Experimental and Numerical Investigation of High-Temperature Multi-Axial Fatigue

2021 ◽  
Author(s):  
Harish Ramesh Babu ◽  
Marco Böcker ◽  
Mario Raddatz ◽  
Sebastian Henkel ◽  
Horst Biermann ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Biaxial Loading ◽  
Complex Geometry ◽  
Low Cycle Fatigue ◽  
Axial Stress ◽  
Equivalent Stress ◽  
Turbine Blades ◽  
Damage Development ◽  
Simulation Results ◽  
Axial Fatigue

Abstract Gas turbines and aircraft engines are dominated by cyclic operating modes with fatigue-related loads. This may result in the acceleration of damage development on the components. Critical components of turbine blades and discs are exposed to cyclic thermal and mechanical multi-axial fatigue. In the current work, planar-biaxial Low-Cycle-Fatigue tests are conducted using cruciform specimens at different test temperatures. The influence on the deformation and lifetime behaviour of the nickel-base disk alloy IN718 is investigated at selected cyclic proportional loading cases. The calculation of the stress and strain distribution of the cruciform specimens from the experimental data is difficult to obtain due to complex geometry and temperature gradients. Therefore, there is a need for Finite Element Simulations. A viscoplastic material model is considered to simulate the material behaviour subjected to uniaxial and the selected planar-biaxial loading conditions. At first, uniaxial simulation results are compared with the uniaxial experiment results for both batches of IN718. Then, the same material parameters are used for simulating the biaxial loading cases. The prediction of FE simulation results is in good agreement with the experimental LCF test for proportional loadings. The equivalent stress amplitude results of the biaxial simulation are compared with the uniaxial results. Furthermore, the lifetime is calculated from the simulation and by using Crossland and Sines multi-axial stress-based approaches. The Crossland model predicts fatigue life significantly better than the Sines model. Finally, the simulated lifetime results are compared with the experimental lifetime

Experimental and Numerical Investigation of High-Temperature Multi-Axial Fatigue

2021 ◽  
Author(s):  
Harish Ramesh Babu ◽  
Marco Böcker ◽  
Mario Raddatz ◽  
Sebastian Henkel ◽  
Horst Biermann ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Biaxial Loading ◽  
Complex Geometry ◽  
Low Cycle Fatigue ◽  
Axial Stress ◽  
Equivalent Stress ◽  
Turbine Blades ◽  
Damage Development ◽  
Simulation Results ◽  
Axial Fatigue

Abstract Gas turbines and aircraft engines are dominated by cyclic operating modes with fatigue-related loads. This may result in the acceleration of damage development on the components. Critical components of turbine blades and discs are exposed to cyclic thermal and mechanical multi-axial fatigue. In the current work, planar-biaxial Low-Cycle-Fatigue (LCF) tests are conducted using cruciform specimens at different test temperatures. The influence on the deformation and lifetime behaviour of the nickel-base disk alloy Inconel 718 is investigated at selected cyclic proportional loading cases, namely shear and equi-biaxial. The calculation of the stress and strain distribution of the cruciform specimens from the experimental data is difficult to obtain due to complex geometry and temperature gradients. Therefore, there is a need for Finite Element (FE) Simulations. A viscoplastic material model is considered to simulate the material behaviour subjected to uniaxial and the selected planar-biaxial loading conditions. At first, uniaxial simulation results are compared with the uniaxial experiment results for both batches of IN718. Then, the same material parameters are used for simulating the biaxial loading cases. The prediction of FE simulation results is in good agreement with the experimental LCF test for both shear and equi-biaxial loadings. The equivalent stress amplitude results of the biaxial simulation are compared with the uniaxial results. Furthermore, the lifetime is calculated based on the stabilized cycle from the simulation and by using Crossland and Sines multi-axial stress-based approaches. The Crossland model predicts fatigue life significantly better than the Sines model. Finally, the simulated lifetime results are compared with the experimental lifetime.

Study on the Formation of Stray Grains during Directional Solidification of Nickel-Based Superalloys

2016 ◽  
Vol 879 ◽  
pp. 1582-1587 ◽  
Author(s):  
Maria Rita Ridolfi ◽  
Oriana Tassa ◽  
Giovanni de Rosa
Keyword(s):  
Directional Solidification ◽  
Gas Turbines ◽  
Complex Geometry ◽  
Turbine Blades ◽  
Columnar Dendrite ◽  
Affecting Factors ◽  
Stray Grains ◽  
Geometrical Factors ◽  
Stray Grain ◽  
The Impact

