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Ca Ch Cm Co Cr

Crack growth

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Definition: Crack growth refers to the progressive propagation of an existing crack under mechanical or corrosive loading. It is described in fracture-mechanics terms using parameters such as the stress intensity factor ΔK or the J-integral. Under cyclic loading, the growth often follows the Paris law.

Practical relevance: Crack growth largely determines the remaining service life of cracked components. Influencing factors are stress amplitude, mean stress, material toughness, temperature and medium. Quantitative assessment is carried out using da/dN-ΔK curves. Applications are found in pressure equipment construction, structural steelwork and aviation.

Decision-making perspectives:

  • Technical decision-makers: Definition of permissible crack sizes and inspection intervals.
  • Purchasing/project management: Assessment of repair or replacement strategies based on remaining-service-life analyses.
  • Science: Investigation of fatigue crack propagation and environmental influences.
  • Insurance/law: Demonstration of whether a crack would have been controllable with proper monitoring.

Typical testing or verification methods: Fatigue crack growth test, fracture-mechanics assessment to DIN EN ISO 12108, non-destructive crack testing.

FAQ:

  • What does the Paris law describe?
  • It describes the relationship between the crack growth rate (da/dN) and the stress intensity factor range (ΔK) under cyclic loading.
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