DOCSLIB.ORG

Process and Tool Design for the High Integrity Die Casting of Aluminum And

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Process and Tool Design for the High Integrity Die Casting of Aluminum And Process and Tool Design for the High Integrity Die Casting of Aluminum and Magnesium Alloys THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Varun Nandakumar Graduate Program in Industrial and Systems Engineering The Ohio State University 2014 Master's Examination Committee: Dr. Jerald Brevick, Advisor Dr. Alan Luo Copyright by Varun Nandakumar 2014 Abstract The push for higher efficiency and lower emissions on present day automobiles have created a greater need for light alloys such as Aluminum and Magnesium to replace the customary steel parts in an automobile. A lot of these replaced parts are in structural load bearing components on a vehicle. This usually meant that processes such as the traditional High Pressure Die Casting would not be able to claim a stake in it due to its innate air and Hydrogen entrapment issues. But, with an overall higher maintenance of quality in the traditional process, it is possible to create higher integrity parts that are usable in structural applications. This thesis describes and tests some methods to improve the traditional High Pressure Die Casting process to enable it to produce higher integrity casts for Aluminum and Magnesium alloys. Methods to achieve a higher quality melt are researched and a rotary degasser is used for two experimental trials of similar Aluminum alloys. Similarly, methods to integrate vacuum into the existing setup are studied and the tooling part of the vacuum assist system with chill blocks is fully designed. The design of the chill blocks is carried out from the ground up using MAGMA and ANSYS simulation tools which were available at the Integrated Systems Engineering Lab. A designed experiment is completed to understand the effects of changing parameters on the design. Finally, the optimum design is completed on 3D CAD software and then manufactured in house. ii To Charuchechi iii Acknowledgments To Dr. Brevick - my advisor, the best teacher I’ve had and possibly the most patient man I will ever meet. I can’t even begin to describe how much I’ve enjoyed working under you. I have never come out of a discussion – be it in the hallway, on a drive or at your office, without learning something new. You have a knack of making any topic interesting and I’m going to miss popping into your room with the silliest question knowing that you will do your best to break it down for me. Thank you sir for everything. To Martin Doyle from Gibbs Die Casting at Henderson, KY- Thank you for helping us understand vacuum die casting, giving us a tour of your facility and graciously providing us with tool bits to make the sealant cut outs. To Charuchechi - Without your generosity I wouldn’t be here. Thank you for a second chance at life. To My Parents – It is a tremendous joy knowing that the two of you are constantly behind me. Thank you for always being there. To Deepta – Thanks for all the encouragement, the talks and help when I thought I couldn’t make it. To my Sister, friends and so many others who are in one way or the other responsible for my success, I am deeply humbled by all of your kindness. Last but by no means least, to my colleague William Tullos - I’ve had a great time working with you the past year and a half, thank you for always responding to my email within minutes of receiving them and your constant backing. iv Vita March 19, 1987 ..............................................Born – Bangalore, India 2008 ...............................................................B.E. Mechanical Engineering, Visvesvaraya Technological University Fall 2010 to present .......................................M.S. Industrial and Systems Engineering, The Ohio State University May 2013 to present ......................................Graduate Research Associate, Department of Industrial and Systems Engineering, The Ohio State University Fields of Study Major Field: Industrial and Systems Engineering v Table of Contents Abstract ............................................................................................................................... ii Acknowledgments.............................................................................................................. iv Vita ...................................................................................................................................... v Table of Contents ............................................................................................................... vi List of Tables ..................................................................................................................... xi List of Figures ................................................................................................................... xii Chapter 1: Introduction ....................................................................................................... 1 The High Pressure Die Casting Process .......................................................................... 1 Advantages and Limitations ............................................................................................ 4 Types of High Pressure Die Casting ............................................................................... 5 The Cold Chamber Process ......................................................................................... 6 The Hot Chamber Process ........................................................................................... 7 High Integrity Processes.................................................................................................. 