Calculation Of Axial Forces Research Articles

Calculation and Application of Ultimate Lateral Friction Resistance of Concrete Piles under Different Soil Layer Materials

In practical engineering applications, it usually gets the expected value of the ultimate side friction of concrete piles by the empirical parameter method. The expected value of the ultimate side friction of concrete piles cannot achieve maximum optimization due to the complexity of formation conditions and the lack of experience of technicians. To accurately obtain the ultimate lateral friction resistance of piles in homogeneous soil layers, optimize the standard value of pile ultimate lateral resistance, ensure construction safety, and save construction costs, the research method combining theoretical derivation and on-site measurement data validation was done in the manuscript. Based on the shear strength of the pile-soil interface of different materials and the shear performance of the soil around the pile, a calculation equation for the standard value of the ultimate lateral friction resistance of concrete piles in different homogeneous soil materials was derived and applied to the equation for calculating the ultimate bearing capacity of foundation pile and the axial force of pile. Finally, based on an engineering example, the calculated results were compared with the measured resultsThe research results show that in thick coarse-grained soil, as the foundation pile is short, the ultimate bearing capacity of a single pile obtained using the calculation equation deduced in this paper is less than that obtained using the empirical equation provided by the national code. In a deep cohesionless homogeneous soil material, the concrete pile shaft axial force calculation using the pile shaft axial force calculation equation deduced in this paper is close to the measured value when the foundation pile bears the ultimate load; the proposed new method has good application value.

Axial Force Calculation Model for Completion String with Multiple Point Resistances in Horizontal Well

Frequent accidents may happen during the string run-down and pull process due to the lack of accuracy in the prediction of string force analysis. In order to precisely predict the completion string axial force in horizontal wells, a new model is established, and an in-house software has been developed. The model aims to predict the multiple local resistances that occur at different points on the completion string, which makes up for the technical defects of the commonly used software. It can calculate resistance at different points of the string, which will lead to varying hook load amplification. This method can also predict the axial force of the completion string. By changing the hook load, location, and direction, the resistance can be determined more accurately. Based on the calculation and analysis, the relationship between local resistance, the blocking point, and the amplification factor is also obtained. Furthermore, this model is used to analyze the local resistance of a horizontal well with multiple external packers in the low-permeability Sadi Reservoir of Halfaya Oilfield, Iraq. The recorded data from in-site operations are compared with the predicted results from this model. The results show that the relative errors between the recorded data and model calculation are within the range of 10%, which indicates that the calculated values are reliable. Meanwhile, the results indicate the success of the subsequent completion design and the construction of the oilfield.

Numerical calculation and analysis of axial force of multistage centrifugal submersible pump

Abstract The study of axial force has been a hot spot in fluid mechanics research, and the magnitude of axial force directly affects the stability, safety, and efficiency of submersible pumps. This paper takes 200QJ50 multistage centrifugal submersible pump with spatial guide vane as the research object, simulates and numerically calculates the internal flow field of multistage submersible pump based on Standard k-ε turbulence model, a SIMPLE algorithm, and high-resolution format through CFX software, analyzes the distribution law of static pressure and velocity field of the multistage submersible pump under 0.7Qd , 0.8Qd , 0.9Qd , 1.0Qd and 1.1Qd working conditions and compared the theoretical and simulated values of the corresponding axial force for each working condition. The results show that with the increase of the flow rate, the axial force of the multistage submersible pump shows a downward trend; the axial force generated by the first stage impeller has a larger proportion, and reaches the maximum value in the design condition; the traditional axial force calculation formula can more accurately predict the axial force under the design condition, and the error is 6%. The results of this study can provide references for the design and optimization of multistage centrifugal submersible pumps.

Calibration of CFD grid for simulating the impeller clearance flow and axial hydraulic force of centrifugal pump

The axial hydraulic force of centrifugal pump is an important parameter affecting pump performance. The force mainly includes the force inside impeller and in clearance. Due to the special structural characteristics of the clearance, the influence of grid discretization method on the calculation of axial force in the clearance is not fully understood. Therefore, based on the Reynolds-averaged method with shear stress transport turbulence model, an orthogonal experiment was designed to compare the correlation coefficient of velocity and pressure distribution between shear stress transport model and large eddy simulation models. A more suitable grid discretization strategy was found by artificial neural network for grid calibration. When the strategy is applied to the entire centrifugal pump, the prediction of axial force has high accuracy. The range analysis shows that the grid node number in the wall-wall direction has the greatest impact on velocity distribution. When the mesh parameters are in a certain range, it can compromise between the simulation accuracy and computational resource. The Reynolds-averaged model based simulation is proved accurate in capturing the complex velocity and pressure field inside clearance. The entire pump model is also used for the verification after the calibration of grid. The typical axial force law can be found under different flow rate conditions. This study provides a significant guidance in determining the grid scheme for accurate prediction of centrifugal pump’s axial force. It makes the computational fluid dynamics simulation feasible in the initial design of centrifugal pump which specifically considers the axial force problem.

