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What is creep in the context of material science?
What is creep in the context of material science?
- Deformation caused by rapid heating and cooling of a material
- Temperature-dependent deformation of a material subjected to variable stress
- Time-dependent deformation of a material under constant stress (correct)
- Stress-dependent deformation of a material under constant temperature
When does creep become significant in a material?
When does creep become significant in a material?
- When the temperature is less than 0.4 Tm
- When the stress is greater than the yield stress
- When the temperature is greater than 0.4 Tm (melting temperature on an absolute scale) (correct)
- When the stress is less than 0.4 Tm
Under what conditions does a material experience creep failure?
Under what conditions does a material experience creep failure?
- When the temperature is close to the melting point
- When the stress exceeds the ultimate tensile strength
- When the dimensional change renders the material useless in performing its intended function (correct)
- When the material undergoes rapid heating and cooling cycles
What is the result of sufficient strain or creep in a material?
What is the result of sufficient strain or creep in a material?
Which process governs creep mechanisms?
Which process governs creep mechanisms?
How do vacancies in a material's microstructure contribute to creep?
How do vacancies in a material's microstructure contribute to creep?
What are the mechanisms of creep mentioned in the text?
What are the mechanisms of creep mentioned in the text?
What can make materials susceptible to creep at different temperatures?
What can make materials susceptible to creep at different temperatures?
What is a typical creep test measure?
What is a typical creep test measure?
Which materials are mentioned as susceptible to creep at relatively high temperatures?
Which materials are mentioned as susceptible to creep at relatively high temperatures?
Where do components that experience creep phenomenon exist?
Where do components that experience creep phenomenon exist?
What can cause creep failures to appear in a brittle manner?
What can cause creep failures to appear in a brittle manner?
Why are materials with high melting temperatures often selected for turbine engine blades?
Why are materials with high melting temperatures often selected for turbine engine blades?
What is the slope of the strain vs. time curve in a creep test?
What is the slope of the strain vs. time curve in a creep test?
What is an example application whereby components experience creep phenomenon?
What is an example application whereby components experience creep phenomenon?
What can ceramics exhibit at extremely high temperatures?
What can ceramics exhibit at extremely high temperatures?
Ceramics have a very low resistance to deformation by creep due to their characteristically low melting temperatures.
Ceramics have a very low resistance to deformation by creep due to their characteristically low melting temperatures.
The rupture lifetime (tr) in a creep test is the time taken for the material to reach its maximum strain.
The rupture lifetime (tr) in a creep test is the time taken for the material to reach its maximum strain.
Thermal activation of dislocations refers to the reduction in energy required to move pinned dislocations at increasing temperatures.
Thermal activation of dislocations refers to the reduction in energy required to move pinned dislocations at increasing temperatures.
Boilers, gas turbine engines, and ovens are examples of components that do not experience creep phenomenon.
Boilers, gas turbine engines, and ovens are examples of components that do not experience creep phenomenon.
Materials with high melting temperatures are often selected for turbine engine blades due to their resistance to creep at relatively high temperatures.
Materials with high melting temperatures are often selected for turbine engine blades due to their resistance to creep at relatively high temperatures.
Creep failures always appear in a ductile manner.
Creep failures always appear in a ductile manner.
In a creep test, strain is measured as a function of stress at a constant temperature.
In a creep test, strain is measured as a function of stress at a constant temperature.
Nickel-based superalloys are not susceptible to creep at relatively high temperatures.
Nickel-based superalloys are not susceptible to creep at relatively high temperatures.
Creep becomes significant in a material only at extremely high temperatures.
Creep becomes significant in a material only at extremely high temperatures.
The slope of the strain vs. time curve in a creep test represents the strain rate of the material.
The slope of the strain vs. time curve in a creep test represents the strain rate of the material.
Creep is a time-independent deformation of a material subjected to a constant stress.
Creep is a time-independent deformation of a material subjected to a constant stress.
Creep is not influenced by temperature.
Creep is not influenced by temperature.
Creep failure occurs when the dimensional change of a material makes it unsuitable for its intended function.
Creep failure occurs when the dimensional change of a material makes it unsuitable for its intended function.
Creep fracture is also known as elastic deformation.
Creep fracture is also known as elastic deformation.
Creep occurs when atoms move in response to the applied stress and temperature, filling the voids in the grains.
Creep occurs when atoms move in response to the applied stress and temperature, filling the voids in the grains.
Materials with low melting temperatures are often selected for turbine engine blades.
Materials with low melting temperatures are often selected for turbine engine blades.
Study Notes
Creep in Material Science
- Creep is a time-dependent deformation of materials subject to constant stress, particularly at high temperatures.
- It becomes significant at extremely high temperatures where strain accumulates over time.
Conditions for Creep Failure
- Creep failure occurs when the dimensional changes in a material render it unsuitable for its intended function.
- Creep fractures typically manifest in a ductile manner, contrary to brittle failure modes.
Mechanisms and Influences on Creep
- Creep mechanisms are governed by thermal activation of dislocations, where increased temperatures reduce the energy needed to move dislocations.
- Vacancies in a material's microstructure facilitate creep by allowing atoms to move under stress, filling voids within the grains.
Creep Conditions
- Materials with high melting temperatures are often chosen for turbine engine blades due to their enhanced resistance to creep under high temperature conditions.
- Conversely, materials with low melting temperatures are more susceptible to creep failures.
Creep Testing
- A typical creep test measures strain as a function of stress at a constant temperature, indicating how a material behaves under prolonged loading.
- The slope of the strain vs. time curve during a creep test reveals the strain rate of the material.
Applications and Examples
- Common applications where components experience creep include turbines, boilers, and ovens.
- Ceramics can exhibit unique properties at extremely high temperatures, although they are generally characterized by low resistance to deformation from creep.
Overview of Creep Performance
- The rupture lifetime (tr) in a creep test signifies the duration required for a material to reach maximum strain.
- Nickel-based superalloys are noted for their resistance to creep at elevated temperatures, making them suitable for critical applications.
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Description
Explore the concepts of creep failure, creep test, stress and temperature effects on creep behavior, and design against creep in mechanical engineering. This quiz covers Chapter 5 of the Fourth Year First Term curriculum, taught by Dr. Reham Reda Abbas.