Pair Of Rolls Research Articles

Limitations of vehicle movement resistances: rolling resistance

In the paper limitations and exemplary methods of rolling resistance minimization are described. Changes of value of rolling resistance coefficient during years and values for exemplary rolling pairs are presented. Conclusions about future progress are formulated.

The Two-Volume Archetype of the Pauline Corpus

ABSTRACT An extremely ancient edition of the Pauline corpus collecting 14 epistles into a pair of rolls, with Hebrews heading the second roll, arguably underlies the text and numbering in Codex Vaticanus. For such an arrangement, a plausible rationale is apparent, mainly involving considerations of length (perhaps further influenced by inclusion of 2 Peter as an epilogue). Furthermore, this lost two-volume edition can explain many difficulties surrounding the early evolution of the corpus. Transitioning to the single-volume codex format motivated the segregation of Hebrews from the public epistles into a distinct group alongside the four pastorals, with Galatians left still before the slightly longer Ephesians, and the resulting well-attested edition and its derivatives account for nearly all witnesses of the corpus. The exceptional 𝔭46 stems from an imperfect attempt to replicate this edition from a two-roll exemplar, while several distinctive features of Marcion’s Apostolicon derived independently from the two-volume edition. Both the titles of the epistles and the “in Ephesus” in Ephesians were absent in the original two-volume edition but were supplied when its contents were incorporated into a larger New Testament compilation. From this two-volume edition, likely assembled by Luke, all subsequent collections of Paul’s epistles have arguably descended.

Extended Simulations of the Roll Bonding Process

AbstractRoll bonding is a joining‐by‐forming process in which two or more layers of different metals are passed through a pair of flat rolls. Under the high pressure, a permanent bond between the metals is generated by plastic deformation. The main factors influencing this process and the creation of bond strength are the size of the surface area and the normal pressure in the interface. In order to numerically predict the bond strength the FE implementation of a contact algorithm is performed. Simultaneously, the physical mechanisms typical of plastic deformation are taken into consideration. The focus particularly lies on the micro‐mechanical modeling of strain hardening by dislocation slip. A first study is given on the effects of the chemical impurities on the dislocation density and motion.

Patterns of particle convection in a mono-size granular system under coupling vibration and airflow

Convection patterns in a mono-size granular system are studied experimentally in a 3D-cylindrical container under coupling vibration and airflow. The granular system has been changed from the non-fluidized state to the fluidized state with increasing the air velocity. The phase diagrams of particle convection in four different particle size systems are provided. When decreasing vibration frequency (f = 15–45 Hz), increasing vibration acceleration (Γ = 2–7), or increasing air velocity (u = 0–1.81 m/s), particle convection shows three patterns in turn: one pair of rolls, one single local roll, and one single global roll. These convection patterns can be observed when particle size is increased from 2 mm to 8 mm. However, the pattern forming conditions of vibration and airflow are different with the change of particle size. Particle convection depends strongly on vibration and airflow parameters, and the convection intensity is enhanced when the convection pattern changes from one pair of rolls to one single global roll. The convection intensity has a close relationship with convection patterns.

Interactive data visualization of chatter conditions in a cold rolling mill

Rolling of flat steel products is an industrial process in the field of metalworking where two or more pairs of rolls reduce the thickness of a steel strip to produce a uniform thickness material. Despite it has been studied for many years, there are still unpredictable problems that can affect the final quality of the product. One of them is the so-called chatter, that is a powerful self-excited vibration that appears suddenly and limits the productivity of the process. In this paper, a visual analytics approach is considered for exploratory analysis in order to discover and understand the factors and conditions under which chatter appears. An interactive web-based interface is presented here which allows the user to explore a map of dynamical conditions and visualize relevant details of each chatter onset. A validation case is performed using real data where normal/fault conditions have been identified automatically. By means of interactive exploration, the tool allows to refine an automatic chatter detection method. Moreover, it is shown to reveal correlations between variables, providing in some expected cases data-based confirmation, but also revealing less obvious relationships. Finally, it provides context, allowing to carry out comparative analysis, both qualitative and quantitative, for different subsets of coils (e.g. different years) as well as for different working conditions.

Effect of roller mill configuration on growth performance of nursery and finishing pigs and milling characteristics.

