Shape Prediction of the Sheet in Continuous Roll Forming Based on the Analysis of Exit Velocity

Continuous roll forming (CRF) is a new technology that combines continuous forming and multi-point forming to produce three-dimensional (3D) curved surfaces. Compared with other methods, the equipment of CRF is very simple, including only a pair of bendable work rolls and the corresponding shape adjustment and support assembly. By controlling the bending shapes of the upper and lower rolls and the size of the roll gap during forming, double curvature surfaces with different shapes can be produced. In this paper, a simplified expression of the exit velocity of the sheet is provided, and the formulas for the calculation of the longitudinal curvature radius are further derived. The reason for the discrepancy between the actual and predicted values of the longitudinal radius is deeply discussed from the perspective of the distribution of the exit velocity. By using the response surface methodology, the effects of the maximum compression ratio, the sheet width, the sheet thickness, and the transverse curvature radius on the longitudinal curvature radius are analyzed. Meanwhile, the correction coefficients of the predicted formulas for the positive and negative Gaussian curvature surfaces are obtained as 1.138 and 0.905, respectively. The validity and practicability of the modified formulas are verified by numerical simulations and forming experiments.

Numerical Simulation of Buckling and Post-Buckling Behavior of a Central Notched Thin Aluminum Foil with Nonlinearity in Consideration

In thin notched sheets under tensile loading, wrinkling appears on the sheet surface, specifically around the cracked area. This is due to local buckling and compression stresses near the crack surfaces. This study aims to numerically study the buckling behavior of a thin sheet with a central crack under tension. A numerical model of a notched sheet under tensile loading is developed using the finite element method, which considers both material and geometrical nonlinearity. To overcome the convergence problem caused by the small thickness-to-length/width ratio and to stimulate the buckling, an imperfection is defined as a small perturbation in the numerical model. Both elastic and elasto-plastic behavior are applied, and the influence of them is studied on the critical buckling stress and the post-buckling behavior of the notched sheet. Numerical results for both elastic and elasto-plastic behavior reflect that very small perturbations need more energy for the activation of buckling mode, and a higher buckling mode is predominant. The influences of different parameters, including Poisson’s ratio, yield limit, crack length-to-sheet-width ratio, and the sheet aspect ratio are also evaluated with a focus on the critical buckling stress and the buckling mode shape. With increase in Poisson’s ratio. First, the critical buckling stress reduces and then remains constant. A higher yield limit results in increases in the critical buckling stress, and no change in the buckling mode shape while adopting various crack length-to-sheet-width ratios, and the sheet aspect ratio changes the buckling mode shape.

Automatic control of the rolling mode “at an angle” on a reversing hot rolling mill

One of the most important indicators of the quality of control of the rolling process on a plate mill is the accuracy of obtaining the geometric dimensions of rolled metal, which determines the cost of metal per ton of product, in particular, the accuracy of the implementation of a given width. The sheet width exceeding the width of the initial billet, under rolling on plate mills, is obtained at the stage of breaking the width in a horizontal stand. Breakdown of the width in most cases is carried out by rolling the workpiece at an angle of to the longitudinal axis of the future sheet. However, if the rotation of the roll (slab) is not possible at the stated angle (for example, when the width of the roll is less than the distance between the rollers), then a part of the considered stage is carried out by rolling “at an angle” less than . In the process of such rolling, the dimensions of the roll along all axes and its shape in plan are changed (initially the rectangular shape takes the form of a parallelogram). The paper describes the mathematical description for one of the options for forming the width of a thick sheet when rolling “at an angle” in relation to an automated control system for the technological process of a plate mill. On the basis of the concepts describing the formation of the roll in the plan during rolling “at an angle”, the expressions were obtained that relate the parameters of the roll and the rolling mode. The problem of automatic control of the rolling mode “at an angle” is formulated. The proposed calculation of the rolling mode, which is implemented at a pace with the rolling process, provides a rectangular roll of a predetermined width for a minimum number of passes, subject to restrictions on the reduction in passes. The described approach to the automatic control of the rolling mode during rolling at the “angle” is implemented in the mathematical support of the system for calculating the rolling parameters and heat hardening of the plate mill 5000.

