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Optimal Modeling of Knots in Wood

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A model has been developed to modify Euler-Bernoulli beam theory for wooden beams, using visible properties of wood knot-defects. Treating knots in a beam as a system of two ellipses that change the local bending stiffness has been shown to

A model has been developed to modify Euler-Bernoulli beam theory for wooden beams, using visible properties of wood knot-defects. Treating knots in a beam as a system of two ellipses that change the local bending stiffness has been shown to improve the fit of a theoretical beam displacement function to edge-line deflection data extracted from digital imagery of experimentally loaded beams. In addition, an Ellipse Logistic Model (ELM) has been proposed, using L1-regularized logistic regression, to predict the impact of a knot on the displacement of a beam. By classifying a knot as severely positive or negative, vs. mildly positive or negative, ELM can classify knots that lead to large changes to beam deflection, while not over-emphasizing knots that may not be a problem. Using ELM with a regression-fit Young's Modulus on three-point bending of Douglass Fir, it is possible estimate the effects a knot will have on the shape of the resulting displacement curve.

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Date Created
2015-05

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Reconciling the differences between tolerance specification and measurement methods

Description

Dimensional Metrology is the branch of science that determines length, angular, and geometric relationships within manufactured parts and compares them with required tolerances. The measurements can be made using either manual methods or sampled coordinate metrology (Coordinate measuring machines). Manual

Dimensional Metrology is the branch of science that determines length, angular, and geometric relationships within manufactured parts and compares them with required tolerances. The measurements can be made using either manual methods or sampled coordinate metrology (Coordinate measuring machines). Manual measurement methods have been in practice for a long time and are well accepted in the industry, but are slow for the present day manufacturing. On the other hand CMMs are relatively fast, but these methods are not well established yet. The major problem that needs to be addressed is the type of feature fitting algorithm used for evaluating tolerances. In a CMM the use of different feature fitting algorithms on a feature gives different values, and there is no standard that describes the type of feature fitting algorithm to be used for a specific tolerance. Our research is focused on identifying the feature fitting algorithm that is best used for each type of tolerance. Each algorithm is identified as the one to best represent the interpretation of geometric control as defined by the ASME Y14.5 standard and on the manual methods used for the measurement of a specific tolerance type. Using these algorithms normative procedures for CMMs are proposed for verifying tolerances. The proposed normative procedures are implemented as software. Then the procedures are verified by comparing the results from software with that of manual measurements.

To aid this research a library of feature fitting algorithms is developed in parallel. The library consists of least squares, Chebyshev and one sided fits applied on the features of line, plane, circle and cylinder. The proposed normative procedures are useful for evaluating tolerances in CMMs. The results evaluated will be in accordance to the standard. The ambiguity in choosing the algorithms is prevented. The software developed can be used in quality control for inspection purposes.

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Created

Date Created
2014

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Conceptual Composite Wing Design

Description

Automation has become a staple in high volume manufacturing, where the consistency and quality of a product carries as much importance as the quantity produced. The Aerospace Industry has a vested interest in expanding the application of automation beyond simply

Automation has become a staple in high volume manufacturing, where the consistency and quality of a product carries as much importance as the quantity produced. The Aerospace Industry has a vested interest in expanding the application of automation beyond simply manufacturing. In this project, the process of systems engineering has been applied to the Conceptual Design Phase of product development; specifically, the Preliminary Structural Design of a Composite wing for an Unmanned Air Vehicle (UAV). Automated structural analysis can be used to develop a composite wing structure that can be directly rendered in Computer Aided Drafting (CAD) and validated using Finite Element Analysis (FEA). This concept provides the user with the ability to quickly iterate designs and demonstrates how different the “optimal light weight” composite structure must look for UAV systems of varied weight, range, and flight maneuverability.

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Created

Date Created
2021

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Detailed Analysis of Liquid Ligament Breakup

Description

Multiphase flows are relevant to various industrial processes and are also a ubiquitous feature of nature. Atomization is a Gas-Liquid class of multiphase flow in which the liquid bulk disintegrates into a spectrum of drops. The final drop size distribution

Multiphase flows are relevant to various industrial processes and are also a ubiquitous feature of nature. Atomization is a Gas-Liquid class of multiphase flow in which the liquid bulk disintegrates into a spectrum of drops. The final drop size distribution of fragmenting liquids is important and is crucial to quantifying the performance of atomizers. This thesis implements two models of ligament breakup. The first model provides a method to determine the droplet size distribution of fragmenting ligaments. The second model provides a relation between ligament stretching, aspect ratio and dimensionless properties like Ohnesorge and Weber numbers for ligaments being stretched by aerodynamic force. The first model by Villermaux et.al considers a ligament as a linear succession of liquid blobs which undergo continuous interplay during destabilization. The evolution of their size distribution ultimately rules the droplet size distribution which follow a gamma distribution [14]. The results show that the Direct Numerical Simulations (DNS) of ligaments with different perturbations fragmented into very few drops and cannot be used to confirm that they follow the predicted gamma distribution. The second model considers a ligament breakup due to Rayleigh-Plateau Instability and provides an equation for ligament stretching. Through test runs the proportionality constant in the equation is determined by a least square fit. The theoretical number of drops is compared with the number of drops resulting from the Direct Numerical Simulation of ligament with a sinusoidal perturbation. It is found that the wavelength of the initial perturbation does not determine the number of drops obtained by ligament breakup

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Created

Date Created
2021

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Design of Wings for Jump Gliding in a Biped Robot

Description

This thesis aims to design of wings for a laminate biped robot for providing locomotion stabilization during jump gliding. The wings are designed to collapse down during the jumping phase to maximize jump height and deployed back for gliding phase

This thesis aims to design of wings for a laminate biped robot for providing locomotion stabilization during jump gliding. The wings are designed to collapse down during the jumping phase to maximize jump height and deployed back for gliding phase using anisotropic buckling in tape spring hinges. The project aims to develop a reliable dynamics model which can be utilized for design and evaluation of optimized systems for jump-gliding. The aerodynamic simulations are run on a vortex-lattice code which provides numeric simulations of the defined geometric bodies. The aerodynamic simulations assist in improving the design parameters such as planform, camber and twist to achieve the best possible Coefficient of Lift for maximizing glide distance. The aerodynamic simulation output is then plugged into a dynamics model built in Python, which is validated and correlated with experimental testing of a key wing designs. The experimental results are then utilized to improve the dynamics model and obtain better designs for improved performance. The simulation model informs the aerodynamic design of wings for sustaining glide for the biped platform and maximizing glide length to increase range.

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Agent

Created

Date Created
2020