Coupled thermalstructural FEA of AS tooling for brazing

Coupled thermal-structural FEA of AS tooling for brazing of manifolds to disk stack R. Raatikainen, F. Rossi 17. 10. 2011

INDEX Ø Introduction to AS tooling Ø Transient FEA description Ø Results Ø Conclusion

Introduction to AS tooling 4. Brazing (Au. Cu 25/75, 1040 °C) 4 4 4 5. Machining 6. Cleaning 4 4 4 Stack type 1 7. QC - Cooling circuit test 8. Brazing (Au. Cu 25/75, 1040 °C) 9. QC 1. Vacuum test Structure type 1 Structure type 3 1. Vacuum test 2. Cooling circuit test 3. Fiducialisation (Leitz) 10. Brazing (Au. Cu 35/65, 1020 °C) 11. QC Stack type 3 4 16

Introduction to AS tooling • Upper spring (graphite): apply a vertical force on the manifolds through the upper support and allow thermal expansion of the assembly during the brazing cycle. • Rod (stainless steel): connect upper support and lower plate. • Lower plate (graphite): support the assembly during alignment operations and brazing cycle. • Wedges (ceramic): allow small adjustment of manifolds in the vertical direction. • Lateral springs (graphite): apply an horizontal force to the manifolds through the lateral plates and allow thermal expansion of the assembly during the brazing cycle (k=20 N/mm). • Lateral supports (stainless steel): support the springs. Upper support Nut Upper spring Lateral plate Lateral spring Lateral support Lower plate Wedges Rod

Introduction to AS tooling Steady-state analysis Brazing cycle inside furnace 3 h 1020 °C 900 °C Transient analysis

Transient FEA description Ø Thermal analysis has been performed to calculate the stresses during the brazing cycle and to compare them to the previous ones calculated in a steady-state thermal analysis (EDMS 1151868 v. 1). Ø The real temperature cycle is imported into ANSYS and a coupled thermal-structural FEA was carried out. Ø The material properties has been taken into account as a function of temperature. Illustration of nonlinear material data; Young’s modulus as a function of temperature.

Boundary conditions Ø Thermal: temperature constraint applied on the exterior surfaces corresponding the real temperature cycle inside the furnace. Ø Structural: lateral springs + sliding constraints. Frictional contact between the manifolds and the stack. Critical point Applied structural boundary conditions. Temperature cycle during the brazing process.

Thermal results Ø The thermal-structural behaviour of the structure has been studied more in detail around the maximum temperature (1020 °C) of the brazing process. Ø The time resolution for the transient analysis has been set to appreciate the real temperature gradient inside the structure. Ø Below the temperature gradient at different time instants. 20 s 60 s

Structural results - Deformation Ø The highest thermal deformations occur at the maximum temperature. Radial deformation of the AS disks at 1020 °C Deformation contours in the x-direction at 1020 °C

Structural results – Stress & Relaxation Ø The highest stress concentration occurs around the iris area and the damping slots. • Stress contours around the AS iris area: maximum stress = 0. 12 MPa • No residual deformations occur at the end of the brazing process

Conclusion Ø A transient FE analysis has been performed to study thermo-structural behaviour of the AS tooling for the brazing of the manifolds to disk stack. Ø The real temperature profile measured during the heating cycle has been taken into account in the simulation and the material properties have been considered in the model as function of the temperature. Ø During the entire heating process the stresses remain below the yield strength of the material, i. e no residual deformation is foreseen at the end of the process. ØSince the temperature is changing very slowly during the brazing cycle, no differences are seen between the previous steady-state thermal analysis and the current transient simulation. NEXT Ø Further simulations will be performed for the other tooling involved in the assembly procedure of AS for TM 0 LAB.