physics

Ratcheting

Ratcheting is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Ratcheting rather than just read about it. In short: In continuum mechanics, ratcheting, or ratchetting, also known as cyclic creep, is a behavior in which plastic deformation accumulates due to cyclic mechanical or thermal stress. In an article written by J.

Key takeaways

Ratcheting belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Ratcheting to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Ratcheting from memory before moving on to harder problems.

Reference excerpt

In continuum mechanics, ratcheting, or ratchetting, also known as cyclic creep, is a behavior in which plastic deformation accumulates due to cyclic mechanical or thermal stress. In an article written by J. Bree in 1967, the phenomenon of ratcheting is described as "Unsymmetric cycles of stress between prescribed limits will cause progressive 'creep' or 'ratchet(t)ing' in the direction of the mean stress". Ratcheting is a progressive, incremental inelastic deformation characterized by a shift of the stress-strain hysteresis loop along the strain axis. When the amplitude of cyclic stresses exceed the elastic limit, the plastic deformation that occurs keep accumulating paving way for a catastrophic failure of the structure. Nonlinear kinematic hardening, which occurs when the stress state reaches the yield surface, is considered as the main mechanism behind ratcheting. Several factors influences the extent of ratcheting including the load condition, mean stress, stress amplitude, stress ratio, load history, plastic slip, dislocation movement, and cells deformations. The effect of structural ratcheting can sometimes be represented in terms of the Bree diagram. Alternative material models have been proposed to simulate ratcheting, such as Chaboche, Ohno-Wang, Armstrong–Frederick, etc. Ratcheting is a significant effect to be considered to check permanent deformation in systems which undergoes a cyclic loading. Common examples of such repetitive stresses include sea waves, road traffic, and earthquakes. Initially it was studied to inspect the permanent deformation of thin, nuclear fuel cans with an internal pressure and temperature gradient while undergoing repetitive non-zero mean stresses.

References

Worked examples

Example 1 — a first encounter with Ratcheting

Start with the simplest possible case. Write down what Ratcheting claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Ratcheting before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Ratcheting ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Ratcheting

In research: Ratcheting appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Ratcheting in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Ratcheting is common in secondary-school and first-year university syllabi. It links to neighbouring topics Continuum mechanics, Deformation (mechanics), Plasticity (physics), so understanding it makes those chapters shorter.
In everyday life: Look for Ratcheting outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Ratcheting in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Ratcheting means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Ratcheting out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Ratcheting in simple terms?

Why does Ratcheting matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Ratcheting?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Ratcheting.