Pair Of Rolls Research Articles

Eddies driven by eddy currents: Magnetokinetic flow in a conducting drop due to an oscillating magnetic field

An oscillating magnetic field of amplitude H 0 and angular frequency ω is applied across an electrically conducting non-magnetic drop of conductivity κ, viscosity η and radius R. The oscillating magnetic field generates an oscillating electric field due to Faraday's law, , where E and H are the electric and magnetic field, and μ 0 is the magnetic permeability. This generates a current density, . The non-linear interaction between the oscillating current and magnetic field results in a time-independent body force density, due to Ampere's circuital law. This drives a pair of axisymmetric circulation rolls in the two hemispheres of the drop in the viscous limit where inertia is neglected. The characteristic circulation velocity is times a function of the dimensionless parameter , the square root of the ratio of the magnetic field frequency and the eddy current relaxation rate. The velocity increases proportional to for , has a maximum at , and decreases proportional to for . Large strain rates in the range are generated in a metal drop of radius 0.1–1 mm for magnetic flux density as low as , provided relatively high frequencies of oscillation in the range are used. Joule heating could increase the drop temperature by tens of degrees Kelvin in comparison to the ambient.

Study on the shape prediction of doubly curved shallow shell in flexible rolling process

Flexible rolling (FR) is a novel process for manufacturing doubly curved shallow shells with various shapes based on a pair of small-diameter bendable rolls. In this paper, the fundamental reason for bi-directional bending of the sheet metal in FR is explained. For the purpose of predicting the forming radii in the transverse and longitudinal directions more effectively, the exit velocity is divided into linear velocity and interference velocity, with the latter so small as to be considered to cause only elastic deformation of the sheet. The theoretical calculation model of the pre-curvature radius resulted from linear velocity is established. Using the mechanical theory of the doubly curved shallow shell, the transverse and longitudinal curvature changes caused by the interference velocity are derived and solved by the analytical approach, which are added to the transverse and longitudinal pre-curvatures respectively so that the actual curvature radii are obtained. In order to verify the reliability of the proposed shape prediction method of FR, numerical simulations and forming experiments for convex and saddle-shaped parts are carried out. Through measurement and comparison, it is found that the simulated and experimental results are extremely consistent with the theoretical data. Besides, the effect of important parameters on elastic deformation is investigated by means of the deduced formulas.

Rolling pairs with shifting contact geometry: Design, development, and validation

This work introduces two innovative rolling pair concepts to minimize slippage and reduce mass in cam-roller systems of large-scale hydraulic drivetrains: The variable contact length and the Shifting Contact Geometry concepts. Both aim to improve traction in the low contact force phase in cyclically loaded rolling contacts. The shifting contact geometry concept was validated using three custom rolling contacts: a line contact, a double elliptical contact, and a combination of both (i.e., shifting contact geometry). The tests were conducted under synchronized cyclic loading to mimic the conditions in a hydraulic drivetrain. Furthermore, a model from previous work was implemented to make predictions and compare them against the experimental results. During preliminary tests, the double elliptical contact displayed superior tractive behavior than the line contact under the same load thanks to higher contact pressures. Under synchronized cyclic loading, the line contact displayed high sensitivity to applied resisting torques at low contact forces, leading to high slide-to-roll ratios and traction force peaks. In contrast, the rolling pair with shifting contact geometry exhibited minimum slippage even under high resisting torques, resulting in substantially lower (and in most cases negligible) slide-to-roll ratio and traction force peaks. The simulations also captured this behavior, proving the validity of the model for predicting and comparing the rolling-sliding dynamics of these two different rolling pairs. This study demonstrates that rolling pairs with shifting contact geometry can not only improve the tribological performance of cam-roller contacts in large-scale hydraulic drivetrains but also yield a more favorable dynamic behavior.

Теоретическое исследование кинематических пар «тор с тором» на основе геометрической кинематики

The article presents a theoretical study of kinematic pairs known as «rolling pairs» used in many areas of mechanical engineering, in particular, mechanisms. The research concerns such bodies (links) as geometric tori, which are well-known bodies of rotation. From the geometric kinematics, new representations of the mechanical motions of a torus in a «torus-torus» connection are described without the reasons that cause this motion. Two options for connecting two tori are analyzed: the axes of the tori are parallel and perpendicular. By analogy, the analysis of kinematic pairs of this type expands the elements of kinematic pairs theory and allows developing their new variants in many mechanisms used in various fields of mechanical engineering.

