Mechanical Engineering Commons^™

Part Repair Using A Hybrid Manufacturing System, Kunnayut Eiamsa-Ard, Hari Janardanan Nair, Lan Ren, Jianzhong Ruan, Todd E. Sparks, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Nowadays, part repair technology is gaining more interest from military and industries due to the benefit of cost reducing as well as time and energy saving. Traditionally, part repair is done in the repair department using welding process. The limitations of the traditional welding process are becoming more and more noticeable when the accuracy and reliability are required. Part repair process has been developed utilizing a hybrid manufacturing system, in which the laser aided deposition and CNC cutting processes are integrated. Part repair software is developed in order to facilitate the users. The system and the software elevate the repair …

Freeze-Form Extrusion Fabrication Of Ceramics, Tieshu Huang, Michael S. Mason, Greg Hilmas, Ming-Chuan Leu

Materials Science and Engineering Faculty Research & Creative Works

A novel, environmentally friendly solid freeform fabrication method called Freeze-form Extrusion Fabrication (FEF) has been developed for the fabrication of ceramic-based components. The method is based on deposition of ceramic pastes using water as the media. The ceramic solids loading can be 50 vol. % or higher and initial studies have focused on the use of aluminum oxide (Al₂O₃). The FEF system components and their interaction are examined, and the main process parameters affecting part geometry defined. 3-D shaped components have been fabricated by extrusion deposition of the ceramic paste in a layer-by-layer fashion. The feasibility …

Sensitivity Analysis Of Process Parameters In Laser Deposition, Zhiqiang Fan, Kaushik Phatak, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In laser cladding with powder injection process, process output parameters, including melt pool temperature and melt pool dimensions, are critical for part quality. This paper uses simulation and experiments to investigate the effect of the process input parameters: laser power, powder mass flow rate, and scanning speed on the output parameters. Numerical simulations and experiments are conducted using a factorial design. The results are statistically analyzed to determine the significant factors and their interactions. The simulation results are compared to experimental results. The quantitative agreement/disagreement is discussed and further research is outlined.

Determination Of Dynamic Powder Modeling Parameters Via Optical Methods, Todd E. Sparks, Heng Pan, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Dynamic parameters, such as restitution and friction coefficients are important for powder flow simulations of laser based deposition processes. These parameters are difficult to find, especially for industrial metal powders. This paper introduces an optical method for measuring restitution and friction coefficients. The free falling powder flow was illuminated by a laser sheet. In order to obtain particle velocity, streaks proportional to particle velocities was generated by laser pulse obtained by a chopper. Recorded imaged were analyzed to determine particle velocities both before and after various impact conditions as well as impact parameters.

Workpiece Alignment For Hybrid Laser Aided Part Repair Process, Ajay Panackal Padathu, Todd E. Sparks, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Work piece alignment is a key issue for hybrid laser aided part repair,a process utilizing both machining and laser deposition.Proper alignment can greatly improve the accuracy of the repair process.This paper introduces a method for aligning a physical work piece and a CAD model using a Renis aw touch probe and software tools. Also discussed is a model for computing 5-axis CNC positions based on a desired work piece orientation.

Experimental Investigation Of The Travel-Time Variance Of An Acoustic Wave Propagating Through The Grid-Generated Turbulence, Tatiana A. Andreeva, William W. Durgin

Office of the Provost Scholarship

An experimental technique for the investigation of the behaviour of acoustic wave propagation through a turbulent medium is discussed. The present study utilizes the ultrasonic travel-time technique to diagnose a grid-generated turbulence. Travel-time variance is studied versus mean flow velocity, travel distance and outer turbulence scale. The effect of thermal fluctuations, which result in fluctuations of sound speed, is studied using a heated-grid experiment. Experimental data obtained using ultrasonic technique confirm numerical and theoretical predictions of nonlinear increase of the travel-time variance with propagation distance, which could be connected to the occurrence of caustics. The effect of turbulent intensity on …

