Plasticity, Yielding, and Work Hardening
Plasticity refers to a material’s ability to undergo permanent deformation without breaking when subjected to stress. Yielding is the point at which a material begins to deform plastically, meaning it will not return to its original shape when the stress is removed. Work hardening, or strain hardening, occurs when a material becomes stronger and harder as it is deformed plastically, due to the rearrangement of its internal structure.
Plasticity, Yielding, and Work Hardening
Plasticity refers to a material’s ability to undergo permanent deformation without breaking when subjected to stress. Yielding is the point at which a material begins to deform plastically, meaning it will not return to its original shape when the stress is removed. Work hardening, or strain hardening, occurs when a material becomes stronger and harder as it is deformed plastically, due to the rearrangement of its internal structure.
💡 Key Takeaways
- Define plasticity and yielding and distinguish elastic from plastic deformation
- Explain yield strength and the onset of plastic deformation
- Describe how dislocations enable plastic deformation in metals
- Summarize work hardening (strain hardening) and its effect on material strength
- Identify factors that influence plasticity and yield, such as temperature, strain rate, and microstructure
❓ Frequently Asked Questions
What is plasticity?
Plasticity is the ability of a material to undergo permanent, irreversible deformation after the elastic limit is exceeded.
What does yielding mean on a stress-strain curve?
Yielding is the onset of plastic deformation: the material starts to deform permanently once the yield stress is reached.
What is yield strength and how is it defined?
Yield strength is the stress at which a material begins to plastically deform. It is often defined by a 0.2% offset criterion.
What is work hardening (strain hardening)?
Work hardening is the increase in a material's strength with plastic deformation, caused by dislocation interactions that hinder further motion.
How do dislocations contribute to plastic deformation and work hardening?
Plastic deformation occurs mainly by dislocation glide; as dislocations multiply and interact, the material becomes harder to deform, leading to work hardening.