Ni-based superalloy single-crystal turbine blades are widely used in gas turbines for aircraft propulsion and power generation as they can be subjected to high service temperature and show high mechanical properties due to the almost total elimination of grain boundaries. Particularly in presence of complex geometry shapes, rare grains nucleating apart from the primary grain, become a serious problem in directional solidification, when characterized by high-angle boundaries with the primary grain, extremely brittle due the elevated amount of highly segregating elements and the absence of grain boundary strengthening elements. It is of fundamental importance analyzing the physical mechanisms of formation of stray grains, to understand which thermo-physical and geometrical factors highly influence their formation and to find possible ways to reduce the impact of the problem. In this paper, constrained dendrite growth and heterogeneous grain nucleation theories have been used to model the formation of stray grains in directional solidification of Ni-base superalloys. The study allows to derive the preferred locations of stray grains formation and the role played by the most affecting factors: (i) geometrical: angle of primary grain dendrites with withdrawal direction and orientation of the primary grain with respect to the side walls, responsible for the formation of volumes where the stray grain undercooling is lower than the undercooling of the columnar dendrite tip; (ii) process and alloy: thermal gradient ahead to the solidification front and alloy composition, influencing the columnar dendrite tip undercooling; (iii) wettability of foreign substrates, on which the stray grain undercooling strongly depends.

Crystal Visco-Plastic Model for Directionally Solidified Ni-Base Superalloys Under Monotonic and Low Cycle Fatigue

2021 ◽  
Author(s):  
Navindra Wijeyeratne ◽  
Firat Irmak ◽  
Ali P. Gordon
Keyword(s):  
Grain Boundaries ◽  
Gas Turbines ◽  
Thermal Stresses ◽  
Low Cycle Fatigue ◽  
Turbine Blades ◽  
Material Behavior ◽  
Flow Rule ◽  
Cycle Fatigue ◽  
Directionally Solidified ◽  
Crystallographic Slip

Abstract Nickel-base superalloys (NBSAs) are extensively utilized as the design materials to develop turbine blades in gas turbines due to their excellent high-temperature properties. Gas turbine blades are exposed to extreme loading histories that combine high mechanical and thermal stresses. Both directionally solidified (DS) and single crystal NBSAs are used throughout the industry because of their superior tensile and creep strength, excellent low cycle fatigue (LCF), high cycle fatigue (HCF), and thermomechanical fatigue (TMF) capabilities. Directional solidification techniques facilitated the solidification structure of the materials to be composed of columnar grains in parallel to the <001> direction. Due to grains being the sites of failure initiation the elimination of grain boundaries compared to polycrystals and the alignment of grain boundaries in the normal to stress axis increases the strength of the material at high temperatures. To develop components with superior service capabilities while reducing the development cost, simulating the material’s performance at various loading conditions is extremely advantageous. To support the mechanical design process, a framework consisting of theoretical mechanics, numerical simulations, and experimental analysis is required. The absence of grain boundaries transverse to the loading direction and crystallographic special orientation cause the material to exhibit anisotropic behavior. A framework that can simulate the physical attributes of the material microstructure is crucial in developing an accurate constitutive model. The plastic flow acting on the crystallographic slip planes essentially controls the plastic deformation of the material. Crystal Visco-Plasticity (CVP) theory integrates this phenomenon to describe the effects of plasticity more accurately. CVP constitutive models can capture the orientation, temperature, and rate dependence of these materials under a variety of conditions. The CVP model is initially developed for SX material and then extended to DS material to account for the columnar grain structure. The formulation consists of a flow rule combined with an internal state variable to describe the shearing rate for each slip system. The model presented includes the inelastic mechanisms of kinematic and isotropic hardening, orientation, and temperature dependence. The crystallographic slip is accounted for by including the required octahedral, cubic, and cross slip systems. The CVP model is implemented through a general-purpose finite element analysis software (i.e., ANSYS) as a User-Defined Material (USERMAT). Uniaxial experiments were conducted in key orientations to evaluate the degree of elastic and inelastic anisotropy. The temperature-dependent modeling parameter is developed to perform non-isothermal simulations. A numerical optimization scheme is utilized to develop the modeling constant to improve the calibration of the model. The CVP model can simulate material behavior for DS and SX NBSAs for monotonic and cyclic loading for a range of material orientations and temperatures.

