Simulating Welds & Bolted Connections/ANSYS TUT

Basic Set-up: Disclaimer (If you know how to set up welds already, you can skip to simulations!)

• A sketch of the structure can be made to provide a mould/shape of the final result, with the use of the Structural Member tool on Solidworks; you can transform sketch lines into differing-sized shapes & tubes

  • Some tips: While setting up, sketches make use of planes and 3D sketches to align joints to perfection, this will make the step mentioned above significantly easier to do.

• Structural Member Breakdown:

  • Once sketches have been finalized and set up, you can proceed to create your members.

  • Standard, Type, and sizes can be selected from the menu.

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  • Groups can be made through basic interactions with standard geometry (squares, triangles etc), or you could opt to have multiple stand-alone groups.

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• After this your corners (Joints) can be treated, to make it as aesthetic and clean-looking as possible, and to later help your sim.

  • A higher trim order may be necessary based on the number of objects intersecting at a corner. For the example set-up in the image 4 objects are intersecting at a corner, so the max trim order was used for all groups to refine the edge. Select the pink circle on your joins to apply the corner treatment.

SIMULATIONS OF WELDMENTS

• To begin sims, you need to set up, Weld Beads, the actual joints for the different materials

• The Weld Bead menu:

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  • A Weld Path or Weld Geometry may be used to model the weld, that is needed.

    • Weld Geometry:

      • In this case, a face is selected and the intersecting tube is used as the second face, this is a basic setup for a welded joint. The welding symbol can also be defined, for both faces, it is recommended that a fillet is used, as it is an easier identifier for a weld.

    • Weld Path:

      • This is as easy as it sounds, you’re simply creating a path to indicate where the welds should be made. As long as you've set your default radius.

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      • Once you’re done with this process and making the weld beads, simulations may begin

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        • Also, all welds will be in the Weld Folder

        • By right-clicking on the weld folder you can hide and unhide the cosmetic weldments.

Simulations:

• Start a new study; the static study will be your best friend

• Apply your fixtures, not on the welds, but the stationary segments of your design.

• Apply your forces, in the case of my example they would be beams, you could also apply the individual forces to the joints as well

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• Solidworks recognizes your weld beads as secure welds and the sim is run accordingly

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This has been the easiest way, I’ve found to simulate weld behaviour, as weld beads hold far too much customizability, with the capacity to simulate and run every type of weld.

Method 2: Directly from the Simulations tab

For assemblies, where the aforementioned steps have not been mentioned, it is quite simple to also use the Edge weld connector method or Spot Weld features in the FEA menu, directly from the simulation → new study → connections → right click → Edge weld.

This option allows for direct treatment of the edge of 2 intersecting objects

Limitations: Weldments have many benefits in their ability to simulate and construct basic layouts for welds easily, yet are quite limited in overall depth compared to other software.

• The complexity of Joints: You can currently only make 3 types of joints on SolidWorks, Miter, EndButt, and Endbutt 2 this grossly limits the ability to represent more complex joints and non-standard conventions, which would require external detailing and sketching to achieve.

• Limited Simulation: Overall simulation capabilities; the SolidWorks simulation capacity for advanced weldments is comparable to the underdeveloped muscular system of a little brother. The older brothers being ANSYS/Abaqus, SolidWorks fails when trying to simulate the behaviour of welded structures undergoing complex loads, this includes but is not limited to fatigue analysis, all of which would require software or manual calculations. [Stress]

• Customization/Cutlist Issues: SolidWorks offers a variety of standard weldment profiles, and also a unique method of storing the customizations in the form of a cutlist. Management of this form of data storage is also quite challenging, and for unique and non-standard cross-sections, it becomes more challenging and complex.

• Non-linear Analysis: The analysis of the behaviour of weldments under large deformations and non-linear material properties, FEA and simulations may be limited as well.

  • An example of this would be:

    • If we were analyzing a welded beam that was gradually undergoing increasing load, the point in which the load force surpasses the yield point of the material, plastic deformation occurs; significantly decreasing the stiffness of the material. SolidWorks FEA would not accurately model this behaviour, which would lead to the misestimation of stresses and incorrect deformation predictions.

      • This would be a situation in which ANSYS would be better.

• When you finish the installation of ANSYS Student, you will have a zipped file, I have WINRAR to help extract zipped files.

• Extract all zipped files to your downloads folder, and you can move them elsewhere

• Open the folder, click set-up, follow the instructions and install ANSYS.

• Now you have ANSYS

The first step is to import your geometry into Workbench, once you’ve installed ANSYS, you’ll gain access to a plethora of resources.

• In WorkBench → Drag Static Structural → (Make Changes to the structural property that you need) → Right Click geometry → (For Solidworks, .prt, .asm files are not acceptable, export your parts as .stl files.) → Then import and view your part on Space Claim. You can also visit (Importing and exporting ) to see acceptable file types.

We can now move to ANSYS Mechanical. Double-click Model in the Workbench interface to enter the workspace.

Creating A Mesh:

A mesh is made up of nodes in space that represent the shape of the geometry. Meshing turns our irregular shapes into smaller more recognizable volumes named “elements.”

• The beauty of ANSYS is its ability to Mesh selectively at a deeper level, Not everything needs to be meshed

• The relationship between 2 or more parts in your geometry needs to be defined and accurately described.

  • If nodes are shared between common faces (or edges), you need to decide between conformality and nonconformity with your mesh.

    • a conformal mesh ensures that the nodes on both sides of the interface match. With a non-conformal mesh, the nodes on one side of the interface do not match the nodes on the other side of the interface.

• For welds, conformal meshes will be used.

  • A nonconformal mesh will be used for parts joined by contacts or joints.

