Conduct Linear Static and Linear Buckling Simulations in Autodesk Inventor4 Feb, 2016 By: Radu Stancescu
IMAGINiT Tricks Tutorial: Autodesk Nastran can help Inventor users make better products using digital prototyping.
Editor's note: This tutorial courtesy of IMAGINiT Technologies.
Linear Static is one of the most common types of analysis. It determines stress, strain, and deformation resulting from applied static loads and imposed constraints. Linear Buckling assesses stability under loads; it examines structures for sudden failure modes caused by compressive forces.
In addition, there are several other types of basic and advanced analysis capabilities in Autodesk Nastran In-CAD software, which we may address in future tutorials.
There is a Nastran panel in the Environment tab in the ribbon, as well as a Nastran browser.
The assembly model shown here is displayed as a level of detail (LOD) of a complex CAD model. Before we simulate the buckling, we may need to perform a linear static analysis.
The Physical option will assign materials to the CAD models. The material can be selected from the extensive Autodesk material library or imported directly from the CAD model; when doing so, the existing Inventor materials are automatically populated in the browser and they are available for use. I’m going to pick the ASTM A36. After defining the material, I need to associate it with the components.
Next, I need to specify the contact between the parts. I can automatically detect all of the surface contact pairs by using the Automatic option. This command detects the contacts based on the CAD geometry. I can also use the Surface Contact Generation (which is the manual way), use Bonded as the contact type, symmetric contact as a Penetration type, and select the surfaces.
I’m using Bonded, so the surfaces move together when loading is applied to the model.
The next step is defining the mesh; I will generate a solid mesh with parabolic tetrahedron elements and a 20-mm size based on the object’s dimensions. All the mesh details are updated in the browser.
Now I will apply the boundary conditions that simulate a real-world scenario. I’m starting with a fixed constraint at the end of the crane, then I have the two holes that are used to lift the model up and down. In order to simulate the bearing, I will add rigid connectors on both sides.
The two connectors can now be used to apply a constraint that allows only rotation; so I will use the Pinned option for that matter.
Finally, I need to add a load to the model in the direction of gravity; so I’m defining a 500N force to lift the model.
I’ve completed the setup for the linear static study, let’s go ahead and run the solver and view the results. Simulation has completed, and the browser updated accordingly. Von Misses plot shows the area with high stress concentration; the maximum value is 114 MPa at the point indicated on the screen.
There is also the principal stress plot (Solid Principal C) for focusing to tension and compression on the model. Let’s have a look at the compression.
The model won’t yield here, but it can cause a buckling failure where the red color is presented on the above picture.
What is buckling? It’s a stiffness-related instability resulting from compression. Buckling may occur in areas where compression causes a loss in stiffness, which can have costly consequences if overlooked. Fortunately, the buckling analysis can be set up right here in Inventor.
The boundary conditions for the linear static study will be reused for the new simulation. I drag the load and constraints to the second subcase created for buckling. After solving the simulation, the software will produce the buckling load factor.
Autodesk Nastran (the solver) calculates the displacements to graphically represent the modal shapes for each eigenvalue extracted. The first eigenvalue is about 54, which is of primary interest. That means the model will buckle at the applied load multiplied by the factor number. Obviously, in this case, the model will fail because of the stress and not the buckling.
This workflow not only saves time and money during the design process, it also ensures a safer product and fewer warranty claims from customers. Autodesk Nastran in Inventor helps to make better products using digital prototyping.
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