Theoretical Calculation Value Research Articles

A new approach for determining the thickness of material plate using gamma backscattering method

This study proposes a new approach to determine the thickness of the material plate. This approach uses Monte Carlo simulation to construct the calibration curve of the ratio R versus the thickness of the material plate (R is the ratio of area under a scattering peak for a given thickness to that for a saturation thickness). Using this calibration curve, the unknown thickness of a material plate is determined by experimentally measuring the ratio R. To validate the proposed approach, we performed 39 measurements for 13 aluminum samples with thicknesses in the range of 7.00 mm–35.20 mm. The results showed that except for two measurements with relative deviations of 5.45% and 6.17%, the relative deviation for the remaining measurements is less than 5%. Besides, the method for estimating the maximum measurable thickness with the desired deviation was presented, which shows good agreement between theoretical calculation and experimental value. The obtained results are the basis for completing the thickness measurement system using semi-empirical methods in further studies.

Dynamic Analysis of sprint burst based on coupled Fuzzy Control

The dynamic analysis of sprint burst based on coupled fuzzy control is studied. through theoretical analysis and computer vision simulation, the detailed data are obtained and applied to sprint training. Computer simulation technology is used under the computer vision simulation platform, the dynamic model of sprint burst movement is analyzed, and the dynamic mathematical model of sprint explosive force joint is constructed. The limb mechanical characteristic parameters under sprint burst action are obtained. Based on the coupling control method, the characteristic analysis and information parameter estimation of sprint burst dynamics are carried out. The sprint starting model and sprint model are constructed respectively. The mathematical modeling and lower extremity mechanical analysis of two sprint burst motion modes are carried out. The torque of bone and joint is calculated, and the theoretical calculation value and simulation value are obtained. Finally, the visual simulation of sprint burst mechanics is carried out with ADAMS software, and the simulation values and theoretical values of the characteristic parameters of sprint burst dynamics are obtained, and the comparative analysis is realized. Through the simulation results, the optimal power model control under sprint burst mode can be realized. The research results will provide effective theoretical guidance for sprint training, optimize the training methods and improve the training effect.

Finite Element Analysis Model on Ultrasonic Phased Array Technique for Material Defect Time of Flight Diffraction Detection

In this study, the finite element method (FEM) for phased array technology in ultrasonic time of flight diffraction (TOFD) for the defect detection of two-dimensional (2-D) geometric materials was researched. The phased array technology generated the FEM model for the TOFD signal. We have established the finite element model by the FEM software ANSYS based on the ultrasonic mechanism about the defects and the phased array transducer. A plane strain elements have simulated the reflected signal of the defect. We can compare the error ratio between simulation and experiment by using the theoretical calculation value as the benchmark, and find the feasibility of the FEM detection.

Chalcogenide glass-ceramics for radiation shielding applications

In this paper, the radiation shielding properties of chalcogenide glass-ceramics with the chemical composition of xCsCl-(100−x)(0.5GeS2-0.5Sb2S3), where 0 ≤ x ≤ 40 mol%, were investigated by using Geant4 simulations, G-P method, and Phy-X/PSD program. Mass attenuation coefficient (μ/ρ), half value layer (HVL), removal cross section (RCS), exposure buildup factor (EBF), mean free path (MFP), and effective atomic number (Zeff) were evaluated to elucidate the radiation shielding competence of the present chalcogenide glass-ceramics. A good agreement was noted between the μ/ρ values of Geant4 simulations and theoretical calculations. At 15 MeV, we found that the HVL values raised from 5.276 cm to 5.728 cm as the concentration of CsCl increased from 0 to 40 mol%. Maximum Zeq values occurred at 1 MeV and were 42.20, 42.98, 43.76, 44.57, and 45.40 for GSC-A, GSC-B, GSC-C, GSC-D, and GSC-E, respectively. The results revealed that the chalcogenide glass-ceramics have radiation shielding properties superior to those of commercial glasses, and traditional concrete.

