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Uniaxial Tension Testing Lab: Fewer Instructions for Better Results?

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Conference

2018 ASEE Annual Conference & Exposition

Location

Salt Lake City, Utah

Publication Date

June 23, 2018

Start Date

June 23, 2018

End Date

July 27, 2018

Conference Session

Mechanical Engineering Division Technical Session 9

Tagged Division

Mechanical Engineering

Page Count

18

Permanent URL

https://peer.asee.org/31183

Download Count

50

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Paper Authors

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Hadas Ritz Cornell University Orcid 16x16 orcid.org/0000-0002-5396-2962

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Hadas Ritz is a senior lecturer in the Sibley School of Mechanical and Aerospace Engineering at Cornell University. She teaches required and elective courses covering a wide range of topics in the undergraduate Mechanical Engineering curriculum. Her main teaching interests include solid mechanics and finite element analysis. Ritz was recognized with a 2013 Cornell College of Engineering Excellence in Teaching Award. She received her PhD in Mechanical Engineering from Cornell in 2008.

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Meredith N. Silberstein Cornell University

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Nelly Andarawis-Puri Cornell University

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Abstract

In this sophomore level statics and mechanics of materials course, students perform several small-scale benchtop labs during discussion sections throughout the semester. These experiments are intended to expose students to more hands-on interaction with the course concepts such as: force and moment balance, statically indeterminate axial stress, and beams in bending, among others.

One of the labs is a uniaxial tension testing lab where students work in pairs with a thin rubber specimen. They hang pre-measured weights from the specimen, measure the change in position of reference marks on the specimen, and from those force and displacement data calculate stress and strain. They then plot the data points on a provided graph and estimate Young’s modulus from the slope of their data.

During Fall 2017 we compared two versions of this lab. Version A was the open-ended version. Students were provided equipment and a blank stress-strain graph, and told to spend several minutes working with their partners to plan what data to collect to eventually estimate Young’s modulus for the material. No specific instructions were included in that version. Version B was much more explicit. Well-labeled tables and specific step-by-step instructions were provided for both data collection and data reduction. Students were led through the steps from force and position measurements to stress and strain, and finally to Young’s modulus. Both versions concluded with essentially identical discussion questions.

Assessment of any differences between these versions is based on student surveys and one midterm exam problem. Students were asked to complete anonymous feedback surveys following the lab that asked about their enjoyment of the activity, the level of intellectual challenge, and the perceived value of the lab. One problem on the first midterm exam was specifically related to this lab and performance on that problem was tracked based on discussion section and therefore which version of the lab students completed.

Full statistical analysis is not yet complete, but preliminary data indicate almost no difference in student perceptions between the two versions of the lab. Students ranked their enjoyment, the level of intellectual challenge, and the perceived value very similarly between the two versions. However, performance on the exam problem was better for students completing the open-ended version of the lab. This may indicate that when students design their own experiment they gain a better understanding of proper data reduction methods.

Ritz, H., & Silberstein, M. N., & Andarawis-Puri, N. (2018, June), Uniaxial Tension Testing Lab: Fewer Instructions for Better Results? Paper presented at 2018 ASEE Annual Conference & Exposition , Salt Lake City, Utah. https://peer.asee.org/31183

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