laser interferometer gravitational-wave observatory 1 stefano tirelli undergraduate student...
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![Page 1: Laser Interferometer Gravitational-Wave Observatory 1 Stefano Tirelli Undergraduate student University of Pisa Italy LIGO-G020441-00-R Stress-strain behaviour](https://reader036.vdocuments.site/reader036/viewer/2022062322/5697bf831a28abf838c86871/html5/thumbnails/1.jpg)
Laser Interferometer Gravitational-Wave Observatory 1
Stefano TirelliUndergraduate student
University of PisaItaly
LIGO-G020441-00-R
Stress-strain behaviour of MoRuB glassy metals
ChenYang WangGraduate Student
CaltechNow at University of Stanford
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LIGO Laboratory at Caltech 2
Physical properties studied
• Young’s Modulus• Mechanical hysteresis
• Yield Point• High yield point allows THINNER suspensions and less energy
dissipation
• Structural modifications• Shear bands
• Crack propagation (upcoming)
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LIGO Laboratory at Caltech 3
How to study stress/strain of MoRuB?
Load frame and cell courtesy of Robert Rogan, Materials Science
Load frame, operational setup
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LIGO Laboratory at Caltech 4
How to measure stress?
Micro Load Cell, maximum load 1000lbs (oversized!)
Wheatstone-bridge based
Present resolution ~ 50 grams
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LIGO Laboratory at Caltech 5
How to measure strain?
LVDT: Linear Variable Differential Transformer
Custom designed micro-LVDT and holders
Differential measurement = high resolution, rejection of noise
Current flow
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LIGO Laboratory at Caltech 6
Linear response:
Present resolution: 15nm
-4
-3
-2
-1
0
1
2
3
3 4 5 6 7 8 9 10 11
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
4.7 4.9 5.1 5.3 5.5 5.7 5.9 6.1
Displacement (mm)1mm
1 V
olt
Vo
lta
ge
(V
olt
s)
Linear regime:
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LIGO Laboratory at Caltech 7
The stress/strain chart
The stress\strain chart give us a clear picture of many properties of the material:
Slope: Young’s modulus
Breaking point
Plastic deformation(not present in Glassy metals)
Yield point
Ductile deformation(not present in Glassy metals)
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LIGO Laboratory at Caltech 8
Stress/strain chart for MoRuB
First cycles: low load
Non-rigidity of the system
Hysteresis NOT due to sample
Sample tested:Mo50.4Ru33.6B16
Cross section:3.3mm x 50um
Displacement (microns)
Lo
ad
(K
g)
Stress = load * g * 1/cross-section
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LIGO Laboratory at Caltech 9
Stress/strain curves for MoRuB
Crack formation
Material hysteresis
Permanent deformationNo breakdown failure as in crystals!
Displacement (microns)
Lo
ad
(K
g)
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LIGO Laboratory at Caltech 10
Why low values for yield point?
Young’s modulus:
Boron 16: 174 GPa
Yield point (lower limit!):
Boron 16: 1.34 Gpa
(upper limit: 5.2GPa)
Non-uniformity of stress: effective cross-section is LOWER than the measured one.Solution: self-aligning swivel holders (already in production):
LVDT Sample holder
Rotating swivel
Two LVDT’s for detecting torsion!
Error: ~15% mainly due to poor thicknessMeasurement. Solution: precision-micrometerUpcoming.
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LIGO Laboratory at Caltech 11
Why low values for yield point?
Nucleation of cracks. To take good measurements we need regular borders without weak point for crack nucleation:
EDM CutLocal meltingPossible formationOf crystals on edges
Scissor cut:Very irregular and unreliable!
Electropolished cut:The best!
Nucleation of cracks causes premature failure of the material!
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LIGO Laboratory at Caltech 12
Structural effects of stress: shear bands
Shear bands
Details of a MoRuB brokensample
Who knows about shear bands? I don’t, but they’re nice.
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LIGO Laboratory at Caltech 13
What needs to be done:
•Testing on electropolished samples to obtain a value close to the one calculated by Vicker hardness test (5.2GPa).
•Study of crack propagation.
•Poisson’s modulus.
•Observation of shear bands during formations: load frame is designed to fit into an SEM casing.
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LIGO Laboratory at Caltech 14
Thanks to
Riccardo DeSalvo - Mentor
Prof. Francesco Fidecaro - University of Pisa
ChenYang Wang - Graduate Student, LabMateHareem Tariq - Graduate Student
Prof. William Johnson
Robert Rogan - Materials ScienceMichael HallBrian EmmersonEric KortMaddalena MantovaniBarbara Simoni