Unit 8 - Creep Lifing Methods Flashcards
1
Q
What factors can increase creep rate?
A
- Increasing stress
- Increasing temperature
2
Q
What are the stages of the creep curve?
A
- Primary stage is determined by grain deformation
- At the minimum rate, both the grains and zones contribute to strain accumulation
- Tertiary acceleration is due to cavity enhancement of zone deformation
3
Q
Why is it important to consider creep during the design stage?
A
Creep failure can occur at stresses which appear safe and are well below the UTS
4
Q
What factors can cause scatter in creep data?
A
- Temperature fluctuations
- Specimen imperfections
- Microstructural variations
- Test machine variability
5
Q
What effect can increasing stress and temperature have in relation to creep?
A
- Minimum creep rates increase
- Rupture time decreases
- The relationship between these two is known as the Monkman-Grant relationship
6
Q
How can long term creep properties be predicted?
A
By performing creep tests at the same stress but higher temperatures than the actual environment
7
Q
For aerospace applications, what factor relating to creep can limit component life?
A
Creep strain exceeding a specified limit
