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Pixel Detector Supports

This document provides the requirements and goals for supporting the pixel detector, including concepts such as rolling, sliding, and toothed elements, as well as support locations and constraints. It also discusses the strength and stiffness of the axle.

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Pixel Detector Supports

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  1. Pixel Detector Supports T Loew, N Hartman, E Anderssen ID Engineering, Session #4 October, 2001

  2. Requirements | Goals E. Anderssen LBNL

  3. Partial Concepts List • Rolling, sliding or toothed elements. • Linear, torsion and other springs in diverse configurations. • Torsion and bending elements as springs themselves. • Rollers and ramps with either positive or negative “V” grooved features. • Dual stacked rollers; either self contacting or separate. • Roller with housing that initiates sliding contact with an overhead spring. • Stationary PST-mounted supports that catch and hold frame on linear slides. • Long screwdriver-type tool to set/release preload condition. E. Anderssen LBNL

  4. Preload Beam/Roller Schematic Beam spring achieves 75N preload with less than 1Nm moment transfer to the Pixel Frame. An applied force of 75N deflects the beam tip 2.5mm Pixel Frame PST Ø7mm axle fits within space envelope and satisfies overall deflection criteria E. Anderssen LBNL

  5. Rollers and Preload Beam Operation Preload Beam Roller Load Bearing Roller E. Anderssen LBNL

  6. Pixel Support Locations E. Anderssen LBNL

  7. Support Constraints & Locations Fixed Y Fixed X,Y z Fixed X,Y,Z Fixed Y x y E. Anderssen LBNL

  8. PST Support Envelope Support Dimensions Envelope Requirement Fit Within Requirement E. Anderssen LBNL

  9. PST Support Upper Profile Development Movement of load bearing and preloading rollers along lower ramp contour defines centerline trajectory and neutral path of upper contour. Neutral path boundary along which no preload force is generated. Centerlines Lower ramp contour Deviation from this path governs the correlation between the magnitude of preload and axial position within PST. E. Anderssen LBNL

  10. Dimensioned Path E. Anderssen LBNL

  11. Insertion and Preload Forces Insertion force due to services and rail sliding friction is a constant 130 N from insertion until the frame meets the supports. There is no preload in this region. Fi= 130 N P= 0 N If z* represents axial position in mm starting at the first contact with supports, then insertion and preload forces are predicted to be as follows: Fi(z*)= 0.5z* + 90.1 N P(z*)= 5.0z* N 0 < z* < 20 E. Anderssen LBNL

  12. PST Supports Deflection Deflections due to Bending and Shear: 75N 75N = + 11.1 μm 53.2mm 5.8 μm 5.3 μm This conservative first order determination is already larger than the 10 μm total budget allows, but it is of the right order of magnitude and will shrink by about half with reduced span length. E. Anderssen LBNL

  13. Axle Strength & Stiffness Back to back angular contact bearings. 75N 75N For Ø7mm Ti axle with 10mm bearing spacing, end deflection can be limited to 3μm. E. Anderssen LBNL

  14. Axle Strength & Stiffness Maximum moment of 1.1Nm on Ø7mm Ti axle σ = Mρ/I σmax = 314 MPa • For the titanium alloy Ti6Al4V, a safety factor > 2 can be • achieved against yield onset. • Due to the nature of the requirements, the axle’s • frequency response (~stiffness) drives the • design instead of strength. E. Anderssen LBNL

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