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NCSX

CTD Test Results

Kalish 11/30/04

Modulus

y = 21414x + 10.951

-200

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-0.01 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

Strain

Stre

ss

Series1modulusLinear (modulus)

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NCSX

The Issue

• The Winding Pack (WP) insulation (pre-impregnated S-2 glass with co-wound polyimide film) has orthotropic CTE () values which are much different than that of the Cu conductor (from 300 to 80K): Normal (Insulation) = 25 to 28+ In-Plane (Insulation) = 7 to 8 Isotropic(Cu Cond.) =

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NCSXWinding Pack at 85K

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NCSX

When the WP is Cooled to LN2:

• The Cu contracts more than low-In-Plane Turn-Wrap Insulation.

• This produces deformations at the corners which push layers apart.

• Max. Tensile stresses approach 8 MPa

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NCSXThe Issue

• When data is not available the design requirements document requires we use .02% strain as the tension allowable normal to the plane of the glass. Using 22 GPa as the composite out of plane modulus the max. allowable tensile stress is only 4.4 MPa

• Max. tensile stress resulting from coil cool down per FEA analysis are in the range of 8 MPa

• CTD was contracted to test the ultimate tensile strength of the composite

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NCSXModulus

y = 21414x + 10.951

-200

0

200

400

600

800

1000

1200

1400

1600

-0.01 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

Strain

Stre

ss

Series1modulusLinear (modulus)

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NCSX Results / Implications

• All 4 grit blasted/primed test samples survived• The one primed only sample that survived

showed a similar tensile yield to the grit blasted sample

• Avg. Ultimate Tensile strength was 9.0 MPa. resulting in an allowable of 1/5 x 9 = 1.8 MPa (lower than the 4.4 MPa based on .02% strain)

• Max Ultimate Tensile strength may have been as much as 7x higher if the failure began at the edges and the sample “unzipped”

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NCSXOther Tensile Test Results

• Rutherford Lab Tensile Test– 8 MPa average stress at failure– 60 MPa max stress based on analysis– Max Stress = 7.8 x avg. stress

• Rutherford specimen = 40mm dia. by .030 inch thick

• CTD specimen = 12.6 mm dia. by .050 inch thick– Compares to 9 MPa average stress at failure

for CTD Sample

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NCSXModulus Results

• Modulus results were suspect– expect 22 GPa– result = .13 GPa

• Test to be repeated with solid billet replacing test sample

• Possible that slow “unzipping” failure results in bogus Modulus result

• If strain results are anywhere near correct for these samples failure occurred at between .07 and .1 strain. The tensile stresses resulting from cool down are in the range of only .0024 strain a factor of 30 less.

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NCSXUnzipping Study

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NCSXConclusion

• Test results inconclusive• Require cyclical thermal testing of

representative winding pack to validate design