Dynamic shear bands: an investigation using high speed optical and infrared diagnostics
This paper presents an experimental investigation of the initiation and propagation characteristics of dynamic shear bands in C300 maraging steel. Pre-fatigued single edge notched specimens were impacted on the edge under the notch to produce shear dominated mixed mode stress fields. The optical technique of coherent gradient sensing (CGS) was employed to study the evolution of the mixed mode stress intensity factors. Simultaneously, a newly developed two-dimensional high speed infrared (IR) camera was employed to observe the temperature field evolution during the initiation and propagation of the shear bands. Possible criteria for failure mode selection are discussed. The IR images, for the first time, revealed the transition of crack tip plastic zone into a shear band and also captured the structure of the tip of a propagating shear band. These thermographs support the notion of a diffuse shear band tip and reveal "hot spots" distributed along the length of a well-developed shear band.
© 2001 Elsevier Science Ltd. Received 10 October 2000; received in revised form 27 November 2000. This work was supported by the Office of Naval Research grant # N00014-95-1-0453 (Dr. Y.D.S. Rajapakse, project manager) and the engineering research program of the office of Basic Energy Sciences at the Department of Energy through grant No. DE-F603-95ER14560 (Dr. Robert Price, Project officer). Additional funding for the development of the infrared camera was provided by the National Science Foundation through the Center for Quantitative Visualization at Caltech (Professor M. Gharib, Director). We are also pleased to acknowledge the contributions of Professor A.T. Zehnder, Cornell University, for his pivotal role in developing the high speed IR camera. PRG acknowledges many useful discussions with Dr. David M. Owen, Caltech throughout this work.