Week 3 Verification of Weld Joints

OBJECTIVE

To carry out a static structural analysis on a weld joint model and compare certain outputs of welds of different materials - specifically stainless steel, aluminium alloy and bronze. The outputs to be requested are directional deformation and equivalent strain generated in the model.

The following are the specifications:

Case 1: Stainless Steel: In this case, the material of the plates must also be the same. Use Stainless steel for both weldments and plates. No need to add flux to the weldments.

Case 2: Aluminium Alloy: The material to be chosen for this case is Aluminium alloy (high strength, wrought). [Plate material to be used is stainless steel]

Case 3: Bronze: In order to simulate "Brazing", you should be using bronze as the weld material. Assign Stainless Steel to both plates and Copper to the "Ribs".

MODEL IMAGE

PROCEDURE

1. After opening ANSYS Workbench, we are met with the Project Schematic window. Here, we can select the 'System Structural' analysis system on the left. Doing so creates a new project. Here, we can rename the project and also change the material if needed. We will need to right-click 'Geometry' and select 'import'. The file provided for this project should be selected. 

Now, we can add the materials right here and make our job easier for later. To do that, we need to double-click Engineering Data'. This opens up the list of inserted materials. We can pick materials we need from the repository listed here. Most of the materials we need are available in the source list. We may need to create one of the required materials - Aluminium alloy (high strength, wrought).

To do that, we can go ahead and create the materials within this library we had created for a previous project. We just need to select the checkbox as shown by the green box below. To create your new material inside this library, click on ‘Click here to add a new material’, which should be an option in the outline of the current library. Once we do that, we can name the material and drag various attributes from the toolbox on the left to the properties section at the bottom, as shown below. The values entered are specified as per requirements.

After that, we simply need to click the yellow '+' symbol on each material's corresponding 'add' column to add these specific materials to the project. Once we are done, we can simply close the tab - the program may ask if you want to save - you can respond in the affirmative.

Once we return to the project schematic window, we can right-click geometry and select 'edit'. This will bring the model up in the Mechanical interface.

2. In the mechanical interface, in the outline, under geometry, we can rename each of the components if needed. We can rename the non-weld parts as shown:

3. We can then go to connections in the outline and rename all the existing contacts by right-clicking connections > rename based on definition.

We can then highlight all the contacts that do not involve a weld and edit certain attributes of theirs - particularly the type (as frictional) and the frictional coefficient as shown:

4. We can now move on to mesh creation. We will need to make use of the mesh sizing function to refine the mesh in particular regions (right-click Mesh in outline > insert > sizing).

Here, we will be selecting just the small and big plates for the geometry attribute and assign a sizing of 7mm.

5. Next, we shall define the analysis settings. For that, we go to Static Structural > Analyses Settings. Right-click analysis settings > insert > fixed support.

For this fixed support, the geometry will be one of the surfaces of the larger plate (see screenshot).

Then, we can right-click analysis settings again > insert > force.

For this analysis, the geometry is going to include the faces of the rectangular hole in the small plate. The requirement mentions applying a 15000N load in Y direction. Therefore, for this force setting, we shall be entering 15000N for the Y component attribute as shown below (after defining force by components).

6. Now we can generate the outputs. To do this, we can right-click Solution > Insert > Strain > Equivalent (Von-Mises) (for equivalent strain), right-click Solution > Insert > Stress > Equivalent (Von-Mises) (for stress) and right-click Solution > Insert > Deformation > Directional (specify the orientation as shown in the below screenshot).

Now, all we need to do is right-click solution again and click 'Evaluate all results'. After the results are generated, we just need to save the project and come back to the mechanical interface and change the welds' material as per case requirements (also change rib material in case 3 to copper).

Care must be taken to ensure that the file is saved after generating the result in each case.

Finally, when the analysis is done, we can view the results by simply clicking each of these solution entities we created, in the Outline menu.

OUTPUTS

CASE 1 - STAINLESS STEEL WELDS, PLATES AND RIBS

Directional Deformation in Y Direction

Maximum & Minimum

Equivalent Strain

Maximum & Minimum

Weld Stresses

CASE 2 - ALUMINIUM ALLOY WELDS & STAINLESS STEEL RIBS AND PLATES

Directional Deformation in Y Direction

Maximum & Minimum

Equivalent Strain

Maximum & Minimum

Weld Stresses

CASE 3 - BRONZE WELD MATERIAL, COPPER RIBS AND STAINLESS STEEL PLATES

Directional Deformation in Y Direction

Maximum & Minimum

Equivalent Strain

Maximum & Minimum

Weld Stresses

OBSERVATIONS

The material of the welds seems to play a large role in these numbers. Aluminium and bronze (a copper-based alloy) are generally more ductile and has lesser tensile strength than stainless steel, which was used in case 1. This explains the higher stresses generated (see below) in stainless steel and as a result, lower deformation and lower strain numbers. In case 3, the use of copper in the ribs exacerbates the deformation situation due to copper's ductile nature. This affects the overall model and resulted in the most deformation among the three cases.

As discussed previously, stainless steel welds did produce the most stress, particularly due to stainless steel's higher tensile strength as compared to the other materials used. In addition to that, in all three cases, the following weld joint experienced the highest equivalent stress.

RESULT

Static structural analysis was carried out on the given weld joint model and the outputs of different cases with different weld materials were compared. Stainless steel seems to be the best option due to its higher strength and resistance to deformation.