Features of an elastic wheel motion along a curvilinear and rectilinear trajectory with a slip

The results of the study of the motion of an elastic wheel as an integral mechanism along a curvilinear and a rectilinear trajectory with a slip on the ground plane having a high adhesion coefficient are presented. The previous researches analysis has shown that the most complete theory of wheel skidless rolling without slipping on elastic pneumatics was formulated by Keldysh V. M. who proposed the equation for calculating the curvature of the motion trajectory. Due to the difficulty of this equation coefficients determining, its use is currently limited. In this paper, the dependences for determining the components of the equation of the elastic wheel motion trajectory curvature have been proposed. According to the shimmy theory, during an elastic wheel rolling along a curvilinear trajectory, the rim turn and its lateral displacement relative to the tire-ground contact patch occur simultaneously. The rim turn causes tire body torsion, and the lateral displacement causes the elastic wheel moving with a slip angle. It is established that the absolute value of the tire body torsion angle is equal to the slip angle, and their values depend on the trajectory curvature, on the tire-ground contact patch longitudinal axis, and on the existence of traction there. The condition, under which the tire body energy distribution on the rim relative rotation and on its lateral displacement during the movement along a curved trajectory is uniform, has been determined. The experimental confirmation of the hypothesis of uniform distribution of the energy supplied to the elastic wheel during its movement along a curvilinear trajectory on the rim relative turning and its lateral displacement has been obtained. When the elastic wheel moves along a rectilinear trajectory with a slip, only the rim lateral displacement occurs, this displacement is accompanied by a cornering force applied in the center of the tire-ground contact patch and by the tire alining torque relative to the vertical axis passing through the contact patch geometric center. The energy consumption for the rim lateral displacement during the wheel rolling along a rectilinear trajectory with a slip has been also determined. The results of the research can be useful to professionals improving the wheeled vehicles performance characteristics, including maneuverability, handling, and road stability.

On the Issue of Determining Relative Rail Rolling Contact Fatigue Damageability

Adoption of heavy haul traffic on many railroads, comprising Russian railways, has highlighted the relevance of assessing the effect of increased axial loads on the contact fatigue life of rails.The article describes a set of theoretical studies carried out to create a scientifically substantiated method for predicting the contact fatigue life of rails depending on the values of axial loads. The stress-strain state of the contact area has been determined using the finite element model of wheel rolling on a rail. It has been found that the wheel-rail rolling contact area undergoes complex multiaxial loading with the simultaneous action of normal and shear strains. Based on the analysis of models describing multiaxial fatigue damage, the Brown–Miller model was chosen, which considers the simultaneous action of normal strains at the contact area and of maximum shear strains, which most fully describes the stress-strain state of the wheel-rail rolling contact area. To apply the Brown–Miller model, fatigue stress-strain curves for rail steel have been identified. Based on the analysis of methods for determining the parameters of stress-strain curves carried out by V. A. Troschenko, a modified Roessle– Fatemi hardness method has been applied. Based on the experimentally determined values of hardness on the rolling surface, the parameters of the curves of elastic and plastic fatigue have been revealed by calculation and experiment. To establish the damaging effect of the load from wheel rolling on a rail, the concept of relative damage per rolling cycle had been assumed which is the value inverse to the number of cycles preceding formation of a contact-fatigue crack at a given value of the axial load.Calculations of the relative damage rate of the rolling surface of rails caused by contact fatigue defects were carried out with the Fatigue software package considering mean values of the indicators of the degree of fatigue strength and plasticity of rail steel and the calculated stresses in the wheel-rail contact area, as well as the plasticity correction using Neuber method. The polynomial dependence of relative damageability of the rolling surface of rails is obtained. The established functional dependence of relative damageability of the rolling surface of rails on the values of vertical forces can be used as the basis for the developed methodology for predicting the contact fatigue life of rails.

Maximum Admissible Slip of Tractor Wheels without Disturbing the Soil Structure

One of the most important parameters that characterize the traction-coupling properties of a wheeled tractor is its slip. The more tractor’s gross traction exists, the higher its traction-coupling properties are. However, this gross traction should not exceed its maximum possible value, which, in turn out, is to be determined by the maximum permissible slip, . This article provides the equation to calculate this crucial parameter and establishes the dependencies between the tractor’s slip and soil structure coefficient. It was shown that the value of basically depends on such soil characteristics as the bulk deformation coefficient and the coefficient of rolling resistance. Calculations showed that, for the average value of the soil bulk deformation coefficient at , the average value of rolling resistance coefficient at 0.16, and the ratio value of the maximum permissible soil pressure to the tractor wheel rolling radius at , the maximum permitted amount slip of the tractor wheels should not exceed 15%. With more slip, the soil structure deteriorates significantly. In this case, its structure coefficient may be less than critical, equal to 0.4.

