据加工后零件表面材料余量呈现“等残留高度”的要求，设计的一种生成空间等距环切加工刀具轨迹的新方法。该方法巧妙地将三维曲面简化为二维平面进行处理，避免了对曲面的复杂计算，解决了用投影法不能处理竖直面或曲面竖直区域的问题。     

Laser surface mapping of a canister closure weld

Laser surface mapping of a canister closure weld provided data that was used to generate three-dimensional images of the weld failure. These images were invaluable in that they allowed people who did not have access to the canister to see the anomaly in great detail. This aided in the scientific examination while reducing exposure to the radiologically contaminated canister. Precise measurements from the surface maps provided useful information about the location of weld features that were used in the examination of the weld failure. Laser surface mapping proved to be a powerful addition to the nondestructive examination tools available for surface phenomena.     

基于HHT变换的超光滑加工表面谱分析

Hilbert-Huang变换是最新发展起来的处理非线性非平稳信号的时频分析方法。其基本的实现分为两步,多分辨经验模态分解和瞬时频率的求解,随后可以获得信号的时—频谱。这种方法的关键部分是多分辨经验模态分解,任何复杂的信号都可以分解为有限数目并且具有一定物理意义的固有模态函数。本文针对表面粗糙度用HHT进行了分析,得出相应结论,对加工有一定的指导意义。     

The generalized Weierstrass system and an application to the study of deformations of surfaces by means of integrable hierarchies

Generalized Weierstrass representations can be used to investigate deformations of surfaces under the action of integrable hierarchies. It will be shown that the generalized Weierstrass representation of Konopelchenko leads to a linear system in a single independent space variable in the case of surfaces of revolution. This result is combined with a second linear problem with an unknown second matrix in terms of a parameter. It is then shown how an integrable hierarchy can be obtained. Solutions to this hierarchy generate deformations which preserve the surface-inducing means of generalized Weierstrass representation.     

Elasticity solution for vibration of 2‐D curved beams with variable curvatures using a spectral‐sampling surface method

An accurate spectral‐sampling surface method for the vibration analysis of 2‐D curved beams with variable curvatures and general boundary conditions is presented. The method combines the advantages of the sampling surface method and spectral method. The formulation is based on the 2‐D elasticity theory, which provides complete accuracy and efficiency for curved beams with arbitrary thicknesses and variable curvatures because no other assumptions on the deformations and stresses along the thickness direction are introduced. Specifically, a set of non‐equally spaced sampling surfaces parallel to the beam's middle surface are primarily collocated along the thickness direction, and the displacements of these surfaces are chosen as fundamental beam unknowns. This fact provides an opportunity to derive elasticity solutions for thick beams with a prescribed accuracy by selecting sufficient sampling surfaces. Each of the fundamental beam unknowns is then invariantly expanded as Chebyshev polynomials of the first kind, and the problems are stated in variational form with the aid of the penalty technique and Lagrange multipliers, which provide complete flexibility to describe any arbitrary boundary conditions. Finally, the desired solutions are obtained by the variational operation. Copyright © 2016 John Wiley & Sons, Ltd.     

Application of a stereometric structural analysis for an evaluation of surface and for a forecast of the wear of endoprothesis acetabular cups

To improve the resistance to wear and permanent deformation of polyethylene operating in a polymer/metal friction couple, initial plastic deformation of the polyethylene and its electron irradiation was applied. This contributed to a change of the polymer structure, visible already while machining when the sample surfaces were being prepared for a tribological test. The study shows that the interactions that shape the structure of polyethylene, at the same time cause adequate changes to the stereometric structure of its surface. The parameters of surface microgeometry characterize the future tribological behavior of polyethylene during its operation in a friction couple. It has been shown that an analysis of stereometric parameters may constitute the first projection of polymer wear resistance.     

Nonlinear analysis and damage monitoring of a one-sided patch repair with delamination

A simple analytical model using beam theory is developed to study a one-sided patch structure with delamination, considering the effect of large deflection and thermal stress. The method is based on the concept of equivalent delamination, which is analytically defined and employed to describe delay in load transfer between patch and parent plate with eccentrically aligned neutral axes. The analytical model has closed form solutions and good agreement with nonlinear finite element analysis (FEA) as well as experimental results is shown. The relation between the delamination propagation and the strains at monitoring locations is derived and feasibility of delamination monitoring based on surface strains is analytically demonstrated.     