Three experiments were conducted to evaluate the effects of roller mill configuration on growth performance of nursery and finishing pigs, feed preference, and feed mill throughput. The four experimental treatments included corn ground through a roller mill using two, three, four sets of rolls in a fine-grind configuration, or four sets of rolls in a coarse grind configuration. The same roller mill was used for all configurations with the appropriate lower rolls completely open when using the two or three roll pair configurations. Across all studies, mean particle size averaged approximately 540, 435, 270, and 385 µm for the four roller mill configurations, respectively. In Exp. 1, 320 pigs (DNA 400 × 200, initially 10.7 ± 0.27 kg BW) were randomly allotted to treatments with five pigs per pen and 16 pens per treatment in a 21-d growth trial. While there were no evidence of differences observed for ADG or ADFI, pigs fed corn ground using the 4-high coarse configuration had a marginally significant (P = 0.091) improvement in G:F compared with those fed with the 2-high configuration, with others intermediate. In Exp. 2, 90 pigs (PIC 327 × 1050, initially 12.1 ± 0.25 kg BW) were randomly allotted to one of three diet comparisons to determine feed preference between the 2-high, 4-high fine, and 4-high coarse configurations. When given a choice, pigs consumed more (P < 0.05) of the diet containing corn ground through the 2-high roller mill (67%) or 4-high coarse configuration (63%) compared with corn ground through the 4-high fine configuration. In Exp. 3, 922 finishing pigs (PIC TR4 × [FAST Large white × PIC Line 2], initially 40.1 ± 0.36 kg BW) were used in a 97-d experiment with pens of pigs randomly allotted by initial BW to the same experimental treatments used in Exp. 1. There were 21 pigs per pen and 11 pens per treatment. Pigs fed corn ground with the 2-high configuration had greater (P < 0.05) ADG compared with those fed corn ground using the 3-high configuration. Pigs fed corn ground with the 4-high fine configuration had the poorest (P < 0.05) ADG. No differences were observed in G:F. Grinding rate (tonne/h) was greatest (P < 0.05) for the 4-high coarse configuration, while net electricity consumption (kWh/tonne) was lowest (P < 0.05) for the 2-high configuration and greatest for the 4-high fine configuration. In summary, nursery pig G:F tended to be greatest using the 4-high coarse configuration, and finishing pig ADG was maximized using the 2- and 4-high coarse configurations.

A METHOD FOR DETERMINING THE DISTRIBUTION OF LOADS IN ROLLING PAIRS IN CYCLOIDAL PLANETARY GEAR

The power transmission system in the cycloidal planetary gear is created by a serial connection of three rolling pairs: central cylindrical roller bearings, a set of rolling pins in the straight-line mechanism, and cycloidal meshing. The paper presents the numerical method for determining the distribution of forces acting on each rolling pair of this gear. Unlike analytical methods, numerical methods allow one to find that distribution in corrected meshing. Geometrical dimensions used in the equations of balance for the planetary gear transmission Palmgren`s dependences for the deformation line contact were used to calculate forces between co-operating elements. Once the distribution of load is known, one can predict the fatigue life of Cyclo’s gears in rolling pairs. The fatigue of rolling pairs is a very good criterion to optimize geometrical parameters of the power transmission system.

Phase-coexisting patterns, horizontal segregation, and controlled convection in vertically vibrated binary granular mixtures.

We report patterns consisting of coexistence of synchronous and asynchronous states [for example, a granular gas co-existing with (i) bouncing bed, (ii) undulatory subharmonic waves, and (iii) Leidenfrost-like states] in experiments on vertically vibrated binary granular mixtures in a Hele-Shaw cell. Most experiments have been carried out with equimolar binary mixtures of glass and steel balls of same diameter by varying the total layer height (F) for a range of shaking acceleration (Γ). All patterns as well as the related phase diagram in the (Γ,F) plane have been reproduced via molecular dynamics simulations of the same system. The segregation of heavier and lighter particles along the horizontal direction is shown to be the progenitor of such phase-coexisting patterns as confirmed in both experiment and simulation. At strong shaking we uncover a partial convection state in which a pair of convection rolls is found to coexist with a Leidenfrost-like state. The crucial role of the relative number density of two species on controlling the buoyancy-driven granular convection is demonstrated. The onset of horizontal segregation can be explained in terms of an anisotropic diffusion tensor.

