一种基于经验模式分解的结构损伤预警方法

提出了一种基于经验模式分解的结构损伤预警方法。首先,将结构反应信号用经验模式分解方法分解成一系列固有模态函数;然后,利用固有模态函数在结构损伤前后的能量分布变化来表征结构因损伤引起的动力特性改变;最后,计算结构的损伤预警指标。应用该方法对健康监测Benchmark模型结构进行分析,采集模型在锤击激励下结构损伤前后的动力响应,计算了结构损伤预警参数及其损伤预警指标。试验数据分析表明,基于经验模式分解的结构损伤预警指标具有良好的损伤预警能力,能够准确地判断结构初期损伤的发生。     

汽车驱动桥准双曲面齿轮齿面测量误差精确计算

为精确获取汽车驱动桥齿轮实际加工齿面的真实误差,改善汽车齿轮的齿面精度,结合汽车驱动桥齿轮在传动方面的优越性及其在机床调整计算、加工方法和齿面测量等方面的特殊性,对其齿面数控展成与数字化检测的运动关系进行了深入分析;鉴于汽车驱动桥齿轮齿面拓扑结构的复杂性,结合齿面误差计算原理,在实际加工齿面检测信息的基础上,提出了一种汽车驱动桥齿轮齿面误差的精确计算方法;最后,通过齿轮齿面加工测量结果的比对,验证了该齿面误差精确计算方法的正确性和有效性。     

基于工艺动作过程的机械执行系统概念设计过程模型

机械产品概念设计的目的是获得产品设计方案,以便为后续的详细设计奠定基础。为了获得较好的产品设计原理方案,需要对机械产品在概念设计阶段的过程模型进一步研究。在前人的研究基础之上,主要针对机械执行系统概念设计过程模型进行研究,提出基于功能-作用原理-工艺动作过程-执行动作-行为-功能载体过程模型和相互之间的映射策略,把产品概念设计的过程模型进一步细化,以更好的符合人们在产品设计过程中的逻辑思维,从而便于提高设计人员的创新能力。     

ADAMS/Matlab环境下车辆悬架联合仿真分析

针对ADAMS/View环境下某车辆1/4整车动力学模型,通过ADAMS/Control模块建立了ADAMS与Matlab软件之间的通信连接,在Matlab/Simulink环境下建立最优联合控制系统,运用ADAMS和Matlab/Simulink软件(即ADAMS/Matlab)进行联合仿真,并与在Matlab单一环境下运行的仿真模型进行对比分析。结果发现:两种分析方法都能使车辆悬架簧上总质量质心加速度均方根值和控制能量降低,而ADAMS/Matlab软件联合仿真控制下的悬架簧上总质量质心加速度和控制能量下降幅度更大。     

基于E-CBP的机电产品可持续概念设计方法

在传统概念设计方法的基础上,引入可持续设计理念,提出基于E-CBP(extended casual behavioral process)模型的可持续概念设计方法。通过对行为的特性研究,提出了相应的可持续设计指导原则。根据这些原则对E-CBP模型进行优化,并以电动抛光机为实例验证了该方法的可行性。     

凸轮轴磨削加工速度优化调节与自动数控编程研究

为进一步提高凸轮轴的加工精度、表面质量和加工效率,根据X-C轴联动磨床的运动原理,建立了凸轮轴恒线速加工理论数学模型,依据该数学模型采用三次样条拟合插值法,建立了凸轮转速优化调节的数值计算模型。结合具体凸轮轴零件及其磨削加工工艺方案的具体参数,计算出机床各运动轴加工过程的运动数据,在确保无工艺故障的前提下,最终把各轴的运动数据自动转换为对应数控控制系统的数控加工程序,从而实现了凸轮轴磨削的自动数控编程。最后在CNC8312A数控高速凸轮轴磨床上,对钱江32F型号凸轮轴的进气凸轮和排气凸轮分别进行磨削加工试验,得到了预期加工效果。试验验证表明,该加工速度优化调节及其自动数控编程方法在理论上和实践上都是可行的,完全满足实际生产的需要。     

