Statistical analysis of the influence of tooth geometry in the performance of a harmonic drive
The objective of this research is to determine the influence of gear tooth geometrical variations in the performance of a double wave harmonic drive through statistical analysis. This work incorporates state of the art analytical and numerical models to evaluate kinematic error, load capacity, bending fatigue strength, and pitting. The geometric variables considered in this study include gear modulus, pressure angle, and tooth correction factor. The statistical analysis follows a three-level full-factorial design of experiments. Nonlinear dynamic simulation is accompanied by finite element analysis to estimate contact and bending stresses. Largest bending fatigue strength is also determined. Results demonstrate that gear modulus is the geometric parameter with prevalent influence on the kinematic error, and pitting life is rather high for all geometric variables considered.
Minimization of bead geometry by optimization of regression equations for laser-beam bead-on-plate welded Hastelloy C-276 sheet
The present study is aimed at selection of laser beam welding parameters that would produce through-penetrated weld zone with minimum cross-sectional area in 2.7-mm-thick Hastelloy C-276 sheet. Weld zone area was found to be comprised of geometrical features such as total throat, crown width, root width, neck width. A new, fast and relatively simple method of optimization has been proposed in the present study. Regression equation for each geometrical feature was generated from the full factorial experimental design data. Optimization of welding parameters to minimize weld zone area was carried out by solving regression equations using experimentally obtained values of geometrical features as the boundary condition. Once the optimized value of parametric combination was obtained, experiment was conducted to confirm the minimization of weld bead cross-sectional geometry.
Trade Secrets: Poetry in the Teaching Machine
Abstract:This essay explores the ways in which experimental writers who work as professors must reconcile the difficulty of their creative work with the explicatory demands of pedagogy. It takes as its main case study the way in which Jorie Graham's poetry exhibits a deep ambivalence about epistemological authority that can be meaningfully tied to the solidification of her academic career. Her work reveals a fundamental truth about the nature of academic discourse in the humanities: it affirms our sense that the dissemination of "critical thinking" is both necessary and socially relevant, while at the same time drawing itself away from sites of pedagogical disclosure, calling attention to the necessity of "obscured" modes of discourse both to the creative and to the academic-hermeneutic process. The simultaneity of this affirmation and anxiety is performed through the dialectical motions of secrecy and disclosure. Ultimately, Graham registers our best hopes for the possibilities of the creative writing program precisely insofar as she challenges the demand for rhetorical clarity and easily parsed choices of "craft" that have come to characterize many such programs. The central tension of this kind of "academic" poetry thus becomes one between the competing interests of the university as it comes to regulate both the consumption and production of literature.