8 Applications of High Pressure Die Casting .................................................................... 9 Automotive Applications ........................................................................................... 10 Structural Automotive Applications .......................................................................... 13 vi Light alloys used in Structural Die Casting .................................................................. 14 Aluminum alloys ....................................................................................................... 14 Magnesium alloys ...................................................................................................... 15 Process consideration for structural alloys in the automotive industry ......................... 16 Research Summary ........................................................................................................ 17 Objectives .................................................................................................................. 18 Approach ................................................................................................................... 18 Chapter 2: Dealing with porosity problems in HPDC .................................................. 20 Gas Porosity .................................................................................................................. 21 Hydrogen ................................................................................................................... 21 Air Entrapment .......................................................................................................... 21 Oil or water from Lubrication spray .......................................................................... 21 Solidification shrinkage................................................................................................. 22 Porosity reduction and obtaining a high integrity cast .................................................. 22 Melt quality Improvements ........................................................................................... 23 Degassing ...................................................................................................................... 23 Passive Degassing...................................................................................................... 24 Liquid argon shield .................................................................................................... 25 Gaseous argon shield ................................................................................................. 25 vii Chemical tablets ........................................................................................................ 26 Rotary Impeller Degassing ........................................................................................ 27 Flux Induced Rotary degassing ................................................................................. 28 Choosing a Purge Gas................................................................................................ 29 Additional and often overlooked Benefit of Degassing ............................................ 30 Reduced Pressure Test ............................................................................................... 30 Improved process control .............................................................................................. 31 Metallurgical Modification ........................................................................................... 33 Vacuum Die Casting ..................................................................................................... 34 Advantages of Vacuum Die Casting ......................................................................... 37 Vacural Process ........................................................................................................
Load more

Recommended publications
  • Troubleshooting Decorative Electroplating Installations, Part 5
    Troubleshooting Decorative Electroplating Installations, Part 5: Plating Problems Caused Article By Heat & Bath Temperature Fluctuations by N.V. Mandich, CEF, AESF Fellow Technical Technical In previous parts of this series, emphasis was given The fast-machining steels must then be carburized to troubleshooting of the sequences for pre-plating or case-hardened to obtain a surface with the hardness and electroplating over metals, Parts 1 and 2;1 required to support the top chromium electroplate. the causes, symptoms and troubleshooting for Case hardening is the generic term covering several pores, pits, stains, blistering and “spotting-out” processes applicable to steel or ferrous alloys. It changes phenomena, Part 3;2 and troubleshooting plating on the surface composition of the top layer, or case, by plastic systems, Part 4.3 Here in Part 5, causes and adsorption of carbon, nitrogen or a mixture of the two. some typical examples of problems that occur in By diffusion, a concentration gradient is created. The electroplating as a result of a) thermal, mechanical heat-treatments and the composition of the steel are surface treatments, b) the metallurgy of the part to additional variables that should be addressed and taken be plated or c) effects of plating bath temperature into account in the electroplating procedure. on plating variables and quality of the deposits When discussing the effect of heat-treatment on are discussed. subsequent electroplating processes it is necessary to zero in on the type of heat-treatment involved. We Nearly every plater has at one time or another had the can defi ne the heat-treatment process as changing the experience of trying to plate parts that simply would characteristics of the parts by heating above a certain not plate.
