FRACTOGRAPHIC ANALYSIS OF FATIGUE CRACK GROWTH IN ENGINE COMPRESSOR DISKS OF Ti-6Al-3Mo-2Cr TITANIUM ALLOY

Autor: A. A. Shanyavsky, N. V. Stepanov
Rok vydání: 1995
Předmět:
Zdroj: Fatigue & Fracture of Engineering Materials and Structures. 18:539-550
ISSN: 1460-2695
8756-758X
Popis: Fractographic features related to fatigue crack growth in a Ti-6Al-3Mo alloy are studied using compressor disks tested on a hydraulic test bed and which simulate operational multiaxial cyclic loading conditions. The hold-time of a cycle results in the formation of a fracture relief which reflects mainly the two-phase (α + β) lamellar structure of the titanium alloy and a fragmentary fatigue striation formation. Correlation between the number of fatigue striations on the fracture surface and the number of applied blocks of loading (imitating the service conditions of compressor disks) has been obtained. The hold-time duration of the cycle does not affect the crack growth rate and the formation of the fracture relief in this material. An analytic expression is suggested to describe the relationship between fatigue striation spacing,δ, and the stress intensity factor K I c as applied to quarter-ellipse-shaped cracks; it is of the form δ = C[f(τ, FCi)K I c ] 4 , where f(τ, FCi) accounts for the hold-time, τ, and the programmed loading together with their influence on the fatigue crack growth behaviour. The particular threshold value of stress intensity factor (K I c ) τ is established at 20 MPa√m. The work indicates that the role of τ manifests itself via a considerable acceleration of crack growth.
Databáze: OpenAIRE
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