Experimental Determination Of Probabilistic Edge-Delamination Strength Of A Graphite–Fiber/Epoxy Composite, Xiangfa Wu, Yuris A. Dzenis

Department of Engineering Mechanics: Faculty Publications

Probabilistic edge-delamination strength of a thermosetting polymer composite was studied experimentally in this work. During the procedure, by means of edge-delamination tensile test, the graphite–fiber/epoxy laminate made of unidirectional Toray P7051S- 20Q-1000 prepregs with an optimized lay-up of [12₂/–12₂/0₂]_S was used for examining its probabilistic distributions of the edgedelamination onset stress and the ultimate tensile strength. Acoustic emission (AE) equipment and optical microscope were utilized to capture the edge-delamination initiation and characterize the failure modes during delaminating. Fractographical analysis based on scanning electron microscope (SEM) was conducted for the characterization of the microscopic …

Crystal-Amorphous And Crystal-Crystal Phase Transformations Via Virtual Melting, Valery I. Levitas

Valery I. Levitas

A new mechanism of crystal (c)–amorphous (a) and c-c phase transformations (PTs) and internal stress relaxation via virtual melting (VM) induced by internal stresses was justified thermodynamically and kinetically. VM removes interface friction, reduces kinetic barrier, increases atomic mobility, and can reduce thermodynamic melting temperature. We combine VM and nonequilibrium PT diagrams to develop new scenarios of c-a and c-c PTs. Results are applied for a new interpretation of c-c and c-a PT mechanisms in ice Ih and are also applicable for other materials.

In-Situ High-Energy X-Ray Diffraction Study Of The Local Structure Of Supercooled Liquid Si, Robert Hyers, A. I. Goldman, K. F. Kelton, D. S. Robinson, J. R. Rogers, T. J. Rathz, A. K. Gangopadhyay, B. Sieve, G. W. Lee, T. H. Kim

Robert Hyers

Employing the technique of electrostatic levitation, coupled with high-energy x-ray diffraction and rapid data acquisition methods, we have obtained high quality structural data more deeply into the supercooled regime of liquid silicon than has been possible before. No change in coordination number is observed in this temperature region, calling into question previous experimental claims of structural evidence for the existence of a liquid-liquid phase transition.

Modeling, Fabrication, And Optimization Of Niobium Cavities Final Phase: Final Report, Robert A. Schill Jr., Mohamed Trabia, William Culbreth

Transmutation Sciences Materials (TRP)

This final report provides the activities and accomplishments of Modeling, Fabrication, and Optimization of Niobium Cavities – Final Phase. The fluid flow experiments for the etching of the superconducting cavity walls and baffle designs of phase II of the three phases has been completed leading to a MS thesis in December of 2003. Designing the experimental setup of secondary electron emission was well underway in early summer of 2003 when funding was made available for this portion of the study. By March 2004, many of the components of the experimental study reached UNLV with some assembly accomplished. The first secondary …

A Cartesian Space Approach To Teleoperate A Slave Robot With A Kinematically Dissimilar Redundant Manipulator, Hariharan Ananthanarayanan

Masters Theses

Due to the inability of humans to interact with certain unstructured environments,
telemanipulation of robots have gained immense importance. One of the primary tasks in telemanipulating robots remotely, is the effective manipulation of the slave robot using the master manipulator. Ideally a kinematic replica of the slave manipulator is used as the master to provide a joint-to-joint control to the slave. This research uses the 7-DOF Whole Arm Manipulator© (WAM) as the master manipulator and a 6-DOF Titan as the slave manipulator. Due to the kinematic dissimilarity between the two, a Cartesian space position mapping technique is adapted in which …

Evolutionary Algorithm For The Placement Of Fluid Power Valves On A Valve Stand, Trichy M. Kethara Pasupathy, Ravi Teja Seethamraju, Robert G. Wilhelm

Department of Mechanical and Materials Engineering: Faculty Publications

The choice of placement of fluid power valves on a valve stand and routing by pipes has an impact on operational costs. Choosing the right placement that provides optimum routing configuration or determining the optimum routing for a chosen placement are both computationally hard problems. An evolutionary algorithm (EA), to minimize operational costs while optimizing placement and routing of valves, is developed here. The best practices in the industry are abstracted and implemented in the EA. In this paper, the algorithm and its performance for examples with varying complexities are presented. Our results meet or exceed experienced designers’ solutions.

