Research on an external adjustment method for RPECT roll profiles based on the segmented cooling principle

Roll profile electromagnetic control technology (RPECT) is a new strip flatness control technology that changes roll gap shape by controlling the roll profiles of electromagnetic control rolls (ECRs). To address the randomness of the flatness defect locations, this paper proposes an external adjustment method for RPECT roll profiles based on the segmented cooling principle. Based on the layout of the cooling areas and electromagnetic sticks, an electromagnetic-thermal-structural coupled model is established to analyse roll profile variations. The results show that symmetrically changing the cooling intensities of the different cooling areas can increase or decrease the roll crown of the ECR, while asymmetrically changing the cooling intensities of the different cooling areas can change the position of the maximum bulging point of the ECR. Variations in the component cooling ratio coefficient impact the effects of different cooling strategies, which needs to be considered when selecting the cooling strategy configuration scheme. Compared the maximum bulging values, radial temperature gradients and axial temperature gradients of different electromagnetic stick (ES) structures, the regulation law reverses when the length of the ES is too small, and the variation of the law is very small. Therefore, different ES structures have different segmented cooling regulation characteristics.

Simulation and Control of High-Order Flatness in Rolling Wide Titanium Strip With 20-High Mill

In wide titanium strip cold rolling process, the high-order flatness defect is one of the most difficult problem to be solved. Based on finite element method, considering the anisotropic mechanical characteristics of titanium, an implicit integration calculation model of rolls-strip for 20-high mill was developed, which can simulate the dynamic rolling process. The model was used to analyze the adjustment characteristics of high-order flatness on the 20-high mill. The simulation revealed as the increasing of the 1# & 7# AS-U or 2# & 6# AS-U press adjustment, the high-order flatness defect was more aggravated; And as the increasing of 3# & 5# AS-U or 4# AS-U press adjustment, the high-order flatness defect was alleviated to some extent. In addition, the high-order flatness cannot be effectively adjusted by roll shifting. Finally, the industrial test showed that increasing 4# AS-U press adjustment can effectively relieve the high-order flatness defect.

Research on work roll contour for improving the flatness defect of electronic aluminum foil

Electronic aluminum foil strip has extremely large width-thickness ratio, and often emerges tight-edge and rib-wave defect after rolling. In order to improve the special flatness defect, the defect distribution characteristics, section profile of aluminum foil strip and defect cause are analyzed, and then a new work roll contour is designed based on the idea of partial variable diameter. The new contour curve is a combination of multiple curves and the influence of various curve parameters on the contour is researched. A finite element simulation model based on ABAQUS is established to study the control characteristics of flatness defect when using the new work roll. The simulation results and actual production data of the 1450 aluminum foil rolling mill show that the new work roll can increase the depression of tight-edge area and improve the flatness defect of tight-edge and rib-wave.

Self-supervised pre-training of CNNs for flatness defect classification in the steelworks industry

Classification of surface defects in the steelworks industry plays a significant role in guaranteeing the quality of the products. From an industrial point of view, a serious concern is represented by the hot-rolled products shape defects and particularly those concerning the strip flatness. Flatness defects are typically divided into four sub-classes depending on which part of the strip is affected and the corresponding shape. In the context of this research, the primary objective is evaluating the improvements of exploiting the self-supervised learning paradigm for defects classification, taking advantage of unlabelled, real, steel strip flatness maps. Different pre-training methods are compared, as well as architectures, taking advantage of well-established neural subnetworks, such as Residual and Inception modules. A systematic approach in evaluating the different performances guarantees a formal verification of the self-supervised pre-training paradigms evaluated hereafter. In particular, pre-training neural networks with the EgoMotion meta-algorithm shows classification improvements over the AutoEncoder technique, which in turn is better performing than a Glorot weight initialization.

Assessment of geometrical defects caused by thermal distortions in laser-beam-melting additive manufacturing: a simulation approach

Purpose The purpose of this paper is to develop a numerical approach inspired by Geometrical Product Specifications (GPS) standards for the assessment of geometrical defects appearing during Additive Manufacturing (AM) by Laser Beam Melting (LBM). Design/methodology/approach The study is based on finite element (FE) simulations of thermal distortions, then an assessment of flatness defects (warping induced by the high-residual stresses appearing during the manufacturing) from the deformed surfaces provided by simulation, and finally the correction of the calculated flatness defects from preliminary comparison between simulated and experimental data. Findings For an elementary geometrical feature (a wall), it was possible to identify the variation in the flatness defect as a function of the dimensions. For a complex geometry exhibiting a significant flatness defect, it was possible to improve the geometric quality using the numerical tool. Research limitations/implications To the best of the author’s knowledge, this work is the first attempt using a numerical approach inspired by GPS standards to identify variations in thermal distortions caused by LBM, which is an initial step toward optimization. This paper is mainly focused on flatness defect assessment, even though the approach is potentially applicable for all types of geometrical defects (shape, orientation or position defects). Practical implications The study opens prospects for the optimization of complex parts elaborated using LBM, based on the minimization of the geometric defects caused by thermal distortions. Social implications The prospects in terms of shape optimization will extend the potential to benefit from the new possibilities offered by LBM additive manufacturing. Originality/value Unlike the usual approach, the proposed methodology does not require any artifacts or comparisons with the computer-aided-design (CAD) model for geometrical distortion assessment. The present approach opens up the possibility of performing metrology from FE simulation results, which is particularly promising in the AM field.

Influence of the probing definition on the flatness measurement

The quality control of mechanical parts is generally performed on a coordinate measuring machine (CMM). The choice of the number of points to be sampled, their distributions and their positions on the surface, as well as the association criterion remains unresolved. This paper studies the variation of the flatness defect with regard to the number of palpated points. The methodology begins by sampling a cloud of points on a CMM. Then, a modal analysis study is carried out in order to generate a modal surfaces (digitally deformed). Insertion of the coordinate cloud points of these modal surfaces in the GEOVERIF software will allow estimation of the flatness defect. The results of the measured flatness by the three fitting criteria (minimum zone, least squares and minimum volume) are compared.