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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Numerical Investigation of Gas-Particle Supersonic Flow

Samel, Mihir A 01 January 2011 (has links) (PDF)
No description available.
2

Signals as Symbols: Applying Normalization of Deviance to Improve User-Centered Design

Vanschaik, Amy 01 January 2021 (has links) (PDF)
Mistakes can happen in the process of designing and developing interactive digital projects. Sometimes these mistakes negatively impact users' perception and trust of digital interfaces. This research applies the concept of normalization of deviance to identify potential missed opportunities in user-centered design data within the context of a website redesign. By doing this I explore how through observing accidental deviant behaviors or processes we can identify ways to improve the usability and user experience of digital environments. I review the concepts of normalized deviant behavior as addressed by Diane Vaughan in the field of engineering and identify a process for applying this against a user research study. This process is explored through a re-analysis of user data collected from the redesign of a library catalog interface. My work focuses on identifying missed and weak signals in the research process. By noting these overlooked signals, I argue for improving the digital design process through implementing extra checks for normalized deviant behavior.
3

Simulating Particle Packing During Powder Spreading for Selective Laser Melted Additive Manufacturing Using the Discrete Element Method in Abaqus

Ng, Priscilla 01 June 2020 (has links) (PDF)
Metal additive manufacturing allows for the rapid production of complex parts that are otherwise impractical using conventional subtractive manufacturing techniques. Applications for additive manufacturing span across a broad array of industries including aerospace, automotive, and medical, among many others. One metric of printing success is material properties, including part density. While there has been extensive research completed for the density of printed parts, there is little published work concerning powder packing density on the build plate associated with powder spreading. In this thesis, a Discrete Element Method (DEM) model was created in Abaqus to simulate the spreading behavior of particles through a single sweep of a spreader blade . Spreading behavior was investigated for three different build plate configurations: a flat build plate, a build plate with a small protruding feature, and a build plate with the same protruding feature split into quarters. For each configuration, the 2D packing behavior of the particles were analyzed during the powder spreading process. Different packing patterns seen in the 2D packing behavior were further analyzed to determine particle packing density, analogous to unit cell packing, and to predict 3D packing behavior and packing density. Additionally, particle packing density was measured following simulation using 2D image analysis to quantify powder spreading around, and interaction with, previously fused structures on the build plate. We found that the local packing fraction is measurably disrupted when particles interact with build plate features, providing insights into part density and short loading during part fabrication.
4

Development of rear-end collision avoidance in automobiles

Dravidam, Uttamkumar 07 December 1999 (has links)
The goal of this work is to develop a Rear-End Collision Avoidance System for automobiles. In order to develop the Rear-end Collision Avoidance System, it is stated that the most important difference from the old practice is the fact that new design approach attempts to completely avoid collision instead of minimizing the damage by over-designing cars. Rear-end collisions are the third highest cause of multiple vehicle fatalities in the U.S. Their cause seems to be a result of poor driver awareness and communication. For example, car brake lights illuminate exactly the same whether the car is slowing, stopping or the driver is simply resting his foot on the pedal. In the development of Rear-End Collision Avoidance System (RECAS), a thorough review of hardware, software, driver/human factors, and current rear-end collision avoidance systems are included. Key sensor technologies are identified and reviewed in an attempt to ease the design effort. The characteristics and capabilities of alternative and emerging sensor technologies are also described and their performance compared. In designing a RECAS the first component is to monitor the distance and speed of the car ahead. If an unsafe condition is detected a warning is issued and the vehicle is decelerated (if necessary). The second component in the design effort utilizes the illumination of independent segments of brake lights corresponding to the stopping condition of the car. This communicates the stopping intensity to the following driver. The RECAS is designed the using the LabVIEW software. The simulation is designed to meet several criteria: System warnings should result in a minimum load on driver attention, and the system should also perform well in a variety of driving conditions. In order to illustrate and test the proposed RECAS methods, a Java program has been developed. This simulation animates a multi-car, multi-lane highway environment where car speeds are assigned randomly, and the proposed RECAS approaches demonstrate rear-end collision avoidance successfully. The Java simulation is an applet, which is easily accessible through the World Wide Web and also can be tested for different angles of the sensor.
5

