14. Design and Installation Considerations of Dynamic Strain Gages for Thermo-Acoustic Aerospace Structures Test

Traditional polyamide film strain gages designed for high temperature applications have a survivable temperature threshold of 500–600 degrees F. Free-Filament (platinum) strain gages offer dynamic strain response with a temperature threshold up to 1800 degrees F. There are challenges using free-filament strain gages including providing robust installation methods, attachment leads, and signal conditioning. These factors are often overlooked and if not correctly addressed will give poor or incorrect responses. Standard adhesives and solder used to attach the strain gage and wire attachment leads break down at similar temperatures as polyamide film gages and are not well suited to use with free-filament gages. This paper will discuss ceramic flame spraying techniques using alumina or other high temperature bonding agents providing a robust and stable attachment. In addition, the use of, Nextel insulated, Constantan wire leads to withstand the high temperatures and direct radiation in high temperature dynamic testing environments will be addressed.