Volume 13, Issue 3-4 -

For an explosive source used in seismic exploration, evaluating its seismic wave energy caused by explosives exploding in the soil is an important issue. The direct method, calculating RMS (root mean square) amplitude of the seismic wave propagation in different time fields, is usually used to appraise this seismic wave energy. However, the result of calculating is not only comparatively imprecise, but also the analysis on the records of seismic wave is very complex and much labor-consuming. Even so an easier and more economical way for evaluating the energy of blast-induced seismic wave is needed. In this paper, a potential pressure measuring method in the elastic zone was proposed. The experimental results showed that under the same geological condition and the same experiment condition, the characteristic of pressure wave in the elastic zone was applicable to evaluate the energy of blast-induced seismic wave.

A series of tensile tests for pure copper sheets containing drilled holes of multi-configurations are carried out on a tensile split Hopkinson bar (TSHB) at a range of tensile velocities. The dynamic growth and coalescence of drilled voids were recorded by a high-speed camera. The results of scanning electron microscopical (SEM) investigation of microvoid evolution at edges of ruptured zones between drilled voids in recovered sheets show void coalescence mechanisms, which are similar to evolution of visualized drilled voids. The experimentally recovered and high-speed camera recorded evolution of drilled voids in pure copper sheets are compared with the numerical simulations involving different models for void coalescence in order to overcome the difficulty of assessing the validity of available models for void coalescence. The possible application of Thomason model and Brown–Embury model for void coalescence to thermoviscoplastic material was explored under impact tension, and the rapid local straining of intervoid ligament was revealed.

The energy absorption characteristics of foam materials can be represented by specific energy absorption W , energy absorption efficiency E and ideal energy absorption efficiency I . The influences of strain rate, cell size, relative density and the content of SiC on energy absorption characteristics of magnesium alloy foam were investigated by dynamic compression experiments. The experimental results showed that the cell size of magnesium alloy foam had significant effect on energy absorption characteristics and the strain rate effect of closed-cell AZ91 magnesium with larger cell size was more sensitive, and the strain rate effect was more sensitive to the closed-cell AZ91 magnesium with larger cell size. The energy absorption characteristics could be optimized by adjusting the cell size. Moreover, the influence of relative density on energy absorption characteristics was not significant and high content of SiC particle had unfavorable effect on energy absorption properties of magnesium foam.

For describing the dynamic evolution of debris cloud formed in oblique hypervelocity impact, a model (expressed in polar coordinates) for the shape, the velocity distribution and the mass distribution is developed according to the results of experiments and numerical simulation, and parameters of the Model are identified by nonlinear integral equations which are derived from mass conservation law and energy conservation law. Afterwards, the model has been verified by another simulation code.

The dynamic behavior of simple supported rectangular thin plate subjected to transverse harmonic excitation is investigated in this paper. The compressive loads N 1 and N 2 is applied on edges of the plate. On assumption of small deformation, dynamic governing equation is derived. The constitutive relation of material obeys can be stood for an integral equation. By use of nonlinear Galerkin method, the partial differential governing equation is turned into integral-differential variation of the Duffing equation. The different kinds of behaviors are investigated making use of the classical tools of nonlinear dynamics, such as the phase portrait, the time-displacement history and Lyapunov exponent analysis. The results of analysis show that the values of N 1 and N 2 , character time of material have large influence on the dynamic response. When they satisfy some condition, chaotic motions may occur in the dynamic system.

Ballistic impact characteristics on the flat-nose projectile penetrating the concrete and soil compound target are studied. The deformation process and failure zone in the target are described by numerical simulation with finite element software. The results show that penetration depth, residual velocity and deceleration amplitude of flat-nose projectile increase with initial velocity. The features of concrete target after impact are approximately in agreement with experimental results. And the cracks and the tensile crush zone formed during penetration could characterize the damage and failure of target. Meanwhile, terminal ballistic characteristics of flat-nose projectile into single soil layer are studied to compare with that of concrete compound target. The results show that the overload of projectile penetrating hard-soil is only one-third of that of concrete compound target with low velocity. Reversely, the duration of the former is more than five times as long as the latter, and the rebound velocity of projectile penetrating soil medium is greater than the concrete compound target.

The peristaltic transport of Casson fluid in a channel and also in an inclined tube is analyzed mathematically, using long wavelength approximation and low Reynolds number assumption. The expressions for the velocity, stream function, flow rate, pressure rise and frictional force at the wall are obtained. It is found that the pressure rise decreases with the increase of the time mean flow rate and angle of inclination and increases with the increase of stress ratio and amplitude ratio. It is also noticed that the frictional force increases with the increase of the stress ratio and decreases with the increase of the angle of inclination. The estimates of the increase in the pressure rise are higher in channel flow compared to that of the inclined tube flow and the estimates of the increase in the frictional force are higher in inclined tube flow compared to that of the channel flow.

The mass loss of the nose of projectile is an obvious phenomenon in high-speed penetration into concrete target. The mass loss percentage depends linearly on the impact velocities of projectile according to experimental data fitting results. A semi-empirical model, which can calculate the ogive-nose shape change due to mass loss, is developed in this paper. The modified penetration model shows that the penetration depth is influenced by nose erosion.

This paper considers a theoretical study on steady incompressible flow of third grade fluid in helical screw rheometer (HSR) with zero flight angles (a vertical concentric annulus). The developed second order non linear coupled differential equations are solved by homotopy perturbation method. Expressions for torsional and longitudinal velocity components are derived. The effects of non-Newtonian parameter β on the velocity profiles are also presented through graphs. It is observed that the velocity profiles are strongly depending upon the Non-Newtonian parameter β .

The paper analysis the incorporation of the source term in the advection-diffusion equation for the BGK Lattice Boltzmann Method (LBM). The problem is the coupled energy and species conservation equations with the Soret term. The problem is extremely important for people using LBM in simulating multi-physics, because multi-physics effect added as a source term to LB. A Few BGK LBM models were used, namely D1Q2, D1Q3, D2Q4 and D2Q5 to solve advection-diffusion-reaction problems. The aim of this work is to demonstrate that the lattice Boltzmann method is able to simulate Soret effect, where the source term is the curvature of the temperature field. Theoretical analysis of the force inclusion is also presented in the paper. To insure that the predictions are correct and consistent with the traditional methods, comparison of LBM predictions with the finite difference method (FVM) predictions were illustrated. Also, the results show that prediction of D1Q2 may suffer from oscillation.

Basic assumptions are introduced into a homogenization theory which is described in the form of elliptic differential equations with a small parameter. Homogenization operators are used to solve the equations by asymptotic expansion methods, and error estimates of homogenization solutions are given.

In this paper, we have investigated the complex dynamics of a one-dimensional spatial nonlinear coupled reaction-diffusion system with a Holling type IV functional response, akin to standard Michaelis-Menten inhibitory kinetics. Prey-taxis is included in a general reaction-diffusion equation to incorporate the active movement of predator species towards regions with high prey concentrations or if the predator is following some sort of cue (such as odor) to find the prey. We have carried out stability analysis of both the non-spatial model without diffusive spreading and of the spatial model. We performed extensive computer simulations to identify various parameter ranges for stable homogeneous solution. Our findings specifically elucidate the role of predator diffusion and prey-taxis in controlling emergent structures, and transitions towards spatio-temporal chaos. We observe that the increasing predator random movement and moderate value of prey-taxis stabilize the system.