New Trends in Computational Solid Mechanics

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New Trends in Computational Solid Mechanics
Wednesday, 10/23/2002
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Class Progress
Visualization abstract concept (stress,2D, 3D),
mechanical field Atomistic Simulations Stochasti
c simulations random walk, Brownian
movement Monte Carlo method (MC)
Ensemble Molecular Dynamics (MD)
Trajectory Continuum Simulation Material Point
Method (MPM)
Finite Element Method (FEM)
Multiscale simulation Adaptive Mesh
Refinement/Coarsening Renormalization
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Computational Solid Mechanics
Stress, strain, constitutive model Defects,
dislocation Fracture Surface roughness
Biomedical Engineering Information Technology
Nanotechnology
Bio/IT/Nano
Bio/IT/Nano
FEM, MPM MD, MC
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Heart
The heart is a muscular organ located just to the
left of the breast bone (sternum). It is about
the size of your fist, and this amazing muscle
pumps 4300 gallons of blood a day. The heart has
four chambers
Atria. The top two chambers that receive blood
from the body or lungs. Ventricles. The bottom
two chambers. The right ventricle pumps blood to
the lungs to pick up oxygen, The left ventricle
pumps blood to the rest of the body and is the
strongest chamber. Valves. There are four valves
in the heart that help to direct blood flow.
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Mechanical Heart Valve

• Structurally designed to last a lifetime
• Most are constructed of pyrolytic carbon, a
  highly durable and biocompatible material
• Excellent blood flow characteristics
• Patient requires long-term anticoagulation
  therapy ("blood thinners", this medication
  actually slows the clotting process of blood)
• Patient may hear the valve leaflets open and
  close

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Biocompatibility

• Mechanical valves are recognized for their
  exceptional durability, but require life-long
  anticoagulation medication.

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Stress distribution in Mechanical Heart Valve
Harsh environment Roughness evolution
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Platelet Coagulation
When reaching a damaged vessel, platelets release
a chemical which sets up a change of events
leading to the production of long, strand like
threads called fibrin. Many fibrin threads join
together to plug a vessel.
Platelets are the smallest corpuscular components
of human blood (diameter 2-4µm) - the
physiological number varies from 150,000 to
300,000/mm3 blood.
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Flow Field Near Rough Surface
Turbulence
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Blood clot
As the blood flows turbulently over the rough
surface of the artificial heart, the blood begin
falling on itself and clotting.
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Shock Wave
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Extracorporeal Shock Wave Lithotripsy (ESWL)
Extracorporeal shock wave lithotripsy (ESWL) is a
medical procedure used to break kidney stones
into fragments small enough for natural
elimination.
A shocking blow for kidney stones
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Kidney Stone
Some of the smaller kidney stones that are less
than 5mm in diameter pass on along during
urination. However, a larger stone that does not
pass on out can block the urinary tract. If left
untreated, the blockage may hamper the normal
function of the kidney and may cause complete
shutdown of the affected kidney in a few days.
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Extracorporeal Shock Wave Lithotripsy
high-frequency sound waves to crush kidney stones
into granules small enough to be passed in the
urine
Noninvasive
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Mechanism of Stone Fails
Evidence that the shock wave may lead to
permanent damage to healthy tissue in the kidney.
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Spallation
Spallation refers to large tensile stress that
leading to stone failure probably by fatigue.
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Cavitation
Cavitation occurs when the tensile stress of the
shock wave is strong enough to make fluid rip
apart. The nature of the shock wave in
lithotripsy leads to a dramatic growth of the
bubble followed by a subsequently violent
collapse. The collapse leads to an probably
surface damaging microjets.
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Mechanical interaction of shock wave with renal
calculi
After the application of 40 shock waves a stone
phantom is fractured into two pieces. Here the
fracture plane is oriented perpendicular to the
wave propagation and exhibits a circular rings.
The diameter of the stone phantom (magnesium
oxide) is 15mm."