THEORETICAL ANALYSIS AND AN EXPERIMENTAL CHARACTERIZATION OF A
HEAT PIPE
Kinematic Mounting Scheme of Miniature Precision Elements for
Mission Survivability against Externally Imposed Environmental
ConditionsPREPARED BY :ANKITKUMAR P. SARVAIYAM.TECH
(CAD/CAM)09CAD14GANPAT UNIVERSITYGUIDED BY:PROF. D. M.
PATELMECHANICAL ENGG. DEPT.,U.V.PATEL COLEEGE OF ENGG., GANPAT
UNIVERSITY, KHERVA
GUIDED BY:MR. J. T. DESAISCI /ENGG, HEAD,
LPMDOPMG,MESA,SACISROAHMEDABAD
1
Presentation Outline
Introduction Literature ReviewDesign of Kinematic MountActual
Testing and RealizationConclusion Future WorkReferences
2
1. IntroductionSpace craft
A spacecraft is designed to leave Earth's atmosphere and operate
beyond the surface of the Earth in outer space. Spacecrafts are
designed for a variety of missions which may include
communications, earth observations, navigation, planetary
explorations, scientific research, and so on.Spacecraft Typical
Subsystems like Attitude control, Payloads, Launch vehicle etc.
Payload
The payload is dependent upon the mission of the spacecraft,
Typical payloads could include scientific instruments (cameras,
telescopes, or particle detectors, etc.).
Remote sensing payload
The remote sensing component of the programme, in particular,
has successfully achieved global acceptance. Operational satellites
have been indigenously built and launched, which cater to land and
ocean applications.There are numbers of elements for imaging,
sensing etc. in remote sensing payload.
Telescope
A telescope is an instrument designed for the observation of
remote objects.
Camera Structure
Filters:
To have single collecting optics for all 4 bands and use
appropriate spectral separation system for band selection.To use
separate collecting optics for each band
Types of FiltersLow Pass Filter- Passes low-frequency signals
but attenuates signals.High Pass Filter- Passes high frequencies
well but attenuates frequencies lower than the filter's cutoff
frequency.Band Pass Filter- Band pass filter are uses to pass these
4 bands, every band has a specific spectrum.
Kinematic mount
Kinematic Mount are widely used to minimize the deformation of
optical elements caused by Kinematic mount induced stresses.
Kinematic mount uses the principle of kinematic theory.
Theory of Kinematics
A rigid body in space has 6-DOF, three translations and three
rotations. Kinematic theory assumes that perfectly rigid bodies
contact only at infinitesimal points.The application of kinematic
theory consists of selecting no more than six contact points to
provide the type of support or motion required.
Flexure:
Definition of Flexure:
Flexure is usually considered to be a mechanism of a series of
rigid bodies conducted by compliant elements that is designed to
produced a geometrical well defined motion upon application of
forceOr Flexure is an elastic element which provides controlled
motion
2. Literature Review
Advantages:
It must exert low force on the optical element to minimize
optical surface distortion.The mount must be such that a thermal
changes in temperature must not degrade the optical surface or
change the position of the optical element.It must maintain the
position of the optical element throughout its assigned life
time.Mounting fabrication and material cost should be as low as
possible.
Flexure Elements:
Flexure device consist of compliant elements that connect rigid
bodies to from a mechanism.Types of Flexure Elements
Types of Notch JointsCompliant JointCompliant Notch Universal
JointCruciform Joint
Material Selection:
Compliance of an individual flexure depends of the shape and
flexure material.Stability of flexure material with respect to time
so its important for maintaining alignment of optical
element.Dimensional stability of flexure is controlled by choice of
material.Another consideration, thermal properties of flexure
material- good matching between CTE of flexure and optical
element.
Test on Vibration Shaker:
11
Sinusoidal Vibration Test
Sine vibration testing is used to find out natural frequencies,
peak value of acceleration.
Random Vibration Test
Many vibration environment are not related to a specific
deriving frequency and may have input from multiple sources which
may not be harmonically related. Unlike Sine vibration,
acceleration, velocity & displacement are not directly related
by any specific frequency. Primary concern in Random testing is the
complete spectral content of the vibration being measured.
