engleski

On estimation of Basquin-Coffin-Manson fatigue parameters of low-alloy steel AISI4140

Strain life approach and methodology is widely used in product development for calculation of number of load reversals 2Nf to crack initiation. Since in early design phases experimentally determined material parameters necessary for performing lifetime calculations are rarely available, methods for their estimation from monotonic material properties are usually implemented. Most of the existing methods for the prediction of strain life parameters are based on direct and independent correlation of experimentally determined strain life parameters with one or more monotonic properties of the material. Certain methods even suggest use of constant values for these fatigue parameters. In strain life approach the fatigue durability of the material is defined by /2 2Nf relationship. As an alternative to the existing approach and methods, it is suggested that estimation of strain life fatigue parameters should be based on analysis of actual strain life data. Instead of individual fatigue parameters, /2 2Nf relations are correlated with chosen monotonic property so that, unlike in existing methods, fatigue parameters are not treated independently. New Basquin-Coffin-Manson parameters determined in such a manner can then be correlated with and estimated from chosen monotonic property. Values of strain life fatigue parameters have been estimated for typical high-strength low alloy steels AISI4140 using both proposed approach and hardness method proposed in literature. Evaluation and comparison of fatigue lives calculated for different values of strain amplitude confirmed validity and good predictive capabilities of method based on new approach.

strain life approach; fatigue parameters; estimation; monotonic properties

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