Seismic Wave Field Model Excited by a Finite Long Cylindrical Charge

The amplitude-frequency characteristic of a seismic wave excited by explosion sources directly affects the accuracy of seismic exploration. To reveal the effect law related to a cylindrical charge, the research proposes a seismic wavefield model excited by a long cylindrical charge. According to the characteristics of the blasting cavity generated by a finite length cylindrical charge, the seismic wavefield characteristics of a cylindrical charge excitation is obtained by superposing the seismic wavefield excited by a series of spherical charges. Numerical simulation results show that the calculation error of the blasting cavity characteristics of the theoretical model is within 10%. The comparison with field experimental results shows that the error of the model is within 9.4%. The velocity field of the excited seismic wave is almost the same as that of the spherical charge when the explosion distance to the cylindrical charge with finite length is 16-21 times longer than the charge length, but the frequency of the seismic wave is 30% higher than for a spherical charge. Moreover, the explosive velocity has a certain influence on the amplitude-frequency characteristic of the seismic wave excited by the cylindrical charge. The established theoretical model can accurately describe the amplitude-frequency characteristics of the seismic wavefield excited by a cylindrical charge with finite length.

Shock Wave Propagation Characteristics of Cylindrical Charge and Its Aspect Ratio Effects on the Damage of RC Slabs

Antiknock research of reinforced concrete (RC) slabs is often carried out with spherical or nearly spherical explosives, although many explosives used in engineering and military are cylinder shaped. It is known that the shock wave caused by cylindrical explosives varies in different directions, which is quite different from the spherical charge. In this paper, the shock wave propagation characteristics of spherical and cylindrical explosives with different aspect ratios are compared and analyzed. The 2D numerical results show the peak overpressure from the cylindrical explosive is significantly affected by the L/D (length/diameter) ratio. Subsequently, the damage features of RC slabs under spherical and cylindrical explosives with a certain L/D ratio are investigated through an explosion experiment. Finally, the influence of the L/D ratio on the dynamic response of RC slabs under cylindrical explosives is studied by the fully coupled Euler–Lagrange method. The accuracy and reliability of the coupled model are verified by comparing the numerical with experimental results. Based on the experimental and numerical studies, it can be concluded that the explosive shape directly determines the shape of upper surface crater damage, and the spall damage area of RC slabs becomes larger as the L/D increases. For the L/D increases to a certain value, the cylindrical explosive will induce larger spall damage than that induced by spherical charge with the same amount of explosives. Hence, the effect of the cylindrical charge should be considered in the antiknock design of the RC structure.

Magnetic dipole moments of the hidden-charm pentaquark states: $$P_c(4440)$$, $$P_c(4457)$$ and $$P_{cs}(4459)$$

In this work, we employ the light-cone QCD sum rule to calculate the magnetic dipole moments of the $$P_c(4440)$$ P c ( 4440 ) , $$P_c(4457)$$ P c ( 4457 ) and $$P_{cs}(4459)$$ P cs ( 4459 ) pentaquark states by considering them as the diquark–diquark–antiquark and molecular pictures with quantum numbers $$J^P = \frac{3}{2}^-$$ J P = 3 2 - , $$J^P = \frac{1}{2}^-$$ J P = 1 2 - and $$J^P = \frac{1}{2}^-$$ J P = 1 2 - , respectively. In the analyses, we use the diquark–diquark–antiquark and molecular form of interpolating currents, and photon distribution amplitudes to obtain the magnetic dipole moment of pentaquark states. Theoretical examinations on magnetic dipole moments of the hidden-charm pentaquark states, are essential as their results can help us better figure out their substructure and the dynamics of the QCD as the theory of the strong interaction. As a by product, we extract the electric quadrupole and magnetic octupole moments of the $$P_c(4440)$$ P c ( 4440 ) pentaquark. These values show a non-spherical charge distribution.

Validation of the pressure wave model in the aspect of special structures endurance

The article presents results of the research on the validation of impact wave in the aspect of special structures’ endurance. Impact waves have been examined according to numerical and analytical methods. In order to verify the results obtained, a workstation for experimental research had been prepared. Before conducting the experiment, approximate pressure value had been checked empirically. The pressure had been measured using sensors for free wave measurements. The topic of the paper is empirical examination of the phenomenon of explosion in the aspect of the free wave pressure. Due to a difficulty of the issue, it was necessary to conduct complex examination of the phenomenon for various charges. The paper examines cases of spherical charge explosions with a balanced mass of 1 kg TNT.

Influence of Charges Shape on a Closely Air Blast Loading

The purpose of the present paper is to investigate the influence of charge shape on the air blast loading near the explosive. By using MSC. DYTRAN, the air blast loading of spherical charge, cubical charge and cylindrical charge with the same weight were simulated. After the characters of shock wave, peak pressure and impulse of such three charges were compared, it can be seen that there are different decay law for peak pressure of cylindrical charge, cubical charge, spherical and experiment formula. There are also different magnitude relation for the impulse at different scaling distance.

Analysis of the Dynamic Response of a Controlled Detonation Chamber

Detonation chambers (either mobile or fixed) are used worldwide for a wide range of applications. At present, a 1/7 scale model of a 1 ton detonation chamber is available for extended testing in Belgium. The chamber is a single wall cylindrical vessel with semielliptical ends. Each time an explosive charge is fired in the vessel, that vessel is submitted to a number of deformation cycles. A series of strain gauges measures the deformation of the vessel walls. Experimental peak strains and vibration frequency can be compared with predicted values based on simple formulas. Measured values are reasonably close to the estimated values. The influence of the shape of the charge is studied. The shape has an important influence on the chamber response. For a fixed charge mass, a spherical charge causes less deformation than a cylindrical charge and is therefore advantageous from a fatigue point of view.