Analytical Modeling and Design of Novel Conical Halbach Permanent Magnet Couplings for Underwater Propulsion

Permanent magnet couplings can convert a dynamic seal into a static seal, thereby greatly improving the stability of the underwater propulsion unit. In order to make full use of the tail space and improve the transmitted torque capability, a conical Halbach permanent magnet coupling (C-HPMC) is proposed in this paper. The C-HPMC combines multiple cylindrical HPMCs with different sizes into an approximately conical structure. Compared with the conical permanent magnet couplings in our previous work, the novel C-HPMC has better torque performance and is easy to process. The analytical calculation method of transmitted torque of C-HPMC is proposed on the basis of torque calculation of the three common types of HPMCs. The accuracy of the torque calculation of the three HPMCs is verified, and the torque performance of the three HPMCSs of different sizes is compared and discussed. The “optimal type selection” method is proposed and applied in the design of C-HPMC. Finally, on the basis of torque analysis calculation and axial force calculation, a complete flowchart of the design and performance analysis of C-HPMC is described.

Relationship between Axial Width and Flow Characteristics of Pump Chamber in Double Volute Centrifugal Pump

The axial width of pump chamber has a great influence on the flow characteristics of the pump chamber in the centrifugal pump. A single-stage single-suction double volute centrifugal pump with a semi-open impeller was selected as the object. For the 6 different pump chamber axial width, it was concluded that the pump chamber pressure at the different angles (0°, 90°, 180°, 270°) along the radial variation characteristics according to the contrast analysis of the pump cavity pressure field, velocity field distribution. The correlation between the pump chamber pressure and the impeller radius was revealed. The tangential velocity and radial velocity along the axial distribution curves were draw. The results show that when the axial width of pump chamber increases from 23.9 mm to 43.9 mm, the pressure value of the same radial position increases gradually. The radial pressure difference is decreasing. At the same axial width of pump chamber, the pressure mean increases along the radial approximately parabola. The tangential velocity of different angular directions has little difference in axial distribution. The mean of dimensionless tangential velocity in the turbulent core area decreases from 0.32 to 0.19 with the increasing of pump chamber axial width. The radial velocity varies is greatly along the axial direction. There are eddies at the directions of 0ånd 180°, but the mean of radial velocity in the turbulent core area is about 0. This research provides the reference for centrifugal pump hydraulic design, structural design and the accurate calculation of axial force.

Critical upheaval buckling forces of sandwich pipelines with variable stiffnesses of pipe material

The upheaval buckling of sandwich pipelines may cause damage to the core material in the buckle, and the changed pipe material stiffness makes such instability problems more complicated. In this paper, the complementary error function is selected to describe the reduction in the stiffness of the pipe material along the sandwich pipe buckle to propose a new buckling characteristic equation for the sandwich pipeline. Green's function for the differential equation for the deflection curve of the variable stiffness of a beam is utilized to portray the upheaval buckle configuration for a precise critical buckling axial force calculation. Three classical imperfection shape functions to account for possible undulations of the seabed or the furrow bottom are induced to modify the critical buckling axial force considering out-of-straightness effects.

Spectrum Analysis and Optimization of the Axial Magnetic Gear with Halbach Permanent Magnet Arrays

In order to study the contribution of each harmonic to the output torque and axial torque of the axial magnetic gear with Halbach permanent magnet arrays (HAMG), torque and axial force calculation formulas of the HAMG are proposed based on the air-gap flux density distribution of the HAMG. Because of the difference of the air-gap flux densities at different radii, two simplified torque and axial force calculation formulas are proposed and compared. To improve the torque capability of the HAMG, parametric analysis of eight dimensional parameters is firstly conducted. By parametric analysis, six parameters such as the inner radius have been found to have obvious impact on the output torque and output torque density of the HAMG. The optimization using Maxwell software is then executed for maximizing the output torque density of the HAMG. The output torque density of the optimized HAMG is improved from 78.1 kNm/m3 to 93.3 kNm/m3 with an increase of 19%. Furthermore, spectrum analysis is also presented to illustrate the significant output torque improvement based on the torque calculation formulas.

