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 Download
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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.
![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: 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
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 3
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Author:
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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:
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ISBN:
Category :
Languages : en
Pages : 17
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Book Description
Author: Troy Leonard Totten
Publisher:
ISBN:
Category : Cushioning materials
Languages : en
Pages : 172
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 116
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Book Description
This study investigated the effectiveness of foam linings in mitigating shock waves in tunnels. A polyurethane foam liner of varying density, crush strength and thickness was modeled inside a 1 meter radius tunnel and an explosion of 1.25 kg of plastic explosive was simulated. Using CTH, an Eulerian- Lagrangian hydrodynamics code from Sandia National Laboratories, the overpressures were computed and compared graphically to determine the effect of varying each foam parameter. The walls of the tunnel consisted of a perfectly reflecting boundary, and in some cases, a foam liner. Low density foam provided the most shock attenuation. with a 20 cm thick layer of 90% void (0. 1265 g/cm3) foam reducing the shock overpressure by 70% at 50 meters. The effects of foam thickness on the shock pressure varied with the distance from the explosion. The thicker foams raised the initial pressure near the explosion due to constriction of the tunnel area. However, the thicker layers reduced the shock faster. Varying the crush strength of the foam from 1 atm to 3 atm overpressure did not affect its ability to mitigate shock propagation in the tunnel. The results of this study strongly suggest that foam can mitigate shock waves significantly ... Shock, Shock mitigation, Foam, Explosions.
Author:
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ISBN:
Category :
Languages : en
Pages :
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Book Description
Sandia National Laboratories (SNL) designs mechanical systems with electronics that must survive high shock environments. These mechanical systems include penetrators that must survive soil and rock penetration, nuclear transportation casks that must survive transportation environments, and laydown weapons that must survive delivery impact. These mechanical systems contain electronics that may operate during and after the high shock environment and that must be protected from the high shock environments. A study has been started to improve the packaging techniques for the advanced electronics utilized in these mechanical systems because current packaging techniques are inadequate for these sensitive electronics. In many cases, it has been found that the packaging techniques currently used not only do not mitigate the shock environment but actually amplify the shock environment. An ambitious goal for this packaging study is to avoid amplification and possibly attenuate the shock environment before it reached the electronics contained in the various mechanical systems. Here, a study to compare two thickness values, 0.125 and 0.250 in. of five materials, GE RTV 630, HS II Silicone, Polysulfide Rubber, Sylgard 184, and Teflon for their shock mitigating characteristics with a split Hopkinson bar configuration has been completed. The five materials have been tested in both unconfined and confined conditions at ambient temperature and with two applied loads of 750[mu][epsilon] peak (25 fps peak) with a 100[micro]s duration, measured at 10% amplitude, and 1500[mu][epsilon] peak (50 fps peak) with a 100[micro]s duration, measured at 10% amplitude. The five materials have been tested at ambient, cold ([minus]65 F), and hot (+165 F) for the unconfined condition with the 750[mu][epsilon] peak (25 fps peak) applied load. Time domain and frequency domain analyses of the split Hopkinson bar data have been performed to compare how these materials lengthen the shock pulse, attenuate the shock pulse, reflect high frequency content in the shock pulse, and transmit energy.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 17
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Book Description
This memo concerns the transmission of mechanical signals through silicone foam pads in a compression Kolsky bar set-up. The results of numerical simulations for four levels of pad pre-compression and two striker velocities were compared directly to test measurements to assess the delity of the simulations. The nite element model simulated the Kolsky tests in their entirety and used the hyperelastic `hyperfoam' model for the silicone foam pads. Calibration of the hyperfoam model was deduced from quasi-static compression data. It was necessary, however, to augment the material model by adding sti ness proportional damping in order to generate results that resembled the experimental measurements. Based on the results presented here, it is important to account for the dynamic behavior of polymeric foams in numerical simulations that involve high loading rates.
Author: J. Singh
Publisher:
ISBN:
Category : Cushion curves
Languages : en
Pages : 7
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Book Description
Mechanical stresses experienced by packages in the distribution environment include shock and vibration amongst several others. The destructive effects of these hazards can typically be restricted by using cushioning materials to help protect fragile goods during distribution. ASTM D1596 is the conventional standard used to determine shock absorbing performance of a cushioning material for a given combination of static loading, thickness, and drop height. This industry-accepted standard, however, requires significant amounts of transmitted shock data and can be expensive with respect to costs associated with testing and materials amongst others. Alternate stress-energy-based methodologies, developed in the past decade, recommending a considerable reduction in the number of drop tests while providing the ability to predict transmitted shock for any drop height, static loading as well as cushion thickness, are evaluated in this study for their stated accuracy. Based upon an in-depth evaluation of dynamic cushion curves for closed cell moldable foams generated using ASTM D1596, this research evaluates the accuracy of the proposed methodology in relation to the prediction of transmitted shock. Results show that the stress-energy methods while saving time in predicting transmitted shock, produce higher degrees of error than the ±5 % previously stated. In addition, they cannot predict behavior of cushions, and transmitted shock at high drop heights and static loadings with thin cushions, where only the measured values are accurate.
