Measurement systems for determining formwork pressure of highly-flowable concrete

This paper offers recommendations regarding test set-ups and measurement systems that can be used for laboratory evaluation and field testing of lateral pressure exerted by flowable concrete and self-consolidating concrete (SCC). Test results indicate that pressure sensors placed flush with the inner surface of the formwork can be used to assess the lateral pressure exerted by plastic concrete. The pore-water pressure resulting from the fluid phase of concrete can be evaluated using pore-water pressure sensors similar to the ones employed in soil mechanics. The sensors can be attached at different heights onto rigid formwork system to monitor changes in pressure with time.Sono-tubes made of cardboard are found not to be suitable for monitoring concrete pressure variations because of their flexibility which leads to erroneous values. A pressure column was developed to evaluate lateral pressure and its variations with time exerted by fresh SCC for heights of up to 10 m. Another system consisting of strain gages welded onto steel anchored bars inserted in the formwork was tested and compared to the pressure transducers system.     

Effect of W/C and superplasticizer type on rheological parameters of SCC repair mortar for gravitational or light pressure injection

The influence of pressure on the yield stress and plastic viscosity of SCC repair mortars was investigated using an adapted Marsh cone with cylindrical shear paddles. Twelve mortars proportioned with water over cement ratios from 0.45 to 0.55 and either Polycarboxylate ether (PCE), polyacrylate (PA) or polynaphtalene sulfonate (PNS) high-range water-reducing admixture (HRWRA) were prepared. Test results show that the exerted pressure, W/C and HRWRA type strongly influence the rheological response: the yield stress is mainly affected by HRWRA residual concentration, except for PCE mortars where sulfate ion concentration can play an important role. Plastic viscosity is mainly affected by solid friction between particles, the latter is influenced by HRWRA dosage and W/C. PA appears to be the most accurate HRWRA for light pressure injection, with less sensitivity to changes in pressure or W/C than PNS or PCE superplasticizers.     

Calculating the pressure force of the non-paraxial cylindrical Gaussian beam exerted upon a homogeneous circular-shaped cylinder

Forces exerted upon a dielectric cylinder of infinite length and arbitrary, or circular, cross-section by the non-paraxial cylindrical Gaussian beam are considered. The projections of the vector of the light force pressure exerted upon a dielectric cylinder of arbitrary and circular cross-section are expressed analytically. In particular, the pressure force is expressed through the coefficients of decomposition of the non-paraxial Gaussian beam into the cylindrical functions. Using numerical examples, a possibility to optically trap a circular-shaped cylinder in two oppositely directed Gaussian beams or a single non-paraxial Gaussian beam is demonstrated.     

纸基碳纳米管薄膜/叉指结构的超灵敏宽量程压力传感器（英文）

柔性压力传感器因其在可穿戴设备和人机交互界面中的潜在应用而备受关注.特别是在实际应用中,人们对具有高灵敏度、宽测量范围和低成本的压力传感器有很大需求.基于此,我们研制出了一种测量范围宽的超灵敏压力传感器.该传感器是以碳纳米管(CNT)均匀溶液直接喷在纸表面作为敏感材料,用光刻技术制成的叉指电极为结构.由于CNT大的比表面积、纸的多孔结构以及CNT与叉指电极有效接触的协同作用,压力传感器实现了从0到140 kPa的宽测量范围,并在15,000个测试周期内表现出良好的稳定性.对于纸基碳纳米管薄膜/叉指状结构(PCI)压力传感器,敏感材料与叉指电极之间的连接区域在较小的压力范围内占主导地位,而敏感材料的内部变化在大的压力区域起主导作用.此外PCI压力传感器不仅具有2.72 kPa-1(直到35 kPa)的高灵敏度,还可以检测小重量,如一颗绿豆(约8 Pa).当压力传感器贴附到人体表面时,可以监测生理信号,如手腕运动、脉搏跳动和语音识别.此外,压力传感器的阵列能够识别空间压力分布,有望实际应用于人机交互界面.     

