• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 6
  • Tagged with
  • 148
  • 148
  • 148
  • 148
  • 56
  • 50
  • 44
  • 41
  • 41
  • 39
  • 38
  • 36
  • 35
  • 34
  • 33
  • 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.

Development of a Finite Element Model for Predicting the Impact Energy Absorbing Performance of a Composite Structure

Roberts, Matthew Lowell 01 June 2014 (has links)
Because of their high strength-to-weight ratio, Fiber Reinforced Composite (FRC) materials are well suited for use in high performance racing applications where weight must be kept to a minimum. Formula SAE (FSAE) race cars are designed and built by college students, roughly following the model of a scaled down Formula One car. Strict regulations are placed on specific components of the car in the interest of equalizing competition and ensuring the safety of the drivers. Students are required to construct a survival cell (the chassis), which can resist large amounts of energy in the event of a crash, with an energy absorbing device at the front of the vehicle. The nose cone of the Cal Poly FSAE car is constructed as a carbon fiber shell designed to act as this sacrificial energy absorbing device. One difficulty associated with using FRC materials is that the anisotropic properties can lead to a variety of complex failure modes such as buckling, delamination, matrix cracking, and fiber breakage, all of which absorb different amounts of energy. In order to accurately predict the behavior of the nose cone so that it meets the requirements set forth by SAE, an initial finite element model has been constructed. This model uses the test results from another paper to construct an explicit non-linear dynamic analysis in Abaqus which simulates the axial crushing of a thin walled composite tube between two rigid plates. The modeling techniques discussed in this paper will be used as the basis for a future thesis dedicated to designing the nose cone for the Cal Poly FSAE car.

Structure Climbing Monkey Robot

Bessent, Paul 01 June 2011 (has links)
This report describes the design, building, and testing of the Structure Climbing Monkey Robot (SCMR). It is composed of seven successive joints and linkages with two grippers at the two ends. Each gripper can act as the base or the end of the robot. The SCMR has the ability to climb any structure. The gripper plates can be changed to grab different kinds of structures, but this one is made to grab 2x4‘s. A program was written to assist the user to grab four non-coplanar, non-orthogonal points. The SCMR is actuated by a total of nine motors: two to open and close the two grippers and seven to control the movement of the SCMR. Planetary gear motors are used with a worm gear to control the motion of each joint. The worm gear increases the torque of the motor and reduces the rotational speed to a usable value. The SCMR is just over 45 inches long and weighs about 30 pounds. The motion of the SCMR is controlled by the microcontroller Arduino Mega 2560, Vex Robotic quadrature encoders, and Pololu 18v15 motor driver chips. Code was written in the languages Arduino and Processing to actuate the motors and create the GUI, respectively. The motors can be controlled individually or run simultaneously while incrementing a specified angle.


El-Achwah, Ahmad, Mr. 01 January 2019 (has links)
Aerosolized medications can potentially be delivered to the lungs of infants through a nasal cannula interface. However, nose-to-lung delivery technologies currently allow for ~1% of the loaded dose to reach an infant’s lungs. Conventional dry powder inhalers (DPI) are superior to other types of inhalers in many ways. However, passive DPIs that operate based on user inhalation and require large volumes of airflow are not applicable to infants. To overcome this challenge, positive pressure DPIs have been developed that enable aerosol delivery to infants. Unless an adequate nasal interface is used with these devices, a significant amount of drug will still be lost. Computational fluid dynamics (CFD) provide a method to assess the performance of a nasal cannula interface and optimize its performance. In this study, a CFD model was first experimentally validated using the low-Reynolds number k-ω turbulence model, then used to assess and optimize several conical diffuser cannula designs for infants. The performance of a cannula depends primarily on two requirements: the amount deposited particles and the cannula’s volume. It was found that 90 and 100 mm long simple diffusers achieved the necessary deposition and volume requirements when operated at 3 and 5 liters per minute, respectively. Additionally, including clean sheath co-flow air with the 70 mm long diffuser achieved the targeted performance requirements. Inclusion of recent advancements in the field with the recommended cannula designs is likely to improve pharmaceutical aerosol delivery to infants using the nose-to-lung approach.

