磁流变智能镗杆的动力学模型

为了准确地在线调控磁流变智能镗杆的动态特性,有效地进行颤振抑制,对动力学模型进行研究.根据磁流变材料在屈服前区、屈服区和屈服后区所表现出的动态特性,结合Kelvin和Maxwell模型,建立本构模型,分析结果表明:该模型能够较好地反映磁流变材料动态特性.在此基础上,建立磁流变智能镗杆的动力学模型,并对屈服前后的动态特性进行分析,同时推导智能镗杆中磁流变材料的屈服临界条件,分析结果揭示:屈服一般发生在以磁流变材料屈服前系统共振频率为中心的频段内,且磁场强度越高,屈服频段越窄.对磁流变智能镗杆动力学模型进行数值仿真研究,分析结果与实测数据对比后表明:该模型能够较准确地描述磁流变智能镗杆动力学特性.     

磁流变智能镗杆的切削颤振抑制机理研究

针对深孔镗削过程中的颤振问题,提出了一种基于磁流变液的智能镗杆构件,并根据深孔镗削颤振的特点建立了磁流变智能镗杆切削系统的动力学模型.结合该模型对镗削系统的稳定性进行了分析,发现当通过调节磁场强度使系统刚度或阻尼增大时,切削系统的稳定性将明显提高,同时对系统固有频率与稳定性的关系也进行了分析,发现随着系统固有频率的减小或增大,系统稳定性极限叶瓣曲线将向左或向右平移,其条件稳定区域也将随之发生改变.当系统不稳定时,只要适当改变系统固有频率,就可以使切削系统处于稳定区域内.为了验证抑振机理,对磁流变智能镗杆系统进行了切削颤振控制实验研究,结果表明,通过控制切削系统的固有频率在一定的范围内封闭型变化,可以有效地抑制镗削过程中颤振的发生.     

减振镗杆中动力减振器动态特性的研究与测试

推导和测定了现代外伸减振镗杆中动力减振器的特性参数，完善了对大悬伸减振镗杆的研究．     

智能腰椎治疗仪动态特性的测试分析

本文分析了腰椎治疗仪的运动与动作特征,使用计算机辅助测试技术对该设备的运行状态进行了在线综合测试,分析了该设备的动作准确性和快速性,为合理设计此类设备提供理论依据.     

镗杆的优化设计

机床行业中内孔加工约占整个机械加工工作量的1/4,而深孔加工又在内孔加工中占有很大的比例。深孔加工中最常见的问题就是由于孔的直径限制了刀具的设计。当镗杆的长径比较大的情况下,镗杆的静态刚度和动态刚度都随之明显下降,在切削过程中引起切削颤振,轻者使被加工表面粗糙度恶化,重者使加工无法正常进行。     

TX1600镗铣加工中心横梁的动态特性分析

为研究TX1600型镗铣加工中心横梁的动态特性,在SolidWorks环境下建立横梁的三维实体模型,基于振动相关理论,运用Workbench软件对其进行模态分析,得出横梁的6阶固有频率及相应振型,并对其进行谐响应分析.结果得出横梁在受外部激振力下的动态响应特性,为横梁的优化设计提供了理论依据.     

高速数控车床切削的动态特性测试与分析

以高速数控车床CK7516GS为研究对象,对其动态特性进行了多工况的振动测试并采用Matlab软件对数据进行了处理.通过数据分析得到了各个工况的振动主频范围,并把各个工况对应的主频进行了对比,同时对振源进行了分析.测试结果表明:高速数控车床不同工况下振动主频大部分都集中在100Hz附近,其振动主要由切削力、电主轴旋转不平衡以及电磁力不平衡引起的.该分析为高速数控机床的系统动态设计和振动抑制提供了参考依据.     

汽车直拉杆的力学性能动态测试及其模态分析

提出了一种通过静态标定，结合动态测试来获得直拉杆的动态力学性能参数的试验方法，对汽车直拉杆进行了计算模态分析，得到其计算振动频率以及相应的振型，并通过试验得到试验模态频率及振型，对计算模态和试验模态进行振型相关性分析，将有限元的动态分析与试验数据有机地结合起来，验证了直拉杆有限元模型，为汽车直拉杆结构设计提供了依据。     

数字式测高仪的动态特性测试分析

数字式测高仪的测量速度、定位精度和测量力是表征其动态特性的3个主要方面.为此,论述了它们的具体测量方法,以某数字式测高仪为对象,采用微平面镜激光干涉仪、精密测力计等器具进行动态特性测试,给出了测试结果,分析了误差来源及其变化规律,其中,对测高仪定位误差的测试与分析是新的尝试.测试结论对改进测高仪的设计、提高测量精度具有实际价值.     

整体机械结构动态特性分析与参数测试

分析了整体机械结构在激励力方向上的的动态特性,介绍了一种小阻尼机械系统获得动态特性参数中的固有频率和阻尼比的方法.     

