Roll Position Research Articles

Forced Phase Diffusion in Rayleigh-Bénard Convection

The first experimental evidence of the diffusive character of the phase variable which describes the position of the convective rolls is presented. To produce a phase modulation a small alternating flow in a slightly supercritical fluid layer is injected. With use of this method, the diffusion coefficient ${D}_{\ensuremath{\parallel}}$ concerning the propagation of phase disturbances parallel to the roll axis is measured.

Automatic Control of the Calendering Process for Plastics

The paper deals with some important topics of new developments in calender automation-scheme design. Introductory the whole automation concept is outlined, based on the calendering process for plastics sheet and the method of suboptimal thickness control with a process computer AEG 80-20. In detail a lot of problem solutions to automatic measurement and control of calendered plastics sheet are considered, for instance parallel measurement of the thickness-profile on three control points, time-optimal scanning of the cross-section with a traversing sensing head, data-filtering with poor delay, compensation of the backlash-phenomenon in the screw-down servomechanism, using a mathematical backlash-model; design of the nonlinear multivariable system by decoupling, adaptaion schemes with respect to the variable parameters of the production- and process management system and to the elastic properties of the screw-down mechanism, cascade roll-gap control with eccentricity-filtering of the roll position data. Furthermore the application of identification methods as a powerful tool for starting and testing the automatic control system is demonstrated and operational results are discussed, achieved from a realized computer-based calender-process automation system in Western Germany.

Automatic control of the calendering process for plastics

The paper deals with some important topics of new developments in calender automation-scheme design. Introductory the whole automation concept is outlined, based on the calendering process for plastics sheet and the method of suboptimal thickness control with a process computer AEG 80-20. In detail a lot of problem solutions to automatic measurement and control of calendered plastics sheet are considered, for instance parallel measurement of the thickness-profile on three control points; time-optimal scanning of the cross-section with a traversing sensing head; data-filtering with poor delay; compensation of the backlash-phenomenon in the screw-down servomechanism, using a mathematical backlash-model; design of the non-linear multivariable system by decoupling; adaptaion schemes with respect to the variable parameters of the production- and process management system and to the elastic properties of the screw-down mechanism; cascade roll-gap control with eccentricity-filtering of the roll position data. Furthermore the application of identification methods as a powerful tool for starting and testing the automatic control system is demonstrated and operational results are discussed, achieved from a realized computer-based calender-process automation system in Western Germany.

Analysis of Three-Dimensional Optimal Evasion with Linearized Kinematics

Abstract : Three-dimensional optimal missile avoidance is analysed with a linearized kinematic model. The solution requires maximum load factor and the problem is reduced to optimal roll position control having two phases: (1) orientation of the lift vector into the optimal evasion plane, (2) rapid 180 roll meanuvers governed by a switch function. For circular missile vectograms the plane of optimal evasion is perpendicular to the line of sight. Evading from roll stabilized missiles of rectangular vectogram, further advantage can be taken maximizing the target-missile maneuver ratio. Bounded rollrate reduces the miss distance but does not affect the optimal evasive maneuver structure. (Author)

Influence of spin rate on side force of an axisymmetric body

Results are presented for an experimental study in which a 10-deg half-angle pointed cone model 57.9 cm long and made of magnesium (for lightness and minimization of inertial effects) is spun at several rates about its axis of symmetry. The model is spun in both directions, but most of the data presented are for the counterclockwise rotation. The resulting side force is recorded on an oscillograph. It is shown that the side force observed occurs under conditions of spin about the longitudinal axis, and that the general shape of the side-force curve with roll position does not depend strongly on spin rate. However, the peak-to-peak value of side force decreases substantially with spin rate, suggesting that the vortices producing the side force require a significant amount of time to change position and/or strength.

An Electrostatic Roll Sensor for Supersonic Vehicles Part I: Feasibility and Flight Tests

A simple, rugged, and low-cost roll sensor developed for model aircraft has been adapted for use on supersonic missiles and projectiles. Pairs of ionizing elements placed symmetrically about the vehicle roll axis sense the vertical electrostatic gradient in the earth's atmosphere, which produces a voltage differential between sensors proportional to their vertical separation distance. Recessing the sensors below the supersonic freestream allows adequate ionization to occur and thus maintains sensor sensitivity. Large separation distances between individual sensors are not required to generate a sufficient voltage differential. Several missile and projectile flight tests were conducted at velocities up to Mach 2.1, roll rates between 2-13 Hz, and altitudes ranging from sea level to 3000 ft. Under these test conditions, sensor accuracy was generally within ±5 deg of true roll position.

