scholarly journals Verification of Over-Speed and Burst Margin Limits in Aero Engine Disc along with Low Cycle Fatigue Life

2018 ◽  
Vol 8 (02) ◽  
Author(s):  
Harinath S. P. ◽  
Sharath Chandra GV ◽  
Shreyas P. M. ◽  
Kumar K. Gowda
Keyword(s):  
Low Cycle Fatigue ◽  
Air Transportation ◽  
Design Tool ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
High Speeds ◽  
Duty Cycles ◽  
Aero Engine ◽  
Design Speed ◽  
Probable Interpretation

Aero engine rotor burst evaluation is one of the most important problems to be taken care off, whenever it comes to designing a turbo machinery disc. The consequences of a failure can be intense, since the disc fragments into multiple pieces and they are hurled away in all the possible direction at high speeds. Due to high thermo-mechanical loading conditions the disc is subjected to varying degrees of temperature from bore to rim. However, the centrifugal force dominates in the disc which ranges from 80%-90% and the rest can be treated as thermal and gas loads. The challenge lies at designing a disc for off-design conditions with their varying loads and duty cycles. In present work evaluation of safety limits and low-cycle fatigue (LCF) life estimation of an aero engine disc through classical methods and blending the terminologies with simulation engineering to arrive at a probable interpretation of number of duty cycles is carried out. The methodology compares the fatigue parameters involved in evaluation of disc life at off-design condition through sensitivity analysis. The design tool closely connects the flight certification FAA and EASA the regulating agencies for safety in air transportation vehicles. The off-design speed regulations through API and MIL handbook for material specification are considered to carry out design of experiments using finite element analysis approach

Component Low Cycle Fatigue Behavior Based on Standard Calculation Procedure and Non-Linear FEA

2017 ◽  
Author(s):  
Jürgen Rudolph ◽  
Adrian Willuweit ◽  
Steffen Bergholz ◽  
Christian Philippek ◽  
Jevgenij Kobzarev
Keyword(s):  
Power Plants ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Hybrid Approach ◽  
Combined Cycle ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Constitutive Material Model ◽  
Standard Design ◽  
Creep Fatigue

Components of conventional power plants are subject to potential damage mechanisms such as creep, fatigue and their combination. These mechanisms have to be considered in the mechanical design process. Against this general background — as an example — the paper focusses on the low cycle fatigue behavior of a main steam shut off valve. The first design check based on standard design rules and linear Finite Element Analysis (FEA) identifies fatigue sensitive locations and potentially high fatigue usage. This will often occur in the context of flexible operational modes of combined cycle power plants which are a characteristic of the current demands of energy supply. In such a case a margin analysis constitutes a logical second step. It may comprise the identification of a more realistic description of the real operational loads and load-time histories and a refinement of the (creep-) fatigue assessment methods. This constitutes the basis of an advanced component design and assessment. In this work, nonlinear FEA is applied based on a nonlinear kinematic constitutive material model, in order to simulate the thermo-mechanical behavior of the high-Cr steel component mentioned above. The required material parameters are identified based on data of the accessible reference literature and data from an own test series. The accompanying testing campaign was successfully concluded by a series of uniaxial thermo-mechanical fatigue (TMF) tests simulating the most critical load case of the component. This detailed and hybrid approach proved to be appropriate for ensuring the required lifetime period of the component.

The Revised Universal Slope Method to Predict the Low-Cycle Fatigue Lives of Elbow and Tee Pipes

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Hiun Nagamori ◽  
Koji Takahashi
Keyword(s):  
Experimental Data ◽  
Internal Pressure ◽  
Low Cycle Fatigue ◽  
Experimental Studies ◽  
High Accuracy ◽  
Universal Method ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Slope Method ◽  
Stress States

