Bolt Pretension with Contact

Nonlinear Structural Analysis Goals Goal: – In this workshop our goal is to investigate the behavior of the pipe clamp assembly (Pipe_clamp.x_t) shown here. Specifically we wish to determine the crushing stress and deformation in a copper pipe section when the bolt in the clamp is torqued down.

Nonlinear Structural Analysis Assumptions We will assume the material used for the pipe is a copper alloy while all other parts are steel. It is assumed the clamp is torqued to 1000 N when placed in service. We’ll assume the coefficient of friction between the clamp and pipe is 0.4. The other contact regions will be treated as either bonded or no separation as shown in the accompanying figures.

Nonlinear Structural Analysis Start Page From the launcher start Simulation. Choose “Geometry > From File... “ and browse to the file “Pipe_Clamp.x_t”.

Nonlinear Structural Analysis Preprocessing Change the working unit system to metric mm. 1.“Units > Metric (mm, kg, MPa, C, s)” Insert the material “Copper Alloy” from the material library. 2.Highlight the “Part 2” in the geometry branch (pipe). 3.Click in the “Material” field and “Import….”

Nonlinear Structural Analysis Preprocessing 4.Select Copper Alloy from the “Material Data to Import” 4.

Nonlinear Structural Analysis Preprocessing 5.Expand the “Connections” branch and use the shift key to highlight all contact definitions. 6.In the details window change the Formulation to “Augmented Lagrange

Nonlinear Structural Analysis Preprocessing 7.Highlight the first contact branch. This is the definition for the pipe to clamp contact. 8.In the detail for the definition change the Type to “Frictional”. 9.Enter a value for “Friction Coefficient” of

Nonlinear Structural Analysis Preprocessing 10.Highlight the second contact branch. This is the definition for the bolt shaft to clamp hole contact. 11.From the details window change the Type to “No Separation”. The remaining 2 contact regions will be modeled using the default bonded type of contact

Nonlinear Structural Analysis Preprocessing Create a local coordinate system along the pipe’s axis. Note, we will use the local coordinate system for post processing later. 12.Highlight the Model branch. 13.“RMB > Insert > Coordinate Systems”. Notice the result is a new branch “Coordinate Systems” appears in the tree. Also, the “Global Coordinate System” is automatically placed in the branch

Nonlinear Structural Analysis Preprocessing With the Coordinate system branch highlighted: 14.Select the inside surface of the cylinder. 15.“RMB > Insert > Coordinate System”

Nonlinear Structural Analysis Preprocessing 16.From the detail for the new coordinate system change “Type” to “Cylindrical”. 17.Change the Principal Axis to the “Z” Direction 18.Defined by “Geometry Selection” 19. “Click to Change” on Geometry, then select the inner surface of the pipe and “Apply”

Nonlinear Structural Analysis Environment 20. Highlight “Static Structural” in the Map of Analysis Types 21.Uncheck “Launch Simulation Wizard” 22. Click “OK”. Project tree should now look as follows:

Nonlinear Structural Analysis Environment 22a. In the Details of “Analysis Settings” Window, define the following: – Number of Steps = 2 – Large Deflection = On This analysis is run in two load steps. In, Load Step 1, apply the bolt pretension In Load Step 2, lock this pretension and postprocess the working load.

Nonlinear Structural Analysis Environment 23. Select one of the end surfaces of the pipe. 24. Highlight “Static Structural” Branch RMB > Insert > Fixed Support

Nonlinear Structural Analysis Environment 25.Select the cylindrical face of the bolt part. “RMB > Insert > Bolt Pretension” 26.In the Detail of “Bolt Pretension” window enter a “Preload” value of 1000 for “Load” Step 1. Using the Timeline, Set load step to “2” and define Pretension as “Lock”

Nonlinear Structural Analysis Solution Setup 27.Switch to “Body” select mode. 28.Select the pipe part. 29.“RMB > Insert > Deformation > Directional”

Nonlinear Structural Analysis 30.From the detail for the “Directional Deformation” change to “Coordinate System”. Note we allowed the default name “Coordinate System” to be used when the local system was created. We could easily change the name to a more meaningful one. Solution Setup

Nonlinear Structural Analysis Solution Setup 31.Switch to face select mode. 32.Highlight the outer surface of the pipe. 33.“RMB > Insert > Contact Tool 34. RMB Contact Tool in the Contact Tool Branch Insert > Pressure Repeat steps 33 and 34 inserting contact “Frictional Stress”. Solve

Nonlinear Structural Analysis Solution Notes The solution for this workshop will take several minutes or more depending on the available hardware. The use of frictional contact triggers a nonlinear solution requiring equilibrium iterations. The solution progress can be viewed by opening the “Solution Information” folder.

Nonlinear Structural Analysis Results Recall that the solution triggered the use of “Weak Spring” stabilization. To insure that the weak springs are not the result of rigid body motion, highlight the Environment branch and inspect the weak spring reaction forces. Highlight Solution, “RMB > Insert > Probe> Force Reaction and specify in the details window the boundary condition as “Weak Springs” – Verify that the reaction in the weak springs is of the order e-5, a negligible value.

Nonlinear Structural Analysis Results Highlight Solution. RMB > Insert > Probe > Bolt Pretension to verify that the bolt pretension working load equals user defined preload – In Details of Bolt Pretension, define Boundary as Bolt Pretension (Trivial since there is only one bolt in this model). – RMB > Evaluate Results

Nonlinear Structural Analysis Results Highlighting and plotting the “Total Deformation” for the assembly shows the plot is not particularly useful for our goal (investigation of pipe’s behavior). The “scoped” result we placed in the solution branch will be more instructive.

Nonlinear Structural Analysis Results Highlight and plot the result “Directional Deformation”. In this case the result is scoped only to the pipe section. Also, since we employed a local cylindrical system at the pipe axis, the X direction here is displayed in the radial sense.

Nonlinear Structural Analysis Results Similarly, the behavior of the contact region can be view by highlighting the contact result objects. Again the use of scoped results allows a more intuitive plot of the quantity displayed.