Application of hybrid method in calculation of fatigue life for C45 steel (1045 steel) structural components

Abstract The article presents a new hybrid method to be applied for calculations of construction steel fatigue life on the example of C45 steel (standard AISI: 1045 steel). The hybrid method involves an assumption that cyclic properties of steel in the range of low cycle fatigue (LCF) are defined in strain based approach by strain diagram of Manson-Coffin, whereas in the high cycle fatigue range (HCF), cyclic properties of steel are described with Wohler diagram in stress based approach. The considered calculation method finds application for cases when service load is contained in the above mentioned ranges, that is, a certain number of load cycles reach values from LCF range and the remaining ones are from HCF range. The work presents a description of a hybrid method, analysis and results of calculations for C45 steel under the conditions of multi stage loads – some of which being contained in LCF range. Calculation results have been compared with the results of experimental tests which proves that in order to sum fatigue damage a modified hypothesis needs to be used.