A Crystal Visco-Plastic Model for Ni-Base Superalloys Under Low Cycle Fatigue

2019 ◽  
Author(s):  
Navindra Wijeyeratne ◽  
Firat Irmak ◽  
Grant Geiger ◽  
Jun-Young Jeon ◽  
Ali Gordon
Keyword(s):  
Gas Turbines ◽  
Internal State ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Turbine Blades ◽  
Material Behavior ◽  
Flow Rule ◽  
Loading Conditions ◽  
Analysis Model ◽  
Plastic Model

Abstract Components in gas turbines, specifically turbine blades are subjected to extreme loading conditions such as high temperatures and stresses over extended periods of time; therefore, predicting material behavior and life expectancy at these loading conditions are extremely important. The development of simulations that accurately predict monotonic response for these materials are highly desirable. Single crystal Ni-base superalloys used in the design of gas turbine blades exhibit anisotropic behavior resulting from texture development and dislocation substructures. A Crystal Visco-plastic (CVP) model has the capability of capturing both phenomena to accurately predict the deformation response of the material. The rate dependent crystal visco-plastic model consists of a flow rule and internal state variables. This model considers the inelastic mechanism of kinematic hardening which is captured using the Back stress. Crystal graphic slip is taken in to account by the incorporation of 12 Octahedral slip systems. An implicit integration structure that uses Newton Raphson iteration scheme is used to solve the desired solutions. The MATLAB model is developed in two parts, including a routine for the CVP constitutive model along with a separate routine which functions as an emulator. The emulator replicates a finite element analysis model and provides the initial calculations needed for the CVP. A significant advantage of the MATLAB model is its capability to optimize the modelling constants to increase accuracy. The CVP model has the capability to display material behavior for monotonic loading for a variety of material orientations and temperatures.

Advanced Experimental and Analytical Investigations on Combined Cycle Fatigue (CCF) of Conventional Cast and Single-Crystal Gas Turbine Blades

2011 ◽  
Author(s):  
Swen Weser ◽  
Uwe Gampe ◽  
Mario Raddatz ◽  
Roland Parchem ◽  
Petr Lukas
Keyword(s):  
Gas Turbines ◽  
Rotor Blade ◽  
Low Cycle Fatigue ◽  
Turbine Blades ◽  
Aircraft Engine ◽  
Combined Cycle ◽  
Rotor Blades ◽  
Blade Design ◽  
Cycle Fatigue ◽  
Predictive Methods

Rotor blades are the highest thermal-mechanical loaded components of gas turbines. Their service life is limited by interaction of creep, low cycle fatigue (LCF), high cycle fatigue (HCF) and surface attack. Because assurance of adequate HCF strength of the rotor blade is an important issue of the blade design the European project PREMECCY has been started by the European aircraft engine manufacturers and research institutes to enhance the predictive methods for combined cycle fatigue (CCF), as a superposition of HCF and LCF. Although today’s predictive methods ensure safe blade design, there are certain shortcomings of assessing fatigue life with Haigh or “modified Goodman diagrams”, such as isolated HCF assessment as well as uni-axial and off-resonant testing. HCF and LCF are considered without taking into account their interaction. PREMECCY is aimed to deliver new and improved CCF prediction methods for exploitation in the industrial design process. Beside development of predictive methods the authors are involved in the design and testing of advanced specimens representing rotor blade features. In this connection the paper presents a novel test specimen type and a unique hot gas rig for CCF feature test at mechanical and ambient representative conditions.

Improving Efficiency in Robot Assisted Belt Grinding of High Performance Materials

2014 ◽  
Vol 907 ◽  
pp. 139-149 ◽  
Author(s):  
Eckart Uhlmann ◽  
Florian Heitmüller
Keyword(s):  
Gas Turbines ◽  
High Performance ◽  
Scale Effects ◽  
Turbine Blades ◽  
Repair Process ◽  
Industrial Robots ◽  
Robot Assisted ◽  
Belt Grinding ◽  
Economy Of Scale ◽  
The Individual

In gas turbines and turbo jet engines, high performance materials such as nickel-based alloys are widely used for blades and vanes. In the case of repair, finishing of complex turbine blades made of high performance materials is carried out predominantly manually. The repair process is therefore quite time consuming. And the costs of presently available repair strategies, especially for integrated parts, are high, due to the individual process planning and great amount of manually performed work steps. Moreover, there are severe risks of partial damage during manually conducted repair. All that leads to the fact that economy of scale effects remain widely unused for repair tasks, although the piece number of components to be repaired is increasing significantly. In the future, a persistent automation of the repair process chain should be achieved by developing adaptive robot assisted finishing strategies. The goal of this research is to use the automation potential for repair tasks by developing a technology that enables industrial robots to re-contour turbine blades via force controlled belt grinding.

scholarly journals A Novel Evaluation Method For Particle Deposition Measurement

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 927-934
Author(s):  
Tao Song ◽  
Chao Liu ◽  
Hengxuan Zhu ◽  
Min Zeng ◽  
Jin Wang
Keyword(s):  
Layer Thickness ◽  
Dielectric Layer ◽  
Gas Turbines ◽  
Particle Deposition ◽  
Optimization Design ◽  
Turbine Blades ◽  
Simulation Software ◽  
Circuit Board ◽  
Normal Operation ◽  
Mass Detection