Self-powered pressure sensor for ultra-wide range pressure detection

The next generation of sensors should be self-powered,maintenance-free,precise,and have wide-ranging sensing abilities.Despite extensive research and development in the field of pressure sensors,the sensitivity of most pressure sensors declines significantly at higher pressures,such that they are not able to detect a wide range of pressures with a uniformly high sensitivity.In this work,we demonstrate a single-electrode triboelectric pressure sensor,which can detect a wide range of pressures from 0.05 to 600 kPa with a high degree of sensitivity across the entire range by utilizing the synergistic effects of the piezoelectric polarization and triboelectric surface charges of self-polarized polyvinyldifluoride-trifluoroethylene (P(VDF-TrFE)) sponge.Taking into account both this wide pressure range and the sensitivity,this device exhibits the best performance relative to that of previously reported self-powered pressure sensors.This achievement facilitates wide-range pressure detection for a broad spectrum of applications,ranging from simple human touch,sensor networks,smart robotics,and sports applications,thus paving the way forward for the realization of next-generation sensing devices.Moreover,this work addresses the critical issue of saturation pressure in triboelectric nanogenerators and provides insights into the role of the surface charge on a piezoelectric polymer when used in a triboelectric nanogenerator.     

Analytical solutions of sensitivity for pressure microsensors

Pressure microsensors are normally designed in linear operation range. In this study, analytical solutions are presented in order to offer a set of simple equations to designers and researchers to calculate and predict the sensitivity of pressure microsensors. The pressure sensitivity is proportional to the square of the ratio of diaphragm thickness to diaphragm length, but it is inversely proportional to burst pressure. We found that the analytical solutions are in good agreement with simulation by finite element method     

Analysis of temperature/pressure sensitivity of the resonant wavelength of long-period channel waveguide gratings

A theoretical study on the sensitivity of the resonant wavelength of long-period waveguide gratings (LPWGs) to temperature and pressure is reported. Starting with the phase-matching condition of the LPWG, general expressions for the temperature and pressure sensitivities are derived. The temperature sensitivity considers the thermo-optic and thermal expansion effects, and the pressure sensitivity takes into account the elasto-optic and elastic deformation effects of the materials involved, as well as the modal dispersion effect. Focusing on the extensively studied glass and polymer waveguides, the contributions of these effects to the temperature or pressure sensitivity were roughly evaluated and illustrated in the form of histograms in order to show the roles of these effects straightforwardly. The results show that a LPWG based on a polymer waveguide is preferred to that based on a glass waveguide for obtaining high temperature or pressure sensitivity. The temperature sensitivity is dominated by the modal dispersion effect and the difference between the thermo-optic coefficients of the waveguide and the cover layer materials, while the thermal expansion effects make only a minor contribution to the sensitivity for the cases of both glass and polymer waveguides. The pressure sensitivity is dominated by the modal dispersion effect and the difference between the elasto-optic coefficients of the channel waveguide and the cover layer materials. In particular, in the case of the polymer LPWG the elastic deformation effects of the waveguide and grating materials make a moderate contribution to the pressure sensitivity and cannot be ignored. The minor contributions from the thermal expansion effects or the elastic effects may play a role in designing a temperature- or a pressure-insensitive LPWG device. Finally, the possibility that the waveguide loss affects the LPWG temperature/pressure sensitivity is discussed.     

The effect of relative refractive index on monosized particle movement under laser radiation pressure

The purpose of this study is to investigate the fundamental characteristics of particle movement under laser radiation pressure from the viewpoint of particle separation. In this study, the radiation pressure exerted on a spherical particle was calculated by using a simple geometrical optics model and the simulation of particle movement in a laser beam was performed. Further, the movement of particles under the laser radiation pressure was experimentally observed to confirm the accuracy of simulation. As a result, it was possible to simulate particle movement with the two-dimensional equations of motion by considering radiation pressure, viscous drag, gravity, and buoyancy as the forces acting on a particle. The possibility of particle separation according to the refractive index was suggested since the difference in laser radiation pressure was large enough to discriminate the particles.     

