Post on 29-Jan-2016
transcript
Micro-valve
Estimated Time for Completion: ~30minExperience Level: Lower
MSC.Patran 2005 r2MSC.Marc 2005 r2
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Topics Covered
• Topics covered in Modeling• Importing Geometry file with FEA data.
• Neutral format (.out)
• Creating Non Spatial Fields by Tabular Input.
• Specify the time dependent temperature input.
• Applying Initial and Final Temperature
• Increase Temperature by multiplying the final temperature and the temperature scaling factors.
• Topic covered in Analysis• Applying Large Displacement/Large Strains Analysis.
• Applying Coupled (Thermal-Mechanical) Analysis
• Topics covered in Review• Creating XY plots
• Load vs. Displacement plot
• Animation
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• Thermal actuators are very popular actuators in MEMS. This example demonstrates the thermal-mechanical coupled problem. A micro-valve is actuated by increasing the temperature of the structure
Problem Description
Close at Initial temperature, Ti
Open at Final temperature, Tf=Ti+ΔT
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Problem Description
• Given Parameters• Dimensions
• Size : 16mm x 0.83mm
• Thin layer thickness= 30μm
• Material properties (μMKS units)
• Simplifying the problem• To apply the symmetric condition, the rotation at the center is fixed.
Nickel: t=30μm
Silicon: t=30μm 0.4mm
0.4mm
8mm
Bonded (Nickel&Silicon)
Bonded (Si&Si)Not Bonded
Properties Silicon Nickel
Young’s Modulus (MPa) 190e3 200e3
Poisson’s Ratio 0.26 0.3
Density (kg/μm3) 2.330e-15 8.930e-15
Thermal Expansion Coeff. (1/K) 0.23e-5 0.3e-5
Thermal Conductivity (pW/μmK) 157e6 80e6
Specific Heat (pJ/kgK) 7.53e14 4.55e14
Yield/Fracture Stress (MPa) 6e3 0.23e3
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Goal
• Find the displacement vs. temperature plot at the center of the valve. What is the minimum ΔT for the required displacement, 100μm?
• Find the location and value of the maximum stress during the loading (increasing temperature) process. From the stress analysis, find the maximum operating ΔT.
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Expected Results
Initial at T=0
Deformed at T=100
• Deformation
• Stress
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Create Database file and Import Geometry
• Create a New Database file called ‘microvalve.db’
• Use Marc as the analysis Code
• Select Coupled as the Analysis Type
• Import the Neutral Geometry file called ‘microvalve.out’, and Node and element information will be imported.
Imported elements and nodes
Maximum dimension is about 8000μm
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Create Nonspatial Field
• Create a time dependent Nonspatial Field called Temp_time
• Map f=t to generate Field Table
• This will increase the temperature from initial to the final values
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Load Case
• Defined a Time Dependent Load Case called IncreasingTempCase.
• To define the time dependent Load/BCs, a time dependent Load Case must be defined first.
Make sure the current Load Case is time
dependent.This can be automatically
done by turning the checkbox on
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Boundary Conditions
• Displacement Constraints• Fixed_x
• This will prevent the right end of the structure from moving to x-direction.
• Fixed_y• This will prevent the bottom of the structure from
moving to y-direction.• Sym
• Symmetric boundary condition.
• Initial Temperature• Temp_initial
• Temp (Thermal) : time dependent• Temp_increase
Fixed_x
Temp_Initial
Temp_increase
sym
Fixed_y
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Boundary Conditions
• Deformable Contact Bodies• Create four deformable bodies
• Glue condition will be applied to the following pairs
• Nickel & Si_up
• Si_anch & Si_low
Nickel
Si_up
Si_low
Si_anch
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Materials
• Material properties• To simplify, apply isotropic properties to the Crystal Silicon.
• Use μMKS units.
Silicon Nickel
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Properties
• Element Properties• Create 2D Solid properties
called Nickel_prop and Si_prop
• Nickel_prop
• Material Name: Nickel
• Thickness: 3mm
• Si_prop
• Material Name: Silicon
• Thickness: 3mm
Si_prop
Nickel_prop
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Load Cases
• Modify the previously defined Load Case• Name: IncreasingTempCase
• Apply following BCs/Load• Displacement
• Fixed_x
• Fixed_y
• Sym
• Temperature
• Temp_initial
• Temp_increase
• Contact
• Nickel
• Si_anch
• Si_up
• Si_low
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Analysis
• Single Load Steps• Name: IncreasingTempStep• Load Case selected: IncreasingTempCase
• Solving Options• Large Displacement/Large Strain• Fixed Increment Type
• Initial Time Step Size : 1.0• Total Time : 1.0
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Review Results
• Select the reference information• Reference nodes to review the
displacement and stress results
• Reference increment to compare the results based on time (load factor) and increment (solving step)
Reference node forthe displacement axis
Reference nodes forthe von-Mises stress
Reference increments forLoading and unloading results:
Select the increment resultswith the time increasing.
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Results
• Temperature vs. displacement Curve• The valve cap moves upward about 160μm when ΔT
increases to 100K. • For the required opening (100μm), ΔT must be at least 52K.
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Results
• Stress Analysis• Von Mises stress in Nickel
• The maximum value is about 300MPa > Yield Stress of• Maximum principal stress in Crystal Silicon
• The maximum value is about 225MPa << Fractural Stress• Maximum operating ΔT is about 56K.
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Animation (Displacement_uy)