Papers by Keyword: Air Bending

Abstract: High springback and limited forming limits of modern high strength steels are a big challenge in manufacturing engineering. Both aspects are crucial in sheet metal bending processes. Different modifications of the air bending process have already been developed in order to reduce springback and also to increase the forming limits of materials. The innovative process of incremental stress superposition on air bending, developed at the IUL, is an alternative to conventional processes. Studies of this new process alternative show a positive effect on the considerable reduction of the sheet metal springback and extension of forming limits. Using the principle of incremental stress superposition leads to several advantages compared to conventional bending processes like die bending, bending with an elastomer tool, or three point bending. The bending force and, therefore, the consumed energy during air bending with incremental stress superposition are much lower. This paper presents the new process alternative and shows the latest investigation results.

Abstract: Bump bending or step bending is a forming technique that allows making large radius bends in a sheet metal part by means of a series of bends performed close to each other. The bump bending process has been studied by means of both an experimental campaign and finite element analysis. High-strength steel Weldox 1300 and a punch of radius 30 mm have been used. The finite element calculations have been performed with Abaqus using the solid formulation and Implicit/Explicit solvers. The results of the finite element analysis have been validated experimentally by monitoring the bending process using a camera system aligned with the bending line. Experiments were performed on a press-brake with a capacity of 50 metric tons. Deflections of a sheet during and after bending have been measured using the images recorded by the camera. In order to investigate the influence of a new bend on a previously formed bend, experiments have been performed with different distances between two consecutive bends. Based on the experiments, the size of the affected zone for the bend has been measured. The dependence of the distance between two consecutive bends on the resulting global bending angle has been studied. Moreover the influence of the bump distance on the springback has been investigated.

Abstract: Springback and limited forming limits of modern high strength steels are a big challenge in manufacturing engineering. Both aspects are crucial in sheet metal bending processes. Different modifications of the air bending process have already been developed in order to reduce springback and also to increase the forming limits of materials. A new method (the incremental stress superposition on air bending) has been developed. Studies of this new process alternative show a positive effect on the springback behavior. In order to investigate the potential of this process a comparison with other already established bending processes have been carried out. A possible process control to extend the forming limits has also been investigated.

Abstract: 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.

Abstract: 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.

Abstract: 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 analysis deformation characteristic of air bending. So, air bending is analyzed 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 stress/strain from simulation is discussed. Thus, the results of research provides a basis to improve JCO forming quality.

Abstract: Bending is a commonly used forming technology in metal forming. The occurring springback and low forming limits of high-strength steels especially during air bending are the main disadvantages. In this paper, the conventional air bending process is applied with a hydrostatic pressure in the bending zone. This was done using an elastomer tool. The advantage of this method is that the flexibility of air bending is maintained by reducing the springback while the forming limits are extended. Furthermore, different geometries for the elastomer tool were investigated by means of a FEM simulation. The investigation leads to a reduction of the process forces by minimizing the springback and to an extension of the forming limits.

Abstract: In this work, the multi-breakage effect has been studied by means of an experimental campaign and finite element analysis. We suggest that large radius bending (XL-bending) consists of three phases that are distinguishable according to the type of contact of the plate with the tool: 1-point, surface and 2-points. In the experimental investigation the high-strength steel Weldox 1300 and a 40 mm radius punch were used. The authors created a camera setup to film the multi-breakage effect. Additionally, finite-element calculations were performed to confirm the hypothesis of the three phases of the bending process. For the springback and the bending force evaluation, the difference in the moment distribution for each phase has been calculated in the case of a beam. It shows that the multi-breakage effect must be taken into account to obtain a good accuracy for the springback and the bending force calculation.

Abstract: Springback is a common phenomenon in air bending of sheet metal forming, caused by the elastic redistribution of the internal stresses during unloading. It has been recognized that springback is essential for the design of the air bending. Traditionally, the values of springback is obtained for air bending parameters from handbook tables or springback graphs. However, the handbook tables or springback graphs are obtained using experiments and it is a time consuming processes. In this paper, a finite element model has been used to analyze the air bending process. Some experiments are carried out on ST12 materials, and the finite element model is validated comparing with experiments. In the present research the influence of process variables such as punch radius, die radius and die on springback are discussed using finite element analysis. Thus, the presented results of this research provide a basis of design to improve forming quality.

Abstract: The sheet metal bending is one of the metal forming processes with the simplest geometric interpretation and usually a 2D analysis is considered. The bend over a sheet metal blank consists of a V shape forming by using a punch, with a certain nose radius, forcing the plate against an open die, with a V section. The forming result is a part with an angle obtained between the V legs, flanges, which is known as bending angle. The operation to get the required V angle is called air bending, or free bending. The most common used machines for this forming process are press brakes, special long presses, where the tools, punch and die, are attached to. With the spread use of CNC machines, and their computer control capabilities, most of them using graphical user interface (GUI), became important to get the required shape at first trial. Beyond the required bending angle obtained with just one hit, it is also important to position the gauge system in order to get the successive flange lengths to complete the programmed shape. The main variables controlled by the CNC are the punch penetration inside the die and the position of the back gauge, which is determined by the bend allowance. However this penetration is not the only responsible for the resulting bending angle and the gauging position is not the only responsible for the flange length. Additionally, the radius inside the V shape edge, known as bending radius, influences the geometry and correspondingly the bend allowance. Some authors believe that the punch nose radius has direct influence, both in the bending angle and bend allowance. In this paper, results are presented describing the use of finite element analysis as an aid in the prediction of the inside bending radius, that influences both punch penetration for the final bending angle and the bend allowance for the final flange length. From the air bending analysis, a natural inside bending radius is presented as an important variable in these kind of processes, as well as its minor dependence on the punch nose radius.