Spall Fracture of Multi-Material Plates Under Explosive Loading

1. Spall Fracture of Multi-Material Plates Under Explosive Loading Engineering Project Second Progress Report Presentation By James Danyluk

2. Spall Fracture in Solids • Shock waves traveling through a solid material is reflected at changes in material or free surfaces. • These reflected shock waves are known as rarefaction waves or relief waves. • When a free surface and rarefaction wave interact, a tensile stress can be generated in the solid material. • This can also happen with two rarefaction waves interact. • If this tensile stress exceeds the dynamic tensile strength, or spall strength, the material can fracture.

3. Hydrocode Model • ANSYS AUTODYN, an explicit dynamics code, was used to model the system. • The Euler Multi-material solver was used. • The model was setup with an Explosive, Solid Material and Air layers. • The analysis modeled different materials and material combinations • The tensile wave generated in the solid material(s) was examined in each model. • The analysis was separated into four sets of iterations • 1D Elastic only material models • 1D Elastic/Plastic material models • 1D Elastic/Plastic/Failure material models • 2D Elastic/Plastic/Failure material models

4. Hydrocode Model Single Plate Model Two Plate Model Three Plate Model

5. Single Plate Hydrocode ResultsAl6061-T6 Plate

6. Single Plate Hydrocode Results Shock wave in explosive Shock wave in plate Rarefaction wave generated

7. Two Plate Results Tungsten/Polyethylene Combination Tungsten/304L Steel Combination

8. Three Plate Results Tungsten/Polyethylene/Tungsten 304L/Tungsten/304L

9. Spall Failure Model Results Tungsten/Aluminum Aluminum/Tungsten

10. Current Conclusions • Stacking materials can dictate how spall failures occur • For most cases, the outer solid layer developed spall planes, while the inner layer remained intact. • This method can be used to develop “spall plates”, plates that are intentionally designed to spall off, leaving the desired material (inner layer) intact. • When a highly dense material (tungsten) is mated next to a very low density material (aluminum, polyethylene), a rarefaction wave can be generated by the material interface that will cause the tungsten plate to spall. • Other material combinations did produce rarefaction waves, but they were not large enough to overcome the explosive loading and produce a tensile stress in the plate. • In these cases, the spall can happen in both the inner and outer layers, but the amount of spall is highly reduced in the outer layer.

11. Schedule/Milestones • 9/21/10: Submit Proposal • 9/28/10: Complete Hand Calculations/Finish Research • 10/5/10: Complete 1-D Elastic Hydrocode Model Results • 10/12/10: Complete 1-D Elastic/Plastic Hydrocode Model Results • 10/19/10: Submit First Progress Report • 10/26/10: Complete 1-D Elastic/Plastic/Failure Hydrocode Model Results • 11/9/10: Submit Second Progress Report • 11/18/10: Complete 2-D Elastic/Plastic/Failure Hydrocode Model Results • 11/30/10: Submit Final Draft • 12/14/10: Submit Final Report