Dynamic Pressure Test Research Articles

A study on dynamic pressure sensor based on Pitot tube structure.

To meet the demand for the accurate measurements of the dynamic pressure of a shock wave, a composite dynamic pressure sensor design method is proposed based on the formation mechanism, propagation characteristics, special testing environment of the dynamic pressure, and Pitot tube structure. The dynamic pressure of the shock wave is evaluated by the total pressure and static pressure units installed in the composite sensor. FLUENT simulation software was used to analyze the aerodynamic characteristics of the dynamic pressure sensor, and parameters such as the structural size and inlet position of the sensor were determined. In response to the special experimental environment of the shock wave, the requirements for the dynamic pressure measurements under damage conditions were analyzed, and a dynamic pressure testing system was established. Dynamic pressure tests with four 2,4,6-trinitrotoluene [C7H5(NO2)3] equivalents of 1, 2, 15, and 20kg were carried out. The experimental results show that the proposed sensor design method can accurately and effectively measure the dynamic pressure signal, and the dynamic pressure gain multiple decreases with an increase in the proportional distance. This provides an effective testing method for evaluating the dynamic pressure damage effect of ammunition systems.

Test study on performance of U80 standardized glass curtain wall system

In order to study the air infiltration performance, water penetration performance, structural performance under wind pressure and seismic inter-story drift performance of U80 standardized glass curtain wall system, one full size test specimen was designed according to the actual engineering situation. The test specimen was composed of six-unit curtain walls with exposed frames and six-unit curtain walls with concealed frames. According to the specification of United Stated, the various performance of the test specimen was investigated. The results show that the rate of air leakage of the specimen is within allowable values under design pressure. No water leakage is observed when the water penetration tests with static and dynamic pressure tests. During the structural performance tests at 100% design wind pressure, the deflections of framing members as well as glass panels are all within the allowable deflection limits. No breakage is observed under the 150% design wind pressure. Permanent deformations of framing members remain less than 0.1% of clear span. After 3 cycles of elastic and inelastic inter-story drift performance tests, no damage is observed. The U80 standardized glass curtain wall system has great air infiltration performance, water penetration performance, structural performance and seismic inter-story drift performance. And it can be used in the practical engineering.

Research on vibration compensation technology of pressure sensors in shock wave overpressure measurement

In the dynamic pressure test of explosion shock wave, the interference of seismic wave and mechanical shock makes the interpretation of shock wave pressure measurement more difficult. In this paper, a comparative test is designed to peel off the vibration signal, and the source of vibration in shock wave measurement and the cause of acceleration parasitic effect of pressure sensor are analyzed combined with the data; Then, according to the experimental conclusions and the working principle of the sensor, a new pressure sensor with vibration compensation function is designed; Finally, the feasibility of the new sensor structure for vibration compensation is analyzed by finite element simulation. The results show that the vast majority of vibration interference signals are output by the sensor’s sensitive elements, and the new sensor with double sensitive element compensation can effectively suppress or eliminate the parasitic output caused by vibration interference. The design of the new structure sensor provides ideas for the design of vibration compensation structure of other pressure sensors, and has a certain reference value.

Experimental Study on Operational Stability of Centrifugal Pumps of Varying Impeller Types Based on External Characteristic, Pressure Pulsation and Vibration Characteristic Tests

This study performed external characteristics, dynamic pressure, and vibration tests on the closed impeller model, semi-open type impeller model, and open impeller model in order to study the influence of the impeller structure on the operational stability of the pump. According to the research findings, the external characteristics of the three impellers enjoyed favorable stability with flat curves under low flow rates. As the flow increases, the stability of the external characteristics weakens, and the poorest stability can be observed in the open impeller, while the enclosed impeller has the best stability under a large flow rate. In addition, intense pressure fluctuations arise near the casing tongue due to the dynamic and static interference between the blade and the casing tongue, causing a large amplitude of pressure pulsation near the casing tongue and the pump outlet. It can be seen that the stability of pressure pulsation of the closed impeller in the casing tongue area was the best, whereas the stability of pressure pulsation of the open impeller was the poorest. The minimum casing vibration can be found in the closed impeller, followed by the semi-open impeller, and the open impeller, with the maximum vibration. In addition, the optimum stability of rotor vibration can be observed in the closed impeller, semi-open impeller, and open impeller with similar stability of rotor vibration.

