Initiation phenomena in solid explosives produced by strong shock waves are described. Shock pressures in the explosive are between 20 and 200 kbar. It is demonstrated that in the usual case the shock wave travels not as an inert shock, but as a shock to which the explosive contributes energy, probably from reaction at voids and defects. This slightly reacting shock travels at increasing velocity for some distance, typically 1 cm in the experiments described, and then in a travel of perhaps 0.01 cm becomes full detonation, moving at full velocity. The increase to full detonation velocity occurs without overshoot. Experiments demonstrating the variation of sensitivity to shock with density, grain size, and other properties are discussed. The explosives studied are cyclotol B, TNT, plastic-bonded HMX, and nitromethane-carborundum mixtures.

The plane shock response of PBX 9502 was measured from 0.5 to 25 GPa. The explosive is 95-wL % triamino-trinitrobenzene powder coated with Kel-F 800 plastic; porosity was 2.6%. Shock initiation sensitivity, the Hugoniot, and dynamic yield behavior were studied. Experiments done were explosively driven wedge tests and particle velocity history measurements using electromagnetic gauges at a light-gas gun. A new analysis of the wedge test was implemented. Based on wedge test results, an approximation for the particle velocity at the shock front is constructed, which is used in functional composition with the Hugoniot to calculate the shock path of each experiment. Optimization on the parameters of the approximation and the Hugoniot simultaneously ensures agreement of the Hugoniot with the overall kinematics of the shock growth as wen as the particle velocity/shock velocity data. The individual shock paths are used to examine the single-curve buildup assumption; the assumption is not valid for PBX 9502. A ramping elastic precursor of 0.073 GPa strength was observed. The yield and weak shock behavior are interpreted in terms of porosity, crystaUine anisotropy, and residual strain in the pressed, plastic-bonded explosive.

The use of vehicle bombs to attack city centers has been a feature of campaigns by terrorist organizations around the world. A bomb explosion within or immediately nearby a building can cause catastrophic damage on the building's external and internal structural frames, collapsing of walls, blowing out of large expanses of windows, and shutting down of critical life-safety systems. Loss of life and injuries to occupants can result from many causes, including direct blast-effects, structural collapse, debris impact, fire, and smoke.The indirect effects can combine to inhibit or prevent timely evacuation, thereby contributing to additional casualties. In addition, major catastrophes resulting from gas-chemical explosions result in large dynamic loads, greater than the original design loads, of many structures. Due to the threat from such extreme loading conditions, efforts have been made during the past three decades to develop methods of structural analysis and design to resist blast loads. The analysis and design of structures subjected to blast loads require a detailed understanding of blast phenomena and the dynamic response of various structural elements. This paper presents a comprehensive overview of the effects of explosion on structures. An explanation of the nature of explosions and the mechanism of blast waves in free air is given. This paper also introduces different methods to estimate blast loads and structural response.

If the usual analysis of shock-wave data is made for polycrystalline plastic-bonded HMX and pressed TNT the experimental data extrapolate to the detonation pressure point rather than to the peak spike pressure point . This is indicative of a reactive wave, which is to be expected. Limitations based on the assumptions and analysis are discussed to show that it is not possible to infer any information about the shock properties of unreacted explosive from the available shock-wave daLa for solid explosives.Since no calculational model is available which will permit the computation of the details of initiation of solid explosives, empirical relationships are presented to summarize the data for engineering purposes.

The usual treatment of unsupportad detonation, often called the Chapman-Jouguet theory, is based on four assumptions: (1) the detonation approaches a steady state, (2) the flow is laminar and onedimensional, (3) the detonation products approach a state of chemical equilibrium some distance behind the detonation rront, and (4) the detonation velocity is the minimum permitted by the conservation conditions. In a recent paper Wood and Fickett (Phys. Fluids §, 648(1963)) proposed experiments to test the validity of the Chapman-Jouguet "theory", not requiring knowledge or assumptions about the nature of the equation of state of the detonation products, by making variations of the initial state or the explosive. In this paper we report the results of experiments in which (l) the initial state was varied by using mixtures of nitromethane and another liquid made or equal molar parts of nitric acid, acetonitrile, and '\'tater, which has the same atomic composition as ni tromethane, and (2) the initial state was varied by using TNT as liquid and as solid. These results show that the Chapman-Jouguet theory is violated. The calculated pressures are 15% to 20% below the measured pressures. Results of measurements using other explosives are also presented to support the conclusion that the theory fails. No explanation or alternative theory is orfered.