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Author: Thomas Hannah
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The goal of this work is twofold. One part is to develop both the experimental techniques and advanced finite element modeling techniques necessary for understanding and analyzing data collected using a miniature 3.16 mm diameter Kolsky bar or Split Hopkinson Pressure Bar for high rate experimentation. Additionally, a robust analysis technique to gather statistically significant data is developed to simplify the experimental data gathering process and ensure the significance of the results. The work focuses mainly of the development of the Kolsky equipment and techniques, as well as methods for identifying error sources during testing. Additionally, models of the SHPB system have been generated using the finite element code Abaqus®, and are used throughout the project to aid in system characterization and experimental design efforts. Special attention is paid to the differences between miniature systems and full size ones, especially where data collection rates and sampling frequency are concerned. The use and characterization of paper pulse shapers is also developed to aid in the testing of UHMWPE samples at rates in excess of 10^4 strain per second. The second aspect of this work is to apply these techniques to the characterization of Dyneema® which is a composite consisting of Ultra High Molecular Weight Polyethylene (UHMWPE) fibers set in a polymer matrix, in this case HB26 hard laminate. Additionally, this work entails the design and implementation of full scale high speed impact tests using UHMWPE targets in multiple configurations to examine the variation in response due to a change in initial conditions and to evaluate the change in damage mechanisms. Finally, high resolution Computer Tomography or CT scans are used to evaluate the damage mechanisms observed in both the Kolsky bar testing and the plate impact testing nondestructively and without otherwise effecting the failure surfaces and structures. Mechanisms displayed in the Kolsky experiments are then compared to those observed in the plate impact tests to determine if and where the type of data collected from Kolsky bar tests can be applied to any future modeling efforts of the composite. Three fundamental knowledge gaps to be addressed in this work are: 1) Can a newer generation of "miniature" Kolsky bars generate repeatable and reproducible data? 2) How does Dyneema® respond differently increasing the strain rate from 10^3 strain per second to 10^4 strain per second? 3) Are there similar damage mechanisms seen in small scale Kolsky tests and large scale impact tests, and where could the Kolsky bar data be applied to future modeling efforts?
Author: Thomas Hannah
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The goal of this work is twofold. One part is to develop both the experimental techniques and advanced finite element modeling techniques necessary for understanding and analyzing data collected using a miniature 3.16 mm diameter Kolsky bar or Split Hopkinson Pressure Bar for high rate experimentation. Additionally, a robust analysis technique to gather statistically significant data is developed to simplify the experimental data gathering process and ensure the significance of the results. The work focuses mainly of the development of the Kolsky equipment and techniques, as well as methods for identifying error sources during testing. Additionally, models of the SHPB system have been generated using the finite element code Abaqus®, and are used throughout the project to aid in system characterization and experimental design efforts. Special attention is paid to the differences between miniature systems and full size ones, especially where data collection rates and sampling frequency are concerned. The use and characterization of paper pulse shapers is also developed to aid in the testing of UHMWPE samples at rates in excess of 10^4 strain per second. The second aspect of this work is to apply these techniques to the characterization of Dyneema® which is a composite consisting of Ultra High Molecular Weight Polyethylene (UHMWPE) fibers set in a polymer matrix, in this case HB26 hard laminate. Additionally, this work entails the design and implementation of full scale high speed impact tests using UHMWPE targets in multiple configurations to examine the variation in response due to a change in initial conditions and to evaluate the change in damage mechanisms. Finally, high resolution Computer Tomography or CT scans are used to evaluate the damage mechanisms observed in both the Kolsky bar testing and the plate impact testing nondestructively and without otherwise effecting the failure surfaces and structures. Mechanisms displayed in the Kolsky experiments are then compared to those observed in the plate impact tests to determine if and where the type of data collected from Kolsky bar tests can be applied to any future modeling efforts of the composite. Three fundamental knowledge gaps to be addressed in this work are: 1) Can a newer generation of "miniature" Kolsky bars generate repeatable and reproducible data? 2) How does Dyneema® respond differently increasing the strain rate from 10^3 strain per second to 10^4 strain per second? 3) Are there similar damage mechanisms seen in small scale Kolsky tests and large scale impact tests, and where could the Kolsky bar data be applied to future modeling efforts?
