基于数值-解析方法测量静压条件下阻尼材料动态力学参数

建立了一种测量静压条件下阻尼材料动态力学参数的数值-解析方法。首先,分别制作两种空腔半径不同的圆柱空腔覆盖层样品,测量两种样品在静压力下的复反射系数。其次,采用有限元法仿真静压力下的空腔结构变形,在此基础上同样采用有限元法计算复反射系数。以实测复反射系数和计算复反射系数建立二元非线性方程组,利用牛顿迭代法求解方程组可获得复弹性模量和复泊松比等黏弹性动态力学参数。对聚氨酯材料制作的样品进行了复反射系数测量,分析了静压力对聚氨酯材料动态力学参数的影响规律。最后,测量了某不同结构吸声覆盖层静压下的反射系数,并与采用实测材料参数计算的反射系数进行了比较,验证了该方法的正确性。     

Reference instruments based on industrial pressure sensors

A high precision pressure transducer with a reduced error of 0.03% is created. The possibility of using a reference instrument with a relative error of 0.02% is considered. __________ Translated from Izmeritel’naya Tekhnika, No. 1, pp. 31–33, January, 2008.     

纤维缠绕复合材料压力容器封头厚度预测

本研究的目的是建立一种用来预测纤维缠绕复合材料压力容器封头厚度的方法。针对固化成型的复合材料压力容器封头型面, 基于封头段所有缠绕纱带总体积保持不变条件, 提出了一种采用三次样条函数来预测复合材料压力容器封头厚度的方法。采用该方法对具有不同几何尺寸、 不同缠绕工艺参数的复合材料压力容器进行了封头厚度预测, 并与传统预测方法及实际厚度测量值作了对比分析。算例结果表明, 该方法能够比传统方法更准确地预测纤维缠绕复合材料压力容器的封头厚度, 从而为有限元建模分析提供精确的厚度参数。      

串联孔板的流量-压降计算探讨

基于气液两相流体流过孔板的压降理论提出串联孔板节流元件的计算方法，用实验数据进行计算分析和间接验证。结果表明，计算值与实验值有较好的一致性，说明该方法用于串联孔板节流元件的设计计算有一定的可行性。     

Analytical study on the buckling of cylindrical shells with stepwise variable thickness subjected to uniform external pressure

This article focuses on the buckling of cylindrical shells with stepwise variable thickness subjected to uniform external pressure. First, combining the method of separation of variables, perturbation method, and Fourier series expansion, an analytical method for the buckling analysis of cylindrical shells with axisymmetric thickness variation subjected to external pressure is established. The method is verified by comparing with the previous results. Then, the stepwise variable thickness of cylindrical shells is described exactly by the arc tangent function. Finally, using the presented method, a general formula for the critical buckling load of cylindrical shells with stepwise variable thickness subjected to uniform external pressure is derived. This general formula is compared and discussed with some empirical formulae in the current design standards. This study lays a theoretical foundation for the calculation of the buckling load of cylindrical shells with stepwise variable thickness subjected to uniform external pressure. Moreover, it provides a reference and guidance for the further revision of related standards.     

基于背景网格的混合网格变形方法

混合网格已广泛应用于复杂外形的粘性流动模拟,能否将其推广应用于气动弹性研究,混合网格的变形方法成为主要问题.发展了一种混合网格变形方法,即生成一套非结构四面体背景网格,采用弹簧网络法进行背景网格变形,在背景网格与流场计算的CFD网格之间建立一种快速的代数插值方法,获得流场计算的混合网格变形.由于背景网格仅用于网格变形,不参与流场计算,物面网格可以与流场计算网格不一致,大大减少网格数量,提高弹簧网络法的变形能力和计算效率,进而提升流场计算混合网格的变形能力和计算效率.对于复杂外形流场网格和背景网格在物面的不一致可能造成的覆盖不完全问题,提出了同时生成覆盖流体域和固体域的多套非结构背景网格的方法,保证复杂外形计算时混合网格的高质量变形.由于背景网格采用全三维的线弹簧加扭转弹簧的动网格变形方法,大大提高了大变形的网格变形能力.首先以M6机翼的非结构和混合网格变形为例,与已有方法比较,验证本文方法的有效性;其次运用于三维转动、平动、弯曲变形等典型工况,说明方法对大变形的实用性;最后运用于气动弹性标模和机翼带外挂导弹的复杂外形的颤振特性计算,说明其处理复杂工程问题的能力.     

差压气密性检测仪设计与实现

设计了基于差压法原理的以ARM处理器为控制核心的通用型气密性检测仪.该仪器系统通过气控阀控制气路对工件的充放气过程,并利用高精度差压传感器获得由气体泄露产生的差压值,人机交互界面采用触摸屏模块.结果表明,该检测仪方便快捷、测试精度高、稳定性好.     

基于S变换的结肠压力信号时频域分析

采用S变换对肠道压力信号在时频域进行分析与处理.与短时傅立叶变换(STFT)和Wigner分布相比,S变换解决了STFT窗函数长度不易确定的问题,并且S变换不存在交叉干扰和负频率问题.将S变换应用于结肠压力信号的分析,结合已知的肠动力理论,能够更直接地分析人体结肠的动力特性.结果表明,运用S变换对结肠压力进行时频域分析,可以有效获取信号的有用特征.     

Reduced basis method for managed pressure drilling based on a model with local nonlinearities

To circumvent restrictions of conventional drilling methods, such as slow control actions and inability to drill depleted reservoirs, a drilling method called managed pressure drilling (MPD) has been developed. In MPD, single-phase flow processes can be modeled as a feedback interconnection of a high-order linear system and a low-order nonlinear system. These nonlinearities appear locally both inside and at the boundaries of the computational domain. To obtain a fast simulation platform for real-time purposes (eg, online model-based controller implementation), model order reduction is required for MPD. However, the local nonlinearities render applying model order reduction techniques challenging. In this study, a new approach is proposed to deal with such nonlinearities within the reduced basis (RB) context and it is successfully tested on a model for MPD. Contrary to the classical RB technique, the proposed approach not only does not generate nonphysical spikes at the locations of these local nonlinearities but also yields high speedup factors. The obtained reduced-order model can be used for efficient online simulation and controller design for drilling systems with MPD.     

基于足底压力信号的步态识别

设计了一款基于足底压力传感器的足底测力系统,对压力传感器进行选型布局,设计信号调理电路,对采集到的压力信号进行放大及滤波处理,搭建硬件平台,设计信号采集界面;进行传感器标定实验以及足底测力系统实验,采集测试对象以不同步速进行平地行走以及楼梯行走时的足底压力信号;对采集到的足底压力信号进行比例运算,确定模糊集,设计隶属函数,以比例信号作为输入量进行模糊化处理,采用Larsen产品暗示法作为推理算子建立模糊规则推理,根据模糊输出信号识别出步态相位。