Normal Force and Sag Resistance of Pipe Conveyor

Pipe belt conveyor is a new type of environmentally friendly and efficient bulk conveying equipment.In the design of the roller,the belt and the driving motor of pipe belt conveyor,the sag resistance is a key parameter.Meanwhile,the normal force between the conveyor belt and the roller group is the other important factor need be considered and has a great influence on the sag resistance.This paper analyzes a pipe belt conveyor with a diameter of 150 mm to study the calculation method of normal force.And the relationship between the normal force and the sag resistance is explored.Firstly,the normal force is decomposed into three components related to the forming force of belt,material gravity and belt gravity.So it can be expressed as a linear combination of these three quantities,and the coefficients of each component are obtained based on the dynamic analysis of belt-roller.The results show that the coefficient is mainly affected by the material filling rate,and is almost not affected by the distance between the rollers and the density of the material.The calculation method of the normal force is eventually obtained.Secondly,the normal force in the case of different material filling rates is tested by experiments,and the calculation method of the normal force is verified.Thirdly,the variation law of the sag resistance in the case of different roller group spacing and material filling rate is studied by the dynamic model.It is found that the roller group spacing and material filling rate affects the sag resistance by changing the normal force.There is a power function relationship between the sag resistance and the normal force.In the case of different roller group spacing and material filling rate,the relationship among the sag resistance and the normal force remains unchanged.This study results are of great significance to the design of pipe belt conveyor.

A Study of Effect of Various Normal Force Loading Forms on Frictional Stick-Slip Vibration

In this work,a comparative study is performed to investigate the influence of time-varying normal forces on the friction properties and friction-induced stick-slip vibration(FIV)by experimental and theoretical methods.In the experiments,constant and harmonic-varying normal forces are applied,respectively.The measured vibration signals under two loading forms are compared in both time and frequency domains.In addition,mathematical tools such as phase space reconstruction and Fourier spectra are used to reveal the science behind the complicated dynamic behavior.It can be found that the friction system shows steady stick-slip vibration,and the main frequency does not vary with the magnitude of the constant normal force,but the size of limit cycle increases with the magnitude of the constant normal force.In contrast,the friction system under the harmonic normal force shows complicated behavior,for example,higher-frequency larger-amplitude vibration occurs and looks chaotic as the frequency of the normal force increases.The interesting findings offer a new way for controlling FIV in engineering applications.

Effect of Normal Force on Fretting Wear Behavior of Zirconium Alloy Tube in Simulated Primary Water of PWR

The effect of normal force on fretting wear behavior of zirconium alloy tube mated with grid dimple in simulated primary water of pressurized water reactor nuclear power plant was investigated.Results showed that the maximum wear depth,wear volume and wear coefficient of Zr alloy tube in simulated primary water at 315℃ gradually increased with increasing normal force,while the friction coefficient gradually decreased.Fretting process could be divided into four stages according to the variation of friction coefficient during test.When normal force exceeds 30 N,the fretting regime would transition from gross slip regime to partial slip regime after 3×10^(7 )cycles.Delamination was aggravated with increasing normal force,while abrasive wear became slighter.A thicker third-body layer with monoclinic ZrO_(2) was formed by the tribo-sintering mechanism under higher normal force.In addition,the schematic evolution processes of delamination and third-body layer formation were displayed according to morphology observation.

Investigation into Improvement for Anti-Rollover Propensity of SUV

Currently, many research from domestic and foreign on improving anti-rollover performance of vehicle mainly focus on the electronic control of auxiliary equip- ment, do not make full use of suspension layout to optimize anti-rollover performance of vehicle. This investigation into anti-rollover propensity improvement concentrates on the vehicle parameters greatly influencing on anti-rollover propensity of vehicle. A simulation based on fishhook procedure is used to perform design trials and evaluations aimed at ensuring an optimal balance between vehicle＇s design parameters and various engineering capacities, the anti-rollover propensity is optimized at the detailed design stage of a new SUV model. Firstly a four-DOF theoretical kinematic model is established, then a complete multi-body dynamics model built in ADAMS/car based on the whole vehicle parameters is correlated to the objective handing and stability test results of a mule car. Secondly, in fish- hook test simulations, the Design of Experiments method is used to quantify the effect of the vehicle parameters on the anti-rollover performance. By means of the simulation, the roll center height of front suspension should be more than 30 mm, that of rear suspension less than 150 mm, and the HCG less than 620 mm for the SUV. The ratio of front to rear suspension roll stiffness should be ranged from 1.4 to1.6 for the SUV. As a result, at the detailed design stage of product, the anti-rollover performance of vehicle can be improved by optimizing chassis and integrated vehicle parameters.

