Calibration and evaluation of the Lemaitre damage model using axial- torsion fatigue tests on five engineering alloys

Abstract

The Lemaitre damage model is evaluated using fatigue test data from five engineering alloys: 1045 steel, 16MnR steel, 7075-T651 Al alloy, extruded AZ61A Mg alloy, and extruded AZ31B Mg alloy. Tension-compression, torsion, proportional axial-torsion, and 90° out-of-phase axial-torsion loadings were investigated. The results show that the overall accuracy of the fatigue life estimates made by using the Lemaitre model is comparable to those obtained by fatigue models that require the definition of a loading cycle. A simple and effective method is described for determining the material constants of the Lemaitre model.

An improved continuous damage model to estimate multiaxial fatigue life under strain control problems

“…Analyzing Figure 2, it can be seen that the function of Malcher and Mamiya (2014) does not present a strictly increasing behavior when S 0 < S AE 1 3 (Figure 2(a)) and which is also unable to predict the same damage denominator when S 0 ¼ S AE 1 3 (Figure 2(c)). Also according to Figure 2, note that the function of Castro and Bemfica (2018) can assume negative values when S 0 > S AE 1 3 (Figure 2(d)). Finally, it is concluded that the function proposed in this document behaved adequately under all the conditions evaluated, and, therefore, it was used throughout the present manuscript.…”

“…On the other hand, equation (8) presents a denominator of damage function dependent only on the stress triaxiality. This function was proposed by Castro and Bemfica (2018) as a way to improve the results of the torsional fatigue tests. In a tension-compression fatigue test, the stress triaxiality of a smooth cylindrical specimen assumes the values of 13 (tension) and −13 (compression).…”

“…In the context of fatigue life prediction, Castro and Bemfica (2018) proposed a modification in Lemaitre's damage evolution law, creating a denominator of damage function, which is dependent on the stress triaxiality and two cyclic calibration points (tension-compression and torsional tests). Regarding the tests evaluated by Castro and Bemfica (2018), the proposed modification presented good results for fatigue life estimate.…”

“…In the context of fatigue life prediction, Castro and Bemfica (2018) proposed a modification in Lemaitre's damage evolution law, creating a denominator of damage function, which is dependent on the stress triaxiality and two cyclic calibration points (tension-compression and torsional tests). Regarding the tests evaluated by Castro and Bemfica (2018), the proposed modification presented good results for fatigue life estimate. However, it can be highlight that there is not thermodynamic consistency, due to the denominator of damage function proposed by the authors assumes negative values, which can result in a negative dissipation of energy, violating the laws of thermodynamics.…”

Preface to the special issue of the International Symposium on Solid Mechanics (MecSol 2017)

“…• Structural Reliability Methods and Reliability-Based Design Optimization: Multi-objective optimization (Passos and Luersen, 2018) and experimental crack identification (Oliveira Filho et al, 2018). • Multiaxial and Fretting Fatigue: identification of fatigue limits and continuum damage mechanics (Castro and Bemfica, 2018), stress-life curves for alloy steels (Duran et al, 2018) and assessment of fatigue limits (Bandeira et al, 2018).…”