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Student Understanding of the Mechanical Properties of Metals in an Introductory Materials Science Engineering Course Abstract

We report on initial findings of a project to identify, study, and address student difficulties in a university-level introductory materials science course for engineers. Through interviews of over 80 students and testing of over 300 students, we examined in detail student understanding of the mechanical properties of metals. Here we describe a number of student difficulties in understand- ing macroscopic properties of metals and the effects of simple processing on these properties. For example, many students have difficulty with basic definitions of mechanical properties. These difficulties include the notion that yield strength is independent of the cross sectional area of the material, the difference between the strength of a material and the stiffness of that material, and the actual definition of yield strength and Young’s modulus. Further, only half of the students recognized that drawing a metal through a tapered hole increases its strength and only half again of these students could give a simple, correct explanation as to why. All of these results are after traditional instruction that explicitly covered these topics. In order to address these difficulties, we are in the process of designing and field testing 45 minute in-class active learning group-work lessons, similar in structure and style to lessons shown to be effective in physics education research efforts.

Introduction

An understanding of the definitions of basic mechanical properties is fundamental to understanding materials science. A number of researchers have investigated student understanding of some me- chanical properties such as students’ beliefs about strong materials3 and students’ understanding of strengthening mechanisms behind coldworking4 . In this paper, we add to the existing research on student difficulties with mechanical properites. We study in detail a few concepts including student confusion between mechanical stress and force, and student confusion between stiffness and strength.

All of the data presented here was collected after students received direct instruction and home- work on these topics. The lecturer for the class was an experienced teacher who was aware that students have difficulties with these topics and took steps in class to address these difficulties with slides aimed specifically at the definitions for stress, elasticity, yield strength, and stress strain plots as well as clicker questions and live demos.

Participants and Methods

The participants in this study were enrolled in the introductory materials science engineering course at The Ohio State University, a required core course for many of the engineering major programs. The students ranged from 2nd to 5th year students and about 10% of the students in-

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Rosenblatt, R., & Heckler, A. (2010, June), Student Understanding Of The Mechanical Properties Of Metals In An Introductory Materials Science Engineering Course Paper presented at 2010 Annual Conference & Exposition, Louisville, Kentucky. 10.18260/1-2--16432