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    Experiment Name: Creep Analysis and Case Study

    Uploaded by

    Jessia Alam
    Creep is the tendency of a solid material to slowly deform over time under the influence of a constant mechanical load or stress, especially at high temperatures. The document discusses the different stages of creep (primary, secondary, tertiary), factors that influence creep rates and failure (temperature, stress, grain size), and mechanisms of creep deformation including diffusion, dislocation movement, and grain boundary sliding. It provides an overview of creep analysis and the importance of considering creep for materials used in high-temperature applications like gas turbines.

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    Experiment Name: Creep Analysis and Case Study

    Uploaded by

    Jessia Alam
    99 views5 pages
    Creep is the tendency of a solid material to slowly deform over time under the influence of a constant mechanical load or stress, especially at high temperatures. The document discusses the different stages of creep (primary, secondary, tertiary), factors that influence creep rates and failure (temperature, stress, grain size), and mechanisms of creep deformation including diffusion, dislocation movement, and grain boundary sliding. It provides an overview of creep analysis and the importance of considering creep for materials used in high-temperature applications like gas turbines.

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    creep analysis shortly

    Original Title

    Creep

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    Creep is the tendency of a solid material to slowly deform over time under the influence of a constant mechanical load or stress, especially at high temperatures. The document discusses the different stages of creep (primary, secondary, tertiary), factors that influence creep rates and failure (temperature, stress, grain size), and mechanisms of creep deformation including diffusion, dislocation movement, and grain boundary sliding. It provides an overview of creep analysis and the importance of considering creep for materials used in high-temperature applications like gas turbines.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    99 views5 pages

    Experiment Name: Creep Analysis and Case Study

    Uploaded by

    Jessia Alam
    Creep is the tendency of a solid material to slowly deform over time under the influence of a constant mechanical load or stress, especially at high temperatures. The document discusses the different stages of creep (primary, secondary, tertiary), factors that influence creep rates and failure (temperature, stress, grain size), and mechanisms of creep deformation including diffusion, dislocation movement, and grain boundary sliding. It provides an overview of creep analysis and the importance of considering creep for materials used in high-temperature applications like gas turbines.

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    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
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    Experiment Name: Creep Analysis and case study.

    Abstract: Creep is the tendency of a solid material to move slowly or


    deform permanently under the influence of constant mechanical load
    or stress at high temperature. The manufacturing process or factory
    where work is done at higher temperature that requires materials
    which can resist tat temperature and can work properly . like gas
    turbine , nuclear reactor, chemical industries etc. If we neglect the
    effect of creep , a great number of high temperature failure can occur.

    Introduction: There are mainly two types of degradation occurs at high


    temperature :

    i. Mechanical Degradation

    ii. Chemical Degradation

    Creep is mainly Mechanical Degradation. Time dependent permanent


    deformation under a constant load at high temperature is known as
    creep. Creep failure stress have as lower value than yield stress.

    If the working temperature for metal is 0.5T m <T<Tm , there is a higher


    possibility of creep, for glass and ceramic T>Tg

    Time dependent recoverable deformation under load is called anelastic


    deformation, the characteristic recovery of temporary deformation
    after removal of load as a function of time which is called elastic
    aftereffect.
    Figure: Anelastic behavior

    Creep Curve (ST diagram):


    A typical creep curve indicates three different regions:

    i.Primary Region : Once the material experiences an instantaneous


    strain, ɛ0, which is combination of elastic (recoverable on release of
    load), anelastic (recovers with time) and plastic (nonrecoverable) strain.
    As a result of sudden loading, the primary creep region begins only
    after that. As the name suggests primary creep region describes the
    initial stage of creep deformation. This is region of decreasing creep
    rate.

    ii.Secondary Region: Primary creep continues untill the secondary stage


    starts. The strain rate of deformation remains nearly constant during
    the secondary creep region. The strain rate in secondary stage is the
    minimum strain rate of a creep deformation. The creep life of any
    material can be estimated through the knowledge of the creep strain
    rate in secondary stage.

    iii.Tertiary region: The last stage of creep deformation is the tertiary


    creep regime. In this stage, the material undergoes very high strain
    rate, deformation and eventually fractures. This is region of increasing
    creep rate.

    If we increase stress level creep life will decrease.

    Creep Rapture: Creep rupture occurs when

    i. Applied stress is high.

    ii. strain level is large (50%)


    Temperature Effect on Creep Rapture:

    T1< T2 <T3

    Creep Mechanism:

    i. Diffusion Creep: Applied stress > diffusion > vacancy moves from
    perpendicular grain about stress axis to the parallel grain > grain
    elongated along stress axis > deformation

    Creep rate decreases as grain size increases.

    ii. Dislocation creep:

    cause by movement of dislocations,strong dependence on applied


    stress. That involves moment of dislocations which overcomes barriers
    by thermally assisted mechanism involving the diffuision of vacancies or
    interstitials.

    Stress level increase > strain hardening


    iii. Dislocation Glide: Dislocation climb is replaced by dislocation glide
    at higher temperature. That involves dislocation moving along slip
    plane and overcoming barriers by thermal activation, occurs at high
    stress level.

    iv.Grain Boundary Sliding: The sliding grains pass each others. That
    allos material to extant in length with no net change in grain size.

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