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Tungsten long-rod penetration into confined cylinders of boron carbide at and above ordnance velocities
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.
2001 (English)In: International Journal of Impact Engineering, ISSN 0734-743X, Vol. 25, no 7, 703-714 p.Article 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.

Place, publisher, year, edition, pages
2001. Vol. 25, no 7, 703-714 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-92320DOI: 10.1016/S0734-743X(00)00072-5OAI: oai:DiVA.org:uu-92320DiVA: diva2:165350
Available from: 2004-11-03 Created: 2004-11-03 Last updated: 2013-09-18Bibliographically 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. Interaction of Cylindrical Penetrators with Ceramic and Electromagnetic Armour
Open this publication in new window or tab >>Interaction of Cylindrical Penetrators with Ceramic and Electromagnetic Armour
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Växelverkan mellan cylindriska penetratorer och keramiska och elektromagnetiska pansar
Abstract [en]

Armoured vehicles have traditionally used steel armour as protection against penetrators such as projectiles and shaped charge jets. The latter produce a thin stretching metal jet, usually of copper, with a tip velocity of about 7-8 km/s. In order to obtain more weight-efficient solutions, there is a search for lighter materials and other protection techniques. In this thesis, ceramic and electromagnetic armours are studied. Ceramic materials are lighter than steel, and their high compressive strength makes them useful as armour materials. Electromagnetic armour consists of two metal plates connected to an electric power supply capable of delivering a strong current pulse. A conductive penetrator passing through both plates is destroyed by the effects of the resulting current.

Tests of the ceramic armour materials alumina and boron carbide were performed with reverse impact technique, which signifies that a target assembly (ceramic confined in a metal cylinder) was launched by a gun towards a projectile placed in front of the gun barrel. By this technique yaw was eliminated, but the geometric scale had to be very small. Therefore, we studied scaling laws for ceramic armour through a series of tests with direct impact technique and projectile diameters from 2 to 10 mm. The small scale has the advantage that flash X-ray photography can be used to photograph the projectile inside the ceramic target. The phenomenon of interface defeat or dwell was also demonstrated. It signifies that the ceramic, at least for a short time, can withstand the impact pressure so that the projectile just flows out onto the target surface. A transition velocity, above which dwell does not occur, was determined. Simulations were performed with the continuum-dynamic code Autodyn and by use of a model for the brittle ceramic materials by Johnson and Holmquist. The simulations reasonably well represented the penetration behaviour above the transition velocity. They also did below, if under this condition the ceramic model was forced to remain undamaged.

The performance of electromagnetic armour was tested against a shaped charge jet. The jet was registered with shadowgraph flash X-ray photography between the plates and after passing through the plates. The current through the jet and the voltage over the plates were also registered. The current caused heating leading to melting and even vaporization. The magnetic Lorentz force compressed the jet radially, and as this effect increases with decreasing jet radius, instability may arise. Explosions in the compressed regions resulted in a fragmented jet with disk-shaped fragments which are less effective penetrators than the elongated fragments obtained in the absence of current. We also performed a theoretical study, in which the penetrator was subjected to small elastic strains only and the current was constant. The magnetic field was determined by FFT, and the stresses due to the Lorentz force were calculated with a semi-analytical method. The velocity skin effect was demonstrated.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 73 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1032
National Category
Interaction Technologies
Research subject
Engineering Science with specialization in Solid Mechanics
Identifiers
urn:nbn:se:uu:diva-197563 (URN)978-91-554-8633-4 (ISBN)
Public defence
2013-05-17, Polhemssalen, Ångström, Uppsala, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2013-04-25 Created: 2013-03-27 Last updated: 2013-08-30Bibliographically approved

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