Maximum Rolling Research Articles

Adaptive Radiation Therapy for Postprostatectomy Patients Using Real-Time Electromagnetic Target Motion Tracking During External Beam Radiation Therapy

Using real-time electromagnetic (EM) transponder tracking data recorded by the Calypso 4D Localization System, we report inter- and intrafractional target motion of the prostate bed, describe a strategy to evaluate treatment adequacy in postprostatectomy patients receiving intensity modulated radiation therapy (IMRT), and propose an adaptive workflow. Tracking data recorded by Calypso EM transponders was analyzed for postprostatectomy patients that underwent step-and-shoot IMRT. Rigid target motion parameters during beam delivery were calculated from recorded transponder positions in 16 patients with rigid transponder geometry. The delivered doses to the clinical target volume (CTV) were estimated from the planned dose matrix and the target motion for the first 3, 5, 10, and all fractions. Treatment adequacy was determined by comparing the delivered minimum dose (Dmin) with the planned Dmin to the CTV. Treatments were considered adequate if the delivered CTV Dmin is at least 95% of the planned CTV Dmin. Translational target motion was minimal for all 16 patients (mean: 0.02 cm; range: -0.12 cm to 0.07 cm). Rotational motion was patient-specific, and maximum pitch, yaw, and roll were 12.2, 4.1, and 10.5°, respectively. We observed inadequate treatments in 5 patients. In these treatments, we observed greater target rotations along with large distances between the CTV centroid and transponder centroid. The treatment adequacy from the initial 10 fractions successfully predicted the overall adequacy in 4 of 5 inadequate treatments and 10 of 11 adequate treatments. Target rotational motion could cause underdosage to partial volume of the postprostatectomy targets. Our adaptive treatment strategy is applicable to post-prostatectomy patients receiving IMRT to evaluate and improve radiation therapy delivery.

The effects of lubrication on roll compaction, ribbon milling and tabletting

Lubricants are commonly used in the pharmaceutical industry to prevent adhesion and improve the efficiency of roll compaction and tabletting. The aim of the current work is to develop an improved understanding of the mechanisms involved. Two commonly used pharmaceutical excipients, microcrystalline cellulose (MCC) and di-calcium phosphate dihydrate (DCPD), were selected as the model feed powders with magnesium stearate (MgSt) as the lubricant. An instrumented roll compactor was used, the ribbons were milled using an oscillating mill and the granules were compressed into tablets. The wall and internal friction angles of the feed powders were measured and related to the performance of the roll compaction that was characterised by the nip angle and maximum pressure. The milling performance was related to the fracture energy of the ribbons. The tabletting was assessed by the density and strength of the tablets. A qualitative interpretation of the data was developed and the practical implications of the work are considered. It was also shown that the bulk lubrication results in the reduction in internal friction for MCC but not for DCPD. The wall friction of DCPD is reduced by both bulk and wall lubrication unlike MCC for which the friction coefficient is essentially unchanged. The behaviour of the powders in roll compaction can be ascribed to the variation of the frictional properties due to lubrication. It is found that wall lubrication does not affect either the nip angle or the maximum roll pressure during roll compaction of MCC, but for DCPD the nip angle and maximum pressure are reduced with wall lubrication. In addition, the nip angle and the maximum pressure during roll compaction of MCC and DCPD are reduced with bulk lubrication. Furthermore, bulk lubrication causes reduction in the bonding properties and hence the tensile strength for MCC, but not for DCPD.

Effect of Internal Clearance on Load Distribution and Life of Radially Loaded Ball and Roller Bearings

The effect of internal clearance on radially loaded deep-groove ball and cylindrical roller bearing load distribution and fatigue life was determined for four clearance groups defined in the bearing standards. The analysis was extended to negative clearance (interference) conditions to produce a curve of life factor versus internal clearance. Rolling element loads can be optimized and bearing life maximized for a small negative operating clearance. Life declines gradually with positive clearance and rapidly with increasing negative clearance. Relationships were found between bearing life and internal clearance as a function of ball or roller diameter adjusted for load. Results are presented as life factors for radially loaded bearings independent of bearing size or applied load. In addition, a modified Stribeck equation is presented that relates the maximum rolling element load to internal bearing clearance.

