Evaluation of NDT-signals for use in the fracture mechanics safety analysis

Kern, Torsten-Ulf; Ewald, J.; Maile, Karl

doi:10.1080/09603409.1998.11689587

Cited by 14 publications

(1 citation statement)

References 2 publications

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“…These inclusions can range from several micrometers to a few hundred micrometers in diameter [3] depending on the specifics of the manufacturing processes and materials involved. If these clusters are large enough, typically a millimeter or larger, then they might be detected by ultrasonic testing [4][5][6]. These unavoidable manufacturing imperfections need to be accounted for in engineering life prediction methods, for both new apparatus and service applications.…”

Section: Introductionmentioning

confidence: 99%

Crack nucleation at forging flaws studied by non-local peridynamics simulations

Karim

Kadau

Narasimhachary

et al. 2021

Mathematics and Mechanics of Solids

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We present a computational study and framework that allows us to study and understand the crack nucleation process from forging flaws. Forging flaws may be present in large steel rotor components commonly used for rotating power generation equipment including gas turbines, electrical generators, and steam turbines. The service life of these components is often limited by crack nucleation and subsequent growth from such forging flaws, which frequently exhibit themselves as non-metallic oxide inclusions. The fatigue crack growth process can be described by established engineering fracture mechanics methods. However, the initial crack nucleation process from a forging flaw is challenging for traditional engineering methods to quantify as it depends on the details of the flaw, including flaw morphology. We adopt the peridynamics method to describe and study this crack nucleation process. For a specific industrial gas turbine rotor steel, we present how we integrate and fit commonly known base material property data such as elastic properties, yield strength, and S-N curves, as well as fatigue crack growth data into a peridynamic model. The obtained model is then utilized in a series of high-performance two-dimensional peridynamic simulations to study the crack nucleation process from forging flaws for ambient and elevated temperatures in a rectangular simulation cell specimen. The simulations reveal an initial local nucleation at multiple small oxide inclusions followed by micro-crack propagation, arrest, coalescence, and eventual emergence of a dominant micro-crack that governs the crack nucleation process. The dependence on temperature and density of oxide inclusions of both the details of the microscopic processes and cycles to crack nucleation is also observed. The results are compared with fatigue experiments performed with specimens containing forging flaws of the same rotor steel.

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