Thermomechanical Fatigue Behavior of a Directionally Solidified Ni-Base Superalloy

2005 ◽  
Vol 127 (3) ◽  
pp. 325-336 ◽  
Author(s):  
M. M. Shenoy ◽  
A. P. Gordon ◽  
D. L. McDowell ◽  
R. W. Neu
Keyword(s):  
Crack Initiation ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Material Behavior ◽  
Directionally Solidified ◽  
Creep Tests ◽  
Physically Based ◽  
Estimation Scheme ◽  
Crack Initiation Life ◽  
Base Superalloy

A continuum crystal plasticity model is used to simulate the material behavior of a directionally solidified Ni-base superalloy, DS GTD-111, in the longitudinal and transverse orientations. Isothermal uniaxial fatigue tests with hold times and creep tests are conducted at temperatures ranging from room temperature (RT) to 1038°C to characterize the deformation response. The constitutive model is implemented as a User MATerial subroutine (UMAT) in ABAQUS (2003, Hibbitt, Karlsson, and Sorensen, Inc., Providence, RI, v6.3) and a parameter estimation scheme is developed to obtain the material constants. Both in-phase and out-of-phase thermo-mechanical fatigue tests are conducted. A physically based model is developed for correlating crack initiation life based on the experimental life data and predictions are made using the crack initiation model.

scholarly journals Probabilistic Modeling of Slip System-Based Shear Stresses and Fatigue Behavior of Coarse-Grained Ni-Base Superalloy Considering Local Grain Anisotropy and Grain Orientation

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 813 ◽  
Author(s):  
Engel ◽  
Mäde ◽  
Lion ◽  
Moch ◽  
Gottschalk ◽  
...  
Keyword(s):  
Finite Element ◽  
Crack Initiation ◽  
Test Data ◽  
Grain Orientation ◽  
Fatigue Behavior ◽  
Coarse Grained ◽  
Shear Stresses ◽  
Grain Sizes ◽  
Crack Initiation Life ◽  
Base Superalloy

New probabilistic lifetime approaches for coarse grained Ni-base superalloys supplement current deterministic gas turbine component design philosophies; in order to reduce safety factors and push design limits. The models are based on statistical distributions of parameters, which determine the fatigue behavior under high temperature conditions. In the following paper, Low Cycle Fatigue (LCF) test data of several material batches of polycrystalline Ni-base superalloy René80 with different grain sizes and orientation distribution (random and textured) is presented and evaluated. The textured batch, i.e., with preferential grain orientation, showed higher LCF life. Three approaches to probabilistic crack initiation life modeling are presented. One is based on Weibull distributed crack initiation life while the other two approaches are based on probabilistic Schmid factors. In order to create a realistic Schmid factor distribution, polycrystalline finite element models of the specimens were generated using Voronoi tessellations and the local mechanical behavior investigated in dependence of different grain sizes and statistically distributed grain orientations. All models were first calibrated with test data of the material with random grain orientation and then used to predict the LCF life of the material with preferential grain orientation. By considering the local multiaxiality and resulting inhomogeneous shear stress distributions, as well as grain interaction through polycrystalline Finite Element Analysis (FEA) simulation, the best consistencies between predicted and observed crack initiation lives could be achieved.

Effect of Recrystallization on Low-Cycle Fatigue Behavior of DZ4 Directionally-Solidified Superalloy

2006 ◽  
Vol 306-308 ◽  
pp. 175-180 ◽  
Author(s):  
Hui Ji Shi ◽  
Hai Feng Zhang ◽  
Yan Qing Wu
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Grain Boundaries ◽  
Shot Peening ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Nickel Base Superalloy ◽  
Directionally Solidified ◽  
Crack Initiation Life

Effect of recrystallization on DZ4 directionally-solidified nickel-base superalloy was investigated both at room temperature and high temperature of 673K. In-situ SEM surface observation were performed. Experimental results reveal that the material performance is strongly influenced by surface recrystallization layer. All specimens were prepared under conditions of shot peening and 4h 1220°C high temperature annealing. Different shot peening pressure specimens have different recrystallization states. High shot penning pressure specimens have clear and straight grain boundaries and the grain size appears to be a little bit larger. Recrystallization state seems not only affect the fatigue life, but also the crack initiation pattern and crack initiation life. Low shot peening pressure specimens have much lower fatigue life which is around 8-10% of virgin one, and SEM Real-time observation reveals that channeling cracks initiated at the early stage of fatigue life. High shot peening pressure specimens have higher fatigue life comparing to low shot peening pressure specimens, although it’s almost half lower than the virgin one, and cracks initiated not until middle or latter stage of fatigue life. Crack initiation life is also much longer than those of low shot peening pressure. Low shot peening pressure specimens seems not fully recrystallized, and its grain boundaries are much fragile which is responsible for high density microcracks initiation, and finally leads to the failure. Further nano-indention experiments on surface recrystallized layers show that higher shot peening recrystallized layers have much lower elastic module, which may explain the longer crack initiation life.

