DIFFERENTIAL DISPLACEMENT MEASUREMENT USING SCANNING-X-RAY BEAMS

A noncontacting method for measuring mechanical strain between two fid ucial marks has been developed for use when environmental conditions w ould be disruptive to methods utilizing optical light. A silicon 111 J ohansson crystal is used for this application when Mo K alpha radiatio n is used to fluoresce fiducial markers made of yittria-stabilized zir conia, This substance is used for a thermal barrier costing in gas tur bine engines and the technology for applying this material to withstan d long term high temperature exposure is highly developed. The current system has a displacement repeatability of better than 0.1 mu m which is not limited by counting statistics, but rather determined by mecha nical considerations. (C) 1998 American Institute of Physics.