    [Show full text]
  • Electroforming of Copper Canisters
    Mineralogical Magazine, November 2015, Vol. 79(6), pp. 1521–1528 OPEN ACCESS Manufacturing technology for implementing geological disposal: electroforming of copper canisters 1,2,3,* 1,3 1,4 2 2 T. H ERNANDEZ-SELVA ,D.L.ENGELBERG ,F.SCENINI ,D.FOX AND A. MCCLUSKY 1 Materials Performance Centre, School of Materials, The University of Manchester, Manchester M13 9PL, UK 2 BEP Surface Technologies Ltd, Eton Hill Road, Radcliffe, Manchester M26 2XT, UK 3 Research Centre for Radwaste and Decommissioning, The University of Manchester, Manchester M13 9PL, UK 4 Nuclear Advanced Manufacturing Centre, The University of Manchester, Manchester M13 9PL, UK ABSTRACT The existing capability and current development needs for implementing electroforming as a viable manufacturing process to produce copper cylinders with dimensions comparable to the Swedish KBS-3 design are discussed. Large freestanding copper cylinders can be produced readily, but there is a need to address challenges associated with controlling the electro-deposition process to conform to compositional and mechanical requirements of the copper layers produced. The methodology to optimize the manufacturing process, based on a study of key parameters, such as the effects of electrolyte additives on grain size and the chemical composition of electroformed layers, is described here. Possible ways to introduce a robust manufacturing route are also presented. K EYWORDS: nuclear wastes, deep geological repository, KBS-3 copper canister, electroforming, electroplating. Introduction Institute, 2006; ARAO, 2009), whereas the Nuclear Waste Management Organization (NWMO) of THE concept for the UK’s inventory of high-level Canada is focusing its research on thick-walled radioactive waste (HLW) is to implement deep steel containers coated with 3 mm of electroplated geological disposal (Department of Energy & copper (Keech et al., 2014).
    [Show full text]
  • Enhanced Fracture Strength in the Working Layer of Rolls Manufactured in Ni-Hard Cast Iron Alloyed with Mo, Nb and Mg
    metals Article Enhanced Fracture Strength in the Working Layer of Rolls Manufactured in Ni-Hard Cast Iron Alloyed with Mo, Nb and Mg Alberto Cofiño-Villar 1, Jose Florentino Alvarez-Antolin 1,* and Juan Asensio-Lozano 2 1 Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica, Edificio departamental Este, Universidad de Oviedo C/ Wifredo Ricart s/n-, 33204 Gijón (Asturias), Spain; [email protected] 2 Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica, Escuela de Ingeniería de Minas, Energía y Materiales, Universidad de Oviedo, C/ Independencia 13, 33004 Oviedo (Asturias), Spain; [email protected] * Correspondence: alvarezfl[email protected]; Tel.: +34-985-181-949 Received: 28 August 2018; Accepted: 13 September 2018; Published: 15 September 2018 Abstract: One of the main in-service failure mechanisms of the work-rolls used in hot strip mill finishing stands is surface spalling. The indefinite chill double-poured rolls usually comprise of a peripheral working layer made of crushed Ni-hard cast iron and a grey cast iron core, mostly pearlitic matrix with spheroidal graphite. To enhance its wear resistance, the working layer can be alloyed with Mo and Nb. The possible cracking and spalling of the surfaces of these work-rolls is strongly influenced by the presence of carbides and the continuity of their network. The flexural and impact toughness tests are reliable testing methods to assess these properties. The aim of this paper is to identify those manufacturing factors that have a significant effect on the flexural strength and toughness of this material, correlating the results with the volume fraction of precipitated carbides.
    [Show full text]
  • Ring-Bending Machines
    THE CHRONICLE OF THE COMPANY 1965 Foundation of the company as an one-man-business, trading of gates, metal doors and door frames, window bars and grills. Glaser headquarter is still at Kleestadt, near Groß-Umstadt. First exhibitions in Erbach, Groß-Umstadt and Frankfurt. 1971 Company moves to Groß-Umstadt; building of the first storage- and production hall "Am Brüchelsteg" Extension of the production line: windows, doors, benches and fences made out of plastic, wrought iron works and wrought-iron machines. Automatic Machines 1976 Achieving of the Master Craftsman's Diploma of the Handwerkskammer Darmstadt. 1977 Opening up the second production hall. Extension of teh production line for wrought-iron articles 1982 For the first time GLASER is represented at the International Handwerkermesse München and the Hannover Fair. First pioneering success, mostly in the construction of machinery 1986 Buildingof the fourth factory hall for the production of machines and tools. Achieving the license to train in wrought-iron crafts and constructing of tools and machines. Export business is extended. Attachments for GDM 1990 Demolition of the first factory hall and putting up the new exhibition and administration building. GLASER's 25th anniversary on 8th December 1990 1992 Opening up a new establishment at Bamberg (Bavaria) of 2.000 square meters for the production of wrought-iron articles. 1995 Erection of the fifth hall of 3.000 m² with the most modern bending centre and facilities for stainless Automatic Scroll Benders Scroll steel- and CAD trainings as well as production of machinery and tools. 1997 Wining award »Staatspreis der Bayerischen Staatsregierung« and the »Bundespreis für hervorragende innovative Leistungen für das Handwerk« .