Pressure Disturbance Upstream of the Boundary Layer Data System

Leclere, Michelle S 01 July 2022 (has links) (PDF)
The primary objective for this work was to evaluate the reliability of computational fluid dynamics (CFD) tools in the prediction of upstream surface pressure disturbance and pressure drag of various instrument excrescence shapes for a small aircraft flight test device called the Boundary Layer Data System (BLDS). Insights on pressure disturbance will serve as a guide for the placement of BLDS probes/sensors, and pressure drag can be used to ensure sufficient adhesive is used to install BLDS instrumentation. The Mach number for all CFD cases was 0.12 and the Reynolds number based on excrescence height varied from 4 x 104 to 1 x 105. Excrescences studied have height to local boundary layer thickness ratios 0.75 < h/d < 1.9 and width to height ratios 3 ≤ w/h < 4. Wind tunnel tests were first conducted in the Cal Poly Fluids Lab’s 2 x 2-foot wind tunnel to obtain measurements of the upstream pressure disturbance created by a blunt BLDS housing and a streamlined BLDS fairing. Upstream surface pressure data was measured for two-dimensional excrescences and for three-dimensional models of the blunt and streamlined housings. A rake measurement of the undisturbed boundary layer profile at the leading edge location of each excrescence was also obtained to compare to the computed boundary layer. Prior to viscous modeling with CFD, potential flow theory was used to compute the inviscid upstream pressure disturbance for a generic excrescence on a smooth surface. A Rankine oval was generated using superposition, and a MATLAB program was written to evaluate ovals of varying chord and height. The potential flow results for the pressure distribution upstream of a Rankine oval were found to agree quite well with 2-D measurements and viscous CFD. Ansys ICEM CFD and FLUENT were used for computational modeling. A viscous CFD model was first created in two-dimensions and validated by comparing the upstream pressure disturbance results to the two-dimensional experimental measurements. The validated FLUENT case set-up was extended to three-dimensions, and three-dimensional models were created for blunt and streamlined BLDS excrescences. ICEM CFD was used to generate meshes for 2-D and 3-D models and FLUENT was used to solve the Reynolds-Averaged Navier Stokes (RANS) equations in conjunction with the Spalart-Allmaras turbulence model. Mesh independence studies and evaluation of discretization error were conducted to ensure that the final mesh employed provided adequate spatial resolution. The computed flow features, and results for dimensionless pressure and drag, were compared to experimental measurements and classic aerodynamic principles to evaluate the CFD solutions. It was concluded that CFD can accurately compute upstream pressure disturbances and pressure drag for excrescences mounted to a smooth surface. The viscous calculations showed that the effect of excrescence shape on upstream pressure field is only significant within 6 body heights of the leading edge. Beyond that, no significant difference in the pressure disturbance was observed between different excrescence configurations. Additionally, the spanwise pressure disturbance was found to become negligible at about 1-1.5 housing widths away from the upstream centerline of each excrescence regardless of its shape. Finally, all computed blunt housing models resulted in a pressure drag coefficient of about 0.5 which corroborates past experimental drag measurements. This thesis has set-up a working FLUENT CFD case that can be used for future computational studies related to the BLDS and provides detailed guidance for existing BLDS housing shapes beyond the rules of thumb currently used for informing housing designs.
6

Structural Analyses of Wind Turbine Tower for 3 kW Horizontal Axis Wind Turbine

Gwon, Tae Gyun 01 August 2011 (has links) (PDF)
Structure analyses of a steel tower for Cal Poly's 3 kW small wind turbine is presented. First, some general design aspects of the wind turbine tower are discussed: types, heights, and some other factors that can be considered for the design of wind turbine tower. Then, Cal Poly's wind turbine tower design is presented, highlighting its main design features. Secondly, structure analysis for Cal Poly's wind turbine tower is discussed and presented. The loads that are specific to the wind turbine system and the tower are explained. The loads for the static analysis of the tower were calculated as well. The majority of the structure analysis of the tower was performed using the finite element method (FEM). Using Abaqus, commercial FEM software, both static and dynamic structural analyses were performed. A simplified finite element model that represents the wind turbine tower was created using beam, shell, and inertia elements. An ultimate load condition was applied to check the stress level of the tower in the static analysis. For the dynamic analysis, the frequency extraction was performed in order to obtain the natural frequencies and the mode shapes of the tower. Using the results, the response spectrum analysis and the transient dynamic analysis, which are based on the modal superposition method, were performed in order to see the structure's response for earthquakes that are likely to happen at the wind turbine installation site.
7

Predicting the Acoustic Response of the Golf Club & Ball Impact Using Finite Elements and the Boundary Element Method

Moreira, Scott Henry 01 December 2011 (has links) (PDF)
An improved and repeatable method for meshing golf club heads using finite elements in TrueGrid® was developed. Using solid brick elements through the thickness of the club head instead of shell elements better represents the many thickness variations throughout each section of a club head. This method also results in a high quality mesh at the center of the club head sections while still maintaining high quality at the edges. A simulation procedure was also developed to predict the acoustic pressure at a designated point in an acoustic medium of a golf club and ball impact using the BEM and Rayleigh methods in LS-DYNA®. The simulation time and computing power required for the impact are modest, while the acoustic simulation time and computing power are much greater. The Rayleigh method provides an alternative which can greatly reduce these requirements. The simulation of sound produced from the ball and a USGA COR plate, generic driver, and hybrid impact was accomplished with reasonable results. Experimental testing was performed using a USGA plate to validate the plate result. A simple tap test and an air cannon test were performed to record the acoustic response with a microphone. A Fast Fourier Transform was performed to obtain the frequency response. These two tests correlated with each other, indicating that air cannon procedures could be negated in favor of a much simpler tap test during prototype testing for acoustics. The simulation frequency responses showed similar results to the experimental tests, demonstrating that the procedure developed in this project can be a viable and effective method for determining the acoustic response of the golf club and ball impact.
8