基于ANSYS的电容式测压器的数值模拟

针对目前火炮膛压测试中传感器安装结构与测压器小体积之间的矛盾,设计了一种壳体电容式压力传感器.介绍了测压器的结构及基本原理,并利用有限元分析软件ANSYS对测压器的壳体进行了静态及瞬态分析,由静态分析的结果对壳体电容进行最小二乘法拟合,拟合相关系数为0997 5,并绘制出电容式测压器的静态灵敏度曲线,在模拟膛压发生器上进行动态实验,采用上升沿校准的方法对膛压曲线进行分析.结果表明:该测压器具有良好的非线性,静态灵敏度随压力载荷的增加而增加;该设计方案是可行的,值得推广.     

Reliability-based load and resistance factor design of composite pressure vessel under external hydrostatic pressure

A reliability-based load and resistance factor design procedure for subsea composite pressure vessel subjected to external hydrostatic pressure is presented. The failure criterion for defining the performance function is considered as buckling. A sensitivity analysis is conducted to research influences of statistical characteristics of variables on the partial safety factors and the thickness of pressure vessel. The results shows the longitudinal modulus, inside radius of composite layers, unsupported length and external pressure significantly affect the design results, whereas transversal modulus, Poisson’s ratio, shear modulus and winding angle have little effects. In order to validate the design results, a filament-wound composite pressure vessel is manufactured, and the buckling test is performed. It is observed that when the applied external hydrostatic pressure is a little more than the designed critical buckling pressure, the buckling and subsequent burst behaviours occur, which shows a good agreement between the experimental and analytical results.     

Piezoresistive pressure sensing by porous silicon membrane

In this paper, the piezoresistive pressure-sensing property of porous silicon has been reported. The pressure sensitivity of a porous silicon membrane of 63% porosity and 20-/spl mu/m thickness has been observed to be about three times more than that of a conventional bulk silicon membrane of the same dimensions. The increased sensitivity is attributed to the improvement in piezoresistance due to quantum confinement in the porous silicon nanostructure. The piezoresistive coefficient of porous silicon is estimated for the first time and is observed to be about 50% larger than that of monocrystalline silicon for a 63% porosity porous silicon membrane. The response time has also been studied and observed to be significantly shorter. Power dissipation of the porous silicon pressure sensor is also much less compared to that of commercial bulk silicon piezoresistive pressure sensors.     

低频水声声压校准测试系统的设计

水声声压是声学测量中应用最广泛的参数，对声压的测量又是通过测量水听器的声压灵敏度来完成的。声学计量检定系统中对低频水声声压灵敏度的校准有多种方法，应用振动液柱法校准低频水听器的声压灵敏度是常用方法之一。伴随着新型器件、新材料和数据采集器的应用，笔者根据振动液柱法的数学模型，初步设计了一套测试系统。本文给出测试系统实现原理和系统框图，并对其不确定度进行了分析评定，同时给出测试系统能达到的技术指标。     

The measurement accuracy of the Moser and Poltz McLeod gauge

The accuracy and repeatibility of pressure measurement of the Moser and Poltz McLeod gauge have been studied. The repeatability of measurement of the mercury level position in the comparison side arm of the gauge has been tested and shown to be equal to ±0.2 mm. This value is greater than is given in the literature. A detailed study has been made to find the cause of this fact. It is estimated that the accuracy and sensitivity of the conventional optical method used for measurement is insufficient. A theory of the optical method is formulated and experimentally verified with acceptable agreement. The sensitivity of the optical system may be improved by modification of its parameters, but in no way does this kind of optical system enable adjustment to be made to a plane mercury meniscus. The pressure measurement realised with a curved mercury meniscus may be inaccurate, because of the variation possible of the surface pressure exerted by the mercury meniscus.     

总压探针性能结构敏感性分析

总压探针结构是影响探针性能的关键因素,结构对总压系数、不敏感角大小等性能影响很大.为了研究总压探针性能的结构敏感性,制作不同类型且不同关键尺寸的总压探针,包括凸嘴型总压探针和带套型总压探针.在校准风洞上对这些探针进行总压系数校准试验,发现整流罩型探针性能最好,屏蔽罩型探针次之,凸嘴型探针性能最差.通过对比试验结果,得到...     

