Failure thickness

Fig 1 Minimum Failure thickness Test Assembly (from Ref 4)... 

The booster expl may cause an artificially energetic and rapid detonation, called overdrive, in the sample. To correct for overdrive, wedges with apex angles of 1,2,3,4, and 5° are fired, and the resulting failure thicknesses are plotted vs angle. A linear curve is fitted through the data and extrapolated to 0°, and the failure thickness at (T is designated the detonation failure thickness. (Fig 1)... 

If the brass plate were completely incompressible, the failure thickness so determined would be half that of an unconfined infinite sheet. The failure thickness of an unconfined sheet is less than the failure diameter of a cylinder because rarefactions in a cylinder enter from all sides of the charge and influence the detonation. Thus, the failure diameter may be several times the failure thickness and may vary from one expl to another. More complete details are given in Ref 3... 

The reader is referred to Ref 1 for a voluminous compilation of detonation properties (detonation velocity and diameter effect, cylinder test performance, plate dent test and detonation failure thickness), shock initiation properties (wedge test data and small and large - scale gap tests), and sensitivity tests (skid test, large-scale drop test or spigot test and spark sensitivity) relevant to LASL research expls Refs 1) T.R. Gibbs A. Popolato, LASL Explosive Property Data , Univ of California Press, Berkeley (1980) 2) B.M. Dobratz,... 

Similar to Df, but for plates or slabs of explosive, there is a failure thickness that can and has been measured. These experiments, to determine failure thickness, are run on tapered explosive wedges initiated at the thicker end. The tests are conducted using a brass witness plate to indicate where failure occurred. 

Since the brass affords heavy confinement on one side of the explosive, and steel bars confine the sides, the failure thickness measured is most likely less than that for an unconfined explosive wedge. Figure 21.13 shows the test setup and Table 21.6 the test results for several explosives. 

Data for, and estimates of, D( and failure thickness are obviously important to the designer or analyst in spotting potential detonation reliability problems where explosive charges or systems must be minimized in size and weight. 

The failure thickness of slabs of PBX-9502 confined by air, Plexiglas, Aluminum, Copper and Tungsten were modeled. Ramsay measured the failure thickness of PBX-9502 confined by air, Plexiglas, Aluminum and Copper. The results of the experiments and the modeling are shown in Table 4.3. 

The large temperature difference of the remarkable borehole, opposite other boreholes and their environment is significant. This high temperature difference is a typical feature for a small wall thickness between borehole and blade surface. For technical reasons, precise eroding of the boreholes is difficult. Due to this, the remaining wallthickness between the boreholes and the blade surface has to be determined, in order to prevent an early failure, Siemens/Kwu developed a new method to determine the wallthickness with Impulse-Video-Thermography [5],... 

Equations 1 to 3 enable the stresses which exist at any point across the wall thickness of a cylindrical shell to be calculated when the material is stressed elastically by applying an internal pressure. The principal stresses cannot be used to determine how thick a shell must be to withstand a particular pressure until a criterion of elastic failure is defined in terms of some limiting combination of the principal stresses. 

Load bend fatigue strength of alloys capable of withstanding 4—5 cycles before failure in 0—90—0 degree cycles, which is above the three-cycles-to-failure minimum in MIL-S l D-883 values pertain to a 0.25-mm thick strip that has been sheared to 0.45-mm width. 

Wear owing to corrosion and/or erosion can be particularly dangerous. For example, as carbon steel corrodes, the reduced wall thickness can eventually lead to a stmctural failure. This problem can be compounded through erosive wear of the silo wall. 

When the design temperatures are significantly below ambient temperature, the primary threat to tank integrity is failure of the material by britde fracture. The tank design codes usually provide thorough treatment of this topic to prevent catastrophic failure. Additionally, there is the consideration of corrosion allowance, defined as extra thickness added beyond that required for strength. Corrosion allowance is not discussed herein. 

In North America, a special, high conductivity, low permeability, "hot-pressed" carbon brick is utilized almost exclusively for hearth walls. Because of their relatively small size and special, heat setting resin cement, and because the brick is installed tightly against the cooled jacket or stave, differential thermal expansion can be accommodated without refractory cracking and effective cooling can be maintained. Additionally, the wall thickness is generally smaller than 1 m, which promotes the easy formation of a protective skull of frozen materials on its hot face. Thus hearth wall problems and breakouts because of carbon wall refractory failure are virtually nonexistent. 

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