Simulation and experimental validation of the dynamic pressure of shock wave under free-field blast loading

Shock wave energy generated by a blast can cause severe damage to buildings, as well as result in the loss of lives and properties. As explosive becomes increasingly powerful, the damaging effects generated by blast waves have become a weapon, not only on the battle field. Even explosions of gas utilized in various industries can be a source of great threat and destruction. Therefore, the study of the blast stress wave under the dynamic loading effect of an explosion is a subject to be carefully considered before construction planning and design, and research in this field is urgently needed. This study adopts the methods of field blasting experiment and numerical simulation analysis to analyze the shock wave energy and its attenuation characteristics by comparing the experimental results with data from the numerical simulation. The numerical analysis utilizes the Arbitrary Lagrangian-Eulerian algorithm with a 3-dimensional (3D) solid structural model and 8-node solid elements. The results show an increasing trend for blast pressure as the amount of explosive increases. With the same amount of explosive, the blast pressure extreme shows a decreasing trend as the distance from the blast center increases. The results of this study can facilitate accurate analysis of shock wave energy of a blast, assess its destructive power and provide references for the calculation of blast safe quantity-distance for the human body, as well as for the planning of building safety zones, facility shock absorption measures and disaster prevention, in order to reduce the potential danger of blast waves and ensure the safety of human lives and properties

Numerical simulation and experimental validation of the Mach reflection effect of shock wave under ground surface blast

The hazard of a shock wave is an important consideration in blasting engineering design. The scope of effect and extent of damage caused by a shock wave depends on its energy. In addition to the blasting pressure and the horizontal distance to the blast center, the Mach effect caused by the ground surface reflection is also an important factor in the analysis of the transmission pattern of a shock wave. Therefore, the purposes of this study were to investigate the characteristics of the shock wave effect induced by a surface contact blast, and to analyze the energy attenuation pattern, as well as the impact distances where the Mach reflection effect might occur. To accomplish the purposes, this study conducted 0.5 lb TNT explosive field blasting experiments and numerical simulation analyses. Experimental results and data from the numerical simulation were compared with each other to analyze the shock wave transmission and Mach wave effect. The numerical analysis used an Arbitrary Lagrangian-Eulerian (ALE) algorithm and fluid-solid interaction method, with eight-node solid elements and three-dimensional solid structural model to conduct the analysis. Results of this study will enable more accurate and practical assessments of blasting effects, and provide references for future construction planning, facility shock-absorption and disaster prevention design, in order to reduce potential shock wave hazards and ensure facility safety protection, as well as a secure building safe zone

Numerical analysis and experimental measurements of the ground vibration characteristics caused by shallow underground explosion

Studies of shock waves from explosions involve the dynamic analysis of geometric, material, and contact nonlinearities. The action of the shock wave on soil (pressurization and decompression) is completed within milliseconds. The energy transfer process of shock waves has a significant impact on engineering structures; an analyst evaluating the effectiveness of safety measures must first understand the dynamic characteristics of this energy transfer. Thus, examining the movement patterns of the media through which shock waves travel is of primary concern. Construction designs must consider the propagation characteristics of shock waves in soil. In this study, the finite element method was employed to analyze the dynamic and mechanical behavior of soil by applying the multi-material arbitrary Lagrangian-Eulerian algorithm to a 3D solid element with eight nodes and six faces. A structural model of the fluid-solid coupling was constructed to examine the shock wave propagation process resulting from shallow underground explosions. In addition, ground surface acceleration values obtained from field tests were used to validate results of the numerical analysis of time- and space-dependent shock wave propagation and attenuation in soil. The objective of this study was to perform a rational analysis of the seismic effects of shallow underground explosions to provide a reference for earthquake engineering

Numerical and experimental verification of finite element mesh convergence under explosion loading

Explosions inflict severe damage to building structures and threaten national security as well as social stability; their scope of impact and damage level is subject to the energy contained in the shock waves. Explosion testing is limited by the test site and amount of explosive used; a large scale explosion test is not viable. Therefore, numeric analysis is adopted as the preferred research method instead of an actual field test. The application of finite element analysis requires consideration of the complexity of an analysis model and the mesh density. An explosive load violent enough to cause distortion to mesh cannot reveal the actual mechanical behavior and will compromise the convergence and accuracy of the results. The purpose of this study is to analyze the optimal mesh density of the finite elements under an explosive load, in order to explore the element mesh convergence and to compare the results with the experimental. The results of this study can reasonably simulate an explosion effect, achieve the convergence as indicated by calculation results, and provide a foundation upon which future dynamic mechanic studies may establish numerical models. To enhance the calculation accuracy, this study adopts a fluid dynamic analysis program, LS-DYNA, finite element analysis software, to conduct Fluid-Solid Interaction (FSI). A TNT free-field explosion simulation is analyzed for mesh density convergence under an explosive load. The analysis results reveal a pattern where the shock wave diminishes as it moves further away from the explosion point. The results may serve as reference for studies involving the numeric analysis of explosions

Influence of concave groove on transmission of blasting vibration wave

With the extensive application of blasting techniques, the prediction and hazard control of explosion-induced vibration is an important issue which cannot be ignored in blasting engineering. A numerical approach is presented to study the explosion-induced pressure load on the surface of C-4 explosives in a semi-infinite space, in order to explore the effectiveness of concave grooves in ground vibration wave barrier. Numerical simulations are carried out by using a widely applied explicit dynamic nonlinear finite element software LS-DYNA and adopted the Arbitrary Lagrangian-Eulerian method for numerical analysis to simulate the propagation of blast waves. The analysis shows that the concave grooves have a significant effect on attenuating the propagation of detonation waves. The vibration control is related to the width and depth of the groove, and the impact of the depth is greater than that of the width. This study can be used as a reference in hazard control of explosion-induced vibration

