REFINING THE CALCULATION OF THE CAR TRACTION POWER

Introduction. Traction power of the car is used to determine its traction-speed properties. The purpose of the paper is the calculation refinement of the car traction power.Materials and methods. The authors used the methodology of the refined calculation of the car traction power.Results. The authors carried out the comparative analysis of the refined and traditional methods for calculating traction power. As a result, the authors obtained the refined equation for calculating the traction power, taking into account the elastic modulus, the width of the contact track, the free radius of the wheel, the deflection of the tire and the tangential friction forces in the contact zone. The largest discrepancy between the curve of the vehicle’s traction power calculated by the updated methodology and the curve of the vehicle’s traction power calculated by the traditional method was 26.8%.Discussion and conclusions. The results of the research are useful to specialists of automobile and transport enterprises and masters of universities to compare the traction and speed properties of the various car types.

RESEARCH OF STRENGTH OF CONTACT OF THE PLASTIC PIPE ANDCONCRETE WHEN CALCULATING PLASTIC PIPE CONCRETE STRUCTURES

This article presents numerical studies of the stress-strain state of centrally compressed short plastic-tube-concrete (PTC) cylindrical cores, having experimentally obtained and analyzed the influence of the tangential friction forces at the boundary of the concrete core and plastic shell layers on the stress-strain state of the PTC core under the assumption of elastic work of the core materials and shell. The need for these studies is associated with a lack of theoretical and numerical studies of the influence of tangential friction forces on the stress-strain state of this type of structural elements, including the classical solution with a steel shell. In this regard, mathematical modeling and the creation of engineering methods for calculating the PTC based on the study of the actual joint work of the concrete core and the cylindrical plastic shell has significant scientific potential. The performed calculations demonstrated the relevance with engineering accuracy of using the mathematical model of a short PTC rack for engineering calculations and structural analysis of the structure. It has been established that the use of an analytical model allows us to study the effect of variations in the physical and mechanical characteristics of the materials of the core and shell of the PTC on the parameters of the stress-strain state of the structure and to rationally design the PTC elements in the construction of civil and industrial buildings with reference to the widely used materials market.

A dynamic model to predict the number of pins to transmit load in a cycloidal reducer with assembling clearance

In the ideal design of a cycloidal reducer, the tooth profile of cycloidal gear can make contact with all pin teeth on the pinwheel, wherein half of the pin teeth participate in load transmission. Meanwhile, the output holes on a cycloidal gear can maintain contact with all pins on the output disc and half of the output pins deliver load. However, under the influence of the assembling clearance caused by tooth modification, manufacturing tolerance, or machining error, the numbers of pins that participate in force transmission on both pinwheel and output disc fails to reach half of the total available. The objective of this research is to present a dynamic model to precisely predict the number of pins used to transmit load in a cycloidal reducer with assembling clearance. The methods for contact detection among the transmitting components are given in detail. In modeling of the contacts, both normal contact, and tangential friction, forces are considered. Finally, a typical cycloidal reducer with a single cycloidal gear is modeled and used as an example to analyze the variation of the number of pins that take part in load-bearing work under the influences of assembling clearance and external torque.

Dynamics and locomotion of flexible foils in a frictional environment

Over the past few decades, oscillating flexible foils have been used to study the physics of organismal propulsion in different fluid environments. Here, we extend this work to a study of flexible foils in a frictional environment. When the foil is oscillated by heaving at one end but is not free to locomote, the dynamics change from periodic to non-periodic and chaotic as the heaving amplitude increases or the bending rigidity decreases. For friction coefficients lying in a certain range, the transition passes through a sequence of N -periodic and asymmetric states before reaching chaotic dynamics. Resonant peaks are damped and shifted by friction and large heaving amplitudes, leading to bistable states. When the foil is free to locomote, the horizontal motion smoothes the resonant behaviours. For moderate frictional coefficients, steady but slow locomotion is obtained. For large transverse friction and small tangential friction corresponding to wheeled snake robots, faster locomotion is obtained. Travelling wave motions arise spontaneously, and move with horizontal speeds that scale as transverse friction coefficient to the power 1/4 and input power that scales as the transverse friction coefficient to the power 5/12. These scalings are consistent with a boundary layer form of the solutions near the foil’s leading edge.

Nonlinear Dynamics Response of a Planar Mechanism with Two Driving Links and Prismatic Pair Clearance

The influence of the joint clearance on the dynamic response of a planar mechanism with two driving links and prismatic pair clearance is investigated under variable input speeds of the system. The simulation model was built with a nonlinear impact model. The normal contact force is characterized by Hertz contact theory and an energy dissipation term. A tangential friction force is involved in the simulation model based on Coulomb’s friction law. The simulation results indicate that the largest Lyapunov exponents are dependent on the clearance size and the input speed.

Vortex Stability Analysis Based on Coupling the Rubbing with BTA Boring Bar

For the purpose to analyze the stability of the deep-hole boring, a rubbing disturbance model is proposed. New model introduces an effect of friction dominant. The stability criterion of the system is obtained, by means of describing the tangential friction velocity as the function of the angular frequency and eccentricity. Thus, the center tracks changing with vortex stirred by the rotating bar within the inner and outer cutting fluid environment are analyzed. The results show that the vortex frequency of boring bar tends to increase with rotation speed increasing. The vortex frequency tends to hyperbolic declining with the increasing of the clearance C.