基于响应面法的结构动力学模型修正

为了获得精确的结构动力学模型,提出了响应面和优化相结合的方法。利用参数化模型和优化拉丁方试验设计获取样本点构造多项式响应面模型,最小二乘法确定多项式系数并检验响应面的拟合精度。用响应面计算结果与实验结果的误差构造目标函数,自适应模拟退火算法来优化修正响应面参数,将修正后的参数值带入有限元模型得到修正模型。以欧洲航空科技组织的基准模型GARTEUR飞机模型为算例,对比修正前后模态频率,结果表明修正后的模型在测试频段和预测频段具有良好的复现和预测能力,进而验证了基于响应面法与优化方法相结合的结构动力学有限元模型修正的有效性。     

基于激光二维散射原理在线测量表面粗糙度

针对现有零件表面粗糙度测量仪器操作复杂,现场测量能力差的问题,提出一种基于激光二维散射的在线测量方法,该方法不仅可以测量表面粗糙度的统计参数,而且可以反映出表面纹理的形貌特征.在测量中,用无衍射激光光束作光源,用高精度的CCD摄像机作位移传感器,利用Matlab进行表面粗糙度测量数据采集与处理,使表面粗糙度在线检测成为...     

弧齿锥齿轮基本参数优化设计

为改善因传统机械式机床加工运动受限而采用局部共轭接触造成的齿面接触区域小的现状,同时为提升齿面接触性能,提出了一种弧齿锥齿轮基本参数优化设计方法。基于齿轮副全齿面接触的实现方法,以齿轮基本参数为优化变量、排除啮合界限线和根切界限线（以下简称为“2类界限线”）及防止齿顶变尖为约束条件,建立了以传动润滑性能综合参数和齿面瞬时接触线总长度最大为目标的齿面接触性能多目标优化数学模型。引入更加适合模型本身的现代多目标骨干粒子群算法求解最优基本参数。以一个具体的弧齿锥齿轮为研究对象,对比基本参数优化设计前后齿面的接触性能指标。数值仿真结果表明,优化后2类界限线分布于工作齿面区域外,表征润滑性能的综合参数的最小值和表征承载能力的齿面瞬时接触线总长度的最小值都有明显提升。有限元模型仿真结果表明,优化后工作齿面无干涉且呈全齿面接触。该研究提供了一种快速可行的弧齿锥齿轮基本参数最优设计方法,为弧齿锥齿轮的优化设计提供了参考。     

脉冲激光作用Al2O3的表面形貌演变过程

激光表面加工是一种能够有效降低陶瓷材料表面粗糙度的方法,为了研究脉冲激光与陶瓷材料作用后表面形貌演变过程及激光工艺参数对表面粗糙度的影响,本文通过有限元法建立了瞬态二维轴对称数值模型,研究了单脉冲、多脉冲激光作用于氧化陶瓷表面形貌的演变过程及激光工艺参数对表面粗糙度的影响。结果表明：单脉冲激光对材料表面具有显著的平滑效果;多脉冲激光加工在脉冲2～3次时具有最好的平滑效果,继续增加脉冲数量,熔池内的表面轮廓开始向下凹陷,表面平滑效果减弱;采用不同工艺参数加工时,过大的频率、脉宽、激光功率都会导致材料表面粗糙度增加。当表面温度处于熔化温度与蒸发温度之间,熔池内流体以毛细力为主要驱动力,促使表面逐渐平滑;当表面温度超过蒸发温度时,熔池内流体受反冲压力挤压,促使表面粗糙。实验与模拟结果对比表明,该模型具有较高的准确性。     

Laser parameter optimization for surface texturing of inconel 625

The optimum laser parameters required for the inconel 625 alloy surfaces to have the desired properties have been determined. Process parameters were optimized to get maximum heat affected zone depth (HAZ) and width and maximum aspect ratio and minimum defect outside of the spot area independently of each other. Also, the effect rates of the examined process parameters on the treated surface quality were determined separately for each surface feature. As a result of optimization using Taguchi method, the most effective parameters to obtain the desired surface were obtained as gas type with 72.26 % for heat affected zone depth, gas type with 90.46 % for heat affected zone width, gas type with 81.57 % for aspect ratio, pulse energy with 30.99 % for minimum defect outside of the spot area. The best results were obtained on the surfaces obtained as a result of the confirmation experiment with the new parameters obtained with the Taguchi method. Since the results of the confirmation experiments are highly compatible with the results suggested by the Taguchi method, the Taguchi method may be concluded as reliable in the laser ablation of the inconel 625 surface.     

