What we do
Our research area is the mechanics of fracture. We intend to address some very fundamental problems in this subject. Since the problem in itself is paramount - the method or tool used is according to the problem being considered. Therefore, we use theory, simulation and experiments as the need goes. In short, we intend to specialize in the problem and not the method/tool.
Journal Papers Please click here for my ORCid page (right click and open in new tab).
Here are a few questions we are trying to address:
Role of contact mechanics in fracture mechanics
The video below shows the overall compressive stress vs strain response of an orthotropic solid (wood) with a pore. The pore is open initially and closes gradually with the faces coming into contact. We are trying to understand how does the contact of pore faces influence the failure (fracture) of the solid.
This problem translates to the application of other orthotropic porous solids (like bones) under compression.
Plasticity and fracture at atomistic scale
The video below shows the overall tensile stress vs strain response of an amorphous solid (silica) at an atomistic scale. The void formation and it's growth dictates it's plasticity and fracture behaviour. We are trying to better understand continuum concepts like flow/hardening rules and crack propagation direction using these simulations from the first principles.
This problem translates to the application of plastic failure of silica tiles (used in re-entry of space vehicles) and finding direction of rift growth in icebergs (ice is amorphous at large scales).
Crack growth paths in polycrystalline solids
The microscopic picture below shows the grains and grain boundaries of a polycrystalline silicon solar cell wafer. The picture further below shows the crack growth path because of the presence of various grain boundaries.
We are trying to understand, through linear elasticity, the role of grain boundaries in altering rack growth direction.
Integral equations for fracture mechanics problems
It is well known that formulating the fracture mechanics problem as a partial differential equation offers a huge advantage of being solvable using Finite Element Method. We are convinced that it is (at least) mathematically questionable to use certain cohesive traction-separation relations (like the one shown below) for solving differential equation using variational methods.
We instead use integral equations to bypass above issues.
Research Facilities
Testing system (Fracture and Thermal)
Make Zwick, Model Z050 TE, Nominal Force 50kN
Testing speed 0.0005-600 mm/min
Linearity Accuracy under 0.25% from 200 N and under 1% from 50 N
MakroXtens extensometer (resolution 0.06-0.12 micro-meter) direct measurement up to fracture
Clip-on extensometer, gauge length 10 mm
Temperature chamber: RT to 250 C
Wedge grip, specimens flat 0-17 mm and round 4-12 mm
CT specimen testing, specimen thickness 0.25 inch and 0.5 inch
3 point bend, support separation 10-180 mm
Screw grips
Compression platens, square 400 mm side
Additional 1 kN load cell with it's screw grips (RT and thermal)
2D DIC quasi-static
Camera Make Basler (Sony IMX183 CMOS sensor 17 fps at 20 MP resolution)
Lens Make Basler (focal length 50 mm), Acquisition 1 Hz
Data Acquisition System
Make Quazar Technologies
4 channel DAQ
Full bridge strain gauge signal conditioner
Workstations
Dell Precision Tower 5810, 5810, 3620
Tyrone Camarero SS400TR-54
Laptops with IIT Delhi HPC
Vacuum Oven
Make Labsol, Temperature: 5 C to 250 C, Capacity 190 litres
Moisture Meter
Make Mastech, Model MS6900
Depth 0-50 mm, Range 0-60 percent, Sampling rate 240 ms, Resolution 0.1 percent
Stereo Zoom Microscope
Make Leica Microsystems, Model M125C
Zoom Ratio 12:1 (fully apochromatic), Magnification 8X to 100X
Maximum resolution more than 430 lp/mm with 1X objective and 10X eyepiece
Digital color camera with 12 MP with 4K 60fps
Micro Vicker's Hardness Tester
Make ASI
Load 0.3-30 kgf, Automatic loading/releasing, Dwell 5-99 seconds
Measuring unit 0.1 micro-meter, Microscope 100X and 200X
Rotary Fatigue Machine
Make Dinesh Scientific
Gripping Diameter 12 mm, Testing Diamater: 8 mm (maximum), Speed 2800 rpm
Bending moment 25-200 kgf-cm
Vibration Isolation Table
Make Holmarc, Non-magnetic breadboard 1.2 m by 1.2 m
Passive vibration isolation system with inter-connected legs (pneumatic 25-35 psi)
Currently, a system to study mechanics of crack growth in ball bearings is being setup
VFD Make Schneider
Fused Deposition 3D Printer
Make CREALITY, Model Ender-3 S1 Plus
Print size: 300*300*300 mm, Layer height 0.1-0.4 mm, Precision 100 mm +/- 0.2 mm
Filament diameter 1.75 mm, Supported Filament: PLA/ABS/TPU/PETG
Resin 3D Printer
Make CREALITY, Model LD 002 H
Print size: 130*82*160 mm, Resolution 1620*256, Curing time 1-4 s/layer
Layer height 0.03-0.05 mm, XY-axis precision 0.051 mm
Surface Roughness Tester
Make Mitutoyo, Model Surftest SJ-210
Range -200 to 160 micro-meter, Resolution 0.02 micro-meter, Speed 0.25-0.75 mm/s