Teaching Basic Materials Engineering Design to Engineering Technology Students Using Stringed Instrument Top Design

摘要

During the past five years, we have transformed our basic Introduction to Materials Engineering course from a passive lecture only course to a learner-centered and concept based course. It is known that teaching any course in multiple ways, especially in ways which build scaffolds from the students' previous knowledge base, can prove to be very effective for a wide range of learners. One of the activities used in the course in this category which has proven useful and effective involves the use of stringed instrument design. This paper describes the selection of alternative materials for the design of soprano ukulele tops to teach materials engineering fundamentals such as the elastic constant, specific stiffness, density, bending stress and deflection. An inexpensive ukulele kit ($25) is used to construct the instruments with the alternative materials to illustrate the results of implementing the key design parameters on the sound of the instrument. The paper delineates the design parameters and equations needed for the ukulele tops so that other faculty members can easily use these concepts as an active learning tool. The paper also describes in detail how to construct the instruments with the new tops and how the tonal effects can be measured. Although mahogany and koa woods are the traditional choices for ukulele tops, a wide range of materials can be used such as natural materials like spruce and balsa wood to synthetic materials such as acrylic and carbon fiber reinforced plastics. It is very easy to demonstrate why some materials make superior instruments, while other materials produce mediocre instruments. One need not make careful measurements on some of the instruments produced as the tonal effects are dramatic and easy to hear. The geometry of the soprano ukulele is straightforward and its size is small, so this instrument is a good choice for in-class demonstrations, but the principles could be used to design acoustic or classical guitar tops or mandolin tops. The paper concludes with our initial assessment data, including lessons learned from pre- and post-class questionnaires, and actions that are planned for the future for this class for its continuing improvement.