Research on flexible asymmetric rolling process for three-dimensional surface parts

To realize rapid fabrication of three-dimensional surface parts, flexible asymmetric rolling process for continuously forming surface parts is developed. This process employs an auxiliary roll, a pair of upper and lowers bendable rolls as forming tools. By adjusting the height of the auxiliary roll, the sheet metal is inclined before non-uniform rolling, which is conducive to longitudinal bending deformation of the sheet metal after rolling. Meanwhile, the non-uniform thickness reduction of the sheet metal caused by the non-uniform roll gap between the upper and lower rolls makes itself bend in the transverse and longitudinal directions. Owing to small bending behavior of the bendable roll in the experiment, the forming precisions of formed parts are not ideal by the 3D rolling process without the auxiliary roll. In this paper, the flexible asymmetric rolling process is introduced to improve the 3D rolling process for surface parts with well forming precisions. An auxiliary roll is employed in the flexible asymmetric rolling process except a pair of upper and lower rolls. The formation mechanism of the curved surface is set forth, and the parametric equations of the formed surface in flexible asymmetric rolling process are derived. Typically simulations and experiments for forming spherical and saddle surfaces have been performed. The dimensional accuracies of the forming parts are measured, and the differences of the 3D rolling and flexible asymmetric rolling processes are investigated though numerical simulations. The forming results with good dimensional accuracies show that the flexible asymmetric rolling process is feasible for manufacturing three-dimensional surface parts with a broader range.

Alternating Sign Rolling Technology in Grooved Rolls for Nonferrous Metal Plate Billets

Results are given for a study of rolling plate metal by technology including rolling in grooved rolls and levelling on a smooth barrel. Results of computer modeling and analysis of the Lode–Nadai coefficient show that during rolling in grooved rolls two types of deformation-compression arise in a billet cross section, i.e., compression in inclined areas and shear in ridged zones. This picture of stress distribution is most favorable since compressive strain leads to “healing” of possible metal discontinuities, but shear deformation leads to intense working of the original metal structure. During rolling in the first pair of smooth rolls deformation compressive in nature predominates, and in the second pair of rolls it is deformation alternating in nature. In any billet vertical section, metal contact with rolls occurs on both surfaces, i.e., upper and lower, which leads to compression in ridge zones, but to tension in inclined sections. Analysis of the results of metallographic studies points to the benefits for rolling in grooved rolls in the plan of preparing a metal fine-grained isotropic structure. The use of grooved rolls leads to significant strengthening of L63 brass compared with using smooth rolls with an identical overall degree of deformation.

Convection induced by vibrating rod in fine-powder bed

In this study, vibration-induced convection was studied experimentally using a fine powder with a mass median particle diameter of 8μm. A cylindrical rod arranged vertically in a powder container was vibrated horizontally with simple harmonic motion at a frequency of 300Hz using a piezoelectric vibrator. For a vibration amplitude of 10μm, particles around the cylindrical rod were consolidated to a certain extent due to gravity; however, for a vibration amplitude of 70μm or more, a pair of convection rolls formed on both sides of the vibrating rod. The strength of the convection was quantified from the particle velocity distribution in the convection rolls, and the relationship between the convection strength and vibration amplitude was elucidated. In addition, the air-pressure distribution in the powder bed was measured showing that the convection strength correlates with the characteristic positive pressure, i.e., the average value of positive pressure measurements. Elliptical motion and circular motion as well as simple harmonic motion were applied to the cylindrical rod by adding two harmonic motions in directions orthogonally crossing each other with a phase difference of π/2rad. The convection of the particles varied according to the Lissajous trajectory of the cylindrical rod. Even for simple harmonic motion, heaps of a pair of convection cells overlapped each other. In the case of elliptical motion, the overlapping portion of the heaps became larger. In the case of circular motion, the two heaps were integrated into one circular heap, and there were no effects of the circumferential angle on the particle velocity and the characteristic positive pressure.