The stress states of elbow and tee pipes are complex and different from those of straight pipes. The low-cycle fatigue lives of elbows and tees cannot be predicted by Manson's universal slope method; however, a revised universal method proposed by Takahashi et al. was able to predict with high accuracy the low-cycle fatigue lives of elbows under combined cyclic bending and internal pressure. The objective of this study was to confirm the validity of the revised universal slope method for the prediction of low-cycle fatigue behaviors of elbows and tees of various shapes and dimensions under conditions of in-plane bending and internal pressure. Finite element analysis (FEA) was carried out to simulate the low-cycle fatigue behaviors observed in previous experimental studies of elbows and tees. The low-cycle fatigue behaviors, such as the area of crack initiation, the direction of crack growth, and the fatigue lives, obtained by the analysis were compared with previously obtained experimental data. Based on this comparison, the revised universal slope method was found to accurately predict the low-cycle fatigue behaviors of elbows and tees under internal pressure conditions regardless of differences in shape and dimensions.

Improved Low Cycle Fatigue Analysis for Ni-Based Turbine Nozzles

2018 ◽  
Author(s):  
Gianluca Maggiani ◽  
Matthew J. Roy ◽  
Simone Colantoni ◽  
Philip J. Withers
Keyword(s):  
Gas Turbines ◽  
Mechanical Test ◽  
Low Cycle Fatigue ◽  
Computation Time ◽  
Cyclic Hardening ◽  
Life Assessment ◽  
Type Model ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Material Models

The requirements for cleaner energy have driven industrial gas turbines manufacturers to increase firing temperatures and improve cooling of nozzles. The application of high temperature alloys having adequate thermo-mechanical requirements is critical, as assessed by low cycle fatigue performance. The effect of higher firing temperatures combined with higher cooling efficiencies has lead to operating cycles where the level of plastic strain imparted define component life. The capability of material models to account for non-linear effects such as ratchetting or shakedown, cyclic hardening or softening as well as Bauschinger or relaxation effects have been highlighted in this context. Neglecting these effects can lead to over and under-conservative life assessment analysis, while accounting for them using standard multilinear material models lead to convergence issues in finite element analysis. In this paper, Chaboche viscoplastic model has been applied to a transient structural of a first stage gas turbine nozzle. Fitting of the model based on experimental mechanical test data on MAR-M-247 alloy will be described, followed by an overview of how the model may be implemented to a benchmark nozzle thermo-mechanical transient analysis. Finally the details how the Chaboche-type model has provided up to 50% decrease in computation time when compared to using a standard multi-linear material modelling approach.

Low Cycle Fatigue Tests and Simulations on Steel Elbows

2013 ◽  
Author(s):  
Patricia Pappa ◽  
George E. Varelis ◽  
Spyros A. Karamanos ◽  
Arnold M. Gresnigt
Keyword(s):  
Finite Element ◽  
Low Cycle Fatigue ◽  
Local Strain ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Out Of Plane ◽  
Strain Gauge Measurements ◽  
Number Of Cycles

In this paper the low cycle fatigue behaviour of steel elbows under strong cyclic loading conditions (in-plane and out-of-plane) is examined. The investigation is conducted through advanced finite element analysis tools, supported by real-scale test data for in-plane bending. The numerical results are successfully compared with the experimental measurements. In addition, a parametric study is conducted, which is aimed at investigating the effects of the diameter-to-thickness ratio on the low-cycle fatigue of elbows, focusing on the stress and strain variations. Strain gauge measurements are compared with finite element models. Upon calculation of local strain variation at the critical location, the number of cycles to fracture can be estimated.

