Authors:
Markus Schneider (1), Dennis Wawoczny (1, Kevin Haffke (1)
1- GKN Powder Metallurgy Engineering GmbH, Radevormwald, Germany
Abstract:
Ceramics and intermetallic compounds, e.g. sintered Nd2Fe14B hard magnets, are hard and brittle. The lack of any macroscopic plasticity yields to the fact that all defects exhibit its sharpest effect as predicted with the methods of the classical Linear Elastic Fracture Mechanics (LEFM) and Neuber’s theory of notch stresses. Residual stresses from the processing do not relax. The lack of any peak stress or stress intensity reducing plasticity explains its stronger scattering and Probability Density Function’s (PDF) loss of symmetry. The PDF of common ceramics are skewed and broader which leads to the need to consider the whole PDF and to define local component strength values. This refers to Weibull’s “weakest link theory”. Two different Nd2Fe14B hard magnet grades were tested and corresponding characteristic strength values and Weibull moduli were derived. The Weibull moduli can be used to predict the “size effect” or “volume effect” of the strength.
DOI:
https://doi.org/10.59499/EP246319979