Analysis of continuous roll forming for manufacturing 3D surface part with lateral bending deformation

Continuous roll forming (CRF) is a novel technology for both single-piece and small-batch manufacturing of 3D surface sheet metal parts. In the CRF process, a pair of flexible rolls is placed to form a non-uniform roll gap. When the flexible rolls rotate in opposite directions with identical angular velocity, the sheet metal is bitten into the roll gap by frictional force, and the sheet metal is non-uniformly thinned in thickness direction and elongated in longitudinal direction. Thus, a 3D surface part with a desired shape is manufactured consecutively. In this paper, CRF is further developed and expanded into LB-CRF, which enables the CRF process to manufacture 3D surface parts not only with transverse and longitudinal bending deformation but also with lateral bending deformation (LB-CRF). The methods to design the curved profiles of flexible rolls and the distribution of the roll gap are provided. Through a series of numerical simulations on the LB-CRF processes, the proposed design methods are verified. The relationship between the distribution of the roll gap and radius of lateral bending curvature is discussed. The LB-CRF processes were presented through experiments, and the results validate the feasibility of adopting the LB-CRF process to manufacture 3D surface part with lateral bending.

カーボンブラック充塡加硫天然ゴム，イソプレンゴムおよび脱タンパク質化天然ゴムのフィラーの分散構造と物性

Relationship between morphology and mechanical properties of vulcanized rubber samples filled with carbon black was investigated. Samples of natural rubber (NR), isoprene rubber (IR) and deproteinized natural rubber (DPNR) were prepared using an internal mixer with a pair of 6-inch or 8-inch rolls. Dispersion of carbon black was evaluated by transmission electron microscopy and small-angle/ultra-small-angle X-ray scattering. Difference in tensile strength of the NR samples prepared by different pairs of the rolls was very small. This may be attributable to almost equal quality of the carbon black dispersion in the two kinds of NR samples. The tensile strength and volume resistivity of the IR sample were different from those of NR and DPNR samples, because of different quality of carbon black dispersion between IR and the other samples.

Rayleigh–Bénard convection driven by a long wavelength heating

Natural convection in a two-dimensional horizontal layer has been investigated. The layer is confined between two parallel horizontal plates. The upper plate is kept isothermal, while the lower plate has an externally imposed, long wavelength, spatially sinusoidal heating with the amplitude expressed in terms of the Rayleigh number Ra and the wavelength characterized by the wave number α. Only steady-state flow structures and their bifurcations have been considered. The detailed analysis has been carried out for two Prandtl numbers, i.e. Pr = 0.7 and Pr = 7, and only small differences in the bifurcation diagrams have been observed. When Ra 427. When 427 ∼470 and α > ~0.14, bifurcation assumes the form of “bifurcation from infinity”. The main branch is associated with one pair of rolls per heating period for α > 0.25. Decrease in α along this branch results in the formation of secondary rolls, with the rolls at the hot spot co-rotating with the primary rolls. The lower part of the other branch is associated with one pair of rolls per heating period in the limit α → 0. Increase in α results in pinching off a single roll which counter-rotates with respect to the primary roll at the hot spot.

A rotary reduction of fine wires/tubes of a wide range of diameters using a pair of concave rolls

This paper presents an innovative rotary reduction method of elongated fine solid wires and hollow tubes, the diameters of which could be reduced to 0.02 times of diameter of rolls as the tool. A pair of concave rolls is positioned at a skew angle to the material axis, and the rolls compress the material. The material travels between the rolls in a spiral movement with tension applied on its ends. The method is applicable for a very wide range of diameters using the same tools. Diversified shapes would be fabricated as the method reduces the diameter at arbitrary axial positions.

A twin disc test rig for contact fatigue characterization of gear materials

Pitting on gear tooth flanks is one of the major causes of failure in power transmissions. Cracks originate at the surface and propagate at a small depth causing the detachment of material debris, which results in craters. Pitting is detrimental as it leads to vibration, noise, loss of efficiency and eventually to the gear un-serviceability. The contact fatigue characterization of gear materials requires a great number of endurance tests on reference gears and is rarely affordable for industries. For this reason, the ISO standard 6336 suggests that tests on rolling pair of disks may be performed in order to compare the pitting durability of either different materials or manufacturing processes. However, the standard does not provide guidance about the geometry of the specimens and the correlation between the results of disc tests and actual gears durability.In this paper a twin-disc test rig is presented, that was conceived to reproduce the contact pressure and the sliding velocity of gears at one particular point along the tooth profile. A criterion for specimens design is also described. The discs were sized to resemble the working conditions experienced by sun gears mounted in the final drive of an axle for medium power Off-Highway vehicles. In particular, the Lower Point of Single Tooth Contact (LPSTC) was considered to design the tests, being the most favourable location for pitting occurrence because of the high contact pressures and unfavourable kinematic conditions.