Dynamic Pressure Test and Analysis of Marine Ballasted Centrifugal Pump under Rapid Changing Conditions

Ship ballast pumps have stringent requirements for their transient characteristics. Here, the pneumatic control valve and programmable logic controller (PLC) are applied to realize the rapid reduction in flow rate for ballast pumps, and the dynamic pressure of steady and transient conditions and inner flow for the ballast pump are tested and analyzed. The results show that the dynamic pressure of each study scheme has cyclical increasing trends, however, the larger the amplitude of the flow rate reduction is, the greater the pressure increasing rate of the two measuring points. While the flow rate decreases to 0.4× Qd and 0.2× Qd, the rate of pressure increase is first fast and then slow. The dynamic pressure pulsation intensity is higher than the corresponding steady-state conditions after the transient conditions. With the increase in flow rate reduction, the characteristic frequencies of the dynamic pressure are 1APF (axial passing frequency) and 1BPF (blade passing frequency) and their harmonic frequency. The rapid decrease in flow rate causes the separation vortex in the impeller channel to be generated in advance, and the scale increases, which reduces the pulsation intensity of the pump outlet to prevent an increase in the level of broadband pulsation between 2APF and 1BPF.

Experimental study on the evolution of rock strength and sealing properties under multi-cycles alternating loading

Different from the long-term and low-speed depletion of conventional gas fields or monotonous gas injection in carbon dioxide geological sequestration, the engineering background of multi-cycle intensive injection and production of underground gas storage (UGS) makes the dynamic sealing capacity and stability of the trap cap and pipe string under alternating load become the key problem that cannot be ignored. Firstly, the basic mechanical parameters of sandy mudstone and G-grade oil well cement were determined by conventional uniaxial tests, then, different upper load levels and alternating times were set to carry out alternating mechanical tests for sandy mudstone and G-grade oil well cement stone. The deformation, failure and stress-strain curve characteristics of the two types of rocks were analyzed, and the variation laws of the strength and elastic modulus with the upper stress and the alternating times of the two types of rocks were obtained: The strength of cement stone decreases, while that of sandy mudstone increases with the increase of upper limit stress and alternating times, and the reasons for the different laws of the two types of rocks were further analyzed. Then, after undergoing different alternating times with different upper load levels, the dynamic breakout pressure tests of two types of rocks were carried out by the step-by-step method. The results show that the breakthrough pressure of the two types of rocks decreased gradually and significantly with the increase of the alternating times. The dynamic evolution prediction model of the breakthrough pressure with the alternating times was established. And because the breakthrough pressure of the cement stone in the nondestructive state exceeds the measuring range of the equipment, the initial breakthrough pressure of the cement rock was also predicted by the prediction model of the breakthrough pressure. All of these results above can be significant reference value for the sealing evaluation of gas storage site selection and the real-time monitoring after it is put into operation.

Experimental study on laminated glass responses of high-speed trains subject to windblown sand particles loading

China has built high-speed railways in desert areas. When high-speed trains run in wind-sand flows, wind pressure and sand impact increase the fracture probability of side-window laminated glass. This paper aims to explore the dynamic response and impact resistance performance of laminated glass in high-speed trains subjected to windborne sand particles loading using full-scale experimental tests. Dynamic pressure tests were carried out using an air cannon on the laminated glass to evaluate the glass response under wind dynamic pressure loading. Sandstone impact tests were conducted to study the laminated glass dynamic behavior during particle impact loading. The study results demonstrate that sand impact loading was the primary factor causing the laminated glass damage. The mixed-mode crack initiation and propagation were driven by the reflected tensile waves and Rayleigh surface waves under sandstone impacts. In addition, a statistical analysis of the scratch velocity of the laminated glass suggested that the size of sandstone and impact angle were sensitive to the scratch velocity in the sand particles impacts. This research provides practical help for designing crack-resistant laminated glass structures for high-speed trains.

Completion of the production of the W7-X divertor target modules

The installation of an actively water cooled divertor in the stellarator Wendelstein 7-X (W-7X) is mandatory to achieve stationary power and particle exhaust for pulse lengths up to 30 min. The highly loaded divertor area is made of 100 target modules distributed in ten divertor units. The target modules have mechanical support frames with attachment systems to the plasma vessel, and manifolds to distribute water equally between the target elements. A target element is designed to remove a stationary heat flux up to 10 MW/m² and is made of a CuCrZr copper alloy heat sink armored with CFC NB31 tiles. The manufacturing process, assembly and quality assessment of the last 70 target modules has been successfully completed in the Integrated Technical Centre of IPP-Garching. Some parts such as the target elements and manifolds were delivered by industry. The quality was assessed as follows: visual inspections, measurement of the 3-D CFC surface, dynamic pressure tests, He leak testing under pressure at different temperature (20 °C, 160 °C) in vacuum oven, high heat flux testing. The production of the water cooled divertor is now completed, and the mounting operation of the target modules in the plasma vessel of W7-X has started.