Physicochemical, rheological, and baking properties of wheat flours from different mill streams

AbstractBackground and ObjectiveWheat is one of the most produced cereal grains in the world, predominantly consumed as bread and other baked products. The roller mill system, which produces different stream flours, is the most commonly used size reduction method for wheat. This study aims to comprehensively examine the physicochemical properties, rheological behavior, and bread‐baking performances of individual mill streams. Flours from 15 different mill streams, along with straight‐grade flour, were collected from a pilot‐scale flour mill and thoroughly analyzed.FindingsThe results showed that the protein and ash content of the flours increased as they passed from the first to last pairs of rolls, while the moisture content decreased. All the flours collected showed poor bulk flowing properties. Rheology analysis revealed that flours from the break system had better mixing properties compared to that from the reduction system, and this trend was also observed in bread‐baking quality. Rheological properties of 4M (4th middling's) and 5M (5th middling's) flours were extremely poor, comparable to gluten‐free flour characteristics. The bread loaves produced by 3BK (3rd break) and 4BK (4th break) showed larger volumes, while 4M and 5M yielded poor‐quality bread. Principal component analysis indicated that lactic acid ‐SDS‐retention capacity can serve as a better predictor of the baking property of wheat flour compared to current methods.ConclusionOur study shows that different flour streams have significantly different dough properties and baking application functionalities. Appropriate flour streams may be pooled for specific end‐uses (e.g., pizza, bread, noodles, pretzels, and cookies).Significance and NoveltyThis study highlights the significance of better understanding wheat flour characteristics for enhancing the overall baking quality, specific end uses, and consumer satisfaction. This study will serve as a blueprint to improve wheat flour testing for baking purposes.

Lifetimes of metastable windy states in two-dimensional Rayleigh–Bénard convection with stress-free boundaries

Two-dimensional horizontally periodic Rayleigh–Bénard convection between stress-free boundaries displays two distinct types of states, depending on the initial conditions. Roll states are composed of pairs of counter-rotating convection rolls. Windy states are dominated by strong horizontal wind (also called zonal flow) that is vertically sheared, precludes convection rolls and suppresses heat transport. Windy states occur only when the Rayleigh number $Ra$ is sufficiently above the onset of convection. At intermediate $Ra$ values, windy states can be induced by suitable initial conditions, but they undergo a transition to roll states after finite lifetimes. At larger $Ra$ values, where windy states have been observed for the full duration of simulations, it is unknown whether they represent chaotic attractors or only metastable states that would eventually undergo a transition to roll states. We study this question using direct numerical simulations of a fluid with a Prandtl number of 10 in a layer whose horizontal period is eight times its height. At each of seven $Ra$ values between $9\times 10^6$ and $2.25\times 10^7$ we have carried out 200 or more simulations, all from initial conditions leading to windy convection with finite lifetimes. The lifetime statistics at each $Ra$ indicate a memoryless process with survival probability decreasing exponentially in time. The mean lifetimes grow with $Ra$ approximately as $Ra^4$ . This analysis provides no $Ra$ value at which windy convection becomes stable; it might remain metastable at larger $Ra$ with extremely long lifetimes.

MECHANICAL ANISOTROPY OF COLD-ROLLED ST-37 STEEL PLATE UNDER HIGH STRAIN RATES LOADINGS

Cold rolling process in metal could increase its strength and hardness, but also induces mechanical anisotropy. This is caused by unresolved plastic strain and microstructural changes caused by plastic deformation exerted by pair of rolls at a relatively low temperature. This research aims to provide understandings on anisotropic and strain rate sensitive behaviour of St-37 mild steel. The microstructure of rolled and unrolled St-37 plate were observed in 3 directions relative to the rolling direction. The cylindrical specimens were then prepared from rolled plate with 33.3% reduction in the orientation of 0o, 45o, and 90o relative to the rolling direction. Specimens were also prepared from unrolled plate as comparison in the same directions. These specimens were then tested in compression loading, first in quasi-static condition, and then by using Split-Hopkinson Pressure Bar (SHPB) at the strain rate of 1200 s-1. The experimental results in the form of stress-strain curves are used to obtain the parameters of Simplified Johnson-Cook viscoplastic model. The anisotropy of yield strength in rolled specimens could be seen on both quasi-static and high strain rate condition, where the highest strength found on the specimens perpendicular to the rolling direction. In addition, the effect of cold rolling to the strain rate sensitivity of the material were also captured successfully in this study, where specimens from rolled plate show less strain rate sensitivity compared to the unrolled specimens.