Reverse-Flow Oxidation Catalyst With Supplemental Fuel Injection For Lean-Burn Natural Gas Engines, Steven Scott Smith

Masters Theses

The purpose of this research is to demonstrate that the use of a reverse-flow oxidation catalyst reactor (RFOCR), both with and without supplemental fuel injection (SFI), will result in significant reductions of methane (CH4) in a simulated lean-burn natural gas exhaust mixture. Methane reduction is investigated as a function of the directional duration of the exhaust gases through the oxidation catalyst, gas hourly space velocity (GHSV), and exhaust gas temperature. The CH4 catalytic chemical reaction, at an elevated exhaust gas temperature, is an exothermic reaction and elevating the temperature across the catalyst reactor corresponds to an increase in CH4 conversion. …

Design And Characterization Of A Dual-Stage, Thermally Actuated Nanopositioner, Neal B. Hubbard, Larry L. Howell

Faculty Publications

A nanopositioner is presented that has two stages for independent coarse and fine position control. Thermal microactuators operate both stages. The first stage includes a bistable mechanism: it travels 52 micrometers between two discrete positions. The second stage is mounted on the first stage and moves continuously through an additional 8 micrometers in the same direction as the first stage. Three approaches to the control of the second stage were evaluated in terms of accuracy and manufacturability, and one was selected for the design of the nanopositioner. The device was surface micromachined in a two-layer polysilicon process. Experiments were performed …

Decentralized Perimeter Surveillance Using A Team Of Uavs, Timothy Mclain, Randal W. Beard, Derek Kingston, Ryan S. Holt, David W. Casbeer

Faculty Publications

This paper poses the cooperative perimeter-surveillance problem and offers a decentralized solution that accounts for perimeter growth (expanding or contracting) and insertion/deletion of team members. By identifying and sharing the critical coordination information and by exploiting the known communication topology, only a small communication range is required for accurate performance. Simulation and hardware results are presented that demonstrate the applicability of the solution.

Clinical Significance Of Hip Separation In Metal On Polyethylene, Metal On Metal, And Ceramic On Ceramic Tha Due To Resonant And Energy Dispersion Effects, Joseph Scott Bader

Masters Theses

Femoral head sliding within the acetabular cup does occur in THA. Since it is
known that impact conditions can lead to component ringing, the present study
investigates the vibrational response of variable bearing surface materials. A further understanding of the physical response resulting from impact during femoral head sliding may lead to valuable insight pertaining to THA failure.
Accelerometers were mounted to synthetic bones which had been implanted with hip prostheses. Data was collected from these sensors as a machine impacted the femoral head into the acetabular cup. These tests were carried out for metal-metal, ceramicceramic, and metal-polyethylene bearing surfaces …

Mechanical Design And Integration Of A Tracking Fluoroscope System, Robert Bradley Cunningham

Masters Theses

The Tracking Fluoroscope System (TFS) – patent pending serial number 60/606,480 – is a robotic platform designed to follow a patient's natural, uninhibited walking motion and obtain full-range-of-motion x-ray videos of a patient's ankle, knee, or hip. The video data can be used to analyze dynamics within the human body and develop mathematical models of the joints. The TFS can also be used to study artificial implants under various conditions in order to design more effective versions. Similar systems could be used to aid surgeons in artificial implant procedures. Athletic motions could be analyzed to design more effective sports equipment …

Robust Initial Matching Of Free-Form Objects Represented By Point Cloud Data, Nimun A. Jahangir

Digitized Theses

No abstract provided.

