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College Park, Maryland      June 6 - 10 , 2004

MP31: Residual Strain Distribution around Luders Bands

Y. Sun, B. Yang, T. A Saleh, B. L. Benson, P. K. Liaw (Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996, USA.), H. Choo (Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996, USA.; Metals and Ceramics Division, Oak Ridge National Laboratory), M. R. Daymond (ISIS, Rutherford Appleton Laboratory), J. Y. Huang, R. C. Kuo (Institute of Nuclear Energy Research (INER), P. O. Box 3-14, 1000 Wenhua Road, Chiaan Village, Lungtan, Taiwan 325, Republic of China), J. G. Huang (Taiwan Power Company, Taipei, Taiwan)

Lüders bands often indicate the onset of the plastic deformation at the vicinity of stress concentrations and inclusions, which may contribute to the crack initiations. Investigating the evolution process of Lüders bands will help understand the early stages of the mechanical damage behaviors. In the current research, Lüders bands have been developed on the plate samples of reactor pressure vessel (RPV) steel during fatigue tests. In-situ thermography detection technique has been applied to control the amount of plastic deformation created by the Lüders bands. Two specimens with different amount of plastic deformation (with plastic strains of 1.25% and 1.83%) were prepared. Residual-strain distributions inside and outside the Lüders bands have been measured by neutron diffraction technique in various directions using ENGIN-X instrument at the ISIS Facility. Inside the Lüders bands, compression residual strain has been detected in the gauge-length direction, while tensile residual strain has been detected in the gauge-width direction. Outside the Lüders bands, the residual strains were close to zero. Based on the neutron results, theoretical models to provide better understanding of the Lüders-bands evolution processes have been attempted.

Acknowledgement: We would like to give thanks to (1) The National Science Foundation (NSF) International Materials Institutes (IMI) Program, Under DMR-0231320. (2) Combined Research-Curriculum Development (CRCD) Program, under EEC-9527527 and EEC-0203415. (3) The Integrative Graduate Education and Research Training (IGERT) Program, under DGE-9987548, with Dr. C. Huber, Ms. M. Poats, Dr. W. Jennings and Dr. L. Goldberg, as the contract monitors, respectively. (4) Mr. D. Fielden who machined the samples and grips for us.

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