Research on the Compatibility Between Washover String and Casing in Directional Casing Damage Wells

Nowadays extracting or changing casing is a mature technique used in vertical wells, which can solve the problems of casing breaking and corrosion. But for directional casing damage wells, the phenomena of milling head cutting casing often happen because of the stiffness difference between washover string and casing. In order to evaluate the compatibility between washover string and casing, some studies have been made in this paper: (1) an axial force calculation model is established, which is used for mechanical analysis of washover string in the condition of well wall outside and casing inside. (2) a turning force calculation model is obtained through mechanical analysis of the milling head-ball-casing assembly. The calculation model can reflect the compatibility between washover string and casing. And on this basis the contact stress of the assembly can be simulated with Comsol Multiphysics. When the contact stress exceeds casing’s yield stress, yield failure happens. A poor compatibility will result in casing to be cut off and the interruption of extracting operation. The research results provide a method for evaluating the compatibility between washover string and casing.

Bat algorithm for optimization of reinforced concrete columns

AbstractIn structural mechanics, when the design contains two different materials with opposite mechanical behaviours and costs, the optimum design cannot exactly found. In that case, numerical optimization algorithms are a good source. Reinforced concrete design shows that behaviour since concrete is a cheap material comparing to steel while the tensile strength of concrete is very low to use. The cross sections are effective on the stresses and balance of tensile and compressive forces. This situation shows the importance of the dimension optimization of reinforced concrete members. Also, the number and size of the reinforcements need an optimization. The place of the reinforcements is effective on the place of tensile forces in the calculation of axial force and flexural moment capacity. In this paper, reinforced concrete columns are optimized for the cost minimization by employing a bio‐inspired metaheuristic algorithm called bat algorithm. The idealization of the echolocation behaviour of bats is the inspiration of the bat algorithm. Differently from the algorithms, the bat algorithm uses global and local optimization with a changeable probability. The optimization process considers the security measures and slenderness of the according to the design regulation called ACI 318. The slenderness is taken into consideration by using a magnified design flexural moment, which is factored by a value defined according to the buckling load and axial load of columns. The proposed approach is applied for different numerical cases and the results are compared with the approach using harmony search algorithm. The present approach is effective for the optimization problem. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The Structure Parameters Optimization of Variable Direction Joint During Extracting Casing in High-Inclination Directional Well

During extracting casing in high-inclination directional well, the existence of variable direction joint (VDJ) can enhance the build-up ability of washover string. And it can increase the compatibility between washover head and casing to some extent. However, too large or too small bending angle of VDJ will result in that the washover head cuts the upper and bottom parts of casing. Therefore, it is necessary to design reasonable bending angles for casing damage wells with different borehole curvature. In this paper, through the geometrical and mechanical analysis on the washover string with VDJ, a build-up rate calculation model and an axial force calculation model are established respectively. Moreover, through establishing the finite element model of washover tubing-ball-casing combination, the contact stress distribution is obtained. Under the critical condition of casing breaking when the contact stress exceeds the yield stress, the reasonable bending angle of VDJ matching with different casing damage well is designed. We can conclude that the research results play an important significance for in assuring the safe extracting casing. Key words: Variable direction joint; Safe extracting; Parameters optimization; Casing damage well

Analysis of Bearing Mechanics Characteristic of Wind Turbine

The transmission gear, bearing and hub and important component of wind field prone to fatigue failure under thermal load and alternating stress. The core component of MW class wind turbine gear box is bearing parts, according to the Betz principle bearing dynamic characteristic is analyzed including deduction and calculation of axial force and radial force, this paper simulates contact stress under the typical conditions of cylindrical roller bearing by finite element method, meanwhile analyzes the stress variation of the rolling body and a holding frame, the simulation results show that bearings bear a greater impact load in the starting process, retainer and rolling body produce large instantaneous stress value in the process, while the stress value is relatively small in the smooth operation and at braking speed, The simulation results has some practical value in engineering of optimization design.

NUMERICAL CALCULATION AND EXPERIMENTAL STUDY OF AXIAL FORCE IN A DEEP-WELL CENTRIFUGAL PUMP

In the operation process of centrifugal pumps, especially in multi-stage pumps, axial force is one of the main factors which affect the pump safety and reliability. This paper presents the axial force study in a deep-well centrifugal pump (DCP) with theoretical calculation, numerical simulation and experimental measure. Three different calculation formulas were respectively introduced and used in the model pump. The calculated results were compared and analyzed with the numerical simulation values and experimental results, and the detailed numerical simulation methods and experimental configuration were explained. Finally, the more accurate formula for calculating the axial force in oblique flow centrifugal impeller was selected out. At the rated flow point, the deviation of the axial force obtained by numerical simulation and the experimental value is approximately 3.8%, and the calculated result of selected formula only less than the experimental results of 2.6%. The results provide a theoretical basis for the axial force calculation in the centrifugal impeller design process.

