Structural Integrity Assessment and Engine Test of an Additive Manufactured First Stage Ring Segment of a Siemens Large Gas Turbine

2019 ◽  
Author(s):  
Tobias T. Rühmer ◽  
Uwe Gampe ◽  
Kathrin A. Fischer ◽  
Thomas Wimmer ◽  
Christoph Haberland
Keyword(s):  
Gas Turbine ◽  
Structural Integrity ◽  
Low Cycle Fatigue ◽  
Creep Rupture ◽  
Measuring System ◽  
Dynamic Strain ◽  
Uniaxial Tensile ◽  
Cycle Fatigue ◽  
Integrity Assessment ◽  
Ring Segment

Abstract The first stage ring segment (RS) of a Siemens large gas turbine has been redesigned for Selective Laser Melting (SLM) in order to reduce the cooling air consumption and to increase the gas turbine efficiency. The material is IN939. Cylindrical specimen for uniaxial tensile, cyclic tests and creep rupture tests have been manufactured by SLM to characterize the material by derivation of stress strain and creep rupture curves. The ring segment has been tested in a real gas turbine. The loading conditions as well as measurement data from thermocouples and dynamic strain gages have been taken as input for numerical structural integrity assessment. Permissible service life of the ring segment was evaluated in respect of low cycle fatigue (LCF), high cycle fatigue (HCF) and creep. Results have been compared with the conventional design. Furthermore the hook lock up in the engine was evaluated. The manufacturing quality was ensured through several methods including an optical 3D measuring system and computer tomography, process specimen and flow tests. Post investigations such as cut ups and metallography have also been conducted. The results show that the additive manufactured RS meets the required service lifetime.

Structural Integrity Assessments for Validating Directed Energy Deposition Repairs of Integrally Bladed Rotor

2020 ◽  
Author(s):  
Onome Scott-Emuakpor ◽  
Brian Runyon ◽  
Tommy George ◽  
Andrew Goldin ◽  
Casey Holycross ◽  
...  
Keyword(s):  
Energy Deposition ◽  
Structural Integrity ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Component Level ◽  
Integrity Assessment ◽  
Repair Processes ◽  
Directed Energy Deposition ◽  
Directed Energy ◽  
Blown Powder

Abstract Considerable steps to assess the structural capability of laser directed energy deposition (DED) aim to determine the viability of repair processes for integrally bladed rotors (IBRs). Two laser DED processes are under investigation in this study: wire fed and blown powder feedstock. Using a small subsonic Titanium 6Al-4V fan as the component of interest, a series of tests and associated models for laboratory specimens, subcomponents, and components are necessary for proper assessment of material structural properties pertaining to the intended mission of the IBR. Experimentation on laboratory specimens acquire properties such as tensile strength, elongation, low cycle fatigue (LCF), high cycle fatigue (HCF), crack growth rate, and fracture toughness. Subcomponent test articles fabrication occurs by sectioning an operational IBR into individual blades for vibration HCF assessment. Component level testing focuses on LCF and overspeed strength acquired from spin rig testing. Even though the full IBR repair validation of laboratory specimen, subcomponent, and component testing has yet to be completed, the results to-date for laser DED repairs are promising. Furthermore, this plan for structural integrity assessment can serve as a reference for validation of future IBR repair processes.

A Life Prediction Model for Single-Crystal Nickel-Base Alloys Under Low-Cycle Fatigue

2020 ◽  
Author(s):  
Firat Irmak ◽  
Navindra Wijeyeratne ◽  
Taejun Yun ◽  
Ali Gordon
Keyword(s):  
Single Crystal ◽  
Gas Turbine ◽  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Turbine Blades ◽  
Deformation Model ◽  
Cycle Fatigue ◽  
Nickel Base Superalloys ◽  
Nickel Base ◽  
Prediction Approach

