DESIGN MANUFACTURE SIMULATION AND EXPERIMENTATION OF SEVERAL TOOLS TO ASSIST IN TEACHING STRENGTH OF MATERIALS AND STATICS COURSES

摘要

In the bachelor degree program of mechanical engineering, strength of materials and statics are among the most fundamental and applied courses. The use of experiments and simulations in order to improve the quality of learning these subjects cannot be overstated. In strength of materials the analysis of pure bending and transverse loading are two important objectives. The similarities and the differences of the behavior of a structure to these types of loadings should be understood thoroughly. These behaviors are similar in terms of generating bending stresses; but they are different when it comes to producing shear stresses. During teaching strength of materials for many years, the second author has experienced that many students have problem in differentiating these phenomena. The problem is that students obviously cannot see the different values of internal forces and stresses in these cases. These concepts have been usually taught in lectures using diagrams, formulas and textbooks. This method can be improved by giving students the opportunity to gain hands-on experience and to use CAD software for simulations. Such an experience also provides a means for comparing theoretical, simulation and experimental results. In this research, to address the mentioned need, two devices are designed, fabricated and tested. The main question to be answered by using these devices is, "How the transverse loading of a beam compares with the pure bending of the same beam?" To answer this question, in this research two devices are designed and constructed. Each device consists of a beam with two polymethyl methacrylate (PMMA, or simply, Plexiglas) layers. Loads are applied on these beams in order to produce either transverse loading or pure bending moment. For analyzing pure bending, a four-point bending set up is fabricated. For shear force generation in transverse loading, tip load is applied on the cantilever beam. Pasta is used as a test specimen to identify in which of these two cases shear force generates. These experiments are augmented with computer simulation and theoretical results and used in classrooms at the University of Southern Maine (USM). The objective is to facilitate the understanding of a concept that is usually difficult for students to comprehend using traditional teaching methods. Also, for using in a statics course, a separate test setup for analyzing the equilibrium of a hinged bar subjected to a tip force is designed and built. The tip force is applied and measured using a spring scale. There are three parameters that can be varied in this device. These are the bar mass and angle as well as the angle of the applied loading. Students will use this device in the statics course to explore the concept of the moment of a force as well as to compare theoretical and experimental predictions of the load needed for maintaining the equilibrium of the bar.