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Articles 1 - 6 of 6

Full-Text Articles in Mechanical Engineering

Ultrasonic Flaw Classification And Sizing , Sung-Jin Song Jan 1991

Ultrasonic Flaw Classification And Sizing , Sung-Jin Song

Retrospective Theses and Dissertations

Flaw classification (determination of the flaw type) and flaw sizing (prediction of the flaw shape, orientation and sizing parameters) are very important issues in ultrasonic nondestructive evaluation of materials. In this work, new techniques for both classification and sizing are described;In the area of flaw classification, a methodology is developed which can solve classification problems in weldments using probabilistic neural networks. In the area of flaw sizing, four new approaches are presented including (1) the determination of distance-gain-size (DGS) curves and frequency response curves for flat-bottom holes based on a theoretical ultrasonic scattering model, (2) a time-of-flight equivalent (TOFE ...


Application Of The Boundary Element Method To Coupled Fluid-Structure Interaction Problems , Partha P. Goswami Jan 1991

Application Of The Boundary Element Method To Coupled Fluid-Structure Interaction Problems , Partha P. Goswami

Retrospective Theses and Dissertations

The direct boundary element method (BEM) is used to formulate and numerically simulate the interaction of acoustic waves with submerged elastic structures and subsequently specialized to model finite beam transmission through locally curved elastic surfaces. These are structural-acoustic or fluid-solid interaction problems coupling scalar (acoustic) and vector (elastic) media. The problem is formulated in the frequency domain and modelled in three dimensions, and the elasto-acoustic phenomenon described by the acoustic and elastodynamic boundary integral equations (BIE) with pressure and displacement serving as the primarily variables;The general problem deals with a closed solid domain surrounded by an unbounded fluid medium ...


An Open Loop Control Scheme To Minimize Flexible Robot Response Time While Minimizing Residual Vibrations , Wan-Shik Jang Jan 1991

An Open Loop Control Scheme To Minimize Flexible Robot Response Time While Minimizing Residual Vibrations , Wan-Shik Jang

Retrospective Theses and Dissertations

This study is to develop a practical control scheme called three-step input method whereby a flexible robot arm is moved from one position to another in the least amount of time with a minimum of residual vibration when the arm reaches its defined end point. The basic premise is to use open loop self-adjusting input signals that take system dynamic characteristics into account;In particular, the class of problem addressed in this thesis is restricted to the elimination of residual vibration when the fastest response is done in time steps of one half of the robot's fundamental natural period ...


Numerical Solution Of Inverse Problems In Mechanics Using The Boundary Element Method , Shuvra Das Jan 1991

Numerical Solution Of Inverse Problems In Mechanics Using The Boundary Element Method , Shuvra Das

Retrospective Theses and Dissertations

Due to the ill-posed nature of inverse problems, it is difficult to obtain solutions using well known analytical and numerical techniques. The use of boundary element method as a numerical technique to solve inverse problems is quite new. In this work, the algorithms for the solution of two kinds of inverse problems are examined in detail. For the first kind, the shape and location of a part of the boundary is unknown; and for the second kind, the boundary condition is not specified on a part of the boundary;Boundary value problems with partially unknown boundary are ill-posed. To solve ...


Application Of The Boundary Element Method To Elastic Wave Scattering Problems In Ultrasonic Nondestructive Evaluation , Paul Jay Schafbuch Jan 1991

Application Of The Boundary Element Method To Elastic Wave Scattering Problems In Ultrasonic Nondestructive Evaluation , Paul Jay Schafbuch

Retrospective Theses and Dissertations

The boundary element method (BEM) is used to numerically simulate the interaction of ultrasonic waves with material defects such as voids, inclusions, and open cracks. The time harmonic formulation is in 3D and therefore allows flaws of arbitrary shape to be modeled. The BEM makes such problems feasible because the underlying boundary integral equation only requires a surface (2D) integration and difficulties associated with the seemingly infinite extent of the host domain are not encountered. The computer code utilized in this work is built upon recent advances in elastodynamic boundary element theory such as a scheme for self adjusting integration ...


Drag On Object Moving Through Foam , Chinwha Chung Jan 1991

Drag On Object Moving Through Foam , Chinwha Chung

Retrospective Theses and Dissertations

Foams consist of small gas bubbles separated by thin liquid films. Although many complex models have been developed to describe the rheological properties of foam, very little information is available concerning the flow charateristics of foam flowing past an object. The purpose of this research was to investigate foam flow properties by performing simple experiments to determine the drag charateristics of simple-shaped bodies moving through foam;A rotating tank apparatus was built and used as the equivalent of a wind tunnel in aerodynamic testing. Foam with consistent properties was produced and models of various shapes were suspended in the moving ...