Types of Meshes:

• Tetrahedral: Referring to their geometry

  • Hexahedral: Referring to their geometry

• Hybrid Meshing:

  • This is a multizone method, allowing you to mesh different parts of your imported or constructed geometry with differing methods. With this method, you perform less geometry and you possess more local control meshes.

• Sweep Meshing:

  • Mesh “sweeps” through the entire volume and all faces to help create an efficient mesh, that is accurately and regularly sized

Mesh Controls:

In ANSYS mechanical, to create a mesh select mesh on the tree, on the left-hand side of your screen, from here you can select the bodies, faces, or sides that you wish to mesh.

In the details section you can select your geometry and the bodies you wish to highlight, there is also a menu created in your work area for more specific regions. You may also alter your element size, which makes your mesh element smaller or larger, smaller sizes make for a finer mesh, allowing for more accurate simulations later. Behavior, soft or hard is ANSYS requiring a suggestion to either enforce your size restriction (hard) or allow minor edits for performance (soft).

Welds are found underneath Mesh → right-click → insert → weld

Once this has been selected you gain access to a customizable menu, titled Details of “Mesh,” based on your geometry you can define the scope of your weld.

P.S If you’re like me and a little clumsy with your mouse, if you close “details” or “outline” or any other toolbar recovery of them is easy.

• Head over to Home, in your top navigation bar then manage

  • Click Manage then whatever you closed to re-open it!

The power of ANSYS for welding lies in your Mesh:

Welded structures, due to their nature undergo variable loading conditions, var

Mesh Analysis:

Once a mesh is created it is best to analyze the statistics of the mesh, this is found in the Mesh section of the toolbar on the left hand of the screen:

The amount of nodes is a point of a fixed definition of its degrees of freedom, and the amount of elements is # of shapes comprised within your mesh. Theoretically, the finer your mesh, the more elements you have.

Mesh Metrics

This is a metric graph of Element Quality, the closer the values are to one the more of a perfect cubic element it is, whereas the closer to one the more deficient and inadequte.

There are other Metric graphs that could be implemented such as the Jacobian Ratio which tells you how distorted your elements are, the closer the value is to one, the lower the distortion value is.

Advanced Meshing

You can create a general size mesh, by selecting sizing → body (ctrl + b) → selecting the body then running the actual sizing, this will generate the mesh for the entire body, a basic means to simply create a quick and easy mesh to analyze the forces. After running the Mesh Metrics as mentioned before, and noticing non-continuous areas of force, we can proceed to advanced meshing or mesh refinement. For example, ref to the image below, if I have solved this mesh, but notice, a non-uniform spread of my force on that area, I can specifically create a mesh (face) sizing for that area and decrease the element size, to account for strange curvature in the area. This feature increases our control over our meshes and makes it simpler to analyze the forces.

In a local area of your geometry you can select refinement which can increase the number of tetrahedral elements in an area, refinement converts the enter body sizing into a tetrahedral as mentioned before but allows for way more depth in how refined you want a mesh to be. For Weld Analysis this tool is quite powerful, as you may want a general body mesh for the surrounding features, but an ultra fine mesh on the weld alone.

If the green represented a weld, by selecting refinement and then selecting that face we can specify the number of refinement iterations to generate a finer mesh. Ref to image below

The area we selected is way finer, but the surrounding area is not as intensely focused, in weldment analysis, Refinement is your best friend.

WELDS aren’t hard on ANSYS, MESH understanding is. Ref to More on WELDS.

Convergence requirement is a tool we can insert into our mesh analysis, this is only to be used when a stress/solution (deformation, strain, equiv stress etc.) is mesh-dependent in your analysis. To check for this, utilize the above mesh-refinement methods, and see if any of your solutions change significantly due to mesh alterations. If so, proceed with convergence.

Right-click solution factor → insert → convergence

What does convergence do?

• Convergence changes your mesh/refines your mesh until your model reaches a less-than “?” allowable change value respective to the mesh-dependent solution.

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  • If there is a less than 20% change in my calculated solution, from one iteration to the next, then it has converged and a solution has been found. If the value is too low, you may never converge, too high and you’re reverting your mesh refinement. (5% is my recommendation).

    • After defining your convergence conditions, navigate back to the solution and from here you can alter the maximum amount of refinement loops the amount of iterations you want convergence to run, and refinement depth similar to the Refinement tool mentioned before, the amount of subdivisions you wish to occur over the entirety of the mesh. After this process, your Mesh will be solved more finely.

      • THE STUDENT VERSION IS LIMITED TO 32, 000 nodes. A super-fine mesh is impossible with this version, but fun to try out.

The assumption when exploring Bolted Connections is that you've made holes for the allocated bolts, this can be done using the hole wizard on Solidworks

Below is a Sample piece/tutorial to help speed up and sim bolted connections:

Example Piece

For this simulation, I created a virtual wall, this is done by creating a reference plane where you want the wall to be, indicated by the plane called Wall.

• Simply right-click:

  • Then select local interactions:

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  • Select your adjacent face and the plane you created as a reference; now you have a virtual wall!

• After making your fixtures and applying your forces proceed to make your connections.

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  • After selecting this, select your edges and apply the bolts you wish to apply.

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  • Scrolling down in the menu allows for custom options, such as calculating the Tensile Stress Area or simply proceeding with the known Tensile Stress Area.

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  • You can insert various bolts relative to the fixtures that are needed: (Standard counterbore with Nut, Countersink, Standard or Counterbore, Countersink, Foundation bolt)

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    • Once these have been set up run your simulations!

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  • Results can be analyzed ( Stress, Strain, Displacement etc.)

  • Additionally, a Pin/Bolt Check Plot can be made to further analyze the connections:

    • Results → right click → Define Pin/Bolt Check Plot → green check mark

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    • Hope this helps!