Workspace-constrained optimal design of three-degrees-of-freedom parallel manipulators with minimum parasitic motions by integrating interval analysis,region mapping and differential evolution

Three-degrees-of-freedom (3-DOF) parallel manipulators have many advantages such as simple structure, fewer actuators, and lower maintenance cost. However, parasitic motions may degrade the positioning accuracy of the platforms. In order to design 3-DOF parallel manipulators which can fulfil specified workspace requirements and exhibit minimum parasitic motions, the design problem is formulated into a minimax problem with workspace constraints. Then, an interval-based method is exploited to determine the feasible solution set which is derived as a union of many scattered parameter intervals (boxes). Then, a new approach based on region mapping and a powerful optimizer (namely differential evolution) is proposed to solve the optimization problem over scattered search regions. Benchmark tests show the superiority of the proposed approach. Then, the approach and interval analysis are used to solve a real-world design problem involving a 3-DOF manipulator. Numerical results demonstrate the effectiveness and advantages of the proposed design method.     

The study of the interactions between graphene and Ge(001)/Si(001)

The interaction between graphene and germanium surfaces was investigated using a combination of microscopic and macroscopic experimental techniques and complementary theoretical calculations.Density functional theory (DFT) calculations for different reconstructions of the Ge(001) surface showed that the interactions between graphene and the Ge(001) surface introduce additional peaks in the density of states,superimposed on the graphene valence and conduction energy bands.The growth of graphene induces nanofaceting of the Ge(001) surface,which exhibits well-organized hill and valley structures.The graphene regions covered by hills are of high quality and exhibit an almost linear dispersion relation,which indicates weak graphene-germanium interactions.On the other hand,the graphene component occupying valley regions is significantly perturbed by the interaction with germanium.It was also found that the stronger graphene-germanium interaction observed in the valley regions is connected with a lower local electrical conductivity.Annealing of graphene/Ge(001)/Si(001) was performed to obtain a more uniform surface.This process results in a surface characterized by negligible hill and valley structures;however,the graphene properties unexpectedly deteriorated with increasing uniformity of the Ge(001) surface.To sum up,it was shown that the mechanism responsible for the formation of local conductivity inhomogeneities in graphene covering the Ge(001) surface is related to the different strength of graphene-germanium interactions.The present results indicate that,in order to obtain high-quality graphene,the experimental efforts should focus on limiting the interactions between germanium and graphene,which can be achieved by adjusting the growth conditions.     

Three-dimensional analysis of the interaction between a matrix crack and nanofiber

A three-dimensional study of interactions between a matrix crack and nanofibers is undertaken. The nanofibers considered in the study have a hollow structure and a certain wall thickness. The analytical study is performed by considering a penny-shaped crack propagating towards a pair of nanofibers placed symmetrically with respect to the crack. The three-dimensional study accounts for the influence of nanofiber hollow geometry and outer diameter on crack energetics. The effect of the mismatch between the elastic properties of nanofiber and matrix is also considered. Finally, the influence of the interphase between nanofiber and matrix on crack energetics is investigated. Energy release rates along the crack front of the penny-shaped crack are computed to understand the nature of the toughening effect of nanofibers. The results of the study indicate a significant influence of nanofiber wall thickness and longitudinal modulus on crack energetics. Also, the presence of an interphase between a nanofiber and matrix seems to alter the crack energetics considerably. Finally, the results of the study indicate that nanofiber diameter may have a positive or negative effect on resistance to crack propagation depending on nanofiber wall thickness.     

The nature of the ordering of atoms in a melt and the surface properties of simple eutectic systems

Using the models reconstructed from the experimental structure factor curves by the reverse Monte-Carlo and Voronoy-Delaunay methods the local atomic structures of the Sn-Ge, Ag-Ge, and Ni-C simple eutectic systems has been analyzed. It has been found that the nature of the atom ordering in melts is responsible not only for the melt bulk properties, but for its surface properties (surface tension, wetting) as well. Clusters that form from atoms of the same sort in melts and whose binding energy inside the clusters exceeds the binding energy between the atoms of a solvent and a cluster, exhibit the surface activity in the melt, which explains the extremes in isotherms of the density and surface tension of the melts. Clusters with a chemical ordering of atoms patterned after the Me₃C electronic compound revealed in the Ni-C and Ag-Ge systems indicate that the equilibrium phase diagrams of these systems at high pressures transform from diagrams of a simple eutectic type to diagrams with a compound, i.e. an increase in pressure contributes to the metallization of bonds in a melt.