基于不确定度分析方法的硅微传感器设计方法研究

基于谐振式硅微压力传感器敏感结构设计原理,结合不确定度分析方法,分析了各结构尺寸对敏感结构固有频率以及检测灵敏度的影响.建立基于样本的随机模型在考虑尺寸加工误差的同时,评估了谐振敏感结构各个结构尺寸传感器固有频率以及检测灵敏度的影响大小并进行了比较,从而获得了对传感器性能起关键作用的影响因素.以上的结果可以为相应传感器敏感结构设计与优化提供参考.     

考虑非线性因素的科氏质量流量计灵敏度分析

基于科氏质量流量计(CMF)测量管的工作原理,为了提高传感器的灵敏度,了解其振动过程中非线性项对于CMF灵敏度的影响至关重要。以U型管科氏质量流量计为研究对象,考虑非线性因素,用比较法推导出非线性项对于CMF灵敏度的影响。此外,通过实验仿真,优化传感器结构,进而提高传感器灵敏度。     

基于介观压阻效应的新型微陀螺仪结构设计与优化

介绍了介观压阻效应,其灵敏度比硅压阻效应高一个数量级.利用该效应作为高灵敏度器件,首次提出了介观压阻效应微陀螺仪结构,并论述了其工作原理.利用AN SY S软件,对其结构性能进行仿真,分析了固有频率、振幅以及哥氏效应下敏感方向的位移等特性,提出了结构优化分析的方法.在哥氏效应等耦合作用下对该结构进行多参数优化设计,并得到优化结果.经过对结果进行比较和考量分析,结果证明：微陀螺仪的驱动频率和检测频率的差值由原来的217.83 H z增大到362.87 H z,微陀螺仪的工作带宽增大,同时质量块在Z方向的位移增大了0.3μm,从而使检测梁根部受到的应力也增大了1.7 M Pa,结构灵敏度提高了18%.     

双热源质量流量传感器数值模拟研究

在微小气体流量测量中,双热源型质量流量传感器具有精度高、反应快以及良好的环境温度适应性等特点。利用ANSYS.FLUENT软件,从反映传感器性能的线性度及灵敏度两大指标出发,改变质量流量传感器热流密度、热源间距、管径等参数进行数值模拟分析,分析了影响双热源型质量流量传感器性能的主要因素,从而为双热源型质量流量传感器的改进提供参考。     

四柱式力传感器固有频率提升研究

为研制高动态性能的四柱式力传感器,基于机理分析法,建立了四柱式传感器固有频率模型,得到了通过改进四柱式传感器结构参数来提高四柱式传感器固有频率的方法,并通过Solidworks仿真与标准锤击法实验验证了该方法的正确性。研究结果表明：四柱式传感器的固有频率主要由其四立柱的结构参数决定,增大四立柱横截面长度或宽度,降低柱体高度,有利于提高其固有频率。研究结果也指出,除改进四柱式传感器结构外,增大材料弹性模量,降低材料密度,也能进一步提高其固有频率。     

一种求解不均匀随机场结构频率特性的方法

针对实际随机结构中每个单元的随机性不同，且各随机参数间的相关系数也不同的情况，提出了一种新的随机参数结构频率特性的计算方法。在结构总刚度和质量矩阵中，根据各元素所含随机参数的不同以及相同随机参数幂次的大小，将刚度和质量矩阵分别展开为若干矩阵之和的形式；利用求解结构固有频率的瑞利商公式，得到结构固有频率关于结构中各个随机参数的函数表达式；利用求解随机变量函数的矩法求得结构各阶固有频率的随机特性。通过算例验证了该方法的可行性和有效性，并分析了各随机变量对结构固有频率随机性的影响。     

随机激励下的随机结构全局灵敏度分析

为了考察处于随机激励下的结构系统的随机不确定性输入参数对结构动力响应的影响,提出了基于动力响应均值的全局灵敏度指标和基于动力响应方差的全局灵敏度指标。结合这两个指标对随机结构在随机激励下的响应进行灵敏度分析,能够对输入参数的重要性作出合理评估,以便为改善结构设计提供有益指导。为求解所提出的全局灵敏度指标,提出了一种基于点估计的高效方法。该方法将所提出的动力响应灵敏度指标视为均值和方差算子的嵌套,通过嵌套使用点估计的方法进行分解降维。通过对某发动机管路系统的算例分析,验证了上述全局灵敏度指标及其求解方法的工程适用性。     

