Creep Factors
Creep Factors - Related Videos
01:28
Factors Affecting Creep
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2024
In normal-weight aggregate concrete, the hardened cement paste is the primary contributor to creep, whereas the aggregates, being stiffer than the cement paste, are more resilient to stress-induced deformation. The stiffness of the aggregates is defined by their modulus of elasticity, and the more voluminous they are in the concrete, the less it will creep. Further, the water/cement ratio is critical, as a lower ratio increases concrete strength, thus reducing creep. The strength of the...
01:22
Creep in Concrete
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2024
Creep refers to the time-dependent increase in strain under a sustained load, excluding other time-dependent deformations associated with shrinkage, swelling, and thermal expansion in concrete. The primary mechanism behind creep involves the loss of physically adsorbed water from the calcium silicate hydrate within the hydrated cement paste. This process is further exacerbated by concrete's non-linear stress-strain relationship, microcrack development in the interfacial transition zone, and...
01:25
Effects of Creep
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2024
Creep in concrete, the gradual deformation under prolonged stress, significantly impacts the integrity of structures. For reinforced concrete beams, it can be a vital design consideration, as it increases deflection, sometimes necessitating additional design measures. In columns, especially slender ones under eccentric loads, creep can cause buckling, compromising their stability. However, creep can be beneficial in indeterminate structures by mitigating stresses that arise from shrinkage,...
09:51
Measuring Plant Cell Wall Extension (Creep) Induced by Acidic pH and by Alpha-Expansin
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Cited by 43 •
2009
We demonstrate the use of a constant-force extensometer to measure long-term extension (creep) of plant cell wall specimens induced by acidic buffers and expansin protein.
02:16
Transcription Factors
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2019
Tissue-specific transcription factors contribute to diverse cellular functions in mammals. For example, the gene for beta globin, a major component of hemoglobin, is present in all cells of the body. However, it is only expressed in red blood cells because the transcription factors that can bind to the promoter sequences of the beta globin gene are only expressed in these cells. Tissue-specific transcription factors also ensure that mutations in these factors may impair only the function of...
FAQs
Temperature generally accelerates the atomic diffusion and dislocation movement that contribute to time-dependent deformation. Greater applied stress can also increase the creep rate, while longer exposure allows strain and microstructural changes to accumulate. Evaluating these variables together is essential because a component experiencing sustained mechanical loading at elevated temperature may deform substantially over its intended service period.
Grain structure and material composition influence how readily a material undergoes atomic diffusion, dislocation movement, and other microstructural changes. These characteristics can therefore alter the rate at which strain develops under sustained loading. Comparing candidate materials and their internal structures helps engineers identify options better suited to components that must retain shape during prolonged thermal and mechanical exposure.
Progressive creep first appears as accumulated strain, but continued deformation can compromise the component’s ability to carry its load. The same time-dependent processes that change shape may ultimately contribute to rupture when exposure, temperature, and stress remain sufficiently demanding. Considering both strain development and rupture risk gives engineers a more complete view of long-term component reliability.
Engineers assess the expected temperature, sustained stress, exposure duration, material composition, and grain structure for a proposed component. They then use those conditions to estimate long-term strain, stress relaxation, and possible rupture. The resulting assessment informs material selection and safety-factor calculations, helping the design accommodate the anticipated effects of prolonged thermal and mechanical loading.
Creep assessment is especially relevant to turbine blades, pressure vessels, pipelines, and high-temperature fasteners. These components may remain under mechanical load while exposed to elevated temperatures for extended periods. Applying the relevant material, environmental, and loading factors helps engineers anticipate dimensional changes, load redistribution through stress relaxation, and potential loss of service reliability.
Creep analysis can estimate long-term strain, stress relaxation, and the possibility of rupture under sustained conditions. Those outcomes support service-life prediction and help engineers select suitable materials and safety factors. The analysis also indicates whether a design is likely to remain reliable throughout prolonged thermal and mechanical loading, rather than only during its initial operation.