scholarly journals Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys

2000 ◽  
Author(s):  
Nagaraj K. Arakere ◽  
Gregory Swanson
Keyword(s):  
Fatigue Life ◽  
Single Crystal ◽  
Turbine Blade ◽  
Fatigue Failure ◽  
Failure Criterion ◽  
Crystal Orientation ◽  
Rocket Engine ◽  
Maximum Shear Stress ◽  
Turbine Blades ◽  
Fe Model

High Cycle Fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Single crystal nickel turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry because of their superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493, PWA 1484, RENE’ N-5 and CMSX-4. These alloys play an important role in commercial, military and space propulsion systems. Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades are complicated to predict due to the material orthotropy and variations in crystal orientations. Fatigue life estimation of single crystal turbine blades represents an important aspect of durability assessment. It is therefore of practical interest to develop effective fatigue failure criteria for single crystal nickel alloys and to investigate the effects of variation of primary and secondary crystal orientation on fatigue life. A fatigue failure criterion based on the maximum shear stress amplitude [Δτmax] on the 24 octahedral and 6 cube slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criterion reduces the scatter in uniaxial LCF test data considerably for PWA 1493 at 1200F in air. Additionally, single crystal turbine blades used in the alternate advanced high-pressure fuel turbopump (AHPFTP/AT) are modeled using a large-scale 3D finite element (FE) model. This FE model is capable of accounting for material orthotrophy and variation in primary and secondary crystal orientation. Effects of variation in crystal orientation on blade stress response are studied based on 297 FE model runs. Fatigue lives at critical points in the blade are computed using FE stress results and the failure criterion developed. Stress analysis results in the blade attachment region are also presented. Results presented demonstrates that control of secondary and primary crystallographic orientation has the potential to significantly increase a component’s resistance to fatigue crack growth without adding additional weight or cost.

scholarly journals Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys

2000 ◽  
Vol 124 (1) ◽  
pp. 161-176 ◽  
Author(s):  
N. K. Arakere ◽  
G. Swanson
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Finite Element Model ◽  
Single Crystal ◽  
Fatigue Failure ◽  
Failure Criterion ◽  
Crystal Orientation ◽  
Rocket Engine ◽  
Turbine Blades ◽  
Element Model

High cycle fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Single crystal nickel turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493, PWA 1484, RENE’ N-5 and CMSX-4. These alloys play an important role in commercial, military and space propulsion systems. Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades are complicated to predict due to the material orthotropy and variations in crystal orientations. Fatigue life estimation of single crystal turbine blades represents an important aspect of durability assessment. It is therefore of practical interest to develop effective fatigue failure criteria for single crystal nickel alloys and to investigate the effects of variation of primary and secondary crystal orientation on fatigue life. A fatigue failure criterion based on the maximum shear stress amplitude [Δτmax] on the 24 octahedral and 6 cube slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criterion reduces the scatter in uniaxial LCF test data considerably for PWA 1493 at 1200°F in air. Additionally, single crystal turbine blades used in the alternate advanced high-pressure fuel turbopump (AHPFTP/AT) are modeled using a large-scale three-dimensional finite element model. This finite element model is capable of accounting for material orthotrophy and variation in primary and secondary crystal orientation. Effects of variation in crystal orientation on blade stress response are studied based on 297 finite element model runs. Fatigue lives at critical points in the blade are computed using finite element stress results and the failure criterion developed. Stress analysis results in the blade attachment region are also presented. Results presented demonstrates that control of secondary and primary crystallographic orientation has the potential to significantly increase a component’s resistance to fatigue crack growth without adding additional weight or cost.

scholarly journals Fretting Stresses in Single Crystal Superalloy Turbine Blade Attachments

2000 ◽  
Vol 123 (2) ◽  
pp. 413-423 ◽  
Author(s):  
Nagaraj K. Arakere ◽  
Gregory Swanson
Keyword(s):  
Single Crystal ◽  
Contact Stress ◽  
Crystal Orientation ◽  
Rocket Engine ◽  
Turbine Blades ◽  
Nickel Base Superalloy ◽  
Attachment Region ◽  
Nickel Base ◽  
Fatigue Failures ◽  
Base Superalloy