Optimization of cold rolling process parameters in order to increasing rolling speed limited by chatter vibrations

Chatter has been recognized as major restriction for the increase in productivity of cold rolling processes, limiting the rolling speed for thin steel strips. It is shown that chatter has close relation with rolling conditions. So the main aim of this paper is to attain the optimum set points of rolling to achieve maximum rolling speed, preventing chatter to occur. Two combination methods were used for optimization. First method is done in four steps: providing a simulation program for chatter analysis, preparing data from simulation program based on central composite design of experiment, developing a statistical model to relate system tendency to chatter and rolling parameters by response surface methodology, and finally optimizing the process by genetic algorithm. Second method has analogous stages. But central composite design of experiment is replaced by Taguchi method and response surface methodology is replaced by neural network method. Also a study on the influence of the rolling parameters on system stability has been carried out. By using these combination methods, new set points were determined and significant improvement achieved in rolling speed.

Effect of impurity reduction on rollability of AZ31 magnesium alloy

The effect of impurity reduction on the hot rolling behavior of AZ31 magnesium alloy was systematically investigated in this study. In the as-cast alloys, the total content of main impurity elements such as Fe, Si, Cu, and Ni was varied from 0.0462 to 0.0163 wt% by changing the purity of used raw magnesium metals. The alloys after homogenization were subjected to hot rolling at 300 °C with a reduction of 20% per pass. It was found that the initiation of edge cracks is postponed with reducing impurity level in the alloys. And the maximum rolling reduction prior to edge cracking increases from 34 to 58% as the impurity content drops from 0.0462 to 0.0163 wt%. Microstructural observations showed that smaller grains are present in the alloy with lower impurity content in the cast and homogenization states. Moreover, decreasing impurity content leads to a reduced number of deformation twins and an enhanced volume fraction of small recrystallized grains in the as-rolled microstructure, which indicates that impurity reduction is beneficial to the recrystallization process and subsequent plastic deformation. Based on the results, the enhancement in hot rollability of the AZ31 sheet by impurity reduction should be due to finer grain size, the reduced number of deformation twins and the enhanced extent of recrystallization.

Improving machine dynamics via geometry optimization

The central thesis of this paper is that the dynamic performance of machinery can be improved dramatically in certain cases through a systematic and meticulous evolutionary algorithm search through the space of all structural geometries permitted by manufacturing, cost and functional constraints. This is a cheap and elegant approach in scenarios where employing active control elements is impractical for reasons of cost and complexity. From an optimization perspective the challenge lies in the efficient, yet thorough global exploration of the multi-dimensional and multi-modal design spaces often yielded by such problems. Moreover, the designs are often defined by a mixture of continuous and discrete variables—a task that evolutionary algorithms appear to be ideally suited for. In this article we discuss the specific case of the optimization of crop spraying machinery for improved uniformity of spray deposition, subject to structural weight and manufacturing constraints. Using a mixed variable evolutionary algorithm allowed us to optimize both shape and topology. Through this process we have managed to reduce the maximum roll angle of the sprayer by an order of magnitude, whilst allowing only relatively inexpensive changes to the baseline design. Further (though less dramatic) improvements were shown to be possible when we relaxed the cost constraint. We applied the same approach to the inverse problem of reducing the mass while maintaining an acceptable roll angle—a 2% improvement proved possible in this case.

STABILITAS STATIS KAPAL IKAN TIPE LAMBUT TERSANJUNG YANG BERPANGKALAN DI PELABUHAN PERIKANAN SAMUDERA AERTEMBAGA KOTA BITUNG PROPINSI SULAWESI UTARA

Ship is water vehicle with any shape and any purpose, mechanically powered or by windvor tug and categorized as a multipurpose platform. It could be operated underwater or in the surface of water and could function merely as a floating static structure. The natural condition is the fish catching area are unpredictable as the wave an current of the water could disturbing the maneuverability and the stabilty of the ship. For that purpose the fish catching ship should have and meet the criterion of robust construction and strong structure to deal with the extreme condition in the sea and also should have a good maneuverability and enough power to make it move steadily. The total lenght of the sample ship Tersanjung are 15.85 m, the width are 2.90 m and inside the ship measured as 1.32 m. The average comparison among the 3 parameters are 5.50 for L/B, 13.05 for L/D and 2.37 for B/D. The coefficient of the Tersanjung ship are Cb=0.58, Cp=0.96, C =0.60 and Cw=0.87. “Tersanjung” ship has reverse velocity 3.7 second (1 perod). Maximum rolling reaching at 120 with righting moment of 0.21 m.

