🔍 Key Concepts

• Babbitt metal properties in journal bearings (soft, low-melting, good embeddability) • How load and film thickness change at low vs. full speed in turbine bearings • Effect of vibration and misalignment on bearing surfaces

💭 Think About

• Think about when the oil film supporting the shaft is strongest and when it is weakest. At which operating condition is the shaft most likely to contact the Babbitt lining? • Consider which option would cause repeated metal-to-metal contact or uneven loading rather than just high speed alone. • Ask yourself: which condition places abnormal stress or fatigue on the Babbitt layer, especially near bond lines or edges?

✅ Before You Answer

• Compare how hydrodynamic oil film develops at low-speed vs. full-speed in a turbine journal bearing. • Ask: Does vibration alone usually crack Babbitt, or does it need loss of film / misalignment to do damage? • Verify which condition is most associated with boundary lubrication (thin or broken oil film) leading to fatigue and cracking of the Babbitt.