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Utility of FEM and FEA

Utility of FEM and FEA. Evaluate possible designs without manufacturing a prototype Augment experimental capabilities time money. Heart Disease. 4 million patients in the U.S. are victims of heart failure, and nearly 400,000 new cases are diagnosed each year 2,800 receive heart transplants

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Utility of FEM and FEA

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  1. Utility of FEM and FEA • Evaluate possible designs without manufacturing a prototype • Augment experimental capabilities • time • money

  2. Heart Disease • 4 million patients in the U.S. are victims of heart failure, and nearly 400,000 new cases are diagnosed each year • 2,800 receive heart transplants • Heart disease is the leading cause of death and disability in the U.S.

  3. Arrow LionHeartTM • LVAD (Left Ventricular Assist Device) • electric pulsatile blood pump • fully implanted in upper abdomen • 70 cc volume 8 L/min at beat rate of 135 = stroke volume of 60 cc

  4. Introduction Poly(urethaneurea) Blood Sac Pusher- plate Titanium Pump Case

  5. Introduction • Design goal: 2 yrs @50,000,000 cycles/yr = 100,000,000 cycles • FEA used to evaluate various pump designs and their effectiveness at reducing the material stresses

  6. Finite Element Model • Axisymmetric • Pusherplate and pump case treated as rigid • 8-node continuum elements • Blood sac : homogeneous, hyperelastic (non-linear) • Frictionless contact

  7. 0.9 in 2.86 in Finite Element Model

  8. Boundary Conditions • Internal pressure = 100 mm Hg • Rigid pump case was fixed in space • Pusherplate displaced 0.8 inches • 30 increments • simulating ejection stroke of pump

  9. Parametric Study • 3 different thickness sacs (0.015, 0.02, 0.025 inches) • 2 pump case designs (tapered, not tapered) • 2 radii of curvature for sac (3/16 and 7/16 inch) • Total of 12 cases

  10. 3/16 inch of stroke 3/8 inch of stroke end of stroke

  11. 2 3 4 1

  12. Conclusions • Material stresses and strains are sensitive to the thickness of the blood sac • Radius of curvature has little influence on the peak stress in the blood sac, however, it does affect when the peak stress occurs during the stroke cycle

  13. Conclusions • Tapering the pump case can significantly alter blood sac stresses • All stresses and strains were much lower than the yield stress and strain for poly (urethaneurea)

  14. News Release (Feb. 28th, 2001) • First fully implantable heart assist device implanted • As of March 12th, Arrow LionHeartTM recipient is stable and recovering as expected

  15. Total Artificial Heart • Fit into chest cavity • 50 cc • Develop a model to predict and minimize stresses in biomaterials, so that the durability of a reduced-size device is not adversely affected by pump scaling

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