    [Show full text]
  • ZEP LUBEZE DRILL CHILL™ Cutting Oil
    PROD. #1378 205 PRODUCT SPECIFICATION REPORT ZEP LUBEZE DRILL CHILL™ Cutting Oil DESCRIPTION A fatty, mineral oil based, ready to use metalworking fluid, fortified with extremely pressure additives. FEATURES BENEFITS • Versatile • Can be used on carbon, allot, and stainless steel as well as softer metals such as aluminum. • Anti weld • Helps prevent chips from welding to tool surface • Prolongs tool life • Reduces friction, increases cutting speeds • Inhibits rust • Leaves behind a light oil film which provides temporary protection to the work piece and tool surface • Conserves energy • Lowers resistance to cutting resulting in lower torque and power requirements APPLICATIONS An excellent lubricating fluid for metalworking applications, particularly in extreme pressure situations such as drilling and threading. Used in any metalworking and fabricating facility. COMPANION PRODUCTS Zep Gator Tails, Zep degreasers, Zep Cold Galvanized, Zep Super Penetrant, Zep Ironclad, Zep PLS, Zep Viton Gloves SPECIFICATIONS Physical form . .Thin, amber oil Boiling point . .545 - 884°F Flash point (TCC) . .300°F Shelf life . .1 year minimum Odor . .solvent odor DOT Shipping label . .LUBRICANTS, METAL CUTTING, pH . .N/A . .LIQUID, NOI Specific gravity . .0.88 PACKAGING 5 gallon pail 55 gallon drum ZEP MANUFACTURING COMPANY 1-877-I BUY ZEP Your One Source for Cleaning and Maintenance Products (1-877-428-9937) PROD. #1378 205 PRODUCT LABEL ZEP LUBEZE DRILL CHILL™ Cutting Oil ™ PROD.# 1378 LUBEZE DRILL CHILL 501B CUTTING OIL •Drilling •Cutting •Boring •Thread Cutting and Machining Operations A premium cutting oil fortified with sulfur and chlorine compounds for FIRST AID: effectiveness in extreme pressure applications. Provides excellent lubricity. EYES: Immediately flush eyes with plenty of water for at least 15 minutes, occasionally Reduces energy requirements by lowering resistance to cutting tool.
    [Show full text]
  • From the on Inal Document. What Can I Write About?
    DOCUMENT RESUME ED 470 655 CS 511 615 TITLE What Can I Write about? 7,000 Topics for High School Students. Second Edition, Revised and Updated. INSTITUTION National Council of Teachers of English, Urbana, IL. ISBN ISBN-0-8141-5654-1 PUB DATE 2002-00-00 NOTE 153p.; Based on the original edition by David Powell (ED 204 814). AVAILABLE FROM National Council of Teachers of English, 1111 W. Kenyon Road, Urbana, IL 61801-1096 (Stock no. 56541-1659: $17.95, members; $23.95, nonmembers). Tel: 800-369-6283 (Toll Free); Web site: http://www.ncte.org. PUB TYPE Books (010) Guides Classroom Learner (051) Guides Classroom Teacher (052) EDRS PRICE EDRS Price MF01/PC07 Plus Postage. DESCRIPTORS High Schools; *Writing (Composition); Writing Assignments; *Writing Instruction; *Writing Strategies IDENTIFIERS Genre Approach; *Writing Topics ABSTRACT Substantially updated for today's world, this second edition offers chapters on 12 different categories of writing, each of which is briefly introduced with a definition, notes on appropriate writing strategies, and suggestions for using the book to locate topics. Types of writing covered include description, comparison/contrast, process, narrative, classification/division, cause-and-effect writing, exposition, argumentation, definition, research-and-report writing, creative writing, and critical writing. Ideas in the book range from the profound to the everyday to the topical--e.g., describe a terrible beauty; write a narrative about the ultimate eccentric; classify kinds of body alterations. With hundreds of new topics, the book is intended to be a resource for teachers and students alike. (NKA) Reproductions supplied by EDRS are the best that can be made from the on inal document.