The Model and Experiment for Heat Transfer Characteristics of Nanoporous Silica Aerogel

Nanoporous silica aerogel insulation material is both lightweight and efficient; it has important value in the fields of aerospace, petrochemicals, electric metallurgy, shipbuilding, precision instruments, and so on. A theoretical calculation model and experimental measurement of equivalent thermal conductivity for nanoporous silica aerogel insulation material are introduced in this paper. The heat transfer characteristics and thermal insulation principle of aerogel nano are analyzed. The methods of SiO2 aerogel production are compared. The pressure range of SiO2 aerogel is 1Pa-atmospheric pressure; the temperature range is room temperature-900K. The pore diameter range of particle SiO2 aerogel is about 5 to 100 nm, and the average pore diameter range of about 20 ~ 40 nm. These results show that experimental measurements are in good agreement with theoretical calculation values. For nanoporous silica aerogel insulation material, the heat transfer calculation method suitable for nanotechnology can precisely calculate the equivalent thermal conductivity of aerogel nano insulation materials. The network structure is the reason why the thermal conductivity of the aerogel is very low. Heat transfer of materials is mainly realized by convection, radiation, and heat transfer. Therefore, the thermal conductivity of the heat transfer path in aerogel can be reduced by nanotechnology.

Research on Mechanical Properties of High-Pressure Anhydrite Based on First Principles

This article focuses on the elucidation of a three-dimensional model of the structure of anhydrite crystal (CaSO4). The structure parameters of anhydrite crystal were obtained by means of first principles after structure optimization at 0~120 MPa. In comparison with previous experimental and theoretical calculation values, the results we obtained are strikingly similar to the previous data. The elastic constants and physical parameters of anhydrite crystal were also studied by the first-principles method. Based on this, we further studied the Young’s modulus and Poisson’s ratio of anhydrite crystal, the anisotropy factor, the speed of sound, the minimum thermal conductivity and the hardness of the material. It was shown that the bulk modulus and Poisson’s ratio of anhydrite crystal rose slowly with increasing pressure. The anisotropy characteristics of the Young’s modulus and shear modulus of anhydrite crystal were consistent under various pressure levels, while the difference in the anisotropy characteristics of the bulk modulus appeared. The acoustic velocities of anhydrite crystal tended to be stable with increasing pressure. The minimum thermal conductivity remained relatively unchanged with increasing pressure. However, the material hardness declined gradually with increasing pressure.

A UHV standard with option to be used as partial pressure standard

Partial pressure measurement has become indispensable for many applications and contributes to the complete characterization of a vacuum system. In this work, an ultrahigh vacuum (UHV) standard was established for calibrating partial pressure analyzers as a partial pressure standard, and a new method was introduced to generate standard partial pressures, which was named ‘the dynamic expansion method based on static expansion vacuum standard injection mode’. The method can produce standard partial pressures in the range from 10–5 Pa to 10–10 Pa. The relative standard uncertainty budgets of generated partial pressures (k = 1) were in the range from 2.8% up to 5.0% from 10–5 Pa to 10–9 Pa for nitrogen. Employing this method, the sensitivity calibrations of quadrupole mass spectrometry (QMS) were performed in the partial pressure range of 8.62 × 10−5 Pa to 1.51 × 10−10 Pa with single inert He, Ar, and Kr gas in secondary electron multiplier (SEM) mode. Similarly, the calibrations were carried out using active gases (H2, CH4, N2, O2, and CO2) in the range 8.56 × 10−5 Pa to 1.50 × 10−9 Pa. Additionally, the SEM gains were calibrated for these high-purity gases, on the basis of SEM gain coefficients. QMS sensitivities equivalent to Faraday cup mode were attained, and it was found that the results were approximately consistent with those of previous studies. The data were also in agreement with our theoretical calculation values excluding CH4.