12
3. Design of Kinematic MountIntroductionDesign StepsCAD
modelsStructural Analysis of Assembly
IntroductionKinematic mount is monolithic part. The mount needs
to be designed to perform satisfactorily without losing its
alignment. The mount itself has to avoid deformation of the mounted
optics. Kinematic mount is to be made by incorporating different
types of flexures in this design.Kinematic mount following the
cantilever principle, a large mount allows finer control than a
smaller one.
Design Steps
1) Identification of NeedFilters need to be housed in mechanical
assembly to give them support as well as to maintain separation
between different optical elements under the application of loads.
Need arises to design to this mechanical element.
2) Definition of ProblemTo design mechanical support for
supporting optical elements like band pass filter in such a way
that it will sustain different loads and the optical elements will
perform satisfactorily under this load.
Goals:
Supporting optical element and maintaining its position relative
to other optical elements in an optical system.Design has to be
such a way that to sustain gravity loads and changing temperature
conditions in space, sine and random vibrations.
Loads and boundary conditions :Loads
Inertial load: 100g, 200g (gravity load) individually in all
axes as per requirement.Temperature: 40c excursion load.Sine loads,
Random loads as per below table
Qualification Levels(ii) Sine Vibration loads(iii) Random
Vibration loadsDirectionIn PlaneOut of PlaneDirectionIn PlaneOut of
PlaneFrequency(Hz)Amplitude at Qualification LevelAmplitude at
Qualification LevelFrequency (Hz)Qualification LevelQualification
Level5 164.85 mm9.7 mm20 100+3 dB/Oct+3 dB/Oct16 505 g10 g100 -
7000.1g2 / Hz0.2 g2 / Hz50 803 g6 g700 2000- 3 dB/ Oct- 6 dB/ Oct80
- 1003g3 gOverall g rms11.89 rms14.8 rmsRate & Duration2
Oct/min2 Oct/minDuration2 minutes2 minutes
Boundary conditions:
Mount should have 2 fixing holes at the end.
Specifications:
Mount design to hold optical elements having sizes: 85x10x2,
30x20x1and 30x20x3 mm3.Filter material: NBK-7, fused silica (glass
material).Mount should be made with optimum size (approaching close
to filter size) and minimum mass as possible.
3) SynthesisThis is the most important step in the designing.
Here are various schemes for designing of kinematic mount.
Kinematic mount is made by using different types of thin sections.
These thin sections are called flexures. Cross strip,Notch joints
(Square, Circular, Elliptical), Cruciform flexure etc.
Material selection for mount:
Sufficient flexibility of mount should be made up from material
which has low stiffness.Difference between CTE (co-efficient of
thermal expansion) of filter material and mount material should be
as minimum as possible.Mount material should have sufficient
strength so that it should not fail under the action of different
loads.The mount material should be dimensionally stable over a
period of time.Flexures will be having complicated geometry and the
material should have good machinability.
4) Analysis and OptimizationAnalysis of the mount gives the
results in frequencies, stress, acceleration and displacement. Here
, Two types of analysisStatic Analysis
Dynamic Analysis
Natural FrequencyAnalysisFrequency ResponseAnalysisRandom
ResponseAnalysisDynamic AnalysisStatic AnalysisInertial
loadTemperature load
6) PresentationEvaluation is the final proof of a successful
design and usually involves the testing of a prototype.
5) EvaluationA brief summary is presented which involves
different steps in the process as well as final results obtained
from the analysis and testing.
Option-1
CAD Models (Different options for mount design)
For Filter size:- 85x10x2
For Filter size:- 30x20x3
For Filter size:- 30x20x1
Option-2
For Filter size:- 85x10x2
Assembly view
For Filter size:- 30x20x1
For Filter size:- 30x20x3
Option-3
For Filter size:- 85x10x2
For Filter size:- 30x20x1
For Filter size:- 30x20x3
Option-4
For Filter size:- 85x10x2
Assembly view
Structural Analysis of AssemblyAnalysis means examination of the
different components or elements that make up an assembly, to
discover their interrelationships and relative importance in the
realization of its goals or purpose.
Basically in analysis three steps are involved1) Pre
Processing2) Processing3) Post Processing
Pre-Processing:
Meshing:Meshing is performed to discretize the geometry created
into small pieces called elements.