Abstract Normal operation of gas turbines will be affected by deposition on turbine blades from particles mixed in fuels. This research shows that it is difficult to monitor the mass of the particles deposition on the wall surface in real time. With development of electronic technology, the antenna made of printed circuit board (PCB) has been widely used in many industrial fields. Microstrip antenna is first proposed for monitoring particles deposition to analyse the deposition law of the particles accumulated on the wall. The simulation software Computer Simulation Technology Microwave Studio (CST MWS) 2015 is used to conduct the optimization design of the PCB substrate antenna. It is found that the S11 of vivaldi antenna with arc gradient groove exhibits a monotonous increase with the increase of dielectric layer thickness, and this antenna is highly sensitive to the dielectric layer thickness. Moreover, a cold-state test is carried out by using atomized wax to simulate the deposition of pollutants. A relationship as a four number of times function is found between the capacitance and the deposited mass. These results provide an important reference for the mass detection of the particle deposition on the wall, and this method is suitable for other related engineering fields.

scholarly journals Numerical Simulation and Experimental Study on Axial Stiffness and Stress Deformation of the Braided Corrugated Hose

2021 ◽  
Vol 11 (10) ◽  
pp. 4709
Author(s):  
Dacheng Huang ◽  
Jianrun Zhang
Keyword(s):  
Numerical Simulation ◽  
Geometric Model ◽  
Equivalent Stress ◽  
Element Model ◽  
Maximum Error ◽  
Structural Features ◽  
Axial Stiffness ◽  
Frictional Stress ◽  
Maximum Equivalent Stress ◽  
Simulation Results

To explore the mechanical properties of the braided corrugated hose, the space curve parametric equation of the braided tube is deduced, specific to the structural features of the braided tube. On this basis, the equivalent braided tube model is proposed based on the same axial stiffness in order to improve the calculational efficiency. The geometric model and the Finite Element Model of the DN25 braided corrugated hose is established. The numerical simulation results are analyzed, and the distribution of the equivalent stress and frictional stress is discussed. The maximum equivalent stress of the braided corrugated hose occurs at the braided tube, with the value of 903MPa. The maximum equivalent stress of the bellows occurs at the area in contact with the braided tube, with the value of 314MPa. The maximum frictional stress between the bellows and the braided tube is 88.46MPa. The tensile experiment of the DN25 braided corrugated hose is performed. The simulation results are in good agreement with test data, with a maximum error of 9.4%, verifying the rationality of the model. The study is helpful to the research of the axial stiffness of the braided corrugated hose and provides the base for wear and life studies on the braided corrugated hose.

Thermomechanical Fatigue Behavior of Bare and Coated CMSX-4

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
T. Coppola ◽  
S. Riscifuli ◽  
O. Tassa ◽  
G. Pasquero
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Turbine Blades ◽  
Thermomechanical Fatigue ◽  
Tensile Creep ◽  
Thermal Gradients ◽  
Test Program ◽  
Complete Set ◽  
Comparison Of The Results ◽  
Very High

Highly cooled turbine blades undergo very high thermal gradients during rapid engine idle-max-idle cycling. Traditional isothermal fatigue data are often insufficient for predicting service lives. A complete set of high temperature tests, in the range of 750–1050°C, was performed on single crystal alloy CMSX-4. The test program comprised tensile, creep, low cycle fatigue, and thermomechanical fatigue (TMF) tests. In particular the cycle time for TMF was 3 min, aiming to simulate the real high-power transient conditions in aircraft engines. Clockwise and counterclockwise diamond cycle types were applied on bare and coated specimens to investigate their influence on the fatigue limit. The comparison of the results obtained with the available ones from open literature is discussed.

Development and Fabrication of Silicon Nitride Components for Ceramic Gas Turbine

1997 ◽  
Author(s):  
Keisuke Makino ◽  
Ken-Ichi Mizuno ◽  
Toru Shimamori
Keyword(s):  
High Temperature ◽  
Silicon Nitride ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Turbine Blades ◽  
High Strength ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Spark Plug ◽  
Power Turbine

NGK Spark Plug Co., Ltd. has been developing various silicon nitride materials, and the technology for fabricating components for ceramic gas turbines (CGT) using theses materials. We are supplying silicon nitride material components for the project to develop 300 kW class CGT for co-generation in Japan. EC-152 was developed for components that require high strength at high temperature, such as turbine blades and turbine nozzles. In order to adapt the increasing of the turbine inlet temperature (TIT) up to 1,350 °C in accordance with the project goals, we developed two silicon nitride materials with further unproved properties: ST-1 and ST-2. ST-1 has a higher strength than EC-152 and is suitable for first stage turbine blades and power turbine blades. ST-2 has higher oxidation resistance than EC-152 and is suitable for power turbine nozzles. In this paper, we report on the properties of these materials, and present the results of evaluations of these materials when they are actually used for CGT components such as first stage turbine blades and power turbine nozzles.

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