Integrated intelligent control analysis on semi-active structures by using magnetorheological dampers

The control strategy is very important for semi-active control or active control systems. An integrated intelligent control strategy for building structures incorporated with magnetorheological (MR) dampers subjected to earthquake excitation is proposed. In this strategy, the time-delay problem is solved by a neural network and the control currents of the MR dampers are determined quickly by a fuzzy controller. Through a numerical example of a three-storey structure with one MR damper installed in the first floor, the seismic responses of the uncontrolled, the intelligently controlled, the passive-on controlled, and the passive-off controlled structures under different earthquake excitations are analyzed. Based on the numerical results, it can be found that the time domain and the frequency domain responses are reduced effectively when the MR damper is added in the structure, and the integrated intelligent control strategy has a better earthquake mitigation effect.     

一维杆的纵向热弹性动力响应瞬态分析

引入状态空间理论,并在时域内应用差分格式,建立了一维杆热耦合问题的状态方程,分析了一维杆纵向热弹性动力响应的瞬态过程。杆的温度和力学边界条件在状态方程的求解过程中能够得到严格满足。算例表明,本文方法可以方便地计算和显示温度场和弹性场的瞬变过程,且收敛于最终的稳态结果。因此,用本文方法分析瞬态温度应力问题是非常有效性的。     

基于XGBoost的隧道掘进机操作参数智能决策系统设计

为了实现隧道施工的同质化,提出基于极端梯度提升算法（XGBoost）预测模型的隧道掘进机（TBM）操作参数的智能决策方法. 定义场操作系数指数（FOI）作为替代传统场切深指数（FPI）的围岩级别特征参数,使用XGBoost算法建立预测模型以实现对FOI的预测,对围岩级别进行预测、判断. 通过对优秀司机在特定FOI下TBM操作参数的选择,建立专家模型实现FOI与特定TBM操作参数的关联,实现TBM操作参数的智能决策. 使用引松工程的现场数据进行对比实验,结果表明,设计的TBM操作参数的智能决策系统能够实现对优秀的TBM司机操作参数决策的复现,相比于以FPI为特征参数的传统智能决策系统,新系统的推进速度和刀盘转速两部分的平均相对误差分别下降8.84 %和7.97 %.     

气动系统长气管建模与分析

由于气体的可压缩性,气压信号在长气管中的传递特性表现为非线性,这种非线性给系统设计和应用带来困难。从工程应用的角度出发,难过实验对气动系统中长气管的主要特征－气压信号的延迟进行了研究,根据长气管的物理特点建立了动力模型及数学模型,并对模型参数进行了辨识和分析,还根据流体力学的理论探讨了管内流体的状态,最后通过对数学模型的仿真和实验研究进行了比较,两者具有较好的一致性。     

弹引系统动态特性有限元分析

提出一种基于有限元分析的弹引系统动态特性计算方法.采用预紧单元对弹体和引信的耦合部位进行网格划分,对不同拧紧力时弹引系统的动态特性进行模拟.在相同的激励环境下,对某弹引系统进行了有限元数值计算和实测锤击试验,试验结果表明,所采用的有限元分析方法精度较高.     

Autoregressive trispectrum and its slices analysis of magnetorheological damping device

A combined magnetorheological damper combined with rubber spring and magnetorheological damper is addressed.This type of damping device has inherited the merits of rubber spring and the magnetorheological damper.The test damping device is made up of combined magnetorheological damper,amplitude controller,signal collecting device,computer software for dynamic analysis,etc.When a zeromean and non-Gaussian white noise interfere with the device,a time series autoregressive(AR) model is conducted by using the sampled experimental data.Trispectrum and its slices analysis are emerging as a new powerful technique in signal processing,which is put forward for investigating the dynamic characteristics of the magnetorheological vibrant device.The present of trispectrum and its slices analysis change with the variation of controllable working magnetic field of the damper correspondingly.It is indicated that AR trispectrum and its slices analysis methods are feasible and effective for investigation of magnetorheological vibrant device.     

Characteristic analysis of magnetorheological fluid based on different carriers

In order to prepare special MRFs to satisfy the demands of tracked vehicle,two different carrier fluids were used to prepare MRFs.Preparation of MRF,which are based on carrier of special shock absorption fluid and 45# transformer oil,was finished.And characteristics of these samples were tested and analyzed.The results show that Tween-80 and Span-80 can improve the sedimentary stability,and the larger mass fraction can also increase the sedimentary stability.Using 45# transformer oil instead of special shock absorption fluid as a carrier of MRF,the shear yield stress remains nearly constant but the viscosity and the sedimentary stability are reduced.The MRF with diameter of 2.73 μm shows better sedimentary stability than that of the MRF with diameter of 2.30 μm,or 4.02 μm.Stearic acid obviously improves sedimentary stability and off-state viscosity,but has no function on the shear yield stress.In magnetic field of 237 kA/m,the shear yield stress of MRF based on special shock absorption fluid is 18.34 kPa and the shear yield stress of MRF based on 45# transformer oil is 14.26 kPa.     

Evaluation of boring machine performance with special reference to geomechanical characteristics

The duration of tunneling projects mostly depends on the performance of boring machines. The performance of boring machines is a function of advance rate, which depends on the machine characterizations and geomechanical properties of rock mass. There were various theoretical and empirical models for estimating the advance rate. In this paper, after determining the geome-chanical properties of rock mass encountered in the Isfahan metro tunnel, the performance of the roadheader and tunnel boring ma-chine (TBM...