## Abstract

A method is proposed for simplified nondestructive evaluation of multiple cracks by means of measurement of magnetic field produced in the air by d. c. current flow in a material. First approximate equation which relates the change in magnetic flux density due to a 3-D surface crack to the crack length and crack depth is derived based on the results of the numerical analysis. The equation is the basis of developing a method for simplified nondestructive evaluation of 3-D multiple cracks. Next the equation for multiple cracks is expressed as the sum of the magnetic flux density for a plate without crack, increment of the magnetic flux density due to the respective cracks which is calculated by assuming that the plate contains one of these cracks and a term representing the interaction between these cracks. Finally the inverse problem to evaluate the crack depths is analyzed by comparing the magnetic flux density calculated in this way with the measurement. It is shown that multiple cracks are sized accurately by the present method.

Original language | English |
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Pages (from-to) | 14-21 |

Number of pages | 8 |

Journal | Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A |

Volume | 64 |

Issue number | 617 |

DOIs | |

Publication status | Published - 1998 |

## Keywords

- Inverse problem
- Magnetic field
- Nondestructive inspection
- Numerical analysis
- Simplified evaluation
- Three dimensional multiple cracks

## ASJC Scopus subject areas

- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering