Springback In Air Bending Research Articles

Effect of Die and Punch Geometry on Spring Back in Air Bending of Electrogalvanized CR4 Steel

Effect of Die and Punch Geometry on Spring Back in Air Bending of Electrogalvanized CR4 Steel

Investigation of Spring Back in Air Bending of Electrogalvanized CR4 Steel

Objectives: To analyze the effects of galvanizing thickness and punch speed on spring back of CR4 steel. Methods: Galvanizing is done by electro-deposition method using an alkaline cyanide-free zinc plating system and different thickness of deposition was achieved by changing the time. Galvanizing thickness was measured by coating thickness gauge. Experiments were conducted on a universal testing machine, using various combinations of punch travel, punch speed, and sheet orientation, using the same tooling and size of the specimen. An approach to change one parameter at a time was applied. Measurement of angles was done with the help of graphics and optical profile projector. Spring back was analyzed graphically. Findings: It was observed that spring back increases with the increase of punch travel and punch speed both. With the increase of galvanizing thickness increase of spring back was observed. Application/ Improvements: These results will be useful for design engineers and manufacturing engineers since the use of galvanized steel sheets has increased and the methods of initial bent angle and galvanizing used is as per industry's current practice.

Prediction of springback in air-bending of Advanced High Strength steel (DP780) considering Young׳s modulus variation and with a piecewise hardening function

Advanced High-Strength steels (AHSS) are increasingly used in industry. Thus, the springback prediction in bending of AHSS is important to maintain close geometric tolerances in deformed parts. The unique properties of AHSS: a non-constant Young׳s modulus and a stress–strain relation which does not follow a simple flow stress equation make the prediction of springback very difficult. In this study, an analytical model was developed to predict the springback in air-bending of AHSS, considering the special properties of these materials. A computer code which is developed based on classical bending theory was updated based on the new model. The finite element simulation which includes the properties of the AHSS is also presented in the paper. The comparison between the experimental results and predictions indicates that the detailed consideration of the properties of AHSS affects the accuracy of the springback prediction with the analytical method. It is hoped that this new analysis can be incorporated into the controller of a press brake to adjust the machine for compensating springback during bending.

Sensitivity Analysis of Technical Parameters on Springback in Air Bending of JCO Forming

JCO forming is one of manufacture mode widely used in production of large diameter submerged-arc welding pipes, in which JCO forming process is progressive multi-step air bending. In order to design technical parameters, it is necessary to analysis effects of technical parameters on springback in air bending of JCO forming. So, sensitivity analysis of technical parameters on springback in air bending of JCO forming is carried out using finite element method. Taking the air bending of X80 steel Φ1219mm×22mm×12000mm welding pipe for instance, the air bending is simulated by finite element (FE) code ABAQUS. In this paper, the simulation data is validated by experiments and a comparison showed a good agreement with experiments results. The sensitivity analysis of technical parameters from simulation is discussed. Thus, the results of research provides a basis to design technical parameters.

Effects of Simulation Parameters on Springback in Air Bending of JCO Forming

JCO forming is one of manufacture mode widely used in production of large diameter submerged-arc welding pipes, in which JCO forming process is progressive multi-step air bending. In order to improve JCO forming quality, it is necessary to predict springback of air bending. In this paper, air bending is simulated using finite element method, but simulation parameters directly affected prediction precision. So, taking the air bending of X80 steel Φ1219mm×22mm×12000mm welding pipe for instance, the air bending is simulated by finite element (FE) code ABAQUS. The effects of simulation parameters on springback is discussed. Thus, the results of research provides a basis to improve prediction precision of springback in air bending of JCO forming.

Application of response surface methodology for predicting springback in air bending of electro galvanised steel sheets

Springback in bending affects the geometry of the finished part and it must be predicted in advance to compensate, thus maintaining required tolerances in the finished part. Response surface methodology (RSM)-based models are more useful in industrial applications. Though the researches on application of RSM for other bending processes are available, it is limited in air bending and the attempts are only for uncoated steel sheets. This paper describes the method of developing a prediction model employing RSM and central composite design of experiments that establishes a relationship between springback and the parameters such as strain hardening exponent, coating thickness, die opening, die radius, punch radius, punch travel, and punch velocity in air bending of electro galvanised steel sheet. The results obtained from the model are in good accord with the experimental. Besides, the direct and interaction effect of parameters on springback have been studied based on the developed model.

Prediction for Air-Bending Springback Radius of Sheet Metal Using Back Propagation Neural Network and Micro Genetic Algorithm

Springback radius is a very important factor to influence the quality of sheet metal air-bending forming. Accurate prediction of springback radius is essential for the design of air-bending tools. In this paper, a three-layer back propagation neural network (BPNN), integrated with micro genetic algorithm (MGA), is proposed to solve the problem of springback radius. A micro genetic algorithm is used for minimizing the error between the predictive value and the experimental one. Based on air-bending experiment, the prediction model of springback radius is developed by using the integrated neural network. The results show that more accurate prediction of springback radius can be obtained with the MGA-BPNN model. It can be taken as a valuable tool for air-bending forming of sheet metal.

Influence of Lubrication on Springback in Air Bending Process of Interstitial Free Steel Sheet

This work aims at studying the influence of lubrication on springback in air bending of interstitial free steel sheets with three different orientations namely 0°, 45°, and 90° for the bending analysis. It is observed that lubrication on both punch and die shows the lowest springback compared to the dry conditions. The white grease is more effective in reducing the springback compared to dry and SAE30 oil. A statistical analysis was done to find out appropriate deviation of springback obtained from the experiments and from the material model. It is further noted that the springback exhibited a second-order polynomial relationship with the bend angle.

The Effect of Sheet and Material Properties on Springback in Air Bending

Angle control in air bending is achieved either by exploiting direct angle measurement (adaptive forming) or by controlling punch displacement. In general, the desired angle is supplied as input to CNC press brakes and the choice of punch stroke relies on either analytical or empirical models. Process geometry and material properties affect the outcome, therefore, full knowledge of these values is critical. Since a major source of inaccuracies is due to errors in material description (sheet thickness is critical as well), material data (or, more generally, sheet behavior information) collection in process is advisable. In air bending, process control can be improved by studying the total load as a function of punch displacement. This approach becomes more and more interesting since devices for load measurement are now available on the market. The aim of this work is to analyze some experimental load measures, collected in actual working conditions, to evaluate the accuracy of such technique and its potential for in process applications. Several sheet materials (ferrous and non-ferrous alloys) are studied through both bending and tensile tests; the resulting material properties (tensile and bending) are evaluated and compared. After data treatment of punch force signal, the ability of predicting punch displacement needed to reach a defined bending angle (after springback) is discussed.

Prediction of Bend Allowance and Springback in Air Bending

In the fabrication industry, one of the critical challenges is to maintain close geometric tolerances in finished products, particularly in the air bending process. In many cases, this problem is related to springback and plastic elongation/compression of the sheet, as it undergoes deformation in bending. Springback refers to the elastic recovery of the bent sheet after unloading, whereas bend allowance refers to the elongation of the sheet during bending. Both factors, if not predicted properly, may lead to dimensional inaccuracies in the finished product and cause difficulties in the assembly. Therefore, it is essential to predict springback and bend allowance in order to obtain the final desired geometry. A new analytical model was developed to predict springback and bend allowance simultaneously in air bending, and a user-friendly computer program, BEND (Version 3.0), was developed. Results obtained from the BEND program were compared to other analytical predictions and experimental results available in the literature. It was concluded that the proposed analytical model and the computer program predicted bend allowance and springback within acceptable accuracy.