基于Harris角点检测的位移测量算法

在力学实验中,位移和应变的测量是最基本任务之一。本文提出了一种基于Harris角点检测的位移测量算法。通过检测变形前图像的角点,然后利用光流跟踪技术在变形图像中搜索其匹配点,最终计算得到位移值。算法对图像采用网格划分方式进行计算,达到了全场测量的目的。实验结果表明,该算法位移测量精度高、稳定性好,可作为基于图像处理的无损测量方法。     

一种新的全场应变光学测量方法

采用光栅衍射、光学全息、显微图像分析等技术，本文提出了一种用于固体表面应变直接测量的新的光学方法，并把这一方法应用于铝合金试件的单轴拉伸试验。实验结果表明：该方法的应变测量灵敏度为８×１０－５。     

主导曲线法测定J阻力曲线的研究

本文利用主导曲线法测定了国产核容器用钢材料Ａ５０８－３的Ｊ阻力曲线，并将实验结果与卸载柔度法作了对比，进而说明这种新方法有其广阔的应用前景；同时，本实验引入了计算机数据实时采集及自动处理系统．这些系统的引入大大提高了实验精度和效率．     

A new Apparatus for Long-term Petrophysical Investigations on Geothermal Reservoir Rocks at Simulated In-situ Conditions

We present a new apparatus capable of maintaining in-situ conditions pertinent to deep geothermal reservoirs over periods of months while in the same time allowing a variety of continuous petrophysical investigations. Two identical devices have been set up at the GFZ-Potsdam. Lithostatic overburden- and hydrostatic pore pressures of up to 100 and 50 MPa, respectively can be simulated. In addition in-situ temperature requirements of up to 200°C can be met. The use of corrosion resistant parts throughout the pore pressure system allows investigations with highly saline formation fluids. Rock permeability, electrical conductivity as well as compressional- and shear-wave velocities can be measured simultaneously and the pore fluid can be sampled under pressure for further chemical analysis. Scientifically, the usage of the device focuses on risk potentials in exploration and exploitation of deep geothermal reservoirs. Particularly, the investigations address possible effects of fluid-rock interactions on the transport properties of a reservoir host rock.     

新型陀螺仪转子表面的测量及对陀螺性能的影响

提出了一种新的陀螺转子表面测量技术，它采用光强调制式的单光纤传感器作为测量元件。系统测试(0～100μ)结果显示：相应的灵敏度为2．5mV／μm，精度等级优于1％，重复性优于0．5％。设计了一种适用于陀螺转子表面测量的系统，其测量精度达到0．005μm。以直径38mm的实心陀螺转子球为例介绍了整个系统的组成及其工作过程，给出了两种转子表面图形绘制法(墨克脱投影法和三维表面重现法)和该陀螺转子的三维表面测量图；最后分析了图形的存在引起的转子表面不规则对陀螺性能的负影响，这些参数可以用来预测陀螺漂移性能。陀螺；转子表面测量；光纤传感器；二维旋转台；表面图的绘制     

基于Haar小波变换的位移场测量方法

本文提出了一种应用小波变换对固体表面位移场进行测量的新方法，在图像分析时，用各点属于不同尺度的小波变换系数来表征该点周围的子区。将试件表面位移前后的两幅数字图像进行小波变换，通过变形前后两幅图像小波变换系数之间的相互匹配，使位移前后两幅图中的子区对应起来，从而确定图像的位移场。本文应用Haar小波变换进行了计算机模拟实验和实物位移实验。引入亚像素技术，获得了0．02的位移测量精度。     

静态应变数据采集器的新软件

本文介绍了静态应变数据采集器应用软件的编制情况,通过改进软件界面和采样模式及数据图表处理等方面的功能,使应用软件更符合各类工程测试的实际需求。     

过阻尼地震检波器阻尼系数测量的研究

对动圈式恒速度型过阻尼地震检波器相对阻尼系数的测量方法进行了研究。首先引入了动圈式地震检波器的运动方程和输出方程,随同参数定义给出了这种检波器对直流电流的响应函数;然后讨论了当前两种过阻尼系数的测量方法———经典的参数辨识法及两点法,明确了它们的适用范围;最后提出了一种线性方法。根据该方法,相对过阻尼系数能够表示成检波器响应曲线的半峰高宽度和检波器自然频率乘积的线性函数。研究表明,利用本方法可在较宽阻尼范围取得更好性能,且该方法便于硬件实现。     

发动机叶片扭转和弯曲变形同步测量新方法

扭转和弯曲变形测量可以确定叶片弯扭变形耦合的特征,为叶片弯扭耦合分析提供可用的试验手段。本文提出了一种发动机叶片扭转和弯曲变形同步测量的新方法,其中,扭转角度测量方法能更加灵活地应用于测量叶片类形状不规则构件的扭转变形,而弯曲变形测量方法解决了叶片变形方向未知且存在弯扭耦合时的叶片变形测量问题,从而可实现对叶片截面扭转和弯曲变形的同步测量。对上述测量方法进行了专门的验证试验,结果表明:与传统方法测量结果相比,扭转角度测量偏差小于1%,挠度测量偏差小于2%,满足工程测量精度要求。     

