Micro-Measurements offers special sensors to provide a method for determining the rate of crack propagation in a test part or structure.
Four crack propagation patterns are available, each made with parallel resistor strands. When bonded to a structure, the progression of a surface crack through the gage pattern causes successive open-circuiting of the strands, resulting in an increase in total resistance. The patterns produce stepped increases in resistance by successive open-circuiting.
Crack propagation gages are made with a high-endurance Karma alloy foil backed with a glass-fiber-reinforced epoxy, providing for an operational temperature range of –452°F [–269°C] to +450°F [+230°C]. The grid construction allows for a single cycle strain range of up to ±1.5% with a fatigue life of greater than 107 cycles at ±2000 µɛ.