Nonlinear Finite Element Modelling for Reinforced Concrete Beams Retrofitted with FRP in Bending

For the purpose of simulating the behaviour of reinforced concrete (R.C)[1] beams retrofitted with fibre-reinforced polymers/plastics (FRP)[2] in bending, a finite element (FE)[3] modelling procedure has been developed throughout this paper. The FE software package ABAQUS CAE 6.11-3 was used. The data required for such modelling process are boundary conditions, geometric and material properties. Non-available material properties are obtained through experimentally verified numerical material models. FRP isotropic and orthotropic material models are compared; both models nearly yielded similar results. Also, perfect bond model and cohesive zone model for the interface between concrete and FRP have been compared. Unlike the perfect bond model, the cohesive zone model captured the debonding. The modelling procedure was validated through its application to R.C beams retrofitted with FRP in bending. The FE model results were compared to experimental results where both results were highly correlated. Such results include load-deflection curves and cracking pattern. The effect of sheet width and number of FRP layers is emphasized through performing a parametric study. Increasing sheet width is only effective at longer sheet lengths regarding increasing both; stiffness and load carrying capacity. Upon increasing the number of FRP layers, only shifting of the yielding point of reinforcement was noticed.

ABONOS ORGÁNICOS Y SU EFECTO EN EL CRECIMIENTO Y DESARROLLO DE LA COL (Brassica oleracea L)/ ORGANIC FERTILIZERS AND THEIR EFFECT ON GRAIN GROWTH AND DEVELOPMENT OF CABBAGE (Brassica oleracea L.)

Los abonos orgánicos constituyen una de las alternativas en el grupo de productos utilizados en la agricultura sustentable, fundamentalmente aquellos que se obtienen a partir de fuentes orgánicas de carácter reciclables como la composta y la vermicomposta. El objetivo del presente estudio fue determinar el efecto de abonos orgánicos en el crecimiento y desarrollo de plantas de col verde. Los tratamientos aplicados fueron vermicomposta, Jacinto de agua, y la combinación 50% vermicomposta y 50% Jacinto de agua y un control, mediante un diseño completamente al azar con cuatro repeticiones. Las variables evaluadas fueron altura de la planta, número de hojas, largo de hojas, ancho de hojas, peso y circunferencia del repollo. Los resultados mostraron que el uso de Jacinto de agua en plantas de col verde estimuló las variables altura de la planta con 23.80 cm, número de hojas con 11.16, largo de hojas con 21.06 cm, ancho de hojas con 17.43 cm y el pesó y circunferencia del repollo con 388.86 55.53 cm respectivamente, sin diferir de la vermicomposta y la mezcla entre ambos. ABSTRACTOrganic fertilizers are one of the alternatives in the group of products used in sustainable agriculture, primarily that which is obtained from organic sources of recyclable nature as compost and vermicompost. The aim of this study was to determine the effect of organic fertilizers on the growth and development of plants of green cabbage. The treatments applied were vermicompost, water hyacinth, and the combination 50% vermicompost and 50% water hyacinth control through a completely randomized design with four replications. The evaluated variables were plant height, leaf number, leaf length, leaf width, weight and circumference of cabbage. The results showed that the use of water hyacinth plants stimulated variables green cabbage plant height with 23.80 cm, number of sheets 11.16, along with 21.06 cm sheets, sheet width 17.43 cm and weight and girth cabbage with 55.53 g 388.86 cm respectively, without differ from the vermicompost and the mixture between them.

Edge behaviour in the glass sheet redraw process

Thin glass sheets may be manufactured using a two-part process in which a sheet is first cast and then subsequently reheated and drawn to a required thickness. The latter redrawing process typically results in a sheet with non-uniform thickness and with smaller width than the cast glass block. Experiments suggest that the loss of width can be minimized and the non-uniformities can be essentially confined to thickening at the sheet edges if the heater zone through which the glass is drawn is made very short. We present a three-dimensional mathematical model for the redraw process and consider the limits in which (i) the heater zone is short compared with the sheet width, and (ii) the sheet thickness is small compared with both of these length scales. We show that, in the majority of the sheet, the properties vary only in the direction of drawing and the sheet motion is one-dimensional, with two-dimensional behaviour and the corresponding thick edges confined to boundary layers at the sheet extremities. We present numerical solutions to this boundary-layer problem and demonstrate good agreement with experiment, as well as with numerical solutions to the full three-dimensional problem. We show that the final thickness at the sheet edge scales with the inverse square root of the draw ratio, and explore the effect of tapering of the ends to identify a shape for the initial preform that results in a uniform rectangular final product.