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Yield Stress Determination by the Massachusetts Institute of Technology Miniaturized Disk Bend Test

Dong-Seong Sohn, Gordon E. Kohse, David M. Parks, Otto K. Harling

Nuclear Technology

Volume 92 / Number 3 / December 1990 / Pages 383-388


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Considerable effort is currently being expended to develop mechanical property tests for various miniature specimens. Bend tests of thin 3-mm-diam disks (standard transmission electron microscopy specimens) have been used by various workers. A miniaturized disk bend test (MDBT) using a 3-mm-diam x 0.25-mm-thick disk is described and recent progress in extracting uniaxial yield stress values from bend test data is discussed. The method is based on the existence of an initial linear region in the load/deflection curve generated by the bend test. A strong relationship between the load at deviation from linearity and the uniaxial yield stress is found. By simulating observed load/deflection curves using a finite element stress/strain analysis, yield stresses can be calculated from MDBT data. Results using our approach to MDBT for a range of materials are presented, and good agreement with uniaxial tensile test data is shown. These results for the small specimen volume required for MDBT offer interesting possibilities for monitoring the mechanical properties of in-service structures, as well as for minimizing test volumes and specimen radioactivities in such programs as alloy development for irradiation performance in fusion reactors.

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