Analysis of Multi-Material Plates Under Explosive LoadingEngineering Project Final Report PresentationBy James Danyluk

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.

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

Hydrocode ModelSingle Plate Model

Two Plate Model

Three Plate Model

Trial Layer 1 Layer 2 Layer 31 6061-T6 - -2 Steel v250 - -3 304L - -4 Tung - -5 6061-T6 Tung -6 Tung 6061-T6 -7 304L Tung -8 Tung 304L -9 Polyethylene Tung -

10 Tung Polyethylene -11 Steel v250 Tung -12 Tung Steel v250 -13 Tung 304L Tung14 Tung 6061-T6 Tung15 Tung Polyethylene Tung16 304L Tung 304L17 Steel v250 Tung Steel v25018 6061 Tung 606119 Polyethylene 304L Tung20 Tung 304L Polyethylene

Single Plate Hydrocode ResultsAl6061-T6 Plate

Single Plate Hydrocode ResultsShock wave in explosive Shock wave in plate

Rarefaction wave generated

Two Plate ResultsTungsten/Polyethylene Combination Tungsten/304L Steel Combination

Three Plate ResultsTungsten/Polyethylene/Tungsten 304L/Tungsten/304L

Spall Failure Model ResultsTungsten/Aluminum

Aluminum/Tungsten

Two Dimensional Model Hydrocode Model

A two dimensional model was constructed. Air was placed around the HE and Solid Layers. A single detonation point was used to detonated the

HE. Symmetry conditions were used to simplify the

model.

AirHMX

Air

Air

Detonation PointSurrounding Air

Symmetry Plane

Solid Plates

Two Dimensional Model ResultsTungsten/Polyethylene Combination

Two Dimensional Model ResultsSteel/Tungsten Combination

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.