Small-scale Approaches to Evaluate the Mechanical Properties of Quasi-brittle Reactor Core Graphite 1 Dong Liu, 1 Peter Heard, 2 Soheil Nakhodchi, 1,3 Peter EJ Flewitt 1 Interface Analysis Centre, School of Physics, University of Bristol, Bristol, BS8 1TL, UK 2 Department of Engineering, University of Bristol, Bristol, BS8 1TR, UK 3 HH Wills Physics Laboratory, University of Bristol, Bristol, BS8 1TL, UK 19 th -20 th September, 2013 1 Symposium on Graphite Testing for Nuclear Applications: the Significance of Test Specimen Volume and Geometry and the Statistical Significance of Test Specimen Population
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Small-scale Approaches to Evaluate the Mechanical Properties of Quasi-brittle Reactor Core Graphite 1 Dong Liu, 1 Peter Heard, 2 Soheil Nakhodchi, 1,3.
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Small-scale Approaches to Evaluate the Mechanical Properties of Quasi-brittle Reactor
Core Graphite
1Dong Liu, 1Peter Heard, 2Soheil Nakhodchi, 1,3Peter EJ Flewitt
1Interface Analysis Centre, School of Physics, University of Bristol, Bristol, BS8 1TL, UK2Department of Engineering, University of Bristol, Bristol, BS8 1TR, UK
3HH Wills Physics Laboratory, University of Bristol, Bristol, BS8 1TL, UK
19th-20th September, 2013
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Symposium on Graphite Testing for Nuclear Applications: the Significance of Test Specimen Volume and Geometry and the Statistical Significance of Test Specimen Population
Symposium on Graphite Testing for Nuclear Applications
Nano-indentation
Experimental and specimens
• Cylinder Gilsocarbon graphite specimen (22 mm dia. x 30 mm thickness)
• Agilent Nano Indenter G200(Culham Centre for Fusion Energy, Materials Facility, UK)
• A square array of 5 x 5 of distributed indents are performed on the flat surface
• Berkovich diamond tip
• Load control with the maximum load of 10 mN and peak hold time of 10 s
• Select specific microstructure features
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19th-20th September, 2013
Symposium on Graphite Testing for Nuclear Applications
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Nano-indentation
Elastic modulus
Gilsocarbon graphite 7.1 - 9.3 GPa
19th-20th September, 2013
Symposium on Graphite Testing for Nuclear Applications
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Summary of data
Materials Elastic modulus (GPa)
Tensile strength Flexural strength
Four-point bending
PGA (virgin) 7.5 ± 0.4 - 13.8 ± 0.6
PGA (irradiated) < 7.5 - -
Brazilian disc
PGA (virgin) 1.4 ± 0.3 8.5 ± 1 -
Gilsocarbon 2.2 ± 0.4 15.6 ± 1.3 -
Micro-scale cantilever beam
Gilsocarbon > 20 GPa > 9.8 GPa > 10 GPa
Nano-indentation
Gilsocarbon 7.1 - 9.3 - -
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Symposium on Graphite Testing for Nuclear Applications
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Concluding comments
• Small-scale testing is a powerful approach to explore mechanical properties of quasi-brittle materials
• Properties measured depend upon length scale of tests
• Centimetre scale tests provide representative global measurements
• Millimetre scale tests could provide representative global values if sufficient tests conducted to sample the material – requires statistical analysis of these data as porosity increases this becomes more difficult
• Micro-scale and below provide measurements for specific micro-scale features
• Important to understand what information is required for a particular application
19th-20th September, 2013
Symposium on Graphite Testing for Nuclear Applications
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Acknowledgement
We acknowledge the financial support from EPSRC funded project – QUBE
(QUasi-Brittle fracture: a 3D Experimentally-validated approach). Grant number:
EP/J019801/1. The Materials Research Laboratory at the Culham Centre for
Fusion Energy was used for the nano-indentation on Gilsocarbon graphite.
19th-20th September, 2013
Symposium on Graphite Testing for Nuclear Applications
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19th-20th September, 2013
Symposium on Graphite Testing for Nuclear Applications