IPP Annual Report 2007 - Max-Planck-Institut für Plasmaphysik ...

4.1.1.2.4 Central support elements (CSE)
Each coil is suspended on the central support structure via
two bolted connections between blocks as part of the coil
housings, and extensions of the central support structure.
These connections are typically made of a thick single or a
matrix of up to nine long and elastic Inconel 718 rods to
obtain a preload of 650-900 MP a per bolt at 4 K. Stainless
steel wedges are inserted between the coil blocks and the
shoulders of the CSS extension flanges. The wedges, according
to a new design, are welded onto the coil blocks by
two weld seams each (instead of previously one). The detail
analysis continued in close cooperation with Warsaw
University of Technology. Extended models were completed
for the complex triple and double connections NPC2-Z2 +
NPC3-Z2 + NPC4-Z2 and NPC1-Z1 + PLCA-Z1, respectively,
the new weld design for the wedges was confirmed,
and wedge installation procedures were defined with developed
parametric model of typical CSE. The process of
creation parametric models for all critical CSEs is on-going.
The set of such models allows to analyse variation of parameters
(e.g. tolerances) of components like wedges or shims
during assembly.
4.1.1.2.5 Lateral support elements (LSE)
The lateral support elements are located on the low field
outboard side and transmit tensile, compressive and shear
forces up to 1.7 MN, and bending moments up to 200 kNm,
resp. For the non-planar coil pairs 1-1, 1-2, 2-3, 3-4, 4-5 the
limited space permits welded solutions only. For the LSE
between the coils 5-5 at the module boundary a bolted solution
was adopted. The lateral support element weld dimensions
were finally defined, and the basic design of the bolted
LSE 5-5 at the module interface was completed. The functional
specifications were issued. During assembly quick
assessments concerning cracks and material imperfections
were performed which led to continuation of assembly without
significant interruption.
4.1.1.2.6 Narrow support elements (NSE)
The narrow support elements are sliding contacts (~30 per
half module), located on the high field inboard coil side.
They transmit forces up to 1.5 MN between adjacent coils
while simultaneously allowing relative coil movement up to
5 mm when in contact, and relative coil tilting up to
1 degree. In many cases there is a small initial gap in the
range from 0.2 mm up to 4.5 mm between the sliding surfaces
which close gradually during the coil current ramp-up.
The optimization and definition of the NSE gap widths was
an ongoing issue where the analysis results had to be ready
in correspondence to the assembly schedule. On the other
hand, fixing of these sensitive distances was delayed as long
as possible in order to have the most recent FE model and
design updates available. By end of the year this tedious
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work was done and all gaps for the NSEs inside of the halfmodules
were defined. The tilting of the NSE surfaces
against each other during loading adds a considerable sliding-rolling
path length to the pure relative translational coil
shift. Therefore, pre-tilting in opposite direction was introduced
for the NSEs with large tilting angles. The corresponding
algorithm was developed and implemented in the
design and manufacturing procedure.
4.1.1.2.7 Planar support elements (PSE)
The planar supports fix the planar on top of the non-planar
coils. Most of the PSEs are sliding elements with designs
similar to the sliding NSEs, allowing relative coil movements
up to 10 mm when in contact.
Figure 15: Fixed planar coil support elements; stress intensity in MPa
(bolt preload + EM forces in HJ regime)