An adaptive mesh-independent numerical integration for meshless local petrov-galerkin method

In this paper, an adaptive numerical integration scheme, which does not need non-overlapping and contiguous integration meshes, is proposed for the MLPG (Meshless Local Petrov-Galerkin) method. In the proposed algorithm, the integration points are located between the neighboring nodes to properly consider the irregular nodal distribution, and the nodal points are also included as integration points. For numerical integration without well-defined meshes, the Shepard shape function is adopted to approximate the integrand in the local symmetric weak form, by the values of the integrand at the integration points. This procedure makes it possible to integrate the local symmetric weak form without any integration meshes (non-overlapping and contiguous integration domains). The convergence tests are performed, to investigate the present scheme and several numerical examples are analyzed by using the proposed scheme.     

The numerical method for the coverage interval determination in the conducted emission measurements

This paper presents a numerical method for the coverage interval determination of the output variable while knowing the probability density functions of two non-dependent input variables. The coverage interval is derived from distribution function. In order to obtain the probability density function of the output variable, which is of mixed distribution type, the numerical combined method is applied, consisted of the Monte Carlo method and the modified least-squares method. The proposed method is applied for the symmetric distributions in the conducted emission measurements. The validation of the combined method showed its satisfactory level of accuracy.     

数控车间信息集成技术研究

在分析数控车间生产管理的业务流程及车间硬件环境特点的基础上,构建了车间制造执行活动集成框架及执行信息流程模型.提出了基于Web服务和组件技术的数控车间数字化信息系统集成解决方案.应用分布式组件对象模型的组件技术设计了功能构件,并加以封装以实现系统内各功能模块的集成;系统与外部环境集成采用基于标准Web服务接口的方式,通过设置信息访问器和发布器来实现.开发了一个原型系统.实践证明,该系统不仅能实现车间信息的内外部集成,而且具有良好的可扩展性、可重构性和易维护性.     

Response sensitivity analysis of the dynamic milling process based on the numerical integration method

As one of the bases of gradient-based optimization algorithms, sensitivity analysis is usually required to calculate the derivatives of the system response with respect to the machining parameters. The most widely used approaches for sensitivity analysis are based on time-consuming numerical methods, such as finite difference methods. This paper presents a semi-analytical method for calculation of the sensitivity of the stability boundary in milling. After transforming the delay-differential equation with time-periodic coefficients governing the dynamic milling process into the integral form, the Floquet transition matrix is constructed by using the numerical integration method. Then, the analytical expressions of derivatives of the Floquet transition matrix with respect to the machining parameters are obtained. Thereafter, the classical analytical expression of the sensitivity of matrix eigenvalues is employed to calculate the sensitivity of the stability lobe diagram. The two-degree-of-freedom milling example illustrates the accuracy and efficiency of the proposed method. Compared with the existing methods, the unique merit of the proposed method is that it can be used for analytically computing the sensitivity of the stability boundary in milling, without employing any finite difference methods. Therefore, the high accuracy and high efficiency are both achieved. The proposed method can serve as an effective tool for machining parameter optimization and uncertainty analysis in high-speed milling.     

A novel numerical approach for workspace determination of parallel mechanisms

In this paper, a novel numerical approach is proposed for workspace determination of parallel mechanisms. Compared with the classical numerical approaches, this presented approach discretizes both location and orientation of the mechanism simultaneously, not only one of the two. This technique makes the presented numerical approach applicable in determining almost all types of workspaces, while traditional numerical approaches are only applicable in determining the constant orientation workspace and orientation workspace. The presented approach and its steps to determine the inclusive orientation workspace and total orientation workspace are described in detail. A lower-mobility parallel mechanism and a six-degrees-of-freedom Stewart platform are set as examples, the workspaces of these mechanisms are estimated and visualized by the proposed numerical approach. Furthermore, the efficiency of the presented approach is discussed. The examples show that the presented approach is applicable in determining the inclusive orientation workspace and total orientation workspace of parallel mechanisms with high efficiency.

