Thesis (Ph. D.)--Drexel University, 2005. / Includes abstract and vita. Includes bibliographical references (leaves [165]-180).

Vibration generated from main rotor unbalance has a major impact on the aerospace gas turbine industry. A combination of logistical and technological drivers differentiate aerospace gas turbines and their derivatives from other types of gas turbines with respect to the approach for managing vibration, leading to a bespoke approach for the design, build, and balancing. The key drivers are: limited accessibility to rotors within the engine, the requirement for exchangeable modules (sub-assemblies) of major parts of the rotor without rebalancing, the use of only low-speed balancing on pseudo-rigid rotors with bladed assemblies, very low vibration limits leading to very tight balancing limits, extreme weight limits for design solutions, and the need for highly accurate, repeatable, and stable rotor joints. This study proposes and demonstrates a novel and rapid robust design system that has been created to deal with these unique challenges. The system comprises an overarching process and a set of novel tools and methods that have been created to support the process. These tools comprise an Unbalance Response Function (URF) design method that effectively delivers a preliminary design assessment and a fast Monte-Carlo simulation and comparison method with supporting software for comparing and improving build and balance design solutions. The aim of the overall process is to generate a system that identifies and controls critical parameters, and alleviates time wasted controlling non-critical parameters. The target outcome is therefore the most cost effective, predictable and repeatable solution with respect to rotor generated vibration (i.e. robust). Two novel methods of informing and improving the outcome of the low-speed balancing process using extra information available about the rotor are also introduced.

Thesis (M.S.)--Rochester Institute of Technology, 1991. / Includes bibliographical references (leaves 105-109).

No description available.

M.Phil. / “Failure is one of the unfortunate facts of life”. This is the very first statement in the book by Coetzee (1998). This statement is unfortunately true, leading to the fact that failure is a reality, to be dealt with. Dealing with it in a proactive way will provide warnings of an approaching failure. Dealing with it in a reactive way will go through the “surprising pain” of an unexpected breakdown or downtime. In both cases the source of failure must be known to prevent it from happening again. Root Cause Analysis (RCA) is a structured method of determining the reason (root cause) of a failure. On the other hand, Vibration Analysis is one of the best known methods of condition monitoring and has the capability to indicate a reason for failure, although not necessarily the root cause or causes. The objective of this dissertation is to investigate the possibility to combine the RCA method with Vibration Analysis as forensic science to improve the success of finding root causes and their solutions.

In the development of engineering products, it is necessary to predict dynamic properties of the modified structures. Achieving such predictions by using the structural properties of the original structure and information on the modifications is commonly referred to as structural modification analysis. In this thesis, &Ouml / zg&uuml / ven&rsquo / s Structural Modification Method and Sherman-Morrison Method are selected as exact methods for structural modifications to predict the dynamics of a locally modified structure. Also, a new structural modification method named as &ldquo / Extended Successive Matrix Inversion Method&rdquo / is developed in this study. These three methods are implemented in a software developed herein, called &ldquo / Structural Modification Toolbox&rdquo / . The software uses modal analysis results of MSC Nastran&copy / for the original structure and calculates the modified frequency response functions by any of the methods above. In order to validate the software, direct modal analysis results of MSC Nastran&copy / for the frequency response functions of the modified structure are used. The methods are compared in terms of computational time, and the effectivity of each method is studied as a function of modification size to determine which of these methods is more suitable. In order to investigate the application of the methods and compare their results with experimental ones, modal tests are conducted on a scaled aircraft structure. The solutions are compared with test results obtained from modified test structure. Additionally, the software is used for comparison of real aircraft test results and frequency response functions of the modified structure.

Gait analysis is one of the primary applications of biomechanics and deals with scientific description of human locomotion, which is a qualitative concept as observed through the human eye. METU Gait Analysis Laboratory has been operating in various fields of gait and motion analyses since 1999. Although several studies have previously been undertaken about METU Gait Analysis System, until now, the effects of methodology and protocol related system parameters on kinematic analysis results have not been fully and exhaustively investigated. This thesis presents an assessment on sensitivity and compatibility of METU Gait Analysis Protocol to variations in experimental methodology and implementation of various joint center estimation methods, performed through investigation of the resulting joint kinematics. It is believed that the performance and reliability of METU Gait Analysis System will be improved based on the findings of this study.

The METU Gait Analysis System employs a computer program called Kiss-GAIT for the calculation of joint angles, moments and powers using force plate data and marker trajectories as input. Kiss-GAIT was developed using Delphi and is confined to calculations related to the standard gait protocol. Because the code lacks the flexibility required to carry out various test cases, the inverse dynamics formulation being used could not be verified and the extent of the error propagation problem could not be determined so far. The first aim of this study was to develop a code for the inverse dynamics model of the METU Gait Analysis System making use of the flexible programming environment provided by MATLAB. Verified and more reliable analysis results, obtained by reformulating the inverse dynamics algorithm in a new code, are presented. Secondly, data smoothing and differentiation techniques conventionally used in gait analysis were critically reviewed. A common tool used for filtering marker trajectories is the Butterworth digital filter. This thesis presents a modified, adaptive version of this classical tool that can handle non-stationary signals owing to its coefficients which are functions of local signal structure. The results of this thesis indicate the dominancy of ground reactions as compared to inertial effects in normal human gait. This implies that the accuracy needed in body segment inertial parameter estimation is not a critical factor. On the other hand, marker trajectories must be as accurate as possible for meaningful kinetic patterns. While any smoothing and differentiation routine that produces reasonable estimates is sufficient for joint moment calculation purposes, the estimation performance becomes a key requirement for the calculation of joint powers.

ABSTRACT DESIGN OF A MECHANISM FOR OPENING HACTHBACK CAR BAGGAGE DOOR Duran, Yusuf M.S., Department of Mechanical Engineering Supervisor: Prof. Dr. Eres S&ouml / ylemez September 2009, 65 Pages In this thesis, a new mechanism design for opening hatchback-car baggage door is introduced. Unlike the classical hinged doors used, this new design will include a mechanism so that the door will be opened vertically and thus occupy less space behind the car during the opening. In this fashion even the hatchback doors of closely parked cars may be opened. First, considering type synthesis, different mechanism types are investigated. In dimensional synthesis, with the help of Burmester theory, motion generation is applied. Using the circle and center point curves, considering link dimensions, transmission angle characteristics, branching and some order issues possible solutions that satisfy the position requirements are found. To actuate the mechanism, an appropriate gas-spring is sought. As a case study a prototype is manufactured and mounted on a sample hatchback car to check the mechanism performance.

The objective of this study is to present a dynamic model of a backhoe-loader including cab dynamics in order to simulate the vibration levels transmitted to the operator. For this purpose, analytical solutions of the cab and the machine are developed by deriving the equations of motion of the system and the state space forms of the solution are implemented in the commercially available simulation software, MATLAB/Simulink. In addition to the analytical solution, a model is developed using the physical modeling toolboxes of MATLAB/SimMechanics. Cab model developed in SimMechanics is extended to simulate whole machine dynamics by inserting machine body and tire parameters. Vibration data is acquired from the machine for experimental validation of the models. Analytical and SimMechanics solution are evaluated by comparing the seat acceleration results for the same inputs. Furthermore, simulation results obtained from the models and the measurement results are found to be in agreement in both time and frequency domain.