Hydrodynamic fluctuations near the convection instability

Hydrodynamic fluctuations of a horizontal liquid layer heated from below are considered in the vicinity of the point where convection sets in because of buoyancy. It is assumed that convection occurs in the form of nearly two-dimensional rolls. Close to the instability, the hydrodynamics (described in the Boussinesq approximation) is simplified considerably by the appearance of a slow mode which dominates the motion of all hydrodynamic variables. It is described by a slowly varying complex amplitude whose absolute value and phase describe the strength and the position of the convection rolls, respectively. Generalizing previous work by several authors, an approximate equation of motion is derived, which is satisfied by the slow variable. New in this analysis is the inclusion of fluctuating terms, which leads to a Langevin equation. The fluctuations are shown to satisfy a detailed-balance principle. Consequently, a generalized thermodynamic potential can be defined, which was discussed briefly in an earlier paper. It depends as a functional on the slow variable, which thereby assumes the role of an order parameter of the transition. I give a further evaluation of the hydrodynamic fluctuations for a horizontally unbounded liquid layer on both sides of and at the B\'enard point by using my potential and applying various approximations. For strictly two-dimensional flows (i.e., independent of one horizontal coordinate) I calculate the time-independent steady-state properties (coherence lengths) without any further approximation by relying on published numerical data obtained for one-dimensional Ginzburg-Landau fields. Dynamic steady-state properties (coherence times) for that case and fluctuations in the three-dimensional case are calculated in a quasilinear approximation which reproduces the time-independent results for two-dimensional flows reasonably well. In the purely heat-conducting region my results contain some earlier results of Zaitsev and Shliomis in lowest order. Large and long-lived fluctuations of velocity and temperature are shown to appear at the critical wave number as the liquid is brought near the convection instability. They are due to the random appearance and disappearance of convection cells. Their size and lifetime at the B\'enard point are only limited by nonlinear coupling of the critical modes to other passive modes. In the heat-convection region, the coupling to passive modes stabilizes the amplitude of the convection cells; only slow fluctuations of the positions of the rolls remain (for unbounded layers) and destroy the long-range order of the one-dimensional roll lattice, in agreement with well-known general theorems. If the B\'enard point is approached from this side, the stabilizing influence of the passive modes decreases and is efficient only for the large fluctuations at the B\'enard point. Approached from either side, the B\'enard point resembles the critical point of a Landau phase transition. The width of the region around the B\'enard point where the Landau description breaks down is calculated and found to be unobservably small in realistic liquids. An experimental check of these results, though very tedious, seems possible and very worthwhile.

Geology of Felder Uranium Deposit, Live Oak County, Texas: ABSTRACT

The Felder ore deposit is a 5 million-lb uranium deposit in the South Texas coastal plain. It occurs in the basal sandstone of an Oakville Formation (Miocene) alluvial system. The host sandstone is a carbonate-rich arkose which contains virtually no carbonaceous debris and has been reduced by the local introduction of hydrogen sulfide. The ore lies well within the reduced zone and occurs as coffinite and uraninite that fill interstices and coat and replace grains. The overall geometric configuration of the ore is that of a winged, crescentic ore roll. Weak mineralization extends the wings of the ore roll and gives greater expression to the roll character. Departures from the shape are controlled by discontinuities in bedding and by proximity of the ore to the surface. Associated with the uranium is a broad halo of anomalous molybdenum. Subsidiary mineralized trends suggest a preexisting updip position for the main roll. Oxidation from the surface largely destroyed this previous roll by solubilization of uranium. Uranium subsequently migrated into favorably reduced sandstone and reprecipitated at the present roll position. End_of_Article - Last_Page 1393------------

Reentry Vehicle Radar Altimeter Antenna Patterns

An analytical technique is proposed for investigating the effect of antenna pattern shape on reentry vehicle radar altimeter performance. Initially, a method is presented that computes the average performance under all roll positions. This method is then extended to allow performance to be determined at each roll position. Some numerical results are included that show roll effects for a typical antenna pattern.