     

Improved numerical integration method for flowrate of ultrasonic flowmeter based on Gauss quadrature for non-ideal flow fields

Multipath ultrasonic flowmeters with large diameter are widely used in industry. And their measurement performances are sensitive to velocity profiles in conduits. Gauss–Jacobi and Optimized Weighted Integration for Circular Sections (OWICS) method are commonly applied in flow measurement of multipath ultrasonic flowmeters, both of which assume ideal flow in pipes. They are not proper for non-ideal flow measurement. Therefore, an improved numerical integration method for flowrate based on Gauss quadrature is proposed. With this method, optimum relative path heights and corresponding weights are determined according to specific disturbed flows. By comparison Gauss–Jacobi, OWICS with the improved method, the validity of the proposed method is verified for typical disturbed flows based on both theoretical analysis and experiments, and measurement performances of ultrasonic flowmeters are improved significantly.     

A fast method for the numerical solution of thermal-elastohydrodynamic lubrication problems

The paper presents a method for the numerical solution of the elastohydrodynamic lubrication problem in line contacts, which includes thermal and rheological effects. The method consists in alternating repeatedly the solution of a generalised Reynolds equation and of the energy equation. In both cases use is made of a finite-element technique. Since the method proves to be very fast, a computer program has been developed which runs on common personal computers. Results (presented for two values of load parameter and for a range of values of slip/roll ratio up to 50%) show that thermal and non-Newtonian effects can strongly influence the film thickness and are essential for a reasonable evaluation of traction force. In this connection, the dimensionless parameter K (which depends on the equivalent curvature radius as well as on thermal conductivity and other material parameters) appears to be determinant.     

A modified formula for accurate determination of three‐dimensional birefringence of fiber using modified subfringe integration method

The development of the use of interferometric techniques in the study of the optical properties of materials encouraged many researchers to work on the derivation and development of the theoretical considerations and the equations used in the calculations of those properties. The form of these equations depends on the technique used and the cross section of the sample, and also on the method of calculating the optical path difference of light across the sample studied. A modified formula to calculate the three‐dimensional birefringence distribution of the fiber, without the need to determine the refractive indices of the fiber in the parallel and perpendicular directions, was presented. The phase distribution of the simulated and experiment interferograms was obtained using subfringe integration method. The results obtained from the new method were compared with the calculated results of a well‐known method (Z method) and the figures presented showed that the results of the two methods were close to each other.     

Effects of aliasing on numerical integration

During the course of processing acceleration data from mechanical systems it is often desirable to integrate the data to obtain velocity or displacement waveforms. However, those who have attempted these operations may be painfully aware that the integrated records often yield unrealistic residual values. This is true whether the data has been obtained experimentally or through numerical simulation such as Runge–Kutta integration or the explicit finite element method. In the case of experimentally obtained data, the integration errors are usually blamed on accelerometer zero shift or amplifier saturation. In the case of simulation data, incorrect integrations are often incorrectly blamed on the integration algorithm itself. This work demonstrates that seemingly small aliased content can cause appreciable errors in the integrated waveforms and explores the unavoidable source of aliasing in both experiment and simulation—the sampling operation. Numerical analysts are often puzzled as to why the integrated acceleration from their simulation does not match the displacement output from the same simulation. This work shows that these strange results can be caused by aliasing induced by interpolation of the model output during sampling regularisation.     

A simple sixth order numerical method for solving the Reynolds equation

A numerical iterative method is given for the solution of the Reynolds equation subject to separable boundary conditions. The iteration error for a given eigenfunction is sixth order in the step size. The method has been tested in the case of the finite exponential bearing pad for which exact analytical solutions are available. The dimensionless load capacity per unit width, W, can be calculated to 0.1% accuracy if ten terms are used in the sum for W. Only the first five terms need be calculated using the iteration, thereafter, analytical approximations given in the article may be used. Not more than twenty steps are needed in any given iteration to obtain the accuracy stated above.Calculations of the dimensionless load capacities of plane bearings show that the method is at least one order of magnitude faster than the method based on a two-dimensional rectangular array of points. The superiority is even more marked when calculations are made for a family of plane bearings having the same inclination but different breadth/length ratios.     

基于非结构动网格的跨音速颤振研究

采用流固耦合的方法对跨音速颤振进行了数值模拟.流体方面在改进的非结构动网格的基础上应用中心格式的有限体积法求解了Euler方程.结构方面则在Euler方程的基础上求解了后掠机翼典型剖面的结构方程.用时间推进的方法计算了结构响应特性.最后计算了NACA64A006翼型剖面的跨音速颤振边界,与相关实验结果吻合的比较好.     

