复合材料推力轴承设计与制造研究

文章首先对复合材料瓦面推力轴承的设计思路进行了分析;其后,围绕干燥处理、材料拌合、加压制造等环节,研究了复合材料瓦面推力轴承的制造工艺;最后,从瓦面进油机制、瓦面结构造型两个角度入手,提出了复合材料瓦面推力轴承设计与制造的把控要点.     

瓦面进油对推力轴承承载能力的影响分析

基于FLUENT软件建立了推力轴承瓦面进油的CFD分析模型,分析了瓦面进油槽压力、位置以及宽度对推力轴承承载能力的影响规律。研究表明,合理的瓦面进油设计有利于提高推力轴承的承载能力。当进油槽压力达到一定数值后对油膜压力具有积极的增压作用;进油槽位置应靠近推力瓦入油边侧;进油槽宽度对承载能力的影响很小。研制了采用瓦面进油的某型重载推力轴承装置,开展了性能试验和1 100 h长跑试验,为推力轴承润滑系统的设计提供了参考。     

弹性模量对塑料瓦推力轴承润滑性能的影响

弹性金属塑料瓦(EMP瓦)压缩弹性模量是一复合弹性模量,并不像金属材料那样是一个常数,而是随压力增大而逐渐增大。结合"三峡推力轴承方案"中EMP瓦推力轴承数据,从理论上计算了EMP瓦压缩弹性模量的变化对推力轴承润滑性能的影响,从而对EMP瓦压缩弹性模量允许的变化范围有所了解。计算结果表明:压缩弹性模量的变化对最小油膜厚度、最高油膜温度和最大压力有一定的影响,而对功耗影响不大。     

数字弹性模量测定仪的设计与研究

介绍了一种应用激光技术、CCD摄像传感技术、液晶显示技术于一体的数字弹性模量测定仪,该仪器与弹性模量测定仪相比,具有操作简单,精度高,智能化水平高等优点,便于教学,可大大提高工作效率。     

弹性模量对弯曲成形法非球面研磨中磨具成形精度的影响

弯曲成形法非球面研磨中弹性模量误差是影响磨具成形精度的关键因素,通过力学和高等数学方法建立了磨具弯曲成形的数学模型,推导出误差公式,分析了弹性模量误差的影响,并给出了算例,表明在选择磨具材料的过程中．要根据工件的精度要求确定材料弹性模量的取值．保证其控制在一定范围内,从而保证磨具的成形精度,进一步提高研磨工件的面形精度。     

复合材料纵向弹性模量疲劳衰减规律研究

研究了载荷大小和铺设角度对疲劳载荷作用下复合材料的纵向弹性模量连续衰减规律产生的影响,由此构建了一个量化描述模型,对材料纵向弹性模量的衰减进行预测。为验证模型的合理性,设计了一套通过测量不同单向板应力应变关系来获取材料纵向弹性模量的疲劳试验方案,并对一系列不同铺设角的碳纤维复合材料单向板进行了大量疲劳试验。分析结果表明,所构建的衰减模型较合理地描述了复合材料纵向弹性模量的疲劳衰减规律。     

Predicting modulus of rupture (MOR) and modulus of elasticity (MOE) of heat treated woods by artificial neural networks

In this study, MOR and MOE of the heat-treated wood were predicted by artificial neural networks (ANNs). For this purpose, samples were prepared from beech wood (Fagus orientalis Lipsky.) and spruce wood (Picea orientalis (L.) Link.). The samples were exposed to heat treatment at varying temperatures (125, 150, 175 and 200 °C) for varying durations (3, 5, 7 and 9 h). According to the results, the mean absolute percentage errors (MAPE) were determined as 0.74%, 1.01% and 1.04% in prediction of MOR values, and 1.14%, 2.21% and 2.13%, in prediction of MOE values for training, validation and testing data sets, respectively. In the prediction of MOR and MOE, values of R² were obtained greater than 0.99 for all data sets with the proposed ANN models. The results show that ANN can be used successfully for predicting MOR and MOE of heat-treated wood.     

Influence factors on natural frequencies of composite materials

Frontiers of Mechanical Engineering - Compared with traditional materials, composite materials have lower specific gravity, larger specific strength, larger specific modulus, and better...     