Experimental Study of Shear Spinning

Many researchers have done some work on the analysis of shear spinning process. But their works are limited to a certain extent. This paper deals with the experiment on the shear spinning process of aluminium to find out the fundamental characters in detail. The influence of the following working conditions is discussed ; roller position angle, clearance between roller and mandrel, feed of roller, cone angle, speed of rotation of mandrel, roller corner radius, roller diameter, blank thickness and blank diameter. In addition, the deformation theory of simple shear which is derived from the observation of the experiments, is checked about tangential force Pθ. It is said that there is an optimum blank thickness ts, of which the calculated values agree with the experiments, and if the blank thickness is smaller than ts, the theoretical value is overestimated, but underestimated, if it is the other way round.

A Device for Automatically Tracking the Roll Position of a Missile

Many short range missiles are guided in angle or range by optical means. Since these missiles are usually caused to roll in flight for stability reasons, some type of roll position reference device is necessary. The only type of roll reference device in use is a gyro, although various horizon scanners, Doppler, and optical methods have been considered. This paper describes an optical method of roll reference which utilizes the relative positions of two flares of different color attached to the rear of the missile. Since the roll position is known at the launch point, commands to the missile are commutated at the launch point rather than in the missile as is necessary when a gyro or other missile-borne roll reference device is used. Thus, the roll tracker removes from the missile two subsystems (gyro and commutator) while adding two components (two colored flares).

Experimental Study of Some Variables of the Tube-Expanding Process

This paper deals with certain aspects of the tube-expanding process, which have been investigated using the test rig previously developed as part of a research sponsored by the British Shipbuilding Research Association. The factors investigated are (1) retubing, (2) the starting position of the roller cage within the tube, and (3) the initial clearance between tube and seat. A few tests are also reported on the relaxation of the joint with time. In the retubing tests, further tubes were expanded into seat plates used in previous tests, from which the original tube had been removed. The main conclusion was that seat pressures can approach the theoretical maximum in retubing, and that if an extra pass is made to take advantage of the work-hardened seat, a stronger joint than in a first expanding results. To study the effect of the starting position of the rollers within the joint, four complete tests were made. The results show conclusively that a much stronger joint is obtained with less work, if the rollers start with their front ends almost at the back of the joint. Tests to study the effect of the initial clearance between tube and seat showed that clearance is not a major factor in joint strength.

The Effect of Bottom Front Roll Run-Out in Spinning on Yarn Quality and Processing Performance

Measurement of bottom front roll run-out at every spinning stand position in a typical mill indicates that only a small percentage of the stands have run-outs that are exces sively high. It was found also that square neck jointed rolls in the two plants studied have higher roll run-outs than screw neck jointed rolls. A reasonable explanation for this is that the square neck jointed rolls generally receive rougher handling. since con siderable force is required when separating or putting together the sections of the rolls on the spinning frame. Periodic irregularities are introduced in the yarn by eccentric bottom front rolls which lower the quality of the yarn being produced. With increases of bottom front roll run- out from 0.000 in. to 0.010 in., the following properties of 31 1 warp yarn were affected to the extent shown: As the roll run-out increased, the pattern on yarn appearance boards became more dis tinct. Analysis of the yarn properties indicated that yarn quality was appreciably lowered at bottom front roll run-outs in excess of 0.0055 in. A study of the processing performance of the yarn produced at various bottom front roll run-outs indicates that yarns produced at high roll run-out positions are more difficult to process in spooling and weaving. In this study, there was an increase of 12% in the number of breaks in spooling as the bottom front roll run-out increased from ranges of 0.000-0.003-0.006 in. and higher. With these same ranges of roll run-outs, warp stops in weaving increased 48% when the weavability of the yarn produced at low roll run-out positions was compared with yarn produced at high roll run-out positions in spinning. The appearance grade of 80 X 80 print cloth, woven with filling yams produced at various roll run-out positions, was found to decrease with increases in bottom front roll run-outs. All graders that ranked the fabrics selected the fabric having the highest roll run-out as being the worst fabric in the group. However, no correlation was found be tween the appearance grade of 110 X 58 broadcloth woven with warp yarn produced at different bottom front roll run-outs in spinning.

