| Applies To | |
| Product(s): | AutoPIPE |
| Version(s): | ALL; |
| Area: | Modeling |
| Date Logged & Current Version | Dec 2022 12.08.03.015 |
Problem:
How to model a support that has a breakaway force and then free to move using AutoPIPE?
Example
U-bolt that is tightened down on the pipe, when axial load sufficiently overcomes the friction load which was calculated to be 1000 N, the pipe will spring / slip / free to move in the axial direction.
Solution:
Easy, AutoPIPE has a support that can be configured to accommodate multiple types of scenarios such as this, see AutoPIPE help for Incline support, Ultimate Force Gap. Please take the time to read about "Understanding Ultimate Force Gap Supports" for better understanding on the versatility and potential modeling scenarios with an incline support.
In this case, one would model this scenario using 2 supports:
1. Guide Support -
This support will resist lateral and vertical movement. Model a guide support stiffness and gaps as needed, while Friction should be set to 0.00.
2. Incline Support -
The axial movement characteristics will be modeled with this support.
Note the settings on the incline dialog above. Recall that the breakaway force was calculate to be 1000 N. Therefore, breakaway was set to 1000 N. After reaching breakaway, the pipe is free to move during Phase 1 and Phase 2, thus K1 and K2 resistance, both forward and back stiffness's, are set to 0.00 in the global axis direction (ex. Global X). One could have modeled a Phase K1 distance, use any value, but not needed because the resistance is free for both K1 and K2 ranges.
Results
When enabling the Ultimate Force Gap, the program will prevent any movement in the direction of the restraint until a breakaway force value specified by the user is achieved. Once the breakaway force value is achieved in the positive or negative direction, the support exerts the first stiffness value (K1) specified by the user until the K1 phase is travelled. Once the K1 phase is travelled, the support exerts the second stiffness value (K2) specified by the user.
If the breakaway force is not attained in this case, the load that arises on the Incline support will range from 0.00 to 1000 N. If a force has built up to overcome the breaking away force, that load will be transferred onto the K1 Spring. Since the K1 stiffness is free (0 N/mm), the point slips or springs with out consuming any force. The load on the support is reduced to 0.00 N as a result. In order to move again once this point rests, it must overcome breakaway force.
Think of it this way, the break away force is like a shackle, once the forces reaches the breaking point of the shackle, it breaks. The breaking force dissipates as it is now free to move, no stiffness settings. Once the pipe reaches equilibrium, the shackle is reapplied and the process will repeat.