A systematic method for studying a manufacturing enterprise to determine the possibilities for integration

There is a need to develop a framework for integration in manufacturing. This paper gives a framework for an ‘integration audit’, i.e. an approach which identifies areas for integration and produces an integration profile which summarizes the findings. An integration audit takes the form of asking and answering questions. A progressive approach to integration is recommended which (1) establishes performance measures, (2) integrates the material flow system, (3) plans integration inside each management function, (4) plans the dataflow between functions and (5) organizes the system by assigning responsibility to individuals for different sets of tasks.     

基于提升小波的颤振图像边缘检测方法研究

这里基于提升小波理论重点研究了图像边缘检测问题，提出了一种新的图像多尺度边缘检测方法，该检测方法适用于多种线性或非线性双正交小波，具有运算速度快、检测精度高等特点；并基于此边缘检测技术，研究了飞机结构颤振的边界预测问题，给出了一种新的稳定性参数估计方法。     

A new model for the plate leveling process based on curvature integration method

Leveling is a process used to minimize the plate defects including flatness imperfections and uniformity of internal stress in the plate industry. It plays an important role in delivering the desired material properties and product standards required. This paper presents a new mechanics model for predicting the leveling process of plates. First, the mechanics model is developed based on the curvature integration method. Next, a global nonlinear unconstrained optimization method is utilized to solve this model. Then, the presented model is evaluated by comparative study to experimental data. Finally, the leveling process is studied using our model. It is found that the bending curvature of the plate is highly sensitive to the contact angles between the plate and the roller. The defective plate with different initial curvature tends to be flatted and the residual stress can be reduced effectively after being leveled.     

一种面向集成的注塑模冷却系统特征识别算法

提出一种基于图的注塑模冷却系统特征识别方法:首先根据注塑模型芯或者型腔三维模型构建面边图,再对面边图进行扩展,得到相应的扩展属性面邻接图;在此基础上,对冷却系统特征的规则进行描述,并依据该规则将冷却回路特征子图从型芯或者型腔的扩展属性面邻接图中识别出来.对于识别出来的冷却回路特征子图,首先进行简化处理,去掉多余的水路信息,然后提取其直径和中心线信息并进行优化,最后转换成CAE系统所需的格式.实例测试表明,该冷却系统特征识别算法能有效地识别注塑模的冷却回路特征,提高用户的工作效率并降低出错率,实现了冷却系统在CAD和CAE之间的无缝集成.     

A numerical method for the calculation of lubricant pressures in bearings with mixed lubrication

A model for mixed lubrication, assuming that the total normal load applied to the plane of the lubricated surfaces is carried partly by the hydrodynamic action of the lubrication film and partly by asperity contacts and that the total friction force between the lubricated surfaces is partly due to viscous friction and partly to asperity contacts, was used to develop a numerical solution for pressure distribution in a bearing experiencing mixed lubrication. The geometry treated and the pressure distribution obtained were for a simple slider bearing, but the method could easily be extended to other shapes. The model is based on measured roughness of a real surface. Real load carrying capacity and drag can therefore be determined since they are related directly to bearing pressure distribution     

A numerical method for dynamic analysis of tracked vehicles of high mobility

A numerical method is presented for the dynamic analysis of military tracked vehicles of high mobility. To compute the impulsive dynamic contact forces which occur when a vehicle passes on a ground obstacle, the track is modeled as the combination of elastic links interconected by pin joints. The mass of each track link, the elastic elongation of a track link between pin joints by the track tension, and the elastic spring effects on the upper and lower surfaces of each track link have been considered in the equations of motion. And the chassis, torsion bar arms, and road wheels of the vehicle are modeled as the rigid multibodies connected with kinematic constraints. The contact positions and the contact forces between the road wheels and track, and the ground and the the track are simultaneously computed with the solution of the equations of motions of the vehicle consisting of the multibodies. The iterative scheme for the solution of the multibody dynamics of the tracked vehicle is presented and the numerical simulations are conducted.     

A numerical method for the kinematic analysis of planar higher pairs in rolling contact

In this paper, a general mathematical model describing the planar motion of higher pairs in rolling contact has been used to derive a system of five nonlinear algebric equations. An iterative, but simple and efficient, numerical algorithm for solving these equations is presented. The computer code that implements this method is futher combined with the KINANL package to analyze complex planar mechanisms with embedded rolling-contact pairs. One complete example is used to illustrate the accuracy of this numerical method.