Comparative initiating strength

The comparative initiating strength of different types of primary explosives may be obtained in a similar way—on the basis of the dent depth produced in the steel witness plate after the detonation of the primary explosive alone. For this, 300 mg of primary explosive alone is press-loaded at 1115 kp/cm into a PMMA sample holder, wliich is then placed on the steel witness plate. The initiation of the primary explosive is performed by means of the safety fuse. The depth of the dent produced in the steel witness plate after the detonation of the primary explosive is connected with its initiating performance and serves for the comparative evaluation of the initiating strength of different types of primary explosives. 

Tablets were prepared either with an insoluble (dicalcium phosphate dihydrate), a soluble (6-lactose) or a moderately soluble filler-binder (a-lactose monohydrate). As a disintegrant four different starches (com, rice, potato and tapioca) were used. As a comparison the effect of two super-disintegrants (crospovidone and sodium starch glycolate) was studied. The disintegrants were added at two concentration levels. The compression load was adjusted in order to obtain tablets with comparable initial cmshing strengths.

Copper substrates are commonly bonded with epoxy adhesives in the microelectronics and marine industries. Compared to aluminum substrates, copper when bonded with epoxy adhesives provides lower initial strength. Depending on the adhesive and the type of test used, this can be as much as 50 percent lower. Similar to aluminum joints, copper joints bonded with epoxy adhesives can show poor durability in moist environments unless the interface is protected. 

Since we have no information on the relative strengths of the internal and external vibrations the simplest isotropic representation is used and its initial strength is estimated ( 2.6.3). The observed INS spectrum is shown in Fig. 5.5(upper), where it is compared with the calculated spectrum, Fig. 5.5(lower), using program default values. 

Certain polyaxial copolymers can be converted to compliant monofilaments with comparable, or superior, initial strength relative to surgical gut sutures. 

Figure 9.8 Effect of proof testing on space shuttle tile materials. Compared to the initial strength distribution, the strength of the surviving specimens was found to be truncated close to the maximum proof stress. (From Green et al, 1982, reproduced courtesy of The American Ceramic Society, Westerville, OH.)...

Taking into account the higher level of initial strength of Si3N4-based ceramics the remaining strength after hot corrosion is usually higher compared to SiC. 

It should be pointed out that the initiating strength of primary explosives depends on several factors, such as explosive purity, leading density, confinement conditions, etc. Thus, the results obtained by different testing methods are not directly comparable. 

Ahrens, H. On the comparative evaluation of the initiating strength of detonators by indirect method, Explosivstoffe 3, 93-95 (1973). 

Performance and durability of wood products bonded with isocyanate and urethane adhesives have been the subject of several investigations. The strength of composition board is generally determined by its modulus of rupture (MOR), which is a flexure to break test its modulus of elasticity (MOE), or stiffness and its internal bond strength (IB), or tensile strength. These tests are run on dry and on water-soaked or wet samples, and are described in ASTM test method D 1037. As compared to phenol-formaldehyde adhesives, composition boards prepared with isocyanate or urethane adhesives are reported to display similar or superior initial strengths. Moisture resistance of isocyanate-bound par-... 

In a review of previous work, DeLollis concluded that the nitrile-phenolic is the most durable adhesive, surviving all environmental exposures. The nylon-epoxy adhesive performed well on exposure to medium-humidity environments, but was susceptible to high humidities. The nitrile-epoxies showed good resistance to most outdoor exposures except the seacoast environment, where bonds failed after four years. Epoxy/polyamide bonds gave good results after four years exposure to an industrial environment and joints exposed to a tropical climate had retained about 33% of their initial strength after three years. This performance should be compared with that of some heat-cured adhesives, for which the bonds are completely degraded by tropical exposure. 

The data in Table 3-23 indicate that no material lost more than about 5% in tensile strength in one year. Also, the three-month loss was comparable to the loss for the entire year. For example, the tensile strength of polystyrene had California values of 12,350 psi and 12,100 psi for 3 mo and 1 yr, respectively, while the initial strength was 13,600 psi. This behavior is attributed to initial water absorption and formulation of a partially degraded or photooxidized surface which acts as a barrier to prevent further degradation. These effects are quite rapid and would certainly be complete within 3 mo. if not within the first few weeks of exposure ... 

To classify redox couples with respect to their strength, a trick is used that is similar to that used with acid-base equilibria. Consider what would happen if the redox couple studied was brought to react with a standard partner . Long ago, the couple hydrogen gas/hydrogen ion (H2/H30 ) was chosen to act as the standard partner. To solve the problem of comparing the strength of redox couples, we simply initiate the reaction and, after equilibrium has been established, determine the actual equilibrium constant (as with acid-base equilibria). This time, however, the classification is done in a somewhat different way. 

With an initial strength of 144 N/mm in the glass fiber mat reinforced laminate and 386 N/mm in the fabric laminate, both test materials were loaded at 30 and 60 N/mm. It can be clearly seen that damage occurs earlier under higher stress. The more rapid reduction in the glass fiber mat reinforced laminate can be explained by the fact that the relative load level is notably higher compared to the... 

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