弧齿锥齿轮中凹盘铣刀高效数控铣削及仿真

为了解决球头铣刀数控铣削弧齿锥齿轮时切削带宽小、效率低等问题,提出了基于中凹盘铣刀的弧齿锥齿轮五轴数控高效率铣削方法。在掌握弧齿锥齿轮几何构造的基础上,选用刀底带内凹的盘铣刀,先确定刀具侧倾角以避免齿槽底面的过切,再参考端铣刀加工自由曲面的理论确定刀具前倾角,以保证大的切削带宽。弧齿锥齿轮的数控铣削仿真验证了该高效铣削方法的可行性和正确性。     

时标信号在螺旋锥齿轮振动与噪声测量中的应用

在传统的齿轮振动与噪声测量的基础上,提出了一种使用旋转编码器为采集振动与噪声数据提供齿轮分度时标的测量方法;通过对齿轮啮合时谐波特征的分析,建立了螺旋锥齿轮振动与噪声的同步测量模型,推导了时标信号的频率特性,并分析了其滤波效果;然后在此基础上利用MATLAB软件对齿轮传动中的啮合频率及其谐波进行了仿真与分析;最后,在Y9550型滚动检验机上搭建振动与噪声测量的试验平台,并对螺旋锥齿轮的振动与噪声进行了测量验证。结果表明,利用时标分度信号的测量方法能够有效地隔离机床本身的振动并减少输入噪声的扰动及其他影响,进而准确地提取出与啮合周期信号相关的频率信息。     

Ultrasonic Velocity as a Tool for Physical and Mechanical Parameters Prediction within Geo-Materials: Application on Cement Mortar

This paper discusses the ability of ultrasonic wave velocity to evaluate some physical parameters within mortar. The behavior of ultrasonic pulse velocity within mortar subjected to incremetal stress was also studied. For experimentation, we carried out ultrasonic measurements on mortar samples before and during uniaxial compressive strength, perpendicularly to the stress direction. The water/cement ratios were varied in order to contribute certain specific characteristics. A set of expressions was obtained linking the initial velocities of longitudinal ultrasonic waves with compressive strength, density, porosity and load at elastic limit.The evolution of ultrasonic velocity through mortar samples under continuous incremental uniaxial stress were also investigated. The results illustrated the behavior of ultrasonic pulse velocity as a function of the applied stress. It was observed that velocity did not decrease under initial loading and until about 70% of the ultimate stress, where sudden decrease occurred, followed by the failure of the material.     

Full Curve Damage Process of Polypropylene Fiber Reinforced Mortars under Dynamic Tensile Loading Based on Acoustic Emission Technique

The study of the full curve damage process of polypropylene fiber reinforced mortars under medium strain rate (10^–6 s^–1–10^–4 s^–1) could enrich the understanding of the dynamic damage characteristics of polypropylene fiber reinforced structures. In order to explore the physical mechanisms of polypropylene fiber in the dynamic damage process of the polypropylene fiber reinforced mortars. The real-time dynamic acoustic emission (AE) technology was applied to monitor the damage process of polypropylene fiber reinforced mortars at different strain rates. The analysis of characteristics of AE wavelet energy spectrum and the average AE peak frequency of polypropylene fiber reinforced mortars with different polypropylene fiber content at different strain rates were conducted. The results show that with the accumulation of damage, the AE wavelet energy spectrum in ca8 frequency band increases first and then decreases and the average AE peak frequency increases gradually. The AE wavelet energy spectrum in ca8 frequency band and the average AE peak frequency decreases gradually with the increase of the strain rate, but them increases first and then decreases with the increase of polypropylene fiber content. The above AE characteristics could provide important information for the identification of dynamic damage mechanism of polypropylene reinforced fiber mortars.