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Cavitation: A Brief Review of the Literature

Cavitation: A Brief Review of the Literature. Stephen P. Midson The Midson Group, Inc. NADCA Technical Paper From 1981. Definition of Cavitation: Davis & Murray. Cavitation means literal generation of cavities in a fluid

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Cavitation: A Brief Review of the Literature

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  1. Cavitation:A Brief Review of the Literature Stephen P. Midson The Midson Group, Inc.

  2. NADCA Technical PaperFrom 1981

  3. Definition of Cavitation:Davis & Murray • Cavitation means literal generation of cavities in a fluid • Occurs when the local pressure falls below the vapor pressure of the fluid • Whenever bubble nuclei are available • In zinc die casting, cavitation bubbles can be formed in the cavity, the gooseneck or the nozzle

  4. Mechanism of Cavitation Erosion

  5. Damage from Cavitation • Bubbles in the liquid can impact surfaces at speeds of 130 m/sec (300 miles/hr) • Peak surface stresses of 900 MPa (130 ksi) have been measured

  6. Effect of Flow System Geometry on Erosion • Cavitation bubbles are produced in places where low pressures occur • Bends • Changes in cross-section • Junctions between runners • Protrusions, such as ejector pins • Bubbles carried downstream & can collapse on die surfaces

  7. Examples of Cavitation

  8. Examples of Cavitation

  9. Morris Murray • “I talk often about cavitation because it is one of the most common failures of dies” • “During my course on runner design, I discuss cavitation due to ejector pins standing into the flow (or back from the die) & bad runner design (i.e. square bends)”

  10. DasGupta & KillingsworthSPX Corp. • SAE paper from 2000 • Reported cavitation erosion data for selected aluminum alloys used with squeeze & semi-solid casting • Results show that type of casting process, surface finish & alloy chemistry influence erosion wear

  11. Flow 3-D • Most recent version of Flow 3-D has potential to simulate cavitation and identify areas vulnerable to cavitation damage • The cavitation model can be turned on or off by the user for a filling analysis.

  12. End of FillingCavitation Potential Found Mostly on One Side of the Cavity Metal colored by cavitation potential (red is bad)

  13. 2008 Japanese Die Casting Association Congress • Kado, Hasuno & Asada • Ryobi Limited • Simulation test of die erosion in die casting with acoustic cavitation

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