Enhanced formation of α-Al2O3 at low temperature on Cr/Al coating by controlling oxygen partial pressure

α-Al2O3 is one of the most promising hydrogen permeation barriers due to its high melting point, stable chemical properties, and good machinability. However, α-Al2O3 synthesis usually requires temperatures above 1200 °C, which weakens the properties of the substrate material. Therefore, low-temperature preparation of α-Al2O3 is crucial. Most studies have reported that using Cr2O3 as a template is a good method to promote α-Al2O3 formation. However, the formation of monolithic Cr2O3 is still a challenge. To address these problems, a Cr/Al coating was introduced that was successfully deposited on stainless steel. A new composite coating was formed by the subsequent oxidation conversion under ultra-low-partial-pressure conditions via decomposing the oxygen precursors (nickel/iron oxide) in a closed environment. The results from X-ray diffraction, Raman spectra and other methods showed that the content of α-Al2O3 was enhanced at 2.6 × 10−24 Pa (theoretical calculation value) and promoted the formation of near-stoichiometric Cr2O3. In addition, the ultra-low partial pressure condition could promote the diffusion of defects on the interface between metastable Al2O3 and corundum crystal structure Cr2O3, by which the α-Al2O3 was successfully formed at 600 °C due to the template effect of Cr2O3. This work provides a new approach for the low-temperature preparation of α-Al2O3.

Structural Simulation and Fatigue Life Analysis of the Step Attenuator

In this paper, the internal reed of a type of wideband coaxial step attenuator was studied. The research unit was modeled, and the finite element ANSYS-Workbench simulation software was used for simulation analysis to clarify the stress status of the reed and determine the dangerous position. Based on the theory of structural fatigue damage, the nominal stress method is used to predict the theoretical life of the reed, and N-code fatigue simulation software is used for fatigue simulation. The result shows that the maximum stress of reed connector occurs at the fixed end of the reed, which is the dangerous part. The theoretical calculation value of maximum stress is 318.54MPa, the simulation value of finite element is 395.53MPa. The theoretical prediction of fatigue life is 8.65e6, and the simulation life of N-code is 7.003e6.

Effect of Process Conditions on Residual Stress in Laser-MAG Welding of High Strength Steel

In this paper, the finite element method is used to simulate and analyze the laser-MAG composite welding of 4mm thick cylinder of high strength steel 30CrMnSiA, and the variation law of welding residual stress under different technological conditions is obtained. By comparing and analyzing the welding residual stress of the actual test plate by blind hole method with theoretical calculation value, the two methods are in good agreement, and the rationality of the model is verified.

Simulation of a Hall Effect Thruster Using Krypton Propellant

The multifluid computational framework Hall2De is updated to perform simulations of Hall thrusters operating with krypton propellant. The implementation is validated by comparison to past experimental measurements obtained for the NASA-300M thruster that operated with both xenon and krypton. For xenon, the computed thrust matches experimental values to within 6%, whereas for krypton the difference is only 1.8%. From simulations at the same thruster power level, the krypton propellant specific impulse is 15% higher than that for xenon, and the thrust is only 17% lower than that for xenon. These results are consistent with a simple theoretical calculation and experimental values. Next, the unshielded H6 thruster, which has not yet operated experimentally with krypton propellant, is also simulated for both gases at the same power level. The flow rate for krypton is reduced by 28% to maintain the 6 kW power level used for xenon propellant. The performance trends observed are consistent with the NASA-300M thruster simulations. Although the singly charged ion current fraction for xenon is 11% lower than that for krypton, for the doubly and triply charged species the trend is reversed. This behavior is expected when considering the relative differences in cross sections between the various ionization processes.

