Energy response of S355 and 41Cr4 steel during fatigue crack growth process

Abstract

In this research, a novel approach of the fatigue crack growth rate description has been proposed. Based on theoretical and experimental approach, the mean stress effect expressed by R-ratio is present in classical da/dN-DK diagram. According to energy approach-based on the irrevocably dissipated energy accumulated in material (hysteresis loop) during fatigue process-the mean stress effect can be minimalized. Experimental validation of the proposed model was performed using results of fatigue crack propagation data for S355 and 41Cr4 steels in terms of strain energy density parameter DS or cyclic J-integral range-DJ. In contrast to the force approach based on K max (or DK), the energy parameters DS or DJ represent unambiguously the fatigue crack propagation rate, without influence of mean stress effect-R-ratio. However, in near threshold range of kinetic fatigue fracture diagram, the energy parameter displays a slight dispersion of the experimental data. According to the crack closure theory and its U-Elber parameter, the dispersion of experimental data is decreased. Therefore, the crack closure effects have a high significance in energy model-similar to the 'force approach' based on DK concept.

Fatigue Crack Growth Rate in Long Term Operated 19th Century Puddle Iron

“…One of the promising approaches is the energy approach proposed in refs. [11,12]. In the range of linear fracture mechanics a similar effect (R-ratio avoidance) was achieved as for effective ∆ using ∆ * [11].…”

Profile and Areal Surface Parameters for Fatigue Fracture Characterisation

“…Researchers have studied the characteristics of fractured surfaces using observational tools, from macro- to nanoscale [ 13 , 14 , 15 , 16 , 17 ]. Unfortunately, even though advanced methods such as optical coherence tomography [ 18 ], scanning acoustic microscopy [ 19 ] or energy response approach based on strain energy density histories during variable loading [ 20 , 21 ] are described in the literature, usually simple-fracture qualitative analysis conducted with scanning electron microscopy is employed for the evaluation of surface fractures resulting from impact [ 22 , 23 ], tensile strength [ 24 , 25 ], fatigue [ 5 , 19 ], ultra-high fatigue [ 26 ], adhesion testing [ 27 ] or even wear damage description [ 28 , 29 ]. However, few studies have investigated the use of profile and surface roughness as a tool for fatigue fracture characterisation.…”

Fatigue-Induced Evolution of AISI 310S Steel Microstructure after Electron Beam Treatment

“…For instance, fatigue fracture of metals and propagation of fatigue cracks depend on stress levels and rates, surface roughness, heterogeneity of microstructure, etc. To an extent, all of these factors are relevant for the growth of fatigue cracks [ 1 , 2 , 3 , 4 , 5 , 6 ].…”