Influence of the GZ calculation method on parametric roll prediction

Parametrically excited roll response in a container ship sailing in irregular head sea has been studied. Short-term predictions for roll have been made for a ship at a constant forward speed based on different hydrodynamic roll descriptions. The first order reliability method (FORM) has been used to obtain the probability that the roll motion will exceed a given limiting angle. The results have been compared to the results by a Monte Carlo simulation. Using FORM the computational time is greatly reduced as compared to direct simulations, still retaining the probability of failure of the correct order of magnitude. Calculations have been made for different sea states and operational conditions leading to parametric roll resonance and for relevant maximum pre-defined roll angles. The outcome of this comparative study could be useful for the decisions in an early design phase or for application to on-board decision support systems, where a computationally efficient method is needed in order to have an operationally feasible time frame.

Load Distribution of Rolling Bearing for Steel Shapes Universal Roll Mill

At the stage of the start and end for rolling H-beam by universal rolling method, there exists biting and tailing-out phenomenon in the stage, the rolling bodies endures repeating impact loading for the bearings. In order to ensure the working safety and reliability for universal roll mill, according to Hertz contact theory, small deformation superposition principle, and etc. Setting bearing clearance is 0.1 mm, maximum rolling force is 8000 KN for the level rollers, without consideration of influence of friction, and researches and deduces the mathematic models of force calculation for rolling bodies. The results shows that the thickness of the rolling bearing had very little effect on load distribution of rolling body, the calculated results coincide better with finite element results, and the achievements can supply a reference of the production of hot rolling for H-beam.

Understanding variation in roller compaction through finite element-based process modeling

One of primary goals of the Quality by Design initiative in the pharmaceutical industry is to reduce variation in the product quality through increased understanding and control of the manufacturing process. In the case of roller compaction, in which mixtures of active and inert powders are fed via a screw to counter-rotating rolls, drawn into the nip region and compacted under hydrostatic and shear stresses, variation in density of the roller compacted material has been commonly observed. In the experimental part of this work we report measurements of pressure and shear under the rolls which show variation of the local stress conditions along the width of the roll which evolves with time. Also roll pressure and shear stress appear to persist past the minimum roll separation. To further investigate the potential causes of these variations, 2D and 3D explicit finite element-based models with adaptive meshing and arbitrary Eulerian–Lagrangian capabilities were developed. A Drucker-Prager/cap constitutive model was used to describe the mechanical behavior of the powder. Microcrystalline cellulose was used as the model powder. The 2D model was used to evaluate the effects of feed stress, roll friction on roll force, profiles of roll pressure and roll shear stress, nip angle and relative density of the compacted powder. The results indicated increasing feed stress, and/or increasing roll friction lead to higher maximum roll surface pressure and attendant relative density at the exit. The results may be explained by the location of the nip angle and the amount of pre-densification in the feed zone. Simulations with pressure-dependent frictional coefficients indicated significant differences in densification. In addition, oscillating feed stress conditions revealed periodic variations in roll pressures and relative densities. The 3D model predicted lower roll pressure and densities near the edges due to presence of side seal friction. Variable inflow of material along the roll width was related to variation in roll pressure. Overall, the model predictions followed experimental trends. The process modeling provided greater insight into the potential causes of the variation in density of the roller compacted material and highlighted the significance of the design of the feed system, which may be used to evaluate potential design improvements.

Prediction of Formation of Wavy Surfaces in Rolled Plates by Post-Buckling Analysis

Excessive wavy surfaces formed by a cold- or hot-rolling process in a thin plate degrades the value of the plate significantly, which is called the flatness problem in the industry. It is a result of post-buckling due to the residual stress caused by the rolling process. Because the buckling occurs in a very long, continuous plate, a unique difficulty of the problem as a buckling problem is that the buckling length is not given but has to be found. In many previous works, the length that gives the lowest critical load of the plate for the given load profile was taken as the buckling length. In this work, it is shown that this approach is flawed, and a new approach is developed to solve the flatness problem by extending a classic post-buckling analysis method based on the energy principle. The approach determines the buckling length and amplitude without using any unfounded assumptions or hypothesis. Using simple displacement functions, approximate solutions are obtained in closed forms for the plate subjected to a linearly distributed residual stress. The new solution approach can be used to determine the condition for the maximum rolling production that does not cause the flatness problem.

