Fatigue life prediction of notched components based on a new nonlinear continuum damage mechanics model

Abstract

A CDM (continuum damage mechanics) model for damage evaluation is here considered and applied to the study of two different typologies of notched and cylindrical specimens. The model presents some parameter and authors determined them in a previous work testing cylindrical and smooth specimens. Firstly fatigue characterization was conducted and the SN curves found. In order to evaluate the capability of CDM model to predict the sequence effect and to simulate a more realistic loading condition, tests with various loading blocks were carried on and in particular high-low, low-high and random blocks were applied to the three specimens considered. Model previsions showed good agreement with results for each geometry considered. Keywords: Continuum damage mechanics; variable amplitude fatigue; load sequence effect. Nomenclature D damage variable n i number of cycles at a given stress amplitude N i number of cycles to failure at a given stress amplitude max maximum stress m mean stress a stress amplitude, a = max -m M 0 , coefficients of the damage model ( ) function in the damage model H, a coefficients of function ( ) defined as x = 0 if x < 0, x = x if x > 0

Experimental investigation and life prediction of hot corrosion pre‐exposure on low‐cycle fatigue of a directionally solidified nickel‐base superalloy

“…Several researchers [22][23][24][25] assume that the initial value of fatigue damage is zero. This value may be reasonable for unexposed conditions but unsuitable for pre-exposed conditions.…”

“…Continuum damage mechanics (CDM) are widely used for the determination of material failure because of creep, fatigue and particularly creep–fatigue interaction . The purpose of this study is to develop a new methodology based on the CDM method with which to investigate the HTHC fatigue life of a directionally solidified (DS) nickel‐base superalloy.…”

“…creep, fatigue and particularly creep-fatigue interaction. [20][21][22][23][24][25] The purpose of this study is to develop a new methodology based on the CDM method with which to investigate the HTHC fatigue life of a directionally solidified (DS) nickel-base superalloy. Specifically, reductions in effective bearing area are used to describe the effect of hot corrosion damage, and the Chaboche model is applied to characterise the fatigue life of the alloy.…”

Influence of superimposed VHCF loadings in cyclic fatigue of 7075-T6 aluminum alloy

“…12 One of the purposes of the critical tests developed in this study was to evaluate the validity of Miner's rule, in relation to the strain-life curve chosen, when a very large number of fatigue cycles, below the endurance stress for a material, are superimposed to a larger amplitude duty cycle. Several studies confirmed that the sequence of loading events is critical in fatigue, 13 and that when low amplitude duty cycles follow highly damaging events or sequences, they contribute more significantly to the damage in the material. Figure 8 shows the calculated Miner's summation for the test data shown in the previous sections.…”

Fatigue and ratcheting assessment of AISI H11 at 500°C using constitutive theory coupled with damage rule

“…Besides, damage initiation is dependent on plastic deformation; thus, higher mean stress and amplitude generate shorter lifetime before damage initiation and higher damage rate as well as shorter whole life. Based on achieved stabilized damage rate dD/dN, fatigue lifetime is calculated by using Equation 23: The lifetime prediction is shown in Table 6 and Figure 11, where N 0 is the predicted damage-initiation lifetime and N r is predicted damage-evolution lifetime, while N f and N ft are the experimental lifetime and the predicted whole lifetime, respectively. The comparison shows that all the data are located between twice-error bands; thus, the proposed method in this work is promising and reasonable.…”