IN-SITU BEND FIXTURE FOR DEFORMATION AND FRACTURE STUDIES IN THE ENVIRONMENTAL SCANNING ELECTRON-MICROSCOPE

A computer controlled loading fixture has been designed to allow in si tu observation of fracture processes during bending deformation of met al/ceramic microlaminates in an electroscan environmental scanning ele ctron microscope (ESEM). The stage has the capability of accommodating either three- or four-point bending experiments. A unique design feat ure of the stage is that the specimen surface remains at a fixed dista nce from the secondary electron detector and, hence, in focus during b ending. The sample rests on the fulcrum which remains in a fixed posit ion while the restraints that grip the ends of the sample descend on a ball slide. The system is controlled by a Macintosh IIci computer and National Instruments NB-MIO-16L-9 data acquisition card. National Ins truments LabVIEW(R)2 software is used to control the stage displacemen t and to record the load cell and transducer outputs. The operation of this instrumentation in the ESEM is illustrated by the study of fract ure processes in ceramic and ceramic/metal microlaminate films deposit ed on ductile metallic substrates.