scholarly journals Effect of Wave Process of Plastic Deformation at Forging on the Fatigue Fracture Mechanism of Titanium Compressor Disks of Gas Turbine Engine

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1851
Author(s):  
Andrey A. Shanyavskiy ◽  
Alexey P. Soldatenkov ◽  
Alexandr D. Nikitin
Keyword(s):  
Plastic Deformation ◽  
Titanium Alloy ◽  
Fatigue Crack ◽  
Gas Turbine ◽  
Crack Growth ◽  
Wave Process ◽  
Gas Turbine Engine ◽  
Tunneling Effect ◽  
Growth Duration ◽  
Turbine Engine

The low-cycle fatigue behavior of the VT3-1 titanium alloy (Ti–6Al–3Mo–2Cr alloy) under loading with a triangular and trapezoidal shape of cycle waveform was studied on round specimens prepared from forged compressor disks of a gas turbine engine. The filament type structure after forging has alternating filaments with the ductile and quasi-brittle state of the metal as a result of the wave process of plastic deformation during the metal forging process. The crack propagation, regardless of the cyclic waveform shape, occurs by the crack meso-tunneling mechanism: initially, the cracks propagate along the filaments by a quasi-brittle mechanism with the formation of a facetted pattern relief on the fracture surface reflecting the two-phase structure of the titanium alloy, and then, the bridge between the meso-tunnels is fractured with the formation of fatigue striations. The part of the crack growth duration Np/Nf in the durability Nf is determined on the basis of measuring the fatigue striation spacing, and it depends on the crack path with respect to the material filaments. The growth of a fatigue crack in the case of in-service failure of a compressor disk of a gas turbine engine is considered, taking into account the crack meso-tunneling effect, and the fatigue crack growth duration in the disk is determined on the basis of quantitative fractography.

Thermo-mechanical fatigue crack growth behaviour of Ti-6246

2021 ◽  
Author(s):  
◽  
Jennie Palmer
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Gas Turbine ◽  
Crack Growth ◽  
Growth Rates ◽  
Turbine Engine ◽  
Mechanical Fatigue ◽  
Test Conditions ◽  
Materials Used ◽  
Crack Growth Rates

Within the gas turbine engine, the high transient thermal stresses developed due to variations in power requirements during a typical flight cycle give rise to the phenomenon of thermo-mechanical fatigue (TMF). Associated with higher operating temperatures, the study of TMF within the gas turbine engine has mainly been focused on materials used in the latter turbine sections. However, the increasing temperatures to improve operating efficiency have led to the requirements for an understanding of the TMF behaviour in materials used for the later stages of the compressor. As such, fatigue crack growth rates are required to be evaluated under non-isothermal conditions along with the development of a detailed understanding of related failure mechanisms. In the current study a bespoke TMF crack growth (TMFCG) test set up has been developed and validated to investigate the TMFCG behaviour of the titanium alloy, Ti-6246. The study has explored the effects of phasing between mechanical loading and temperature, as well as the effects of maximum cycle temperature. Results show in-phase (IP) test conditions to have faster crack growth rates than out-of-phase (OP) test conditions, due to increased temperature at peak stress and therefore increased time-dependent crack growth. Fractography evidences subtle differences in fracture mechanisms and the microstructural analysis along the crack path has aided the characterisation of damage mechanisms in IP and OP test conditions.

Probabilistic Fretting Fatigue Assessment of Aircraft Engine Disks

2009 ◽  
Author(s):  
Michael P. Enright ◽  
Kwai S. Chan ◽  
Jonathan P. Moody ◽  
Patrick J. Golden ◽  
Ramesh Chandra ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Gas Turbine ◽  
Crack Growth ◽  
Stress Gradient ◽  
Random Variables ◽  
Aircraft Engine ◽  
Fretting Fatigue ◽  
Turbine Engine ◽  
Engine Components

Fretting fatigue is a random process that continues to be a major source of damage associated with the failure of aircraft gas turbine engine components. Fretting fatigue is dominated by the fatigue crack growth phase and is strongly dependent on the magnitude of the stress values in the contact region. These stress values often have the most influence on small cracks where traditional long-crack fracture mechanics may not apply. A number of random variables can be used to model the uncertainty associated with the fatigue crack growth process. However, these variables can often be reduced to a few primary random variables related to the size and location of the initial crack, variability associated with applied stress and crack growth life models, and uncertainty in the quality and frequency of non-deterministic inspections. In this paper, an approach is presented for estimating the risk reduction associated with non-destructive inspection of aircraft engine components subjected to fretting fatigue. Contact stress values in the blade attachment region are estimated using a fine mesh finite element model coupled with a singular integral equation solver and combined with bulk stress values to obtain the total stress gradient at the edge of contact. This stress gradient is applied to the crack growth life prediction of a mode I fretting fatigue crack. A probabilistic model of the fretting process is formulated and calibrated using failure data from an existing engine fleet. The resulting calibrated model is used to quantify the influence of inspection on the probability of fracture of an actual military engine disk under real life loading conditions. The results can be applied to quantitative risk predictions of gas turbine engine components subjected to fretting fatigue.

Estimating working life for aircraft gas turbine engine disks at the stage of fatigue crack development. Part 1

1994 ◽  
Vol 26 (11) ◽  
pp. 796-800 ◽  
Author(s):  
V. V. Pokrovskii ◽  
V. T. Troshchenko ◽  
V. I. Tseitlin ◽  
V. N. Ezhov ◽  
V. S. Zamotaev ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Gas Turbine ◽  
Working Life ◽  
Gas Turbine Engine ◽  
Crack Development ◽  
Turbine Engine ◽  
Aircraft Gas Turbine Engine ◽  
Fatigue Crack Development

Probabilistic Fretting Fatigue Assessment of Aircraft Engine Disks

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Michael P. Enright ◽  
Kwai S. Chan ◽  
Jonathan P. Moody ◽  
Patrick J. Golden ◽  
Ramesh Chandra ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Gas Turbine ◽  
Crack Growth ◽  
Stress Gradient ◽  
Random Variables ◽  
Aircraft Engine ◽  
Fretting Fatigue ◽  
Turbine Engine ◽  
Engine Components

Fretting fatigue is a random process that continues to be a major source of damage associated with the failure of aircraft gas turbine engine components. Fretting fatigue is dominated by the fatigue crack growth phase and is strongly dependent on the magnitude of the stress values in the contact region. These stress values often have the most influence on small cracks where traditional long-crack fracture mechanics may not apply. A number of random variables can be used to model the uncertainty associated with the fatigue crack growth process. However, these variables can often be reduced to a few primary random variables related to the size and location of the initial crack, variability associated with applied stress and crack growth life models, and uncertainty in the quality and frequency of nondeterministic inspections. In this paper, an approach is presented for estimating the risk reduction associated with the nondestructive inspection of aircraft engine components subjected to fretting fatigue. Contact stress values in the blade attachment region are estimated using a fine mesh finite element model coupled with a singular integral equation solver and combined with bulk stress values to obtain the total stress gradient at the edge of contact. This stress gradient is applied to the crack growth life prediction of a mode I fretting fatigue crack. A probabilistic model of the fretting process is formulated and calibrated using failure data from an existing engine fleet. The resulting calibrated model is used to quantify the influence of inspection on the probability of fracture of an actual military engine disk under real life loading conditions. The results can be applied to quantitative risk predictions of gas turbine engine components subjected to fretting fatigue.

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