01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 1 CERN European Organization for Nuclear Research Mechanical Engineering and Thermo-mechanical

01.07.200401.07.2004 A. Bertarelli – R. PerretA. Bertarelli – R. PerretCERN TS – MME GroupCERN TS – MME Group

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CERN CERN European Organization for Nuclear ResearchEuropean Organization for Nuclear Research

Mechanical Engineering and Thermo-mechanical Analysis of LHC Collimators

Alessandro BertarelliTS – Materials and Mechanical Engineering Group

External Review of LHC Collimator Project01 July 2004


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OUTLINEOUTLINE

Project RequirementsProject Requirements Design strategyDesign strategy Technical designTechnical design Thermal and Mechanical Thermal and Mechanical

CalculationsCalculations ConclusionsConclusions


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Functional specification (Mechanical Functional specification (Mechanical aspects):aspects): – High absorbed heat load (up to 32 kW)– Very high precision (25m on 1200mm)– High robustness in accident cases (up to

700ºC)– Low-Z, high conductivity materials for jaw

(carbon based)– Limited jaw temperature (<~50º C) for

outgassing reasons– Easy maintenance

Schedule (see M. Mayer’s talk for details)– Design Activity started in September 2003 – First full prototype TCS by May 2004

PROJECT REQUIREMENTSPROJECT REQUIREMENTS


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How to meet the challenging requirements ? How to meet the challenging requirements ? Highest priority to Secondary Collimators (TCS)

… Contribution of many experts … Wide exploitation of LEP experience … In-depth calculations carried out from the early

stages of development (concurrent design) … Mix of traditional and edge technologies. Advanced Materials (C/C composites, GlidCop®

…). Specific tests to validate most critical

technologies (S. Calatroni’s talk)

DESIGN STRATEGYDESIGN STRATEGY


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Main Features (TCS design)Main Features (TCS design) Multi-DoF internal alignment system. Monolithic jaw (1200mm) clamped to

the support. Decoupling and compensation of

thermal deformations. Cooling system. RF contacts for low impedance. Actuation system (2 step-motors per

jaw). External alignment system and plug-in Electronic controls

TECHNICAL DESIGNTECHNICAL DESIGN


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TECHNICAL DESIGNTECHNICAL DESIGNMechanical AssemblyMechanical Assembly

Beam axis

Overall length: 1480mmTank width: 260mm

Vacuum Tank

Main support and plug-in

External adjustment motor

Actuation system


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TECHNICAL DESIGNTECHNICAL DESIGNCollimator Cross-section (1/2)Collimator Cross-section (1/2)

SupportBar

Clamping springs

Jaw(25x80x1200

mm)

Cooling Pipes

Bellow

Return Spring

Stepper Motor

Jaw stroke+30/-5 mm


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TECHNICAL DESIGNTECHNICAL DESIGNCollimator BlocCollimator Bloc

1. Jaws in C/C or graphite2. Cooling Cu-pipes and plate pressed against the

jaw, brazed to the bar.3. GlidCop® support bar and clamping plates

• Low thermal contact resistance (P=3÷5 bar)

• Differential thermal expansion allowed• Deformations minimized

(compensation)

3

2 1


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TECHNICAL DESIGNTECHNICAL DESIGNActuating SystemActuating System

1. Jaw actuated by 2 stepper-motors via a roller screw (10 m/step)

2. Return spring for semi - automatic pullback and play recovery

3. Rack-pinion system to prevent misalignments

4. Vertical sliding of the jaw surface ( 10mm)

1

1

22 3

3


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TECHNICAL DESIGNTECHNICAL DESIGNCooling SystemCooling System

Jaw cooled by 2 Ø6 OFE-Cu pipes (3 loops each)

Outer section squared (9) to allow brazing to internal and external plates

Water from general cooling circuit (Inlet temp. up to 27ºC)

Water flow 5 l/min (20 l/min per collimator) leading to a 3 m/s velocity


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THERMOMECHANICAL THERMOMECHANICAL ANALYSISANALYSIS

Main problems to tackle in Main problems to tackle in analysis and design …analysis and design …

How to evacuate heat How to evacuate heat loads?loads?

How to join graphite jaw How to join graphite jaw and metal support?and metal support?

How to keep thermal How to keep thermal deformations to a deformations to a minimum?minimum?


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Extensive analytical and numerical Extensive analytical and numerical calculations.calculations.

