Semi-infinite Concrete Targets Research Articles

High Velocity Penetration of Concrete Targets with Eroding Long- Rod Projectiles; An Experiment and Analysis

This paper describes the design, analysis and experiments done to test eroding long-rod (9 ≤ L/d ≤ 11) penetration into semi-infinite concrete targets at high impact velocities (650 (m/s) < v0 < 1150 (m/s)). Furthermore, it studies the mechanical behavior of the projectile and semi-infinite concrete target at high velocity penetration. Test results showed similar qualities of eroding penetration in metal and concrete targets; therefore, it is possible to introduce models for studying eroding penetration in a semi-infinite concrete target using the basic equations used for evaluating penetration into metal targets. The experimental data on depths of penetration showed that the Forrestal model is inappropriate for studying eroding penetration in concrete targets; however these data are in good agreement with the results obtained from hydrodynamic theory. Therefore, it is recommended, that analytical study of eroding penetration in concrete targets takes account of necessary corrections relating to the special behavior of concrete when analytical models of penetration into metallic targets are used.

Numerical Analysis of Deformation and Failure of Penetration into Concrete Target by Projectile

Penetration is an important topic in the military and protection engineering field. Based on *MAT_PLASTIC_KINEMATIC of LS-DYNA program, this report studies effects of failure strain of the material parameters on structure of penetrating projectile. By establishing a group of numerical models about 45 steel hemispherical projectile penetrating semi-infinite concrete targets, this research aimed at analyzing effects of different failure strain values related to the destruction of the internal bracket structures of this projectile. At the same time, it studied the criterion of failure on finite dynamic program. The numerical results show that the use of failure strain in this model can well simulate damage of internal bracket structures of the projectile. Test was carried on based on this conclusion, which showed that bracket plate is subjected to shear failure in process of penetration, and numerical simulation was consistent with the experimental results.

The Deep Penetration of Concrete Targets by Rigid Rods - Revisited

The penetration of rigid long rods into semi-infinite concrete targets is revisited. In particular, we focus on the deceleration of these rods during their penetration, as inferred from the experimental data for penetration depths vs. impact velocities. We find that for a given concrete these decelerations are independent on impact velocity, which enables us to construct a simple relation between the penetration depth and impact velocity. Our model is different from the model which is based on the dynamic cavity expansion analysis to account for the resisting forces on the rod. The cavity expansion model has two terms for the resisting force, a strength term and an inertia term which depends on the velocity of the rod. In the present work we show that there is no physical basis for the inclusion of an inertia term and that the concrete's resisting force depends only on its strength, as with metallic targets. We demonstrate the validity of our approach by comparing its predictions with penetration depths from published data for different concrete and grout targets. We also find an empirical relation between the concrete's resisting stress and its unconfined compressive strength. Several important issues concerning target dimensions and the strength of the rod are discussed. These issues should be carefully considered as they influence the rigid nature of the rod and the semi-infinite condition of the target.

A fuzzy model of the penetration resistance of concrete targets

The penetration resistance of a concrete target varies greatly with the strike velocity of the projectile from low and intermediate impact velocities to high impact velocities. A fuzzy model of the penetration resistance of a concrete target is proposed to describe this characteristic. A complete analysis is conducted of the penetration process during which a rigid projectile penetrates a semi-infinite concrete target based on the proposed fuzzy model. Good agreement is observed between the experimental and predicted results based on the proposed fuzzy model.

A semi-empirical equation of penetration depth on concrete target impacted by ogive-nose projectiles

In this paper, the penetration process of ogive-nose projectiles into the semi-infinite concrete target is investigated by the dimensional analysis method and FEM simulation. With the dimensional analysis, main non-dimensional parameters which control the penetration depth are obtained with some reasonable hypothesis. Then, a new semi-empirical equation is present based on the original work of Forrestal et al., has only two non-dimensional combined variables with definite physical meanings. To verify this equation, prediction results are compared with experiments in a wide variation region of velocity. Then, a commercial FEM code, LS-DYNA, is used to simulate the complex penetration process, that also show the novel semi-empirical equation is reasonable for determining the penetration depth in a concrete target.

Use of flash X-radiography to observe ejecta from shaped charge penetrators in concrete

This paper describes the use of Flash X-Radiography for imaging the ejecta cloud from a small-scale shaped charge jet impacting a semi-infinite concrete target. The aim is to understand the timescale and extent of the ejecta as well as measuring the general velocity field. This provides useful additional information for validating material and fracture models used in simulations. The technique required the novel use of the X-ray equipment, since it was necessary to image the ejecta cloud in a region just above the surface of the concrete target and to take two images very close together, to allow a reasonably accurate velocity measurement. Also the extent of the ejecta cloud was important in terms of determining whether it originated from the borehole or as a result of the surface spallation leading to crater formation. Various techniques of target doping were used and these had varying degrees of success since the doping method could also affect the borehole formation. These were compounded by limits in the resolution of the equipment. General results are presented and recommendations made for developing this promising technique further.

Penetration into concrete by truncated projectiles

In this paper, the penetration into semi-infinite concrete targets by rigid truncated projectiles is examined. The semi-analytical cavity expansion based penetration formula in Forrestal et al. (Int. J. Impact Eng. 15(4) (1994) 395) and Frew et al. (Int. J. Impact Eng. 21(6) (1998) 489) for ogive-nosed projectiles has earlier been seen to give good agreement with experiments. In Lixin et al. (Int. J. Impact Eng. 24 (2000) 947), this model was extended to truncated-nosed projectiles by introducing two additional empirical constants. In the present paper, Forrestal's approach is expanded to include a larger class of projectile nose geometries, especially flat and truncated noses. The new theory presented here introduces no new empirical constants, and is seen to agree very well with the available experimental data.

A semi-analytical model for truncated-ogive-nose projectiles penetration into semi-infinite concrete targets

The study on the truncated-ogive-nose projectile penetration into semi-infinite concrete targets is described in this paper. With reference to Forrestal's force model of ogive-nose projectile, semi-analytical penetration equations are developed by introducing a resistance constant which takes into account the truncation effect of the ogive-nose projectile on penetration. The semi-analytical model is shown to be in good correlation with limited recently published experimental results.

A method for scaling ballistic penetration phenomena

There are several established formulae for projectile penetration into semi-infinite concrete targets. Most of them include a term which indicates that regular scaling does not hold in this situation. Most of these formulae were derived using curve-fitting procedures, so that these terms do not represent any physical meaning. Non-scaling is also found in long rod penetrations, which cannot be attributed to strain rate effects. It is suggested here to differentiate the energy spent by the projectile during the penetration process into two parts, one—the energy expended for surface effects and the other—the energy expended for volume effects. By doing so, it is possible to derive expressions which account for the irregularity in scaling. These expressions are derived from the global, energy balance point of view, so they do not require the detailed characterization of the materials involved. They only require strict adherence to replica scaling procedures. A similar approach is used to account for strain rate effects, but in that case, the results are not as general and can be applied only to a narrow span of configurations. Examples are cited from tests with concrete penetration and long rod penetration into different targets.