Materials scienceLesson 5 of 5 in the course Composites and mechanical behaviour

Creep in Materials: Stages, Mechanisms, and Engineering Control

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson introduces creep as a time-dependent form of deformation and explains why engineers must consider it when designing components under sustained loads.

Creep, sometimes called cold flow, is the gradual deformation of a solid under a persistent mechanical stress. It can occur even when the stress is below the material’s yield strength. Unlike brittle fracture, which can occur suddenly, creep strain builds up over time while the load remains applied.

All flashcards

Creep
Gradual deformation of a solid under sustained stress, which can occur even below its yield strength.
Tertiary creep
The stage in which strain rate accelerates, often as necking, cracks, or voids reduce the effective cross-sectional area.
Deformation mechanism map
A map showing which deformation mechanism is expected to dominate under specified material conditions.
Harper–Dorn creep
A low-stress, climb-controlled dislocation mechanism with weak stress dependence and approximate independence from grain size.
Blocking agent
An additive used to inhibit the sticking of plastic sheets caused by polymer cold flow.

Quiz questions

  1. What characterizes secondary, or steady-state, creep?Answer: The strain rate remains approximately constant.
  2. How does Coble creep differ from Nabarro–Herring creep?Answer: Coble creep occurs along grain boundaries and has a stronger grain-size dependence.
  3. Which mechanism commonly controls deformation at high stress relative to the shear modulus?Answer: Dislocation creep
  4. Which quantities commonly form the axes of a deformation mechanism map?Answer: Homologous temperature and stress normalized by shear modulus
  5. Why can single-crystal turbine blades resist some high-temperature creep processes?Answer: They avoid grain boundaries that can contribute to deformation.

Based on the Wikipedia article Creep (deformation), licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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