Summer Internship 2011

1. Summer Internship 2011 Peter M. Mancini Los Alamos National Laboratory, XTD-1 Los Alamos, New Mexico USA LA-UR-11-04080

2. What is LANL? • Los Alamos National Laboratory • Founded in 1943 in Los Alamos, New Mexico • Manhattan Project

4. First Atomic Bombs Fat Man Little Boy

5. What Do You Want To Do? • Research - Government/University Lab - Novel topics, laboratory work environment, no right or wrong answer • Industry - Quality control - Improve/develop current designs - Manufacturing

6. Where Do You Live? • Companies in your city/state ~ 75% of the interns at LANL are from New Mexico Cheaper for the company: no travel expenses to go out there Companies here in Florida: Lockheed Martin (Orlando) Siemens (Orlando) Pratt and Whitney (West Palm Beach) • Certain hot spots for engineering i.e. Southwest U.S. has Sandia, LANL, Lawrence-Livermore National Lab

7. Who Do You Know? • Networking - Find and meet people who have jobs in your desired field or at the company you would like to work for - Ask around for open positions that are often not posted on a career website • With the huge amount of “John Smiths” applying for these positions, a personal recommendation to an employer can do you wonders

8. Stand Out • Words from my mentor (who is also the recruiter for X-Division): “I would take a student with a lower GPA from a decent, top 50 school with some research over a 4.0 from MIT with no real experience.” • Most kids weren’t exceptionally qualified • Low GPA? No worries. There are openings for you • Worked with a UF sophomore • You may feel like you don’t know enough to contribute to the research, but most of what you need for the job will be taught to you or you will have to read up on in textbooks and papers

9. Government Labs • Unique projects • Tons of interesting, optional lectures • Friendly work environment • Plenty of students (undergraduate and graduate) to interact with • Mentors to guide you in your research

10. Adventures

11. Overview of Project • Long Rod Penetrators (LRP) - armor-piercing ammunition generally used as anti-tank rounds • Uses high kinetic energy to penetrate target • Applies large force over small area to significantly exceed target’s yield strength • Generally use Tungsten or Uranium alloys, due to high density (~18 ) • Uniqueness of problem: • Semi-infinite target to model final penetration • No residual velocity • Due to normal impact of penetrator, simulation can be run as a quarter of the model

12. Experimental Data G. Silsby, Penetration of Semi-Infinite Steel Targets By Tungsten Long Rods at 1.3 to 4.5 km/s, Eighth International Symposium on Ballistics (October 1984)

13. PAGOSA • PAGOSAis a multi-dimensional / multi-material Eulerian hydrocode • Accurately models high strain rate deformation • Staggered mesh (U V W at vertices, P ρ e Sik at cell centers) • Multi-material (arbitrary number of materials per cell) • Young’s interface reconstruction for each material in each cell

14. PAGOSA Equations of State • Void • Ideal gas analytic equation • Polynomial • Mie-Grüneisen ( Us / Up ) • Osborne analytic • Becker-Kistiakowsky-Wilson (BKW) • SESAME, tabular EOS including phase changes • Jones-Wilkins-Lee (JWL), analytic EOS for explosive materials • Reactive High Explosive (HE) Burn Models : BKW-HE, JWL-HE

15. PAGOSA Strength Models • “Hydrodynamic” (no strength) • Elastic-Perfectly-Plastic • Johnson-Cook (JC) • Modified Steinberg-Cochran-Guinan (mod SCG) • Steinberg-Cochran-Guinan (SCG) • Kospall (SCG with additional thermal softening terms) • Preston-Tonks-Wallace (PTW) • Modified Preston-Tonks-Wallace (mod PTW) • Mechanical Threshold Stress (MTS)

16. Example of Mesh…(1mm cell size) RHA Armor Void Vo Tungsten Penetrator

17. Visual Void Target Interface Penetrator Model Space

18. Mesh Convergence • Decreasing cell size increases accuracy but also increases computational run time • Computational cost increases nonlinearly with decreasing cell size due to several factors: • Increased number of elements • Decreased integration time steps • Increased total number of integrations performed • Communication between the parallel processors

