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Impact of conical tungsten projectiles on flat silicon carbide targets: Transition from interface defeat to penetration
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.
2006 (English)In: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 32, no 11, 1842-1856 p.Article in journal (Refereed) Published
Abstract [en]

Normal impact of conical tungsten projectiles on flat silicon carbide targets was studied experimentally and numerically for half apex angles 5° and 5–15°, respectively, and comparisons were made with cylindrical projectiles. A 30 mm powder gun and two 150 kV and four 450 kV X-ray flashes were used in the impact tests. The numerical simulations were run with the Autodyn code in two steps. In the first, the surface loads were determined for different impact velocities under assumed condition of interface defeat. In the second, these surface loads were applied to the targets in order to obtain critical states of damage and failure related to the transition between interface defeat and penetration, and the corresponding critical velocities. In the impact tests, interface defeat occurred below a transition velocity, which was significantly lower for the conical than for the cylindrical projectiles. Above the transition velocity, the initial penetration of conical projectiles differed markedly from that usually observed for cylindrical projectiles. It occurred along a cone-shaped surface crack, qualitatively corresponding to surface failure observed in the simulations. The transition velocity for the conical projectile was found to be close to the critical velocity associated with this surface failure.

Place, publisher, year, edition, pages
2006. Vol. 32, no 11, 1842-1856 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-92322DOI: 10.1016/j.ijimpeng.2005.04.004OAI: oai:DiVA.org:uu-92322DiVA: diva2:165352
Available from: 2004-11-03 Created: 2004-11-03 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Interface Defeat and Penetration: Two Modes of Interaction between Metallic Projectiles and Ceramic Targets
Open this publication in new window or tab >>Interface Defeat and Penetration: Two Modes of Interaction between Metallic Projectiles and Ceramic Targets
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ceramics constitute an important group of low-density armour materials. Their high intrinsic strength makes it possible to design ceramic armour systems capable of defeating projectiles directly on the ceramic surface. This capability, named interface defeat, signifies that the projectile material is forced to flow radially outwards on the surface of the ceramic without penetrating significantly.

This thesis presents impact experiments between long-rod projectiles and ceramic targets. The projectile/target interaction was studied using flash X-ray technique. Transition velocities (the impact velocity at which interface defeat can no longer be maintained and penetration starts) were estimated for different combinations of metallic projectiles and ceramic targets and compared to critical velocities estimated on a theoretical basis. Replica scaling experiments were also performed in order to investigate the possible influence of scale.

All ceramic materials tested showed a distinct transition from interface defeat to penetration. Experiments with different silicon carbides showed that the transition velocity correlated better with the fracture toughness than with the hardness of the ceramic materials. For conical projectiles, penetration occurred along a conical surface crack and at a lower transition velocity than that observed for cylindrical projectiles. Experiments with unconfined alumina targets in different scales showed only a slight increase in dimensionless final penetration with length scale.

A unique transition velocity seems to exist for each combination of projectile, target material and target configuration. This velocity was found to depend on both the strength (hardness) and the brittleness (fracture toughness) of the ceramic. The lower transition velocity of conical projectiles compared with cylindrical ones is mainly due to the radially expanding load and the penetration of projectile material into surface cracks. The results of the experiments in different scales indicate that replica scaling is valid for penetration in ceramics.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 53 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 1033
Keyword
Engineering physics, projectile, target, impact, interface defeat, penetration, tungsten, ceramic, replica scaling, Teknisk fysik
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:uu:diva-4641 (URN)91-554-6077-1 (ISBN)
Public defence
2004-12-03, Room 80121, The Ångström Laboratory, Lägerhyddsvägen 1, Polacksbacken, Uppsala, 10:00
Opponent
Supervisors
Available from: 2004-11-03 Created: 2004-11-03Bibliographically approved
2. 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
Supervisors
Available from: 2006-11-07 Created: 2006-11-07 Last updated: 2013-09-18Bibliographically approved

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