基于遗传算法的圆度误差评价

为了在全局范围正确评价圆度误差 ,本文采用遗传算法对圆度测量数据进行最小二乘法评价 ,克服了传统圆度最小二乘法评价的局部收敛问题。计算结果表明 ,本文介绍的方法可以在设计变量的全局范围内有效、正确地评价圆度误差     

基于微粒群算法的圆度误差评价

为了在全局范围正确评价圆度误差，采用微粒群算法对圆度测量数据进行最小二乘法评价，克服了传统圆度最小二乘法评价的局部收敛问题。计算结果表明，本文介绍的方法可以在设计变量的全局范围内有效、正确地评价圆度误差。     

选择圆度误差评定方法的体会

圆度误差评定方法有4种：最小二乘圆法、最小外接圆法、最大内接圆法、最小区域法。同一被测零件的圆度误差用4种评定方法评定的圆度误差结果有差异的,那么,到底应该选择哪种评定方法呢？哪种评定方法评定的圆度误差精度更高呢？在实际生产中,当对被测件评定结果有争议时,哪种方法可作为仲裁的依据呢？本文谈谈自己的体会。     

基于MATLAB的圆度评定方法

本文利用MATLAB优化工具箱,采用最小区域圆法、最小二乘圆法、最小外接圆法和最大内接圆法进行圆度的评定。并给出了参考程序和运行结果。     

基于区域搜索的圆度误差评定方法

针对最小二乘法评定圆度误差存在的非线性方程组求解困难、线性化处理后的最小二乘法对测量采样点的布置特殊要求难以满足等问题,提出了基于区域搜索的圆度误差评定方法,阐述了方法的原理与实现步骤,并进行了实际圆度误差的对比测量与评定.结果表明,此方法简便易行,评定精度比最小乘法提高4.16%.     

最小区域法评定圆度误差的程序设计技术

介绍了最小区域法判别准则和最小区域法快速精确求解圆度误差的基本思想,设计了用最小区域法评定圆度误差的程序设计技术。利用本文所述的程序设计技术,依据最小区域法快速精确求解圆度误差的基本思想,能够设计出最小区域法评定圆度误差的软件,实现三坐标测量数据的圆度误差评定。     

圆度误差的最小二乘法、最小包容区域法和最优函数法评定精度之比较

目的在于寻找符合最小条件的圆度误差评定方法。首先详细介绍圆度误差评定的最小二乘法、最小包容区域法和最优函数法的算法模型与实现方法;然后,在三坐标测量机上对被测圆进行采样点坐标数据提取,分别用最小二乘法、最小包容区域法和最优函数法对给定圆进行误差评定。结果表明,最小包容区域法评定精度最高,最优函数法评定精度次之,最小二乘法评定精度较低。     

基于机器视觉的非均匀分布点圆度误差评定

对圆度误差的4种评定方法进行比较和改进,改进后的最小二乘法适用于非均匀分布圆或圆弧的计算,同时研究最小区域法在离散点非均匀分布圆的运用。用解析的方法求解最小区域下的圆度误差,改善了优化迭代法的缺陷,经过数次计算准确得到最小区域,以最小区域圆心作为圆心、平均半径作为半径,可将其应用于不完整圆和分布点非均匀分布的圆中。引出圆度误差评定的相对误差率ξk ,可说明圆度误差、加工精度、加工方法及微观占比例等情况。在圆孔视觉检测实验中,4种评定方法的计算结果分别为ξk1=0.019、ξk2=0.017、ξk3=0.018、ξk4=0.019。离散非均匀分布圆的检测方法可广泛应用于实际生产检测中。     

基于平面投影的空间直线度误差评定

在分析了目前空间直线度误差测量的一些方法后,为了得到简单易行并且结果更准确的空间直线度误差值,本文提出了基于平面投影的空间直线度误差评定方法.先求出均值点的空间最小二乘线,然后将直线度的测量点投影至最小二乘线的中垂面上,在中垂面上找出所有投影点的最小包容圆,将最小包容圆的直径作为空间直线度误差.经实验数据验证,本文方法...     

基于LabVIEW环境下的圆度误差算法实现

文章阐述了使用最小包容区域法思想求解圆度误差的一种算法。该算法通过外圆逼近的方法求取最小包容区域法的特征点,确定最小区域圆圆心,进而求得圆度误差。算法通过LabVIEW编程实现,经过实例测试并与Talyrond365的评定结果相比较,证明该算法能够满足圆度误差快速、精确测量的需求。     

KDP晶体单点金刚石切削脆塑转变机理的研究

加工超光滑表面的KDP晶体是现代超精密加工技术领域的重点研究课题。实验采用维氏压痕法研究KDP晶体脆性材料(001)面不同晶向的硬度、断裂韧性的变化规律。通过建立KDP晶体脆塑转变临界切削厚度模型,研究了KDP晶体金刚石切削脆塑转变机理。结果表明,脆塑转变临界最小切削厚度出现在断裂韧性最小而硬度最大的[110]方向;脆塑转变临界切削最大厚度出现在断裂韧性最大而硬度最小的[001]方向。并利用超精密机床加工了KDP晶体,加工结果与理论推导结论相符合,在[001]方向加工出表面粗糙度为7.5nm(RMS)的超光滑表面。     