尿素机中高频微弯型科氏质量流量计信号处理

为了将微弯型高频传感器的科氏质量流量计应用于尿素加注机,根据在企业现场采集到的流量信号数据,建立科氏质量流量传感器加注过程的信号模型。根据此模型分析已有的数字信号处理算法产生误差的原因,并从兼顾实时性与准确性两方面出发对算法进行改进,以适用于尿素机测量的需要。在研制的基于DSP的科氏质量流量变送器上,实时实现算法,并进行水流量标定实验和尿素加注机标定实验,其测量误差小于0.1%,重复性误差小于0.05%。     

多维加速度传感器的设计及优化

研制了一种基于单惯性质量块的一体化结构三维加速度传感器。依据传感器的工作原理,采用有限元工具对传感器静态和动态特性进行了分析,给出了弹性体的应变分布、固有频率及振型等,按各轴向灵敏度及其一致性和固有频率等目标对传感器结构尺寸进行了优化设计。有限元分析计算和实验结果表明,所研制的传感器在三个正交方向上都有较高的灵敏度,各加速度分量互干扰小。     

基于四分之一车辆模型的具有随机结构参数车辆的随机动力分析

本文通过具有随机结构参数的四分之一车辆模型研究了具有不确定性结构参数的车辆在受到来自道路的随机激励作用下的振动响应问题。文中将簧上质量、簧下质量、悬挂阻尼、悬挂刚度以及轮胎刚度均认为是随机变量。将路面的不平整引起的对车辆的激励看作高斯随机过程并通过简单指数功率谱密度来建立力学模型。利用蒙特卡洛方法得出了车辆的固有频率和模态振型的均值、标准差以及变异系数。利用随机变量函数矩方法在频域中建立了车辆的随机响应的均方值的数字特征的计算表达式。通过工程算例表明了车辆结构参数的随机性对其动力响应的影响。本文所做的工作可拓展应用于车辆结构参数的灵敏度分析和动力优化设计。     

科氏流量计测量管固有频率在线预测方法

提出了一种基于幅值变化期信号特征参数识别的科氏流量计测量管固有频率在线预测方法,该方法对测量管固有频率变化时引发的过渡期振动信号进行两次整周期采样,进而通过傅里叶变换获得反映所采样信号特征的虚部与实部参数,并根据所建立的基于信号特征参数的固有频率改变量计算模型,计算出测量管当前固有频率。对所提出方法进行了实验验证。该方法可用于科氏流量计振动控制中,帮助其将驱动频率快速、精准地调整到固有频率上,从而提高科氏流量计在复杂多变工况下的测量可靠性。     

Model-based correction of Coriolis mass flowmeters

Coriolis mass flowmeters (CMF) are direct mass flowmeters and form a real mean along the flow profile. They do not exploit secondary physical properties of the specific liquid, such as fluid velocity and fluid density in the measuring process, but directly exploit the primary property inertia to measure mass flow. However, there is some evidence from field applications that the devices, in particular those using a single straight pipe, suffer from parameter variation. Therefore, the flowmeter has to be carefully adjusted with respect to physical properties of the liquid, operating conditions, and site installation. When modeling the CMF using two oscillatory systems referring to the first and second mode, the mass flow enforces the coupling of these oscillatory systems. In the ideal case, the coupling is only affected by the mass flow. Detailed analysis, however, reveals that asymmetries in installation, sensors, actuators, as well as pipe-inhomogeneities heavily contribute to this coupling and thus lead to a parameter variation. In this paper, a model-based approach is presented to identify the parameters of the model using an auxiliary excitation of the system.     

A study on an online measurement method to determine the oil discharge ratio by utilizing Coriolis mass flow meter in a calorimeter

In this paper, an online measurement method of oil discharge ratio (ODR) is experimentally investigated based on a compressor calorimeter with the Coriolis mass flowmeter (CMF). In this method, the oil concentration is determined by a linear mixing law of the specific volume model using the density of the refrigerant, oil and refrigerant-oil mixture obtained by CMF. During the testing, the light absorption method is also conducted simultaneously for the comparison. The results indicate that the presented CMF based density method has an average relative deviation of 4.28%. The accuracy of the CMF based density method is superior to the light absorption method, which has the relative deviation of −8∼23% compared with the standard sampling method. The presented CMF-based method can be expected to be used for future ODR measurement due to its non-sampling, online, and accurate features.     