Progress in the production of the W7-X divertor target modules

The realization of the 19.6 m² highly heat loaded target area of the actively water-cooled divertor of Wendelstein 7-X (W7-X) requires the installation of 100 target modules distributed in ten discrete similar divertor units. A target module is water-cooled from manifolds to distribute the water equally between the target elements with flanged connections to the water supply system. A target element is made of a CuCr1Zr copper alloy heat sink armored with CFC NB31 tiles and designed to remove a stationary heat flux up to 10 MW/m². The production of the first 30 target modules has been successfully completed in the workshop of IPP-Garching. The quality of the finished target modules was systematically assessed as follows: visual inspections, measurement of the 3-D CFC target area, dynamic pressure tests, integral He leak testing under pressure at different conditions (20 °C, 4 MPa and 160 °C, 2.5 MPa) in a vacuum oven, high heat flux testing. Only 2 finished target modules did not pass the integral He leak testing and were successfully repaired.

Pressure Sensor Based on Polyvinylidene Fluoride Nanofibers Directly Written upon Silicon Substrate

A novel integration of silicon substrate and near-field electrospun polyvinylidene fluoride (PVDF) nanofibers is applied to pressure sensor for dynamic pressure measurement. PVDF is the widely known polymer with outstanding piezoelectric property, and has a wide range of applications in energy, biology, and sensors. Near field electrospinning (NFES) has obvious advantages in the preparation of direct written PVDF nanofibers with high piezoelectric performance. This paper mainly presents the preparation of pressure sensor of PVDF nanofibers on silicon substrate with integrated subtractive and additive manufacturing methods. First, a silicon substrate with diaphragm was fabricated with MEMS techniques. Then, aligned parallel PVDF nanofibers were deposited on the diaphragm with NFES as sensing element. Last, a home-made dynamic pressure testing device was used for testing the properties, and its results showed that: with the increase of pressure, the output signal was gradually enhanced, and the sensitivity of the prototype sensor was finally obtained, which is 2214.4mV/MPa (the circuit amplification factor of 20,000 times), and the optimal linearity is 2.8%.

Theoretical Calculation and Experimental Analysis on Initial Shock Pressure of Borehole Wall under Axial Decoupled Charge

This paper attempts to calculate the exact initial shock pressure of borehole wall induced by the blasting with axially decoupled charge. For this purpose, Starfield superposition was introduced considering the attenuation and superposition of blasting pressure, and the theoretical solution of initial borehole wall pressure was obtained for the upper and middle air‐decked charging structures. Then, the explosive pressure field around the borehole was measured by cement mortar models and a dynamic pressure test system, and the pressures at multiple measuring points were simulated with numerical models established by ANSYS/LS‐DYNA. The results show that the deviations between simulated and theoretical pressures are smaller than 10%, indicating the reliability of the theoretical formula derived by Starfield superposition. For the upper air‐decked charging structure, the initial shock pressure of the charging section followed a convex distribution, with the peak value near the charge centre. With the increase in the distance from the charging section, the borehole wall shock pressure in the air gap underwent a sharp decline initially before reaching a relatively constant level. The minimum pressure was observed at the hole collar. For the middle air‐decked charging structure, the pressures at both ends of the charging section obeyed a convex distribution, with the peak value near the charge centre. Finally, the author optimized air‐decked charging structure of periphery boreholes within Grade III surrounding rocks of Banjie tunnel, China, and proved the enhancement effect of the theoretical findings on smooth blasting. The research findings provide valuable references to the theoretical and experimental calculation of air column length and other key parameters of air‐deck blasting and shed new light on the charging structure determination of smooth blasting and blasting vibration control for the excavation of large‐section, deep mining roadways.

