Strain Field Mining:
The Key to Understanding the Strength and
Toughness of Paper and Packaging
Yoon Joo Na, James Collins, and Christopher L.
Muhlstein
School of Materials Science and Engineering
The Muhlstein Research Group
Deformation, Degradation, and Failure of Materials
• Metallic,
ceramic,
organic, and
composite
materials
• Emphasis on
crack growth
and
degradation
mechanisms
• From
nanoscale to
bulk specimens
Understanding Strength and Toughness
• Constitutive behavior
– Nonlinear elastic plastic
– Deformation mechanisms
– Material vs. fiber structure
• Failure mechanisms
– Fiber fracture and pullout
– Critical defects (what and
where)
– Environmental effects
• Fracture mechanics
– Fracture toughness
– Subcritical crack growth
DIC is the solution…
• Spatial distribution of
strains in paper
• Direct correlation
with structure
How Digital Image Correlation and
Point Tracking Works
1. Identify and track
features
2. Interpolate
displacements
3. Calculate strains
(displacement gradient)
Types of Features and Analyses
Traditional
Points
Features
• Identify with image processing algorithms
• Determine sizes, shapes and positions
• Select best features for tracking
Tracking Feature Motion
•
•
•
•
Base and input images
Rigid body motion and deformations
Cross correlation algorithms
Sub pixel resolution
Displacement Interpolation Scheme
1. Voronoi cells
2. Regularly spaced
array
Calculated Strains
What is strain field mining?
• Extract information
from the magnitudes
and spatial
distributions of strains
• Image processing,
spatial statistics, and
other analysis
methods
Engineering Superior Adhesive Joints with
Strain Field Mining
Collins and Muhlstein 2015
Engineering Superior Adhesive Joints with
Strain Field Mining
• Predict joint strength and failure mode from strain field
• Process development and control tool
Collins and Muhlstein 2015
Deformation and Failure of Copy Paper
•
•
75 g/m2 copy paper (OfficeMax, 8.5
in×11in)
Modified TAPPI (T404, T402)
specimens (50 mm×12.5 mm)
•
Preconditioned for 24 hours (25°C,
35% R.H.) and conditioned/tested for
>3 hours (23°C, 50% R.H.)
Tensile Fracture Path (MD)
Tensile Fracture Path (CD)
Axial Strain Field Mining (MD)
Axial Strain Field Mining (CD)