Fatigue Analysis of Forged Aerospace Components Based on Micro Structural Parameters

Abstract

With the objective of creating a simulation model for the lifetime calculation of forged aerospace components it is necessary to clarify the damage mechanisms in the materials used. This has been researched for the Ni-base alloy Inconel 718 by varying the forging parameter effective plastic strain rate, which is realised by using three types of equipment: hydraulic press, screw press and hammer. Specimens processed at the screw press show the highest lifetime by keeping all other forging parameters unvaried. Micro structural investigations show that the amount and morphology of dominant as-large-as grains play a important role. This methodology is currently investigated for Ti-6Al-4V. Lifetime tests show that besides effective strain and anisotropy the influence of morphology is important. As soon as the model status allows lifetime analyses the thermo-mechanical process (forging and heat treatment) can be developed depending on the desired lifetime specifications in order to realise an interdisciplinary lifetime optimisation of forgings. A further aim is the use of basic coherences of safe-life and fail-safe approaches in the low and high cycle fatigue region in order to reasonable handle with flaws and defects at the edge layer.