PSI - Issue 41

Liviu Daniel Pîrvulescu et al. / Procedia Structural Integrity 41 (2022) 492–499 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig 7. The factor for the slope of the fatigue curves

Knowing the correlation coefficients, a master curve can be obtained that includes the dimensional effect. If we consider the fatigue curve A as a reference curve, then the equation of the fatigue curve B for a finite number of cycles becomes: , = ′ , ′ ∙ ( ) − (10) Analysing the experimental results, the correlation factors for finite life of AM50 alloy, including size effect, were obtained: ➢ The coefficient of fatigue strength, ′ : ′ = ′ , =6.2 ′ , =8.0 = 10.205 (11) ➢ The factor for the slope of fatigue curve, : = =6.2 =8.0 = 2.480 (12) If the fatigue curve for the specimen diameter = 6,2 is considered as the reference curve, then the fatigue curve equation for the specimen set with the diameter = 8,0 is obtained: , =8.0 = ′ , =6.2 ′ ∙ ( ) − =6.2 (13) Correlation of fatigue curves is an indicator of the effect of defects and surface processing, respectively, on the fatigue behavior of AM50A alloy. In principle, increasing the diameter of the test piece from = 6,2 to = 8,0 implies an increase in the density of the defects which causes a decrease in the fatigue strength factor. The fracture surfaces of the specimens were analysed by the FEI Inspect S Scanning Electron Microscope (SEM) for structural defects. The fracture surfaces of 6.2 diameter of specimens, analysed by SEM are shown in Fig.8.