Strain Hardening with a Paper Clip

Submitted by: Dr. Ipek Yucelen

Title: Strain Hardening with a Paper Clip

Concept: Strain Hardening (Work Hardening)

Institution: University of South Florida

Course: Materials Engineering I

Level: Undergraduate | Also suitable for high school students

Semester: Summer 2024

Type: In-Class Demonstration / Hands-On Activity

Materials Needed: One metal paper clip per student

Description:

To help students feel and understand strain hardening, I hand out a metal paper clip to each student. They begin by uncoiling it, then repeatedly bend it back and forth at the same spot.

At first, the metal bends easily. But as they continue, it becomes harder to deform—that’s strain hardening in action! Eventually, the paper clip breaks, giving students a real sense of how dislocation motion is affected by plastic deformation.

Teaching Tips:

• Ask students to describe how the feel of the metal changes as they bend it.

• Connect their observations to the buildup of dislocations and increased strength.