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Spall Fracture of Multi-Material Plates Under Explosive Loading

Spall Fracture of Multi-Material Plates Under Explosive Loading. Engineering Project Proposal Presentation By James Danyluk. Spall Fracture in Solids. Shock waves traveling through a solid material is reflected at changes in material or free surfaces.

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Spall Fracture of Multi-Material Plates Under Explosive Loading

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  1. Spall Fracture of Multi-Material Plates Under Explosive Loading Engineering Project Proposal 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. • This type of fracture is often seen in warhead applications, separation system and other energetic assemblies.

  3. Examples of Rarefaction Waves t = t1 t = t2 Free Surface Pressure wave reaches the free surface Free Surface Zero initial velocity Incoming pressure wave Initial velocity = Vo Pressure Pressure After interaction from the pressure wave, the free surface now moves at Velocity V=Vo Pressure wave is reflected Velocity is reversed, V=-Vo t = t3 Distance Distance Tensile stress generated due to opposite moving waves Pressure Distance

  4. Proposed Modeling Detonation front • 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. HE (HMX) Air Single Layer Three Layers Two Layers Selected Solid Materials Proposed Model Solid Material Setup

  5. Example Results Aluminum 6061-T6 t = 0µs HMX Air t = 2µs Pressure Wave is generated by the explosive t = 5.4µs Rarefaction wave generates a tensile stress in the material. Pressure Wave has traveled through the solid, generating a rarefaction wave t = 9µs Tensile stress exceeds the spall strength, fracturing the material.

  6. Expected Outcomes • Materials 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.

  7. 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

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