PSI - Issue 46

Robert Basan et al. / Procedia Structural Integrity 46 (2023) 62–67 Robert Basan et al. / Structural Integrity Procedia 00 (2019) 000–000

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Numerous approaches and calculation models and methodologies have been proposed in the literature for dealing with the task of the determination of the load-carrying capacity and durability i.e. fatigue lives of gears and other components operating in rolling-sliding contact loading regime. These range from early, empirical data-based works and simplified calculation models by Pederson and Rice (1961), Sandberg (1981), to those using Von Mises stress as a relevant parameter as in Glodež et al. (1996). Stress-based approach ws used in Zwirlein and Wieland (1983) and strain-based models were used by Šraml et al. (2003) and Šraml and Flašker (2007). More recent approaches for modeling and determining fatigue lives involve critical plane-based fatigue crack initiation criterion originally proposed by Fatemi and Socie (1988). Most recent approaches implement multi-scale i.e. micro-structurally-based fatigue crack initiation modelling as done by Mlikota et al. (2021) and critical resolved shear stress as proposed by Mlikota and Schmauder (2020). Regardless of the actual problem and/or selected approach, one of the greater challenges which is very often encountered and that must be overcome in calculation and analysis of both monotonically and cyclically loaded components is a lack of exact properties of the material that they are made of, which is especially pronounced in cases of heat-treated components in which values of material properties can vary significantly within the component. Experimentally determined materials properties and parameters or detailed materials response are very costly in terms of time and financial means, and testing equipment is usually unavailable. Thus, using existing data and information available from published references or other sources of data are often resorted to. However, another solution can also be considered - using various estimation methods with which needed and missing material data can be estimated based on partially available information on material state, condition and monotonic properties. An example of this is a study on large-diameter slewing bearings of onshore wind turbines made from induction hardened and tempered steel 42CrMo4 done by Friederici et al. (2021) where extensive experimental work was done in order to extract material specimens and then test them in order to characterize the material and where estimation methods could perhaps have been implemented in conjuction with simple non-destructive testing methods which were done. In a failure analysis of a ruptured compressor pressure vessel, Vukelic et al. (2021) use well-known possibility to estimate the ultimate strength of the pressure vessel steel using measured values of Vickers hardness. For potential further studies, estimation of strain-life fatigue parameters can be performed in the similar manner. For the purpose of static and fatigue analyses of coil spring, Pastorcic et al. (2021) also estimate ultimate strength from Vickers hardness while fatigue parameters needed are taken from the available published reference. Papadopoulou et al. (2019) use the fatigue parameters needed for strain-life fatigue analysis from the software for numerical analysis. In this case, possibility of estimating them from monotonic properties might have been explored since the samples of failed roll steel pins were available and hardness measurement might have been measured (and possibly static tensile testing as well). 2. Fatigue life calculation model and materials parameters estimation methods Aim of the present study is to evaluate applicability of estimation methods for analysis of load-carrying capacity and durability of gear teeth flanks. For this, multiaxial fatigue life calculation model comprising mathematical model of rolling-sliding line contact combined with a multiaxial fatigue life calculation model based on Fatemi-Socie (FS) critical plane crack initiation criterion, previously proposed by Basan and Marohnić (2019) is used. Besides determination of number of load reversals to crack initiation and fatigue failure, model enables estimation of most likely locations of cracks initiation and based on critical planes orientation also the damage type they are likely to form. In its original form, FS criterion uses shear fatigue parameters but using equivalent deformation (von Mises) criterion, it can be written in the form based on axial fatigue strain-life parameters which are estimated in most of proposed estimation methods:

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max n

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f 

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 c

(1)

b

1

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k

N

N

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f   

f

f

2

R G

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