1,977,877 research outputs found
Stability of rigid and deformable roll coating flows
No full textThis thesis is concerned with developing suitable models for the investigation of instabilities in rigid and deformable roll coating flows. Consideration is restricted to Newtonian, incompressible fluids in the absence of inertia. In each coating flow analysed the steady two dimensional base state solutions of the system axe explored before the stability of the system is considered.
The particular rigid roll coating flow that is studied in this thesis is the flow formed between an intermediate pair of contra-rotating rolls within a multiple roll coater. The
base state is modelled using lubrication theory and the flow domain is terminated with simple boundary conditions. It is found that the form of the meniscus location
solutions differ from those found in similax flows by previous workers and this motivates a detailed re-examination of the boundaxy conditions. A matched asymptotic analysis applicable for small capillaxy numbers Ca and small inter-roll gaps gives the leading order correction to the boundary conditions and it is found that the inclusion of the correction terms alter the results significantly. It is found that a critical roll speed ratio,
Sc exists beyond which no steady two dimensional solutions exist. A simple stability hypothesis predicts the upstream meniscus to be neutrally stable at Sc and this point is
associated with bead break. Under certain operating conditions the stability hypothesis predicts multiple steady states.
The lineax stability of this multiple roll coating flow is investigated. Special attention is given to the relationship between the wavelength of the disturbance and
the form of the boundary conditions. The main predictions of the stability hypothesis axe confirmed and an additional ribbing instability on the downstream meniscus is predicted.
The base flow of a deformable roll coater is investigated using lubrication theory for the fluid and a linear elastic plain strain model for the compliant layer. The boundary
conditions developed for the multiple roll problem are extended to higher values of Ca. A finite element method is developed to numerically solve the governing equations.
The effects of Youngs modulus E and layer thickness L on the steady state operation of the coater are investigated. Previous workers have used spring models to describe
the compliant layer with the implicit assumption that E and L-1 have the same affect. Here it is shown that E and L-1 have a different effect upon the meniscus location in the negative gap regime and hence the underlying assumption of all spring models is shown to be incorrect. The plain strain model is extended to include viscoelastic terms
and it is shown that these terms can account for the discrepancy between experimental results and previous steady state elastic theories.
The lineax stability of the deformable roll coater is investigated with the plain strain model being extended to account for lateral disturbances. The effect of E and L-1 on
the stability of the system is investigated and it is found that in keeping with the steady state results, they have a different effect on the stability of the system in the
negative gap regime. It is demonstrated that perturbations to the compliant layer play a negligible role in the stability analysis and it is shown how the viscoelastic extension to the base state can be incorporated
Rolling mill roll design
No full textIn this thesis, some previously published experimental and theoretical studies of hot rolling are reviewed. A thorough understanding of the available roll design methods, and conditions of their application is extremely important in order to achieve the objective of producing high quality rolled products. Successful hot roll design is dominated by the calculations of some important parameters, which describe two-dimensional (2D) or three-dimensional (3D) deformation in the workpiece. These parameters, such as roll separation force, torque, elongation, spread and draft, are discussed in detail. The method or formula for the calculation of each parameter is different for each set of different application conditions. A thorough study of these methods in different application cases will lead to the optimised design of hot rolled products. Finite Element (EE) is an important method which has been employed in the study of hot rolling. Design theory, commercial software and application cases have been described. 2-D and 3-D Finite Element Methods (FEM) for hot rolling simulation have also been discussed within the work. The current techniques and the problems of using the Finite Element system in hot roll design have been presented briefly. Possible solutions to these problems have also been discussed and there need to be considered in order to successfully apply Finite Element theory in hot roll design. An important alternative approach for hot roll design has been introduced in this thesis. A Matrix-based roll design system has been developed. It includes a Matrix-based system for flat and section roll designs. The realisation of the Matrix-based system is discussed. All the methods and formulae considered previously can be integrated in the proposed roll design system. The approach emphasizes the need for teamwork. The design procedure allows both less experienced designers and senior designers to benefit from participation. It is suggested that high quality rolled products could be achieved from optimised designs produced using this systematised the approach compared to the ad-hoc use of existing techniques, formulae and methods
Dupla vagy semmi
No full text1.Dupla vagy semmi /Dolly Roll +2.Sztár volt Lollypop /J. Roberts - M. Levy - R. Spencer - Dolly Roll +3.Boldog remény /G. Gouldman - Dolly Roll +4.Édensziget /Dolly Roll +5.Még úgy fáj /B. Ram - A. Rand - Dolly Roll +6.Simogass, napsugár /Novai - Dolly Roll +7.Reklámbébi /Novai - Dolly Roll +8.Elpattant egy húr /Novai - Dolly Roll +9.Do wah diddy diddy /Barry - Greenwich - Dolly Roll +10.Hazugság vagy igazság /Dolly Roll +11.Ma-nah ma-nah /P. Umiliani - Dolly Roll +12.Egy tenyér ha csattan /Dolly Roll +13.Happy birthday kis Krisztin /N. Sedaka - H. Greenfield - Dolly Roll +14.Végleg a szívügyem maradtál /Dolly Roll +15.Jumbo jet /Dolly Roll +16.Álmodj velem! /Novai - Dolly Roll +17.Handicap /Dolly Roll +18.Ábrándos szép napok /G. Raskin - Dolly Roll +19.Zakatol a szív /Dolly Rol
Ship roll stabilization control with low speed loss
No full textLarge roll motion induced by waves can severely affect the ability of vessels and the speed will loss due to added resistance which caused by ship motions, especially in moderate to high sea states. With increasing needs of fuel efficiency and greenhouse gas (GHG) emissions, the effect of added resistance on surface ship performance must be considered when a ship fin stabilizer control system is designed. In this paper, we investigate basic principles of added resistance in oblique waves and ship calm water resistance. An alternative approach for reducing speed loss while keeping the satify roll reduction percentage, is proposed by controlling both roll and roll rate at the same time. A double nonlinear generalized minimum variance (NGMV) controller is used for achieving this objective. Finally, the effectiveness of the method is demonstrated
Manuscript: J.L. Roll's Audition for Posterity
No full textType, 4 pages, questions and answers about the Lincoln family
Work Roll Cooling System Design Optimisation in Presence of Uncertainty
No full textOrganised by: Cranfield UniversityThe paper presents a framework to optimise the design of work roll based on the cooling performance. The
framework develops Meta models from a set of Finite Element Analysis (FEA) of the roll cooling. A design of
experiment technique is used to identify the FEA runs. The research also identifies sources of uncertainties
in the design process. A robust evolutionary multi-objective algorithm is applied to the design optimisation I
order to identify a set of good solutions in the presence of uncertainties both in the decision and objective
spaces.Mori Seiki – The Machine Tool Compan
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