Abstract In the development and assessment of critical gas turbine components, simulations have a crucial role. An accurate life prediction approach is needed to estimate lifespan of these components. Nickel base superalloys remain the material of choice for gas turbine blades in the energy industry. These blades are required to withstand both fatigue and creep at extreme temperatures during their usage time. Nickel-base superalloys present an excellent heat resistance at high temperatures. Presence of chromium in the chemical composition makes these alloys highly resistant to corrosion, which is critical for turbine blades. This study presents a flexible approach to combine creep and fatigue damages for a single crystal Nickel-base superalloy. Stress and strain states are used to compute life calculations, which makes this approach applicable for component level. The cumulative damage approach is utilized in this study, where dominant damage modes are capturing primary microstructural mechanism associated with failure. The total damage is divided into two distinctive modules: fatigue and creep. Flexibility is imparted to the model through its ability to emphasize the dominant damage mechanism which may vary among alloys. Fatigue module is governed by a modified version of Coffin-Manson and Basquin model, which captures the orientation dependence of the candidate material. Additionally, Robinson’s creep rupture model is applied to predict creep damage in this study. A novel crystal visco-plasticity (CVP) model is used to simulate deformation of the alloy under several different types of loading. This model has capability to illustrate the temperature-, rate-, orientation-, and history-dependence of the material. A user defined material (usermat) is created to be used in ANSYS APDL 19.0, where the CVP model is applied by User Programmable Feature (UPF). This deformation model is constructed of a flow rule and internal state variables, where the kinematic hardening phenomena is captured by back stress. Octahedral, cubic and cross slip systems are included to perform simulations in different orientations. An implicit integration process that uses Newton-Raphson iteration scheme is utilized to calculate the desired solutions. Several tensile, low-cycle fatigue (LCF) and creep experiments were conducted to inform modeling parameters for the life prediction and the CVP models.

Experimental and Numerical Investigation on an Additively Manufactured Gas Turbine Ring Segment With an In-Wall Cooling Scheme

2019 ◽  
Author(s):  
Thomas Wimmer ◽  
Tobias Ruehmer ◽  
York Mick ◽  
Lieke Wang ◽  
Bernhard Weigand
Keyword(s):  
Gas Turbine ◽  
Thermal Model ◽  
Operating Conditions ◽  
Measuring System ◽  
External Boundary ◽  
Turbine Cooling ◽  
Cooling Channels ◽  
Rectangular Channels ◽  
Full Speed ◽  
Ring Segment

Abstract An additively manufactured ring segment (AMRS) for the first row of a large gas turbine from Siemens was designed with a novel cooling scheme. The wavy rectangular channels used for in-wall cooling are only viable through Additive Manufacturing (AM). Manufacturing deviations have been tracked using an optical 3D measuring system and were accounted for in the calculation models for thermal analysis. Friction factors of the cooling channels have been investigated experimentally allowing accurate flow prediction. The AMRS was tested in an engine at “Full Speed – Full Load” operating condition. It was instrumented with thermocouples and pressure taps. All crucial engine operating conditions were monitored. The results are compared to a conventional ring segment with similar instrumentation. It was installed next to the AMRS in the wake of the same burner. From a thermal model of the conventional ring segment and the measured temperatures the external boundary conditions are scaled to fit the experimental data. These were applied to the thermal model of the AMRS which was used for performance evaluation of the cooling scheme. This work addresses and quantifies the application of AM on advanced gas turbine cooling schemes. The AMRS underwent a mechanical integrity investigation in a referenced publication.

The Effect of Nitrogen Alloying on the Low Cycle Fatigue and Creep-Fatigue Interaction Behavior of 316LN Stainless Steel

2013 ◽  
Vol 794 ◽  
pp. 441-448 ◽  
Author(s):  
G.V. Prasad Reddy ◽  
R. Sandhya ◽  
M.D. Mathew ◽  
S. Sankaran
Keyword(s):  
Stainless Steel ◽  
Strain Rate ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Hold Time ◽  
Cyclic Plasticity ◽  
Dynamic Strain ◽  
Cycle Fatigue ◽  
Intergranular Cracking ◽  
Creep Fatigue

Low cycle fatigue (LCF) and Creep-fatigue interaction (CFI) behavior of 316LN austenitic stainless steel alloyed with 0.07, 0.11, 0.14, .22 wt.% nitrogen is briefly discussed in this paper. The strain-life fatigue behavior of these steels is found to be dictated by not only cyclic plasticity but also by dynamic strain aging (DSA) and secondary cyclic hardening (SCH). The influence of the above phenomenon on cyclic stress response and fatigue life is evaluated in the present study. The above mentioned steels exhibited both single-and dual-slope strain-life fatigue behavior depending on the test temperatures. Concomitant dislocation substructural evolution has revealed transition in substructures from planar to cell structures justifying the change in slope. The beneficial effect of nitrogen on LCF life is observed to be maximum for 316LN with nitrogen in the range 0.11 - 0.14 wt.%, for the tests conducted over a range of temperatures (773-873 K) and at ±0.4 and 0.6 % strain amplitudes at a strain rate of 3*10-3 s-1. A decrease in the applied strain rate from 3*10-3 s-1 to 3*10-5 s-1 or increase in the test temperature from 773 to 873 K led to a peak in the LCF life at a nitrogen content of 0.07 wt.%. Similar results are obtained in CFI tests conducted with tensile hold periods of 13 and 30 minutes. Fractography studies of low strain rate and hold time tested specimens revealed extensive intergranular cracking.

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