Influence of Initial and Welding Residual Stresses on Low Cycle Fatigue and Ratcheting Response Simulations of Elbows

2017 ◽  
Author(s):  
Nazrul Islam ◽  
Tasnim Hassan
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Low Cycle Fatigue ◽  
Simulation Models ◽  
Cycle Fatigue ◽  
Residual Stress Field ◽  
Element Analysis ◽  
Girth Welding ◽  
Stress States ◽  
Welding Processes

Earlier studies [1] showed that the ANSYS software package customized with an advanced rate-independent constitutive model was unable to simulate some of the low-cycle fatigue responses of elbow components. Hence, simulations are performed to investigate the influence of manufacturing and welding residual stresses on elbow low-cycle fatigue responses. The sequentially coupled thermo-mechanical finite element analysis is performed to determine the initial residual stress states in elbows due to the elbow manufacturing processes and welding of elbows to straight pipes. Real-time girth-welding processes are taken into account to simulate the welding induced residual stress field. Incorporating these initial residual stresses in the computations, low-cycle fatigue and strain ratcheting responses are simulated by ANSYS. The simulation responses demonstrate that the influence of manufacturing and welding residual stresses in elbows on its low-cycle fatigue responses is negligible. Hence, the question remains what is missing in the simulation models that some of the elbow low-cycle fatigue responses cannot be simulated.

Low Cycle Fatigue Behaviour of a Turbine Blade Made of Nickel Base Wrought Alloy

2014 ◽  
Vol 891-892 ◽  
pp. 506-511 ◽  
Author(s):  
Benudhar Sahoo ◽  
Sashi Kanta Panigrahi
Keyword(s):  
Turbine Blade ◽  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Fatigue Behaviour ◽  
Dynamic Strain ◽  
Transgranular Fracture ◽  
Cycle Fatigue ◽  
Aero Engine ◽  
Nickel Base ◽  
Super Alloy

Life of an aero-engine is limited by the life of the turbine blade in particular and that of hot end components in general. Design of aero-engine is always conservative in nature considering the flight safety as paramount important. Earlier engines have been assigned life in hours but the life of the component is limited by LCF cycles particularly during the start-stop cycles. In this paper LCF behaviour of a typical Russian origin nickel base wrought super alloy AP220BD used for turbine blade has been studied at room temperature (RT), 400 °C and 700 °C that corresponds to idle rating and cruise rating of a typical aero-engine. Low cycle fatigue (LCF) tests have been carried out at RT, 400°C and 700 °C at three strain amplitudes of ±0.3%, ±0.5% and ±0.8%. Hysteresis loop have been developed at each strain and temperature. It has been observed that LCF life of the nickel base wrought alloy AP220BD is not influenced significantly at strain amplitude of ±0.3% till it reaches 400° C. Reduction in LCF life with increase in strain amplitude from ±0.3% to ±0.8% is much significant compared to that of increase in temperature up to 700°c.The higher life at intermediate strain of ±0.5% may be due to DSA(dynamic strain aging) of the material. Transgranular fracture has been observed at RT & 400° C while intergranular fracture at 700° C.

A Nonlinear Dynamic Reduced-Order Model for a Large Gas Turbine Outer Casing Low Cycle Fatigue Prediction

2021 ◽  
Author(s):  
Aditya Dubey ◽  
Rishi Relan ◽  
Uwe Lohse ◽  
Jaroslaw Szwedowicz
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Gas Turbine ◽  
Nonlinear Dynamic ◽  
Low Cycle Fatigue ◽  
Reduced Order Model ◽  
Cycle Fatigue ◽  
Order Model ◽  
Element Analysis ◽  
Reduced Order

Abstract The secondary stresses that result from nonlinear and transient thermal gradients during the start-up and shut down of the large gas turbine engines drive low-cycle fatigue at specific locations of the outer casing. Typical service inspection of the outer casing is primarily based on finite element analysis estimates, considering various safety factors. However, as finite element analysis includes the worst possible combination of loading scenarios and operating conditions any engine may encounter in actual operation, this results in a conservative estimation of the service interval. Therefore, a generic preventive maintenance plan for the whole fleet often underutilises the casing capability and added cost. Hence, this paper proposes a data-driven nonlinear dynamic reduced-order model developed using the temperature data from low-cycle fatigue critical casing locations, ramp rates, and the percentage load of operation to predict the stresses. As a result, a reduced-order model can assess the damage for low-cycle fatigue critical locations in real-time using the operational data and propose an appropriate service intervention plan for each casing in a fleet.

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