Podcast
Questions and Answers
Creep is the time-dependent deformation of a material subjected to a constant ____?
Creep is the time-dependent deformation of a material subjected to a constant ____?
False
Creep is temperature-dependent and becomes significant when the temperature is greater than ___?
Creep is temperature-dependent and becomes significant when the temperature is greater than ___?
False
Creep failure occurs when the dimensional change renders the material useless in performing its intended function, such as in creep ____?
Creep failure occurs when the dimensional change renders the material useless in performing its intended function, such as in creep ____?
False
Sufficient strain or creep can result in fracture, known as stress rupture or creep ____?
Sufficient strain or creep can result in fracture, known as stress rupture or creep ____?
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Creep occurs by atomic diffusion, atoms move in response to the applied stress and temperature, to fill the voids in the grains, resulting in an elongation of the grain in the direction parallel to the applied ____?
Creep occurs by atomic diffusion, atoms move in response to the applied stress and temperature, to fill the voids in the grains, resulting in an elongation of the grain in the direction parallel to the applied ____?
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Creep mechanisms involve a diffusion-controlled process where vacancies in the material’s microstructure migrate toward ____ boundaries.
Creep mechanisms involve a diffusion-controlled process where vacancies in the material’s microstructure migrate toward ____ boundaries.
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Creep failures may appear in a ductile or brittle manner.
Creep failures may appear in a ductile or brittle manner.
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In a creep test, strain is measured as a function of time at a constant stress and temperature.
In a creep test, strain is measured as a function of time at a constant stress and temperature.
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Ceramics have a very high resistance to deformation by creep partly because of their characteristically high melting temperatures.
Ceramics have a very high resistance to deformation by creep partly because of their characteristically high melting temperatures.
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To prevent failure due to creep deformation, it is important to know the operating conditions of the system when selecting materials for an application. Materials experience thermally activated creep at different temperatures.
To prevent failure due to creep deformation, it is important to know the operating conditions of the system when selecting materials for an application. Materials experience thermally activated creep at different temperatures.
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Dr. Reham Reda Abbas's research involves the assessment of microstructure degradation of creep exposed boiler steels.
Dr. Reham Reda Abbas's research involves the assessment of microstructure degradation of creep exposed boiler steels.
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Creep is a phenomenon experienced by components in boilers, gas turbine engines, and ovens.
Creep is a phenomenon experienced by components in boilers, gas turbine engines, and ovens.
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In a creep test, the slope of the strain vs. time curve is the creep rate of the material.
In a creep test, the slope of the strain vs. time curve is the creep rate of the material.
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Materials with high melting temperatures are often selected for turbine engine blades to combat the sustained stress over time at a relatively high temperature.
Materials with high melting temperatures are often selected for turbine engine blades to combat the sustained stress over time at a relatively high temperature.
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Polymers or tin-lead solder can be susceptible to creep at much lower temperatures compared to nickel-based superalloys.
Polymers or tin-lead solder can be susceptible to creep at much lower temperatures compared to nickel-based superalloys.
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Rupture lifetime (tr) in a creep test is the total time before failure occurs.
Rupture lifetime (tr) in a creep test is the total time before failure occurs.
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Study Notes
Creep Fundamentals
- Creep refers to time-dependent deformation of a material under constant stress.
- Significant creep occurs at temperatures exceeding approximately 0.4 times the melting temperature of the material.
Creep Failure
- Creep failure results when dimensional changes impair a material's functionality, often seen in components like boilers.
- Strain accumulation in materials can lead to stress rupture, a type of fracture associated with prolonged exposure to stress and temperature.
Creep Mechanisms
- Atomic diffusion is the primary mechanism driving creep, as atoms shift under stress and temperature to fill voids in grain structures, causing elongation parallel to the applied stress.
- Creep mechanisms include a diffusion-controlled process, where vacancies migrate toward grain boundaries.
Material Behavior
- Creep failures can manifest in either ductile or brittle forms, depending on the material and conditions.
- In creep testing, the relationship between strain and time is used to determine the creep rate, reflecting the rate of deformation under constant stress and temperature.
Material Selection
- Materials with high melting temperatures, such as ceramics, exhibit significant resistance to creep due to their structural properties.
- It is crucial to consider operating conditions when selecting materials for high-temperature applications, such as turbine engines or boilers.
Research and Applications
- Research by Dr. Reham Reda Abbas focuses on assessing microstructure degradation in boiler steels exposed to creep.
- Components in systems like gas turbine engines, ovens, and boilers experience creep, necessitating careful material selection.
Creep Compared Across Materials
- Polymers and tin-lead solder can exhibit creep at much lower temperatures compared to robust materials like nickel-based superalloys.
- Rupture lifetime (tr) in creep testing indicates the total time until failure under specified stress and temperature conditions.
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Description
Test your knowledge of Chapter 5 'Creep Failure and Design Against Creep' from the fourth year, first term of Mechanical Engineering Department. This quiz covers topics such as creep failure, creep test, stress and temperature effects on creep behavior, and design against creep.
