On the energy conservation and critical velocities for the propagation of a "steady-shock" wave in a bar made of cellular material

The propagation of shock waves in a cellular bar is systematically studied in the framework of continuum solids by adopting two idealized material models, viz. the dynamic rigid, perfectly plastic, locking （D-R-PP-L） model and the dynamic rigid, linear hardening plastic, locking （D-R-LHP-L） model, both considering the effects of strain-rate on the material properties. The shock wave speed relevant to these two models is derived. Consider the case of a bar made of one of such material with initial length L 0 and initial velocity v i impinging onto a rigid target. The variations of the stress, strain, particle velocity, specific internal energy across the shock wave and the cease distance of shock wave are all determined analytically. In particular the ＂energy conservation condition＂ and the ＂kinematic existence condition＂ as proposed by Tan et al. （2005） is re-examined, showing that the ＂energy conservation condition＂ and the consequent ＂critical velocity＂, i.e. the shock can only be generated and sustained in R-PP-L bars when the impact velocity is above this critical velocity, is incorrect. Instead, with elastic deformation, strain-hardening and strain-rate sensitivity of the cellular materials being considered, it is appropriate to redefine a first and a second critical impact velocity for the existence and propagation of shock waves in cellular solids. Starting from the basic relations for shock wave propagating in D-R-LHP-L cellular materials, a new method for inversely determining the dynamic stress-strain curve for cellular materials is proposed. By using e.g. a combination of Taylor bar and Hopkinson pressure bar impact experimental technique, the dynamic stress-strain curve of aluminum foam could bedetermined. Finally, it is demonstrated that this new formulation of shock theory in this one-dimensional stress state can be generalized to shocks in a one-dimensional strain state, i.e. for the case of plate impact on cellular materials, by simply making proper replacements of the elastic and plastic constants.

The Ultracytochemical Effects of High Energy Shock Wave on Rabbit Liver

The ultracytochemical effects in the liver of rabbit undergoing high energy shock wave (HESW) were studied with electron microscope. The application of lanthanum as a tracer for ultrastructural study demonstrated that intracellular lanthanum could be observed, most of which entered the hepatocytes and its mitochondria. The lanthanum granules were also found to deposite in the zone of tight junctions of bile canaliculi, which indicated that the tight junctions had been damaged. The activities of succinate dehydrogenase (SDH) in liver cells, alkaline phosphatase (ALP) and thiamine pyrophosphatase (TPPase) on the wall of bile canaliculi became diminished obviously. Both the activites and localizations of TPPase had changed. Some TPPase from the damaged lysosome like vesicles and Golgi saccules of liver cells discharged into cytoplasm. TPPase reaction production in some bile canaliculi decreased. In the intercellular space of the liver cells and the tight junctions of bile canaliculi TPPase reaction could be seen. Ultrastructurally, the changes commonly seen were hydropic mitochondria and dilatation of rough endoplasmic reticulum. Serologic test demonstrated that there was an abnormal change of SGPT, SGOT and ALP. The results showed that HESW can damage the ultrastructure and function of liver.

Simulation of the relationship between roadway dynamic destruction and hypocenter parameters

Many factors can induce rock burst. Shock energy and shock distance are two key factors affecting rock burst. The 32101 roadway of the Xingcun coal mine, which has a tendency for rock burst, was used as an example. The dynamic module of Itasca’s FLAC (Fast Lagrangian Analysis of Continua) 2D explicit finite-difference software was used to simulate the roadway’s destruction. The vibration velocity and displacements of the rock surrounding the roadway were modeled for different shock energies and hypocenter distances. The simulation results indicate that the vibration velocity and displacement of rock surrounding the roadway have a quadratic relationship to the shock energy and a power law relationship to the distance of the hypocenter from the roadway. A dynamic view of the process was obtained from a series of "snap-shots" collected at 100 different time steps. This shows an isolating "river" is first formed at the hypocenter. The region above the "river" is a low stress zone while below the "river" a high stress zone exists. This high stress zone surrounds the ribs of the roadway in a "double ear" pattern. Continuous and repeated action of the high stress in the "double ear" shaped zone destroys the roadway.

Radial explosion strain and its fracture effect from confined explosion with charge of cyclonite

Instrumented experiments were conducted in concrete models to study the explosion-induced radial strain and fracture effect of rock-like media under confined explosion with a charge of cyclonite. As a charge was exploded, two different radial strain waves were sequentially recorded by a strain gage at a distance of 80 mm from the center of charge. Through the attenuation formula of the maximum compressive strain(εrmax), the distribution of εrmax and its strain rate（ ） between the charge and gage were obtained. The effect of the two waves propagating outwards on the radial fracture of surrounding media was discussed. The results show that the two waves are pertinent to the loading of shock energy （Es） and bubble energy （Eb） against concrete surrounding charge, respectively. The former wave lasts for much shorter time than the latter. The peak values of εrmax and of the former are higher than those of the latter, respectively.

Shock waves and water wing in slit-type energy dissipaters

The slit-type energy dissipater（STED）is widely used in hydraulic projects of high water head,large discharge,and narrow river valley,thanks to its simple structure and high efficiency.However,the water wing caused by the shock waves in the contraction section of the STED may bring about harmful effects.A coefficient is introduced for the application of Ippen？s theory in the STED.The expression of the coefficient is experimentally obtained.Simplified formulas to calculate the shock wave angle and the water wing scope are theoretically derived,with relative errors within 5%.