Investigation of the Influence of Permanent Traffic Lane Properties on Rolling of Bridge Agricultural Equipment Wheels

Movement of bridge agricultural equipment along the permanent traffic lanes is characterised by significant energy costs for overcoming the rolling resistance forces. Until now, the movement process of bridge agricultural equipment wheels along the compacted soil of permanent traffic lanes has been paid only a little attention. It has been established that the physical and mechanical properties of soil lanes significantly affect the energy consumption necessary for overcoming the rolling resistance of forces of bridge agricultural equipment wheels. Considering the range of possible changes in these properties, the coefficient of rolling resistance of equipment wheels varies from 0.06 to 0.1, which is 66%. In order to reduce the rolling resistance coefficient of equipment wheels when moving along the permanent traffic lanes, the surface needs to be undeformable. When moving along such a solid and dense supporting surface, the wheel rolling resistance is lowest.

Buspirone, a 5-HT1A agonist attenuates anger, aggression and suicidal tendencies in rats.

The purpose of the work was to evaluate the effect of buspirone (BUS) on social isolation induced anger, aggression and suicidal tendencies in rats. The male Wistar rats were randomized in 6 groups (n = 6) and caged individually for 14 days to elicit anger and aggression. They were then divided into the following groups vehicle control (no isolation), Stress control (SC), fluoxetine (Flx; 30 mg/kg, p.o), BUS (10 mg/kg, p.o), BUS (20 mg/kg, p.o), BUS (40 mg/kg, p.o). All treatments were administered from day 14 through day 28. On the last day of treatment, assessment of anger, aggression and suicide-related traits were performed. Serum cortisol, blood pressure were measured and magnetic resonance imaging (MRI) of the rat's brain and of BDNF expression were performed. SC group showed significant increase in anger (wheel rolling activity), aggression (increased number of attack bites, wrestling, chasing behavior), irritability score, learned helplessness (number of attempts of escape success and failure, escape latency), increased level of serum cortisol as compared to normal confirming induction of anger, aggression and suicidal ideation. BUS significantly reduced all behavioral traits associated with anger, aggression and suicidal ideation, reduced cortisol levels and significantly increased BDNF compared to stress control. Blood pressure increased substantially in stress control was significantly reduced by BUS, but not by Flx. Neuroimaging studies in stress control brains showed a reduction in amygdala size compared to normal, while animals under BUS treatment mitigated this reduction. Buspirone has been found to be effective in preventing anger, aggression and suicidal tendencies.

Use of the kinematic radius in the rolling mechanics of an elastic wheel

The analysis of the physical essence of the kinematic and dynamic radii of the wheel is given. It is stated that the rolling radius of the wheel is a conditional kinematic parameter that characterizes only the rolling mode of the wheel. It is not the shoulder of all longitudinal forces acting on the wheel and should not be used to determine tractive forces, rolling resistance and wheel braking forces. Specific examples are given to illustrate the inappropriateness of using the kinematic radius to determine forces and moments. Keywords: elastic wheel, rolling radius, kinematic radius, dynamic radius, arm of force, traction force, rolling resistance force, braking force, rolling mode

Using the kinematic radius in the mechanics of elastic wheel rolling

As you know, in the mechanics of a wheel with an elastic tire, both dynamic (rd) and kinematic (rk) radius are widely used. At the same time, specialists in the theory of the motion of wheeled vehicles still do not have a clear understanding of the scope of their application. Keywords: elastic wheel, kinematic radius, circumferential force, dynamic radius, wheel traction force, instantaneous center of speeds, torque, solid, rolling resistance

Control and measuring modernization systems of the “Soil Channel” stand and the development of a wheel motion mathematical model in stand conditions

Introduction (problem statement and relevance). A promising direction for reducing a vehicle moving energy is the application of adaptive laws for controlling the power supplied to the propeller based on neural networks. To create a training array of the latter, a large set of experimental data is required, the collection of which, as a rule, is carried out by using research stands, such as the “Soil Channel”. But the fi eld studies require a lot of resources.The purpose of the study was to create a wheel rolling mathematical model in the conditions of the stand, with the help of which it would be possible to organize the collection of needed statistical data on the wheel rolling modes by calculation them in an automatic mode.Methodology and research methods. The paper describes the “Soil Channel” bench test, held by the Department of “Multipurpose tracked vehicles and mobile robots” of Bauman Moscow State Technical University. A list of the control and measuring systems components used in the process of its modernization in order to automate the collection of experimental data was considered. The “Soil Channel” stand mathematical model was presented which was based on the use of experimentally obtained dependences of the specifi c longitudinal thrust force on sliding and the specifi c longitudinal thrust force on the specifi c circumferential force.Scientifi c novelty and results. The developed mathematical model has been verifi ed on the basis of the data obtained in the course of fi eld studies. Conclusions were made about the suitability of the developed mathematical model of wheel motion under the stand conditions for conducting virtual experiments.Practical signifi cance. The data obtained by applying the developed mathematical model can be used to create a training array of a neural network to provide the implementation of adaptive laws for controlling the power supplied to the propeller.