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.

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.

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.

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.

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.