Dynamic Characterization of Frequency Response of Shock Mitigation of a Polymethylene Diisocyanate (PMDI) Based Rigid Polyurethane Foam PDF Download
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 17
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Book Description
Kolsky compression bar experiments were conducted to characterize the shock mitigation response of a polymethylene diisocyanate (PMDI) based rigid polyurethane foam, abbreviated as PMDI foam in this study. The Kolsky bar experimental data was analyzed in the frequency domain with respect to impact energy dissipation and acceleration attenuation to perform a shock mitigation assessment on the foam material. The PMDI foam material exhibits excellent performance in both energy dissipation and acceleration attenuation, particularly for the impact frequency content over 1.5 kHz. This frequency (1.5 kHz) was observed to be independent of specimen thickness and impact speed, which may represent the characteristic shock mitigation frequency of the PMDI foam material under investigation. The shock mitigation characteristics of the PMDI foam material were insignificantly influenced by the specimen thickness. As a result, impact speed did have some effect.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 17
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Book Description
Kolsky compression bar experiments were conducted to characterize the shock mitigation response of a polymethylene diisocyanate (PMDI) based rigid polyurethane foam, abbreviated as PMDI foam in this study. The Kolsky bar experimental data was analyzed in the frequency domain with respect to impact energy dissipation and acceleration attenuation to perform a shock mitigation assessment on the foam material. The PMDI foam material exhibits excellent performance in both energy dissipation and acceleration attenuation, particularly for the impact frequency content over 1.5 kHz. This frequency (1.5 kHz) was observed to be independent of specimen thickness and impact speed, which may represent the characteristic shock mitigation frequency of the PMDI foam material under investigation. The shock mitigation characteristics of the PMDI foam material were insignificantly influenced by the specimen thickness. As a result, impact speed did have some effect.
Author: Bo Song
Publisher: Elsevier
ISBN: 0128233265
Category : Technology & Engineering
Languages : en
Pages : 360
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Book Description
Summarizing the latest advances in experimental impact mechanics, this book provides cutting-edge techniques and methods for designing, executing, analyzing, and interpreting the results of experiments involving the dynamic responses of materials and structures. It provides tailored guidelines and solutions for specific applications and materials, covering topics such as dynamic characterization of metallic materials, fiber-like materials, low-impedance materials, concrete and more. Damage evolution and constitutive behavior of materials under impact loading, one-dimensional strain loading, intermediate and high strain rates, and other environmental conditions are discussed, as are techniques using high temperature testing and miniature Kolsky bars. Provides cutting-edge techniques and methods for designing, executing, analyzing, and interpreting the results of experimental impact mechanics Covers experimental guidelines and solutions for an array of different materials, conditions, and applications Enables readers to quickly design and perform their own experiments and properly interpret the results Looks at application-specific post-test analysis
![Pre-strain Effect on Frequency-based Impact Energy Dissipation Through a Silicone Foam Pad for Shock Mitigation [Pre-strain Effect on the Frequency Response of Shock Mitigation Through a Silicone Foam Pad]. PDF](https://books.google.com/books/content/images/frontcover/lh3VtwEACAAJ?fife=w80-h100)
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 8
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Book Description
Silicone foams have been used in a variety of applications from gaskets to cushioning pads over a wide range of environments. Particularly, silicone foams are used as a shock mitigation material for shock and vibration applications. Understanding the shock mitigation response, particularly in the frequency domain, is critical for optimal designs to protect internal devices and components more effectively and efficiently. The silicone foams may be subjected to pre-strains during the assembly process which may consequently influence the frequency response with respect to shock mitigation performance. A Kolsky compression bar was modified with pre-compression capabilities to characterize the shock mitigation response of silicone foam in the frequency domain to determine the effect of pre-strain. Lastly, a silicone sample was also intentionally subjected to repeated pre-strain and dynamic loadings to explore the effect of repeated loading on the frequency response of shock mitigation.
Author:
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ISBN:
Category :
Languages : en
Pages : 17
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 82
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Book Description
The dynamic characteristics of six rigid polyurethane foams were studied at impact velocities from 15.24 to 60.96 m/s (50 to 200 ft/sec). A test technique developed for crushing confined samples is described. The dynamic properties of materials tested are reported by both graphical and tabular methods.
