June 23, 2013
June 23, 2013
June 26, 2013
23.843.1 - 23.843.9
Laboratory Activities to Illustrate the Importance of Low Cycle Fatigue and Linear Elastic Fracture MechanicsAbstractThe goal of this project was to develop hands-on activities that would illustrate the limitations ofthe static failure theories and High Cycle Fatigue (HCF) modeling techniques covered in detail ina third-year Design of Machine Elements class. This does not necessarily require that significantmaterial is added to the class, only that we make the students aware that what we teach them isnot universally applicable, and that they need to understand the problem at hand before applyinga model.Low cycle fatigue theory and linear elastic fracture mechanics are important topics formechanical engineering students to learn and understand. Essential in broadening the scope anddepth of students’ knowledge of mechanics, these topics create a better versed engineer withexperience in topics necessary in many industries. Current required coursework in MechanicalEngineering at [our school] is insufficient in that it only covers HCF theory and bypassesfracture mechanics altogether. An important gap in student understanding of these failuretheories is that they tend to use the techniques taught in class in any similar situation. HCF istaught as it relates to machine design, and is therefore focused on application to steels, yetstudents may try to use this tool in analyses where plastic strain is a significant contributor tofailure, or where the components being analyzed are made from aluminum or other material thatdoes not have a well-defined endurance limit. Similarly, the only static failure theories ourstudents see are based on undamaged materials, not materials that may have pre-existing cracks.Students will leave the class and be tempted to try to apply these theories to cracked bodies thatcould fail at lower applied stresses.Fatigue and fracture specimens and tests were designed by an undergraduate MechanicalEngineering student, as part of an Independent Study project. This student createddemonstrations that could be easily incorporated into an existing course to show the contrast withthe fatigue life prediction methods currently being taught, as well as introduce students tofracture mechanics. The results of the fatigue tests were favorable, with good correlationbetween theoretical and experimental results while the fracture tests also proved successful inthat results were consistent and repeatable. These successful results were instrumental increating a lesson plan to be presented to students in the form of hands-on experience inconjunction with classroom instruction in the theory. This paper presents an outline of thecurrent topics taught, the design, implementation, and results of the new instructional laboratorytests. Assessment of the implementation of these new laboratory tests will be presented.
Boedo, S., & DeBartolo, E. A., & Kasemer, M. (2013, June), Laboratory Activities to Illustrate the Importance of Low Cycle Fatigue Paper presented at 2013 ASEE Annual Conference & Exposition, Atlanta, Georgia. 10.18260/1-2--19857
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