МАТЕМАТИЧНА МОДЕЛЬ СИСТЕМИ РАННЬОГО ВИЗНАЧЕННЯ АВАРІЙНОСТІ СКЛАДНИХ ТЕХНОЛОГІЧНИХ ВИРОБНИЦТВ НА БАЗІ АВТОНОМНИХ П’ЄЗОТРАНСПОНДЕРІВ

For the early detection of emergencies and accidents on potentially hazardous or high-risk objects in complex technological processes, the changes in technical parameters of the equipment, such as vibration changes, can be used. To do this, we propose to use piezoceramic transducers. However, to build a complete system of complex technological process, it is necessary to use a large number of such sensors, which should work in a single identification system. To do this, the paper proposes a mathematical model of the system of preliminary determination of the accidents in complex technological industries, which is built on the principle of fixing the vibration changes of the equipment that precedes any accident. The model obtained takes into account: the number of control points at which vibration parameters are determined, the number of piezotransponders, the triggering threshold for each transponder, the energy previously accumulated in the system, the matrix of values of the possible placement of piezotransponders at control points, the time of transmission of the alarm, vectortape of fixation of transmission of an alarm signal identification, the time of transmission of an alarm signal, parameters of vibration at control points.In order to check the adequacy of the mathematical model obtained, several experiments have been performed where the rotational motion of the working shafts is used as the source of vibration. Console piezoelectric transdurers based on bymorph piezoelectric elements are used as piezotransponders. When performing experiments to change the vibrational effects, the speed of rotation of the working shafts and the mass of the fixed eccentrics varies. The results of the experiments have shown that the energy accumulated due to vibration in the piezotransponder is sufficient for the transmission of emergency information, with the difference between the values of theoretical calculations and the experimentally obtained data not exceeding 23 %.The resulting mathematical model can be used by developers to build effective anti-crash systems on complex technological productions of potentially hazardous or high-risk objects.

Experimental study on jet pulse assembly design and numerical simulation

Jet pulse assembly is one of the main components of jet hydraulic oscillator. The pressure wave characteristics produced by jet pulse assembly have an important influence on the performance of the tool. In this paper, the structure and working principle of jet pulse assembly are studied, the mechanical analysis model of piston rod is established, the dynamic resistance ratio formula of jet pulse assembly is deduced, and the numerical simulation test of 89-mm jet pulse assembly structure parameters is carried out. The results show that the piston rod downward stroke is driven by both the jet element driving force and the throttle plate load driving force, and can stably descend. The driving force of the piston rod upward stroke jet element is opposite to the load acting force of the throttle disc, and the jet driving force needs to be greater than the load resistance of the throttle disc to stably ascend. The dynamic resistance ratio formula is deduced. When the area of the end of the piston rod is reduced, the resistance of the throttle disc is reduced and the jet power is increased, thus solving the problem of insufficient power of the piston rod in the upstroke and ensuring the normal operation of the tool. Ten groups of numerical simulation tests were carried out, and it was found that the pressure amplitude and pressure drop of the tool decreased significantly with the increase of the tool size, and the error between the numerical simulation value and the theoretical calculation value was less than 9%, which verified the correctness of the theory. It is suggested to select tools on site according to the drilling construction situation to ensure the drilling effect.

Investigation on a semi-active hydraulic damping strut to reduce vehicle in situ shift vibration

In order to reduce the shock and vibration caused by torque disturbance of the gearbox in vehicles equipped with automatic transmission in the process of in situ shift, a novel semi-active hydraulic damping strut is introduced in the powertrain mounting system. The dynamic response evaluation indexes of vehicle in situ shift are put forward, and a 13-degree of freedom vehicle dynamic model including the semi-active hydraulic damping strut is established. The optimized dynamic characteristic parameters are acquired according to the principle of sharing force and the 13-degree of freedom vehicle dynamic model. The dynamic response evaluation indexes with and without the semi-active hydraulic damping strut are calculated using the 13-degree of freedom vehicle dynamic model in the process of in situ shift, and the calculation results show that the vibration of a vehicle can be reduced by the introduction of a semi-active hydraulic damping strut. Experiments are carried out to analyze the vibration response of the vehicle with and without a semi-active hydraulic damping strut, and the results show that the shock and vibration of the vehicle are reduced by introducing the semi-active hydraulic damping strut. The theoretical calculation values of active-side acceleration of the engine mount and torque strut are consistent with the experimental values, which show that the 13-degree of freedom vehicle dynamic model is reasonable.

