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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

The microstructure of drill steel

Pollard, Arthur L. January 1909 (has links) (PDF)
Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1909. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed March 24, 2009)
2

Cutting Tool Edge Design for Longer Tool Life

Banciu, Diana 08 1900 (has links)
In metal cutting, the effects of edge preparation and tool wear are considered most critical, as they directly determine tool life, surface finish and properties of the subsurface layer. Proper selection and application of cutting tool edge preparation is one of the basic factors for a successfully manufactured and correctly performing cutting tool. In this regard, the use of cutting tools with honed and chamfered edges is ever increasing. This thesis develops a procedure to design a subtle feature on the cutting edge of an insert, which mimics as closely as possible the natural wear that occurs in the initial stage of wear and arrive at a geometry that is known to lead to stable wear. In this case the geometry that would naturally occur is established with minimal subsurface damage, thus leading to a longer tool life. Turning test data collected showed that using a 50(mu)m chamfer on the rake face of the insert could minimize tool flank wear. By applying a special coating on this newly created geometry, a significant increase in the stable stage of wear and an overall improvement in performance and productivity have been observed. The analysis of chip morphology showed an improved behavior in the case of chamfered coated inserts. / Thesis / Master of Applied Science (MASc)
3

A Comparison of Depression Screening Tools in Parkinson’s Disease and Normal Community Controls Using a Brain and Body Donation Database

Rosen, Amanda 01 May 2012 (has links)
A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine. / The purpose of this study was to review and compare a variety of depression inventories in Parkinson’s disease (PD) and normal controls (NC) to look for patterns or trends to help with clinical management of these patients. The study population consisted of subjects enrolled in a brain and body donation program who were receiving annual neurological and neuropsychiatric assessments. Statistical models were applied to the data to compare trends between screening tools, medications, and demographics. The frequency of depression was greater in PD cases than NC across the inventories. The greatest frequency of positive screens came from the Neuropsychiatric Inventory (NPI). Because the NPI requires an informant to administer, and had the highest percent of positive screens in both PD and NC groups, this study suggests that a caregiver or partner may be a helpful addition in clinical practice during depression screening in elderly patients with and without PD.
4

Multisensor Fusion for Intelligent Tool Condition Monitoring (TCM) in End Milling Through Pattern Classification and Multiclass Machine Learning

Binsaeid, Sultan Hassan 17 December 2007 (has links)
In a fully automated manufacturing environment, instant detection of condition state of the cutting tool is essential to the improvement of productivity and cost effectiveness. In this paper, a tool condition monitoring system (TCM) via machine learning (ML) and machine ensemble (ME) approach was developed to investigate the effectiveness of multisensor fusion when machining 4340 steel with multi-layer coated and multi-flute carbide end mill cutter. Feature- and decision-level information fusion models utilizing assorted combinations of sensors were studied against selected ML algorithms and their majority vote ensemble to classify gradual and transient tool abnormalities. The criterion for selecting the best model does not only depend on classification accuracy but also on the simplicity of the implemented system where the number of features and sensors is kept to a minimum to enhance the efficiency of the online acquisition system. In this study, 135 different features were extracted from sensory signals of force, vibration, acoustic emission and spindle power in the time and frequency domain by using data acquisition and signal processing modules. Then, these features along with machining parameters were evaluated for significance by using different feature reduction techniques. Specifically, two feature extraction methods were investigated: independent component analysis (ICA), and principal component analysis (PCA) and two feature selection methods were studied, chi square and correlation-based feature selection (CFS). For various multi-sensor fusion models, an optimal feature subset is computed. Finally, ML algorithms using support vector machine (SVM), multilayer perceptron neural networks (MLP), radial basis function neural network (RBF) and their majority voting ensemble were studied for selected features to classify not only flank wear but also breakage and chipping. In this research, it has been found that utilizing the multisensor feature fusion technique under majority vote ensemble gives the highest classification performance. In addition, SVM outperformed other ML algorithms while CFS feature selection method surpassed other reduction techniques in improving classification performance and producing optimal feature sets for different models.
5

