1. Simulation of a Bolted Frame for the ISIS TS1 Project
Owain Williams
ISIS Neutron & Muon Source
Design Division

2. Aims: A cautionary tale…
What you already know…
Modelling bolts in FEA can be difficult and computationally expensive
Verification using hand calculations must be done with care, and testing is much better
The number of variables contributing to the stresses and strains in bolted connections can be quite large!
What you might not know (or, what I learned)…
Potential uses (and increasing understanding)
Limitations of hand calculations

3. ISIS TS1 Project: TRAM
Current
Proposed

4. Why Bolted?
Radiation Containment cell – Remote Handling Manipulator Arms
End of Life Disassembly and Removal

5. Initial Analysis Check frame components can withstand applied loads
Suggest improvements to increase strength / stiffness
Extracting Loads
Free Body Diagrams
Simplified Hand Calculations

6. Initial Results
Deflection – Simple Model
Stress – Simple Model

7. Bolted Joint Analysis Aims:
Make sure the bolts could support the applied eccentric loading
Quantify the loading on the bolts from torsion loads on the frame
Explore the possibility of other bolted joint methods, reducing the work required for end-of-life disassembly

8. Application to Project
Initial Hand Calculations (Roymech)
Other considerations:
Torsion on the frame
Reduction in bolt number and sizes
No-Slip Friction Joints

9. Bolted Joint Simulations
Types of simulations (credit to NAFEMS)
No-bolt
1-Dimensional Beam
Full bolt

10. Bolted Joint Simulation Methods
1-Dimensional Beam Element
Rigid Elements “spidered” to the nodes simulating the head and nut
Light-weight (and linear analysis)
Unrealistic load path – inaccurate local stresses
Methodology is to extract loads on each bolt, and use them in hand calculations
Easy to set up (although still tedious for a large number of bolts)

11. Bolted Joint Simulation Results
1D Beam Element Connections
Limitations
Stress – Bolted Model
Connections “spidered” to 1D Beam Element

12. Results
Reasonable agreement with Hand Calculations for Worst Case – Hand calculations always more conservative

13. Uncertainty… Go to 2D
Why is there such a disparity in the bolt load results?
Load = 335kN
91kN
141kN
26kN
89kN

14. Hand Calculations: Elastic Method
Principle of Superposition
All Loads and Moments moved to the CoG of the Bolt Pattern
Conservative – only models the worst case

15. Instantaneous Centre of Rotation
2D Static Analysis: Displacement

16. Conclusions and Further Work
1D Beam Modelling of Bolts can yield useful results, in conjunction with empirical recommendations
Plans for testing in the future!