    [Show full text]
  • Study Unit Toolholding Systems You’Ve Studied the Process of Machining and the Various Types of Machine Tools That Are Used in Manufacturing
    Study Unit Toolholding Systems You’ve studied the process of machining and the various types of machine tools that are used in manufacturing. In this unit, you’ll take a closer look at the interface between the machine tools and the work piece: the toolholder and cutting tool. In today’s modern manufacturing environ ment, many sophisti- Preview Preview cated machine tools are available, including manual control and computer numerical control, or CNC, machines with spe- cial accessories to aid high-speed machining. Many of these new machine tools are very expensive and have the ability to machine quickly and precisely. However, if a careless deci- sion is made regarding a cutting tool and its toolholder, poor product quality will result no matter how sophisticated the machine. In this unit, you’ll learn some of the fundamental characteristics that most toolholders have in common, and what information is needed to select the proper toolholder. When you complete this study unit, you’ll be able to • Understand the fundamental characteristics of toolhold- ers used in various machine tools • Describe how a toolholder affects the quality of the machining operation • Interpret national standards for tool and toolholder iden- tification systems • Recognize the differences in toolholder tapers and the proper applications for each type of taper • Explain the effects of toolholder concentricity and imbalance • Access information from manufacturers about toolholder selection Remember to regularly check “My Courses” on your student homepage. Your instructor
    [Show full text]
  • Foundry Industry SOQ
    STATEMENT OF QUALIFICATIONS Foundry Industry SOQ TRCcompanies.com Foundry Industry SOQ About TRC The world is advancing. We’re advancing how it gets planned and engineered. TRC is a global consulting firm providing environmentally advanced and technology‐powered solutions for industry and government. From solid waste, pipelines to power plants, roadways to reservoirs, schoolyards to security solutions, clients look to TRC for breakthrough thinking backed by the innovative follow‐ through of a 50‐year industry leader. The demands and challenges in industry and government are growing every day. TRC is your partner in providing breakthrough solutions that navigate the evolving market and regulatory environment, while providing dependable, safe service to our customers. We provide end‐to‐end solutions for environmental management. Throughout the decades, the company has been a leader in setting industry standards and establishing innovative program models. TRC was the first company to conduct a major indoor air study related to outdoor air quality standards. We also developed innovative measurements standards for fugitive emissions and ventilation standards for schools and hospitals in the 1960s; managed the monitoring program and sampled for pollutants at EPA’s Love Canal Project in the 1970s; developed the basis for many EPA air and hazardous waste regulations in the 1980s; pioneered guaranteed fixed‐price remediation in the 1990s; and earned an ENERGY STAR Partner of the Year Award for outstanding energy efficiency program services provided to the New York State Energy Research and Development Authority in the 2000s. We are proud to have developed scientific and engineering methodologies that are used in the environmental business today—helping to balance environmental challenges with economic growth.