FE model of Mount:Option -2
Option -4
Loads and Boundary Condition:Loads: Inertial, temperature, sine
& random vibration loads
Boundary conditions:
Fixing point
Processing:
Import the model for processing which is exported from
Pre-processor.
Two types of analysis has been carried out
1) Static analysis
2) Dynamic analysis
Post- Processing:
After completion of analysis solver generates result files.
Viewing and Interpretation of Results:
Before looking the results the terms Von-Mises and Max.
Principal are as follows.
Von-Mises Stress: Ductile material fails at a plane inclined 45
to axis of loading. Normal stress not act on this plane so this
theory is best for ductile material.
Max.Principal:Failure of brittle material subjected to uniaxial
test is along a plane to perpendicular to axis of loading. So this
theory is best for brittle material.
Case-1 : Inertial Load of 100g & 200g
Inertial loading analysis is done to analyses strength of the
structure during its flight.
Stresses due to Inertial Load
Option-2Band Pass Filter assemblyComponent Stress (MPa) value at
200 g Inertial loadFilter ( Max Principal)9.22.293.23Mount (Von
Mises)39.613.050.9Adhesive14.73.0911.5
Stress on filter ( Max. Principal)Stress on Mount ( Von
Mises)Stress CountersThis results shown only Yaw axis results
because yaw axis is critical axis for analysis
Option-4Band Pass Filter assemblyComponent Stress (MPa) value at
100 g Inertial loadFilter ( Max Principal)2.881.440.84Mount (Von
Mises)8.648.162.96Adhesive2.481.590.76
Stress Counters
Stress on filter ( Max. Principal)
Stress on Mount ( Von Mises)
This results shown only Yaw axis results because yaw axis is
critical axis for analysis
Case-2 : Temperature Load (T= 40c)
Temperature loading analysis is done to measure the strength of
structure under temperature difference. During in-orbit operation
of payload, some faces see the sun side and experiences radiation
from the sun.
Stresses due to Temperature Load
Option-2Band Pass Filter assemblyComponent Stress (MPa) on
Temperature changeT=40C Filter ( Max Principal)4.35Mount (Von
Mises)51.3Adhesive5.75
Stress Counters
Stress on filter ( Max. Principal)Stress on Mount ( Von
Mises)
Option-4Band Pass Filter assemblyComponent Stress (MPa) on
Temperature changeT=40C Filter ( Max Principal)13.2Mount (Von
Mises)36Adhesive12.4
Stress Counters
Stress on Mount ( Von Mises)Stress on filter ( Max.
Principal)
Case-3 : Normal Mode Analysis
Normal mode analysis is done for finding out normal mode shapes
and frequencies for final configured models to be tested on
vibration shaker. It determines the natural (resonant) frequency
and mode shapes of the structure.
Results of Normal Modes:
Only flexure modes are important because its shows the behavior
of mount and shows the acceleration of filter also.
Normal Mode AnalysisOption-2
First mode: 885.1 HzFilter has translation in out of plane.
Flexure worked as a cantilever beam.
Frequency (Hz)ModeNastran ( Theoretical )First mode885.1Second
mode1597.2Flexure in plane mode2141
Second mode: 1597.2 HzFlexure will flex in plane direction
Third mode: 2141 Hz
Option-4
First mode: 885.1 HzFilter has translation in out of plane.
Flexure worked as a cantilever beam.
Frequency (Hz)ModeNastran ( Theoretical )First mode985.27Local
mode of mount1519.5Second mode2030Flexure in plane mode2036
Local mode of mount: 1519.5 Hz
Second mode: 2030 Hz
Flexure in plane mode: 2036Hz
Case-4: Frequency Response
Frequency response analysis is done to simulate the response at
different locations of the job for given acceleration Critical
damping factor is most unpredicted term of the frequency response
analysis.Critical damping factor is most unpredicted term. It
depends on many parameters like material, shape, no. of joints in
the structure etc). It is difficult to evaluate damping factor
theoretically. Hence, to determine damping factor, low level Sine
test of Band Pass filter assembly was carried out. Damping factor
is calculated by half power bandwidth method
Damping factor () = 1/2*Dynamic magnification factor (Q)
Derived dynamic magnification factor (Q) for BP filter mount
assembly are shown in following.