Towards a Semantic Knowledge Management Framework for Laminated Composites

Premkumar, Vivek 23 November 2015 (has links)
The engineering of laminated composite structures is a complex task for design engineers and manufacturers, requiring significant management of manufacturing process and materials information. Ontologies are becoming increasingly commonplace for semantically representing knowledge in a formal manner that facilitates sharing of rich information between people and applications. Moreover, ontologies can support first-order logic and reasoning by rule engines that enhance automation. To support the engineering of laminated composite structures, this work developed a novel Semantic LAminated Composites Knowledge management System (SLACKS) that is based on a suite of ontologies for laminated composites materials and design for manufacturing (DFM) and their integration into a previously developed engineering design framework. By leveraging information from CAD/FEA tools and materials data from online public databases, SLACKS uniquely enables software tools and people to interoperate, to improve communication and automate reasoning during the design process. With SLACKS, this research shows the power of integrating relevant domains of the product lifecycle, such as design, analysis, manufacturing and materials selection through the engineering case study of a wind turbine blade. The integration reveals a usable product lifecycle knowledge tool that can facilitate efficient knowledge creation, retrieval and reuse, from design inception to manufacturing of the product.

A Prediction of the Acoustical Output of a Golf Driver Head Using Finite Elements

Sharpe, Roger 01 March 2010 (has links) (PDF)
A simulation was created using LS-DYNA® to determine the acoustical properties of a golf ball and golf driver head impact. LS-DYNA® has a coupled finite element analysis (FEA) and boundary element method (BEM) solver that uses the integral form of Helmholtz’s acoustic wave equation to deliver predicted sound pressure levels at predetermined acoustic points. Validation of the modeling was done on a simple plate donated by Titleist Golf. The plate was modeled and meshed using TrueGrid and impacted by a three layer golf ball model derived from “Tanka’s” paper on multilayered golf balls. The final converging model consisted of 10,900 solid fully integrated elements between the ball, plate, and plate support structure. The result was compared to experimental data taken by an air cannon and anechoic chamber that housed strain and acoustical measurement equipment. The sound level predictions from the model showed a promising correlation with experimental data and the focus switched to a golf driver head response during impact. The same ball developed from Tanaka’s paper was used to impact a 350cc generic golf driver head. The driver head consisted of 3300 fully integrated shell elements throughout the model. The top of the hosel was fixed during the simulation to simulate the connection to the golf shaft. The ball was fired at the center of the driver’s face and the predicted sound was determined for a point two feet behind the driver head. The BEM prediction of the driver head model showed little correlation with actual recorded impact sounds provided by Cleveland Golf when comparing frequency response functions. These differences could arise from assumptions and simplifications made to speed up the impact simulation. The sound produced from the golf ball after impact was one such factor was not included. Due to the complex shape of the driver head and the total number of elements involved, the numerical solution took upwards of 100 hours to finish. Adding the golf ball sound would greatly increase computational time and not contribute significantly to the overall predicted sound. Although the BEM solution can be used to characterize different driver heads, the impact is too complicated to efficiently and accurately predict the true impact sounds.


Chan, KC Thomas 27 July 2014 (has links)
<p>Computer simulation is widely used to predict the fatigue life of engine oil coolers that fail under pressure cycles. The objective of this study is to develop a practical simulation methodology to accurately predict the fatigue life of an engine oil cooler undergoing pressure cycle testing. The study focuses on two key areas of the simulation process. First, it investigates the effect of using linear and nonlinear FEA to provide stress or strain results for subsequent fatigue analysis. Second, due to lack of fatigue material properties for the aluminum coreplate material, approximate material models derived from tensile properties are used in fatigue life calculation. The study has attempted to find out the material model that gives the best correlation in life prediction. The life prediction correlation based on the Seeger, the Modified Universal Slopes and the Modified Mitchell models, together with the Modified Universal Slopes-Al model, are evaluated.</p> <p>It is concluded that the Modified Universal Slopes-Al model, which is a re-assessment of the Modified Universal Slopes model based on the fatigue data of 16 wrought aluminum alloys, gives the best life prediction for simulations using either linear or nonlinear approaches. Life prediction using nonlinear finite element results together with this approximate material model is recommended to be the best approach. On the other hand, a simple and quick linear analysis, followed by fatigue life calculation using this material model still gives life estimates with an acceptable level of confidence.</p> <p>In the last part of the study, the life prediction performance using different strain-life criteria, together with either Morrow or Smith-Watson-Topper (SWT) mean stress correction, are evaluated. It is found that SWT mean stress correction method is worse than that of Morrow in EOC fatigue life prediction in both linear and nonlinear approaches. Using the principal strain criterion with SWT mean stress correction gives conservative life prediction in both approaches. On the other hand, there are no significant differences in life prediction correlations using the principal strain, the Brown-Miller combined strain and the maximum shear strain strain-life criteria, with Morrow mean stress correction. As such, the Brown-Miller combined strain criterion with Morrow mean stress correction is the recommended strain-life model used in fatigue life calculation.</p> / Master of Applied Science (MASc)

