'cylinder with prestressed bolts' simulation project by rszoeke


#1

I created a new simulation project called 'cylinder with prestressed bolts':

Copy of project cylinder-test1 - stress test of torr segments by @rotteman


More of my public projects can be found here.


#2

Nonlinear Static Analysis of a 30 part assembly with pre-stressed bolts and physical contact.
Some sample results:

Geometry/Mesh

Pre-Stress on Bolts

Von Mises Stress on full assembly

Displacement


#3

Hi. I had problems in several areas setting up this model & simulation.

  1. Material: I wanted to assign steel to the bolts,nuts and washers & aluminum to the two castings. I tried assigning the material in the second panel. but I could not see if they were assigned or not. I also tried the third panel model-but i could not see any material assignment. How do you tell what materials have been assigned for each part?
  2. Load: How do you apply the load? Do you apply a set tension stress at the washer interface or a set deflection of the bolt length ?
  3. Is the reason you used nonlinear vs linear analysis because you exceeded the stress limit on the bolts?

#4

Hi @rotteman,
I’ll try to answer to you questions one-by-one:

  1. Generally if you are new to SimScale I would highly recommend you having a look at our learning page. There you find a loot of useful information that will help you getting started a lot quicker, especially our short video tutorials could be a good starting point.

For every setting in the workbench where you have an assignment, you can visualize the assigned entities by clicking on Select assignment. All assigned entities will then be selected in the viewer and are shown in red:

One thing that might confuse at the beginning is that we have two decoupled entity type (vertex, edge, face, volume) specification locations. Above the viewer in the row of symbols you can choose which entity type you want to select by clicking in the viewer:

For a material assignment, the volume selection has to be activated since materials can only be assigned to volumes.

Additionally above the assignemnt box in the settings panel of the material itself (or any boundary or initial condition) you can select which entity type should be active (for BCs there are multiple possible, for materials only volume (sets)):

  1. The pre-stress in the bolts is set with a predefined deflection which is done in the physical contact named Contact Washer - Bottom Prestress where I used a fictitious clearance* of 0.1 mm to define it:

  1. A nonlinear analysis was used since it is obligatory for using a physical contact. The prestress was basically a random value and just to show how a prestress could be set up for such an analysis.

Best,
Richard


#5

Hi, it appears that you have applied the penalty contact between the bottom face of the lower body and the lower washer upper face, effectively adding a fictitious rigid body of depth 0.1mm between the two. Is this assumption correct?

You have also applied this displacement as a function of time? I don’t understand why this would be a function of time.

Thank you in advance for any help you can give on this matter.

Regards,

James


#6

Hello @Jamesg83,
your assumption is almost correct. The added thickness is 0.1mm, but it is not applied as a rigid body, both master and slave surfaces do not get any additional stiffness via this.

Applying the pre-stress as a function of time is done because of the nonlinearities involved. We could also just use a static value of 0.1mm, but if this would not converge in the first step, there is no chance to reach convergence. Using a ramped value allows an effective time step subdivision in case of convergence problems. I am normally doing this for any load in a nonlinear analysis, it’s good practice.

Best,
Richard


#7

Thank you for your quick response. This has clarified my issues.

Regards,

James