Begin by asking students how they would break the stick? Most, if not all, students will break the popsicle stick in weak-axis, three-point bending. Note that students have an understanding of stresses without even realizing it! Let’s do the math! Why is this the best configuration for failure? Assume the normal stress limit of the […]
Determine failure surface using Mohr’s Circle by giving students two pieced of chalk to break: one in bending and one in torsion. General note you may need to share with you students: brittle materials (like chalk) tend to fail under high tensile stresses. We need to find peak tensile stresses in a material. Let’s find […]
This is a simple assignment that your students can do at home, either as part of a remote course or an in-person course. Students make short (<5 minute) videos demonstrating an ASTM standard mechanical test (or other common mechanical test) using basic household materials. Learning Objectives Read and interpret ASTM standard specifications for mechanical tests. […]
The Spring 2020 semester at Cornell University was thrown into chaos by COVID-19. But we had a little more time to prepare for Summer 2020. In this video, I describe how we adapted our mechanics of materials lab activities for remote instruction.
Model Description These physical models demonstrate basic principles underlying the behavior of thin-walled pressure vessels (TWPVs). Two models of TWPVs are used to explain forces inside of TWPVs. This demonstration should take 10-15 minutes. Engineering Principle The basic derivation for TWPV behavior (when ) states that for a cylindrical pressure vessel: where the hoop stress […]
Model Description This is a simple demonstration of the basic principals underlying the behavior of thin-walled pressure vessels (TWPVs). A hot dog is used to show that hoop stresses are twice as high as longitudinal stresses in cylindrical pressure vessels and failure occurs along the length of the hot dog. The failure that occurs in […]
Model Description This physical model demonstrates thermal expansion for different metals. This demonstration should take 10-15 minutes. Engineering Principle When materials, especially metals, are exposed to heat, they expand at different rates. The reverse is also true in that cold temperatures tend to cause material contraction. The amount of expansion/contraction may be small, but if […]
Model Description Students often have difficulty with shear and stress/strain transformation. To give a quick demonstration of pure shear and stress transformation, blocks are drawn on the side of a BIG book to show the effects of shear and transformation of axes. This demonstration should take 3-5 minutes. Engineering Principle Shear occurs when parallel planes […]
Model Description These demonstrations show the effects of shear within rectangular members. This demonstration should take 10-15 minutes. Engineering Principle When a load perpendicular to the longitudinal axis is applied to a beam, the force is transferred through the beam through shear. With the help of these two demonstrations, the students will better understand how […]
Model Description These physical models easily and quickly demonstrate the behavior of varying cross-sectional shapes to varying loading conditions. When the instructor passes the rubber shapes around during class, students personally experience the associated behavior and quickly catalog for themselves when shapes are best used. Applying vertical, horizontal, and circumferential lines along the length allow […]