Issue 54

A. Moslemi Petrudi et alii, Frattura ed Integrità Strutturale, 54 (2020) 226-248; DOI: 10.3221/IGF-ESIS.54.17

strength of the backing material's erosion), it is assumed that the projectile penetrates the ceramic and forms a smaller new cone. At the ceramic surface of the backing layer more than the erosive strength of the backing material, the ceramic cone begins to penetrate the backing material. Using mass accumulation theory, the basic equations of this theory can be written as follows: Newton's second law of the application for projectiles: ) 26 ( ¨ p p p F M X  

Newton's Second Law Application for Eroded Ceramic Front Panel:

M X 

) 27 (



c

CF

 

F F

c

1



t

Projectile Mass Reduction:





) 28 (

p p CF c M X X       

Reduce ceramic mass from the ceramic front panel

) 29 (





c CF C C M X X       Projectile forces when the projectile is eroded or mushrooming is formed:

) 30 (

 

F

P

PES

The relationship between ceramic front velocity, ceramic erosion, and ceramic velocity is:

) 31 (

CF CE C X X X      The joint surface force 1 F will be different for different phases of erosion, mushrooming shape, and projectile rigidity. In the above equations p X  and p X  projectile velocity and acceleration at any instant, CF X  ceramic front element speed, C X  ceramic element velocity, and CES  and PES  the erosion stresses are ceramic and projectile. Model by Forrestal and Luk Forrestal and Luk proposed a model for penetrating a projectile with a spherical nose. To calculate the force applied to the projectile during penetration, they must consider the effect of frictional force in addition to normal stress. To do this, the tangential stress was defined as follows [12]: ) 32 ( t n    where µ is the slip friction coefficient between the target material and the projectile.

Figure 12: Cylindrical projectile with spherical nose [10].

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