Option-2
Option-4
Yaw axisFrequency (Hz)Q92918
Yaw axisFrequency (Hz)Q101019.61570116
Results of Frequency Response Analysis
Option-2 Input level of 1mm/s2 for 10Hz-2000Hz
TheoreticalExperimentalFrequency (Hz)885929Response
(g/g)30.4627.11
Sine Response at middle of the filter
Acceleration V/s Frequency
Theoretical value of stress
At 1st freq stress is 0.00127 x 10-5 MPa for input of 1
mm/s2Calculation: 0.00127 x 10-5 *9810*0.5= 0.622 MPaExperimental
value of stress
Strain is 15.4 x 10-6Stress = E* = (0.82x105) x (8.35 x 10-6) =
0.684 MPa
TheoreticalExperimentalFrequency (Hz)885929Stress
(MPa)0.6220.684
Stress middle of filter
Stress vs. Frequency
Option-4Input level of 1mm/s2 for 10Hz-2000Hz
TheoreticalExperimentalFrequency (Hz)9851010Response
(g/g)24.120.55
Sine Response at middle of the filter
Acceleration V/s Frequency
Theoretical value of stress
At 1st freq stress is 9.3 x 10-5 MPa for input of 1
mm/s2Calculation: 9.3 x 10-5 *9810*0.5= 0.456 MPaExperimental value
of stress
Strain is 6.78 x 10-6Stress = E* = (0.73x105) x (6.78 x 10-6) =
0.495 MPa
TheoreticalExperimentalFrequency (Hz)9851010Stress
(MPa)0.4560.495
Stress middle of filter
Case-5: Random Response
Random response analysis is the same analysis that performed as
the random vibration test on vibration shaker. This is the most
effective step towards the measurement of vibration
characteristics. This analysis takes input from the result of
frequency response analysis. So it's a dependable analysis. Along
with above input, this analysis requires power spectral density
(PSD) level for the frequency range to be tested.
Results of Random Response Analysis
Option-2
TheoreticalExperimentalInput level(gRMS) at mounting
I/P14.814.8Response at middle of filter (gRMS)96.3164.83
Random Response at middle of Filter due to Random Qualification
load
Response (g2/Hz) V/s Frequency
TheoreticalExperimentalFilter (Max. Prin.)
MPa2.9439.86*10-6*0.82*105 = 3.28Mount (Von Mises) MPa8.5-Adhesive
MPa3.31-
Stress (rms) at middle of filter due to Random Qualification
load
Response (stress2/Hz) V/s Frequency
Stress counter for stress (rms) due to Random Qualification
loadStress on filter 2.94 MPaStress on Mount 8.5 MPa
Option-4
TheoreticalExperimentalInput level(gRMS) at mounting
I/P14.814.8Response at middle of filter (gRMS)71.863.93
Random Response at middle of Filter due to Random Qualification
load
Response (g2/Hz) V/s Frequency
TheoreticalExperimentalFilter (Max. Prin.)
MPa2.9345.07*10-6*0.73*105 = 3.29Mount (Von Mises) MPa2.56-Adhesive
MPa1.2-
Stress (rms) at middle of filter due to Random Qualification
load
Response (stress2/Hz) V/s Frequency
Stress counter for stress (rms) due to Random Qualification
load
Stress on filter 2.93 MPaStress on Mount 2.56 MPa
4. Actual Testing and RealizationActual test is performed by
vibration testing of band pass filter assembly on vibration
shaker.
Purpose of Testing
This test has basic purpose of evaluating the behavior of filter
assembly to the actual launch environment that is simulated during
testing.
The set up consists of Shaker Fixture BP filter assembly Spacer
Accelerometers Strain gauges
Test Configuration
Requirements to measure Acceleration and StrainAccelerometerIt
is a piezoelectric transducer used to convert the kinetic energy
into an electrical signal. One accelerometer is used in the test.
Its mass was 1 gram.Strain GaugeA strain gauge is used to measure
the strain of an object. The gauge is attached to the object by a
suitable adhesive. Strain gauge measure the strain of filter in
terms of mst (micro strain). One strain gauge is used in the
test.