Анализ кинематических пар катания типа «цилиндр в цилиндре»

The article is devoted to the study of specific kinematic pairs used in many areas of mechanical engineering: the so-called «rolling pairs» used in many mechanisms. The study is based on a detailed study of the structure of the «cylinder in cylinder» connection, and their geometric parameters are considered. The analysis is considered by the location of the axes of the cylinders between themselves: when the axes are parallel and when they intersect or intersect at an angle of 90 º. This study complements the data in the theory of description of kinematic pairs, in particular, rolling pairs, and makes it possible to synthesize their new types for their rational use in the mechanisms of many industries.

Pattern selection and heat transfer in the Rayleigh–Bénard convection near the vicinity of the convection onset with viscoelastic fluids

The effect of viscoelasticity on the flow and heat transport in the Rayleigh–Bénard convection (RBC), a frequently encountered phenomenon in nature and industry, in a rectangular enclosure with horizontal periodic boundary is investigated via direct numerical simulation. The working fluid is described by a finitely extensible nonlinear elastic-Peterlin constitutive model almost all important features of viscoelastic fluid flow. Numerical simulations are conducted at a low concentration β=0.9, where β=μs/μ0, μs is the solvent viscosity, and μ0=μs+μp is the sum of μs and the polymer viscosity μp. A parametric analysis is performed to understand the influence of the Weissenberg number Wi, the viscosity ratio β, and the extension length L on the oscillating mode of the viscoelastic RBC. The results indicate that both Wi and β weakly inhibit the convection onset and the transition from steady to oscillatory convection. The amplitude and frequency of the oscillations in the oscillatory flow regime are both suppressed. However, the strongly elastic nonlinearity makes the flow transition irregular and even brings about the relaminarization or lead to the convection cells traveling in the horizontal direction. The increasing extension length L induces multiple pairs of roll flow patterns at a specific setting of (Ra, Wi). Heat transport is reduced (up to 8.5%) by elasticity but still obeys the power law with Ra if the flow pattern has one pair of rolls. However, heat transfer enhancement occurs if multiple pairs of rolls are induced.

Three-dimensional analysis of the stress-strain state for straightening pipes on skew-roll straightening machines with special roll profiling

In order to increase the competitiveness of domestic metal products, in particular pipes, it is necessary to ensure their compliance with international standards in terms of the main quality indicators. The pipe straightening process provides quality indicators such as straightness and cross-sectional shape. Skew-roll pipe straightening machines are the most common and most effective for straightening pipes of small and medium diameters. The most modern are six-roll pipe straightening machines with special roll profiling, which provide straightening of two types: in the caliber of the profiled rolls and at the step between the roll clamps. But the lack of knowledge about the regularities of straightening pipes holds back the wide implementation of such machines. In the work, a finite element model was developed and with its use, a study of the influence of the straightening process parameters in profiled rolls with symmetric and asymmetric profiling of the extreme pairs of rolls on the indicators of pipe straightness and straightening force was carried out. According to the results of their implementation, it was established that straightening the pipe in gauge and pitch allows to reduce the residual curvature of the pipe by almost three times with a 2.5 times smaller overlapping of the middle rolls relative to the outer ones. At the same time, the force on the most heavily loaded middle rolls increases almost twice, which should be taken into account in view of the possibility of ovality in the section of thin-walled pipes. The use of additional asymmetric profiling of the extreme rolls with step adjustment practically does not affect the quality of straightening in the gauge, increases the quality of straightening at the step by up to 15 %, while reducing the maximum straightening force by 5—7 %. The developed finite-element model allows determining the rational values of rolls overlaps to ensure the minimum residual curvature of the pipes.

Study on the conditions of material capture by pairs of rolls of squeezing machines

This paper is devoted to the analysis of the condition for material capture with pairs of rolls of squeezing machines. Calculation formulas for the parameters of roll pairs of squeezing machines are given, such as: contact angles, minimum distance between the rolls, the thickness of the processed material after squeezing. It has been established that the capture of material in the roll pairs of squeezing machines is determined by the center distance between the rolls, the thickness of the processed material and the coefficients of friction of the rolls on the processed material. It was determined that the displacement of the upper roll relative to the lower roll does not affect the values the nip angles.

