Bending Of Metal Sheets Research Articles

Design and Development of a Cost-Effective Automated Metal Sheet Bending Machine

Design and Development of a Cost-Effective Automated Metal Sheet Bending Machine

Research on the laws of transition zone of non-deformation area for 90° V-bending forming process

Purpose“V-bending” is the most commonly used bending process in which the sheet metal is pressed into a “V-shaped” die using a “V-shaped” punch to form a required angular bend. When the punch is removed after the operation, because of elastic recovery, the bent angle varies. This shape discrepancy is known as spring back which causes problems in the assembly of the component in the modern aerospace industry. Regarding the optimization of spring-back accuracy, this research will illustrate the laws of the transition area (TA) of the nondeformation area (NDA) during the 90° “V-shape” bending process.Design/methodology/approachAccording to the traditional “V-bending” process to optimize the spring-back accuracy, the bent sheets are divided into deformation area (DA) and NDA. For this reason, the traditional “V-bending” process may prolong error to optimize the spring-back accuracy because NDA has a certain amount of deformation, which the researcher always avoids. Firstly, bent sheets are divided into three parts in this research: DA, TA and NDA to avoid the distortion error in TA that are not considered in the NDA in traditional theory. Then, the stress and strain in the DA and TA were discussed during theoretical derivation and some hypotheses were proposed. In this research, the interval, position and distortion degree of the TA of the bending sheet are used by finite element analysis. Finally, V-shape bending tests for aluminum alloy at room temperature are used and labeled all the work pieces' TAs to realize the deformation amount in the TA.FindingsThe bending radius does not affect the range of the TA, it only changes the position of TA in the bending sheet. It is evident that the laws of TA were explored in the width direction and gradually changed from the inner layer to the outer layer based on the ratio of width and thickness of the bending plate/sheet.Originality/valueIn the modern aerospace industry, aircraft manufacturing technology must maintain high accuracy. This research has practical value in the 90° “V-shape” bending of metal sheets and the development of its spring-back accuracy.

An Open Source Framework Approach to Support Condition Monitoring and Maintenance

This paper discusses the integration of emergent ICTs, such as the Internet of Things (IoT), the Arrowhead Framework, and the best practices from the area of condition monitoring and maintenance. These technologies are applied, for instance, for roller element bearing fault diagnostics and analysis by simulating faults. The authors first undertook the leading industry standards for condition-based maintenance (CBM), i.e., open system architecture–condition-based maintenance (OSA–CBM) and Machinery Information Management Open System Alliance (MIMOSA), which has been working towards standardizing the integration and interchangeability between systems. In addition, this paper highlights the predictive health monitoring methods that are needed for an effective CBM approach. The monitoring of industrial machines is discussed as well as the necessary details are provided regarding a demonstrator built on a metal sheet bending machine of the Greenbender family. Lastly, the authors discuss the benefits of the integration of the developed prototypes into a service-oriented platform, namely the Arrowhead Framework, which can be instrumental for the remotization of maintenance activities, such as the analysis of various equipment that are geographically distributed, to push forward the grand vision of the servitization of predictive health monitoring methods for large-scale interoperability.

Study on the Free Bending of Metal Sheets Based on the Model of Modified Indices

Study on the Free Bending of Metal Sheets Based on the Model of Modified Indices

Plastic Twisting of Erect Metal Roller

The twisting of an erect round metal roller (beam, roll) has a place in many metallurgical processes. For example, in the rolls of a wide-band mill at rolling of metal slab, in the leading rolls of flattening machines, in the asymmetric three-roll machines at bending of metal sheet, and so on. Under the large external torques in an erect metal roll, the plastic deformations can occur, which lead to the large residual stresses after an unloading of round roll. These residual stresses can bend the axis of the roll or cause it to a collapse under the subsequent loads. To estimate the value of residual stresses, it is necessary to know the spring-back factor of roll at a twisting. In this article, we have obtained the spring-back factor of the erect roll under a twisting.

Determination of the bendability of ductile materials

Understanding fracture in the bending of metal sheet is important but difficult especially for ductile materials were fracture is hard to quantify. New bend tests allow fracture analysis at higher bending strains, however, most of them are impractical for industrial application. This work investigates the link between material failure in bending of brittle and highly ductile materials and local tensile ductility which can be measured in a simple tensile test. For this, a 3-point bend test is developed based on the widely accepted VDA238-100, enabling the fracture of highly ductile aluminium alloys. The failure strain of brittle and ductile aluminium sheets in bending is determined. Uni-axial tensile tests are performed in combination with a digital image correlation (DIC) strain measurement system. Using the surface strain data, obtained from the DIC system during tensile testing and bend testing, a correlation between the local ductility in tensile testing and the fracture strain in bending was identified.