Determination of the Friction Coefficient in the Flat Strip Drawing Test

Current work is focused on the influence of friction in deep drawing process. Friction measurements were also conducted using a modified tribotester based on strip sliding between tools. Four different tool surfaces were tested under similar contact conditions regarding contact area, normal pressure, sliding speed, lubricant and surface characteristics to calculate the friction coefficient between the tool surface and a high strength low alloy steel sheet HSLA 380. The results showed that friction coefficient varies over a wide range with different lubricating conditions and different sliding velocities. For some sliding velocities, the coefficient of friction is stable and low, while for others it is unstable and higher. Results of the experiments reveal that this novel tribotester is a very useful tool to evaluate and compare the friction between steel sheet and tool surfaces in alloyed steel for cold working applications. The outcomes have only small dispersion within the different test series, which indicates a stable process with good repeatability. The test method enables comparison of different surface finishes and treatments, lubricants and coatings in terms of friction and galling under conditions similar to those found in sheet metal forming processes. The four different types of surfaces considered for this study were grinded, polished, nitrided and quenched/tempered. The main difference among the tested tools in this work was the surface roughness, which was found to have a strong influence on friction.

SQUEEZE FLOW OF A SECOND-ORDER FLUID BETWEEN TWO PARALLEL DISKS OR TWO SPHERES

The normal viscous force of squeeze flow between two arbitrary rigid spheres with an interstitial second-order fluid was studied for modeling wet granular materials using the discrete element method. Based on the Reynolds' lubrication theory, the small parameter method was introduced to approximately analyze velocity field and stress distribution between the two disks. Then a similar procedure was carried out for analyzing the normal interaction between two nearly touching, arbitrary rigid spheres to obtain the pressure distribution and the resulting squeeze force. It has been proved that the solutions can be reduced to the case of a Newtonian fluid when the non-Newtonian terms are neglected.

Effects of antiseizure medications on alternative psychosis and strategies for their application

Forced normalization(FN)is a unique phenomenon that is often seen in the treatment of epilepsy.FN is characterized by abnormal mental behavior and disordered emotions in epilepsy patients despite a significantly improved electroencephalogram and successful seizure control;the occurrence of FN seriously affects patients’quality of life.The causes of FN include antiseizure medications(ASMs),epilepsy surgery and vagus nerve stimulation,with ASMs being the most common cause.However,with the timely reduction or discontinuation of ASMs and the use of antipsychotic drugs,the overall prognosis is good.Here,we perform an extensive review of the literature pertaining to FN,including its epidemiology,possible mechanisms,clinical features,treatment and prognosis.

The establishment of the normal contact force model for a one‐dimensional sphere chain subjected to impact load

The normal contact force determines the behavior of a particle system.To investigate the normal contact force in a one‐dimensional sphere chain subjected to impact load,by comparing the simulation results of the existing typical normal contact force models embedded in the discrete element program,an improved normal contact force model was proposed in this paper.The improved model con-sists of two parts:the Cundall model for loading and the Daniel model for unloading.Moreover,a systematic test was designed to verify the accuracy and applicability of the improved model.The results showed that the calculated contact force curves agree well with the experimental results.Furthermore,the improved model is implemented in the solution algorithm without need for complex numerical methods and parameters fitting,leading to more efficient simulations.

