a monolithic tensile tester fabricated and fully operated by a femtosecond laser
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Design of a Monolithic Tensile Tester Fabricated and Fully Operated by a
Femtosecond Laser
C.E. Athanasiou, B. McMillen, Y. Bellouard
Mechanical Engineering Department
Eindhoven University of Technology, the Netherlands
Galatea Towards The Monolithic Integration Goal
Turning a single piece of material into a system by locally tailoring its
microstructure?
2
Fused silica (a-Si02)
3
Awazu et al, Appl. Phys. 94, 6243-6262 (2003)
(μicro)mechanics of Silica?
• Ultimate Tensile Stress of a-SiO2 Nanowires >10 GPa.
• Dependence of silica’s young modulus from surfaceeffects
• Under shear stress plastic deformation occurs
• Nanoscale plastic flow for high bending strengths
*Brambilla et al., Nano Lett. 9, 831-835(2009).
*Zheng et al., J Mater Sci. 42, 191-198 (2007)
*Rountree et al., ARL. 102, 195501 (2009)
*Bellouard, Opt. Mat. Express 5, 816-831 (2011)
The motivation…
5
Capabilities of a Femtosecond Laser
6
Design of a Monolithic Tensile Tester fabricated and fully operated by a
femtosecond laser
How does a Tensile Tester Works?
A sample is subjected to controlled tension until failure
7
Brittle Failure Ductile Failure
Strain Hardening
Regime
σ
ε
σ
ε
Beam Under
Test
How to perform a tensile test on micro-/nano- scale
specimens?
Requirements for a micro tensile tester for silica polymorphs
8
• A fabrication method
• A loading tool
• Strain measurements
• Measurement of the stress
Femtosecond laser processing
Femtosecond laser induced volume expansion
Third Harmonic Generation Metrology
Birefringence Measurements
Fabrication methods for the micro-/nano- tensile test
Yb Fiber Amplified Laser System~270 fs pulses, 800 kHz rep-rate,low-pulse energy (200 nJ)
9
Chemical Etching
Y. Bellouard et al, Optics Express, 12, 2120-2129 (2004)
Etching in low concentration HF bath
Femtosecond Laser Exposure (no ablation)
Laser induced controlled deformations in silica
By writing adjacent planes in the bulk of the material the stress of the tensile tester can be tuned!
10
A. Champion et al., Opt. Mat. Express 2, 165240 (2012)
The Tensile Tester
11
Part aLoading
Cell
Bars 1,2: UndergoVolume
Expansion
Bar 3: Beam underTest
Part bDisplacement Amplification
Sensor
Point C: Remote
Center of Rotation
Ground
σ=Εε
12
20um1mm
20um
Measured Stress
280 MPa.
Loading the Tester
13SEM picture of the fabricated mechanism
Measured elongation after machining planesEnergy per pulse 300nJ@ 800KHz rep rate
3mm
1 1
1mm
A
B
Points A, B are the centers of rotation of thetwo stage compliant mechanism
A
B
Loading vs. Stressors
14
Modeling the Loading Cell
15
Modeling vs. Experiment
16
17
Reference Surface
Undesired out of plane motion
9um
2mm
Third Harmonic Generation as an In-Situ Characterization Tool
18
SiO2
ωn1,χ2
n2,χ1
• Weak process that occurs in all materials
• Surface-enhanced phenomenon
• When using focused ultrashortpulses the process is highlyoperative
T. Thomas, Physical Review A, 5, 4116–25 (1995)
3ω
Femtopulses Crossing an SiO2 Interface
19
SiO2
Subsurface Edge Detection?
20
SiO2Air
Subsurface Edge Detection?
21
Subsurface Edge Detection?
22
Subsurface Edge Detection?
23
Subsurface Edge Detection?
24
25
Subsurface Edge Detection?
SiO2 Air
Results & Perspectives
• The same femtosecond laser can be used for thefabrication, loading and dynamical characterizationof a micro tensile tester
• THG can be used for (sub)surface in-situ edgedetection in the micro scale
• Tool for characterizing silica’s polymorphic phases
C.E Athanasiou, B. McMillen, Y. Bellouard
Acknowledgements
27C.E. Athanasiou, B. McMillen, Y. Bellouard
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