Laboratory for Validation of Rolling-Resistance Models

In this paper, a versatile drum setup for measuring rolling resistance of small wheels is presented. The purpose is to provide a flexible setup for testing of models for rolling resistance under controlled circumstances. To demonstrate this, measurements of rolling resistance with a series of sandpapers of different grit sizes representing surface textures were carried out. The measurements show a clear increase in the rolling-resistance coefficient with increasing surface roughness, rolling speed and load. Numerical calculations in the time domain for a visco-elastic contact model run on equivalent surfaces agree with the trends found experimentally. We conclude that this approach to simplifying the experiment in order to obtain a high degree of control, accuracy and repeatability is useful for validating and testing models for calculating the rolling resistance for a given surface texture.

MODELING OF ROLL CASTING AND ROLLING OF METALS

В данной работе представлены результаты изучения процесса валковой разливки с применением методов физического и математического моделирования. Показано, что стабильность процесса валковой разливки-прокатки металлов зависит от таких технологических параметров, как температура перегрева, скорость разливки и уровень расплава в межвалковом пространстве. Для использованных в процессе исследования сплавов получены зависимости оптимальной скорости разливки-прокатки от толщины полосы, угла мениска металла, радиуса валков и температуры перегрева расплавов.Экспериментальная составляющая данных исследований, выполненная в лабораторных условиях на установке валковой разливки металлов, подтвердила адекватность и высокое качество расчетных режимов разливки для всех изучаемых сплавов. Полученная для описания изучаемых процессов валковой разливки металлов математическая модель показала высокую корреляцию теоретических и экспериментальных данных, что свидетельствует о корректности данной модели. This paper presents the results of studying the roll casting process using physical and mathematical modeling methods. It is shown that the stability of the roll casting-rolling process of metals is provided by such technological parameters as the overheating temperature, the casting speed and the melt level in the inter-roll space. For the alloys used in the study, the dependences of the optimal casting-rolling speed on such technological indicators as the thickness of the strip, the angle of the metal meniscus, the radius of the rolls and the temperature of overheating of the melts were obtained. The experimental component of these studies, performed under laboratory conditions at the roll casting plant of metals, confirmed the adequacy and high quality of the calculated casting modes for all the studied alloys. The mathematical model obtained to describe the studied processes of roll casting of metals showed a high correlation of theoretical and experimental data.

Wheel Speed Effect on Transient Lateral Force and Its Characterization by Ramp-Step Steer Test Method

ABSTRACT The concept “relaxation length” serves as one of several ways to characterize the transient lateral response for a rolling tire. Most test methods developed to identify relaxation length tightly link to Pacejka's single-contact-point linear transient model. Its underlying assumption is that the traveled distance during the transition interval is always a constant regardless of the wheels' linear rolling speed. The current research provides physical data against this strong assumption. The data is acquired through a newly-developed test method named the “ramp-step steer method”. The ramp-step steer method features a nonstop, high rolling speed, and fast-changing slip angle procedure that cannot be fulfilled by the conventional “start-stop-resume” step steer method. Thanks to the high dynamic capability of the equipment in GCAPS Corp., the proposed test method becomes feasible. A novel data postprocessing scheme accompanies the test method as well. The ramp-step steer method is independent of any specific models and replicates the scenario of a rolling tire subjected to a sudden slip angle change from on-vehicle to an indoor environment. The wheel speed effect on the tires' transient lateral response is reflected through a proposed quantity, Ly, which is a more general descriptor and can downscale to relaxation length under specific circumstances. Ly itself does not associate with any model, so the remaining study explains the speed effect through an updated model. The present research aims to provide a better way of characterizing tires' lateral transient behavior and is not an alternative to identify the key parameter “relaxation length” in Pacejka's model. Another contribution of the research is categorizing and separating the hierarchy of various transient tire models.

Research the Effect of Speed Mismatch during Continuous Rolling on the Plasticity Margin

The paper analyzes the influence of tension (dam) on the stress-strain stain and plasticity margin. For the analysis, a model of continuous rolling in three adjacent stands was developed using the Deform 3D software. The adequacy of the model was confirmed by comparing the experimental data from the small-section wire mill 150 and the simulation results. Further, a computational experiment was planned to identify the effect of mismatched of rolling speeds on stress-strain stain. It is shown that for small deviations of rolling speed from the matched mode, there is no significant change in the reserve plasticity along the specific trajectory of the particles movement.

Multiscale Mixed Hydrodynamics in Line Contacts

In the hydrodynamic line contact, there is a very thin layer physically adsorbed to the solid surface. When the surface separation is sufficiently small, the Hertzian contact zone will be completely filled with the boundary layer, while in most of the inlet zone still occurs continuum hydrodynamics, which lies between the mated adsorbed layers. The present paper studies this mixed hydrodynamics by a multiscale analysis. The boundary layer flows are simulated from the flow factor approach model; The intermediate continuum fluid flow is simulated from the continuum fluid model. The flow equations are given respectively for the boundary layers and for the intermediate continuum fluid. The final governing equation has been obtained relating the surface separation to the solid surface speeds and the carried load. The calculation results show that for a high rolling speed the hydrodynamic behavior in the contact agrees with the classical hydrodynamic theory; However for a critically low rolling speed it gives the surface separation greatly higher than that calculated from the classical hydrodynamic theory, showing the significant adsorbed layer effect.

