## General Mechanical

#### Bolt pretension

• andimens13
Subscriber

Hi,

I am trying to determine the amount of preload needed to clamp two plates of 0.5 mm gap between them. Under bolt pretension, i choose an adjustment of 0.5mm instead of specifying a preload. In the solution i was able to retrieve working load values of each bolt. i want to know how to determine the amount of preload needed to close that gap. Any help will be very appreciated. see attached picture below. The plates are fixed at one end each, so more of a cantilever.

• andimens13
Subscriber

• peteroznewman
Subscriber

If I understand, there are two cantilever beams with a 0.5 mm gap between them.

You have to define what you mean by "clamping".

The first contact between the beams will be at the tip. Is that clamped? I wouldn't say so.

As more force/adjustment is applied, the contact moves from the tip to the centerline of the bolt. Is that clamped?  You could argue that it is or it isn't yet.

As even more force/adjustment is applied, the contact moves to the diameter of the head of the nut/bolt. That is another definition of clamped.

Insert a Contact Tool in the Solution branch and Insert a Pressure result into that tool. Now you can see the demarcation between zero pressure and some pressure.

Site usage tip:  Don't mark your own post with Is Solution, because the discussion looks to be solved and members may not open the discussion anymore.

• andimens13
Subscriber
Thank you very much for your reply. Possibly I didn’t ask the question well. What I want to determine is that I have a gap of 5mm between the two plates acting as a Cantilever, how do I determined the force each bolt has to apply to get the gap close. I understand using a hand calculation I can determine the force needed to get a 0.5 mm deflection at the tip of the beam or any where along the beam. However I want to understand how I can determine the force apply by the bolt to close the gap.
Site usage tip: the solution mark was done by mistake. Thank you.
• peteroznewman
Subscriber

I suggest a multi-step solution. In step 1, you can have an adjustment of 0.5 mm, in step 2, an adjustment of 1.0 mm, in step 3 an adjustment of 1.5 mm, etc.

During one of the steps, the solver will fail to converge, but you can look at the results at all previous steps.  Next, refine your search with finer increments such as 1.2 mm, 1.3 mm, 1.4 mm etc.  For each one of these adjustments you can plot the working load.

• ME18102
Subscriber

I want to parameterize the Bolt Pretension but the check box for parameterization disappears once the step is increased from one. I did contact many people and they preferred to use APDL l for that. is there any alternative way?

• peteroznewman
Subscriber

You can't use Workbench parameters in a multistep solution.