The velocity and attenuation of outgoing surface acoustic waves measured using an ultrasonic microscope with two focusing transducers

A new method for measuring the local parameters of outgoing surface acoustic waves (OSAWs) is proposed. The technique employs a system of two focusing transducers, with the output signal taken from one of these scanning over the sample surface. In comparison with the conventional method with a single transducer moving in the direction normal to the sample surface, the proposed technique is capable of conducting measurements in a greater range of OSAW velocities and is less sensitive to parameters of the immersion liquid. The new method was experimentally verified by measuring systems with known properties.     

基于模糊神经网络与主成分分析的磨削表面粗糙度在线预测

基于声发射和振动信号提出了一种模糊神经网络和主成分分析的表面粗糙度预测方法,以提高磨削过程中工件表面粗糙度识别的准确性。首先,采集磨削程中声发射与振动信号,提取相关时域特征、频域特征和小波包特征参数,利用主成分分析对特征量进行降维优化;然后,构建表面粗糙度模糊神经网络预测模型,将信号特征量与表面粗糙度作为模糊神经网络的输入和输出;最后,对模型进行训练,并对表面粗糙度预测精度进行验证。实验结果表明:通过主成分分析(PCA)方法对声发射和振动信号特征量进行降维得到5个主成分,以此建立的模糊神经网络表面粗糙度预测模型的效果精度可达到91%以上,与局部线性嵌入和多维标度法降维方法相比,PCA方法降维后的特征所含信息更优,预测准确度更高。     

The effects of laser machining parameters on roughness and contact angle for boron carbide ceramic surface

Hydrophobicity or Hydrophilicity properties of boron carbide ceramic surface can be controlled by manipulating the roughness of the surface and thus the contact angle. In this study, the wettability of the boron carbide surface was manipulated by laser with different parameters. The contact angle was measured at 9^th seconds after the droplet was dropped onto the laser-treated surface. Also, the change in contact angle in the first 9 seconds after the droplet was dropped was examined. For a more hydrophobic surface, it was aimed to have the largest contact angle at 9^th seconds after the droplet was dropped and the smallest change with time in contact angle. The effects of laser scan speed, power, frequency and overlap rate on the contact angle of the treated surface were investigated using the Taguchi method. It was calculated to what extent each examined parameter affected the result. The effectiveness rates of the two most effective parameters which were scan speed and overlap rate were obtained. Since the results of the verification tests performed to confirm the results obtained are quite compatible with the results predicted by the Taguchi method, the Taguchi method can be regarded as a reliable method in optimizing laser parameters.     

考虑桥路面粗糙度的移动体参数识别

基于虚拟变形(VDM)方法中移动动态影响矩阵的概念,利用双自由度质量-弹簧阻尼模型模拟移动车辆,系统推导和阐述了车-桥耦合系统中粗糙路面上移动体参数的识别方法。以移动体参数的修正因子为优化变量,通过最小化桥体结构实测响应和计算响应的平方距离进行识别,识别精度高,对噪声鲁棒性强,且较少的传感器就能识别多个移动体参数。利用移动动态影响矩阵,每步优化中无需时时重构系统参数矩阵,计算效率高。利用一个三跨连续梁模型验证该方法的有效性,在5%的噪声影响下,利用一个传感器可以准确地识别多个移动体参数和移动荷载。此外,通过比较平坦路面与粗糙路面上的移动体参数的识别方法和结果,结合车体参数的灵敏度分析,说明了路面粗糙度、移动体参数对结构响应的影响及不同情况下参数识别中优化变量的选取原则。     

Extending electrical resistivity measurements in micro-scratching of silicon to determine thermal conductivity of the metallic phase Si-II

The aim of this work to analyse the relationships between parameters of concrete surface geometry determined with various methods as well as their relations to adhesion in repair systems. Several types of concrete preparation techniques were selected to obtain different levels of surface roughness of concrete substrates. Four measurement techniques, corresponding to different levels of observation, have been used to characterize the surface geometry: laser profilometry, mechanical profilometry, a microscopic method and a “sand” (macroscopic) method. The correlations between parameters describing surface geometry are determined. The relationships between bond strength and selected parameters of surface geometry are also discussed.     

多孔金属比表面积的计算方法

提出了一种根据泡沫金属的孔率和孔径这两个基本参量计算其比表面积的方法.利用泡沫金属比表面积与孔率和孔径的对应数理关系,结合有关实验数据,成功地计算出了电沉积法和高压渗流铸造法制备的泡沫金属的比表面积.     