A general relativistic model for the light propagation in the gravitational field of the Solar System: the dynamical case

Modern astrometry is based on angular measurements at the micro-arcsecond level. At this accuracy a fully general relativistic treatment of the data reduction is required. This paper concludes a series of articles dedicated to the problem of relativistic light propagation, presenting the final microarcsecond version of a relativistic astrometric model which enable us to trace back the light path to its emitting source throughout the non-stationary gravity field of the moving bodies in the Solar System. The previous model is used as test-bed for numerical comparisons to the present one. Here we also test different versions of the computer code implementing the model at different levels of complexity to start exploring the best trade-off between numerical efficiency and the micro-arcsecond accuracy needed to be reached.Comment: 40 pages, 5 figures. Accepted for publication on The Astrophysical Journal. Manuscript prepared with AASLaTeX macros v.5.

Analysis of blast-induced ground vibration under surface explosion

The blasting operation is vital in the construction of tunnels and channels or in mining when encountering hard geological environments to facilitate the progress of a project. The level and range of damage due to the blast are affected by the energy of shock waves generated after explosion. The control of seismic damage is a major issue in blasting engineering and cannot be neglected. The stratum layer or buildings on the earth’s surface can be damaged when blasting-induced vibration strength exceeds the allowed range. In order to reduce the degree of damage, the patterns of blasting vibration must be studied and controlled. Therefore, the propagation characteristics of shock waves on the earth’s surface are important factors to be studied before the planning and designing of a project. This paper adopted a mutual verification method between the blasting experiment and numerical analysis results for verifying the reliability of numerical simulation based on experimental data. The numerical analysis method analyzed the dynamic mechanical behavior of blasting vibration using the finite element method. The LS-DYNA program was used to simulate TNT explosive and surface contact blasting in semi-infinite space and in propagation of the resulting seismic waves. The propagation characteristics, represented by temporal and spatial changes of surface acceleration, were investigated. The analysis results showed that post-explosion dynamic characteristics of the earth’s surface simulated by finite element method yielded promising simulation results. In addition, the propagation characteristics of stress waves were observed from the dynamic mechanical behavior of surface acceleration after explosion. That is, the maximum main stress presented a pattern of progressive attenuation with increasing distance from the blasting source. The results are able to provide reference for the protection of engineering structures from blasting vibration damages

Numerical analysis and experimental measurements of the ground vibration characteristics caused by shallow underground explosion

Studies of shock waves from explosions involve the dynamic analysis of geometric, material, and contact nonlinearities. The action of the shock wave on soil (pressurization and decompression) is completed within milliseconds. The energy transfer process of shock waves has a significant impact on engineering structures; an analyst evaluating the effectiveness of safety measures must first understand the dynamic characteristics of this energy transfer. Thus, examining the movement patterns of the media through which shock waves travel is of primary concern. Construction designs must consider the propagation characteristics of shock waves in soil. In this study, the finite element method was employed to analyze the dynamic and mechanical behavior of soil by applying the multi-material arbitrary Lagrangian-Eulerian algorithm to a 3D solid element with eight nodes and six faces. A structural model of the fluid-solid coupling was constructed to examine the shock wave propagation process resulting from shallow underground explosions. In addition, ground surface acceleration values obtained from field tests were used to validate results of the numerical analysis of time- and space-dependent shock wave propagation and attenuation in soil. The objective of this study was to perform a rational analysis of the seismic effects of shallow underground explosions to provide a reference for earthquake engineering

Nonlinear dynamic response and deformation analysis of soil under the explosion shock loading

Energy is released during explosions, and this creates shock waves. The dynamic pressure generated from an explosion is transmitted through soil in the form of compression waves. In military engineering and industrial safety protection, soil, a blast-resistant material, is used to achieve blast resistance. This study used the blast pressure and ground acceleration measured in an experimental explosion to verify the results of finite element numerical analysis. A fluid–solid interaction numerical analysis method was employed to simulate a trinitrotoluene explosion on the ground. Through analysis of the dynamic characteristics of soil after an explosion, the relationship between the dynamic stress wave formed by the explosion and the plastic deformation of the soil was studied. The results may provide a reference for the design of blast-resistant protective soil layers

The second US Naval Observatory CCD Astrograph Catalog (UCAC2)

The second USNO CCD Astrograph Catalog, UCAC2 was released in July 2003. Positions and proper motions for 48,330,571 sources (mostly stars) are available on 3 CDs, supplemented with 2MASS photometry for 99.5% of the sources. The catalog covers the sky area from -90 to +40 degrees declination, going up to +52 in some areas; this completely supersedes the UCAC1 released in 2001. Current epoch positions are obtained from observations with the USNO 8-inch Twin Astrograph equipped with a 4k CCD camera. The precision of the positions are 15 to 70 mas, depending on magnitude, with estimated systematic errors of 10 mas or below. Proper motions are derived by utilizing over 140 ground-and space-based catalogs, including Hipparcos/Tycho, the AC2000.2, as well as yet unpublished re-measures of the AGK2 plates and scans from the NPM and SPM plates. Proper motion errors are about 1 to 3 mas/yr for stars to 12th magnitude, and about 4 to 7 mas/yr for fainter stars to 16th magnitude. The observational data, astrometric reductions, results, and important information for the users of this catalog are presented.Comment: accepted by AJ, AAS LaTeX, 14 figures, 10 table