Advanced learning made as easy as ABC: an example using design for fatigue of machine elements subjected to simple and combined loads

Failure of systems and components resulting from fatigue is one of the most challenging and costly designs accomplished by today's industrial companies. However, one of the more difficult concepts to teach in machine component design courses is fatigue analysis of "real world" components. These components come with multiple cyclic loads, each with different stress concentrations, which result in mean and alternating stress states. The student then must select a failure criterion to obtain an equivalent stress that can be used in one of several different fatigue failure theories to predict either a safety factor or an estimated life. Without a heuristic to guide the student, these types of analyses are very difficult. The authors have developed a heuristic which consists of a combination of a concept map and flow charts that give a student not only process but also directions for improvement of the analysis. The heuristic is a visual image that is simple and can be readily reproduced in a basic sketch. The visual quality (simple and striking) of these concept maps/flow charts produces ready access to the understanding which students ultimately develop. Several examples of the heuristic they have developed are presented along with applications to demonstrate their use.