atlas pixel detector september 2002 n. hartman lbnl 1 pixel support tube: design, prototyping, and...

September 2002 N. Hartman LBNL 1

ATLAS Pixel Detector

Pixel Support Tube:Design, Prototyping, and

ProductionPST Progress Update

September 2002



September 17th Review Schedule

• 9:00 PST Design Update• 9:30 Shell Prototyping• 9:45 Rail Prototyping• 10:00 Mounts and Interfaces• 10:30 Break• 10:50 Heater Testing• 11:05 Heater Design and Fabrication• 11:25 Production Planning, Costs, Schedules• 12:15 Questions/Comments



Pixel Support Tube (PST) Overview

• Design Updates– Flange design

• Reduced from 26 pieces to 2• Length Shortened

– Rail design• Impact on stiffness of forward shell calculated• Reduced from 2 pieces per rail to 1• Shell design augmented• Local stiffness analyzed

• Prototyping– Material test results received– Shell and rail prototypes fabricated (covered in subsequent

presentations)• Shell produced with heaters, and in hybrid form• Short rails produced and measured

• Production covered later



PST Overview


ATLAS Pixel DetectorSupport Condition of Pixel Support Tube in Inner Detector

SCT

TRT

Fixed XYZ

Fixed YZ (N/A)

Fixed XY

Fixed Y

ID Vee Rail (float Z/dogged Z)(constrained XY)

ID Flat Rail (float XZ)

(constrained Y)+Z

+XSide C Side A

+Y Vertical

SCT Vee Rail (float Z/dogged Z)(constrained XY)

SCT Flat Rail (float XZ)

(constrained Y)

View from top—allTube Supports are

Horizontal and Co-planar

Properties TBD

Constraint TBD

Flexure Mounts


ATLAS Pixel DetectorPST Key Structures

Forw

ard A

Forw

ard C

Barrel

PST Flanges

SCT Flexuresand mount pads

Mount Pad

Flexure

Forward End flange andFlexure, installation rail



Rail Overview

DETAIL Flat RailDETAIL V Rail

Vee and Flat rails were chosen to provide pseudo-kinematic support for the detector during delivery to the support points.

Rails are used only for delivery, not support.



Flange Design



Flange Face (machined layup)

Flange base(Layup)

Stiffeners(layups)

Flange bolts

Initial Flange Concept

• Base Piece– ½ mm thick– Laid up as hoop,

sized to fit shell

• Face Piece– Laid up as plate– Machined to size

• Reinforcements– Laid up individually– ½ mm thick– 24 parts

• Assembly– 26 pieces bonded

simultaneously as one assembly

– Flange assembly bonded to PST Shell



Revised Flange Concept

• Stiffeners eliminated– Not required for stiffness– Reduces part count by

90%

• Flange shortened– From 40 mm long to 25

mm– Allows thicker “skirt” in

order to machine ID, while approximately conserving material amount from old design

– Still extremely conservative bond stresses

• Two piece design– Single piece skirt and

flange face, provides good shear coupling to shell

– ID of skirt machined, but face is not

– Backing piece provides extra thickness for required stiffness

Flange Cross Section

Single piece skirt and face (“L” shape)

Backing Ring



Revised Flange Analysis

• ANSYS analysis– Stiffening ribs removed– Flange constrained over

bolt stress areas only (~2.5*Bolt Dia.)

– Bolts omitted on diameter (planned pin locations)

– 2 mm forward end offset used (worst case)

• Results– Sub-micron displacement in

flange– Max bolt load ~100 N (at

topmost bolt)

• Glue Stress Calculations– Simple shear stress

calculated (Shear = Axial Force/Area)

– Max bolt load used and area assumed to be ½ of 1 stiffening unit (1/48th of flange circumference)

– Max stress assumed of 21 Mpa (Hysol Adhesive)

– Factor of Safety = 140 for 25 mm long flange

Glue Shear Stress Calculation

Area

Max Bolt Force



Rail Design



Rail Design Summary

• So far, the PST has been modeled without considering the effect of rails in the bending stiffness of the shell– Provided for faster/easier modeling– Will result in higher displacements in the SCT when rails are added

• Rails have conflicting design demands– Rail deflection must be minimal, to assure installation of detector– Rail stiffness must also be minimal, to reduce impact on SCT

• Initial analysis showed problems– Rail deflections were perhaps acceptable (~150-200 microns)– However, impact on stiffness unacceptable (increase of 85%)

• Design shifted to one piece rail– Goal to increase local section modulus of rail, but with lowest cross

sectional area possible• “Hollow” shape more efficient• However takes up more space in PST

– Fiber changed to high strength carbon (rather than high modulus) in order to lower contribution to overall shell stiffness



Evolution of Rail Design

Initial rail shape designed to use as little space as possible inside

PST, and to allow placement of sliders

anywhere along frame

One piece design chosen to fill maximum volume (and increase

bending stiffness of rail itself). This was made possible by decision to place sliders/rollers at

end of frame, freeing up space for rail inside.

V-rail changed to “inverted” v shape. Increases inertia of

section, and can be used either as v or inverted v.

ATLAS Pixel DetectorRail FEA Model

Model simulates prototype of rails and 300 mm long shell(initial two-piece rail shape).

Pixel Mass (1/4 of 35 kg) applied to PEEK slider.

Slider impacts rail through contact elements.

Shell is constrained along edges (where flanges or stiffenerswould be).

Shell modeled as both quasi-isotropic glass laminate andcomposite hybrid laminate of carbon and glass.