Structural Mechanics of DNA Wrapping in the Nucleosome

Experimental X-ray crystal structures and a database of calculated structural parameters of DNA octamers were used in combination to analyse the mechanics of DNA bending in the nucleosome core complex. The 1kx5 X-ray crystal structure of the nucleosome core complex was used to determine the relationship between local structure at the base-step level and the global superhelical conformation observed for nucleosome-bound DNA. The superhelix is characterised by a large curvature (597°) in one plane and very little curvature (10°) in the orthogonal plane. Analysis of the curvature at the level of 10-step segments shows that there is a uniform curvature of 30° per helical turn throughout most of the structure but that there are two sharper kinks of 50° at ± 2 helical turns from the central dyad base pair. The curvature is due almost entirely to the base-step parameter roll. There are large periodic variations in roll, which are in phase with the helical twist and account for 500° of the total curvature. Although variations in the other base-step parameters perturb the local path of the DNA, they make minimal contributions to the total curvature. This implies that DNA bending in the nucleosome is achieved using the roll–slide–twist degree of freedom previously identified as the major degree of freedom in naked DNA oligomers. The energetics of bending into a nucleosome-bound conformation were therefore analysed using a database of structural parameters that we have previously developed for naked DNA oligomers. The minimum energy roll, the roll flexibility force constant and the maximum and minimum accessible roll values were obtained for each base step in the relevant octanucleotide context to account for the effects of conformational coupling that vary with sequence context. The distribution of base-step roll values and corresponding strain energy required to bend DNA into the nucleosome-bound conformation defined by the 1kx5 structure were obtained by applying a constant bending moment. When a single bending moment was applied to the entire sequence, the local details of the calculated structure did not match the experiment. However, when local 10-step bending moments were applied separately, the calculated structure showed excellent agreement with experiment. This implies that the protein applies variable bending forces along the DNA to maintain the superhelical path required for nucleosome wrapping. In particular, the 50° kinks are constraints imposed by the protein rather than a feature of the 1kx5 DNA sequence. The kinks coincide with a relatively flexible region of the sequence, and this is probably a prerequisite for high-affinity nucleosome binding, but the bending strain energy is significantly higher at these points than for the rest of the sequence. In the most rigid regions of the sequence, a higher strain energy is also required to achieve the standard 30° curvature per helical turn. We conclude that matching of the DNA sequence to the local roll periodicity required to achieve bending, together with the increased flexibility required at the kinks, determines the sequence selectivity of DNA wrapping in the nucleosome.

A new airborne tandem platform for collocated measurements of microphysical cloud and radiation properties

Abstract. A new airborne tandem measurement platform for cloud-radiation interaction studies is introduced in this paper. It consists of a Learjet 35A research aircraft and the AIRcraft TOwed Sensor Shuttle (AIRTOSS), which is an instrumented drag-body towed by the Learjet. Currently, the AIRTOSS is instrumented with a Cloud Imaging Probe (CIP) for measuring cloud microphysical properties and an Inertial Navigation System (INS) for measurements of flight attitudes. The cable dragging AIRTOSS can be as long as four kilometres. Thus, truly collocated measurements in two altitudes above, in, and below clouds can be obtained. Results from first test flights with Learjet and AIRTOSS are reported here. The flights were performed from Hohn Airport, Germany. Specific manoeuvres were flown to test the aerodynamic behaviour of the drag-body and to investigate the suitability of AIRTOSS for high-precision irradiance measurements which require a stable flight attitude of AIRTOSS. The flight attitude data show that AIRTOSS is sensitive to several flight manoeuvres such as turns, altitude and airspeed changes, and also to changes of towing cable length. The effects of these manoeuvres on the attitude angles of AIRTOSS have been quantified. Maximum roll angle deviations were observed during turns. Even small changes in heading can lead to high roll angles (one degree change in heading causes a change in roll angle of about eight degrees). The pitch angle varies during climb or dive periods, extending or retracting of towing cable, acceleration or deceleration, and even when flying at too low or too high true airspeed depending on altitude. Values of pitch angle between −5° (dive) and 8° (climb and retracting towing cable) have been observed. While change in attitude is not problematic for cloud particle property measurements it is for radiation measurements. Here, the deviation from the horizontal should be no more than 3° to avoid large errors. When keeping the above mentioned flight parameters constant, sufficiently stable flight conditions can be maintained to perform high-quality irradiance measurements with AIRTOSS in future experiments. During this test campaign also observations of cloud microphysical data as for example droplet number concentrations and size distributions with the AIRTOSS in stratocumulus clouds were performed to prove the compliance with scientific needs. Simultaneous spectral cloud radiation measurements have been made. The measurements of internal operational data of AIRTOSS as well as the first atmospheric data demonstrate the suitability of this tandem platform for detailed cloud microphysics and radiation interaction studies.