Experimental\u2013Numerical Characterization of the Fracture Behaviour of P264GH Steel Notched Pipes Subject to Internal Pressure

The rupture phenomenon of a mechanical structure requires critical consideration, because of its safety constructions. A detailed experiment of material features as well as the Young’s modulus, yield strength, material toughness or fracture resistance provides useful information to predict the life integrity of a pipe structure. This paper presents the most accurate experimental techniques for characterization of a pipe-like structure to assess its reliability. Standard traction tests, dynamic Charpy tests and pressure tests were performed to envisage the crack propagation progress. Detailed information on fracture process was obtained by a robust numerical approach using the finite element method.

Summary of the production of the divertor target elements of Wendelstein 7-X

The realization of the 19.6m2 highly heat loaded part of the divertor of Wendelstein 7-X (W7-X) requires the installation of 890 target elements. A target element is made of a CuCrZr copper alloy heat sink armored with carbon fibre reinforced carbon CFC NB31 tiles. The industrial production of the target elements by the Austrian company PLANSEE SE needed 5 years. The successful delivery of a total of 973 target elements (armored with ∼16,200 tiles) was based on an efficient quality assurance throughout the production by the manufacturer: 44 different quality examinations for 82 manufacturing steps. It was followed by an intensive quality assessment by IPP: visual inspections, dynamic pressure tests, He-leak testing in vacuum oven, high heat flux testing. The quality of the delivered elements, and in particular the reliability of the bonding between CFC tiles and heat sink, was confirmed by high heat flux testing on the basis of a statistical approach. The essential recovery of CuCrZr properties after ageing processes was confirmed by the measurement of hardness and electrical conductivity. 104 target elements (10.7%) were accepted after repair.

Experimental Investigation of Pressure Fluctuations on Inner Wall of a Centrifugal Pump

Abstract Affected by rotor–stator interaction and unstable inner flow, asymmetric pressure distributions and pressure fluctuations cannot be avoided in centrifugal pumps. To study the pressure distributions on volute and front casing walls, dynamic pressure tests are carried out on a centrifugal pump. Frequency spectrum analysis of pressure fluctuation is presented based on Fast Fourier transform and steady pressure distribution is obtained based on time-average method. The results show that amplitudes of pressure fluctuation and blade-passing frequency are sensitive to the flow rate. At low flow rates, high-pressure region and large pressure gradients near the volute tongue are observed, and the main factors contributing to the pressure fluctuation are fluctuations in blade-passing frequency and high-frequency fluctuations. By contrast, at high flow rates, fluctuations of rotating-frequency and low frequencies are the main contributors to pressure fluctuation. Moreover, at low flow rates, pressure near volute tongue increases rapidly at first and thereafter increases slowly, whereas at high flow rates, pressure decreases sharply. Asymmetries are observed in the pressure distributions on both volute and front casing walls. With increasing of flow rate, both asymmetries in the pressure distributions and magnitude of the pressure decrease.

Blast performance of water tank with energy absorbing support

The blast performance of water tank with an innovative energy absorbing support was studied to reduce the support reaction force and mitigate the damage on the water tank. The aluminum foam was adopted as the energy absorbing material, since it has high energy absorbing potential during crush plateau and safety backup zone after the compaction strain. Finite element model considering fluid and structural interaction in which the water is modeled using the Eulerian formulation and the steel tank by Lagrangian formulation is proposed. The proposed numerical model of water tank was verified by comparing the predicted results with the test results obtained from dynamic pressure tests on steel tanks filled with water. The numerical results showed that the support reaction force depends on the density and yield strength of the aluminum foams and the reaction force could be reduced significantly if softer aluminum foam was chosen. The total displacement of the water tank was increased by up to 38% due to the increase in deformation of the energy absorbing foam. The aluminum foam was proposed to absorb the blast energy and reduce the damage on the water tank. However, more damage on the water tank was observed when a very low density aluminum foam support was used. This was attributed to the increased external work done by blast loading which was higher than the energy absorbed by the aluminum foam support.

Study on clothing pressure distribution of calf based on finite element method

This study examines the clothing pressure distribution on the calf using pressure bandages with different levels of tightness. A dynamic clothing pressure test device was fabricated to obtain numerical values for the clothing pressure on key points of the calf, which were used to construct and verify a finite element model of the clothing pressure distribution. A 3D multilayer calf model was established with a simple and rapid method. After point cloud data of the calf outline were obtained by a 3D body scanner; a multilayer calf model comprising skin, muscle, and bone was fitted by reverse engineering software. The results of this model were consistent with the test values of the clothing pressure at key points. These results cannot only be a practical guide for the scientific and rational design and manufacture of tight-fitting clothing but also provide a quantitative basis for the development of clothing pressure standards.