Numerical Modelling of Flow Boiling Heat Transfer in Horizontal Metal‐Foam Tubes

The flow boiling heat transfer performance in horizontal metal‐foam tubes is numerically investigated based on the flow pattern map retrieved from experimental investigations. The flow pattern and velocity profile are generally governed by vapour quality and mass flow rate of the fluid. The porous media non‐equilibrium heat transfer model is employed for modelling both vapour and liquid phase zones. The modelling predictions have been compared with experimental results. The effects of metal‐foam morphological parameters, heat flux and mass flux on heat transfer have been examined. The numerical predictions show that the overall heat transfer coefficient of the metal‐foam filled tube increases with the relative density (1‐porosity), pore density (ppi), mass and heat flux.     

滚珠丝杠副滚珠循环系统的动力学研究和仿真

研究滚珠丝杠副的滚珠循环系统中的碰撞接触现象,根据赫兹接触理论和经典碰撞理论,并考虑滚珠和导珠管的几何外形、丝杠的转动速度等因素,建立滚珠和导珠管碰撞接触的动力学模型。在此基础上分析了滚珠的入口速度、材料密度对碰撞力大小、接触时间的影响。应用多体动力学软件Adams,根据实际物理参数,创建了导珠管和滚珠的几何模型,对钢珠在导珠管中的运动情况进行仿真模拟,获得了碰撞过程中滚珠的运动轨迹、速度、加速度以及碰撞力的变化情况。通过对不同参数的物理模型理论计算和仿真,分析了影响滚珠循环系统动力学的主要因素。理论计算和仿真、试验结果吻合较好,这对于优化导珠管结构,研究开发新型滚珠丝杠副有重要的意义。     

Analysis of capillary interferometry for measuring refractive indices of minute samples

A method of measuring the refractive indices of minute samples by analyzing capillary interferometry is introduced. With the interference theory of light, the intensity distribution of an interference fringe pattern formed by a cylindrical tube of a capillary is obtained, and the influence of some parameters on the fringes are discussed. The measurement accuracy and its relative problems are analyzed.     

Analysis of boundary layer control by heat transfer strips using an asymptotic approach to the PSE

The effect of heating strips on the stability of boundary layer flow over a flat plate is investigated. Heating strips alter the flow stability through the temperature dependence of the fluid properties. A stability study is carried out using the parabolized stability equations (PSE) that calculates the effects of temperature dependent fluid properties in terms of asymptotic expansions based on the total heat input. The leading order influence is obtained as a general result and, for the particular Prandtl number taken, is independent of any special set of property laws. In a fluid for which the intrinsic viscosity increases with temperature and the density decreases with temperature (such as air) the results show that the optimal location for a heating strip to stabilise the flow is upstream of the neutral point. The optimal location moves further upstream as the total heat input level is increased. For a given heat input widening the heating strip further stabilises the flow. Finally, the potential of the asymptotic method as a tool for further analysis of the flow is discussed.     

Thermal Response of Steel–Steel Composite Metal Foams under Small-Scale Torch-Fire Conditions

Steel–steel composite metal foam (S–S CMF) is a novel metal matrix composite material characterized by its high strength-to-weight ratio and unique mechanical and thermal properties. It is made up of hollow stainless-steel spheres, embedded in stainless steel matrix, with 65–70% air in the structure making it effective as an insulating material. S–S CMF is being explored for use in tank cars carrying hazardous materials (HAZMATs) as a potential partial replacement for conventional carbon steel and thermal insulating material currently being used. In this study, S–S CMF material is numerically and experimentally evaluated for its thermal protection performance. Experimental studies are conducted in scaled-down jet fire condition while numerical studies are conducted using fire dynamics simulator (FDS). Based on experimental and modeling results, as well as uncertainty studies, 13–15 mm thick S–S CMF ranging in density of about 2.5 g cc⁻¹ tested as novel structural/insulating material meets the acceptance criterion for small-scale simulated torch-fire testing. Further success is anticipated in future full-scale evaluation of 122 × 122 cm samples. The outstanding fire resistance and thermal protection of S–S CMF is attributed to the substantial volume of air trapped within the material, which correlates to its total density.     

基于输入能量的地震动时程强度包络函数研究

结构随机振动分析和人工合成地震动记录均需要将反应谱转换为功率谱,地震动强度包络函数对转换结果有着重要影响。为合理地确定强度包络函数模型中各参数的取值,依据输入能量谱与傅里叶幅值谱的精确转换关系,建立了由非平稳地震动功率谱计算输入能量谱的方法,并分析了各参数取值对功率谱与能量谱的影响。以匹配设计谱的天然地震动记录样本的平均输入能量谱作为参考依据,通过与设计谱转换得到的输入能量谱进行对比分析,确定了各类场地设计谱转换为功率谱时,强度包络函数模型的各参数取值。通过人工合成地震动记录的输入能量谱分析,验证了各参数取值的合理性。