Spall Fracture of Multi-Material Plates Under Explosive Loading Engineering Project Proposal...
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Transcript of Spall Fracture of Multi-Material Plates Under Explosive Loading Engineering Project Proposal...
Spall Fracture of Multi-Spall Fracture of Multi-Material Plates Under Material Plates Under Explosive LoadingExplosive LoadingEngineering Project Proposal PresentationBy James Danyluk
Spall Fracture in SolidsSpall Fracture in SolidsShock 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.
This type of fracture is often seen in warhead applications, separation system and other energetic assemblies.
Examples of Rarefaction Examples of Rarefaction WavesWavest = t1 t = t2
t = t3Distance
Pre
ssure
Incoming pressure waveInitial velocity = Vo
Free SurfaceZero initial velocity
Distance
Pre
ssure
Pressure wave reaches the free surface
Free Surface
Distance
Pre
ssure
Pressure wave is reflectedVelocity is reversed, V=-Vo
After interaction from the pressure wave, the free surface now moves at Velocity V=Vo
Tensile stress generated due to opposite moving waves
Proposed ModelingProposed Modeling ANSYS AUTODYN, an explicit dynamics code, will be used to
model the system. The Euler Multi-material solver will be used. The model will be setup as with an Explosive, Solid Material
and Air layers. The analysis will model different materials and material
combinations◦ The tensile wave generated in the solid material(s) will be
examined in each model.
Solid Material SetupProposed Model
HE (HMX) Air
Selected Solid Materials
Detonation front
Single Layer Two Layers Three Layers
Example ResultsExample Resultst = 0µs
t = 2µs
HMX Air
Aluminum 6061-T6
Pressure Wave is generated by the explosive
t = 5.4µs
Pressure Wave has traveled through the solid, generating a rarefaction wave
Rarefaction wave generates a tensile stress in the material.
t = 9µs Tensile stress exceeds the spall strength, fracturing the material.
Expected OutcomesExpected OutcomesMaterials under explosively induced
loading may experience spallation due to the rarefaction waves.
Stacking significantly different materials can either prevent spalling or accidentally cause it.
The study will show how different materials being stacked can to induce or prevent spalling.
Schedule/MilestonesSchedule/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