June 18, 2006
June 18, 2006
June 21, 2006
11.482.1 - 11.482.14
Difficulties with Shear Stress in Introductory Mechanics of Materials Abstract
Shear stress is a difficult concept for students when it is first encountered in mechanics of materials. Whether this difficulty is due to a single fundamental difficult topic, a variety of difficult topics, or some other factor has not been addressed in the literature. A student survey and student interviews were conducted in an introductory mechanics of materials course mid- semester to get more specific answers from the students as to difficulties and aids in understanding the concept of shear stress. Responses to which shear stress concept they ‘understood best’ or ‘had the most difficulty with’ were quite varied with many concepts appearing on both lists. Respondents’ replies to how they would explain shear stress to another person offer insight into how students understand shear stress as a whole. This data indicates that here does not seem to be a single underlying cause to the difficulties that students have with shear stress. The distribution of the difficulties implies that peer teaching may be an effective method to reduce the difficulty of these concepts.
The topic of focus for this paper is the concept of shear stress, as taught during an introductory Mechanics of Materials course. Shear stress is stress that occurs tangentially to a plane of interest. Many engineering materials fail in shear, so understanding this concept is critically important to good engineering design. Shear stress, based on teaching experience, appears to be a difficult concept for students. Whether this difficulty is due to a single fundamental difficult topic, a variety of difficult topics, or some other factor has not been addressed in the literature. Because the teaching methods used in this course are similar to how mechanics of materials is taught nationally, the survey results of the study discussed below should be broadly applicable.
There are a variety of methods that can be used to determine what concepts are difficult for students. For many disciplines, concept inventories have been used to determine what concepts are most difficult for students. A concept inventory for mechanics of materials (strength of materials) has been developed [1-3]. From this concept inventory, the initial data (available at: http://somci.eng.ua.edu as noted in reference ) shows that there are broad categories of misconceptions relating to a “failure to make fundamental differentiations.” It is noted that students often fail to differentiate between normal and shear stress and stresses acting in different directions, however no details are given as to underlying misconceptions and how course materials impact learning. Assessment of how specific course materials impact understanding has been somewhat rare in the literature. However reference  and  show that interactive courseware can have a marked improvement in the ability of students to generate correct shear- moment diagrams for beams or determine centroids. A survey for faculty on what concepts students have difficulty with is included in reference . Their results were used to inform instructional module development, however details of the results were not provided. Student focus groups have been used to “offer a window on student knowledge” and gauge student’s perspectives on difficult concepts  in materials science, but no such data is available for mechanics of materials.
Creuziger, A., & Crone, W. (2006, June), Difficulties With Shear Stress In Introductory Mechanics Of Materials Paper presented at 2006 Annual Conference & Exposition, Chicago, Illinois. 10.18260/1-2--1462
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