Author: Ray A. Gsell
Publisher: ASTM International
ISBN: 0803124821
Category : Creep
Languages : en
Pages : 139
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Book Description
Proceedings of a November 1996 symposium held in New Orleans, Louisiana, providing a forum for presentations and discussions of issues critical to the understanding of ultra-high molecular weight polyethylene (UHMWPE) as used in medical and surgical devices. Eleven papers are grouped in three sectio
Author: Kesavan Ravi
Publisher:
ISBN:
Category :
Languages : en
Pages : 198
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Book Description
Recent developments showed polymer coatings to be feasible by cold spray (CS) technique on different surfaces. This is especially important for Ultra-High Molecular Weight Polyethylene (UHMWPE) which cannot be classically processed. But the mechanisms behind coating formation was not largely understood. The thesis presents a mechanistic understanding of high strain rate impact behavior of Ultra-High Molecular Weight Polyethylene and the mechanism of coating formation during CS. The coating formation is first broken down into two major categories: 1. Interaction of UHMWPE with Al substrate (impacting particle-substrate interaction) during a high-speed impact and interaction of UHMWPE with already deposited UHMWPE particles (impacting particle-deposited particles) leading to a buildup in the coating. First stage of coating formation was understood from a technique developed for this work called Isolated Particle Deposition (IPD). In the experimental IPD process, effects of gas temperature and FNA content were calibrated empirically by depositing UHMWPE particles in an isolated manner on an Al substrate. The Deposition efficiency increased with gas temperature and FNA content. The use of an ultrafast video-camera helped to determine the particle velocity, and theoretical calculations helped to evaluate the temperature of UHMWPE particles before and during the impact process. Mechanical response of UHMWPE at different temperatures were understood by calculating elastic strain energy of UHMWPE which decreased with increasing material temperature and increased with the strain rate. Rebound of UHMWPE particles on Al surface depended upon whether UHMWPE particles after impact furnished a contact area with an interfacial bond stronger than elastic strain energy of the particle. External contributions like H-bonds on the FNA surface provide sufficiently strong extra bonds at the contact surface to increase the window of deposition at higher temperatures, which was otherwise very low. Second stage of coating formation was understood from the mechanism of welding of UHMWPE grains at different interfacial loading conditions and at varying FNA contents. The morphological and mechanical characterization showed that when UHMWPE was processed under high loading conditions (using classical sintering technique), FNA particles reinforced the UHMWPE interface. On the contrary, when UHMWPE was processed under low loading conditions, FNA particles weakened the interface. Last to be discussed in the thesis is the strain rate effect of UHMWPE using Split-Hopkinson Pressure Bar (SHPB) experiments, in order to approach comparable conditions to what happens during particle impacts. This part of the study discussed in detail the effects a high strain-rate compression has on UHMWPE by analyzing its stress-strain curves, with and without FNA. Thus, the mechanical response data with the inclusion 0%, 4% and 10% FNA to UHMWPE is also presented and discussed.
Author: Weinong W. Chen
Publisher: Springer Science & Business Media
ISBN: 1441979824
Category : Technology & Engineering
Languages : en
Pages : 388
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Book Description
The authors systematically describe the general principles of Kolsky bars, or split Hopkinson bars, which are widely used for obtaining dynamic material properties. Modifications are introduced for obtaining reliable data. Specific experiment design guidelines are provided to subject the specimen to desired testing conditions. Detailed Kolsky-bar examples are given for different classes of materials (brittle, ductile, soft, etc) and for different loading conditions (tension, torsion, triaxial, high/low temperatures, intermediate strain rate, etc). The Kolsky bars used for dynamic structural characterization are briefly introduced. A collection of dynamic properties of various materials under various testing conditions is included which may serve as a reference database. This book assists both beginners and experienced professionals in characterizing high-rate material response with high quality and consistency. Readers who may benefit from this work include university students, instructors, R & D professionals, and scholars/engineers in solid mechanics, aerospace, civil and mechanical engineering, as well as materials science and engineering.
