Forming Simulation

[Jodee Bouman]

Inmetal forming simulation, the forming of sheet metal is simulated on the computer with the help of special software. Simulation makes it possible to detect errors and problems, such as wrinkles or splits in parts, on the computer at an early stage in forming. In this way, it is not necessary to produce real tools to run practical tests. Forming simulation has become established in the automotive industry since it is used to develop and optimize every sheet metal part.

To illustrate the metal forming process, there must be a model of the real process. This is calculated in the software using the finite element method based on implicit or explicit incremental techniques. The parameters of the model must describe the real process as accurately as possible so that the results of the simulation are realistic.

The typical parameters for forming simulation are, for example, part and tool geometry, material properties, press forces and friction. The simulation calculates stresses and strains during the forming process. In addition, simulations allow for the recognition of errors and problems (e.g. wrinkles or splits) as well as results (e.g. strength and material thinning). Even springback, the elastic behavior of material after forming, can be predicted in advance. Forming simulation also provides valuable information about the influence of process variations on stamping robustness.

Forming simulations are used throughout the entire process chain of sheet metal forming. The simulation allows a part designer to estimate the formability of a sheet metal part already during the design phase, which results in the design of a part which is easy to produce. A process engineer can already assess the process during the planning phase and optimize various alternatives using the simulation, which can subsequently reduce the fine tuning of a forming tool. Finally, regarding the fine tuning of a forming tool, simulation can provide useful information on how an existing, not yet fully functioning tool must be adjusted. It is also possible to see how the process parameters must be adjusted in order to guarantee optimal drawing results.

Metal forming simulation enables the fast review of several alternative concepts for quality and cost improvements, which results in huge cost and time savings. Furthermore, simulating the forming process improves development and planning reliability. The number of tool tryouts is reduced and tryout time is shortened. Metal forming simulation leads to the highest quality in part and tool design as well as maximum reliability in production.

Inspire Form is a complete stamping simulation environment that can effectively be used by product designers and process engineers to optimize designs, simulate robust manufacturing and reduce material costs.

With the fast and easy feasibility module, users can analyze parts in seconds to predict formability early in the product development cycle. The automated blank nesting proposes an efficient layout of the flattened blank on the sheet coil to maximize material utilization.

The tryout module includes a highly scalable incremental solver, helping users to iterate and simulate multi-stage forming, trimming and springback in a modern and intuitive user interface, reducing complexity and making the production of high quality parts more economical.

Inspire Form enables users to quickly and reliably check the formability of apart early in the product design cycle. With Inspire Form, users can visualize potential defects such as splits or wrinkles, and then modify to eliminate defects and improve overall design.

Inspire Form has a simple and highly intuitive workflow that is easy to learn and apply. Standard training sessions last only 4-6 hours, although most users can learn Inspire Form applications with no formal training at all.

Die Engineering Pty Ltd, a regular StampingSimulation customer, needed to be sure that a part of a complex project could be formed successfully. Earlier prototype parts had been made with unacceptable wrinkles and it was, therefore, the job of our simulation team to determine how to make this part in a way that prevented any wrinkling.

Hi Everyone. I am busy testing Nastran In-Cad and have been working through a few tutorials. I have completed the tutorial labeled "metal forming simulation using nonlinear material and contact". Everything seems fine and behaves as expected but the simulation ends with the punch and die in the closed position. Is it possible to open the forming tool to see what the formed part would like, factoring in "spring back".

Welcome to the Nastran In-CAD forum! It's not possible to run the analysis in reverse, a non-linear static solution can only have a linear ramp for a load curve. So we can get to a maximum but then not decrease back to zero. You could switch the analysis type to Non-linear Transient and you could define a time dependent load curve for the loads. Use the following steps to give this a try:

This should cover converting it to a time-dependent solution, although I haven't run the model myself. You can always look at the plastic or permanent strain induced however by looking at SOLID EFFECTIVE STRAIN-PLASTIC/NONLINEAR ELASTIC. Before a model enters permanent deformation it will show the elastic strain, once one element converts to plastic strain by exceeding the yield stress the result vector will reset and show only the plastic strain.

Ah yes that is correct, I forgot that enforced displacements were used in that tutorial. What you can do is capture the force required to push the die during the non-linear static analysis. To do this, right-click on the constraint for the bottom of the die in the model tree and select SPC summation. Then write down the force for a few times over the course of the analysis to create a load curve. I think the load curve will end up more or less linear.

Now in the non-linear transient analysis create a force instead of enforced motion. Once you get to 100% load (1second), change the load scale factor to negative values to get the die to move in the negative direction. This should then allow you to model the die stamping the piece and the die retracting. Leaving you with a formed metal piece, I expected it will retain the shape it was stamped into as it us undergoing a large amount of plastic (permanent) deformation.

Hi Andrew. I did try it yesterday but was unsuccessful. The solver ran for a few hours which seemed excessive and then failed. I have no idea why. I have decided to try again but using a different model, one that is closer to my goal.

I had a chance to work on your model some more today and got a result that I think you'll be pleased with. Attached is an assembly file that you can place in your directory with the part files and it should run OK. Please look at the second analysis in the file. In this I've created a second sub-case with a dummy temperature load (a load is required by the interface) to allow for the open and closing of the die. The results looked pretty good to me! Let me know if you have any questions.

" It's not possible to run the analysis in reverse, a non-linear static solution can only have a linear ramp for a load curve. So we can get to a maximum but then not decrease back to zero. You could switch the analysis type to Non-linear Transient and you could define a time dependent load curve for the loads."

I will try to explain what Andrew meant. If you open up the dialog box for Load in nonlinear static analysis, you will notice that you do not have a way to input the load as a time variant i.e. F(t) using table. Instead you enter the final load value. With nonlinear static analysis, the load is applied in a "ramp" form. For example, if you apply a load of 1N, a portion of the load is applies at each time step, until 100% of the load is applied by the end of the analysis. You will see "OUTPUT SET: INCR x, Load=y" in the bottom left of the work area when nonlinear analysis is run, where "x" and "y" represent the increment number and proportion of the load applied, respectively.

So if you want to model releasing of a load (i.e. unloading) in nonlinear analysis, you need to add a second subcase study with that load removed. The analysis will then gradually remove the load in a ramp form in that subcase study. The only problem is, you need a load defined in a study or the analysis will not run and you will get the message "No load exists within a subcase". To get around this issue, Andrew applied dummy thermal load, allowing the "force" load to decrease to zero.

Create reliable and accurate virtual manufacturing realities with a wide range of simulation software, including metal forming, assembly & joining, and additive manufacturing, aiming at optimising manufacturing processes during design.

Cost Engineering

Define target costs early in the design phase through a realistic stamping cost engineering analysis. Manufacturers and engineers can effectively derive should-cost scenarios, improve overall material utilisation, and reduce vehicle weight and tooling development time.

Process Planning / Technical Planning

Develop a detailed process plan for quoting & estimating from your 3D CAD (Computer Aided Design) design. Generate realistic images for each die operation. This scientific and data-driven approach empowers cost and design engineers to derive fast and accurate quoting and estimating processes and technical planning.

Virtual Process Validation

Perform quick virtual try-outs of stamping and assembly processes and identify issues before tooling kick-off to reduce costs and time-to-market while improving product quality. The 3D explicit incremental analysis provides a complete virtual die development and try-out for tool and die makers.

Be it forging, rolling, extrusion or other methods, bulk forming is an indispensable production technology that many products rely on. Given the influence of temperature, material flow and permanent deformation, our advanced simulation is necessary to effectively establish and control the process effectively.

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