MEASUREMENTS OF CHARACTERISTICS FOR FRAGMENTATION – BURSTING HEADS

The paper deals with questions appearing at investigation of high explosive-fragmentation heads of medium calibre when the blast waves (BW) generated by the flying fragments affect the results of velocity of the BW generated by the head itself (HBW). A method used by the authors for protection of measurement sensors against destructive action of the fragments is described. Distribution of produced fragments regarding the sizes and in function of scattering angle was studied. Mean velocity of highest speed (2100 m/s) fragments was measured on the base of first 10 m. Distribution of HBW velocities in function of radius of propagation was measured.

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Blast Wall Shielding Effectiveness

Volume 4: Fluid-Structure Interaction ◽

10.1115/pvp2017-65187 ◽

2017 ◽

Author(s):

Jihui Geng ◽

J. Kelly Thomas

Keyword(s):

Blast Wave ◽

High Explosive ◽

Blast Loading ◽

Blast Waves ◽

Shielding Effectiveness ◽

Wave Shape ◽

Mitigation Option ◽

Blast Damage ◽

Wave Parameters ◽

Vapor Cloud

Blast walls are frequently considered as a potential mitigation option to reduce the applied blast loading on a building or structure in cases where unacceptably high levels of blast damage are predicted. There are three general explosion types of interest with respect to blast loading: High Explosive (HE), Pressure Vessel Burst (PVB), and Vapor Cloud Explosion (VCE). The blast waves resulting from these explosion types can differ significantly in terms of blast wave shape and duration. The effectiveness of a blast wall depends on these blast wave parameters (shape and duration), as well as the blast wall parameters (e.g., height, width and standoff distance from the protected structure). The effectiveness of a blast wall in terms of mitigating the blast loading on a protected structure depends on the combination of the blast wave and blast wall parameters. However, little guidance is available on the effectiveness of blast walls as a mitigation option for non-HE explosion sources. The purpose of this paper is to characterize the effect of blast wave parameters on the effectiveness of a blast wall and to provide guidance on how to determine whether a blast wall is an effective and practical blast damage mitigation option for a given blast loading.

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Numerical investigation of a new structural configuration of a concrete barrier wall under the effect of blast loads

International Journal of Advanced Structural Engineering ◽

10.1007/s40091-019-00252-8 ◽

2019 ◽

Vol 11 (S1) ◽

pp. 19-34

Author(s):

Ahmed K. Taha ◽

Zhengguo Gao ◽

Dahai Huang ◽

M. S. Zahran

Keyword(s):

High Explosive ◽

Numerical Models ◽

Three Dimensional ◽

Experimental Tests ◽

Blast Waves ◽

Convex Curve ◽

Structural Configuration ◽

Explosive Material ◽

Concrete Wall ◽

Concrete Barrier

AbstractIn this study, a non-linear three-dimensional hydrocode numerical simulation was carried out using AUTODYN-3D, which is an extensive code dealing with explosion problems. A high explosive material (comp-B) is blasted against several concrete wall barriers. The model was first validated using referenced experimental tests and has shown good results. Several numerical models were carried out to study the effect of changing the shape of wall barrier from flat to convex curve and concave curve, and also investigated the effect of changing the angle of curvature. The results showed that changing the shape of a wall barrier from flat to convex curve has the best performance in mitigating the effect of blast waves. It is also concluded that convex walls with 60° angle of curvature have the best performance compared to other barrier walls.

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Scattering-angle dependence of signal/background ratio of inner-shell electron excitation loss in EELS

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100075701 ◽

1983 ◽

Vol 41 ◽

pp. 390-391

Author(s):

T. Oikawa ◽

M. Inoue ◽

T. Honda ◽

Y. Kokubo

Keyword(s):

Energy Loss ◽

Electron Excitation ◽

Heavy Elements ◽

Background Intensity ◽

Light Elements ◽

Energy Analyzer ◽

High Background ◽

Scattering Angle ◽

Angle Dependence ◽

Shell Electron

EELS allows us to make analysis of light elements such as hydrogen to heavy elements of microareas on the specimen. In energy loss spectra, however, elemental signals ride on a high background; therefore, the signal/background (S/B) ratio is very low in EELS. A technique which collects the center beam axial-symmetrically in the scattering angle is generally used to obtain high total intensity. However, the technique collects high background intensity together with elemental signals; therefore, the technique does not improve the S/B ratio. This report presents the experimental results of the S/B ratio measured as a function of the scattering angle and shows the possibility of the S/B ratio being improved in the high scattering angle range.Energy loss spectra have been measured using a JEM-200CX TEM with an energy analyzer ASEA3 at 200 kV.Fig.l shows a typical K-shell electron excitation edge riding on background in an energy loss spectrum.

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Analytic integration of contrast transfer functions

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010010617x ◽

1988 ◽

Vol 46 ◽

pp. 822-823

Author(s):

Peter Rez

Keyword(s):

Wave Function ◽

Transfer Function ◽

Transfer Functions ◽

Spherical Aberration ◽

Continuous Distribution ◽

Objective Lens ◽

Direction Parallel ◽

Scattering Angle ◽

Analytic Integration ◽

Image Position

In high resolution microscopy the image amplitude is given by the convolution of the specimen exit surface wave function and the microscope objective lens transfer function. This is usually done by multiplying the wave function and the transfer function in reciprocal space and integrating over the effective aperture. For very thin specimens the scattering can be represented by a weak phase object and the amplitude observed in the image plane is1where fe (Θ) is the electron scattering factor, r is a postition variable, Θ a scattering angle and x(Θ) the lens transfer function. x(Θ) is given by2where Cs is the objective lens spherical aberration coefficient, the wavelength, and f the defocus.We shall consider one dimensional scattering that might arise from a cross sectional specimen containing disordered planes of a heavy element stacked in a regular sequence among planes of lighter elements. In a direction parallel to the disordered planes there will be a continuous distribution of scattering angle.

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