Stress & Strain

EGR 232

Nov 2013

Engineering Normal Strain and Stress

• Engineering Normal (axial) Strain

• Engineering Avg. Normal Stress

o

Normalavg

A

P

• True Normal (axial) Strain ol

l

l

ltrue

Deformation & Strain (normal & shear)

Engineering Strain and Stress

• Engineering Shear Strain

][tan 1 radiansy

xxy

• Engineering Shear Stress

A

VShearxy

Material Strength Testing, Axial Loads = Normal Stress

Instrumented Specimen, Necks just before failure for Ductile materials.

Stress Strain Diagrams

0.2% Offset Method

Natural Rubber

Cast Iron

Composition Affects SteelStrength

Brittle, tough, & Ductile

Idealized

Double Scales for Accuracy

Work Hardening, Permanent Deformation