A New Divergence Free Synthetic Eddy Method for the Reproduction of Inlet Flow Conditions for LES

This paper describes a recent development of the Synthetic Eddy Method (SEM) proposed by Jarrin et al. (Int J Heat Fluid Flow 30(3):435–442, 2009) for generation of synthetic turbulence. The present scheme is designed to produce a divergence-free turbulence field that can reproduce almost all possible states of Reynolds stress anisotropy. This improved representation, when used to provide inlet conditions for an LES, leads to reduced near-inlet pressure fluctuations in the LES and to a reduced development length, both of which lead to lower computer resource requirements. An advantage of this method with respect to forcing approaches (which require an iterative approach) is the suitability for direct usage with embedded LES. Results for a turbulent channel flow are reported here and compared to those from the original SEM, and other direct approaches such as the VORTEX method of Sergent (2002) and the Synthesized Turbulence approach of Davidson and Billson (Int J Heat Fluid Flow 27(6):1028–1042, 2006), showing overall improved performance and a more accurate representation of turbulence structures immediately downstream of the inlet.     

A New Technique for Characterization of Low Impedance Materials at Acoustic Frequencies

Measuring the mechanical properties of low impedance rubbery polymers at acoustic frequencies is a challenging problem due to the small signal amplitudes, relatively high loss, and the long wavelength of stress waves. One such material is solid polyurea (PU), an elastomeric copolymer, which has excellent chemical, thermal, and mechanical properties and is widely used as a coating (e.g. in truck bed lining) or blast protection (advanced helmet designs and concrete structures) material. Moreover, due to its heterogeneous structure, PU has a wide transition of thermo-mechanical behavior from rubber-like to glassy compared to most engineering polymers, which translates to a broader loss spectrum in frequency domain. In this study, we have developed a new test technique by modifying the split Hopkinson pressure bar and using ball impact to measure Young’s storage and loss moduli of polyurea at kHz frequencies. This will therefore fill the frequency gap between the dynamic mechanical analysis (DMA) and ultrasonic (US) wave measurement. The measured Young’s storage and loss moduli from this technique are compared with the master curves of the moduli developed using experimental data of dynamic mechanical analysis and ultrasonic wave measurements. This technique is a direct measurement which provides more reliable data in the kHz frequency range and can be used to evaluate the reliability of other indirect estimations including master curves. The utility of this technique is not limited to polyurea and it can be used to characterize other low impedance materials at kHz frequencies.     

A New Device for Mechanical Testing of Blood Vessels at Cryogenic Temperatures

As part of an ongoing program to study the thermo-mechanical effects associated with cryopreservation via vitrification (vitreous in Latin means glassy), the current study focuses on the development of a new device for mechanical testing of blood vessels at cryogenic temperatures. This device is demonstrated on a bovine carotid artery model, permeated with the cryoprotectant cocktail VS55 and a reference solution of 7.05M DMSO, below glass transition. Results are also presented for crystallized specimens, in the absence of cryoprotectants. Results indicate that the elastic modulus of a specimen with no cryoprotectant, at about −140°C (8.6 and 15.5°C below the glass transition temperature of 7.05M DMSO and VS55, respectively), is 1038.8 ± 25.2 MPa, which is 8 and 3% higher than that of a vitrified specimen permeated with 7.05M DMSO and VS55, respectively. The elastic modulus of a crystallized material at −50°C is lower by ∼20% lower from that at −140°C.     

A New Device for Tensile and Compressive Testing at Intermediate Strain Rates

Experimental Mechanics - A new device for conducting tensile and compressive tests at strain rates ranging from about 20 s?1 to 250 s?1 is presented. The operation of...     

A New Methodology for Uniaxial Tensile Testing of Free-Standing Thin Films at High Strain-Rates

The investigation of strain-rate effects on the mechanical response and characteristics of thin free-standing films is crucial for the design and fabrication of more reliable MEMS devices. It is also of high interest from the scientific and materials engineering views. In this paper we present a novel apparatus and a procedure for tensile testing of thin free-standing films under a wide range of strain rates from quasistatic to high, almost comparable with those obtained in Hopkinson bar tests. To provide this capability, a unique displacement measurement method is applied and a micro device which meets several strict requirements is implemented. We describe recent results of quasistatic experiments performed on pure aluminum free-standing thin films. A high rate experiment which demonstrates the setup capabilities is also presented. The micro-device measured properties are compared with finite element analysis results.     

