The proposed approach for determining combined stresses of a component

For a mechanical engineering program, one of the main learning outcomes is that students can design mechanical system components. Achieving this outcome requires students be trained to calculate the combined stresses of a component with multiple loadings by using typical theoretical formulas. We have found, however, that students had difficulty in effectively calculating these combined stresses. We believe that this was mainly due to some misconceptions regarding combined stress. During the last several years, we proposed and gradually modified an approach which facilitated students to calculate stress under combined loading. The proposed approach contains 7 steps which clearly demonstrate the relationships between the forces and the induced stresses. The process guides students in the calculation of stress components due to each individual internal resultant force and how to correctly combine these stresses to form the state of stress at the point under the consideration. This paper will describe the proposed procedure with results of the implementation of the procedure in our teaching. The effectiveness of the proposed approach was evaluated using different classes performance on the combined stress problem in the midterm exam. In two class sections, we explained and implemented the proposed approach with three examples. In another two class sections, we just used the traditional approach; that is, we followed the topics arranged in the textbook for calculating the combined stress. The comparison of the grades on the combined stress problem indicated that the exam average score in the sections with the implementation of the proposed procedure was statistically significantly higher than the exam average score in the sections without the implementation of the procedure. A survey was conducted in the classes regarding the proposed procedure. The feedback information from the survey was very positive. This paper will also present these results of the data analysis of the student survey.