Study of Mixed-Mode Cracking of Dovetail Root of an Aero-Engine Blade Like Structure

Abstract

Aerospace structures must be designed in such a way so as to be able to withstand even more flight cycles and/or increased loads. Damage tolerance analysis could be exploited more and more to study, understand, and calculate the residual life of a component when a crack occurs in service. In this paper, the authors are presenting the results of a systematic crack propagation analysis campaign performed on a compressor-blade-like structure. The point of novelty is that different blade design parameters are varied and explored in order to investigate how the crack propagation rate in low cycle fatigue (LCF, at R ratio R = 0) could be reduced. The design parameters/variables studied in this work are: (1) The length of the contact surfaces between the dovetail root and the disc and (2) their inclination angle (denoted as “flank angle” in the aero-engine industry). Effects of the friction coefficient between the disc and the blade root have also been investigated. The LCF crack propagation analyses have been performed by recalculating the stress field as a function of the crack propagation by using the FRacture ANalysis Code (Franc3D®).

A Combined Experimental and Numerical Calibration Approach for Modeling the Performance of Aerospace-Grade Titanium Alloy Products

“…Model parameter 𝐴 is determined as the yield stress under the given reference conditions. To calculate parameters 𝐵 and 𝑛, the test temperature (𝑇) is equated with the reference temperature (𝑇 ) and the test strain rate (𝜀 ) with the reference strain rate (𝜀 ), eliminating the factors of Equation ( 1) dependent on these variables to obtain Equation (6).…”

“…In particular, Ti-6Al-4V (Ti64) is the most widely used titanium alloy because of its appropriate balance of processing characteristics, such as good malleability, plastic workability, heat treatability, and weldability [4]. In addition, it exhibits good biocompatibility, low Aerospace 2024, 11, 285 2 of 22 density, high corrosion resistance, high compressive strength, adequate ductility, toughness, as well as the capacity to resist to impact loading and damage tolerance [4][5][6].…”

“…However, the effective prediction of the mechanical behavior of materials and design of mechanical components subjected to different strain rate and various temperatures is generally performed with the Johnson-Cook (JC) model [18]. The Johnson-Cook plasticity law is used for the design of mechanical components subjected to impact loading [6,19,20], to several strain rates and various temperatures [21], for predicting the response of a material during machining [22,23], for forming processes [24][25][26] and surface treatments [27,28]. The effects of strain hardening, strain rate sensitivity, and thermal softening are incorporated as a product for the stress response computation.…”

Dynamic Characteristics of a Rotating Blade with a Dovetail Fixture

“…Based on the lumping parameter model of a single blisk sector subjected to dry damping under harmonic excitation, Liu et al [15] used a multi-harmonic method combined with a continuation procedure to investigate the effects of excitation level, tangential stiffness of the friction model, and normal contact force on the steady vibration responses of the system. For the purpose of predicting the residual life, Canale et al [16] adopted the commercial software FRANC3D to analyze the low cycle fatigue crack propagation of a rotating blade with a dovetail fixture, and the results showed 45 • with respect to 30 • and 60 • flank angles and a lower friction factor resulting in a lower crack propagation rate. Yuan et al [17] investigated a novel adaptive reduced order modeling method to reduce the high-fidelity fan blisk with dovetail joints and then analyzed the nonlinear modal characteristics under different friction factors and pre-loadings.…”

Editorial on Special Issue “Fatigue and Fracture Behaviour of Additive Manufacturing Mechanical Components”

“…In Reference [7], the authors presented the results of a systematic crack propagation analysis campaign performed on a compressor-blade-like structure. The point of novelty was that different blade design parameters were varied and explored in order to investigate how the crack propagation rate in low cycle fatigue (LCF, at R ratio R = 0) could be reduced.…”