Modeling of the Sheet Rolling Process
Abstract Generated abstract
This paper describes an experimental model for studying stress distributions in sheet rolling mill rolls, developed to assess whether rolling can be modeled by the interaction of one roll with another under conditions closer to actual rolling. The model stand includes work and backup rolls, adjustable roll gap, force measurement by strain gauges, optical access to the contact zone, and a photoelastic work roll examined with a polarization-optical apparatus, with provisions for varying strip thickness, deformation, and rolling speed. Experiments on the model indicated that maximum shear stresses are not located at the roll surface in contact with the rolled metal, but are displaced inward by about one sixth of the roll radius, with the displacement depending on strip thickness and reduction.
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MODELING OF THE SHEET ROLLING PROCESS
N. F. ZIMA, G. D. DEL
(Presented by the scientific seminar of the Department of Strength of Materials)
The overwhelming share of all smelted metal passes through various stages of pressure working, with rolling being of the greatest importance, since it serves not only for the production of finished rolled products, but also for obtaining a variety of blanks for other types of processing. Sheet-material rolling occupies a large proportion of rolling. In this connection, the question of increasing the strength and durability of rolling-mill rolls is of primary importance. This work was carried out on assignment from
Fig. 1. Model diagram
TsNIITMash with the aim of resolving the question of the possibility of modeling the rolling process by rolling one roll over another. Studies of this kind have been conducted by a number of authors [1, 2]. The proposed model of the mill stand is more closely approximated to real rolling conditions. The mill model consists of a stand and an electric drive. The design of the stand is determined by the requirement of the maximum field of view in the contact zone of the work roll with the backup roll. The model has two backup and two work rolls. The rolls are arranged in a horizontal plane. One pair of rolls is capable of moving in order to regulate the gap between the work rolls. To move the movable pair of rolls, a special device with a screw drive was made. The force acting on the movable pair of rolls is recorded by means of wire ...
gauges glued to the screw-drive plate. One work roll is made of an optically active material based on ED-6 epoxy resin. The roll axes are centered, and their final machining was carried out after assembly on the axis between centers. The axes are mounted in special bronze plain bearings. To create a plane stress state and to model the rolling of wide sheets—rolling without spread—a groove is made on the steel roll across the width of the strip being rolled.
Fig. 2a. Distribution of maximum shear stresses over the roll diameter
Both work rolls are driven. The drive is provided either by an AC electric motor with a power of 0.25 kW; \(P = 1360\) rpm through two worm reducers \(i = 30 \times 40\) and a reducer with replaceable gears, or by a DC electric motor using an EMU-5 P electromechanical amplifier for stepless regulation of the roll speed in order to assess the influence of rolling speed on the distribution of stresses in the mill roll. The investigation is carried out on a PPU-7 polarization-optical apparatus.
The general arrangement of the setup is as follows: the optical device is placed on a special table. On the same table the drive with the electric motor is located. The model of the mill stand is built into a break in the support of the optical device. When the electromechanical amplifier is connected with the DC motor, the general arrangement does not change, and the electrical circuit (rectifier, EMU-5 P, disconnecting switch) is placed outside the stand. This circuit makes it possible to vary the rolling speed over rather wide limits. Thus, on the manufactured model of the rolling-mill stand it is possible to obtain the distribution of stresses in the rolls as a function of the thickness of the sheet being rolled, the rolling speed, and the degree of deformation of the sheet.
Fig. 2b. Pattern of fringes during rolling of a lead strip
The experiments carried out made it possible to determine a peculiarity in the distribution of shear stresses (Fig. 2). The maximum of these stresses is not located on the surface of contact with the metal being rolled, but is shifted toward the center by \(1/6\) of the radius. The shift depends on the thickness of the strip being rolled and on the degree of its deformation. The question of the influence of this fact on the strength of the roll is a subject for further research.
REFERENCES
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P. I. Polukhin, V. P. Polukhin, Yu. D. Zheleznov, V. Yu. Markovskii. Investigation of stresses and strains in the rolls of sheet mills by the method of three-dimensional photoelasticity. Izv. vuzov “Chernaya metallurgiya”, No. 4, 1962.
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P. I. Polukhin, Yu. D. Zheleznov, V. P. Polukhin. Investigation and calculations of the contact strength of rolling-mill rolls using the method of photoelasticity, in: Engineering Methods for Calculating Technological Processes of Metal Forming. Metallurgizdat, 1963.