Discussion: “A Critical Analysis of Crack Propagation Laws” (Paris, P., and Erdogan, F., 1963, ASME J. Basic Eng., 85, pp. 528–533)

Comparative evaluation of fatigue life estimation under variable amplitude loading through damage models based on entropy

“…Based on the theoretical background above referred and experimental results, Naderi et al 19 established a relation between the generated entropy and the cycles to failure, assuming a linear entropy accumulation to the point of fracture. The relation by Naderi et al, 19 considered linear for practicality, is shown in Equation (7), where s g is a property of the material known as FFE, which is a constant value independent of the frequency, load, and specimen size. Considering that the FFE is a constant value as a solid fact, they proposed a new methodology for the prediction of fatigue life based on the measurement of the thermodynamic entropy generation.…”

“…Since the first research concerning the fatigue of materials was conducted by August Wöhler, who proposed the stress-life curves, many models for the estimation of fatigue life have been developed, most of them based on experimental work, such as those developed by Basquin, 2 Miner, 3 Tavernelli and Coffin and Mason, 4,5 and Paris and Erdogan and Anderson. 6,7 The models presented by these authors are among the most popular ones and are only a sample of the works proposed for the estimation of fatigue life. However, none of them have received universal acceptance, as they sacrifice their applicability range in favor of gaining precision, generating the next challenges 8 : (a) prediction of useful life under multiaxial and variable amplitude loading histories, (b) data transfer from small test specimens to real machine elements and structures, (c) the influence of corrosion and creep, (d) as well as the best probabilistic distribution and treatment of the dispersions observed experimentally.…”

“…Since the first research concerning the fatigue of materials was conducted by August Wöhler, who proposed the stress‐life curves, many models for the estimation of fatigue life have been developed, most of them based on experimental work, such as those developed by Basquin, 2 Miner, 3 Tavernelli and Coffin and Mason, 4,5 and Paris and Erdogan and Anderson 6,7 . The models presented by these authors are among the most popular ones and are only a sample of the works proposed for the estimation of fatigue life.…”