Fracture Fatigue Entropy Determination

A method for determining the fracture fatigue entropy (FFE) of a metallic specimen subject to cyclic loading, comprising:

• a. monitoring the surface temperature of the specimen over time;
• b. continuing the cyclic loading of the specimen until a fatigue fracture occurs;
• and,
• c. calculating the FFE for the material using the following equation:
• FFE=∫0tf(Wp/T)dt,
• where:
• FFE represents the fracture fatigue entropy for the material;
• tf is time from the beginning of the cyclic loading until the fatigue fracture occurs;
• Wp is cyclic plastic energy for the material;
• and, T is the surface temperature of the specimen.

An apparatus for monitoring the accumulated fatigue entropy of a metallic specimen subject to cyclic loading, comprising:

• a. a temperature monitoring device configured to determine the surface temperature of the specimen;
• b. a temperature input interface that receives temperature data from the temperature monitoring device;
• c. a computing means that receives a temperature signal from the temperature input interface and produces an accumulated fatigue output signal based on the following calculation,
• γ=∫0t(Wp/T)dt,
• where:
• γ represents the accumulated fatigue entropy;
• t is time;
• Wp is cyclic plastic energy;
• and, T is the surface temperature of the specimen.