Location of Accelerometer and Strain gauge
Location of Accelerometer (Tri axial)Location of strain
gaugeActual locations of Accelerometer and Strain gauge for testing
(option-4)
Test Sequence
Low Level Sine test (LLS) Sine qualification test (SQ)Post SQ
LLSLow Level Random (LLR)Random Qualification test (RQ) Post RQ
LLS
Test Results ( option-4)Yaw axisYaw axis Test Set up
Yaw axis Test Results Band pass filter assemblyPre SQ LLS(I/P=
0.5g)Freq (Hz)10101570g/g19.915Micro strain6.788.43Post SQ LLS(I/P
= 0.5 g)Freq (Hz)10101570g/g19.514.6Micro
strain6.538.16LLRI/P=1.48ggRMS5.79Micro Strain RMS4.135RAI/P=
10.52ggRMS42.9Micro Strain RMS30.31RQ(Qualification)I/P=14.8
ggRMS63.93Micro Strain RMS45.07Post RQ LLR(I/P= 0.5g
)g/g10301570Micro strain16.613Freq (Hz)5.586.97
Roll axisRoll axis Test Set up
Roll axis Test Results Band pass filter assemblyPre SQ LLS(I/P=
0.5g )Freq9541460g/g9.8612.8LLR
(I/P=1.17g)gRMS4.285gRQ(Qualification)(I/P 11.77
gRMS)gRMS46.11gPost RQ LLR(I/P= 0.5g )Freq9541460g/g10.915.1
Pitch axisPitch axis Test Set up
Pitch axis Test Results Band pass filter assemblyPre SQ LLS(I/P=
0.5g )Freq16401530g/g3.741.76LLR (I/P 1.17
gRMS)gRMS1.502g1.34gRQ(Qualification)(I/P 11.77
gRMS)gRMS14.9g13.45gPost RQ LLS(I/P= 0.5g
)Freq16501530g/g3.781.72
Comparison of Theoretical and Experimental data of Band Pass
Filter AssemblyIn actual test, accelerometer & strain gauge are
present; hence their masses are considered. So in theoretical
analysis, I have to add those masses and so my analysis is done
with consideration of these masses. In theoretical analysis,
accelerometer has been simulated as a lumped mass.
Low level Sine Response
Comparison of Frequency Response during LLS
Sine Response at middle of Filter
TheoreticalExperimentalFrequency (Hz)9851010Response
(g/g)24.120.55
Comparison of Stress during Low Level Sine Test
Stress at middle of Filter TheoreticalExperimentalFrequency
(Hz)9851010Stress (MPa)0.4560.495
Low Level Random Response
Comparison of Random Vibration Qualification Response
Random Response at middle of Filter due to Random Qualification
LoadTheoreticalExperimentalInput level (gRMS) at mounting
I/P14.814.8Response at middle of filter (gRMS)71.863.93
Comparison of Stress during Random Vibration Qualification
Stress (rms) at middle of filter due to Random Qualification
LoadComponentTheoreticalExperimentalFilter (Max. prin.)
MPa2.933.29
Testing of Option-2
Yaw axis test set up
Yaw axis test dataBand pass filter assemblyPre SQ LLS(I/P=
0.5g)Freq (Hz)929g/g27Micro strain8.35Post SQ LLS(I/P = 0.5 g)Freq
(Hz)929g/g26.1Micro strain8.04LLRI/P=1.48ggRMS929Micro Strain
RMS4.347RAI/P= 10.52ggRMS932Micro Strain
RMS28.45RQ(Qualification)I/P=14.8 ggRMS932Micro Strain RMS39.86Post
RQ LLR(I/P= 0.5g )g/g28.3Micro strain8.84Freq (Hz)929
Comparison of Theoretical and Experimental data of Band Pass
Filter Assembly Low level Sine Response
TheoreticalExperimentalFrequency (Hz)885929Response
(g/g)30.4627.11
Sine response at the middle of the Filter
Comparison of Frequency Response during LLS
Comparison of Stress during Low Level Sine Test
Stress at middle of Filter TheoreticalExperimentalFrequency
(Hz)885929Stress (MPa)*0.6220.684
Low Level Random Response
Comparison of Random Vibration Qualification Response
Random Response at middle of Filter due to Random Qualification
LoadTheoreticalExperimentalInput level (gRMS) at mounting
I/F14.814.8Response at middle of filter (gRMS)96.3164.83
Comparison of Stress during Random Vibration Qualification
Stress (rms) at middle of filter due to Random Qualification
LoadComponentTheoreticalExperimentalFilter (Max. Prin.)