Author: Jorgen S Bergstrom
Publisher: William Andrew
ISBN: 0323322964
Category : Technology & Engineering
Languages : en
Pages : 520
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Book Description
Very few polymer mechanics problems are solved with only pen and paper today, and virtually all academic research and industrial work relies heavily on finite element simulations and specialized computer software. Introducing and demonstrating the utility of computational tools and simulations, Mechanics of Solid Polymers provides a modern view of how solid polymers behave, how they can be experimentally characterized, and how to predict their behavior in different load environments. Reflecting the significant progress made in the understanding of polymer behaviour over the last two decades, this book will discuss recent developments and compare them to classical theories. The book shows how best to make use of commercially available finite element software to solve polymer mechanics problems, introducing readers to the current state of the art in predicting failure using a combination of experiment and computational techniques. Case studies and example Matlab code are also included. As industry and academia are increasingly reliant on advanced computational mechanics software to implement sophisticated constitutive models – and authoritative information is hard to find in one place - this book provides engineers with what they need to know to make best use of the technology available. Helps professionals deploy the latest experimental polymer testing methods to assess suitability for applications Discusses material models for different polymer types Shows how to best make use of available finite element software to model polymer behaviour, and includes case studies and example code to help engineers and researchers apply it to their work
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309212855
Category : Technology & Engineering
Languages : en
Pages : 176
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Book Description
Armor plays a significant role in the protection of warriors. During the course of history, the introduction of new materials and improvements in the materials already used to construct armor has led to better protection and a reduction in the weight of the armor. But even with such advances in materials, the weight of the armor required to manage threats of ever-increasing destructive capability presents a huge challenge. Opportunities in Protection Materials Science and Technology for Future Army Applications explores the current theoretical and experimental understanding of the key issues surrounding protection materials, identifies the major challenges and technical gaps for developing the future generation of lightweight protection materials, and recommends a path forward for their development. It examines multiscale shockwave energy transfer mechanisms and experimental approaches for their characterization over short timescales, as well as multiscale modeling techniques to predict mechanisms for dissipating energy. The report also considers exemplary threats and design philosophy for the three key applications of armor systems: (1) personnel protection, including body armor and helmets, (2) vehicle armor, and (3) transparent armor. Opportunities in Protection Materials Science and Technology for Future Army Applications recommends that the Department of Defense (DoD) establish a defense initiative for protection materials by design (PMD), with associated funding lines for basic and applied research. The PMD initiative should include a combination of computational, experimental, and materials testing, characterization, and processing research conducted by government, industry, and academia.
Author: Cornelia Vasile
Publisher: iSmithers Rapra Publishing
ISBN: 9781859574935
Category : Science
Languages : en
Pages : 192
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Book Description
This practical guide begins with general background to the polyethylene family, with price, production and market share information. It describes the basic types of polyethylene including virgin and filled polyethylene, copolymers, block and graft polymers and composites, and reviews the types of additives used in polyethylene. It gives the low down on the properties, including, amongst others, rheological, mechanical, chemical, thermal, and electrical properties. It goes on to describe the processing issues and conditions for the wide range of techniques used for polyethylene, and also considers post-processing and assembly issues. It offers guidance on product design and development issues, including materials selection. It is an indispensable resource for everyone working with this material.
Author: Susmita Bose
Publisher: Elsevier Inc. Chapters
ISBN: 0128070951
Category : Science
Languages : en
Pages : 450
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Book Description
This brief introductory chapter provides a broad overview of materials, biomaterials and the need to understand different techniques to characterize biomaterials. From this chapter, the reader can gain a perspective on how the rest of the topics in different chapters are divided to fully comprehend this inherently multidisciplinary field. Application of appropriate characterization tools can not only save time to fully evaluate different biomaterials, it can also make commercial biomedical devices safer. In the long run, safer biomedical devices can only reduce the pain and suffering of mankind, a dream that resonates with every biomedical researcher.
Author: Xiaogang Chen
Publisher: Woodhead Publishing
ISBN: 1782424849
Category : Technology & Engineering
Languages : en
Pages : 548
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Book Description
Advanced Fibrous Composite Materials for Ballistic Protection provides the latest information on ballistic protection, a topic that remains an important issue in modern times due to ever increasing threats coming from regional conflicts, terrorism, and anti-social behavior. The basic requirements for ballistic protection equipment are first and foremost, the prevention of a projectile from perforating, the reduction of blunt trauma to the human body caused by ballistic impact, the necessity that they are thermal and provide moisture comfort, and that they are lightweight and flexible to guarantee wearer’s mobility. The main aim of this book is to present some of the most recent developments in the design and engineering of woven fabrics and their use as layering materials to form composite structures for ballistic personal protection. Chapter topics include High Performance Ballistic Fibres, Ultra-High Molecular Weight Polyethylene (UHMWPE), Ballistic Damage of Hybrid Composite Materials, Analysis of Ballistic Fabrics and Layered Composite Materials, and Multi-Scale Modeling of Polymeric Composite Materials for Ballistic Protection. Contributions from leading experts in the field Cutting edge developments on the engineering of ballistic materials Comprehensive analysis of the development and uses of advanced fibrous composite materials
Author: S. R. Reid
Publisher: Elsevier
ISBN: 1855738902
Category : Technology & Engineering
Languages : en
Pages : 320
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Book Description
This study covers impact response, damage tolerance and failure of fibre-reinforced composite materials and structures. Materials development, analysis and prediction of structural behaviour and cost-effective design all have a bearing on the impact response of composites and this book brings together for the first time the most comprehensive and up-to-date research work from leading international experts. State of the art analysis of impact response, damage tolerance and failure of FRC materials Distinguished contributors provide expert analysis of the most recent materials and structures Valuable tool for R&D engineers, materials scientists and designers