取样长度与间隔对花岗石磨削表面分形维数计算的影响

利用高斯滤波对花岗石磨削表面轮廓数据进行处理,再用结构函数分析法,对不同取样长度及不同取样间距时花岗石磨削表面轮廓的分形特性进行了研究,分析了取样长度及取样间距对花岗石磨削表面轮廓分形参数计算结果稳定性的影响,确定了花岗石磨削表面分形参数计算的合适尺度。     

Effect of surface roughness on nanoindentation test of thin films

By using the two-dimensional quasicontinuum method, the nanoindentation process on a single crystal copper thin film with surface roughness is simulated to study the effect of surface morphology on the measurements of mechanical parameters. The nanohardness and elastic modulus are calculated according to Oliver-Pharr’s method. The obtained results show a good agreement with relevant theoretical and experimental results. It is found that surface roughness has a significant influence on both the nanohardness and elastic modulus of thin films determined from nanoindentation tests. The effect of such factors as the indenter size, indentation depth and surface morphology are also examined. To rule out the influence of surface morphology, the indentation depth should be much greater than the characteristic size of surface roughness and a reasonable indenter size should be chosen. This study is helpful for identifying the mechanical parameters of rough thin films by nanoindentation test and designing nanoindentation experiments.     

Measurement of Microrelief Parameters Based on the Correlation Method of Image Processing of the Surfaces Under Study

Measurement Techniques - A method is proposed for measuring the parameters of surface microrelief of machine parts by optical-electronic and computer means. The method is based on calculating the...     

基于响应面方法的支架结构模型修正研究

为减小有限元建模中不可避免的误差,以支架结构模型为研究对象,选取结构不同部件的三个弹性模量和三个密度参数作为设计变量。根据中心复合设计,建立试验样本空间,利用样本参数的显著性分析结果筛选修正参数。结合线性回归方法,建立支架模态频率与修正参数的二阶多项式。以试验模态分析结果为依据,完成支架结构模型修正。响应面方法修正后的模态频率与试验模态频率具有一致性,且避免重复调用有限元模型,大大提高修正效率,具有修正响应快速性和工程实用性。     

Atomistic simulation of chemical vapor deposition of (111)-oriented diamond film using a kinetic Monte Carlo method

Chemical vapor deposition (CVD) of (111)-oriented diamond film is modeled using a kinetic Monte Carlo atomic scale method. The method is parameterized by the rates of the accompanying surface chemical reactions and permits one of these reactions to take place at each simulation step. The effect of local surface structure and morphology on the rates of surface reaction is examined. Film growth at two different chemical compositions of the feed gas and two substrate temperatures is studied in order to determine the effect of these process parameters on (a) the quality of the deposed film and (b) the rate of deposition. The quality of the film is judged by concentration of the point defects (vacancies and H atoms embedded in the film) and by surface roughness. The results obtained show that the parameters that increase the deposition rate, primarily the substrate temperature and the concentration of CH4 in the feed gas, also increase the defect content and surface roughness.     

基于响应面法的楔横轧非对称轴类件轴向平衡研究

楔横轧非对称轴类件时由于存在较大不平衡的轴向力,会产生轴向窜动并导致台阶缺损和表面重皮等质量缺陷.为了减小不平衡的轴向力,目前一般采取的方法是结合工艺参数对楔横轧力能参数的影响规律,利用数值模拟手段,通过多次预设计工艺参数并反复试算以获得能使左右两端轴向力相等或近似相等的最佳工艺参数.该试算方法计算量大、繁琐、不直观,且需逐个零件进行,通用性差.本文通过利用中心组合实验设计并结合响应面法获得轴向力的响应曲面图,利用轴向力等值线选取工艺参数以保证非对称轴类件楔横轧的轴向平衡,本方法简单、直观,极大地节省了工艺参数选择所需时间,缩短了非对称轴类件楔横轧的模具设计周期.     

A direct differentiation formulation of electromechanical sensitivity analysis for rough surfaces in contact

In this article, the electromechanical sensitivity analysis of a rough surface contact law with respect to its governing parameters is developed using the direct differentiation method. The numerical accuracy of the method is assessed in two numerical examples. Finally, the identifiability of surface roughness parameters using an inverse method based on numerical optimization is investigated using pseudo-experimental input data.     

表面粗糙度参数的计算方法

介绍了表面粗糙度参数的计算方法，并用ＱｕｉｃｋＢＡＳＩＣ语文编程实现。     

基于逆响应面法的有限元模型修正

基于响应面法（RSM）的有限元模型修正是以若干设计参数（如密度、弹性模量等）为自变量,以若干特征参数（如固有频率、振型等）为因变量,通过回归分析方法来拟合特征参数关于修正参数的显式表达式。提出的逆响应面法（IRSM）则是以特征参数作为自变量,设计参数作为因变量。利用此法的有限元模型修正可直接根据特征参数的目标值得到设计参数的修正量,而不需要经过迭代计算,有效地提高计算速度和精度。介绍逆响应面法及其应用,讨论使用响应面法和逆响应面法进行有限元模型修正的优缺点和适用范围,分析适合于逆响应面法的逆响应面函数、实验设计方案和回归精度检验的方法。利用逆响应面法对一简支梁进行有限元模型修正的结果表明,逆响应面法能高效准确地修正设计参数,对于输出变量少于输入变量的情况更能显著减少有限元计算次数,适用于复杂的工程结构。