Research on deflection monitoring for long span cantilever bridge based on optical fiber sensing

Abstract There are a lot of shortages in monitoring the deflection of long span cantilever bridge during construction period, such as numerous construction procedures, difficult wiring and failure in collecting data in real-time. In order to overcome these shortages, a Fiber Bragg grating-based inclination sensor is designed, which is based on “pendulum-equal strength beam”. Furthermore, a deflection monitoring structure based on the inclination sensor is designed and it can measure deflection by inclination change. The deflection monitoring structure prototype is manufactured and the relevant performance tests show that the sensitivity is 10.566 pm/mm and the fitting error is 0.9997 ranging from −100 mm to 100 mm. Compared with the theoretical calculation value, the deviation of sensitivity coefficient of the sensing structure is about −0.68%, which can meet the accuracy requirements of deflection measurement for long span cantilever bridge construction health monitoring. Apply the designed deflection monitoring structure in the cantilever bridge of Shaba An’ning River Bridge on Line 2 of Chengdu-Kunming Railway, and monitor the deflection changes of each construction segment in three key processes including hanging basket moving forward, concrete pouring and pre-stressing tensioning. The feasibility of the deflection sensing structure in cantilever bridge construction monitoring is verified.

Experimental study on cyclic pure shear behaviour of hat-section cold-formed steel member buckling-restrained steel plate shear walls without effect of frame

The hat-section cold-formed steel member buckling-restrained steel plate shear wall is a new type of lateral force resisting system that uses hat-section cold-formed steel member to restrain out-of-plane buckling deformation of the steel plate shear wall. Additionally, the integration of building function and structural function can be realized by externally pasting OSB sheet and filling sound insulation material. In order to investigate the cyclic pure shear behaviour of the hat-section cold-formed steel member buckling-restrained steel plate shear wall, the lateral force resistance contribution of the edge rigid connection frame was removed and the quasi-static tests of seven hat-section cold-formed steel member buckling-restrained steel plate shear wall specimens under reciprocating shear load were carried out. The test results indicated that the hat-section cold-formed steel members blocked the diagonally full-length tension band of the steel plate shear wall and reduced the out-of-plane deformation degree of the steel plate shear wall; In addition, the reinforcement of the restraint construction of hat-section cold-formed steel member could gradually improve the deficiency of the hysteresis curve pinching of pure steel wall and promote the energy consumption of structure; Furthermore, the hat-section cold-formed steel member restraint had different degrees of improvement on the initial stiffness of the steel plate shear wall, enhancement of post-yield shear capacity, ultimate shear capacity and ductility, and evidently inhibited the stiffness degradation of the specimen; The externally attached OSB sheet exhibited significant applicability under reciprocating shear load. Finally, the test ultimate shear capacity results of each specimen were compared with the theoretical formula calculation values, and the reliability of the shear capacity calculation formula was evaluated.

Optimization Analysis of Minimum Flat Curve Radius of High Speed Maglev Line with Design Speed of 500 km/h

Firstly, based on the traditional circuit design method, the theoretical calculation value of the minimum radius of the flat curve under the design speed of 500 km/h is calculated in this paper; Through the analysis of the structural characteristics of the TR08 high-speed maglev train and the degree of freedom of each component, a 129-DOF high-speed maglev vehicle-line dynamics model is established by using the multi-body dynamics software SIMPACK; And using the modle to simulate and analyze the influence of the radius of the flat curve on the dynamic performance of the vehicle. Finally, according to the simulation results, the theoretical calculation of the minimum radius of the flat curve is optimized and adjusted, and the minimum radius recommended value of the flat curve that satisfies the dynamic evaluation index is obtained. After the simulation optimization, the unbalanced lateral acceleration and the vertical acceleration dynamic response of the vehicle passing through the designed curve section are significantly reduced, and the ride comfort of the passengers is good.