Ab initio study of vibrational frequencies, force field and normal coordinate analysis of the cis- and trans-isomers of nitrosomethanol

In this paper, the equilibrium geometries of two isomers of the newly found compound ——nitrosomethanol——have been optimized by ab initio SCF MO method with 3-21G basic set by gradient technique. And the second derivatives of potential energy (i. e. the force constant matrix elements) have been calculated analytically. Hence the entire force fields of the two isomers of nitro- somethanol have been obtained theoretically. The theoretical vibrational frequencies and the corres- ponding normal modes were obtained and compared with the experimental values. and the structures of two isomeric forms of nitrosomethanol are established.

Research of Interaction Force Coefficients Based on Model Test in Loading Condition

It is very difficult,for the component-type ship mathematical model,to estimate the interaction force coefficients among the hull,propeller and rudder. Some coefficients such as wake fraction and flow straightening coefficient were studied from the model tests in diffierent loading conditions and the normal force of rudder was tested in captive model tests to obtain the coefficients. From these results of the tests,the flow straightening coefficients increase with the increase of trims or drafts. Similarly,wake fraction coefficients are larger for the large drafts,however,become small as the trims increase. The resistance is obviously different in fully loaded condition with the trims by stern,however ,the difference is not evident when the draft decreases and the bulbous bow is above the water surface.

Hypersonic starting flow at high angle of attack

Compressible starting flow at small angle of attack （AoA） involves small amplitude waves and time-dependent lift coefficient and has been extensively studied before. In this paper we consider hypersonic starting flow of a two-dimensional flat wing or airfoil at large angle of attack involving strong shock waves. The flow field in some typical regions near the wing is solved analytically. Simple expressions of time-dependent lift evolutions at the initial and final stages are given. Numerical simulations by compuational fluid dynamics are used to verify and complement the theoretical results. It is shown that below the wing there is a straight oblique shock （OSW） wave, a curved shock wave （CSW） and an unsteady horizontal shock wave （USW）, and the latter moves perpendicularlly to the wing. The length of these three parts of waves changes with time. The pres- sure above OSW is larger than that above USW, while across CSW there is a significant drop of the pressure, making the force nearly constant during the initial period of time. When, however, the Mach number is very large, the force coefficient tends to a time-independent constant, proportional to the square of the sine of the angle of attack.

Thrust ripple optimization and experiment for a permanent magnet linear synchronous motor

Thrust ripple such as end force,slot force and normal force are key factors that affect the properties of permanent magnet linear synchronous motors(PMLSM).According to different mechanics and analytical models,end force resulting from open magnetic circuit of PMLSM was greatly decreased by optimizing the length of the PMLSM mover.Slot force caused by slot effect was greatly reduced by using fraction slot structure,and normal force was calculated through the finite element method(FEM).After thrust ripple was calculated,its uniform formula was obtained through Fourier series nonlinear regression.An experimental system was set up to measure thrust ripple,and experiment results demonstrated that experimental force ripple was quite in line with that calculated by the fit-ting formula.The optimal theory and analysis method is ef-fective,and the obtained formula can be utilized to com-pensate thrust ripple in practical applications and improve the motion performance of PMLSM.

Research on Vane End Face of Cam-Rotor Vane Servo Motor Based on Disturbing Torque

Cam-rotor vane motor(CRVM) is one of the new continuous hydraulic servo motors with the characteristics of no pulsation of instantaneous flow rate and output torque,small volume and rotating inertia.It is one of the appropriate actuators for hydraulic servo system which has good dynamic and steady-state performance requirements.The ideal output torque of CRVM is pulseless,but the actual output torque of CRVM is pulsating.This is caused by the disturbing torque of contact components,especially the friction between vane and cam-rotor.In order to get better performance of CRVM,which means more stable output torque and smaller disturbing torque,we discuss four kinds of vane end faces(VEFs).Analytic formulae of the normal contact force and the disturbing torque caused by the vane are derived from systematical force analysis.The normal contact force and the disturbing torque vary through a period under different VEF,and the reduced oil pressure is simulated in this paper.The simulation shows that the VEF with the proper round and reduced oil pressure can significantly decrease the disturbing torque and get better servo performance.The experiment results verify the correctness of the theoretical analysis and simulation.