Mechanical, pressure and integrity

Fatigue and fracture mechanics

Crack growth, endurance and weld fatigue assessment for cyclically loaded equipment.

Describe your project

What it covers

Fatigue and fracture mechanics assesses how cyclic loads, welds and pre-existing flaws affect the life of a component. It covers stress-life and strain-life fatigue, weld fatigue to the relevant code, fracture mechanics and crack growth, and the critical flaw size that drives inspection. The engineer establishes the loading spectrum, the stress concentrations and the material data, then predicts crack initiation or growth and a safe operating or inspection interval.

When you need it

You need fatigue and fracture analysis when a component sees repeated loads, vibration, thermal cycling or pressure cycling, when a weld or detail has cracked, or when a fitness-for-service assessment finds a crack-like flaw. It is also part of design-by-analysis for pressure equipment that cycles.

Standards, codes and tools

BS 7910AS 4100ASME VIII Div 2 Part 5API 579-1/ASME FFS-1

Commonly used tools: nCode DesignLife, Ansys, Abaqus, Fe-safe.

What to look for

Look for an engineer who distinguishes crack initiation from crack growth and who can tie the analysis to a real loading spectrum, not a single load case. Ask whether they work to BS 7910 for fracture and the relevant fatigue code for welds. The output should be a life or an inspection interval you can act on, with the assumptions stated.

Common questions

What is the difference between fatigue and fracture analysis?

Fatigue analysis predicts how many load cycles a detail can take before a crack starts or grows. Fracture mechanics predicts whether an existing crack will grow and what flaw size is critical. The two are often used together to set a safe inspection interval.

What is a fatigue spectrum and why does it matter?

A fatigue spectrum is the real sequence of load ranges a component sees in service. Fatigue life is very sensitive to it, so an assessment built on the actual spectrum is far more reliable than one based on a single assumed load.

Need fatigue and fracture mechanics?

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