Mechanical Shock, and Impact

BIETHYLENE (106-99-0) QH Extremely flammable, polymerizable gas extremely low ignition temperature makes it very dangerous [explosion limits in air (vol %) 2.0 to 11.5 flash point -105°F/-76°C autoignition temp 788°F/420°Ct Fire Rating 4]. Self-reactive. In absence of an inhibitor (e.g., ferf-butyl catechol), autoxidation forms heat-, mechanical shock-, and impact-sensitive peroxides with air. Fires, explosions, or hazardous polymerization may result from contact with strong oxidizers, aliuninumtetrahydroborate, copper, high copper alloys, chlorine dioxide. 

Definitions and Characterization of Vibration, Mechanical Shock, and Impact... 

Decomposition Hazards. The main causes of unintended decompositions of organic peroxides are heat energy from heating sources and mechanical shock, eg, impact or friction. In addition, certain contaminants, ie, metal salts, amines, acids, and bases, initiate or accelerate organic peroxide decompositions at temperatures at which the peroxide is normally stable. These reactions also Hberate heat, thus further accelerating the decomposition. Commercial products often contain diluents that desensitize neat peroxides to these hazards. Commercial organic peroxide decompositions are low order deflagrations rather than detonations (279). 

Laminae 4116 and Selectron 5003, were found to be satisfactory and interchangeable for use in these compns. These expls are thermally stable, relatively insensitive to mechanical shock, and have a brisance approaching that of Comp C-3. Weight-drop impact tests indicate them to be of the order of sensitivity of TNT... 

Examples of equipment for mechanical shock or impact testing are the BAM Fallhammer, the Rotter test, the thirty kilogram Fallhammer test, and the Bureau of Mines Impact Apparatus [45]. The latter is shown in Figure 2.31. 

The need for great care to avoid the possibility of detonation of perchloryl compounds by exposure to shock, overheating or sparks is stressed. The compounds are generally more sensitive to impact than mercury fulminate and are of comparable sensitivity to lead azide [1], A range of highly explosive alkyl perchlorates [2] and perchlorylamines [3] have been prepared by interaction of dichlorine heptaoxide with alcohols or amines in carbon tetrachloride solution. The solutions of the products were not sensitive to mechanical shock and could... 

CA 59, 12585(1963) (Impact tester is described for detg relative sensitivity to mechanical shock by impact of a 10-kg wt falling 25cm on 7--, 10- 50-mg samples. Relative sensitivity in terms of % explns and rebound of wc as a % of its fall are reported)... 

The recent AFM experimental data concerning plastic flow place severe restrictions on possible theoretical accounts of plastic deformation in crystalline solids due to shock or impact. The high spatial resolution of the AFM, = 2 x lO " m, reveals substantial plastic deformation in shocked or impacted crystal lattices and molecules. Understanding how this occurs and its effect on plastic flow requires a quantum mechanical description. The semi-permanent lattice deformation has necessitated the development of a deformed lattice potential which, when combined with a quantum mechanical theory of plastic deformation, makes it possible to describe many of the features found in the AFM records. Both theory and the AFM observations indicate that shock and impact are similar shear driven processes that occur at different shear stress levels and time durations. The role of pressure is to provide an applied shear stress sufficient to cause initiation. 

Animals. Employing the results of experiments with animals to predict biodynamic responses in humans introduces uncertainties associated with interspecies differences. Of particular concern is the difference in size of body parts and organs, which influences resonance frequencies. For this reason, most animal research on the limit of exposure to rapid horizontal deceleration and to vertical acceleration, which commonly involves shock and impact, has employed mammals of roughly similar size and mass to man (i.e., pigs and chimpanzees). Research on pathophysiological mechanisms... 

Hamouda, A. M. S. and Hashmi, M. S. J. Simulation ofthe Impact ofa Tool Steel Projectile into Copper, Mild-steel, Stainless-steel (304) Test Specimens. In Structures Under Shock and Impact. Bulson, P. S. (Ed.) Computational Mechanics Publications, pp. 51-61, 1992. 

Sensitivity of high energy materials (EMs) is primarily due to the chemical character of the materials this means it is possible to use the term initiation reactivity of EMs in this case. However, the means of transfer of the initiation impulse to the reaction centre of the EM molecule or the molecule of the most reactive component of the explosive mixture is also of great importance. Therefore, according to Dlott a complex solution to the problem of initiation must involve the areas of continuum mechanics, chemistry and quantum mechanics (quantum chemistry) (1). The main interest has been focused on studies of shock and impact sensitivities of EMs. In the last 16 years the preferred tools for the solution of these sensitivities have involved quantum chemistry [1-5]. The appUcation of chemistry to these problems is relatively reluctant and mostly without any broader contexts. Nevertheless, the approach of physical organic chemistry has been apphed not only to studies of impact and shock reactivity [6,7], but also sensitivity to electric spark [6,8], and in part to thermal reactivity of EMs [7] as well. This survey presents development trends of studies of initiation reactivity of EMs over the last nine years with emphasis on the contribution of physical organic chemistry to these studies. Research results presented at conferences and seminars are quoted here only as the exception. 

Standard surface mount components do not require an underfill, however when assembling some CSPs onto organic PCBs, underfill may be required to increase the thermal and mechanical reliability of the interconnections. Some types of CSPs have a compliant elastomeric layer that decouples the chip-to-carrier body thermal expansion mismatch induced strains. That is the stresses exerted on the solder connections are dissipated by an elastomer that mechanically isolates the silicon die from its flexible polyimide film interposer. Those component designs which do not provide sufficient decoupling between die and carrier require an underfill to satisfy the reliability requirements for some applications. In addition, the components in hand-held consumer products are often underfilled to improve the mechanical robustness of an assemblies ability to withstand drop and shock resistance. Shock and impact requirements for CSPs in portable products may exceed 2,000 G accelerations. 

As hydrazine is an endothermic compound that decomposes exothermically, its derivatives and metal complexes are also highly unstable and some of them fall into the category of high energy materials (HEMs). For such HEMs it becomes essential to test their properties by friction and impact sensitivity tests along with standard techniques like TG/DTA or DSC. This allows for differentiation between HEMs that are classified as primary that is, very sensitive materials which easily explode by the application of fire, spark, impact, friction, and so on, and HEMs that are classified as secondary, that is, materials that are relatively insensitive to both mechanical shock and flame but explode with greater violence when set off [38],... 

Typically polymers are used as dampers and isolators to mitigate mechanical vibration, noise, shock, and impact. Applications include... 

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