Papers by Keyword: Paris-Erdogan Law

Abstract: The study is focused on the comparisons among three stochastic fatigue crack growth models through evaluations of experimental data. The first model assumed that the coefficient and exponent parameters of Paris-Erdogan law are mutually dependent normal random variables. The second model assumed that the fatigue crack growth rate equals to the deterministic Paris-Erdogan law multiplied by a stationary log-normal random factor while the third model proposed by the author was assumed that the fatigue crack growth rate equals to a deterministic polynomial in terms of fatigue crack size multiplied by a stationary log-normal random factor. Compact-tension specimens cut from a 2024-T351 aluminum-alloy plate were used for fatigue crack growth experiments under constant loads performed on thirty specimens. The normal probability paper for the first model was investigated to show the validity of the normal random parameter, and the log-normal probability papers for the second and third models were also investigated to show the validity of log-normal assumption of the random factors. The investigations on the probability of crack exceedance and distribution of random time of the three models were also made, and the comparisons of the results for all models were made as well.

Abstract: Attention to the fatigue cracks in steel structures and bridges has been paid for long time. In spite to efforts to eliminate the creation and propagation of fatigue cracks throughout the designed service life, cracks are still revealed during inspections. Note, that depending on location of initial crack, the crack may propagate from the edge or from the surface. The theoretical model of fatigue crack progression is based on linear fracture mechanics. Steel specimens are subjected to various load (tension, three-and four-point bending, pure bending etc.). The calibration functions for short edge cracks are compared for various load and the discrepancies are discussed.

Abstract: The material quality, the deformation rate, the temperature and the stress state influence mechanical behaviour and properties of different materials. Due to this great variety of the influencing factors we do not have one model of general validity describing the behaviour of materials, but we have to use a great number of material constants in order to characterize the properties. The exponents of the Manson-Coffin, the Basquin and the Paris-Erdogan laws were applied for the verification of the connection among the fatigue fracture types. Own measured values and test results can be found in the literature were used for the illustration of the connections. “Fracture surface”-s were determined for characterizing of different steel grades and their welded joints. It can be concluded that “fracture surface”-s are suitable for the describing of the fracture behaviour and the conversion of different fracture parameters of steels.