Author: William Monroe Hinckley
Publisher:
ISBN:
Category :
Languages : en
Pages : 160
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Author: Andrew Harvey Fulton
Publisher:
ISBN:
Category :
Languages : en
Pages : 332
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Book Description
This study examined the mechanical response of four polymeric foams under quasi-static and dynamic loading conditions to explore the protective impact mitigation applications of polymeric cellular materials. Polyethylene, polyurethane, and polystyrene, all with relative densities between 1.5-3%, and a bilayer polymeric foam with a trademarked name Zorbium were the four foams analyzed. With the extensive use of image analysis techniques (digital image correlation), the quasi-static local strain behavior of these cellular materials was determined. The dynamic impacts, using a gas gun apparatus and high-speed camera imaging in direct impact experiments, were evaluated to study the dynamic shock response. The experiments generally show a much greater dynamic stress response for the foams compared to their quasi-static responses and suggest a significant difference from the slow rate compressive response. Higher impact velocities resulted in shock formation and propagation. Using conservation of momentum and Rankine-Hugoniot jump conditions, the stresses in the foams were determined. The Shock-Hugoniot of impact velocity and shock wave speed was generated from the experimental results to characterize the high-speed dynamic response of the four foams. The two-layer composite foam, with differing stiffnesses and similar pore sizes, in slow and fast impact experiments, is discussed and analyzed using similar methods used for polyethylene, polyurethane, and polystyrene foams. Finally, the impact problem is examined numerically using the method of characteristics; the results of these simulations are used to determine the force transmission characteristics of protective foam layers. This method is shown to be an effective tool for design
Author: Sarah Nicole Scott
Publisher:
ISBN:
Category :
Languages : en
Pages : 118
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Book Description
Polymer foam encapsulants provide mechanical, electrical, and thermal isolation in engineered systems. It can be advantageous to surround objects of interest, such as electronics, with foams in a hermetically sealed container to protect the electronics from hostile environments, such as a crash that produces a fire. However, in fire environments, gas pressure from thermal decomposition of foams can cause mechanical failure of the sealed system. In this work, a detailed study of thermally decomposing polymeric methylene diisocyanate (PMDI)-polyether-polyol based polyurethane foam in a sealed container is presented. Both experimental and computational work is discussed. Validation experiments, called Foam in a Can (FIC) are presented. In these experiments, 320 kg/m3 PMDI foam in a 0.2 L sealed steel container is heated to 1073 K at a rate of 150 K/min and 50 K/min. FIC is tested in two orientations, upright and inverted. The experiment ends when the can breaches due to the buildup of pressure from the decomposing foam. The temperature at key locations is monitored as well as the internal pressure of the can. When the foams decompose, organic products are produced. These products can be in the gas, liquid, or solid phase. These experiments show that the results are orientation dependent: the inverted cans pressurize, and thus breach faster than the upright. There are many reasons for this, among them: buoyancy driven flows, the movement of liquid products to the heated surface, and erosive channeling that enhance the foam decomposition. The effort to model this problem begins with Erickson's No Flow model formulation. In this model, Arrhenius type reactions, derived from Thermogravimetric Analysis (TGA), control the reaction. A three-step reaction is used to decompose the PMDI RPU (rigid polyurethane foam) into CO2, organic gases, and char. Each of these materials has unique properties. The energy equation is used to solve for temperature through the domain. Though gas is created in the reaction mechanism, it does not advect, rather, its properties are taken into account when calculating the material properties, such as the effective conductivity. The pressure is calculated using the ideal gas law. A rigorous uncertainty quantification (UQ) assessment, using the mean value method, along with an analysis of sensitivities, is presented for this model. The model is also compared to experiments. In general, the model works well for predicting temperature, however, due to the lack of gas advection and presence of a liquid phase, the model does not predict pressure well. Porous Media Model is then added to allow for the advection of gases through the foam region, using Darcy's law to calculate the velocity. Continuity, species, and enthalpy equations are solved for the condensed and gas phases. The same reaction mechanism as in the No Flow model is used, as well as material properties. A mesh resolution study, as well as a calibration of parameters is conducted, and the model is compared to experimental results. This model, due to the advection of gases, produces gravity dependent results that compare well to experiment. However, there were several properties that had to be calibrated, and replacing these calibrated parameters with physically derived values is desired. To that end, Vapor Liquid Equilibrium (VLE) equations are added to the Porous Media model. These equations predict the vapor/liquid split of the organic decomposition products based on temperature and pressure. UQ for the parameters in the model as well as a sensitivity study is presented, in addition to comparison to experiment. The addition of the VLE improved temperature and pressure prediction, both qualitatively and quantitatively.
Author: B. L. Neal
Publisher:
ISBN:
Category :
Languages : en
Pages : 12
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Book Description
Author: Michael Szycher, Ph.D
Publisher: CRC Press
ISBN: 1439839581
Category : Technology & Engineering
Languages : en
Pages : 1147
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Book Description
A practical handbook rather than merely a chemistry reference, Szycher's Handbook of Polyurethanes, Second Edition offers an easy-to-follow compilation of crucial new information on polyurethane technology, which is irreplaceable in a wide range of applications. This new edition of a bestseller is an invaluable reference for technologists, marketers, suppliers, and academicians who require cutting-edge, commercially valuable data on the most advanced uses for polyurethane, one of the most important and complex specialty polymers. internationally recognized expert Dr. Michael Szycher updates his bestselling industry "bible" With seven entirely new chapters and five that are revised and updated, this book summarizes vital contents from U.S. patent literature—one of the most comprehensive sources of up-to-date technical information. These patents illustrate the most useful technology discovered by corporations, universities, and independent inventors. Because of the wealth of information they contain, this handbook features many full-text patents, which are carefully selected to best illustrate the complex principles involved in polyurethane chemistry and technology. Features of this landmark reference include: Hundreds of practical formulations Discussion of the polyurethane history, key terms, and commercial importance An in-depth survey of patent literature Useful stoichiometric calculations The latest "green" chemistry applications A complete assessment of medical-grade polyurethane technology Not biased toward any one supplier’s expertise, this special reference uses a simplified language and layout and provides extensive study questions after each chapter. It presents rich technical and historical descriptions of all major polyurethanes and updated sections on medical and biological applications. These features help readers better understand developmental, chemical, application, and commercial aspects of the subject.