膜片式光纤动态压力传感器的研制

为了更好地满足动态压力的测量需求,研究了一种基于法布里-珀罗（Fabry-Perot,F-P）干涉原理的膜片式光纤动态压力传感器。从理论上分析了多个反射面对F-P腔光谱的影响,提出了得到单一F-P腔的方法。进而采用机械研磨的方式对传感器膜片外表面进行粗化加工,有效解决了由多个反射面带来的光谱复杂问题。对传感器进行静态压力和动态压力标定试验,结果表明：传感器性能良好,在0~200 kPa（表压）范围内的静态压力测量误差小于等于0.5 %FS;在20~2500 Hz范围内,传感器的幅值灵敏度相对误差优于±10%。     

A vacuum pressure sensor based on ZnO nanobelt film

A vacuum pressure sensor was fabricated by assembling ZnO nanobelt film on the interdigital electrodes, and the current–voltage characteristics were measured with an Agilent semiconductor parameter tester. Under different pressures of 1.0 × 10(3), 6.7 × 10(?3), 8.2 × 10(?4) and 9.5 × 10(?5) mbar, the currents are 8.71, 28.1, 46.1 and 89.6 nA, and the pressure sensitive resistances are 1150, 356, 217 and 112 MΩ, respectively. In the range of 10(?5)–10(3) mbar the smaller the pressure is, the higher the current is. The pressure sensitive resistance of the vacuum pressure sensor increases linearly with the logarithmic pressure, and the measurement range is at least one order of magnitude wider than that of the previous sensors. Under the final pressure, the vacuum pressure sensor has maximum sensitivity (9.29) and power consumption of 0.9 μW. The sensitivity is larger than that of the previous sensor based on a ZnO single nanowire at that pressure, and the power consumption is much lower than that for the sensor based on a ZnO nanowire array. The pressure sensitive mechanism is reasonably explained by using oxygen chemisorption and energy band theory.     

Energy extraction for a self-energized pressure sensor

With the prolific use of sensors for manufacturing process monitoring, proper power supply and installation scheme has assumed an increasingly central role. Cable-based sensor powering, while commonly used on the factory floor, faces various real-world constraints. It is desirable that the power required by the sensors be "extracted" from the process being monitored itself to enable "self-energized" sensing. Such a novel design for a wireless pressure sensor for injection molding process monitoring is presented in this paper. The focus is on the energy extraction mechanism from the pressure transients exerted by the polymer melt during the injection molding process to power a piezoelectric signal transmitter, which digitally reconstructs the polymer melt pressure profile. An analytical model examining the energy conversion mechanism due to interactions between the mechanical strain and the electric field developed within the energy extraction device is first established. Using a coupled-field analysis, a numerical model is then developed to evaluate the electromechanical properties dependent upon the geometric effects of the energy extraction device. The two models are then compared with experimental results obtained from a functional prototype to evaluate the relevance of the assumptions made and the modeling accuracy. Preliminary experimental results describing the integration of the energy extraction device with the ultrasonic transmitter and the subsequent transmission of pressure information acoustically through a block of steel are also presented. The presented design introduces a new generation of self-energized sensors that can be employed for the condition monitoring of a wide range of high-energy manufacturing processes.     

Sensitivity of polyvinyl butyral/carbon-black sensors to pressure

Interdigitated capacitors have the potential to be used in pressure sensing applications requiring small size, high reliability and cost effective production. Such sensors have applications in wireless pressure monitoring of bodily fluids for the research and diagnosis of a number of medical conditions in cardiology, pulmonology and gastroenterology. In this work, the sensitivity of Polyvinyl Butyral (PVB)/carbon-black composites to pressure is evaluated with these applications in mind. The devices are fabricated by drop coating solutions containing PVB and 5, 10, 15 and 20% carbon black onto interdigitated electrodes. The optimum carbon loading for pressure sensing applications up to 2500 kPa was determined for these composites using a tensile tester. The highest sensitivity was recorded for samples with 5% carbon black. These devices were successfully integrated into a prototype wireless interface, transmitter and receiver system. The response (25 mV), hysteresis (4.78%) and repeatability (10.76%) under hydrostatic pressure ranging from 0-17 kPa were measured. Finally, the devices temperature dependence was investigated.