Strength Of Materials Concept Inventory Assessment Instrument
 

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Goal

The goal is to develop a simple inventory to measure mastery of fundamental strength of materials (SOM) concepts such as stress, strain and buckling. Students are first introduced to these concepts in a sophomore-level Strength of Materials course (also called Mechanics of Materials). Follow-on courses such as Structural Analysis in civil engineering or Machine Design in mechanical engineering build directly upon these concepts. Many students will not master some of the more abstract SOM concepts until completion of these follow-on courses.

The SOM Concept Inventory has been motivated by the Force Concept Inventory created by Halloun and Hestenes [1-4] and its impact on physics education. The Force Concept Inventory (FCI) was designed to measure conceptual, not computational, understanding of Newtonian Mechanics. The questions are posed to focus on intuitive comprehension independent of knowledge of the terminology or numerical modeling. Following the lead of the FCI, faculty members are creating concept inventories for other disciplines. More information about concept inventories can be found in a paper by Evans and Hestenes.[5]

Although a copy of the strength of materials inventory is not available, information about its development can be obtained by contacting either Jim Richardson, Civil Engineering Department, University of Alabama, or Jim Morgan, Civil Engineering Department, Texas A&M University.

Typical Student Background

The typical student entering a first strength of materials course will already have taken:

  • One or two semesters of calculus·
  • One semester of physics
  • One semester of statics
Physics and statics both introduce concepts that are used in a strength of materials course. In physics, a typical student has been briefly introduced to:

  • Forces
  • Vectors
  • Free body diagrams and conditions of equilibrium
  • Moments
  • Center of mass
  • Work
  • Pressure
  • Torque
In statics, a typical student has worked simple problems involving:
  • Equilibrium, free body diagrams and reactions
  • Internal forces and moments in trusses, beams and frames
  • Shear and bending moment diagrams
  • First moment of area and centers of mass
  • Second moments of area and mass moments of inertia

Strength of Materials Concepts

To develop the SOM concept inventory, concepts were classified into the following categories:

  • Stress, strain and deflections due to axial forces in rods
  • Stress, strain and deflections due to torsional forces in rods
  • Shear and bending moment distributions in beams
  • Stress, strain and deflections due to shear and bending in beams
  • Axial buckling of columns
  • Stress in pressure vessels
  • Stress transformation and failure of ductile and brittle materials

SOM Concept Inventory Development Process

The authors met with the developer of the Force Concept Inventory, Dr. David Hestenes at Arizona State University. He explained the history of the FCI and gave us some tips for developing our own concept inventory. Then, we developed the initial concept inventory during the Spring semester of the 2000-01 academic year. We shared the initial version with professors that teach SOM and professors that teach courses relying on SOM. We incorporated their suggestions to produce Version 2. Next, we gave Version 2 to students taking SOM during the summer of 2001. We interviewed the students after taking the concept inventory to identify poorly posed questions. The revised inventory became Version 3. We have given Version 3 to 60 SOM students and 60 students in follow-on courses at the beginning of the Fall semester of the 2001-02 academic year. We have performed psychometric analysis on the results from the 60 students taking the follow-on course to SOM. We plan to modify the concept inventory during Fall semester and have a beta version available for distribution by the beginning of 2002.

References for Further Information

  1. Hestenes, David, Malcolm Wells, and Gregg Swackhamer (1992). Force Concept Inventory. The Physics Teacher, 30 (3), 141-151
  2. Hestenes, David, and Ibrahim Halloun (1995). Interpreting the Force Concept Inventory. The Physics Teacher, 33 (8)
  3. Halloun, Ibrahim and David Hestenes (1985). The initial knowledge state of college physics students. American Journal of Physics, 53(11), 1043-1055.
  4. Halloun, Ibrahim and David Hestenes (1985). Common sense concepts about motion. American Journal of Physics, 53(11), 1056-1065
  5. D. L. Evans and David Hestenes, "The Concept of the Concept Inventory Assessment Instrument, Proceedings, 2001 Frontiers in Education Conference, Reno, Nevada, 10-13 October 2001
  6. Richardson, Jim, and Jim Morgan, "Development of an Engineering Strength of Material Concept Inventory Assessment Instrument," Proceedings, 2001 Frontiers in Education Conference, Reno, Nevada, 10-13 October 2001

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