Improved Vehicle Based Multibeam Bathymetry Using Sub-Maps And Slam, Christopher Roman, Hanumant Singh

Christopher N. Roman

This paper presents an algorithm to improve sub-sea acoustic multibeam bottom mapping based on the simultaneous mapping and localization (SLAM) methodology. Multibeam bathymetry from underwater water vehicles can yield valuable large scale terrain maps of the sea door, but the overall accuracy of these maps is typically limited by the accuracy of the vehicle position estimates. The solution presented here uses small bathymetric patches created over short time scales in a sub-mapping context. These patches are registered with respect to one another and assembled in a single coordinate frame to produce a more accurate terrain estimate and provide improved renavigation …

High Temperature Heat Exchanger Project: Quarterly Progress Report April 1, 2005 Through June 30, 2005, Anthony Hechanova

Publications (NSTD)

Quarterly Collaboration Meeting. General Atomics hosted a UNLVRF HTHX Project quarterly meeting on June 5 in San Diego, California. The purpose of the meeting was to promote collaboration and communication among the UNLV Research Foundation partners. Collaborators had the opportunity to discuss their research program plan and update their progress. The next meeting will be in September in Berkeley hosted by UC Berkeley.

HTHX Computational Design (UNLV). Work on optimizing the ceramic offset strip in compact HTHX design through parametric studies was performed and completed. A simple single channel model was used to perform parametric studies on dimensions and flow …

Incorporating Computational Fluid Dynamics Into The Preliminary Design Cycle, Jonathan Knighton Shelley

Theses and Dissertations

Industry is constantly looking for ways to bring new or derivative products to market in the shortest amount of time for the least amount of money. To accomplish this, Industry has adopted Computer Aided Engineering (CAX) tools that perform structural, flow, manufacturing, and cost analysis. The way in which a company utilizes these CAX tools can determine the success of these new products. One of these tools that Industry often struggles with in the preliminary design of a product is Computational Fluid Dynamics (CFD). Some of the challenges presented by CFD are the time it takes to create a CAD …

Stability Analysis For Forging Of Porous Bodies, Xuan Wang, Eugene Olevsky, Alain Molinari

Industrial and Manufacturing Engineering

The continuum theory of sintering is used for the analysis of the stability of forging of a cylindrical powder specimen. The constitutive properties of the powder material are assumed to follow a power-law creep relationship. Temperature-coupled linear non-uniform stability analyses are carried out. Stability maps are obtained for forging of copper powder components.

Nesting Automated Design Modules In An Interconnected Framework, Jared Matthew Young

Theses and Dissertations

This thesis seeks to extend the PDG methodology by developing a generalized formal method for nesting PDGs in an interconnected system. A procedure for decomposing an individual PDG into reusable modules will be defined and a software architecture will be presented which takes advantage of these reusable modules. This method breaks the PDG structure into discrete elements known as PDG objects, PDG modules and PDG services. Each of these elements forms a distinct unit of reuse and each can be seen as a "little" PDG. Two different industrial implementations of this method are presented. These examples show that it is …

Experimental And Numerical Investigation Of Tool Heating During Friction Stir Welding, Joshua L. Covington

Theses and Dissertations

The heat input to the tool has been investigated for friction stir welding (FSW) of aluminum alloy AL 7075-T7351 over a wide range of process operating parameters using a combined experimental/numerical approach. In a statistical Design of Experiments fashion, 54 experimental welds (bead-on-plate) were performed at 27 different parameter combinations. Measured outputs during each of the welds included forces in all three coordinate directions and internal temperature of the rotating tool at three locations near the tool/workpiece interface. The heat input to the tool was also identified for each weld using infrared imaging temperature measurement techniques and the portion of …

