The mechanism of torsional chatter in drilling differs qualitatively and quantitatively from other types of chatter. In this paper we show that torsional chatter can be explained by the torsional-axial coupling inherent in a twisted beam; the beam “untwists” and extends in response to an increase in cutting torque. Based on a model of this mechanism, predictions of stability boundaries and chatter frequencies are derived by frequency domain analysis, and confirmed by numerical simulation and experimental tests. The effect of the torsional-axial coupling is opposite that of traditional cutting in that an increase in cutting forces leads to axial extension and greater chip load. Because of this sign difference, the limiting depth of cut is governed by the positive real part of the frequency response function, which explains the unexpected fact that torsional chatter occurs below the natural frequency of the tool.
In 2012, the University System of Ohio member universities, which are overseen by the Ohio Board of Regents, moved from operating on a quarter-based calendar to a semester-based calendar. In conjunction with this change, the Mechanical Engineering curriculum at The Ohio State University was revised, and a new and unique course was added to the required curriculum for students in the major. The course, titled "Introduction to Mechanical Engineering", encompasses elements of both the spiral curriculum and experiential learning strategies 19,20 . A prior ASEE paper 1 outlined the structure of the course at the time of pilot development, and the student feedback provided by the pilot program participants. Now in its third year of full-scale implementation, the course has undergone some modification from its original design. Additionally, exploration has begun within the department in order to incorporate additional elements of the mechanical engineering curriculum into the course in a more comprehensive spiral approach.The key challenges for this course are that it is a required course for all students in the major in a very large department, and that it is a hands-on course in which all students are required to complete every aspect of the machining, assembly, and programming of a compressed air motor individually. The course was designed specifically with this requirement to ensure that every student interact directly with every aspect of the process, in order to prevent the specialization, uneven participation and resulting uneven skill and knowledge gains that can occur in group project settings. One interesting outcome of the course has been the relatively large number of female students who completed the course and then applied and were selected as undergraduate teaching assistants for the course. In a department and discipline where female students remain under-represented overall, they have been participating at high levels in this role. We report here on the evolution of the course from its original pilot program through the first four semesters of full-scale implementation, as well as future plans for the course. Our assessment includes detailed feedback from students and teaching assistants who completed the course in the initial two years.
The mechanism of torsional chatter in drilling differs qualitatively and quantitatively from other types of chatter. In this paper we show that torsional chatter can be explained by the torsional-axial coupling inherent in a twisted beam; the beam “untwists” and extends in response to an increase in cutting torque. Based on a model of this mechanism, predictions of stability boundaries and chatter frequencies are derived by frequency domain analysis, and confirmed by numerical simulation and experimental tests. The effect of the torsional-axial coupling is opposite that of traditional cutting in that an increase in cutting forces leads to axial extension and greater chip load. Because of this sign difference, the limiting depth of cut is governed by the positive real part of the frequency response function, which explains the unexpected fact that torsional chatter occurs below the natural frequency of the tool.
Date Presented Accepted for AOTA INSPIRE 2021 but unable to be presented due to online event limitations. The Mobility Assistance for People with Cognitive Disabilities (MAPCD) program, including the WayFinder 3 assistive smartphone navigation app and training program, addresses barriers to community mobility and provides supports to both individuals with cognitive deficits and their caregivers. We describe the MAPCD program and examine strategies that facilitated the adoption of the WayFinder 3 app designed to optimize independent community mobility. Primary Author and Speaker: Sarah E. Anderson Additional Authors and Speakers: Lisa Juckett Contributing Authors: Carmen DiGiovine, Sandra A. Metzler, Ashley Stojkov, Bethany Frick, Kaetlyn E. Culter, and Elizabeth Mance
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