do not edit bmg in indentation ismanam2013
TRANSCRIPT
Mechanical behaviour of Zr‐based metallic glass in indentation
Presented By: Vaibhav Phadnis
Vahid NekouieGayan Abeygunawardane‐Arachchige
Anish RoyVadim Silberschmidt
Wolfson School of Mechanical & Manufacturing Engineering, Loughborough UniversityUta Kühn
IFW/Dresden
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Introduction & Motivation
Metallic glass shows unique mechanical properties Evidence of length scale effects Deformation mechanisms of metallic glass are unique
plastic shear flow in the microscale, but brittle fracture in macroscale deformation induced ductilization
Ultimate goal is to predict component deformation under macroscopically homogeneous loads
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BMG Material
BMG alloy manufactured at IFW/DresdenZr48Cu36Al8Ag8 Samples: 70 mm × 10 mm × 2 mm ; 40 mm × 30 mm × 1.5 mm
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Outline: Mechanical characterisation of the BMG alloy Macroscale Microscale Nanoscale
Constitutive material modelling and Finite Element Analysis
Macroscale
Bending Tests Elastic Modulus Poisson’s ratio
DMA
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E [GPa] ν Tg [°C]
In‐house experiments 80 – 86 0.34 – 0.35 425 ± 3
Date from IFW 98 – 102 430 ± 3
Literature 115 417
5ISMANAM 2013
Crystalline phase
XRD results show :
(i) The structure of the metallic glass is not completely amorphous.
(ii) There are crystalline phases in the materials and these phases are not
uniformly dispersed in the materials.
Macroscale
XRDCrystalline phase
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Nano/Micro Test (Micro Materials Ltd.)
Tests performed:
Nano and Micro‐indentation
Load rate: (0.1, 1, 2,10 mN/s)
Cyclic loading
Spherical Indenter
Micro: r = 50 μm
Nano: r = 5 μm
Nano‐Micro indentation studies
Sample is cut Polished Zygo Talisurf
Ra = 2 to 3 nm
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NanoindentationLoading Rate = 0.1 mN/sec
Cyclic loading was performed to determine initiation of plastic deformation (pop‐in)
Load = 2 mN
Fully Elastic deformation
Load = 3 mN
Initiation of plasticity
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NanoindentationLoading Rate = 0.1 mN/sec
Cyclic loading was performed to determine initiation of plastic deformation (pop‐in)
Pop‐in
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MicroindentationLoad/partial unload technique3 cycles of loading‐unloadingMax load = 15 NLoading rates = 1 mN/s, 2 mN/s and 10 mN/s,
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Indentation Depth (µm) Reduced Modulus (GPa) Young modulus (GPa) Hardness (GPa)1.1 87 82 4.811.5 90 86 5.221.8 88 84 5.072.3 95 90 5.56
Microindentation results
Properties
Cycle Indentation depth(m)
Reduced Modulus(GPa)
Young modulus(GPa)
1 6.2 54 47
2 12.5 50 43.5
3 19.4 46 40.02
Load rate 1 mN/s Load rate 2 mN/s
Cycle Indentation depth(m)
Reduced Modulus(GPa)
Young modulus(GPa)
1 6.2 48 41.7
2 12.1 40 34.8
3 18.2 38 33.06
Nanoindentation results
Load rate 10 mN/s
Cycle Indentation depth(m)
Reduced Modulus(GPa)
Young modulus(GPa)
1 5.7 48.03 41.8
2 10.6 39.8 34.6
3 15.3 36.2 31.5
MODELLING OF INDENTATION/Finite Element Modelling
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Microscale modelling Mohr‐Coulomb: hydrostatic stress component is considered.
the normal stress component on the shear plane is important!
MSC Marc 2012 is used to modelLinear MC criterion is used:
/Here: and
To calculate, and /: /
and sin
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Spherical Indenter Radius: 50 μm
FE Model Dimension: (90 × 90 × 100) µm
Displacement Given to Indenter: 4 µm to 10 µm
Initial # of Elements: 4000Element type: Eight noded hex elements (Type 7)
Spherical Indenter: Analytical Rigid Body
Local Adaptive remeshing: Nodes Within a Box, Cylinder or Sphere Criterion
FE modelQuarter Model, use of symmetry planes
BC: bottom rigid
High Performance Computing – Hydra Cluster
• 161 Computer nodes.
• 1956 core 64 bit Intel Xeon cluster.
• Each having two 6‐core Intel Westmere Xeon X5650 CPUs + 24GB of memory.
• Time taken to finish the Analysis: 2 Hours
• Number of cores – 12.
Outlook: Why is there such a significant reduction in Modulus?
Shear bands ‘break up’ the amorphous material into islands of amorphous MG The shear bands help ‘slip’ these islands under macroscopic loads This will reduce the reaction force on the indenter ►reduced stiffness from experiments Material Damage needs to be characterised [in macroscopic modelling]
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Outlook
MC model is not appropriate for the BMG under study The process of deformation induces damage in the material. This damage needs to be characterised in the constitutive behaviour of the material. A gradient plasticity based approach is currently being developed to capture the effect of the local shear bands
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