Physical Manifestation of a90/95 in Remnant Life Revision Studies of Aero-engine Components (original) (raw)

Probabilistic Life Assessment of Gas Turbine Blade Alloys under Creep

International Journal of Reliability, Risk and Safety: Theory and Application

Deformations occur gradually in the gas turbine components since they are working under high temperature and stress. In the turbine blade alloys, creep is the most significant failure mechanism. In this research, creep life has been estimated for the blade alloys by considering humidity. A method is proposed to estimate the creep life by direct consideration of humidity on the creep life of the gas turbine blade. In the proposed model, the humidity factor is added to the classic Larson Miller creep life estimation method. This model is capable of predicting creep life with known dry temperature (Water Air Ratio=0), mechanical stress, and humidity. In this approach, there is no need to measure blade temperature variation during operation. As a case study, the creep life of first-stage turbine blade alloy is predicted using the proposed method and benchmarked with published (Finite element analysis) FEA results. The reliability of the blades was estimated by considering different success criteria using Monte Carlo simulation. The reliability of the creep rupture life of Nimonic-90 steel was carried out using SCRI mode based on the Z-parameter. The scattered data has been considered for creep rupture of materials in this part. The results show that creep life increases with humidity increase. It is also shown that with an increase in mechanical stress and temperature fluctuations, the reliability of the turbine blade creep life decreases sharply.

Analysis of Creep Life of Steam Turbine Blade by Using Different Material

INTERNATIONAL JOURNAL OF ENGINEERING SCIENCES & RESEARCH TECHNOLOGY, 2014

Turbine Blades are the main component of any steam power plant and have to withstand in very high temperature. The main aim of this paper is to calculate the creep life of 210MW Reheat Reaction Turbine Blade by changing the different material and suggested the best material for the turbine blade, so the life of the turbine blade is increased to some extent. In this paper the modeling of blade is done in PRO-E and analysis of stress is done in ANSYS 14.5 FEA tool. After structural analysis of the turbine blade Modified Larson Miller Parameter is used to calculate the creep life of the turbine blade then the results are compared and finally some of the results are presented.

Advanced Life Assessment Methods for Gas Turbine Engine Components

Procedia Engineering, 2014

In combustion systems for aircraft applications, liners represent an interesting challenge from the engineering point of view regarding the state of stress, including high temperatures (up to 1500°C) varying over time, high thermal gradients, creep related phenomena, mechanical fatigue and vibrations. As a matter of fact, under the imposed thermo-mechanical loading conditions, some sections of the liner can creep; the consequent residual stresses at low temperatures can cause plastic deformations. For these reasons, during engine operations, the material behaviour can be hardly non-linear and the simulation results to be time expensive. Aim of this paper is to select and implement some advanced material life assessment methods to gas turbine engine components such as combustor liners. Uniaxial damage models for Low Cycle Fatigue (LCF), based on Coffin-Manson, Neu-Sehitoglu and Chaboche works, have been implemented in Matlab®. In particular, experimental LCF and TMF results for full size specimens are compared to calibrate these models and to assess TMF life of specimens. Results obtained in different testing conditions have been used for validation. In particular, each model needs specific parameter calibrations to characterize the investigated materials; these parameters and their relation with temperature variation have been experimentally obtained by testing standard specimens.

Creep Life Prediction of Gas Turbine Components under Varying Operating Conditions

2001

A simplified model for creep life prediction of gas turbine components under varying operating conditions is provided. Response Surface Equations are used to connect operating conditions with nodal creep life that is calculated using nodal stresses and temperatures. Then the accumulation of creep rule is applied to determine total creep life. While the present paper is limited to deterministic examples and creep life only, the methodology is expected to be particularly useful for probabilistic prediction of life where the degradation due to both creep and fatigue is taken into account.

Proposal of a stress-based isothermal LCF life model for Aluminium alloy cylinder heads

Procedia Structural Integrity

During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.

Life Estimation of First Stage High Pressure Gas Turbine Blades

2008

Based on very early occurring ruptures found in the first stage high pressure turbine blades of a turbo reactor in a local aviation company, this study has the aim to determine their safe life. The first stage blades are subjected to simultaneous action of gas pressure coming from the combustion chamber, centrifugal forces in the case of the rotor blades and to important temperatures transients, which progress in a very aggressive environment due to hot gases. These combined parameters cause a high state of stress involving several complex mechanisms of damage, such as: fatigue caused by mechanical stress fluctuations, thermo-mechanical fatigue caused by temperature variations and corrosion caused on the stressed elements. Life cycle determination asks for stress evaluation of blades regarding several variables which are approached deterministically in the study. Heat exchange between combustion gases and metal blades is considered. The total stress on two kinds of blades is calculated by the addition of the thermal effect and the mechanical loading. The stress cycle is then calculated for different steps of the engine function during the operation by considering the variation of the thermal and the mechanical properties of the system. Safe life determination is done by two different approaches: the safe life approach by the initiation model and the damage tolerance approach considering the defect growth mechanics and considering the pitting corrosion effect. The calculation is applied for stator and rotor blades of an aero engine high pressure turbine made of NI 738. Since these parts are high risk components from the point of view of potential failure consequences, the risk is assessed as well. The results obtained are studied to determine the solution to the problem, and to propose a safe decision to be taken about the design or maintenance procedures.

Implications of engine's deterioration upon an aero-engine HP turbine blade's thermal fatigue life

International Journal of Fatigue, 2000

Possessing a better knowledge of the impacts of engine deterioration upon an aircraft's performance as well as its fuel and component life usage, helps the users make wiser management decisions and hence achieve improved engine utilization. For a military aircraft, using a computer performance simulation, the consequences of engine deterioration on a high pressure turbine blade's thermal fatigue life are predicted.

Aero-engine turbine blade life assessment using the Neu/Sehitoglu damage model

International Journal of Fatigue, 2014

Suitable models and software were integrated to provide a life assessment tool for aero jet engine blades. The approach combines aircraft and engine performance, turbine blade sizing, heat transfer, finite element analysis (FEA), and thermo-mechanical fatigue life assessment (TMF) using the Neu/Sehitoglu (N/S) TMF model. For a typical medium range flight mission, we find that the environmental (oxidation) effect drives the TMF blade life and the blade coolant side is identified as the critical location. Furthermore, a parametric and sensitivity study of the N/S model parameters suggests that in addition to four previously reported parameters, the sensitivity of the phasing to oxidation damage (n ev) could be critical to overall TMF life.