Influence of billet enthalpy on the temperature field of the product in high-speed rolling

45 A typical setup in high-speed (up to 100 m/s) wire mills consists of a continuous roughing and intermediate group of cells, a finishing module, and two-stage cooling lines for the wire rod. The 150 mill at the Belorussian Metallurgical Plant is of this type. Continuous-cast billet (cross section 125 × 125 mm; length 10‐12 m) is heated in a stepping-floor furnace, with simultaneous turning in the heating zone. The equipment of the 150 mill includes a five-cell continuous roughing group of horizontal cells, in which the rolled metal is turned after cells 1, 3, and 5. These are very rigid cells of modern design, with short-barrel rollers. The first and second intermediate groups include six and four cantilever cells, respectively. The disk rollers of cells 7‐10 are made of special steel; those of cells 11‐16 are made of hard alloys. Beyond cell 16, there are water-cooling sections. Between cell 16 and the tencell finishing module, the direction of motion of the rolled product turns through 180 ° . The configuration, characteristics, and structure of the equipment in the mill may be found, together with the production technology for carbon-steel and alloy-steel wire rod, in [1]. The maximum rolling speed is 100 m/s. In modern wire and rod‐wire mills, the production of wire rod and circular billet generally involves both plastic and thermal treatment of the metal, i.e., the influence of structural defects of the heated and deformed steel on its structure properties during cooling and heat treatment is put to use [2]. Modification of the structure and properties by combined heat treatment and deformation is widely employed [3‐6]. The potential of particular methods depends on the chemical composition of the steel and its required properties, the configuration and characteristics of the equipment, the size range of the products, the strain, and so on. The effectiveness of heat treatment and deformation in changing the structure and properties of wire rod will depend on the possibility of regulating the temperature over the length of the mill and the final temperature of the rolled steel. Other important factors are the parameters of postdeformational treatment and the range of possible cooling rates. According to the global classification, three types of treatment are employed at modern rolling mills: hightemperature deformational treatment; normalizing rolling; and thermomechanical treatment. In all cases, after the rolled steel leaves the last cell, heat treatment continues, with certain stipulations on the temperature conditions and the cooling rate before and during γ α transformation. In high-temperature deformation, rolling ends at a temperature that is at least 150 ° C higher than the initial temperature of structural transformation (point Ar 3 ), depending on the quantity of carbon and alloying elements in the steel. In high-temperature deformation, the load on the technological equipment is reduced and its performance is improved. However, fairly large austenite grains are formed in the metal. The dominant mechanism is dynamic recrystallization in the course of rolling, at high temperature and critical strain. Therefore, at the end of deformation, all the grains may be regarded as newly formed. Repeated deformation and recrystallization reduces the austenite grain size; on entering the finishing module, it is 20‐25 µ m. With further cooling at a specified rate in the second stage of the Stelmor process, the required structural transformation occurs.

Efficient estimation of extreme non-linear roll motions using the first-order reliability method (FORM)

In on-board decision support systems, efficient procedures are needed for real-time estimation of the maximum ship responses to be expected within the next few hours, given online information on the sea state and user-defined ranges of possible headings and speeds. For linear responses, standard frequency domain methods can be applied. For non-linear responses, as exhibited by the roll motion, standard methods such as direct time domain simulations are not feasible due to the required computational time. However, the statistical distribution of non-linear ship responses can be estimated very accurately using the first-order reliability method (FORM), which is well known from structural reliability problems. To illustrate the proposed procedure, the roll motion was modelled by a simplified non-linear procedure taking into account non-linear hydrodynamic damping, time-varying restoring and wave excitation moments, and the heave acceleration. Resonance excitation, parametric roll, and forced roll were all included in the model, albeit with some simplifications. The result is the mean out-crossing rate of the roll angle together with the most probable wave scenarios (critical wave episodes), leading to user-specified specific maximum roll angles. The procedure is computationally very effective and can thus be applied to real-time determination of ship-specific combinations of heading and speed to be avoided in the actual sea state.

