Photoelastic Models
Purpose
Demonstrates stress-induced birefringence (photoelasticity). Transparent plastic shapes placed between crossed polarizers reveal colorful stress patterns when loaded, showing how engineers visualize internal strain distributions using polarized light.
Figure 1:
Overhead projector setup with crossed polarizers on the stage. The four photoelastic shapes — straight rod, right angle, right angle with cutaway inner bend, and hook — are shown alongside.
Figure 2:
Right-angle piece under load between crossed polarizers. Isochromatic fringes concentrate at the inner corner, showing stress concentration at geometric discontinuities.
Figure 3:
Hook under load showing stress distribution through the curved geometry. Higher-order fringes at the bends indicate stress concentration at points of maximum curvature.
Figure 4:
Straight rod under bending stress. Parallel isochromatic fringes run along the length, with fringe density increasing toward the edges where stress is highest.
Equipment
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