Development Of A Weatherproof Windscreen For A Microphone Array, Jeffrey R. Hill

Theses and Dissertations

Microphone windscreens are typically used to reduce the noise associated with wind flowing over a microphone diaphragm by reducing the velocity of the airflow. While most windscreens are effective at reducing this noise, they do not protect the microphone from many natural elements, such as moisture, sand, and other small particles. The focus of this research was to design a windscreen that protects an array of five microphones located around a 4.5-inch diameter cylinder from these natural elements. The design goals were to have a wind noise attenuation of at least 8 dB, an insertion loss of less than 1 …

Visualizing And Interacting With Externally Coupled Engineering Analysis Results, Paul Frederick Nelson

Theses and Dissertations

Visualizing and interacting with engineering analysis results can provide valuable insights into a system's performance and aid in engineering decision-making. Currently, the majority of analysis codes are developed as isolated solutions focusing only on the most prominent physical influence to a system, such as thermal, structural, fluid, etc. Frequently, more than one of these physical influences combined to force engineers to evaluate complex, coupled systems. Coupled analysis codes are becoming more common place tools for engineers demanding high fidelity simulations of complex systems. External code coupling solutions are emerging to permit generic coupling of separate, world class CAE solvers thus …

System And Device For Characterizing Shape Memory Alloy Wires, Robert Ryan Vallance, Bruce L. Walcott, James E. Lumpp, Sumanth Chikkamaranahalli, Osamah A. Rawashdeh, Eric Wolsing

Mechanical Engineering Faculty Patents

Instruments and methods for measuring a property of a shape memory alloy are provided. The instrument includes a base plate, a non-contact movable mass, a force gauge, an actuator, a biasing spring, a heater for heating the shape memory alloy, and a non-contact displacement detector. The biasing spring and the shape memory alloy are disposed whereby a force applied thereby is applied substantially through a center of stiffness of the movable mass. The displacement detector measures a displacement of the movable mass in a colinear direction with a direction of movement of the movable mass and with a direction of …

Integrating Value Stream Mapping And Simulation, Michelle E. Scullin

Theses and Dissertations

An important principle in Lean manufacturing, value stream mapping (VSM) can be helpful in understanding how process flow and information flow affect each other. A VSM is a static picture of a process that allows the user to see where value is added into the value stream. Simulation is used to evaluate the behavioral issues of processes. In a manufacturing realm this means simulation shows how each operation affects other operations so determinations can be made about where bottlenecks or other problems exist in the process. Theoretically, the integration of VSM and Simulation can aide in process improvement by showing …

Vision-Based Target Localization From A Small, Fixed-Wing Unmanned Air Vehicle, Joshua D. Redding

Theses and Dissertations

Unmanned air vehicles (UAVs) are attracting increased attention as their envelope of suitable tasks expands to include activities such as perimeter tracking, search and rescue assistance, surveillance and reconnaissance. The simplified goal of many of these tasks is to image an object for tracking or information-gathering purposes. The ability to determine the inertial location of a visible, ground-based object without requiring a priori knowledge of its exact location would therefore prove beneficial. This thesis discusses a method of localizing a ground-based object when imaged from a fixed-wing UAV. Using the target's pixel location in an image, with measurements of UAV …

Ortho-Planar Mechanisms For Microelectromechanical Systems, Craig P. Lusk

Theses and Dissertations

A method for representing the design space of ortho-planar mechanisms has been developed. The method is based on the Theorem of Equality of Orientation Set Measures (TEOSM) which allows mechanisms to be represented by points in an abstract space. The method is first developed for single loop planar folded mechanisms with revolute joints, and later extended to mechanisms with prismatic joints and to spherical folded mechanisms. Functions which assign a value to each point in design space can be used to describe classes of mechanisms and evaluate their utility for MEMS design. Additionally, this work introduces the use of spherical …