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Interface Defeat and Penetration: Two Modes of Interaction between Metallic Projectiles and Ceramic Targets
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences.
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. , p. 53
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 1033
Keywords [en]
Engineering physics, projectile, target, impact, interface defeat, penetration, tungsten, ceramic, replica scaling
Keywords [sv]
Teknisk fysik
National Category
Other Engineering and Technologies
Identifiers
URN: urn:nbn:se:uu:diva-4641ISBN: 91-554-6077-1 (print)OAI: oai:DiVA.org:uu-4641DiVA, id: diva2:165353
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
List of papers
1. Influence of scale on the penetration of tungsten rods into steel-backed alumina targets
Open this publication in new window or tab >>Influence of scale on the penetration of tungsten rods into steel-backed alumina targets
1996 (English)In: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 18, no 4, p. 403-416Article in journal (Refereed) Published
Abstract [en]

As ballistic tests are often performed in reduced geometrical scale, the scaling laws are important for the interpretation of the results. In this study, we tested the validity of replica scaling, by which we mean that all geometrical dimensions are scaled uniformly, while the materials and the impact velocity are kept the same. Long tungsten projectiles with length-to-diameter ratio 15 were fired against unconfined alumina targets with steel backing. The tests were carried out with impact velocities 1500 m s−1 and 2500 m s−1, and in three different scales with projectile lengths 30, 75 and 150 mm (diameters 2, 5 and 10 mm). The alumina targets were photographed by means of a high-speed camera, and the tungsten projectiles were photographed inside the alumina targets by means of flash radiography. Also, the residual penetrations in the steel backings were measured. The Johnson-Holmquist model for ceramic materials was implemented into the AUTODYN code, which was used for simulation of the experiments. The agreement between results of experiment and simulation was fair, and over the tested interval of scales replica scaling was found to be valid with reasonable accuracy.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-92318 (URN)10.1016/0734-743X(95)00049-G (DOI)
Available from: 2004-11-03 Created: 2004-11-03 Last updated: 2017-12-14Bibliographically approved
2. Impact of metallic projectiles on ceramic targets: transition between interface defeat and penetration
Open this publication in new window or tab >>Impact of metallic projectiles on ceramic targets: transition between interface defeat and penetration
2000 (English)In: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 24, no 3, p. 259-275Article in journal (Refereed) Published
Abstract [en]

Armour systems capable of defeating an incoming projectile on the surface of a ceramic have been reported by several authors. This capability, called interface defeat, signifies that the projectile material is forced to flow radially outwards on the surface of the ceramic without penetrating significantly. In order to investigate the conditions for interface defeat, two models for the interaction of a metallic projectile and a ceramic target were established. With the aid of them, upper and lower bounds for the transition impact velocity between interface defeat and normal penetration were estimated for a given combination of metallic projectile and ceramic target. These approximate bounds were found to be consistent with transition velocities determined experimentally for two projectile materials (tungsten and molybdenum) and five target materials (two types of silicon carbide, boron carbide, titanium diboride and a polycrystalline diamond composite).

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-92319 (URN)10.1016/S0734-743X(99)00152-9 (DOI)
Available from: 2004-11-03 Created: 2004-11-03 Last updated: 2017-12-14Bibliographically approved
3. Tungsten long-rod penetration into confined cylinders of boron carbide at and above ordnance velocities
Open this publication in new window or tab >>Tungsten long-rod penetration into confined cylinders of boron carbide at and above ordnance velocities
2001 (English)In: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 25, no 7, p. 703-714Article in journal (Refereed) Published
Abstract [en]

The purpose was to investigate the influence of impact velocity and confinement on the resistance of boron carbide targets to the penetration of tungsten long-rod projectiles. Experimental tests with impact velocities from 1400 to 2600 m/s were performed using a two-stage light-gas gun and a reverse impact technique. The targets consisted of boron carbide cylinders confined by steel tubes of various thicknesses. Simulations were carried out using the AUTODYN-2D code and Johnson–Holmquist's constitutive model with and without damage evolution. The experimental results show that the penetration process had different character in three different regions. At low-impact velocities, no significant penetration occurred. At high-impact velocities, the relation between penetration velocity and impact velocity was approximately linear, and the penetration was steady and symmetrical. In between, there was a narrow transition region of impact velocities with intermittent and strongly variable penetration velocity. In the lower part of this region, extended lateral flow of the projectile took place on the surface of the target. The influence of confinement on penetration velocity was found to be small, especially at high-impact velocities. The simulated results for penetration velocity versus impact velocity agreed fairly well with the experimental results provided damage evolution was suspended below the transition region.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-92320 (URN)10.1016/S0734-743X(00)00072-5 (DOI)
Available from: 2004-11-03 Created: 2004-11-03 Last updated: 2017-12-14Bibliographically approved
4. Transition between interface defeat and penetration for tungsten projectiles and four silicon carbide materials
Open this publication in new window or tab >>Transition between interface defeat and penetration for tungsten projectiles and four silicon carbide materials
2005 (English)In: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 31, no 7, p. 781-792Article in journal (Refereed) Published
Abstract [en]

Armour systems containing high-quality ceramics may be capable of defeating armour-piercing projectiles on the surfaces of these hard materials. This capability, named interface defeat, has been studied for four different silicon carbide ceramic materials, viz., SiC–B, SiC–N, SiC–SC–1RN and SiC–HPN by use of a light-gas gun and a small-scale reverse impact technique. The velocities of a tungsten projectile marking the transition between interface defeat and penetration have been determined and compared with the Vickers hardness and fracture toughness of the ceramic materials. It is found that the transition velocity increases with the fracture toughness but not with the Vickers hardness. This indicates that, under the prevailing conditions, fracture may have had more influence than plastic flow on the transition. As a consequence, the observed transition velocities may not be the maximum ones achievable, at least not for SiC–B, SiC–N and SiC–SC–1RN. By suppression of the initiation and propagation of cracks through increase of the confining pressure, it may be possible to increase the transition velocities.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-92321 (URN)10.1016/j.ijimpeng.2004.06.003 (DOI)
Available from: 2004-11-03 Created: 2004-11-03 Last updated: 2017-12-14Bibliographically approved
5. Impact of conical tungsten projectiles on flat silicon carbide targets: Transition from interface defeat to penetration
Open this publication in new window or tab >>Impact of conical tungsten projectiles on flat silicon carbide targets: Transition from interface defeat to penetration
2006 (English)In: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 32, no 11, p. 1842-1856Article 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.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-92322 (URN)10.1016/j.ijimpeng.2005.04.004 (DOI)
Available from: 2004-11-03 Created: 2004-11-03 Last updated: 2017-12-14Bibliographically approved

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