NCSX Vacuum Vessel

Stress Analysis Peer Review

Fred Dahlgren

22 April 2004

• Purpose of analysis:To varify the adequacy of the vessel design and assure the design criteria are met.

• Method:Finite element analysis using MSC/Nastran, Static(sol 101), Buckling(sol 105).

• Assumptions:-Vessel & port configuration as of 10 April ‘04 Pro-E models.

-Material of shell & port nozzles and cover plates fabricated from Inconel 625 Annealed – Grade 1 sheet per ASTM B 443.

-Material properties (Linear elastic, isotropic material properties) taken from the Huntington Alloys International Inconel 625 product bulletin.

-Rigid vertical structural support to eliminate rigid body modes. (Elastic supports not yet included in the model)

-Preliminary static model loads assume isothermal, 1-g gravity, 1 Atmosphere external pressure @14.7psi.

-Disruption loads are derived from Spark ver.20b inductive solutions for a stationary center plasma and a plasma displaced 10 cm vertically up from its central equilbrium position.

• Material Properties(@ 300 deg.C - 572 deg.F):

-Youngs Modulus 28.1e6 psi

-Shear Modulus 10.8e6 psi

-Poissons’ Ratio 0.289

-Density 0.305 lbs/cu. in.

-Coeff. of Thermal Exp. 7.3e-6 in./in.-deg.F

• Material Properties (@ 20 deg.C – 70 deg.F):

-Youngs Modulus 30.1e6 psi

-Shear Modulus 11.8e6 psi

-Poissons’ Ratio 0.278

-Density 0.305 lbs/cu. In.

-Coeff. of Thermal Exp. 7.1e-6 in./in.-deg.F

Values from Pro-E Model used

Material Thicknesses for VV model ( inches):Shell 0.375Port 2 0.125Port 3 0.125Port 4 0.500Port 6 0.250Port 7 0.125Port 8 0.125Port 9 0.125Port 10 0.125Port 11 0.125Port 12 0.500Port 15 0.125RF-Turret 0.188*Port 17 0.125Port 18 0.125

Main Flange Dimensions: 0.65 wide x 0.85 deep, 0.375 weld

Model Details:

38,892 DOF’s

7779 GRID POINTS

7,147 CQUAD4

1,175 CTRIA3

40 MPC’s

2 SPC’s

Boundary Conditions:

Cylic-Symmetry @ welded edge

Via MPC’s

Normal Operating Loads:

Uniform external 14.7 psi

Gravity – 1g

Off-Normal (EM Disruption) Loads:

320kA Plasma @ 1.7T

210kA Plasma @ 2.0T (High Beta)

320kA Plasma @ 1.7T @dZ=10cm

(Inductively coupled solutions)

MPC’s (cyclic-symm.)

NCSX VACUUM VESSEL NASTRAN 120 DEG. FEA MODEL

DISPLACEMENTS FOR 1 ATMOSPHERE LOADING

Run 120bbe3: 1 Atmosphere External Pressure Only

Peak Shell Displacement .125”

Peak Tresca Stress @ Vertical Restraint 18 ksi

Peak Tresca Stress@Outer Surface Z215.2 ksi

Run 120bbe3: Tresca Stresses in the flange and weld areas are 1 to 7 ksi

Attempts to stiffen the shell locally – not very effective

Added 2 Ribs .5 x 1” high Added 3rd Rib .5 x 1” high

Peak shell deflection 0.085 for 0.5” thk. Shell & 1 Atmosphere Load

Run 120bbe3g – 1 Atmosphere External Pressure + 1g Gravity Loading

Tresca Stress From 1 Atmosphere + Gravity Loading

Stress @ Support18.3 ksi

Peak Stress@ turret/shell20.9 ksi

Run 120bbe3gf Cantilevered Loading Of Ports:

A cantilevered load, at various port ends, was applied via a concentrated weightof 500lbs to simulate a 250lb load at the end of the port extension ( 2x length =2x load)* Actual port end deflection with the port extension will be higher (~4x for 2x length).

Max. deflection* 1.26”

Outer Surface Tresca Stress From 500lb Cantilevered Load on Port Ends

34.2ksi Tresca Stress

Inner Surface Tresca Stress 46.8 ksiDue To 500lb Cantilevered Load @ port18/turret intersection

Tresca Stress reduced below 22ksiIn the turret and weld region

Stress & deflection still high in nozzle27.3ksi - ~1” displacement @end

Increase nozzle thickness to .188”?

Run 120bbegf-2 with turret wall 0.375” thick

Buckling Eigenvalue = 12.99 - for 1 Atmosphere loading

Run 120bbe3-buckle – Pre-load: 1 Atmosphere, Eigenvalue extraction method: Lanczos

Allowable Stresses For Inconel 625 – Section VIII, Division 1 - ASME BPVC

575 deg.F Bake-out

Status:

-The preliminary static runs for normal operations are completed.

-A run with the bakeout thermal distribution and one with the normal

operating temperature distribution are in work but not complete.

-Runs with disruption loads are not yet completed.

-A 360 degree model will be used to evaluate asymmetric loading conditions and

evaluate any global buckling conditions.

Conclusions:

-Stresses from the normal runs in the shell and ports are below the

allowable stress with the exception of the Port18 cantilevered loading requirement.

Recommend either thickening the turret wall and port nozzle to reduce stress at the

nozzle/port intersection and to reduce vertical deflections of the port, or implement

a radially compliant vertical nozzle support off the cryostat. Port15 also needs support.

-Shell displacements are generally low with the exception of the area between port2

and port9 which indicate a displacement of 0.125” total. Recommend thickening or reinforcing

the shell locally to reduce these deflections.