Constraint Related Fatigue Crack Initiation Life of GH4169 Superalloy

Nickel-based GH4169 superalloy is used as turbine disc material in aeroengines because of its good oxidation resistance, good formability, weldability, and high strength. However, turbine disc fatigue failure will inevitably occur in onerous service environments and after a long operation time. To ensure the safety and reliability of aeroengines, the fatigue damage behavior and fatigue life of GH4169 superalloy need to be studied. Constraint is an important factor affecting the fatigue fracture behavior of materials, because changing it will impact the fatigue behavior. To achieve a long service life and high reliability of aeroengines, fatigue and constraint effects must be researched. However, there are only limited studies on the effect of constraint on fatigue crack initiation time. In this study, a crystal plasticity constitutive model based on low cycle fatigue rate correlation was applied to the GH4169 superalloy. Two fatigue indicators, namely the cumulated energy dissipation and cumulated plastic slip, were introduced as fatigue crack initiation criteria to study the fatigue crack initiation time for different micro-notch depths and lengths. In addition, the relationship between constraint and fatigue crack initiation life was further investigated using the unified constraint parameter A(p). The results showed that both cumulated energy dissipation and cumulated plastic slip can accurately predict the fatigue crack initiation time. With the increase in micro-notch depth, the fatigue crack initiation time decreased, while it increased with the increase in micro-notch length. A linear relationship between the fatigue crack initiation time and root A(p) under different micro-notch depths and lengths was observed. Based on this relationship, the constraint related to the fatigue crack initiation time can be determined.

Automated summary

Nickel-based GH4169 superalloy is commonly used in aeroengines due to its favorable properties. The study focuses on the fatigue behavior and fatigue life of GH4169 superalloy to ensure the safety and reliability of aeroengines. Constraint is an important factor affecting the fatigue fracture behavior of materials. The study introduces two fatigue indicators and investigates the relationship between constraint and fatigue crack initiation life, providing insights into the effect of constraint on fatigue crack initiation time.