Miniature low-pass mechanical filter for improved frequency response with MEMS microphones & low-pressure transducers

We present an acoustic low-pass mechanical filter for high intensity, high temperature silicon piezoresistive microelectromechanical system (MEMS) microphones and low-pressure (<170kPa) differential transducers that has been tuned such that only static pressure and low frequency (DC to 1–10Hz) dynamic pressures are passed to the backside of the pressure sensitive diaphragm. We present an analytical modelof the frequency response of the low-pass mechanical filter that is based on 1D wave propagation with viscous dissipation. We compare the model to experimental results obtained using a spinning valve dynamic pressure generator to demonstrate improved performance of the transducer in the frequency range of 1–2800Hz. Experimental test results yield a −3dB point at 5±4Hz for the low-pass mechanical filter. The addition of this filter enables the use of a MEMS microphone without a controlled static pressure supplied to the transducer's differential tube or the addition of several meters of tubing to prevent the transmission of low frequency content to the backside of the pressure sensitive diaphragm. The spinning valve dynamic pressure tests demonstrate a flat frequency response (±2dB, 25% deviation from the accepted input signal) from 20Hz to 2.8kHz (test limitation) for a close-coupled measurement at the front of the microphone, which is expected to remain constant over the operating temperature range of the transducer and at various static ambient pressures both above and below atmospheric pressure.

High-Performance Interface Electronic System for a 13$\,\times\,$13 Flexible Biomechanical Ground Reaction Sensor Array Achieving a Gait Ground Velocity Resolution of 100 $\mu{\rm m/sec}$

This paper describes a high-performance interface electronics system design for a high-density flexible biomechanical ground reaction sensor array (GRSA). The prototype system can be incorporated into a personal boot heel to measure real-time ground force, shear strain, and sole deformation associated with a human bipedal locomotion, thus providing zero-velocity correction to an inertial measurement unit placed in a close proximity. This approach can greatly reduce inertial error accumulation and improve positioning accuracy. The sensing electronics consist of a front-end multiplexer that can sequentially connect individual sensing nodes from a 13 × 13 GRSA to a capacitance-to-voltage converter followed by a 12-bit algorithmic ADC with a sampling rate of 66.7 k-samples/s. The entire sensor array can be scanned within 10 ms. The GRSA employs capacitive sensing scheme and is fabricated using PDMS deformable dielectric layer. The integrated sensing electronics are fabricated in XFAB 0.35 μm CMOS process and dissipate 3 mW power. The overall system sensing resolution is limited by electrical interferences coupled through long interconnect traces between a GRSA and an electronic sensing module. Dynamic and static pressure testing shows the prototype system functionality achieving a gait ground velocity sensing resolution of 100 μm/s.

Dynamic pressure testing for chronic exertional compartment syndrome in the UK military population

ObjectivesChronic exertional compartment syndrome is one of the main causes of exertional leg pain. Diagnosis is based on the history and intracompartmental muscle pressure testing during exercise prior to consideration...

Study on the Structure of Peroxide Cross-Linked Polyethylene Pipes with Several Stabilizers

Cross-linked polyethylene (PEX) pipes used in hot water supply are required for high mechanical strength and high creep resistance at high temperature. Especially PEX-a pipes which are made by peroxide cross-linking have better performance, such as creep resistance and thermal shock resistance than the pipes made by the other cross-linking method. Because the PEX-a pipes indicate the higher cross-link degree as compared with the other PEX pipes. In this study, the PEX-a pipes which were mixed with several stabilizers were tested to evaluate the effects on cross-link degree and the oxygen induction time. And also they are evaluated with the chlorine aqueous solution by the performance of the long-term hydrostatic pressure test and the long-term hydro dynamic pressure test. As a result, it was found that the combination of antioxidants for PEX-a pipes plays an important role to prolong the oxygen induction time without inhibiting the cross-linking. From the results of the 1H pulsed NMR measurement over the melting point of polyethylene, it was found that each peroxide PEX pipe with different antioxidant combinations indicated the different proportion and crosslink density of cross-linked region, in addition, that these pipes had the effective structure of cross-linking for the hydrostatic and hydrodynamic pressure test with the chlorine aqueous solution. Therefore, it was considered to be useful results for studies of the stricture of cross-linking of polyethylene.