    [Show full text]
  • Semi-Solid Slurry Formation Via Liquid Metal
    SEMI-SOLID SLURRY FORMATION VIA LIQUID METAL MIXING A Thesis Submitted to the Faculty of the WORCESTER POLYTECHNIC INSTITUTE in partial fulfillment of the requirements for the Degree of Master of Science in Materials Science and Engineering July 2003 by Matthew M. Findon ________________________________________ APPROVED: Diran Apelian, Howmet Professor of Engineering, Advisor Richard D. Sisson, Jr., Professor of Mechanical Engineering, Materials Science and Engineering Program Head ii Abstract New, economical semi-solid metal (SSM) processes rely on forced convection during solidification to influence non-dendritic growth. The fundamental mechanisms that produce SSM microstructures in the presence of forced convection (due to fluid flow) are not fully understood. The objective of this work is to elucidate these mechanisms through the use of a new semi-solid slurry-making technique. Employing an apparatus developed at WPI, two alloy melts are mixed within a static reactor that induces convection and rapid cooling. Experiments carried out with this apparatus, named the “Continuous Rheoconversion Process” (CRP), result in globular semi-solid microstructures throughout a wide range of processing conditions. These conditions include the superheat in the melts before mixing, cooling rate of the slurry through the SSM range, and the presence or absence of inoculants in the melts. The results comprise repeatable sets of semi-solid microstructures having fine particle size and shape factors approaching unity. Even in the absence of melt inoculants, uniform distributions of α-Al particle sizes of about 60µm are attainable. Entrapped liquid is not present in the majority of the samples obtained with the CRP, and irregular particles that form in the process are of a limited distribution.
    [Show full text]
  • High Integrity Die Casting Processes
    HIGH INTEGRITY DIE CASTING PROCESSES EDWARD J. VINARCIK JOHN WILEY & SONS, INC. This book is printed on acid-free paper. ࠗϱ Copyright ᭧ 2003 by John Wiley & Sons, New York. All rights reserved Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, e-mail: [email protected]. Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, in- cidental, consequential, or other damages.
    [Show full text]
  • Metal Casting Terms and Definitions
    Metal Casting Terms and Definitions Table of Contents A .................................................................................................................................................................... 2 B .................................................................................................................................................................... 2 C .................................................................................................................................................................... 2 D .................................................................................................................................................................... 4 E .................................................................................................................................................................... 5 F ..................................................................................................................................................................... 5 G .................................................................................................................................................................... 5 H .................................................................................................................................................................... 6 I ....................................................................................................................................................................
    [Show full text]
  • Performance Evaluation of Different Materials As Chills in Sand Casting of Aluminium Alloy
    PERFORMANCE EVALUATION OF DIFFERENT MATERIALS AS CHILLS IN SAND CASTING OF ALUMINIUM ALLOY BY KABIRU MUFTAU RAJI M.Sc/ENG/ 08222/2010-2011 A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY ZARIA, KADUNA STATE, NIGERIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF A MASTER DEGREE IN MECHANICAL ENGINEERING DEPARTMENT OF MECHANICAL ENGINEERING, FACULTY OF ENGINEERING AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA. FEBRUARY, 2016 i DECLARATION I declare that the work in this Dissertation entitled Performance Evaluation of Different Metallic Materials as Chills in Sand Casting of Aluminium Alloy has been carried out by me in the Department of Mechanical Engineering, Ahmadu Bello University, Zaria. The information derived from the literature has been duly acknowledged in the text and a list of references provided. No part of this thesis was previously presented for another degree or diploma at this or any other institution. Kabiru Muftau Raji ……..………………… ……...……………. Name of Student Signature Date ii CERTIFICATION This dessertation entitled Performance Evaluation of Different Materials as Chills in Sand Casting of Aluminium Alloy by Kabiru Muftau RAJI meets the regulations governing the award of the degree of Master in Mechanical Engineering of the Ahmadu Bello University, and is approved for its contribution to knowledge and literacy presentation. Dr. D.S. Yawas ……………………. ………………… Chairman, Supervisory Committee Signature Date Prof. A. I. Obi …………………… ………………… Member, Supervisory Committee Signature Date Dr. M. I. Dauda ……………………. ………………... Head of Department Signature Date Prof. kabir Bala …………………… ………………… Dean, School of Postgraduate Studies Signature Date iii DEDICATION This dissertation is dedicated to the Almighty GOD, the Most Beneficent and the Most Merciful.
    [Show full text]