IntermediateTopic 46 of 106Engineering Mechanics

Hooke's law

In the elastic range stress is proportional to strain, σ=Eε.

In depth

Within the elastic region stress is proportional to strain, σ=Eε, and the material returns to its original shape when unloaded. For springs F=kx. Generalised Hooke's law relates all stress and strain components with E and ν.

Key points

  • Linear elasticity assumption
  • Superposition valid
  • Fails beyond yield
Example

Steel with E=200 GPa under 100 MPa strains by 0.05%.

Why it matters

Hooke's law is valid in the elastic range and lets you predict deformation from load with a simple proportion.

Where this is used

  • Predicting the stretch of a spring under a known load.
  • Calculating the stress in a bar for a measured strain.
  • Modelling the response of a rubber mount in the linear region.

Frequently asked questions

What is Hooke's law?

In the elastic range stress is proportional to strain, σ=Eε.

Why is it important to understand hooke's law?

Hooke's law is valid in the elastic range and lets you predict deformation from load with a simple proportion.

Where does Hooke's law stop being valid?

It stops at the proportional limit and yield point, where permanent deformation starts and the stress is no longer proportional to strain.

Does Hooke's law apply to all materials?

Most metals and ceramics are linear in the elastic range, but rubbers and soft tissues are strongly nonlinear.

How is Hooke's law used in practice?

Typical applications include predicting the stretch of a spring under a known load, calculating the stress in a bar for a measured strain and modelling the response of a rubber mount in the linear region.

What should I learn before Hooke's law?

Study "Stress-strain curve" first (topic 45 of 106 in Engineering Mechanics). It covers the groundwork this topic builds on.

What are the key points of Hooke's law?

Linear elasticity assumption. Superposition valid. Fails beyond yield.

Can you give an example of Hooke's law?

Steel with E=200 GPa under 100 MPa strains by 0.05%.

What comes after Hooke's law?

The next topic is "Young's modulus", which builds directly on this one.

How difficult is Hooke's law?

It is classed as Intermediate in Engineering Mechanics (topic 46 of 106). It is an intermediate topic. Work through the beginner topics in Engineering Mechanics first.

Learning path

Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.