Thesis (award) -- University of Western Sydney, 2005. / Includes bibliography.

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 131-134).

Athletic performance is an important factor to consider when designing athletic footwear. Improvements in agility drill performance can lead to improved sports performance. Changing footwear characteristics can be one way to help improve performance. The design and materialization of the upper of a shoe can impact biomechanical metrics and needs to be further explored during agility movements. Therefore, the first purpose of this study was to investigate the impact that stiffening the upper panel of an athletic shoe could have on agility performance using biomechanical outcome measures that correlate with athletic performance. Stiffening the upper panel significantly altered contact time during the lateral skater jump with the stiffest shoe having the shortest contact time compared to the other two shoe stiffness conditions (p=0.020-0.046). Shoe upper panel stiffness significantly changed peak concentric power in the anterior-posterior drill where the least stiff shoe produced the highest power compared to the stiffest shoe (p=0.006). The same dataset was used to address the second goal of this study which was to model the foot and ankle complex as a system of gears to understand force attenuation and propulsion during agility tasks. Although no differences were found between footwear conditions in gearing, it was shown that modeling the foot and ankle system through gearing can advance our understanding of the impact that footwear changes can have on performance and may be an important outcome measure in future footwear studies. / Master of Science / Athletic performance is an important factor to consider when designing athletic footwear. Through changes in shoe design, it is possible to improve agility drill performance. The design and materials used to construct the upper (top portion of the shoe) of the shoe can change the way an athlete completes a task and therefore, these measures need to be explored during several agility movements. The first goal of this study was to determine the impact of stiffening the upper portion of an athletic shoe on agility performance using outcome measures that are associated with improved athletic performance. Stiffening the upper portion of the shoe altered the contact time during the lateral skater jump with the stiffest shoe having the shortest contact time compared to the other two shoe conditions. Shoe upper panel stiffness also impacted peak concentric power in the anterior-posterior drill where the least stiff shoe produced the highest power compared to the stiffest shoe. The same dataset was used to model the foot and ankle as a system of gears in order to understand how an individual absorbs force and then utilizes force to move the body forward or to the side when completing agility tasks. Although no differences were found between footwear conditions when assessing gearing, it was shown that modeling the foot and ankle system in this way could aid in the understanding of how footwear changes can alter performance.

An interactive program is presented which enhances the design of external spur gears cut by a hob. The program code calculates the geometry of an involute spur gear with trochoidal fillets and then uses the Graphical Kernel System (GKS), CADAM, and MOVIE.BYU to represent and display the gear. GKS, an international standard, is used to represent the gear in two dimensions; while the CAD/CAM system CADAM and the software package MOVIE.BYU accurately create wireframe geometric design models in three dimensions. Examples of the input parameters needed and each of the software packages in use are shown and explained. / M.S.

An analysis of the influence of undercutting on the stress concentration factor for undercut gears using the finite element method is presented. The models used are in the shape of a whole gear with three teeth. The middle tooth is loaded assuming single-tooth contact. Thirty seven finite element models were used to compute stress concentrations in gear teeth. The results for non-undercut gears were compared with the Dolan and Broghamer results, and were not more than 9.5 percent different. The results are expressed in the form of a linear relationship giving the stress concentration factor at the root fillet as a function of the geometry of the tooth. It has been verified that this equation is an accurate formula for both undercut and non-undercut gears with nominal proportions. / Master of Science

The problem of the deflection of spur gear teeth has been previously investigated analytically by several authors. Two of the papers dealing with this topic were written by Timoshenko and Baud (18)t and Marin and Shenk (11). Both papers employ the cantilever beam approach in which the spur gear tooth is represented as a rigidly supported, cantilever beam of uniform thickness tapered in the plane of load application. Deflection is considered to be caused by bending moment, shearing force, and Hertzian pressure at the point of load application. Two additional papers were written by Weber (25) and Attia (3) in which the actual involute gear tooth was considered to be an elastically supported cantilever beam rather than rigidly clamped at the root of the tooth. Likewise, circumferential deformation of the gear body was considered. However, the derived equations for the total deflection due to these effects are exceedingly complicated and require the use of numerical methods for their solution since some of the equations are in integral form. / Master of Science