MPa2.943.28
5. ConclusionThe dissertation establishes a need to develop an
accurate mechanical structure that corrects the deficiencies of the
alignment problem during launching and it's throughout operational
life in orbit. Different types of flexure geometries are evaluated
for making a kinematic mount.
After considering four options, it is realized that option 2 and
option 4 are practically suitable as per the requirements
cited.Further, option 4 is better in comparison to option 2 since
it has satisfies all the design requirements and it has a very good
match of analytical results with its experimental results.Hence,
option 4 can be used for future space projects which are having
similar design criterion.
6. Future WorkPresent work has excluded Opto-mechanical analysis
like finding surface deformations due to different mechanical
loading conditions. This sort of work can be undertaken in future
during integrated payload development.
This design philosophy of the filter mount assembly can also be
applied to other mechanical components holding different optical
elements.
Though the design is made for different mounts having different
materials, actual testing is done only for mounts made from
Aluminum and Invar due to scarcity of time. Mounts from other
materials like titanium, composite materials can be made and can be
tested to know their behavior.
Experimentation of the filter mount assembly can be done by
putting them in thermo-vacuum chamber and subjecting it to designed
temperature excursion loads to know their practical
suitability.
7. ReferencesDr. Jinjun Shan, Assistant Professor of Space
Engineering, ENG 4360 - Payload Design, 1.2 Introduction to Space
Missions.Dr. Jinjun Shan, Assistant Professor of Space Engineering,
ENG 4360 - Payload Design, 2.1 Payload Design and Sizing.Dr. Jinjun
Shan, Assistant Professor of Space Engineering, ENG 4360 - Payload
Design, 4.2 Space Craft Sensors- Introduction to Sensors.George
Joseph and P.D. Bhavsar, Activities at Indian Space Research
Organization (ISRO) on development of space borne remote sensing
sensors.Daniel Vukobratovich and Ralph M. Richard, Flexure Mount
for High Resolution Element, Proc. of SPIE Vol. 0959,
Opto-mechanical and Electro-Optical Design of Industrial Systems,
ed. R J Bieringer, K G Harding (Jan 1988) Copyright SPIE.Daniel
Vukobratovich, Opto-Mechanical Design Principal, 1999 CRC Press,
http://www.engnetbase.comStuart T. Smith. Flexure: Elements of
Elastic Mechanisms. New York, (2000).Brian Trease, Flexures:
lecture summary. Compliant System Design Laboratory The University
of Michigan, April 30 (2004).Chirag Kalariya, M Tech. thesis,
Design, Development and Analysis of Payload Fixation Device for
Space Optical Payload. Department of Mechanical Engineering, Nirma
University, Ahmedabad, May 2010.
http://enpub.fulton.asu.edu/imtl/HTML/Manuals/MC105_Cantilever_Flexure.htm,
accessed on 21st May 2011.Rechard G. Budynas and J. Keith Nisbett,
Shigleys Mechanical Engineering Design, Eighth Edition (2008).Y.
Tian, B. Shirinzadeh, D. Zhang, Y. Zhong, Three Flexure Hinges for
Compliant Mechanism Design based on Dimensionless Graph Analysis,
Science Direct, Precision engineering 34(2010)92-100.3M Scotch Weld
Epoxy Adhesive 2216B/A, Technical Data, December
2009.http://www.colorado.edu/engineering/cas/courses.d/IFEM.d/IFEM.Ch06.d/IFEM.Ch06.pdf,
chapter 6 FEM Modeling: Introduction.Nitin S. Gokhale, Sanjay S.
Deshpande, Sanjeev V Bedekar, Anand N Thite, Practical Finite
Element Analysis, First Edition.Naimesh Patel, J.B.Rami, A.P.Vora,
C.P.Dewan, D.Subrahmanayam, Derived vibration spectrum based
qualification of opto-mechanical subassembly, SSME (Space Society
of Mechanical engineers) Journal of Mechanical Engineering ,Vol.8
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Questions.??
Thank you