Design, Prototyping and Testing of a Tool for Intracardiac Delivery and Anchoring of a Prosthetic MitraI Valve

Marshall, Eli 25 April 2012 (has links)
The mitral valve in the heart sometimes struggles with diseases and complications, and needs to be replaced. This problem becomes more frequent with the ageing of the population in developed countries. The most common practice consists of suturing a prosthetic valve into place. However, newer methods are being devised and tested to make the surgery faster and less invasive. In particular, various types of new sutureless heart valve systems exist on the market. However, there is still a need for a tool designed for the intracardiac delivery and anchoring of a prosthetic mitral valve, as addressed here. A number of criteria and specifications were set by researchers at the Robarts Research Institute (London, ON) who came up with the design task. To address their request, ten conceptual designs of a sutureless, virtual-reality guided, self-anchoring, intracardiac system were developed to hold a prosthetic mitral valve, deliver it safely, and quickly affix it in position. The winning concept adequately met the design criteria. Two prototypes were manufactured. The attachment of a prosthetic valve to a simulated mitral valve annulus was tested with the first prototype to verify feasibility and measure leakage. The second prototype was pressure tested in a dynamic surgical phantom reproducing the circulatory conditions during surgery. While the preliminary feasibility of the concept was established, recommendations were made to develop a less bulky design.
6

Different coatings effect on tool-life when milling hardened tool steels

Jonsson, Jonathan January 2015 (has links)
Abstract This thesis work is about finding out which coating should be used for which hardened tool steel and this was done by testing different coated cutting tools in different kinds of tool steels. The thesis work is performed at Uddeholms AB together with Uddeholms AB in the department of R&D at machinability cooperating with eifeler-Vacotec GmbH. The thesis work is going on from the end of January to the start of June and is a part of the education as mechanical engineer at Karlstad University and includes a total of 22,5 hp. The objective after finished thesis work is to be able to leave a recommendation to Uddeholms AB which coating is most suitable for each tool steel. To be able to leave that recommendation cutting tests are performed in four different hardened steel grades from Uddeholms AB combined with seven different coatings from eifeler-Vacotec GmbH. Steel grades tested are NIMAX®, DIEVAR®, VANADIS® 10 and ORVAR® SUPREME and coatings tested are CROSAL®, EXXTRAL® and SISTRAL® in different compounds. ORVAR® SUPREME gave such a long cutting tool-life that it was left for further investigation due to time limits that the thesis work had. In the other three tool steels it was possible to get a recommendation out of the four coatings tested in each tool steel. The coating that is recommended for each tool steel is only based on the cutting tool lasting the longest in each tool steel. That is not how a recommendation usually is formed, however for this thesis work there is no time for checking all the aspects that is vital for a proper recommendation. In order to get a proper recommendation, further more aspects that are checked are for example: Different cutting parameters (cutting speed, feed, etc.) Different geometries on the cutting tool Smoothness of the cutting tool and the coating In table 1 there is a compilation of which coating that was recommended for which tool steel. Table 1. This is a compilation of which coating that was recommended for which tool steel. NIMAX®               CROSAL® V1 DIEVAR®             SISTRAL® Ultrafine VANADIS® 10    SISTRAL® S
7

Design, Prototyping and Testing of a Tool for Intracardiac Delivery and Anchoring of a Prosthetic MitraI Valve

