Load path sensitivity and fatigue life estimation of 30CrNiMo8HH

Abstract

A set of strain-controlled biaxial proportional and non-proportional tests were conducted on solid and tubular specimens of 30CrNiMo8HH steel. The effect of the phase angle on fatigue life was studied. This effect becomes noticeable when applying a 90° out-of-phase loading, reducing the fatigue life by a factor up to 5. It has been shown that the material has no additional hardening due to out-of-phase loading. To account for this severe path dependency, a material dependent non-proportionality modification factor is proposed. This path dependent sensitivity factor is applied to six different fatigue parameters including maximum equivalent total strain, maximum equivalent stress, Smith-Watson-Topper, Fatemi-Socie, plastic strain energy density and total strain energy density to correlate the fatigue results. The predicted fatigue lives are compared with the experiments. The cyclic plasticity models of Mroz and Chaboche were successfully employed to model the cyclic behavior of 30CrNiMo8HH steel. It has been shown that estimations based on the proposed non-proportionality modification factor agree well with the experimental results. ____________________________

Cyclic hysteresis of AZ31B extrusion under load‐control tests using embedded sensor technology

“…24,7 There has been a wide range of research in predicting the life, or performing notch analysis of different material under cyclic loads using the stress-strain hysteresis. [29][30][31][32][33][34][35][36][37][38] Among those, models based on plastic and elastic strain energy densities have shown promising results in predicting the life of magnesium alloys (see Albinmousa and Jahed 11 for a review on energy-based fatigue life model in magnesium alloys). Using the obtained VMP-FBG hysteresis, the fatigue lives of the samples were estimated based on the energy method for three different bending moments: 2.5 Nm, 5.0 Nm and 6.5 Nm.…”

A fatigue model for sensitive materials to non-proportional loadings

“…According to the reported results in [11], 30CrNiMo8HH is a sensitive material to non-proportional loading. Comparison between predicted and experimental lives are shown in Fig.9.…”

“…Chen et al [9] proposed non-proportionality factor as ratio of a circle area with a radius equals the maximum shear strain to the swept area by maximum shear strain in different directions in polar coordinates. Fatigue models do not predict a higher level of damage under non-proportional loadings than proportional loadings [10][11][12], this leads to over-estimated fatigue life for nonproportionality sensitive materials under non-proportional loadings [10][11].…”

Stabilized cyclic stress‐strain calculation for metals under multiaxial loading

“…One of the modifications referred to Garud model is used in conjunction with an energy fatigue damage model for non-proportional loading conditions [12][13]. Mróz model and Chaboche model are applied to describe the cyclic behavior of 30CrNiMo8HH steel for various loading paths [11,[14][15]]. The Chaboche model has a better agreement with the experimental results of 30CrNiMo8HH steel [15].…”

“…Mróz model and Chaboche model are applied to describe the cyclic behavior of 30CrNiMo8HH steel for various loading paths [11,[14][15]]. The Chaboche model has a better agreement with the experimental results of 30CrNiMo8HH steel [15]. A nonlinear kinematic hardening relation referred to Armstrong-Frederick model is proposed by introducing a recovery term associated with a strain memory effect [16].…”