Week 3 Sheet metal Bending challenge

OBJECTIVE

To carry out static structural analysis on a sheet metal bending setup for different materials and to generate the required outputs from the aforementioned analysis. Throughout the challenge, materials such as Aluminium Alloy 1199, Copper Alloy NL and Magnesium Alloy NL are to be used for the sheet. Required outputs include equivalent stress, equivalent strain and directional deformation in the Y direction. A comparison is to be carried out.

The following are the specifications:

Case 1:Aluminium Alloy 1199( mentioned in the course video), Copper Alloy NL and Magnesium Alloy NL. Find out the Equivalent stress, Equivalent elastic strain and Total Deformation in the Y direction and compare the results for the three materials.

Case 2:With the material as Aluminium Alloy, change the friction coefficient to 0.19 and run the analysis as mentioned in Case 1. Compare the results with that in case 1.

Case 3: Refine the mesh on the plate such that it doesn't cross the academic limit. With Aluminium alloy as material, run the analysis as in Case 1 and compare the results.

MODEL IMAGE

PROCEDURE

Preface: After setting up and running the analysis in the first instance, all we need to do is change the material (for case 1), change frictional coefficient (for case 2) and change mesh sizing value (for case 3).

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. All of the materials we need (Aluminium Alloy NL, Copper Alloy NL and Magnesium Allow NL) are in the General Non-linear Material data source.

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.

One of the materials needed is Aluminium Alloy 1199, which is not listed in data sources. There's a simple fix, we can simply duplicate the current Aluminium Alloy NL material in the Engineering Data window (right-click > duplicate). Once we do that, we simply need to rename it to Aluminium Alloy 1199 and edit the following attributes for the duplicated material - Young's Modulus, Yield Strength and Tangent Modulus as shown in the below screenshot.

We can then exit out of the engineering data tab and return to the project schematic window, where 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 them as 'punch', 'die' and 'sheet' as shown. The material of the sheet would be the Aluminium Alloy 1199 we just created.

3. We can then go to connections in the outline and delete all the existing contacts and create new contacts. To do this, we can right-click 'Connections' from the outline > Insert > Manual Contact Region.

We will be creating two sets of contacts. The first contact is between the punch and the sheet. The contact regions would be the surfaces on the punch that come in contact with the die and the target region would be the surface on the sheet facing the punch.

The second contact would be between the sheet and the die - a similar concept. The contact face would be the sheet's surface facing the die and the target regions would be all the surfaces on the die that would come in contact with the sheet.

For both contacts, the type of contact would be frictional and the frictional coefficient will be 0.1. The rest of the settings will be as follows:

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).

One instance of sizing will be used for the punch and die bodies with an element size of 4mm.

Another for just the sheet with an element size of 1mm

Finally, a third one for the faces on the die and punch that come in contact with the sheet during the bending process - with an element size of 1mm.

Finally, right-click mesh > insert > method. For 'geometry', select the entire sheet body. The method would be 'tetrahedrons'.

After that, we can right-click mesh and select 'generate mesh'.

5. Next, we shall define the analysis settings. For that, we go to Static Structural > Analyses Settings. We shall be editing this entity in the window on the bottom left as shown. The number of steps will be 10 and after that, we will be selecting all the steps in the graph window by ctrl+clicking each manually.

THEN, we can work on the other options. They are edited as per the above screenshot, with the solver type as direct, large deflection turned on, constant stabilization and with an energy dissipation ratio of 0.1.

6. Now, we need to right-click static structural > Insert > Displacement. This process will be carried out thrice. In this case, we shall be working on the first displacement setting on the punch.

The 3 faces are selected as shown for 'geometry'. The X, Y and Z components will be based on tabular data but they will be constricted in the X & Z direction. Only the Y component values will be populated as shown in the screenshot.

For the next displacement setting, the surfaces involved would be those on either side of the sheet. The rest of the details are entered as shown:

Finally, the next displacement setting would be on the die where all the non-involved faces would be selected. As in the first displacement attribute, all the values for X & Z will all be 0. Here's a screenshot of it:

7. 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 finally, 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 sheet's material to the next non-linear alloy that is specified in the question. After case 1, we must make sure the material of the sheet is strictly Aluminium Alloy 1199.

For case 2: the friction coefficient for both contacts is changed to 0.19.

For case 3, the sizing attribute for the sheet's mesh will have a mesh size of 0.8mm instead of the previous 1mm.

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

Copper Alloy

Equivalent stress

Maximum & Minimum

Equivalent Strain

Maximum & Minimum

Deformation in Y Direction

Maximum & Minimum

Magnesium Alloy

Equivalent stress

Maximum & Minimum

Equivalent Strain

Maximum & Minimum

Deformation in Y Direction

Maximum & Minimum

Aluminium Alloy 1199

Equivalent stress

Maximum & Minimum

Equivalent Strain

Maximum & Minimum

Deformation in Y Direction

Maximum & Minimum

CASE 2

Equivalent stress

Maximum & Minimum

Equivalent Strain

Maximum & Minimum

Deformation in Y Direction

Maximum & Minimum

CASE 3

Equivalent stress

Maximum & Minimum

Equivalent strain

Maximum & Minimum

Deformation in Y Direction

Maximum & Minimum

OBSERVATIONS

In case 1, we can see that Aluminium allow 1199 generates the least stress out of the three. When it comes to deformation, copper has higher numbers in the positive Y direction - probably due to its ductility. But in the case of both stress and strain, magnesium alloy has higher numbers. Magnesium in general has very poor ductility properties and this may explain why there is higher stress generated and lower deformation created.

Coming to case 2, which involves comparing outputs between cases of different frictional coefficients in the applied contacts (on the same aluminium alloy 1199 sheet), we can see that there is a slight change in all the values. Case 2 involved contacts with higher frictional coefficient (0.19) as compared to case 1's (0.1). So there is nearly twice as much of a friction force threshold involved, therefore affecting the stress as well.

Between aluminium alloy sheets of case 1 and case 3, refining the mesh has resulted in fair difference in results. The decrease in mesh size will improve the accuracy of the results albeit case 1 had a 1mm mesh whereas case 3 had a 0.8mm mesh. The difference isn't drastic but it was drastic enough to affect the simulation time, which could be the deciding factor in these situations. Considering there was at least a 10% change in almost all values, it's fair to seriously consider this refinement in mesh, despite the time taken.

RESULT

Static structural analysis was carried out on the given sheet metal bending setup. A comparison between cases involving different materials and slight variations in analysis setups was carried out.

N.B. Due to the size of the simulation files and the upload limit, the reports generated through ANSYS have been attached with this challenge.