Marshall, Eli 25 April 2012 (has links)
The mitral valve in the heart sometimes struggles with diseases and complications, and needs to be replaced. This problem becomes more frequent with the ageing of the population in developed countries. The most common practice consists of suturing a prosthetic valve into place. However, newer methods are being devised and tested to make the surgery faster and less invasive. In particular, various types of new sutureless heart valve systems exist on the market. However, there is still a need for a tool designed for the intracardiac delivery and anchoring of a prosthetic mitral valve, as addressed here. A number of criteria and specifications were set by researchers at the Robarts Research Institute (London, ON) who came up with the design task. To address their request, ten conceptual designs of a sutureless, virtual-reality guided, self-anchoring, intracardiac system were developed to hold a prosthetic mitral valve, deliver it safely, and quickly affix it in position. The winning concept adequately met the design criteria. Two prototypes were manufactured. The attachment of a prosthetic valve to a simulated mitral valve annulus was tested with the first prototype to verify feasibility and measure leakage. The second prototype was pressure tested in a dynamic surgical phantom reproducing the circulatory conditions during surgery. While the preliminary feasibility of the concept was established, recommendations were made to develop a less bulky design.
8

Technology, choice, and competitiveness the case of the machine tool industries in the U.S. and Japan /

Yang, Heeseung. January 1988 (has links)
Thesis (Ph. D.)--George Washington University, 1988. / Includes bibliographical references (leaves 280-295).
9

Design, Prototyping and Testing of a Tool for Intracardiac Delivery and Anchoring of a Prosthetic MitraI Valve

Marshall, Eli January 2012 (has links)
The mitral valve in the heart sometimes struggles with diseases and complications, and needs to be replaced. This problem becomes more frequent with the ageing of the population in developed countries. The most common practice consists of suturing a prosthetic valve into place. However, newer methods are being devised and tested to make the surgery faster and less invasive. In particular, various types of new sutureless heart valve systems exist on the market. However, there is still a need for a tool designed for the intracardiac delivery and anchoring of a prosthetic mitral valve, as addressed here. A number of criteria and specifications were set by researchers at the Robarts Research Institute (London, ON) who came up with the design task. To address their request, ten conceptual designs of a sutureless, virtual-reality guided, self-anchoring, intracardiac system were developed to hold a prosthetic mitral valve, deliver it safely, and quickly affix it in position. The winning concept adequately met the design criteria. Two prototypes were manufactured. The attachment of a prosthetic valve to a simulated mitral valve annulus was tested with the first prototype to verify feasibility and measure leakage. The second prototype was pressure tested in a dynamic surgical phantom reproducing the circulatory conditions during surgery. While the preliminary feasibility of the concept was established, recommendations were made to develop a less bulky design.
10

ANALYSIS OF DIFFERENT TI5553 ALLOY CUTTING STRATEGIES FOR THE IMPROVEMENT OF TOOL LIFE

Kock Filho, Tarcisio January 2021 (has links)
Titanium alloys support a wide range of practical applications due to their excellent mechanical properties. These include high strength-to-weight ratio, high mechanical strength at elevated temperatures and remarkable oxidation resistance. Machinability investigations so far have been intentionally focused on Ti-6Al-4V, which is commonly used in the aerospace research and development. However, a new classes of titanium alloys are also being developed for these applications. Ti-5Al-5Mo-5V-3C, also known as Ti5553, is included in this new category of titanium grade alloys. It corresponds to a near beta titanium alloy and generally it is employed on the production of high strength parts. Its high tensile strength combined with low weight (compared to Ti64) makes Ti5553 a suitable choice for landing gear parts and advanced structural components. However, due to the previously mentioned mechanical properties of Ti5553, machining processes can be difficult. During the cutting tests, the cutting zone experiences high cutting temperatures, and combined with a low rate of heat transfer, it generates stress and premature tool failure. By using several distinct experimental approaches, this work presents a comparison between different machining conditions (combinations of tools and coolants) to diagnose wear processes and identify better cutting parameters. The main objective of this research is to establish an understanding of how these parameters affect tribological aspects when machining Ti5553. The results of machining studies demonstrate different wear behaviour for CBN and PCD tools under various cutting environments (different coolant modes). These operating conditions can considerably affect the cutting forces leading to an increased tool life and improved surface integrity by decreasing, the residual stress and roughness, as well as work of hardening the workpiece during machining operations. / Thesis / Master of Applied Science (MASc)

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