300 mmrail

slider

shell constrainedon edges

Cross section of v-rail and slider

Prototype PEEK slider

center bearing Section

(R = 10 mm, L = 20)

tapers on ends forrail misalignment

slider

shell

ATLAS Pixel DetectorRail Analyses

Quasi-isotropic Glass ShellE = 19 GPa

Slider made from PEEKE = 3.5 GPa

Rail Quasi-isotropic CN60E = 126 GPa

Load Applied = 8.75 kg

Dmax = 185 microns

Composite Carbon/Glass Shell(Carbon in Hoop Direction)

Eaxial = 21 GPa; Ehoop = 147 GPa

Slider made from PEEKE = 3.5 GPa

Rail Quasi-isotropic CN60E = 126 GPa

Load Applied = 8.75 kg

Dmax = 154 microns

Hybrid Shell reducesrail displacement by 20%



Expected Rail Performance

• Rails displace more in beam mode than shell mode (displacements are primarily not in the cross sectional plane)– Deflection scales by stiffness (EI) of rail itself (to first order)– However, adding additional hoop plies of YSH80 (in the forward) does

help by about 20%• Different rail designs were compared for optimization

– FEA results used as a starting point and comparison– Different designs compared by calculating EI, and then scaling to

find expected stiffness and deflection implications

Summary of Rails I of Rail % Forward EI % Rail Defl. % Forward EI % Rail Defl.Initial 2 piece design 3280 181% 100% 130% 179%Closed Rail (Iter. 1) 4050.5 178% 81% 129% 145%

Final Iteration 6437.5 194% 51% 135% 91%Final Iteration w/ 2 YSH80 Plies 6437.5 194% 42% 135% 75%

Italics denote numbers that were generated by scaling, not directly from FEA analysis.

CN60 Rail P30 Rail

Deflection in final rail shape is anticipated to be on the order of 125 microns (5 mil).


Anticipated Loads/Displacements Induced in SCT

With Stiffer Forward PST Shells, Due to Installation Rails

Z constrained flexure is located on side C, negative X (in this coordinate system).

Load Direction Load Case FX (N) FY (N) FZ (N) FX (N) FY (N) FZ (N) dr (um) dphi (um) dZ (um)

Y dyA = dyC = 2 mm 0 77 1 1 74 3 11 11 1Y dyA = 2 mm 1 197 4 1 74 3 -22 24 9X dxA = dxC = 2 mm 82 3 76 77 4 92 30 19 -8X dxA = 2 mm 166 16 43 73 4 86 55 -36 -18X dxC = 2 mm 176 14 119 77 5 93 55 -36 -22

CTE Symmetric, 30 degrees C N/A N/A N/A N/A N/A N/A -10 -5 -12CTE Asymmetric, Side A, 30 degrees C N/A N/A N/A N/A N/A N/A -45 12 196

G gravity, pixel load of 75 kg 2 207 1 0 10 0 78 -75 -4

Max. disp. in SCT Structure

NOTES: Values in italics are scaled from shell stiffness calculations and previous FEA results. They assume an increase in forward shell stiffness of 35% over previous. Values in regular text were generated from FEA models as presented in the past.

PST/SCT Load ComparisonsModel Details Max. Force on Interlinks Max. Force at Forwards

Highest Displacements and Forces Still Arise from Gravity and CTE Loading,Which are not affected by an increase in the Forward Shell Stiffness.



Prototyping



Prototyping Plan• Material Testing

– First test completed– Results are fairly consistent, but disagree with calculations

• Shells – presented seperately– Completed– Successfully demonstrate ability to reliably make tubes of given size

• Rails – presented seperately– Partially Complete – foot long rails have been made– Successful so far, but issues remain– Rail Sliders and/or rollers need to be fabricated and tested

• Flanges– To be outsourced, not yet complete

• Hoop Stiffeners– May not be prototyped (fabricate during production phase only)

• Mount Pads/Flexures – presented seperately– To be fabricated in-house, not yet complete

• PST Assembly (bonding)– Not yet complete– To be fabricated in-house and/or outsourced– Design yet to be completed



Material Test Results

Item Tested Fiber Calc. E1 Test E1 Calc. E2 Test E2 Calc. Fiber% Test Fiber % Void %Barrel Layup (1) YSH80 26.3 17.8 26.3 17.0 57.3 52.2 1.2Barrel Layup (2) YSH80 24.5 19.3 24.5 18.0 55.8 N/A N/AFlange Material CN60 17.1 13.8 17.1 14.5 56.0 N/A N/A

• Calculations Differ substantially from results attained– Modulus of YSH80 samples is almost 40% low in cases (this modulus

would be expected with CN60 type fiber)– Modulus of CN60 sample is approximately 20% low– Fiber volume from one sample is low (other samples not tested)

• However, measurements are fairly consistent– YSH80 samples are both very low– E1 and E2 directions are similar (quasi-iso layups)– Spread in test data (from multiple coupons) is not extreme– Void content in one sample is fairly low (other samples not tested)



Major Outstanding Items• Design

– Rail Riders• Conservative choice is a rolling mechanism for detector

– Space available at end of frame– Detector is more than half of sliding mass (on four support points)

• Sliders will be retained for service structure– Space for rollers is probably not available– Each support sustains lower load

– Rails• Is 35% increase in bending stiffness of forward tube acceptable?• Rigorous FEA model of new rail design must be completed, along with tests to validate

stiffness– Flange/Mount Pads

• Design must be modified for new flange (without ribs)

• Prototyping– Material Properties

• Discrepancies must be reconciled (Test accuracy or fabrication?)– Hoop Stiffeners

• Layup separately or incorporate in shell layup (this would require prototyping)– Bond Tooling

• All design must be completed in order to finish prototype phase

atlas pixel detector september 2002 n. hartman lbnl 1 pixel support tube: design, prototyping, and...

Documents

atlas pixel detector

flange design slide

hartman lbnl

shell design

pst shell slide

rail prototyping

installation rail slide

rail overview