有场制备的磁流变弹性体压缩弹性模量测试分析

针对磁流变弹性体压缩弹性模量随磁场变化的问题,在磁场存在的环境下制备出其材料配比分别为羟基铁粉为108 g,硅橡胶为28 g,硅油为18 g的磁流变弹性体磁流变弹性体,在压缩应变ε=2.6%的情况下分别对磁场方向与磁流变弹性体颗粒链压缩方向平行和垂直的情况下建立了数学分析模型。对磁流变弹性体的压缩弹性模量进行了理论分析,并通过实验印证了理论分析的准确性。研究结果表明,加载磁场方向与磁流变弹性体内部颗粒链压缩方向平行的情况下,材料内部磁致压缩力随着磁感应强度的增强而非线性增大;加载磁场方向与磁流变弹性体内部颗粒链压缩方向垂直的情况下,材料内部磁致压缩力随着磁感应强度的增强而非线性减小。     

Comparison of restorative materials and surface alterations after prebiotic and probiotic beverages: A nanoindentation and SEM study

The purpose was to investigate the surface characteristics of various resin-based materials by immersing in probiotic beverages. A total of 420 disc-shaped samples (5 mm × 2 mm) were prepared from resin-based composites. Samples were divided into four groups and immersed for 10 min/day for 1 month in either a probiotic sachet, kefir, kombucha, or artificial saliva (control). Surface roughness was measured at baseline and 1 month. One sample of each of the tested materials was examined under nanoindentation to evaluate the reduced elasticity modulus and nanohardness scores. Scanning electron microscopy (SEM) was used to compare surface differences. Data were analyzed statistically using one-way ANOVA test and the significance was set at p < .05. The lowest roughness scores were observed in Z250, Estelite Bulk Fill, and HRi ENA in most of the test groups. Among conventional composites, Z250 group had the highest nanohardness and elasticity modulus scores. Among bulk-fill composites, Estelite Bulk Fill Flow had the lowest surface roughness after immersion in probiotic beverages and the highest nanohardness values. Reveal HD, as a bulk-fill group showed higher surface roughness and considerably lower nanohardness and elasticity modulus scores. Maximum height levels of samples were recorded. SEM images revealed voids and microcracks on the surfaces of test materials. Dentists may prefer Z250 as microhybrid and Estelite Bulk Fill Flow as bulk-fill composites for the restorations of patients who consume gut-friendly drinks regularly. When there are various types of materials, nanoindentation is a useful method for evaluating surface alterations and sensible comparisons.     

试验机夹具的施力不均匀对弹性模量测定结果的影响

本文介绍采用微机控制电子万能试验机的引伸计系统绘制力与变形弹性回归曲线，测定材料的弹性模量。通过对四个方向分别安装引抻计进行弹性模量测定的曲线和结果的分析，说明了万能试验机夹具的施力不均匀对测定结果的影响，提出了解决偏心影响的途径，对提高弹性模量测试精确度具有一定意义。     

Design of composite flywheel rotor

A design method for a flywheel rotor composed of a composite rim and a metal hub is proposed by studying the connection between the rotor and the driving machine. The influence of some factors such as the rotor material, configuration, connection, and fracture techniques on energy density is analyzed. The results show that the ratio of the inner radius to outer radius of the rim is the key factor, and is determined by the rim material. Optimizing the hub can further efficiently improve energy density. The composite flywheel rotor is produced and its rotation stress has been tested at the speed of 20 krpm. The emulation results are consistent with testing results, which proves that the introduced design method is useful. __________ Translated from Optics and Precision Engineering, 2007, 15(6): 852–857 [译自: 光学精密工程]     

基于改进灰色聚类的复合材料无损敲击检测方法

针对传统复合材料敲击检测方法可靠性低、操作复杂的问题,引入了灰色系统理论,基于灰色关联聚类方法对敲击响应信号进行分类,并对接近关联度的计算方法进行了相应的改进。首先以加速度的时间历程作为系统行为序列,利用改进的计算方法对各序列间的接近关联度进行求解并构建灰色关联矩阵。然后通过灰色关联矩阵对序列组进行归纳合并,根据参考序列所在位置对敲击响应信号进行定性分类,最终在无需预先试验的情况下,完成了复合材料的缺陷检测工作。试验结果表明,基于改进灰色聚类的敲击检测方法准确率达到100%,在简化操作步骤的同时保证了敲击检测结果的可靠性。