Simulations play an important role in the metal fabrication industry. They can help you understand and perform a requirement analysis whether you are working laser cutting or metal rolling. This article discusses the use of simulations in metal bending processes.
Bending a tube or any other workpiece for that matter results in a multitude of changes to it. Firstly, when a workpiece is bent, the inner region becomes thicker while the outer region becomes thinner. Additionally, there are even possibilities of wrinkles in the workpiece. In some cases, the properties of the material change too due to work hardening. There are some tried and tested methods you can employ to simulate the bending process:
- Modeling the bent tube as a homogeneous tube: This method involves modeling the tube and ignoring all of the changes mentioned above that the tube might go through. This modeling technique is perfect for tubes that are heat treated after bending and tubes that are bent in small angles.
- Modeling the bent tube by only considering any flattening and changes in wall thickness: This required extra work due to extra measurements and data collection. This is especially useful in cases when wrinkles in the structure of the tube are not expected and the tube is heat treated after bending.
- Finite Element Method: This is the method used for studying the behavior of the material.
Behavioral and conditional assumptions
In most FEM process simulations, the deformation of the machine and tools used during the processes are mostly ignored, save for some exceptional cases. However, the reality of it is different. Moreover, the conditions the hydraulic system and the high-pressure systems are often ignored and just assumed that the specified pressures and trajectories will be perfectly applied. However, there have been changes. A significant step forward has been the use of the “fluid cell” option that is now being integrated into various FEM programs. This allows for monitoring changes in pressure as the volume of the part changes and the rate of flow of the liquid changes.
Hydroforming simulation techniques make another assumption. That is, sealing surfaces are always leak proof. However, this is not always true. The part may be uneven sometimes due to plastic deformation. This problem can be dealt with by providing the simulation with displacement boundary conditions to check the respective axial forces.
Simulations, like FEM simulations, help plan ahead when dealing with parts and figuring out the different nuances. However, because the different software is used for the simulation of metal forming process and another for structural analytics and calculations of either single hydroformed parts or a combination of parts. The transfer of data between the two software results in loss and errors.
There are still some areas that need more research and development in the field of hydroforming simulations. There is some work being done with other necessary simulation aspects such as those dealing with the material flow in addition to using the deformation capacity of a particular material used in hydroforming processes. In order to get a full grasp on hydroforming, matching experimental and calculated values is essential in incremental stages of the metal forming process.