Semi-analytical models for Semi-analytical models for Thermal contact Thermal contact resistanceresistance, , ConvectionConvection, , Thermal bendingThermal bending … …

Many FE models (ANSYS®) of the TCS were Many FE models (ANSYS®) of the TCS were studied:studied:– 2- and 3-dimensional … 2- and 3-dimensional …

– Different materials (C/C, C, Cu, Steel, Different materials (C/C, C, Cu, Steel, GlidcopGlidcop®®)…)…

– Input thermal load imported from FLUKA Input thermal load imported from FLUKA simulations …simulations …

– Different load cases (nominal, accident, Different load cases (nominal, accident, transient)transient)

– Complex boundary conditions …Complex boundary conditions …

THERMOMECHANICAL THERMOMECHANICAL ANALYSISANALYSIS


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THERMOMECHANICAL THERMOMECHANICAL CALCULATIONSCALCULATIONS

How to evacuate heat and allow free expansion …How to evacuate heat and allow free expansion …

kCu

kG

RMS Roughness

Rq

Mean Asperity Slope

a

P

P

EG

935.03.2

49.1)(

aGq

aSc E

PRk

Ph

• Less than 1% of the interface surfaces is usually in contact …Less than 1% of the interface surfaces is usually in contact …• Pressure is necessary to increase the effective contact surface …Pressure is necessary to increase the effective contact surface …• Thermal conductance might be evaluated analytically Thermal conductance might be evaluated analytically


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How to minimize thermal deformations …How to minimize thermal deformations …

M1

M3

M2

u”u”ii==T/BT/B

=u”L=u”L22/8/8

T

… the principle of compensation is used


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FEM Model for 3-D analysisFEM Model for 3-D analysis

Geom. B.C.: Hinged + Free

expansion

Contact elem. (friction + therm.

Conductance) Preloaded Springs (5 bar)

Convection (12360W/m2/K) + inlet temp. (27ºC)

Temperature - dependent Temperature - dependent properties (when available)properties (when available)

Deposited Heat Power (W/m3)


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Remarks on jaw materialsRemarks on jaw materials Several materials were analyzed for the Several materials were analyzed for the

jaws:jaws:– Snecma NB31 3-d C/C (Y max X min)Snecma NB31 3-d C/C (Y max X min)

– Snecma NB31 3-d C/C (Z max Y min)Snecma NB31 3-d C/C (Z max Y min)

– SGL C1001 2-d C/CSGL C1001 2-d C/C

– Tatsuno AC150 2-d C/C Tatsuno AC150 2-d C/C

– SGL R4550 “isotropic” graphiteSGL R4550 “isotropic” graphite

Out of these only AC150 and R4550 were Out of these only AC150 and R4550 were retained since they present the best retained since they present the best compromise in terms of deformations, compromise in terms of deformations, strength and availability. strength and availability.


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Thermal analysisThermal analysisNominal Conditions 7 TeV 8e10 p/s Steady-state (p=5 bar)Nominal Conditions 7 TeV 8e10 p/s Steady-state (p=5 bar)

2-D C/C AC150 TMax 47ºC

Graphite R4550 TMax 51ºC


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Displacement analysisDisplacement analysisNominal Conditions 7 TeV 8e10 p/s Steady-stateNominal Conditions 7 TeV 8e10 p/s Steady-state

2-D C/C AC150 Max≈20m

Graphite R4550 Max≈14m


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Displacement analysisDisplacement analysisNominal Conditions 7 TeV 4e11 p/s Transient (after 10s)Nominal Conditions 7 TeV 4e11 p/s Transient (after 10s)To be confirmedTo be confirmed

2-D C/C AC150 Max≈30m

Graphite R4550 Max≈47m


2020


Stress AnalysisStress AnalysisNominal Conditions 7 TeV 8e10 p/s steady-stateNominal Conditions 7 TeV 8e10 p/s steady-state

2-D C/C AC150 Max≈7.8MPa

Graphite R4550 Max≈5.8MPa


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Stress Analysis Stress Analysis Accident case 7 TeV 9.1e11 p (200 ns)Accident case 7 TeV 9.1e11 p (200 ns)

AC150 Tmax= 724º R4550 Tmax= 698º

Courtesy A. Dallocchio


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Notes: R=adm(1-)/E


Load case summaryLoad case summary

Material

Min. Flexural Strength

(MPa)

R (Therm Shock

Ind.) ºC

T max (ºC)

Max

( m)

Max (MPa)

T max (ºC)

Max

( m)

Max (MPa)

T max (ºC)

Principal stress(MPa)

SGL R4550Graphite

60 1100 51 16 5.8 70 47 9.9 697 +20.8

AC150C/C Short Fibre

130? 818 47 20 7.8 72 30 9.8 756 +57.7

C10012D C/C

110 740 48 11 14.9 76 94 14.9 821 -

Snecma NB31C/C 3D (Ymax

(70?) 3400 45 78 16.3 - - - 651 -

Properties

7TeV Accident (9,1e11p 200ns

0mm offset)

Load Case

TCS-B2 (from TCPS) 0,8e11 p/s (steady-state)

TCS-B2 (from TCPS) 4e11 p/s (10s)

to be confirmed!


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Based on the given requirements, technical layout is a mix between traditional and new solutions …

Mechanical design was finalized … Feasibility confirmed by prototype manufacturing

… Extensive thermo-mechanical analyses results

predict that tough specification should be attained within reasonable limits, …

… provided available data are correct (material characterization results are forthcoming) …

… and new Fluka simulations confirm previous loads.

In nominal conditions stresses are well below the limits.

Special attention must be given to accident scenarios, where stresses come close to admissible limits … (see O. Aberle talk)

CONCLUSIONSCONCLUSIONS

Documents

01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 1 CERN European Organization for Nuclear Research Mechanical Engineering and Thermo-mechanical