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Stationary contact between a cylindrical metallic projectile and a flat target surface under conditions of dwell
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid Mechanics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid Mechanics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid Mechanics.
2004 (English)In: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 30, no 6, 1265-1282 p.Article in journal (Refereed) Published
Abstract [en]

Armour systems capable of defeating an incoming projectile on the surface of a ceramic target have been reported. This capability, called interface defeat or dwell, signifies that the projectile material is forced to flow radially on the surface of the target without penetrating significantly. Under such flow conditions, the hydrodynamic pressure is normally the most important part of the normal load on the target surface. Therefore, projectile properties such as yield strength and compressibility are commonly ignored or assumed to contribute only marginally. In order to investigate the effects of these properties, an analytical expression was derived for the normal load from a cylindrical metallic projectile impacting on a flat, rigid and friction-free surface, which includes the contributions from yield strength and compressibility in addition to that of inertia. At an impact velocity representative of today's ordinance velocities, the contributions to load intensity on the axis from yield strength and compressibility were found to be 15% and 3.4%, respectively, of that of inertia. The analytical results and Autodyn-2D numerical simulations show good agreement within a projectile radius from the axis.

Place, publisher, year, edition, pages
2004. Vol. 30, no 6, 1265-1282 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-95106DOI: 10.1016/j.ijimpeng.2003.09.001OAI: oai:DiVA.org:uu-95106DiVA: diva2:169192
Available from: 2006-11-07 Created: 2006-11-07 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Impact of Metallic Projectiles on a Ceramic Target Surface: Transition Between Interface Defeat and Penetration
Open this publication in new window or tab >>Impact of Metallic Projectiles on a Ceramic Target Surface: Transition Between Interface Defeat and Penetration
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The purpose of this thesis is to gain understanding of the load on flat target surfaces produced by projectile impact. Models are proposed from which upper and lower bounds can be derived for the transition be-tween interface defeat and normal penetration.

It is shown that the dominating contribution to the normal load is generally provided by the hydrodynamic pressure due to the effect of inertia. In addition it is shown that the contributions from yield strength and compressibility are also significant. For a cylindrical tungsten alloy projectile at an impact velocity representative of to-day’s ordnance velocities, the contributions to the load intensity on the axis of symmetry from yield strength and compressibility are shown to be 15% and 3.4%, respectively, of that of inertia.

Impact tests have shown that for conical projectiles transition from interface defeat to penetration occurs at a significantly lower impact velocity than for cylindrical projectiles. In order to better understand the influence of projectile shape, a conical projectile in axi-symmetric impact is studied by use of an analytical model for self-similar flow, and the results obtained are compared to results of numerical simula-tions. It is shown how the maximum load intensity, and the position of the maximum, depends on the apex angle. For an apex angle of 90º, the maximum load intensity is found to be almost three times that pro-duced by a cylindrical projectile with the same impact velocity. This maximum occurs well off the axis of symmetry and is 20% larger than the load intensity at this axis. Both the self-similar model and the nu-merical simulations show that the contribution to the load intensity from compressibility is positive below and negative above an apex angle of around 80º. The contribution of yield strength to the load in-tensity at centre of impact depends only weakly on the apex angle and is therefore similar to that of a cylindrical projectile.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 37 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 238
Keyword
Engineering physics, Projectile, Cylindrical, Conical, Yield strength, Compressibility, Perfect flow, Self-similar flow, Interface defeat, Dwell, Teknisk fysik
Research subject
Engineering Science with specialization in Solid Mechanics
Identifiers
urn:nbn:se:uu:diva-7264 (URN)91-554-6712-1 (ISBN)
Public defence
2006-12-07, Polhemssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:00 (English)
Opponent
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Available from: 2006-11-07 Created: 2006-11-07 Last updated: 2013-09-18Bibliographically approved

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Lundberg, Bengt

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