A Versatile Punch Stroke Correction Model for Trial V-Bending of Sheet Metals Based on Data-Driven Method

During air bending of sheet metals, the correction of punch stroke for springback control is always implemented through repeated trial bending until achieving the forming accuracy of bending parts. In this study, a modelling method for correction of punch stroke is presented for guiding trial bending based on a data-driven technique. Firstly, the big data for the model are mainly generated from a large number of finite element simulations, considering many variables, e.g., material parameters, dimensions of V-dies and blanks, and processing parameters. Based on the big data, two punch stroke correction models are developed via neural network and dimensional analysis, respectively. The analytic comparison shows that the neural network model is more suitable for guiding trial bending of sheet metals than the dimensional analysis model, which has mechanical significance. The actual trial bending tests prove that the neural-network-based punch stroke correction model presents great versatility and accuracy in the guidance of trial bending, leading to a reduction in the number of trial bends and an improvement in the production efficiency of air bending.

Analytic Model for Multi-point Large-Radius Bending of Steel Sheets

While the majority of industrial sheet bending processes consist of conventional air bending, more complex bending processes such as multi-point bending are also utilized. Multi-point bending involves forming several bends simultaneously with changing contact conditions. Of the various models that may be employed to simulate such processes, analytic models are most attractive for industrial applications as they are time-efficient, strongly theoretically supported and easily extended to a wide range of dies layouts without the need of additional experimental data. In this paper a new analytic model is presented to predict the forming forces, the deformation of the sheet and the springback. The model is based on the literature around large-radius air bending. The geometry of the sheet is determined at each moment as a function of the tool’s positions. The reaction forces are calculated based on the equilibrium of forces and moments and the springback is calculated based on the elastic unloading of the internal bending forces. The model has been compared with a more time consuming finite element (FE) model and the geometry of the sheet has been experimentally verified by means of digital processing of video images. The proposed analytic model shows good agreement with the computational FE model and it is demonstrated to be a robust tool for calculation of the bending characteristics.

Strain distribution during air bending of ultra-high strength steels

Air bending is a widely used method for forming ultra-high strength steels (UHSS). However, the limited formability of UHSS poses some challenges for the bending process in the form of strain localisation, surface defects, punch detachment (multi-breakage) and pseudo-polygonal “nut-like” shape of the bend. In this study, the bendability of three UHSS grades (700, 900 and 1100 MPa) is investigated with 3-point bending tests, utilising Digital Image Correlation (DIC) for measuring the strain distributions on the outer curvature. The differences in the extent of multi-breakage and the bend shapes are also studied, and these observations are correlated with the findings from the bending force and strain measurements. The differences between the investigated UHSS grades are significant. The 900 MPa grade produces more localised strain distributions and pronounced multi-breakage compared to the other grades, along with a more polygonal “nut-like” geometry. The reasons and effects of the multi-breakage phenomenon, as well as the causes for the observed differences in the behaviour of the materials are discussed in this paper. The presented results and the measurement data provide more information about the behaviour of the investigated materials in bending, and can be used for improving bending simulation, numerical models, and workshop instructions.

RANCANG BANGUN PRESS TOOL UNTUK ALAT BENDING PELAT TIPE DIE-V AIR BENDING

Pekerjaan pembentukan logam (metal forming) pada industri permesinan maupun pabrikasi las saat ini sangat banyak permintaan khususnya pada pekerjaan yang memerlukan proses bending. Proses bending merupakan pembentukan logam yang umumnya menggunakan lembaran pelat atau batang, baik dari bahan logam ferro maupun logam non ferro dengan cara ditekuk, yang mana dalam proses pembengkokan akan menyebabkan terjadinya pemuluran atau peregangan pada sumbu bidang netral sepanjang daerah bendingan dan menghasilkan garis bending yang lurus. Penggunaan teknologi tepat guna telah banyak digunakan untuk meningkatkan produktivitas, efisiensi, dan efektivitas dalam proses produksi pada industri permesinan maupun pabrikasi las berskala kecil dan menengah. Salah satu teknologi tepat guna yang memungkinkan diterapkan dalam proses produksi khususnya pekerjaan bending pelat yaitu mesin atau alat press bearing dengan cara menambahkan dengan press tool yang dilengkapi punch dan die penekuk. Press tool adalah salah satu jenis alat bantu pembentukan, pemotongan dan penekukan produk dari bahan dasar lembaran pelat yang operasinya menggunakan mesin press. Dari penelitian telah diciptakan press tool yang dilengkapi punch penekuk dan die berbentuk V air bending. Adapun spesifikasi press tool ini yaitu: sudut punch sama dengan 85o, radius punch sama dengan 1.5 mm, panjang punch sama dengan 300 mm, sudut die sama dengan 85o, lebar bukaan die sama dengan 33 mm, jarak langkah sama dengan 19 mm.