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Tests to Determine Lengths during Reaction

of LQ cable

R. Bossert, F. Nobrega, N. Andreev, G. Ambrosio, I. Novitski

7-1-2008

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Start 22C

= Unreacted Cab le

= Reacted Cable

At 150C

Start point

Growth due to Thermal Expansionfrom 22C to 150C

Shrinkage due to a combination of growth due tothermal expansion and shrinkage due to stressrelaxation from manufacturing and/or winding ten-sion. It is assumed that the net change from thesetwo components is negative.

At 250C

At 650C

Growth due to a combination of growth from thermalexpansion, and change during reaction, which mightbe positive, zero, or negative. It is assumed that thenet change from these two components is positive.

At 22C

Shrinkage due to thermal contraction of thereacted cable. This shrinkage is greater thanthe amount of growth due to expansion in theunreacted cable.

Assumptions about Cable Length Changes during Reaction:

(After reaction, the cable is shorter than it was before reaction)

Ref: D.R. Dietderich, J.R. Litty, and R.M. Scanlan, Dimensional changes of Nb3Sn, Nb3Al and Bi2Sr2CaCu2O8 conductors during heat treatment and their implication for coil design, ACE(Materials) V44B, p1013 1998.

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Start 22C

= Unreacted Cab le

= Reacted Cable

At 150C

Start po int

Growth due to Thermal Expansionfrom 22C to 150C

Shrinkage due to a combination of growth due tothermal expansion and shrinkage due to stressrelaxation from manufacturing and/or winding ten-sion. It is assumed that the net change from thesetwo components is negative.

At 250C

At 650C

Growth due to a combination of growth from thermalexpansion, and change during reaction, which mightbe positive, zero, or negative. It is assumed that thenet change from these two components is positive.

At 22C

Shrinkage due to thermal contraction of thereacted cable. This shrinkage is greater thanthe amount of growth due to expansion in theunreacted cable.

titan ium

titanium

titanium

titanium

titanium

Longer titanium results in tension on coil.

When Titanium is Added:

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Start 22C

= Unreacted Cab le

= Reacted Cable

At 150C

Start point

Growth due to Thermal Expansionfrom 22C to 150C

Shrinkage due to a combination of growth due tothermal expansion and shrinkage due to stressrelaxation from manufacturing and/or winding ten-sion. It is assumed that the net change from thesetwo components is negative.

At 250C

First test.Free cable heated to 250C and back:

Free metal blockThis measurement gives us the starting length

Adding this measurement to (the differ-ence between the start measurement

and the 150C measurement times1.67) gives us the length at 250C

This measurement gives us thelength at 150C

At 22C

Shrinkage due to thermal contraction from250C to 22C. It is assumed to be the sameas the thermal contraction component of theexpansion from 22C to 250C

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Start 22C

At 150C

Start point

Growth due to Thermal Expansionfrom 22C to 150C

Shrinkage due to a combination of growth due tothermal expansion and shrinkage due to stressrelaxation from manufacturing and/or winding ten-sion. It is assumed that the net change from thesetwo components is negative.

At 250C

At 650C

Growth due to a combination of growth from thermalexpansion, and change during reaction, which mightbe positive, zero, or negative. It is assumed that thenet change from these two components is positive.

A t 22C

Shrinkage due to thermal contraction of thereacted cable. This shrinkage is greater thanthe amount of growth due to expansion in theunreacted cable.

Free metal block This measurement gives us the starting length

This measurement gives us thefinal length at 22C

This measurement gives us the length at 650C

= Reacted Cable

Second test.Identical piece of free cable heated to 650C and back:

= Unreacted Cable

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CableInsulation

Mica

Filler

Test pieces of cable will be 1 meter long, insulated pieces of RRP 54/61 LQ or TQ cable. They will be placed into channels of a fixture configured as shown in cross section below. The fixture is made of 1020 steel. Space provided will constrain the cable in width but be ample to allow the cable to grow in azimuth with reaction and slide freely.

Test Setup

1020 steel is used for the fixture because it has a CTE smaller than that of the cable. Therefore, when the cable is expanding longitudinally, it will move faster than the fixture, and be able to maintain contact with the free metal block. When the cable is contracting, it will contract faster than the fixture, ensuring that the free metal block (also 1020 steel) does not slide with respect to the fixture.

When the final measurements to the metal block are taken after cool-down, the movement of the block due to the CTE of 1020 steel will need to be subtracted from the total amount measured.

3 samples will be used in each test, allowing us to assess the consistency between tests.

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For Discussion

• Accuracy of underlying assumptions.

• General comments on test.

• Profile of heat treatment of samples.

• To verify whether or not 150C is the correct temperature at which stress relaxation begins, the temperature could be reduced to 22C after the initial increase to 150C, the free block measured, then compared to the final measurement after the first test.

• Sample size (3 or more?).

• Add an already-reacted cable to one channel?

• Choice of filler material to be used during test?

• Pre-heat treatment of 1020 steel test structure to eliminate stress relaxation during test.

• Further tests with “compressed” cable?

• Other?

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(a) Fractional change in length of an ITER conductor produced by IGC-AS. This 19 sub-element wire with 50 % Cu (b) Fractional change in length of a bronze processed conductor produced by Hitachi.

(a)

(b)