Unit 1 - Thrust or Bust

Question 1

What are the types of fatigue testing methods for gas turbines?

Answer 1

Full Scale: Tests entire component, required for approval but has poor statistical validity.
Sub-Component: Approximates full component performance, identifies life-limiting parts, better statistical significance.
Laboratory: Uses test piece geometry, highest statistical significance, and requires Finite Element Method (FEM) in design​

Question 1

What are the primary failure modes in turbine materials?

Answer 1

The primary failure modes in turbine materials include fatigue, creep, oxidation, and thermal mechanical fatigue.

Question 2

What are the classifications of parts in gas turbines?

Answer 2

Critical: Failure endangers the airframe (e.g., discs, shafts).
Sensitive: Failure may shut down the engine (e.g., blades, combustion chambers).
Unclassified: Low risk to engine operation (most static parts)​

Question 3

How does creep affect the performance of materials in gas turbines?

Answer 3

Creep, the slow deformation of materials under high temperature and stress leading to changes in shape and the loss of mechanical properties. This can reduce the efficiency and safety of the turbine.

Question 4

Explain the significance of fracture mechanics in turbine blade design.

Answer 4

Fracture mechanics is crucial in turbine blade design as it helps predict the growth and propagation of cracks in turbine blades.
Ensures blade durability.

Question 5

Role of abradable coatings in gas turbines?

Answer 5

Improves efficiency by reducing clearance between blades and casing, wears preferentially.

Question 6

Role of fatigue lifing in gas turbines?

Answer 6

Fatigue-lifing methods are used to predict the number of cycles a turbine component can withstand before failure.