Anish Roy
Mechanics of Materials and Processes
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Research
Research
Defect Mechanics: Theory & Computation
Defect Mechanics: Theory & Computation
Defects are everywhere (from biological systems to solid materials). Understanding how defects generate, evolve and interact is crucial in determining how physical systems responds to external stimuli. Developing physically relevant and numerically accurate models is the goal.
develop inertial continuum theories of defects in ordered media
develop numerical strategies for solving partial differential equations (including Div-Curl systems)
implement in massively parallel systems
Field Dislocation Mechanics
Field Dislocation Mechanics
A continuum formulation that accounts for the stress field of signed dislocation density accurately as well as the plastic strain from dislocation nucleation and evolution. Thus accurate small-scale constitutive models can be attempted with less phenomenology.
Read: Finite element approximation of field dislocation mechanics Read: Size effects and idealized dislocation microstructure at small scales: predictions of a phenomenological model of mesoscopic field dislocation mechanics: Part I
Slip Step Formation
Small scale FDM
Inhomogeneity of fields
showing Bauschinger Effect
Size Effect
smaller is harder!
Crystal Plasticity
Crystal Plasticity
Modelling in Mg (and alloys)
Modelling in Mg (and alloys)
Challenge: Poor formability at room temperature hence manufacturing involves: (1) High temperature (2) High strain-rate
Goal: understand the underlying deformation mechanisms to assess structural integrity of parts
Twin phases at 523 K (less twin activation) Twin phases at 293 K (significan twin activation)
Methodology
Methodology
Computational Framework
Computational Framework
Results
Results
Liu, Roy, Silberschmidt; Temperature-dependent crystal-plasticity model for magnesium: A bottom-up approach. Mech Mater 2017. doi:10.1016/j.mechmat.2017.07.008.Zhou, Roy, Silberschmidt; A crystal-plasticity model of extruded AM30 magnesium alloy. Comp Mater Sci 2019. (under review).
Conclusions:
Conclusions:
Crystal-plasticity model which accounts for temperature & strain-rate effects for slip + twinning deformation modes was developed
Twinning plays a significant role in the anisotropic behaviour of the magnesium alloy and should not be ignored
Micro-machining simulations
Read this: Micro-cutting of single-crystal metal: Finite-element analysis of deformation and material removal PDFMicro-machining simulations
HCP Ti single crystal
Plan view
Blast and Ballistics
Blast and Ballistics
We have a Gas Gun which can be pressurised to 100 psi and can shoot a range of projectiles
We also have facilities for ballistics to shoot long projectiles at a range of velocities.
Hybrid Machining
Hybrid Machining
these next generation techniques allow for enhanced and improved machining of parts which are energy efficient and economic.
Ultrasonically assisted turning
Ultrasonically assisted turning
The technique shows significant improvements in force reduction with a visible change in chip formation characteristics
Ultrasonically assisted drilling
Ultrasonically assisted drilling
Significant force reductions in thrust force and torque is recorded. Improvements in chip formation in drilling of polymeric fibre composites that indicate a fundamental change in the process zone under the effect of ultrasonic vibrations
Read this: Effect of ultrasonically-assisted drilling on carbon-fibre-reinforced plastics PDFRelated Modelling work
Read this: Drilling in carbon/epoxy composites: Experimental investigations and finite element implementation, Comp Part A (2013)
Laser + vibration assisted machining
Laser + vibration assisted machining
We are currently developing hybrid-hybrid machining techniques by combining Laser Assisted Machining (LAM) with Ultrasonically Assisted Machining (UAM) thereby yielding a L+UAM process.
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