Axial force calculation of passive magnetic bearing

Axial magnetic force calculation between two ring permanent magnets is presented in the paper. One magnet is magnetized in radial direction while the other one is magnetized in axial direction. Configuration like this one resembles the one passive magnetic bearing has. Force calculation is performed using semi analytical approach based on fictitious magnetization charges and discretization technique. For comparison purposes, and in order to check preciseness of the method applied, Finite Element Method (FEM) results were used.

Ray optics calculation of axial force exerted by a highly focused Gaussian beam on a left-handed material sphere

Theoretical expressions and numerical calculations of axial forces for a left-handed material sphere, exerted by a highly focused Gaussian beam, in the ray optics regime are presented. Comparison is made between a dielectric sphere and a left-handed material sphere. The position at which the maximal magnitude of the axis force occurs is determined by the beam and the sphere parameters. A very strong axial force can be obtained from a low refractivity of a left-handed material sphere, exerted by a highly focused Gaussian beam, which is hundred times larger than that of a dielectric sphere.

Calculation Formula Optimization and Effect of Ring Clearance on Axial Force of Multistage Pump

Since overlarge axial force can damage the pump, accurate calculation formula of axial force on pump is very significant. The traditional formula is based on the assumption that the leakage amount of the pump is zero and the angular speed of fluid in the pump chamber rotates at half the impeller rotation’s angular speed. In order to propose an accurate calculation formula, the whole flow fields of multistage pumps with three different ring clearances were calculated by using Computational Fluid Dynamics (CFD). The results indicate that the axial force on first-stage impeller is larger than that on the second. Along with the change of ring clearance, the static pressure distribution on the shroud of impeller changes at the same time, which leads to the value change of axial force. Meanwhile, angular speed of the fluid in the pump chamber is changing. Therefore, this research works out the reason why the error of traditional axial force calculation is large when the amount of leakage is relatively high. At last, an accurate calculation formula of axial force on pump is obtained through the verification of numerical simulation and experiment.

Shearing Stress Model of Damage Bolt in Tunnel

When bolt is damaged, character of stress is different from character of shear stress integrated bolt. Firstly, Based on the displacement formula of the tunnel surrounding rock，the shear stress and axial force calculation formula of integrated bolt are educed. Subsequence, based on the BOUSSINESG formula of displacement, models on fully grouted bolt shear stress and axial force of uniform rock are educed under pullout load. Consequently, the author deduces shear stress model of bolt damage (completely void of bolt and grouting), combining modes on shear stress and axial force of integrated bolt and shear stress model of bolt under pullout load..

Dynamic characteristics analysis of the offshore wind turbine blades

The topic of offshore wind energy is attracting more and more attention as the energy crisis heightens. The blades are the key components of offshore wind turbines, and their dynamic characteristics directly determine the effectiveness of offshore wind turbines. With different rotating speeds and blade length, the rotating blades generate various centrifugal stiffening effects. To directly analyze the centrifugal stiffening effect of blades, the Rayleigh energy method (REM) was used to derive the natural frequency equation of the blade, including the centrifugal stiffening effect and the axial force calculation formula. The axial force planes and the first to third order natural frequency planes which vary with the rotating speed and length were calculated in three-dimensional coordinates. The centrifugal stiffening coefficient was introduced to quantitatively study the relationship between the centrifugal stiffening degree and the rotating speed, and then the fundamental frequency correction formula was built based on the rotating speed and the blade length. The analysis results show that the calculation results of the fundamental frequency correction formula agree with the theoretical calculation results. The error of calculation results between them is less than 0.5%.

Railway Track Performance Monitoring and Safety Warning System

To install the continuous welded rail (CWR) on the viaduct, it is necessary to consider the accumulated axial force owing to temperature difference and the additional force of the rail exerted by the track-bridge expansion as a result of temperature difference, the so-called track–bridge interaction. This paper used A-thermal fiber bragg grating (FBG) sensors which do not need the temperature compensation, and electronic sensors as monitoring instruments to detect performance changes in CWR axial force. These optical fiber sensors coupled with the developed track axial force calculation software and monitoring platforms calculate the axial force distribution along the track to be monitored. To better understand the influence of the change in the bridge’s structure expansion and the change in concrete slab strain on track axial forces, sensors are set up at bridge expansion joints (EJs), rail ends, and concrete slab beds. Monitoring results show that optic fiber sensors provide sensitive, clear, and stable signals. They are also durable and appropriate for long-term monitoring, providing a complete track safety warning system.

Calculation of Axial Forces Generated in Restrained Pin Ended Steel Columns Subjected to High Temperatures

Calculation of Axial Forces Generated in Restrained Pin Ended Steel Columns Subjected to High Temperatures