混杂纤维增强低树脂基摩擦材料磨损机理及性能研究

目的改善刹车片摩擦材料的耐磨性和降低制动噪声。方法通过正交试验设计摩擦材料配方,利用极差分析法探究混杂纤维对低树脂基摩擦材料性能的影响,并采用扫描电子显微镜观察摩擦材料磨损表面和磨屑的微观形貌,使用能谱仪分析磨屑的元素组成,以研究其磨损机理。结果混杂纤维增强低树脂基摩擦材料具有良好的耐磨性,其洛氏硬度维持在50~80HRM之间,剪切强度均处于11~16 MPa的适宜范围。随着树脂的质量分数从8%逐渐增加到10%,混杂纤维增强树脂基摩擦材料磨屑中O元素的质量分数降低了33.7%,Cu元素的质量分数降低了20.1%。结论丁腈胶粉对摩擦材料磨损率的影响最大,铜纤维对摩擦系数的影响最大,且铜纤维在摩擦过程中会在摩擦表面形成一层"转移膜",可以导出摩擦产生的高热量,从而缓解热衰退。酚醛树脂含量的变化影响摩擦材料的磨损机制,随着树脂含量的增加,摩擦材料由疲劳磨损转变为磨粒磨损。     

Are the relative variation rates (RVRs) approximate in different cities when the same energy-efficiency reform is taken to the same building?

On the assumption that the same envelope reform is made on two buildings located in 19 cities of China, America and Europe, this paper simulates the annual heating and cooling energy consumption before and after the reform with tools of DOE-2, DeST-h and the authors' characteristic temperature method (CTM), and makes further analysis on the relative variation rates (RVRs) of energy consumption. It can be found that the absolute reductions of annual heating and cooling needs may differ up to tens of times in different cities for the same buildings with the same energy-efficient measures. On the other hand, there is no obvious difference in initial investment for the same energy-efficient reform in various cities of a country or an economic district, therefore, the energy efficiency potentiality and economic value of the same reform are completely different under various climatic conditions, which illustrates that it is very important to harmonize the local climates when selecting an energy-efficient project in different locations. However, when the same measures are taken to the same building, the annual heating RVRs are approximate and the annual cooling RVRs are also approximate in different cities, which is the common rule of building energy efficiency.     

基于SSA-ELM的双层十字梁结构光纤布拉格光栅传感器三维力解耦

针对三维力传感器维间耦合干扰严重的问题,以双层十字梁结构光纤布拉格光栅三维力传感器为研究对象,提出了基于麻雀搜索算法优化极限学习机(Sparrow Search Algorithm–Extreme Learning Machine,SSA-ELM)的解耦算法.首先,研究了光纤布拉格光栅的传感及测力原理,揭示该三维力传感...     

数控车床主轴箱的传动设计

为了提高车床的综合性能,本文针对车床的主轴箱组合设计的特点,通过设置主轴箱的工件最大回转值、正转最高转速等已知条件,采用集中式传动,对其主传动方案和传动系统进行设计.根据《实用机床设计手册》查表获得相关参数值,并绘制出主轴箱的主传动系统图来保证车床主轴的精度,从而完成主轴箱的传动设计.     

基于轻量级神经网络的目标检测研究

由于以CSPDarknet53为主干的YOLOv4神经网络参数量巨大,将其移植至手机等小型设备上时会降低其检测精度和速度,为了提高检测速度同时将检测精度控制在合理范围内,提出将原有的53层神经网络改为15层,并对其中的聚类算法进行优化,引入K-means++聚类算法对数据集进行分析,生成满足检测条件的Anchor Box;使用在负区间带有一定斜率的LeakyReLU激活函数代替存在梯度消失问题的Sigmoid激活函数,从而增强浅层网络的学习能力;同时考虑到Bounding Box与Anchor Box之间的中心距和宽高比具有一定的相关性,提出在原有损失函数的基础上增加相应的惩罚项生成LCIoU损失函数,使损失函数在反向传播时梯度下降的方向性更好。实验结果表明,改进后的CSPDarknet15神经网络在VOC2007数据集上检测的平均精度达到83.94%,检测一幅图像的时间为3 625 ms,与CSPDarknet53神经网络相比,检测速度提高了54.43%,能满足小型设备实时检测的速度和精度要求。     

直齿圆柱齿轮淬火残余应力分析

直齿圆柱齿轮的使用很广泛,作为机械零部件中最重要部件,齿轮的应用寿命对机械零件的寿命有很深的影响。因此研究齿轮的使用寿命非常重要。基于ABAQUS有限元软件对齿轮进行淬火残余应力分析。     

基于AMESim的65吨汽车起重机支腿液压系统设计与仿真

随着社会资源开发,起重机的使用逐渐增多,同时施工作业时由于支撑不稳定引发侧翻等问题引发的安全事故也在上升.本文提出运用液压锁在支腿系统工作时能够将其锁死,防止其发生"软腿",提高起重机支腿的支撑稳定性,设计优化起重机支腿液压系统.利用AMESim对其系统建模并进行仿真分析,通过闭锁压力变化曲线分析系统工况.结果表明:整...     

风力发电机叶片的雾凇覆冰数值模拟

为了解风力发电机叶片覆冰情况,以某型300 kW风力发电机叶片为研究对象,根据切片-重构的思想,将叶片划分为有限个截面,基于叶片覆冰的物理过程,采用边界元法对风力发电机叶片的空气流场进行计算;采用拉格朗日法分析计算水滴在叶片表面的碰撞过程;通过迭代计算和冰形重构模拟覆冰增长过程,从而建立风力发电机叶片三维雾凇覆冰增长模...     

Wettability of MgO single crystal by liquid pure Pb,Sn and Bi

The wettability of MgO single crystals by liquid metals such as Sn, Pb and Bi was studied at 873 K in a hydrogen atmosphere. It became apparent that wettability was dependent on a crystallographic orientation and a heat treatment of the MgO substrate. The MgO surfaces were observed using an atomic force microscope (AFM) to clarify the effect of the surface arrangement of the substrate on wettability. The results suggest that the surface arrangement of the substrate does indeed affect wettability.