🔍 Key Concepts

• Hydrodynamic (fluid film) lubrication in a journal bearing • How relative motion between journal and bearing creates a pressure wedge in the oil film • Difference between system supply pressure and locally generated film pressure

💭 Think About

• Think about how the rotating journal pulls oil into a converging wedge between the shaft and bearing — what does this do to the oil pressure inside that wedge? • Is the pressure in the oil film only limited to the pump’s supply pressure, or can motion and geometry create a different (higher or lower) pressure locally? • If the pressure in the wedge were the same as the supply pressure, would the shaft be fully supported on a film of oil under heavy load?

✅ Before You Answer

• Compare pump (supply) pressure to dynamic pressure created by the moving shaft in a narrowing oil film. • Consider where in the bearing the load is actually carried — is it at the oil groove or in the loaded region opposite it? • Verify whether the maximum supporting pressure occurs at the point of minimum film thickness, not at the groove or inlet.