Coupling Vibration between Wind-Induced Internal Pressure and a Flexible Roof for Buildings with a Dominant Opening and Background Leakage

After considering the combination of internal pressure and external pressure acting on the roof, the coupling dynamic equations to describe the relationship between wind-induced internal pressure and flexible roof are reviewed and further refined. The internal pressure responses and the first order modal response of a flexible roof can be evaluated by the coupling equations. Wind tunnel test was carried out on an aeroelastic roof model which was treated as a single-degree-of-freedom system. Three factors, approaching wind velocities at the center of the dominant opening, acceleration responses at dominant opening areas and background leakages, which have effects on roof acceleration responses were studied. On this basis, the effectiveness and calculation precision of the coupling equations were verified. Results show that the root-mean-square (RMS) value of roof acceleration increases with the increase of the approaching wind velocity and dominant opening area, and in background leakage decreases. Meanwhile, theoretical calculation values of RMS internal pressure and RMS acceleration response corresponding to the first order modal of flexible roof agree well with the wind tunnel experimental data.

STUDY OF PROCESS CONTROL ON PIEZOELECTRIC DROP-ON-DEMAND EJECTION

The size and uniformity of micro-droplets are key factors influencing the quality of the molded part by micro-droplet ejecting additive manufacturing technology. In this paper, a piezo-actuated micro-droplet ejection device for generating uniform micro-droplets is studied. The piezoelectric material drives the flexible diaphragm to vibrate and pushes the liquid out of the nozzle and produces micro-droplets. The amplitude of the diaphragm under different control parameters and its influence on the size and uniformity of the generated micro-droplets are investigated by numerical simulation and experiment. The results indicate that the amplitude of the diaphragm is affected by the driving voltage and the piezoelectric frequency and the experimental value of the diaphragm's center point amplitude is less than that of the theoretical calculation value which is mainly influenced by the piezoelectric frequency. The amplitude of the diaphragm will change the pressure inside the nozzle, which leads to the varied sizes of the micro-droplet. When the driving voltage is constant, the diaphragm has the maximum amplitude for the piezoelectric frequency at 10 Hz. As the amplitude of the diaphragm increases, droplets can be generated when the liquid velocity at the orifice and the length of the liquid column increase to a critical value. As the amplitude of the diaphragm continues to increase and the length of the liquid column at the orifice is beyond to a critical value, a satellite micro-droplet is formed. When the amplitude range of the membrane is between 30 $\mu $m and 42 $\mu $m, micro-droplets can be stably formed whose uniformity and size meet the demand well, and the minimum generating micro-droplets size is 339.8 $\mu $m. The maximum change rate of droplet diameter and adjacent two droplets are 0.29% and 2.67% respectively. Results are benefit to promote the uniformity of micro-droplets and will provide a reference for the development of piezoelectric droplet ejection devices.

Experimental study of the effect of seepage on radon exhalation in circular tubular porous emanation media

Radium, which is naturally present in many rocks, decays to the radioactive gas radon, which is then exhaled from the surface of underground tunnels and other underground buildings and is a major source of human exposure to radioactivity. A mathematical model for the migration of radon from a circular tubular emanation medium was established based on the seepage–diffusion migration theory for radon in porous emanation media, such as artificial retaining walls and the surrounding rocks in these locations. An analytical solution for the distribution of radon concentrations and the calculation formula for the radon exhalation rate under steady-state conditions were then obtained. An experimental device was designed to determine the radon exhalation rate under different pressure gradients. The theoretical calculation values for the radon exhalation rate and the total amount of radon exhalation are in good agreement with the experimental results. The radon exhalation rate at the low-pressure side increases with an increase in seepage velocity (pressure difference), while the radon exhalation rate at the high-pressure side is on the contrary. The total amount of radon exhalation increased over time with an increase in the seepage velocity and tended towards a maximum value.