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)