MODELING OF A SYSTEM FOR AUTOMATIC REGULATION OF THE TENSION MODE IN THE ROUGHING GROUP OF STANDS OF A CONTINUOUS SECTION MIL

The subject of the research is automatic control system modeling features for tensioning of stands roughing group, which takes into account changes in the rolling speed at exit of the previous stand and entrance to the next stand. Control systems for high-speed rolling on section mills are the most critical systems, since the trouble-free operation of rolling mill largely depends on their work. Rolling speed control is understood to mean tension regulation in the roughing group of stands and stabilization of the rolling loop in the finishing groups. The influence of such technological factors as uneven heating of blanks, change in the crimping mode in stands, etc. leads to the appearance of tension or back-up forces, deviation of rolled loop from the specified values. Tension rolling, in contrast to loop rolling, is a stable rolling mode. However, (at significant values of tension in the rolled products) such a rolling mode leads to different thicknesses of the finished product. The loop rolling mode is an unstable mode and is impossible without automatic control systems. Both in the tension rolling mode and in the free rolling mode with a loop, it is necessary to study automatic control systems in order to determine the possibilities of compensating for disturbing influences and obtaining rolled products of the given accuracy. Therefore, the main task of the automatic control system is to maintain the rolling mode with the lowest possible tension. To achieve this goal, direct control of the tension of the rolled strip with modern technical means is rather difficult, and the operation of tension control systems is based on indirect methods of measuring it, and the study of the system efficiency is reduced to modeling the process itself. The developed model consists of three stands and two inter-stand spaces, since it takes into account changes in rolling speed at the exit of previous stand and the entrance to the next stand. It is due to this that adequate simulation results are obtained that are close to the real rolling process. Keywords: automation, rolls, stand, inter-stand spacing, modeling, loop tension, rolling mill, roughing group.

Research into the Effect of Speed Mismatch during Continuous Rolling on the Process Parameters

The paper analyzes the influence of tension (dam) on the technological parameters of the rolling process (spreading, force and rolling torque). For the analysis, a model of continuous rolling in three adjacent stands was developed, using the Deform 3D software. The adequacy of the model was confirmed by comparing the experimental data from the small-section wire mill 150 and the simulation results. The error in determining the forming was 0.4%, and in determining the power parameters was 11%. Further, a computational experiment was planned, to identify the effect of mismatched of rolling speeds on technological parameters. According to the results of calculations, graphs of changes in technological parameters were constructed. It is established that, even small deviations of rolling speed from the matched mode lead to significant changes in technological parameters.

FEATURES OF LUBRICANE LAYER CREATING IN A LOCAL CONTACT

The article presents the results of research of the influence of the rolling speed parameter during pure rolling and 20% rolling with slip on the kinetics of formation of the lubricant layer thickness in the central contact zone. The aim of experimental research is establishing the impact of operational parameters of friction pairs - speed rolling (a pure rolling and 20% rolling with slip) the dynamics of the process of forming the lubricant layer thickness in the central contact zone between contacting surfaces experimental «steel ball - glass disc.» Oils of various operational purpose were used in the research work, namely motor oils for gasoline and diesel engines (М8Г2К, М10Г2К), universal motor oil (SAE15w40LUX) and universal motor­gear oils (ЄМТ-8, ЄМТ ПРОТЕК) (I-40). The increase in rolling speed was shifted from 0 to 1.8 m / s; at a volumetric temperature (об'ємній температурі) of oils 20°С; contact stress of 251.5 MPa. The thickness lubricating layer in contact was determined by optical interferometry. According to the results of experimental researches concerning determination of the lubricating action of oils in different composition and operational purpose, it was found that during the period of friction steam kinetics of the formation of the lubricant layer thickness depends on the rolling speed - with the increase of which there is an increase in the lubricant layer thickness in the central contact zone, leading to the establishment of appropriate lubrication modes (from boundary to hydrodynamic). Decisive role kinematic viscosity of the lubricant, which depends on the base of oils and quantitative content of the additives. Based on the experimental data obtained in conditions of the rolling with slip, favorable conditions for reducing the initial rolling speed by setting the maximum lubrication regime when using lubricant which contained surfactants with polar molecules. KEY WORDS: ELASTOHYDRODYNAMIC CHARACTERISTICS, ROLLING SPEED, CLEAN ROLLING, SUSPENSION ROLLING, THICKNESS OF THE LUBRICATION LAYER

Increase in the efficiency of water transport of bulk mineral cargo by the segregation of feedstock at the initial technological stage

The paper gives the analysis of the volume of transportation of bulk mineral cargoes by water transport. It is established that the problem of the use of technological processes for sorting non-metallic building materials and coals transported by water transport is relevant. It is revealed that in the applied beneficiation system of crushed stone it is possible to reduce energy consumption due to the segregation of material into commercial fractions at the crushing stage by combining operations. The developed design of the receiving - segregation hopper is considered which allows classifying the feedstock at the initial technological stage of the production of crushed sandstone. A patented design of a segregation hopper and a technological scheme with its use are described. The volume of material sent to the crushing process is reduced by up to 50% due to the separation of particles of commercial fractions, which helps to reduce the production cost of a unit of the finished product. The principle of operation of the hopper is based on the difference in the rolling speed of particles of various sizes. The influence of the geometrical parameters of the chute and the size of the initial material on the capacity of the hopper is investigated. The influence of the slope angle of the chute and the particle size on the production parameters of the installation is proved. The configuration at which the drain wall achieves the highest throughput is determined.