Kriging modelization in predicting metal sheet elongation

AbstractModern industries are increasingly replacing real experiments with non‐stochastic simulation models due to their restrained costs and growing reliability. The non‐stochastic simulator used in this paper is the Finite Element simulation code (FEM), a widely used numerical technique for the engineering problems modeled by a system of partial differential equations defined on a time‐space domain. In such a context, it is common practice to provide a metamodel, a global approximation of the FEM experiment response on the design space to capture local minima/maxima.We use the most popular metamodel, the Kriging model, applied to an industrial instance: prediction of bend deduction. Metal sheet bending is a manufacturing process in which there is a plastic deformation of the workpieces over an axis. This is a metal forming process, similar to other processes where bending changes the shape of the workpieces.The work focuses on the construction of an optimal initial design in order to achieve a good accuracy of the metamodel at an acceptable computational cost, the theoretical study of this model, and the understanding of how it could be conformed to the bend deduction prediction.The correlation structure, mandatory in a Kriging model, was evaluated by means of the variogram, allowing to refine the correlation specification naturally improving the Kriging predictions. The empirical variograms for each input variable brought to light unusual behaviors. This suggested that the bending angle could be related to the bend deduction according to 2 different models. It is clear that there is a discontinuity in the relationship between the models, but its exact location is not known. The accuracy achieved was then evaluated using different indicators of robustness and the uncertainty of the “leave‐one‐out” methods.

Axial crushing of tubes fabricated by metal sheet bending

Energy absorption characteristics of thin-walled tubes fabricated by bending of metal sheets are studied in this work. Square tubes are prepared by folding aluminum alloy 3003 H12 sheets and quasi-static axial crushing tests are then performed with universal material testing machine. The energy absorption capacity and deformation of these folded tubes are analyzed and compared with traditional square tubes. Nonlinear finite element code LS-DYNA is employed to simulate the crushing tests and the numerical results are compared with the experiment. The influences of various factors, including the boundary condition, loading speed, fillet radius and sectional shape, on the crushing force and deformation of the folded tubes are investigated numerically. In addition, folded tubes with multi-cell sections are also analyzed and compared with traditional tubes. Some suggestions are provided for the design of folded single or multi-cell tubes. Since the folded tubes are easily prepared, cost-effective for small-scale production and flexible in both sectional shape and geometric parameters, they are quite promising to be applied widely in various engineering fields.

Numerical and experimental study on multi-pass laser bending of AH36 steel strips

Laser bending is a process of bending of plates, small sized sheets, strips and tubes, in which a moving or stationary laser beam heats the workpiece to achieve the desired curvature due to thermal stresses. Researchers studied the effects of different process parameters related to the laser source, material and workpiece geometry on laser bending of metal sheets. The studies are focused on large sized sheets. The workpiece geometry parameters like sheet thickness, length and width also affect the bend angle considerably. In this work, the effects of width and thickness on multi-pass laser bending of AH36 steel strips were studied experimentally and numerically. Finite element model using ABAQUS® was developed to investigate the size effect on the prediction of the bend angle. Microhardness and flexure tests showed an increase in the flexural strength as well as microhardness in the scanned zone. The microstructures of the bent strips also supported the physical observations.

Aligning Tools on a Press by Means of 3D Scanning

The paper presents the way the 3D scanning was used to correct miss-alignment of the tools on a metal sheet bending press. Parts obtained by bending where not conform to requirements, and the reason was unknown. In order to find the error, the shape, size, and alignment of bending board and stamp had to be checked. The particular very long tools imposed as the single appropriate method of measurement: 3D scanning. The point clouds gathered by 3D scanning were processed to get the 3D models of the tools. Analyzing the models of the tools and their relative position led to conclusions that revealed the error and allowed fixing the problem.

Investigation on V-Bending and Springback of Laminated Steel Sheets

Laminated steel sheet (LSS) is a novel functional material consisting of two steel sheets sandwiched by an adhesive layer. It has good vibration damping and noise absorption attributed by the middle polymer layer, and structural function owed to the two face steel sheets. Springback is an omnipresent negative phenomenon in metal sheet bending. Experiments and simulations were conducted to analyze the effects of processing and material parameters on springback of a specified LSS for the purpose of process optimization. Various tests including lap-shear, normal tensile, and viscosity analysis were carried out to obtain the mechanical behavior of the polymer layer. A neo-Hookean hyperelastic model was accordingly developed. Tensile tests of the two skin sheets were also implemented for material model. Ninety degree V-bending experiments were fulfilled as a validation on the feasibility and efficiency of finite element method and material models. A following parametric study on 88 deg V-bending of the LSS was then implemented to provide a processing optimization for industry practice.