Study on issues of hydrodynamics of the roll squeezing process

The laws of distribution of hydrodynamic pressure and changes in extracted fluid in the pressing area are developed; they take into account the phenomena of contact interaction in the roll pair of the pressing machine. Hydraulic pressure in the compression zone increases from zero at the initial point of contact to a maximum value at a point lying on the line of centers. The distribution of hydraulic pressure in the recovery zone depends on the position of the water division point. It was revealed that the pattern of change of the removed fluid in the recovery zone depends on the position of the water division point. At the beginning of the recovery zone and up to the point of water division, the fluid flows from the coating into the material, and beyond this point, fluid is reabsorbed from the roll coating, and the amount of fluid removed from the material in the recovery zone is greater than the amount of absorbed fluid.

Parameters of contact lines of rolls

The article defines the parameters of the contact lines of the rolls. Calculation formulas are found for determining such parameters as the ratio of strain rates in roll pairs when the deformation of the semi-finished leather product and the coating of are given by rheological models. It was revealed that the forms of contact lines in roll pairs do not depend on the methods of specifying the deformation of the leather material and the coating of the rolls.

Considerations concerning the power loss in a gear system

The goal of the research is to assess the power losses in a gearbox with helical gears. In addition, the effects of each component of the total power loss in a gear transmission system are investigated. The study shows the important influence of the gear meshing power loss and discuss some aspects concerning the calculus formula. Also, the coefficient of friction is computed and the efficiency of the gear meshing system and the bearing rolling pair. Results are compared to a numerical results obtained by other researchers.

Power conditions of rolling in universal calibers of modern rail-beam mills

Development of rolling stock, increase in the speed of transportation, load-bearing capacity of highways and their length requires constant improvement of the production technology for railway rails. Modern rail-beam mills have in their composition a continuously reversible group of stands, which includes universal stands. Rolling of rail profiles in universal calibers is radically different from rolling in two-roll calibers, and at the moment is not well studied, both theoretically and practically. The article defines the conditions for feasibility of the rolling process in universal calibers with a pair of non-drive rolls, taking into account the values of active (reserve friction forces) acting from the drive rolls and reactive forces from the non-drive rolls and roller fittings. The energy balance method solves the problem of determining the back-up force required for deformation in non-drive rolls. When solving the equation of equilibrium of forces in the deformation center formed by the drive rolls, the reserve of friction forces is defined, the magnitude of which largely determines the possibility of the rolling process. Theoretical dependences are obtained for estimating the power balance during rolling in universal calibers of modern rail-beam mills, taking into account the reserve of friction forces provided by the drive rolls and the support required for deformation in non-drive rolls. Information about the force conditions in a universal caliber is necessary to analyze the feasibility of the rolling process in it under various deformation modes and to clarify the drawing coefficients for elements of the resulting profile. Dependencies are proposed that allow estimating the consumption of the reserve of friction forces for the operation of roller fittings serviced by universal caliber. The well-known formula of A.I. Tselikov and A. I. Grishkov on the definition of broadening was clarified in relation to rolling in universal calibers with two non-drive rolls. The support from the non-drive rolls side effects the change in size of sole and head of the rail profiles.

Controllability and stability capacity of a roll pair motion research

The process of deriving the equation of the perturbed motion of a roll pair during the processing of leather material is discussed in the article, taking into account the influence of dynamic factors. It is shown that one of the reasons for the unstable stress state on the contact surfaces in the roller mechanism are dynamic factors arising from inaccuracies in the manufacture of its individual parts, assembly defects, and the occurrence of an oscillatory process in the roller mechanism, as well as due to the non-uniform thickness of the processed material at its gripping during starting and stopping the machine. Methods for determining optimal controls are shown; they provide asymptotic stability of the unperturbed motion of a roll pair and the torque applied to the upper roll as a function of generalized coordinates.It is shown that the width of the contact strip of the clamp, which depends on the radii of the rolls and the hardness of the coatings, has a significant effect on the efficiency of the rolls. The larger the shaft radius, the lower the actual pressure per unit contact area.
 It is shown that the squeezing efficiency increases with the improvement of the conditions for the removal of the squeezable liquid from the rolls (with their horizontal arrangement), with an increase in its temperature and a decrease in viscosity. Efficiency decreases with increasing material speed and thickness.
 It is shown that the width of the contact strip of the clamp, which depends on the radii of the shafts and the stiffness of the coatings, has a significant impact on the efficiency of the shafts. The larger the shaft radius, the lower the actual pressure per unit contact area

Chiral pattern in nonrotating spherical convection

Thermal convection in a nonrotating spherical shell with central gravity is known to have symmetric solutions in terms of three-dimensional discrete rotation. All the solutions have reflection symmetry. We found a new type of symmetric steady convection with chirality. The pattern consists of six pairs of spiral rolls placed on 12 faces of a regular spherical dodecahedron. There are two configurations that are mirror images of one another.