Multiphase Thermohaline Convection in the Earth’s Crust: I. A New Finite Element – Finite Volume Solution Technique Combined With a New Equation of State for NaCl–H2O

We present a new finite element – finite volume (FEFV) method combined with a realistic equation of state for NaCl–H₂O to model fluid convection driven by temperature and salinity gradients. This method can deal with the nonlinear variations in fluid properties, separation of a saline fluid into a high-density, high-salinity brine phase and low-density, low-salinity vapor phase well above the critical point of pure H₂O, and geometrically complex geological structures. Similar to the well-known implicit pressure explicit saturation formulation, this approach decouples the governing equations. We formulate a fluid pressure equation that is solved using an implicit finite element method. We derive the fluid velocities from the updated pressure field and employ them in a higher-order, mass conserving finite volume formulation to solve hyperbolic parts of the conservation laws. The parabolic parts are solved by finite element methods. This FEFV method provides for geometric flexibility and numerical efficiency. The equation of state for NaCl–H₂O is valid from 0 to 750°C, 0 to 4000 bar, and 0–100 wt.% NaCl. This allows the simulation of thermohaline convection in high-temperature and high-pressure environments, such as continental or oceanic hydrothermal systems where phase separation is common.     

基于电子万能试验机的新型压杆稳定实验装置

本文介绍了一种基于电子万能试验机开发的新型压杆稳定实验装置。该装置利用电子万能试验机自身传感设备,通过测量压杆两端受力与绘制端部轴向位移曲线来确定压杆失稳荷载。装置包括上、中、下三个约束部分与压杆试样部分,可实现两端固支、两端铰支、一端固支一端铰支和一端固支一端自由等4种不同端部约束型式,并且能够施加中部固支约束与压杆初始偏心。本文同时讨论了两种铰支型式,即刀刃铰支与轴承铰支对测试精度的影响。实验表明,轴承铰支测量精度比刀刃铰支高。该套装置的整体测量精度高,与理论值的相对误差最高为2%。     

高温高应变率下材料拉伸性能测试的一种新方法

为了实现高温环境下材料高应变率动态拉伸实验技术,将分离式Hopkinson杆直接拉伸装置中试样与拉杆的螺纹连接形式变成楔形连接形式,并加装了气动同步装置系统。这样,在对试样加高温时,能使靠近试样的入射和透射杆端处于较低温度。当撞击管向传递法兰运动时,气动同步装置瞬间拖动透射杆和试样,使两者之间的间隙为零,此时沿入射杆传递的入射波同时对试样拉伸加载。经实验验证,此方法可以有效实现材料高温高应变率拉伸加载。     

A New Apparatus for Large Scale Dynamic Tests on Materials

The development of an innovative apparatus, based on Hopkinson bar techniques, for performing large scale dynamic tests is presented and discussed. The activity is centered at the recently upgraded HOPLAB facility, which is basically a split Hopkinson bar with a total length of approximately 200 m, with bar diameters of 72 mm and where force pulses up to 2 MN and 40 ms duration can be generated and strain rates up to 50 s^?1 can be achieved. Several modifications in the basic configuration have been introduced: twin incident and transmitter bars have been installed with strong steel plates at their ends where large specimens can be placed. A series of calibration and quantification tests has been conducted in order to prove the reliability of the experimental technique proposed. Moreover, real tests on concrete cylindrical samples of 200 mm diameter and of up to 400 mm length have been performed. Analyses of recorded signals indicate proper Hopkinson bar testing conditions and reliable functioning of the facility.     

A Novel Contactless Flow Rate Measurement Device for Weakly Conducting Fluids Based on Lorentz Force Velocimetry

This paper presents an improved experimental setup for the contactless flow rate measurement in a weakly electrically conducting fluid on the base of Lorentz force velocimetry (LFV) and discusses the measurement results. The new setup embodies major improvements over the setup reported in Wegfraß et al. (Appl Phys Lett 100:194103, 2012). This measurement setup consists of a newly designed fluid channel with well defined flow profiles – a plug profile at the inlet and quasi parabolic profile at the outlet of the test section. Another improvement is the force measurement system which is based on electromagnetic force compensation (EMC). Furthermore an optimized Halbach array is used as a magnet system. The results of our measurements confirm the feasibility of LFV in a model fluid (salt water) with conductivities less than 10 Sm^???1 and demonstrate that the optimized magnet system increases the measurement signal. The used force measurement system had to be particularly calibrated for this purpose, so that in combination with the new magnet system design a three times higher signal resolution for the fluid velocity under laboratory conditions was achieved.     

基于多通道滤波技术的散斑条纹图正则化方法

在光测力学中,条纹图正则化是进一步提取条纹位相信息的重要基础。对于散斑条纹图来说,正则化的过程还需能够有效地抑制散斑噪声。本文提出一种基于多通道滤波技术的散斑条纹图正则化方法。通过使用多个Gabor滤波通道对散斑条纹图进行滤波,并且引入与条纹对比度有关的权重因子把各个滤波通道的滤波结果叠加起来,最终得到滤除了散斑噪声的正则化条纹图。数值模拟和实验结果表明,该方法在将散斑条纹图正则化的同时能够有效地滤除条纹图中的散斑噪声,为进一步提取条纹位相奠定了良好的基础。