FEM analysis for laser bending process of DP980 steel sheet

Laser bending of metal sheet is a complex process that is achieved by introducing thermal stress into a metal sheet through irradiation using a defocused laser beam. In a single scanning process, it is important to know the effects of the engineering parameters on the final bending angle, such as the laser power, laser beam diameter, and scanning speed. Furthermore, it is important to investigate the effect of the scanning direction in a multiple scanning process. In this paper, FEM analyses for a laser bending process of DP980 high strength steel sheet under different laser powers, scanning speeds, line energies, and scanning directions are performed to analyze the effects of the engineering parameters and the scanning direction on the final bending angle. The results indicate that the final bending angle of a DP980 steel sheet increases in a linear increase fashion with the increase of the line energy in the single scanning process; it also increases when the scanning direction is changed time by time in the multiple scanning process.

Improved knowledge-based neural network (KBNN) model for predicting spring-back angles in metal sheet bending

We develop an efficiently improved knowledge-based neural network (KBNN) associated with optimization algorithms and finite element analysis (FEA) to accurately predict spring-back angles in metal sheet bending. The well-known V and U prevalent processes of bending are considered. The KBNN predictive results are based on the empirical model and artificial neural network (ANN) modeling. The empirical model is constructed from the FEA results using response surface method, while the multilayer perceptron is employed to create the ANN. The trained KBNN can accurately model the relationship between the spring-back angles and process parameters. The obtained results are validated against other existing methods showing a high accuracy.

Analytical Approach of Springback of Arced Thin Plates Bending

In practical production, metal sheet bending process contains multiple steps of bending to meet the requirements of the shape and quality. The arced thin plate with pre-strain is taken as the subject to investigate the subsequent bending and spring-back. Based on linear combined hardening constitutive model, the analytical method of the arced thin plate with pre-strain bending forming and springback is researched. The tangential strain on the cross section of the arced thin plate during bending is analysed, and then analytic formulas of material hardening in the circumstance of the positive and reverse loading are deduced. Distributions of stress and strain in subsequent bending and corresponding bending moment formulas are deduced. The central angle and radius of curvature after springback are obtained. The accuracy of the analytical model is verified by FEM cases. In addition, the established model is applied to the UOE forming process and the results show that the analytical approach presented in the paper are feasible and of good precision.

Control System Algorithm for the Prediction of Sprinback in Air Bending

The phenomenon of springback, which is ruled by strain recovery after removal of forming loads, is of remarkable interest in air bending of metal sheets. In this process, the final angle is affected by a number of parameters related to both process geometry (sheet thickness, die and punch radii) and material properties (elastoplastic stress-strain law); because of this, punch stroke has to be calculated in a nontrivial way and a number of input parameters should be taken into account. In this work the study of total load as a function of displacement is used to collect information about material stress-strain law; using this approach, load data may be exploited to fine tune the mathematical description of the material and, finally, to improve springback prediction. A customized press brake able to measure both displacement and force during bending was fabricated for this purpose. The press brake is equipped with a control system algorithm able to collect material information directly during the initial stage of the bending process. These collected data are used to feed a model based on a FEM simulation and the model output is the final punch displacement suitable to obtained a specific bending angle after unloading. The program utilized for the simulation is Deform 2D. Preliminary tests were executed on metal sheets having different thickness.

Identification of material hardening parameters by three-point bending of metal sheets

Calibration of hardening and partly viscoplastic parameters of the previously published material model was the primary concern of this paper. The method used for identification of the material hardening parameters for metals, the three-point cyclic bending of sheets, constitutes a basis for this work. Plastic hardening parameters were determined by comparing load–displacement curves from FE simulations with those from the tests. Since viscoplasticity is assumed, stress–strain curves from uniaxial tension tests at selected strain rates for strain-rate sensitive materials were employed to calibrate corresponding viscoplastic parameters. The optimization problems are solved by means of a commercial optimization code, LS-OPT, using a response surface methodology. The objective is to minimize (by the least-squares method) the sum of the differences between measured and simulated loads. The material parameters were identified for two high-strength steel alloys (ZSte340 and DP600, strain-rate sensitive materials), and one aluminium alloy (AA5182).

On the cold bending ability of metal sheets and plates

The determination of minimum bending radii is still an unsolved problem. Recently an attempt was made to relate the minimum bending radius of a metal sheet to its local instability in bending, based on purely theoretical considerations. It is shown that this approach yields erratic results. An experimental method is described for the direct determination of the instability limit in pure bending, i.e. in bending with a pure moment, without the action of a transverse load exerted by a punch or forming block. In the experimental investigation of a large number of specimens, good correlation has been found between the limiting curvature in pure bending and the reduction of area in simple tension. This empirical relationship is in an excellent agreement with a simple deformational theory. Another good correlation has been found between the limiting curvature in bending and the notch impact value of the same material. The statistical results obtained may be used to assess the deformability in cold bending of metal sheets and plates and to select, in a more rational way, the minimum bending radius for a particular bending operation. In many cases, in fact, it would be wrong practice to identify the technologically attainable minimum bending radius with the safe radius of a reliable construction component, where the latter is subjected to heavy dynamic loads at low temperatures.