Rancang Bangun Mesin Press Karet Dari Lateks Menjadi Sheet Skala Home Industry

Abstract
 Rubber press machine is a tool used to press rubberfrom lumps into sheets or sheets that have been determined in thickness. This machine works with three pairs of rolls and after calculating the planning of the rubber press machine, the roll size is obtained: length 500 mm, Roll Diameter 76.2 mm, with 3 inch pipe iron material. Rubber press machine power 0.09628 kW, speed 0.204653 m/second. Motor power 0.17035 kW. Shaft, Diameter of shaft 20 mm, Material of shaft carbon steel, Moment of torsion of shaft 2736,7635 kg/mm2, Shaft shear stress 361,74468 kg/mm2. Frame, Frame length 150 cm, Frame height 110 cm, frame width 60 cm. Pegs, 7 mm width of the key, 30 mm of key length, 7 mm of key thickness, 4 mm of keyway depth on the shaft, Shear stress on the key, 1,303 kg/mm2, Allowable shear stress on the post 3,055 kg/mm2. Pully, pulley ratio A : 4, pulley belt speed 3.88 m/s, pully diameter 203.2 mm, pully rotation 365 rpm, shaft axis distance 320 mm. Comparison of pully B: 2.6667, speed of belt pully 1.455 m/sec, length of belt 1118,048 mm, diameter of pully 203.2 mm, rotation of pully 136.87 rpm, axle distance of 240 mm. Comparison of pully C: 2.6669, speed of pully belt 0.545 m/sec, belt length 1118,048 mm, pully diameter 203.2 mm, pully rotation 51.32 rpm, shaft axis distance 240 mm. Comparison of pulleys D and E: 1, pulley belt speed 0,545 m/sec, belt length 1318,048 mm, pully diameter 203.2 mm, pully rotation 51.32 rpm, shaft axis distance 340 mm. Bearing, Bearing number 6004, Inner diameter 20 mm, Outside diameter 42 mm, Bearing width 12 mm, Dynamic nominal capacity 735 kg, Static nominal capacity 465 kg, Axial load 51.15 kg, Radial load 170.5 kg, Dynamic equivalent load 169.6475 kg, Static equivalent radial load 196.675 kg.

Application and effect of hybrid grinding techniques on the quality of stone chakki atta (whole wheat flour) and flat bread.

Industrially packaged whole wheat flour (atta) is manufactured in motorized stone chakkis, which consumes more electric power. Present study is aimed towards evaluating the effect of hybrid grinding technique of wheat using roller mill on its grinding characteristics and quality of chakki atta and chapatti. Wheat was passed through the pair of first break rolls in MLU 202 with the roll gaps of 1 and 0.9mm for two different samples. Electrical parameters for grinding energy were compared and the pre-milled wheat was ground in the stone chakki. Atta obtained from 2 different variations and control stone chakki atta were compared for physico-chemical, rheological and chapati making quality. Damaged starch increased from 15.25 for control atta to 17.3% for 0.9mm sample, whereas, farinograph water absorption increased from 75.9 to 78.9% respectively. Chapatis were prepared and sensory studies were carried out. Chapati colour was found to be brighter for 0.9mm sample.

Experiments on natural convection in a horizontal slot with surface corrugation

In order to better understand how critically the small surface irregularity affects the formation of thermal convection, natural convection in a horizontal slot with surface corrugation was examined experimentally at Rayleigh number based on the slot half-height below 300. The sinusoidal surface corrugations whose amplitude was 2.5% of the slot full-height and wavenumber was 0.5 - 2 was applied on the bottom surface while upper surface was kept smooth. Both walls were heated uniformly at different temperature. The results showed that surface corrugation promoted the occurrence of thermal convection significantly, that is, a pair of convection rolls whose wavelength was the same as that of corrugation was observed at Rayleigh number much lower than the critical one of smooth slot. Beyond critical Rayleigh number, on the other hand, the Rayleigh-Benard convection dominated the flow regardless of corrugation wavelength examined.