19. Mesh Convergence

20. Equation of State Comparison • Maintained constant strength model: • Target – Elastic Perfectly Plastic • Projectile – Elastic Perfectly Plastic • EOS Evaluated: • Target – Us/Up, Polynomial • Projectile – Us/Up, Polynomial • Results relatively insensitive to EOS

21. Flow Stress Models • Elastic Perfectly Plastic: • Material is linearly elastic • After yield, stress remains constant • with increasing load • 2 constants required for PAGOSA • Steinberg-Guinan and Johnson-Cook: • Includes strain, pressure, and thermal softening • Function of strain rate • Accounts for strain hardening • 7 constants required for PAGOSA

22. Strength Model Comparison

23. Hole Diameter Simulation of hole created at 3.335 km/s Differently sized hole diameters

24. Simulation Examples • Simulations • Low/High Velocity Shots • Wave Propagation

25. Low velocity: 1.291 km/s *Time in microseconds (µs)*

26. High Velocity: 4.525 km/s *Time in microseconds (µs)*

27. Wave Propagation

28. Conclusions • 1 mm cell size provides converged data in a reasonable run time. • Simulation data are generally insensitive of EOS • At low velocities, results are sensitive to strength model • At high velocities (> 3 km/s), the different models converge within 2% of each other and 5% of experimental data • Hydrocode simulation accurately models actual physics of the penetration, i.e. residual material and stress wave propagation • Equation of State • Low VelocityHigh Velocity • Projectile: Polynomial Polynomial • Target: Mie-Grüneisen (UsUp) Mie-Grüneisen (UsUp) • Strength Form • Low Velocity High Velocity • Projectile: Johnson-Cook Steinberg-Guinan • Target: Johnson-Cook Elastic Perfectly Plastic

29. Future Work • Run more data points to get a smooth curve • Search for different and/or more accurate EOS, strength, and fracture models, i.e. SESAME, Osborne, Johnson-Cook Damage • Compare other experimental data. • Add different shaped tips to penetrator to see how it effects penetration geometry (depth, hole diameter, etc..)

30. References • Wayne N. Weseloh, Sean P. Clancy, and James W. Painter, “PAGOSA Physics Manual,” Los Alamos National Laboratory report LA-14425-M (August 2010). • Wayne N. Weseloh, “PAGOSA Sample Problems,” Los Alamos National Laboratory report LA-UR-05-6514 (August 2005). • G. Silsby, Penetration of Semi-Infinite Steel Targets By Tungsten Long Rods at 1.3 to 4.5 km/s, Eighth International Symposium on Ballistics (October 1984) • Marc A. Meyers, “Dynamic Behavior of Materials,” John Wiley & Sons, Inc., 1994 • Private communication, Shuh-Rong Chen (MST) and Wayne Weseloh (XTD-1), 8 July 2011

31. Outline • Introduction / Overview • PAGOSA • Mesh Convergence • EOS Comparison • Strength Model Comparison • Simulation Examples • Low/High Velocity Shots • Wave Propagation • Conclusions • Future Work http://www.dtc.army.mil/tts/1997/proceed/walton/walton.html

32. Materials • Experimental: Silsby (1984) • Projectile: • 90W-7Ni-3Fe alloy • Yield Strength - 0.0119 Mbar (174 ksi) • Rockwell C 40.6 hardness • Density – 17.3 • L/D = 23 • - Initial Length (L) – 15.83 cm • - Diameter (D) – 0.683 cm • Target: • Rolled homogeneous armor (RHA) • 6 inch plate – BHN 270.4 • 8 inch plate – BHN 231.6 • Simulation: PAGOSA • Projectile: • matname = “Tungsten” • Yield Strength - 0.0119 Mbar (174 ksi) • Shear Modulus - 1.6 Mbar • Density – 17.3 • L/D = 23 • - Initial Length (L) – 15.83 cm • - Diameter (D) – 0.683 cm • Target: • 6 inch plate - BNH 270.4 • Yield Strength - 0.00917 (133 ksi) • Shear Modulus – 0.88 (88 GPa) • 8 inch plate - BNH 231.6 • Yield Strength - 0.007 (101 ksi) • Shear Modulus – 0.88 (88 GPa)