Trouble Shooting in Textile Processing by Use of the Brush Uniformity Analyzer

There are many mechanical faults in cotton processing which may cause periodic variations in the resulting yarn, roving, or sliver. Each of these defects causes a particular pattern of thick and thin places in the resulting material. An eccentric part (roll or gear) on a drawing, roving, or spinning frame results in a wavy pattern of thick and thin places in the material. The pattern formed in the material by a flat spot in the top roll is dependent upon the position (front, second, third, or back) on the particular frame. A flat spot in the back roll position has very little effect on the resulting material. In the third roll position (four roll frame) it yields a thin place directly followed by a thick spot, while a defective front roll causes periodic thick places in the material. Defective bottom rolls on the drawing frame affect the sliver differently, depending upon the position on the frame. Defective drafting rolls used primarily as delivery rolls have a greater effect on the resulting material than defective rolls used primarily as feed rolls. Most of these mechanical faults have a particular pattern which can be distinguished by proper use of the Uniformity Analyzer. There are certain settings (pen average, pen sensitivity, chart speed, and material speed) which can be used on the Brush Uniformity Analyzer to assist in the search for periodic variations. The particular setting to use when searching for periodicities is generally dependent upon the distance between the expected periodic variation. For closely spaced periods (3 to 10 in.) in the material, a fast chart speed (25 mm./sec. or 125 mm./sec.) and the pen average at position 0 or 1 is generally used. A slow chart speed (5 mm./sec.) and the pen average at position 2 or 3 will illustrate longer periodic variations. The pen sensitivity control is generally used to increase the amplitude of the variations on the chart after the pen average and chart speed have been selected.

The Roll-setting Method of Automatic Control of Gauge in Hot and Cold Rolling Mills

When strip is rolled at a constant speed, errors in the finished thickness occur owing to changes in width, hardness, and thickness of the incoming material, in tensions applied to it, and to variations in friction in the roll gap. The gauge of strip may also vary when the mill speed is changed. A closed-loop regulator had been constructed to demonstrate, on a pilot-plant scale, a method of automatically controlling the gauge of sheet and strip rolled in hot and cold mills. A measure of the departure from gauge is obtained from simultaneous measurements of roll-load and the roll-setting, and correction is made by varying the position of the rolls. The controller is described together with experiments which demonstrate that the method is capable of consistent rolling to close tolerances in gauge.

Improvements in Rolling Mill Preset Screw-Down Controllers

In the rolling mill screw-down pre-positioning control system discussed in this paper, the use of electronic-balance detectors and anticipators permits higher screw-down motor speeds without loss of accuracy in the final positioning of the rolls. The electronic-balance detectors replace polarized contact-making ammeters while balance anticipators permit the introduction of slow-down motor circuits for accurate stopping. This latter feature could not be provided so readily by the earlier control method. A new system of schedule panels on which one or more complete rolling schedules may be preset is a definite and important improvement over the earlier design. In the new panels, it is necessary to locate only two plugs for each pass per schedule while in the older method employing cords, it was necessary to locate both ends of two cords, making four connections per pass per schedule. Freedom from the complicated network of cords makes the set-up procedure more rapid and certain.

A position regulator for paper slitters

PAPER slitters are used to trim the edges of paper webs so that a paper roll with even sides can be wound from an unevenly wound roll. When the paper has printed designs on it, the slitting must be done at a definite distance from the printed design. The slitter knives are stationary as shown in figure 1. In order to slit the paper at the same position relative to the design when the position of the paper relative to the shaft of the unwinding roll is varying, it becomes necessary to adjust the position of the unwinding roll transversely.

A position regulator for paper slitters

PAPER slitters are used to trim the edges of paper webs so that a paper roll with even sides can be wound from an unevenly wound roll. When the paper has printed designs on it, the slitting must be done at a definite distance from the printed design. The slitter knives are stationary as shown in figure 1. In order to slit the paper at the same position relative to the design when the position of the paper relative to the shaft of the unwinding roll is varying, it becomes necessary to adjust the position of the unwinding roll transversely.