Mechanical Properties of New Type Negative Offset Structure During Shearing Process of Heavy Steel Plate

Abstract According to the revised Cailikefu's rolling shear force formula, motion path equation of spatial seven-bar path was built, and a mechanical model, with the new structural feature of negative offset, was thus successfully established for 2 800 mm heavy shear of some iron and steel company. Shear and bar forces of steel plate, before and after the adoption of negative offset structure, were analyzed, as well as horizontal force component of mechanism that influences pure rolling shear and back-wall push force that keeps blade clearance. It was found that the back-wall push force keeps large even at the time that the maximum rolling shear was obtained; meanwhile, back-wall push force is the most approximate to side forces when 60 – 100 mm of offset was adopted. Both theoretical results and on-site shear quality show that the negative offset plays an important role in ensuring the stability of pure rolling shear and keeping blade clearance constant.

Using intelligent software to predict the effects of formulation and processing parameters on roller compaction

Roll compaction is a dry, continuous granulation process, which is widely used in the pharmaceutical, chemical, metallurgical, mineral and agricultural industries to produce dust-free and free-flowing agglomerates. Intelligent software has been used to predict the relationships between tablet formulations, roll compaction process parameters and the roll compacted ribbon, from which granules for tablet manufacture can be produced. The software exploits the strengths of artificial neural networks, genetic algorithms and fuzzy logic to predict multivariate relationships from experimental data. Input data were generated from material characterisation studies and from investigations conducted on a 20 cm diameter laboratory-scale roll press with side plates, where process parameters such as roll speed (1–5 rpm), roll gap (0.5–1.4 mm) and compaction pressure (up to 230 MPa) could be manipulated. The relative significance of inputs on various outputs such as ribbon properties, nip angle and maximum roll compaction pressure was investigated using the commercially available artificial intelligence software FormRules (Intelligensys, Teeside, UK). The important inputs and required outputs were subsequently used in the model-development software INForm (Intelligensys, Teeside, UK) so that the conditions necessary to produce ribbons with specific desired properties could be predicted.

INFLATION AT THE MAXIMA OF SYMMETRIC POTENTIALS

We construct a two-stage inflationary model which can accommodate early inflation at a scale Λ1 as well as a second stage of inflation at Λ2 with a single scalar field ϕ. We use a symmetric potential, valid in a frictionless world, in which the two inflationary periods have exactly the same scale, i.e. Λ1 = Λ2. However, we see today Λ1 ≫ Λ2 due to the friction terms (expansion of the universe and interaction with matter). These type of models can be motivated from supergravity. Inflation occurs close to the maxima of the potential. As a consequence both inflations are necessarily finite. This opens the interesting possibility that the second inflation has already or is about to end. A first inflation is produced when fluctuations displace the inflaton field from its higher maximum rolling down the potential as in new inflation. Instead of rolling towards a global minimum the inflaton approaches a lower maximum where a second inflation takes place.

Mathematical Modeling of Draft Schedule for In-line Rolling of Ultra Thin Strip in the Combined Single-belt Casting/Hot Rolling Process

The single-belt process is a new route to produce steel strips, in which the single-belt caster is directly connected with hot mills. This process should be able to roll strip with thickness 1 mm or below. In hot rolling of the ultra thin strip there are many limitations which are represented by the finishing rolling temperature of the strip, the oxidation of the strip, the overheat of the roll and the maximum rolling speed. In the present paper the possibility of hot rolling ultra thin strip in the single-belt process was investigated. On the basis of mechanical/thermal/metallurgical behavior of the strip a mathematical model of draft schedule was proposed. In terms of different criteria the draft schedule was optimized. The results show that austenitic hot rolling of ultra thin strip in the single-belt process can be carried out like the conventional hot rolling for low carbon steels. With consideration of roll life the maximal roll surface temperature has a large influence on the establishment of the draft schedule for hot rolling of ultra thin strips.

PASS SCHEDULE OPTIMIZATION FOR A TANDEM COLD MILL

Pass schedules for a tandem cold mill affect not only the uniformity quality and productivity of rolled strips but also the operation safety. This paper describes pass schedule optimization, which consists of two stages. One is robust pass schedule optimization (RPSO) before rolling, which optimizes pass schedules under distributions in strips' properties and rolling conditions. The other is mill balance control (MBC) during rolling, which slowly changes the pass schedules to cope with remaining distributions and unpredictable during-rolling variations. Results with an actual mill showed an 8% decrease in off-gage length and a 2.4% increase in maximum rolling speed without deterioration in gage accuracy.