An Optical Gage for Strain/Displacement Measurement at High Temperature Near Fatigue Crack Tips.

摘要

The interferometric strain/displacement gage (ISDG) relates the motion of fringe patterns generated by a laser beam impinging upon closely-spaced indentations to local surface deformation. The purpose of this research was to extend the technique to real-time crack tip opening displacement (CTOD) and biaxial strain measurements on superalloys at high temperatures. The indentations must remain reflective at temperature; they can be protected with a coating. A coating was developed to protect Incolloy 901 for several hours at 650 C. IN-100 will remain reflective if it is preoxidized in an rf furnace, but an electroplated chromium and vapor-plated platinum coating produces better fringe patterns.