As pointed out in the “Discussion of Results”, the sub-surface stresses in a gear tooth decrease very rapidly with its depth. This result serves as a supporting evidence to the common practice of case-hardening the gear teeth. Previously this was done according to the mechanical properties of the gear materials, but without any analytical basis. Gear stress is a very complicated problem which includes in general the static, dynamic and fatigue stresses. Most of all, many uncertainties in service such as the impact load, acceleration load and work hardening are involved. These uncertainties make it difficult to get a general solution. The photoelastic method is an effective one for making a static study of gear stress, but it is understood that this method can not solve the whole problem, Since if the static stresses are considered further studies covering the notch sensitivity, friction effect, dynamic effect, and load distribution are still needed. / Master of Science

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Masters of Science in Engineering. University of the Witwatersrand, Johannesburg, 2016 / With the current tough economic times and depressed commodity prices, focus is being placed on achieving higher power densities in gears without increased cost or reduced achievable life and reliability. An investigation into the use of different carburisation methods and processes to minimise post heat treatment distortion, with the aim to reduce and even eliminate the requirement for post heat treatment grinding and grinding stock allowances is presented. The investigation included the processing of test pieces, as per the recommendations of AGMA 2004-B89: Gear Materials, Heat Treatment and Processing Manual. Four alloy steels, namely AISI 3310, AISI 8620, AISI 9310 and 17CrNiMo6, were selected for this research, based on availability, cost and hardenability. The carburising cycles were derived for both gas and vacuum carburising for a 0.10% and 0.20% carbon steel respectively. Two quenching options were applied, oil quenching and intensive quenching. The test pieces were 3-dimensionally measured to determine distortion through the changes in diameter and ovality. The microstructures of the case and core were analysed, as well as effective case depth. This research found that current methods, atmospheric carburising and oil quenching, and steel alloy combinations are inadequate to produce low distortion carburised internal gears, while the use of vacuum carburising and intensive quenching as a process combination can achieve such gears. It was also found that the use of AISI 3310, performed the best for both current and proposed process combinations. It is recommended that future work be conducted, including a full-scaled manufacturing trial with more detailed process adjustments to ensure the quality and repeatability of the final carburised gear. / MT2017

The primary objective of the research reported in this thesis was the improvement of safety in helicopters by identifying and, where necessary, developing vibration analysis techniques for the detection and diagnosis of safety critical faults in helicopter transmission systems. A review and, where necessary, expansion of past research is made into (a) the mechanisms involved in the production of vibrations in mechanical systems, (b) the failure modes experienced in geared transmission systems, (c) which failure modes are critical to the safety of helicopters, (d) how the safety critical failure modes affect the vibration signature, and e) the vibration analysis techniques currently used to detect safety critical failures. The effectiveness of the currently available vibration analysis techniques is investigated using in-flight vibration data from Royal Australian Navy helicopters and seeded fault data from a purpose built spur gear test rig. Detailed analysis of techniques for synchronous signal averaging of gear vibration data is undertaken, which includes the development of new methods of modelling and quantifying the effects of synchronous averaging on non-synchronous vibration. A study of digital resampling techniques is also made, including the development of two new methods which provide greater accuracy and/or efficiency (in computation) over previous methods. A new approach to fault diagnosis is proposed based on time-frequency signal analysis techniques. It is shown that these methods can provide significant improvement in diagnostic capabilities over existing vibration analysis techniques. Some limitations of general time-frequency analysis techniques are identified and a new technique is developed which overcomes these limitations. It is shown that the new technique provides a significant improvement in the concentration of energy about the instantaneous frequency of the individual components in the vibration signal, which allows the tracking of small short term amplitude and frequency modulations with a high degree of accuracy. The new technique has the capability of 'zooming' in on features which may span only a small frequency range, providing an enhanced visual representation of the underlying structure of the signal.

Thesis (M.S.)--Ohio University, March, 1998. / Title from PDF t.p.