Engineering Analysis in Imprecise Geometric Models

Gasparini, Riccardo 01 December 2014 (has links)
Engineering analysis in geometric models has been the main if not the only credible/reasonable tool used by engineers and scientists to resolve physical boundaries problems. New high speed computers have facilitated the accuracy and validation of the expected results. In practice, an engineering analysis is composed of two parts; the design of the model and the analysis of the geometry with the boundary conditions and constraints imposed on it. Numerical methods are used to resolve a large number of physical boundary problems independent of the model geometry. The time expended due to the computational process are related to the imposed boundary conditions and the well conformed geometry. Any geometric model that contains gaps or open lines is considered an imperfect geometry model and major commercial solver packages are incapable of handling such inputs. Others packages apply different kinds of methods to resolve this problems like patching or zippering; but the final resolved geometry may be different from the original geometry, and the changes may be unacceptable. The study proposed in this dissertation is based on a new technique to process models with geometrical imperfection without the necessity to repair or change the original geometry. An algorithm is presented that is able to analyze the imperfect geometric model with the imposed boundary conditions using a meshfree method and a distance field approximation to the boundaries. Experiments are proposed to analyze the convergence of the algorithm in imperfect models geometries and will be compared with the same models but with perfect geometries. Plotting results will be presented for further analysis and conclusions of the algorithm convergence
9

Geometrically Adaptive Milling of Fan Blade Assembly Weld Fillets

Lin, Yu Pin 10 1900 (has links)
<p>Modern aeroengine design focuses on reducing overall weight and improving component service life. For fan blade assemblies, the blades and hub/shaft are attached by the most common dovetail (or fir tree) attachment design, which experiences fretting fatigue at the joint resulting in lower reliability and higher repair difficulty. A new joining design that connects blade /disk by welding and eliminates the attachment, has been implemented in military and commercial aeroengines. This joining design is most suitable for large diameter fan blades where single piece machining is impractical and time consuming. The joined blade requires post-process machining to remove excess weld material. However, because of varying assembly geometry, joints must be individually measured and tool paths consequently adjusted to match actual surface locations. The objective of this thesis is to develop an automated and geometrically adaptive post-process weld machining system.</p> <p>This thesis proposes a solution that integrates surface digitization, computer aided design (CAD) and computer aided manufacturing (CAM) systems, to accommodate the part-to-part variation issue. The integrated system includes precise laser digitizing, geometric modelling, tool path customizing, coordinate registration and CNC machining. The core algorithm was designed on the open and object-oriented C++ ACIS/HOOPS kernel. The customized tool paths are prepared based on the misalignment distance measured by laser digitizing, and a custom developed mathematical correction algorithm that can be implemented on a typical personal computer. At present, the machining process is designed for a three-axis machine tool. Suggested future works include implementation on a five-axis machine, and feed rate optimized tool paths.</p> / Master of Applied Science (MASc)
10

Integration of Machining Inspection Sensors and Software

Sawula, Alan D. 04 1900 (has links)
<p>Ideally, the nominal design of a part or assembly, created with 3D Computer-Aided Design and Manufacturing (CAD/CAM) software, can be consistently fixtured and machined. In reality, process conditions vary, and feedback and correction methods such as integrated on-machine inspection, analysis, and process adjustment, are required.</p> <p>On-machine inspection based on touch trigger probes is well established, but limited motion control computing capability restricts analysis to simple arithmetic. This prevents on-line use of known whole part mathematical analysis software that implements the part salvaging intentions of modern Geometric Dimensioning and Tolerancing (GD&T) standards. Additionally, no CNC integrated method exists for geometrically adjusting nominal tool paths so that an in-tolerance final part is produced. Machine tool support for high data rate sensors such as laser scanners is also lacking.</p> <p>This thesis reports progress towards bidirectional integration of machine tool mounted inspection sensors with GD&T analysis software, and subsequent toolpath adjustment. The concepts are demonstrated using a fixture consisting of three datum spheres and a workpiece. The fixture is clamped in the CNC machine, datum spheres are measured, and after mathematical data fitting and registration, an in-tolerance final part is produced. To facilitate multiple tests, a tool path is split into four and machined in four poses with measurement and tool path adjustment for each pose. Preliminary integration of a laser scanner with axis scales and computer software was also accomplished.</p> / Master of Applied Science (MASc)

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