Single crystal nickel base superalloy turbine blades are being utilized in rocket engine turbopumps and turbine engines because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. High cycle fatigue induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Blade attachment regions are prone to fretting fatigue failures. Single crystal nickel base superalloy turbine blades are especially prone to fretting damage because the subsurface shear stresses induced by fretting action at the attachment regions can result in crystallographic initiation and crack growth along octahedral planes. This paper presents contact stress evaluation in the attachment region for single crystal turbine blades used in the NASA alternate advanced high pressure fuel turbo pump for the space shuttle main engine. Single crystal materials have highly anisotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. Blades and the attachment region are modeled using a large-scale three-dimensional finite element model capable of accounting for contact friction, material anisotropy, and variation in primary and secondary crystal orientation. Contact stress analysis in the blade attachment regions is presented as a function of coefficient of friction and primary and secondary crystal orientation. Fretting stresses at the attachment region are seen to vary significantly as a function of crystal orientation. The stress variation as a function of crystal orientation is a direct consequence of the elastic anisotropy of the material. Fatigue life calculations and fatigue failures are discussed for the airfoil and the blade attachment regions.

The Influence of Crystal Orientation on the Elastic Stresses of a Single Crystal Nickel-Based Turbine Blade

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Michael W. R. Savage
Keyword(s):  
Single Crystal ◽  
Turbine Blade ◽  
Fatigue Resistance ◽  
Crystal Orientation ◽  
Turbine Blades ◽  
Casting Process ◽  
Directionally Solidified ◽  
Element Analysis ◽  
Angle Variation ◽  
Elastic Stresses

Single crystal nickel-based turbine blades are directionally solidified during the casting process with the crystallographic direction [001] aligned with the blade stacking axis. This alignment is usually controlled within 10 deg, known as the Primary angle. The rotation of the single crystal about the [001] axis is generally not controlled and this is known as the Secondary angle. The variation in Primary and Secondary angles relative to the blade geometry means that the stress response from blade to blade will be different, even for the same loading conditions. This paper investigates the influence of single crystal orientation on the elastic stresses of a CMSX-4 turbine blade root attachment using finite element analysis. The results demonstrate an appreciable variation in elastic stress when analyzed over the controlled Primary angle, and are further compounded by the uncontrolled Secondary angle. The maximum stress range will have a direct impact on the fatigue resistance of the turbine blade. By optimizing the Secondary angle variation the elastic stresses can be reduced, giving the potential to enhance the fatigue resistance of the turbine blade.

The Influence of Crystal Orientation on the Elastic Stresses of a Single Crystal Nickel-Based Turbine Blade

2011 ◽  
Author(s):  
Michael W. R. Savage
Keyword(s):  
Single Crystal ◽  
Turbine Blade ◽  
Fatigue Resistance ◽  
Crystal Orientation ◽  
Turbine Blades ◽  
Casting Process ◽  
Directionally Solidified ◽  
Element Analysis ◽  
Angle Variation ◽  
Elastic Stresses

Single crystal nickel-based turbine blades are directionally solidified during the casting process with the crystallographic direction [001] aligned with the blade stacking axis. This alignment is usually controlled within 10°, known as the Primary angle. The rotation of the single crystal about the [001] axis is generally not controlled and this is known as the Secondary angle. The variation in Primary and Secondary angles relative to the blade geometry means that the stress response from blade to blade will be different, even for the same loading conditions. This paper investigates the influence of single crystal orientation on the elastic stresses of a CMSX-4 turbine blade root attachment using finite element analysis. The results demonstrate an appreciable variation in elastic stress when analysed over the controlled Primary angle, and are further compounded by the uncontrolled Secondary angle. The maximum stress range will have a direct impact on the fatigue resistance of the turbine blade. By optimizing the Secondary angle variation the elastic stresses can be reduced, giving the potential to enhance the fatigue resistance of the turbine blade.