圆度误差目标函数凸凹性的研究

应用凸函数理论证明了圆度误差最小区域评定法的目标函数是二维欧氏空间R2 中的连续、不可微的凸函数 ,从而证明了目标函数的全局极小值的唯一性 ,并给出了实例     

Cyclic viscoelastoplasticity of polypropylene/nanoclay composites

Observations are reported on isotactic polypropylene/organically modified nanoclay hybrids with concentrations of filler ranging from 0 to 5 wt.% in cyclic tensile tests with a stress?Ccontrolled program (oscillations between various maximum stresses and the zero minimum stress). A pronounced effect of nanofiller is demonstrated: reinforcement with 2?wt.% of clay results in strong reduction of maximum and minimum strains per cycle and growth of number of cycles to failure compared with neat polypropylene. To rationalize these findings, a constitutive model is developed in cyclic viscoelasticity and viscoplasticity of polymer nanocomposites. Adjustable parameters in the stress?Cstrain relations are found by fitting experimental data. The model correctly describes the growth of the ratcheting strain and shows that fatigue failure is driven by a pronounced increase in plastic strain in the crystalline phase. To assess the influence of loading conditions on the changes in the material parameters, experimental data on polypropylene are studied in cyclic tests with a strain?Ccontrolled program (oscillations between fixed maximum and minimum strains) and a mixed program (oscillations between various maximum strains and the zero minimum stress). Numerical simulation confirms the ability of the model to predict the evolution of stress?Cstrain diagrams with the number of cycles.     

Performance trade-offs for conventional lenses for free-space digital optics

We describe the limitations on the use of conventional lenses in optical computing that arise from manufacturing tolerances. The consequences on maximum array size, minimum device size, and propagation delay of systems are discussed. Two experimental optical computing systems are then compared with these results. We show that there are maximum and minimum bounds on the focal length and the ?-number of lenses imposed when manufacturing tolerances are considered. We also show that there are maximum bounds on image sizes and space-bandwidth products and trade-offs between spot size and system latency.     

On the characteristic distance and minimum fracture toughness for cleavage fracture in a C-Mn steel

This study makes a further investigation on the characteristic distance, minimum fracture toughness and its temperature dependence for cleavage fracture in a C-Mn steel by the detailed finite element analysis combined with experimental observation and measurement. Results show that there is a minimum active zone for cleavage initiation, and the minimum fracture toughness of steel results from the minimum active zone necessary. Corresponding to the minimum fracture toughness, the cleavage fracture ahead of a crack tip can only initiate in a distance range from the minimum distance X_fmin determined by the lower boundary of the active zone to the maximum distance X_fmax determined by its upper boundary. The reason for the occurrence of the minimum active zone and the factors influencing it are analyzed. The temperature dependence of the characteristic distance and minimum fracture toughness and its mechanism are also discussed.     

The Maximum Value of Inventory and Shortages in Production Lot Size Systems

This paper proposes methods of finding the maximum value of the inventory (MVI), the maximum storage space (MSS), and the maximum value of shortages (MVS) in the production lot size system, where several products are being made on a single facility with repetitive common cycle length. Noting the fact that the MVI, MSS and MVS depend on the slack (idle) times between the production runs of two consecutive products, linear programming formulations are presented to determine the minimum MVI, the minimum MSS and the minimum MVS. In addition, when there are restrictions or upper limits on some or all of these measures, linear programming formulations are developed to obtain the constrained optimal lot sizes.     

Precision of determination of the coordinates of an underwater cable from the results of measurements of its magnetic field

The precision of the coordinates of an underwater cable that are determined from the measurements of the strength of the magnetic field created by the cable is estimated. The maximum total or minimum difference signal of the horizontal component of the field with the use of two sensors as well as the minimum vertical component of the magnetic field with the use of a single sensor are recorded.     

Evaluation of minimum zone for flatness by normal plane method and simplex search

This paper presents an optimization approach for evaluating the minimum zone flatness for a data set obtained from a Coordinate Measuring Machine. The search for the minimum zone is performed in the parameter space of a plane. The perpendicular distance (p) from the origin to a normal plane intersecting each point in the data set is determined. The difference between the maximum 'p' and the minimum 'p' for a particular set of parameters (direction cosine angles) determines the minimum zone for flatness. The parameters defining the orientation of a plane through each point in the data set are searched systematically. The set of parameters that determine the minimum zone is found by simplex search. The new method is applied to six example data sets and the results are compared with other methods.     

脂肪酸二元低共熔混合物相变温度和潜热的理论预测

对低共熔混合物相变温度和潜热的理论预测公式进行了选择和验证,对脂肪酸类二元低共熔混合物的配比、熔点和熔化潜热进行了理论计算。从实际的计算过程来看,计算值与实验值吻合得很好,可以用来计算脂肪酸类低共熔混合物的热特性参数。在15种脂肪酸类低共熔混合物中,熔点最低为10.2℃,最高为51.5℃;熔化潜热最低为138.6J/g,最高为187.5J/g。从工程实际应用来看,脂肪酸类低共熔混合物适用于低温采暖、生活热水、相变墙体、温控混凝土、相变服装等领域。     

Interaction of interface delamination and plasticity in tensile steel members reinforced by CFRP plates

This paper presents experimental and numerical results related to double shear lap tests performed on steel specimens reinforced using CFRP plates. These tests have been simulated taking into account the elastic–plastic behavior of the steel and the delamination between steel and CFRP by means of a cohesive approach. The results obtained are discussed in terms of: (i) maximum load bearing capacity, (ii) minimum bond length in order to exploit the maximum load bearing capacity, (iii) brittle to ductile transition of the interface failure (iv) combination of interface delamination and plastic deformation of the steel. Design formulas for the definition of the minimum bond length and the load bearing capacity of the joint are validated.