# Virtual Testing of Composite Structures Made of High Entropy Alloys and Steel

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## Abstract

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## 1. Introduction

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- Higher hardness, as a measure of resistance of solid materials to the penetration in surface of various types of penetrators, with permanent changes of shape when a static or dynamic force is applied to them; the macroscopic hardness is generally characterized by the nature and strength of inter-molecular links, the behavior of the solid material under the force action being complex;
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- High tenacity at low temperatures, because it represents the ability of the metallic material to absorb the breaking energy, to oppose the emergence and spread of various types of cracks, accumulating the energy necessary for the formation of surface rupture and for the fast local deformation under shock conditions;
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- High impact resistance, which is the relative susceptibility to damage by the action of forces applied at high speed.

## 2. Material Models for Virtual Ballistic Testing

## 3. Virtual Testing Campaign

^{−3}ms.

_{yo}—initial yield stress and E

_{t}—tangential modulus.

_{p}, by the relation

_{0}, T

_{m}are the room temperature and melting temperature of the material, respectively; ε

_{p}—equivalent plastic strain; $\stackrel{\u2022}{{\displaystyle {\epsilon}_{p}}}$—plastic strain rate; $\stackrel{\u2022}{{\displaystyle {\epsilon}_{0}}}$—the effective plastic strain rate of the quasi-static test used to determine the yield and hardening parameters A, B and n; T—local temperature in the material.

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- Bullet caliber of 7.62 × 39 mm;
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- Shooting angle of 0°;
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- Incendiary perforating bullet weight of 7.67 g;
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- Steel core weight of 4 g.

- Composite structure: HEA-STEEL welded by explosionTesting speeds: V
_{01}= 900 m/s; V_{02}= 1000 m/s; V_{03}= 1100 m/s; - Composite structure: HEA-STEEL contour weldedTesting speeds: V
_{01}= 800 m/s; V_{02}= 900 m/s; V_{03}= 1000 m/s; - Composite structure: HEA-STEEL free on contourTesting speeds: V
_{01}= 700 m/s; V_{02}= 800 m/s; V_{03}= 900 m/s; - Composite structure: HEA-STEEL-Duralumin sandwich typeTesting speeds: V
_{01}= 400 m/s; V_{02}= 500 m/s; V_{03}= 700 m/s.

## 4. Results

## 5. Discussion

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

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**Figure 6.**The mesh model with finite elements for the incendiary armor piercing bullet, 7.62 mm caliber.

**Figure 12.**The behavior of the HEA-STEEL composite structure, welded by explosion, at impact with an incendiary armor piercing bullet (7.62 mm caliber) with different initial speeds.

**Figure 13.**The behavior of the HEA-STEEL composite structure, welded to contour, at impact with an incendiary armor piercing bullet (7.62 mm caliber) with different initial speeds.

**Figure 14.**The behavior of the HEA-STEEL composite structure, free on contour, at impact with an incendiary armor piercing bullet (7.62 mm caliber) with different initial speeds.

**Figure 15.**The behavior of the sandwich type composite structure at impact with an incendiary armor piercing bullet (7.62 mm caliber) with different initial speeds.

Ensemble | Components | Elements | Nodes |
---|---|---|---|

Incendiary armor piercing bullet, 7.62 mm caliber | Core | 101,888 | 107,935 |

Case | 46,080 | 54,719 | |

Bullet | 20,160 | 24,375 | |

Primer | 12,288 | 14,847 | |

Propellant | 9216 | 10,735 | |

Total | 189,632 | 212,611 | |

HEA—steel composite structure | HEA | 92,160 | 99,977 |

Steel | 92,160 | 99,977 | |

Total | 184,320 | 199,954 | |

TOTAL | 373,952 | 412,565 |

Material | Part | Mechanical Characteristics | ||||
---|---|---|---|---|---|---|

Density ρ | Young Modulus E | Poisson Coefficient $\mathit{\nu}$ | Yield Stress σ_{y} | Tangential Modulus E_{t} | ||

Kg/m^{3} | MPa | - | MPa | MPa | ||

Hardened steel | Core | 7850 | 2.1 × 10^{5} | 0.3 | 2800 | 15,000 |

Brass | Case | 8100 | 1.5 × 10^{5} | 0.33 | 320 | 10,000 |

Lead | Bullet | 11,200 | 1 × 10^{5} | 0.37 | 50 | 100 |

Low carbon steel | Primer | 7850 | 2.05 × 10^{5} | 0.3 | 210 | 5000 |

Pyrotechnic material | Propellant | 1200 | 1.0 × 10^{3} | 0.49 | 10 | 20 |

HEA | Plate 1 | 7720 | 2.2 × 10^{5} | 0.35 | 1550 | 5000 |

Steel | Plate 2 | 7850 | 2.1 × 10^{5} | 0.3 | 1250 | 3000 |

Metallic Material | Mechanical Characteristics | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|

Density, ρ | Transverse Modulus, G | Young Modulus, E | Poisson Coefficient, $\mathit{\nu}$ | Johnson–Cook Coefficients | |||||||

A | B | n | C | m | T_{melt} | T_{0} | |||||

Kg/m^{−3} | MPa | MPa | - | MPa | MPa | - | - | - | K | K | |

HEA | 7720 | 0.81 × 10^{5} | 2.2 × 10^{5} | 0.35 | 1550 | 1200 | 0.24 | 0.032 | 1.00 | 1850 | 300 |

Armor steel | 7850 | 0.82 × 10^{5} | 2.1 × 10^{5} | 0.3 | 1250 | 3200 | 0.18 | 0.15 | 1.00 | 1763 | 300 |

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**MDPI and ACS Style**

Geantă, V.; Cherecheș, T.; Lixandru, P.; Voiculescu, I.; Ștefănoiu, R.; Dragnea, D.; Zecheru, T.; Matache, L.
Virtual Testing of Composite Structures Made of High Entropy Alloys and Steel. *Metals* **2017**, *7*, 496.
https://doi.org/10.3390/met7110496

**AMA Style**

Geantă V, Cherecheș T, Lixandru P, Voiculescu I, Ștefănoiu R, Dragnea D, Zecheru T, Matache L.
Virtual Testing of Composite Structures Made of High Entropy Alloys and Steel. *Metals*. 2017; 7(11):496.
https://doi.org/10.3390/met7110496

**Chicago/Turabian Style**

Geantă, Victor, Tudor Cherecheș, Paul Lixandru, Ionelia Voiculescu, Radu Ștefănoiu, Daniel Dragnea, Teodora Zecheru, and Liviu Matache.
2017. "Virtual Testing of Composite Structures Made of High Entropy Alloys and Steel" *Metals* 7, no. 11: 496.
https://doi.org/10.3390/met7110496