Two Methods of Studying Structure Perfection of Single Crystal Nickel-Based Superalloys

2013 ◽  
Vol 203-204 ◽  
pp. 177-180 ◽  
Author(s):  
Arkadiusz Onyszko ◽  
Jan Sieniawski ◽  
Włodzimierz Bogdanowicz ◽  
Hans Berger
Keyword(s):  
Single Crystal ◽  
Crystal Orientation ◽  
Turbine Blades ◽  
Vacuum Furnace ◽  
Aerospace Materials ◽  
X Ray ◽  
University Of Technology ◽  
Assembly Structure ◽  
Development Laboratory ◽  
Laue Method

The article presents the comparison of two methods: classical X-ray topography and the modern automatic X-ray OD-EFG diffractometer. Both methods were applied to study the crystal orientation of turbine blades of single crystal nickel-based superalloys. The solidification of a hollow assembly structure for 5 various blades was carried out by the Bridgman method at the Research and Development Laboratory for Aerospace Materials at Rzeszow University of Technology using an ALD Vacuum Technologies vacuum furnace. Ceramic moulds made of Al2O3 were used. The alloy temperature during casting into the mould amounted to 1550°C. The specimens for Laue method tests were cut out from the blades at withdrawal rates of 1, 2, 3, 4, and 5 mm/min.

High-Temperature Fatigue Properties of Single Crystal Superalloys in Air and Hydrogen

2001 ◽  
Author(s):  
Nagaraj K. Arakere
Keyword(s):  
High Pressure ◽  
Shear Stress ◽  
High Temperature ◽  
Fatigue Life ◽  
Single Crystal ◽  
Room Temperature ◽  
Turbine Blades ◽  
The Core ◽  
Blade Tip ◽  
Pressure Hydrogen

Hot section components in high performance aircraft and rocket engines are increasingly being made of single crystal nickel superalloys such as PWA1480, PWA1484, CMSX-4 and Rene N-4 as these materials provide superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over their polycrystalline counterparts. Fatigue failures in PWA1480 single crystal nickel-base superalloy turbine blades used in the Space Shuttle Main Engine (SSME) fuel turbopump are discussed. During testing many turbine blades experienced Stage II non-crystallographic fatigue cracks with multiple origins at the core leading edge radius and extending down the airfoil span along the core surface. The longer cracks transitioned from stage II fatigue to crystallographic stage I fatigue propagation, on octahedral planes. An investigation of crack depths on the population of blades as a function of secondary crystallographic orientation (β) revealed that for β = 45+/- 15 degrees tip cracks arrested after some growth or did not initiate at all. Finite element analysis of stress response at the blade tip, as a function of primary and secondary crystal orientation, revealed that there are preferential β orientations for which crack growth is minimized at the blade tip. To assess blade fatigue life and durability extensive testing of uniaxial single crystal specimens with different orientations has been tested over a wide temperature range in air and hydrogen. A detailed analysis of the experimentally determined Low Cycle Fatigue (LCF) properties for PWA1480 and SC 7-14-6 single crystal materials as a function of specimen crystallographic orientation is presented at high temperature (75 F – 1800 F) in high-pressure hydrogen and air. Fatigue failure parameters are investigated for LCF data of single crystal material based on the shear stress amplitudes on the 24 octahedral and 6 cube slip systems for FCC single crystals. The max shear stress amplitude [Δτmax] on the slip planes reduces the scatter in the LCF data and is found to be a good fatigue damage parameter, especially at elevated temperatures. The parameter Δτmax did not characterize the room temperature LCF data in high-pressure hydrogen well because of the noncrystallographic eutectic failure mechanism activated by hydrogen at room temperature. Fatigue life equations are developed for various temperature ranges and environmental conditions based on power-law curve fits of the failure parameter with LCF test data. These curve fits can be used for assessing blade fatigue life.

A Synthetical Numerical Model for Evaluating the Reliability of Turbine Blade

2002 ◽  
Author(s):  
Yonghui Xie ◽  
Di Zhang
Keyword(s):  
Fatigue Life ◽  
Numerical Model ◽  
Steam Turbine ◽  
Turbine Blade ◽  
Power Plants ◽  
Dynamic Stress ◽  
Turbine Blades ◽  
Dynamic Stress Analysis ◽  
Steam Turbine Blades ◽  
Blade Failure

Reliability of turbines is very important for power plants, and the most common blade failure normally result from forced vibration which lead to fatigue failure of blades. In this study, a synthetical numerical model has been developed to obtain more precise evaluation of the reliability of blades. At first, the model used to analyze the dynamic stress of steam turbine blades is investigated, base on the results of dynamic stress analysis, a model to evaluate the fatigue life of turbine blade has been developed, many factors such as manufacturing technology of blades and erosion operating environment are considered to get more accurate results for the fatigue life prediction of blades. At last, a 323 mm blade in a 75MW steam turbine is analyzed by the model developed in this paper, it is shown clearly that the model can provide some significant data to evaluate the reliability of blade.

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