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

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

ISIS TS1 Project: TRAM Current Proposed

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

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

Initial Results Deflection – Simple Model Stress – Simple Model

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

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

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

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)

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

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

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

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

Instantaneous Centre of Rotation 2D Static Analysis: Displacement

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