Numerical Analysis of Fluid Flow and Heat Transfer in Atria Geometries

Kitagawa, Aaron T. 04 1900 (has links)
<p>The design, simulation, and analysis of a reference atrium using ComputationalFluid Dynamics (CFD) are presented. Atria geometries can be observed in manybuildings but their understanding from an energy perspective is not fully understood.Due to the many physical phenomena occurring within these atria, it is often difficult toassess the thermal comfort, energy consumption, and functionality of an atrium's design.The scale of an atrium’s structure coupled with dynamic physical phenomena creates acomplex problem to solve. One particular tool that is useful in solving for detailedenergy quantities is CFD. Validation studies have been conducted using previousexperimental atria data to ensure confidence in the predictions. These validation studieswere successful and also provided further insight on turbulence models, glazing systems,HVAC systems, thermal mass, and fluid flow and heat transfer behavior in atriageometries. A design for a reference atrium located in Toronto, Canada was thensimulated for typical summer and winter conditions using various configurations forglazing, solar heat flux, wall materials, occupant load, and HVAC. These simulationsprovide a realistic analysis of the reference atria and conclusions for the behavior of thereference atria are made.</p> / Master of Applied Science (MASc)


Mason, Michael A 01 January 2014 (has links)
The connection between contact geometry and fatigue in tapered roller bearings utilized in the railroad environment is still of interest. Roller bearings for railroad applications are typically precision ground with crowned contact geometries to prevent edge loading of components. This normally results in completely elastic Hertzian contact stresses under standard railcar loads. However, under extreme load conditions, detrimental edge loading has been known to occur. It is proposed to develop a tool, using finite element analysis, that can be utilized to optimize complex raceway crown geometries for severe applications. A successful implementation of this tool is presented and validated using proven Hertzian contact theory. Correlation within 5% of the ultimate surface and subsurface stress magnitudes, using finite element modeling, in contrast with proven contact theory is achieved. In addition, analyses of other load conditions and contact geometries in order to illustrate the practical application of the tool are exhibited.

Dust Transportation and Settling within the Mine Ventilation Network

Kumar, Anand 01 January 2019 (has links)
Dust is ubiquitous in underground mine activities. Continuous inhalation of dust could lead to irreversible occupational diseases. Dust particles of size lower than 75.0 µm, also known as float coal dust, can trigger a coal dust explosion following a methane ignition. Ventilation air carries the float coal dust from the point of production to some distance before it’s deposited on the surfaces of underground coal mine. Sources of dust are widely studied, but study of dust transportation has been mainly based on experimental data and simplified models. An understanding of dust transportation in the mine airways is instrumental in the implementation of local dust control strategies. This thesis presents techniques for sampling float coal dust, computational fluid dynamics (CFD) analysis, and mathematical modeling to estimate average dust deposition in an underground coal mine. Dust samples were taken from roof, ribs, and floor at multiple areas along single air splits from longwall and room and pillar mines. Thermogravimetric analysis of these samples showed no conclusive trends in float coal dust deposition rate with location and origin of dust source within the mine network. CFD models were developed using the Lagrangian particle tracking approach to model dust transportation in reduced scale model of mine. Three dimensional CFD analysis showed random deposition pattern of particle on the mine model floor. A pseudo 2D model was generated to approximate the distance dust particles travel when released from a 7 ft. high coal seam. The models showed that lighter particles released in a high airflow field travel farthest. NIOSH developed MFIRE software was adopted to simulate dust transportation in a mine airway analogous to fume migration. The simulations from MFIRE can be calibrated using the dust sampling results to estimate dust transportation in the ventilation network.

A Numerical Study in Prediction of Pressure on High-Speed Planing Craft during Slamming Events

Srivastava, Shivank 18 May 2018 (has links)
This thesis is an attempt to create a computer based tool that can be used academically and later industrially by naval architects in analysis and development of efficient planing hull forms. The work contained here is based on the theory created by Vorus (1996) which falls between empirical asymptotic solutions and intractable non-linear boundary value problem in the time-domain. The computer code developed predicts pressures on the bottom of high-speed planing craft during slamming events. The code is validated with available numerical data as a benchmark case. An aluminum wedge is dropped from various heights resulting in unsteady pressure distributions with high peak over the bottom plate. These pressure distributions are compared to the numerically predicted pressures by the code and presented in this thesis. The predicted flow velocities are within 8% difference of experimental data. The graphs depicts similar trends in experimental and numerical data. The predicted peak pressures deviate within 4% to 20% from experimental data. The analysis and comparison illustrate efficacy of the code.

Page generated in 0.1365 seconds