FEM Simulation of the Roll Deformation of Six-high CVC Mill in Cold Strip Rolling
Accurate prediction for the deformation of the roll system is a key to improve the accuracy of the preset model and on-line control model of strip cold rolling processes. A non-linear finite element contact model to simulate the roll system deformation has been developed for the CVC-6h cold strip rolling mill. The elastic-plastic deformation of the strip and the elastic deformation of the rolls are coupled in this model by the contact and friction between the roll and strip. The effects of the work roll bending force, the middle roll bending force and the middle roll transverse shifting on the roll gap profile have been analyzed systematically. Results show that the work roll bending is the most effective mean in these strip shape controlling means. The calculated roll gap profile is close to the measured values. This model can improve the accuracy of final products through a correct preset model and on-line control model of strip shape.
A rigid-plastic finite element analysis of temper rolling process
Abstract A study on temper rolling process has been carried out using rigid-plastic finite element method. Rigid-plastic formulation can be used to predict the roll force and roll torque and to study the deformation field of the rolled sheet. Hitchcock’s formula for roll deformation does not consider the effect of frictional traction on the roll deformation. Hence, to account for high friction present in temper rolling, the roll deformation is computed in an iterative manner using theory of elasticity solution considering roll as an elastic half space. The study reveals that some of the assumptions made for approximate theory of temper rolling are not valid. The deformation field consists of a central rigid (actually elastic) zone and is highly non-homogeneous across the thickness of the strip. Longitudinal stress is not uniform across the thickness of the sheet, hence one-dimensional analysis of the process does not seem to be appropriate. Whereas a rigorous analysis is possible using elasto-plastic finite element formulation at the expense of large amount of computational time, a study using rigid-plastic formulation may be used to understand the qualitative effects of process parameters.
Traceability strategy for gear-pitch-measuring instruments: development and calibration of a multiball artifact
There is a strong demand to ensure the traceability of gear-measuring instruments (GMIs). We propose a multiball artifact (MBA) for the evaluation of pitch-measuring accuracy. The aim of the MBA is to transfer the minimum uncertainty from a calibrated value at the National Metrology Institute of Japan (NMIJ) to a measured value of GMIs at a shop floor. The MBA is composed of equally spaced high-accuracy balls around an axis. The pitch-measuring accuracy of GMIs is evaluated by measuring the angular pitch deviation of the balls instead of the angular pitch deviation of a gear. We calibrated the angular pitch deviation using a coordinate measuring instrument (CMM) at the NMIJ and adapting a multiple-orientation technique. We proposed a calibration strategy of the angular pitch deviation. The calibration value of the pitch deviation for the MBA at the NMIJ was obtained with a measurement uncertainty (U95) of 0.2 µm. We evaluated the pitch-measuring accuracy of a GMI using the calibrated MBA. Each value of U95 for the cumulative and single pitch deviations for the left and right flanks was less than or equal to 0.5 µm. The small uncertainty was transferred from the NMIJ to the GMI.