01.07.2004 a. bertarelli – r. perret cern ts – mme group 1 cern european organization for...
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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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THERMOMECHANICAL THERMOMECHANICAL CALCULATIONSCALCULATIONS
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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THERMOMECHANICAL THERMOMECHANICAL CALCULATIONSCALCULATIONS
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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THERMOMECHANICAL THERMOMECHANICAL CALCULATIONSCALCULATIONS
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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THERMOMECHANICAL THERMOMECHANICAL CALCULATIONSCALCULATIONS
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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THERMOMECHANICAL THERMOMECHANICAL CALCULATIONSCALCULATIONS
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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THERMOMECHANICAL THERMOMECHANICAL CALCULATIONSCALCULATIONS
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
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THERMOMECHANICAL THERMOMECHANICAL CALCULATIONSCALCULATIONS
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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THERMOMECHANICAL THERMOMECHANICAL CALCULATIONSCALCULATIONS
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
THERMOMECHANICAL THERMOMECHANICAL CALCULATIONSCALCULATIONS
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