Design and Control of a Parallel Robot for Mold Polishing

A novel redundantly actuated parallel robot for mold polishing work is proposed. Cogging-less direct drive motors are implemented in the prototype. Instead of using conventional spherical sliding bearings, ball bearings with appropriate preload are implemented in the rolling pairs of the prototype. These mechanical parts enable fine force control for mold polishing work. The rated force of the robot perpendicular to the surface on the workpiece is 20 N with a tangential force of 5 N, which enable the robot to execute polishing tasks as well as skilled workers. In addition, the polishing velocity along the tangential direction is 60 m/min, which exceeds skilled workers’ velocity of 10 m/min. High speed feed contributes to reducing the polishing force and improving the quality of the surface of the mold. Kinematics, statics, dynamics and control of redundantly actuated parallel robot are discussed in this paper. Impedance control was implemented to the prototype for stably executing the mold polishing work.

Curvature control in radial-axial ring rolling

Abstract: Radial-axial ring rolling (RARR) is an industrial forging process that produces seamless metal rings with uniform cross-section using one radial and one axial rolling stage. Conventionally, the ring products are circular and the process is tightly constrained using guide rolls for stability, and to ensure the circularity and uniformity of the ring. Recent work has shown that when guide rolls are omitted, stability can be maintained using differential speed control of the roll pairs. However, achieving uniform curvature in this unconstrained configuration was not always possible when the controller only centred the ring within the rolling mill. In addition to the regulation of constant curvature in circular rings, differential speed control in unconstrained rolling offers an opportunity to bend the ring about the mandrel to create shapes with nonuniform curvature, for example: squares, hexagons, rings with flat sections, etc. We describe a control technique for creating non-circular rings using the rolling hardware of a conventional RARR mill, machine-vision sensing and differential speed control of the rolling stages. The technique has been validated for an industrial material in numerical simulations using the finite element method and also demonstrated on a desktop-scale RARR mill using modelling clay to simulate metal at elevated process temperatures.

The change of work roll surface topography during skin pass rolling of steel sheets

Purpose – This paper aims to analyze changes in the surface topography of the work rolls during skin passing. Cold rolled steel sheets are additionally subject to skin pass rolling to form an appropriate surface topography. This operation should facilitate the process of further metal forming of steel sheets, such as deep drawing, painting, etc. The surface topography of steel sheets is determined by the surface topography of the work rolls as well as the skin pass rolling parameters (rolling speed, elongation, roll force, etc.). Suitable preparation and selection of roll surface topography influences the degree of rolls wear and the surface topography of steel sheets as well. Design/methodology/approach – Two-dimensional (2D) and three-dimensional (3D) roughness measurements of work roll surface before, during and after finishing of skin pass rolling of steel sheets are presented in the paper. The measurements were performed on four sets of work rolls with different surface topography. Findings – The appearance of the surface of rolls obtained from the analysis of 3D roughness, the values of selected parameters of the 3D roughness and relative changes of the roughness parameter Ra/Sa depending on the length of the skin passed steel sheets are presented. Practical implications – The wear of rolls is different depending on work surface topography. Originality/value – The aim of this paper is to analyze changes in the surface topography of the work rolls during skin passing. It was expected that the surface of work rolls with more summits at similar average roughness Ra will change much faster than the surface with fewer summits. For this purpose, preliminary tests were performed in an industrial environment on four pairs of work rolls, including two pairs of rolls that were hard chromium-plated.

On the accuracy of mechanisms with kinematic rolling pairs

Specific issues in the calculation of the accuracy of mechanisms with kinematic rolling pairs are considered. Characteristic forms of expressions are provided for mean and limit travel errors for a batch of mechanisms manufactured according to the same design. It is shown that, with respect to these mechanisms, travel errors are implementations of nonstationary random functions. Adjustment techniques are recommended that enhance the operational accuracy of the mechanisms.