Fatigue Behavior of Circumferentially Notched Round Bars of Austenitic Stainless Steel Under Torsional and Axial Loads

2010 ◽  
Author(s):  
Masao Itatani ◽  
Keisuke Tanaka ◽  
Isao Ohkawa ◽  
Takehisa Yamada ◽  
Toshiyuki Saito
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Static Tension ◽  
Cyclic Torsion ◽  
Cyclic Tension ◽  
Crack Initiation Life

Fatigue tests of smooth and notched round bars of austenitic stainless steels SUS316NG and SUS316L were conducted under cyclic tension and cyclic torsion with and without static tension. Fatigue strength under fully reversed (R=−1) cyclic tension once increased with increasing stress concentration factor up to Kt=1.5, but it decreased from Kt=1.5 to 2.5. Fatigue life increased with increasing stress concentration under pure cyclic torsion, while it decreased with increasing stress concentration under cyclic torsion with static tension. From the measurement of fatigue crack initiation and propagation lives using electric potential drop method, it was found that the crack initiation life decreased with increasing stress concentration and the crack propagation life increased with increasing stress concentration under pure cyclic torsion. Under cyclic torsion with static tension, the crack initiation life also decreased with increasing stress concentration but the crack propagation life decreased or not changed with increasing stress concentration then the total fatigue life of sharper notched specimen decreased. It was also found that the fatigue life of smooth specimen under cyclic torsion with static tension was longer than that under pure cyclic torsion. This behavior could be explained based on the cyclic strain hardening under non-proportional loading and the difference in crack path with and without static tension.

Efficient Methodologies for Determining Temperature-Dependent Parameters of a Ni-Base Superalloy Crystal Viscoplasticity Model for Cyclic Loadings

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
M. M. Kirka ◽  
D. J. Smith ◽  
R. W. Neu
Keyword(s):  
Fatigue Behavior ◽  
Deformation Mechanisms ◽  
Turbine Engines ◽  
Nickel Base Superalloy ◽  
Gas Turbine Engines ◽  
Directionally Solidified ◽  
Temperature Dependent ◽  
Nickel Base ◽  
Calibration Time ◽  
Base Superalloy

The prediction of temperature-dependent fatigue deformation and damage in directionally solidified and single-crystal nickel-base superalloy components used in the hot section of gas turbine engines requires a constitutive model that accounts for the crystal orientation in addition to the changing deformation mechanisms and rate dependencies from room temperature to extremes of the use temperature (e.g., 1050 °C). Crystal viscoplasticity (CVP) models are ideal for accounting for all of these dependencies. However, as the models become more physically realistic in capturing the true cyclic deformation mechanisms, increases the requirements to achieve an accurate model calibration. As a result, CVP models have yet to become viable for life analysis in industry. To make CVP models an industry relevant tool, the calibration times must be reduced. This paper explores methods to reduce the calibration time. First, a series of special calibration experiments are conceived and conducted on each relevant orientation and microstructure. Second, a set of parameterization protocols are used to minimize parameter interdependencies that reduce the amount of iteration required during the calibration. These experimental and calibration protocols are exercised using the CVP model of Shenoy et al. (2005, “Thermomechanical Fatigue Behavior of a Directionally Solidified Ni-Base Superalloy,” ASME J. Eng. Mater. Technol., 127(3), pp. 325–336) by calibrating a directionally solidified Ni-base superalloy across an industry relevant temperature range of 20 °C to 1050 °C.

Brittle and Ductile Creep Rupture Life Prediction of 1CrMoV Steel Notched Thick Plates

1990 ◽  
Vol 112 (3) ◽  
pp. 225-232 ◽  
Author(s):  
K. Ando ◽  
Y. Takeda ◽  
K. Takezoe
Keyword(s):  
Crack Initiation ◽  
Damage Mechanics ◽  
Notch Root ◽  
Rupture Life ◽  
Prediction Method ◽  
Creep Rupture ◽  
Material Behavior ◽  
Analytical Prediction ◽  
Crack Initiation Life ◽  
Creep Rupture Test

An analytical prediction method of brittle and ductile creep rupture life of 1CrMoV steel notched thick plate is proposed. Rupture time is evaluated as a sum of crack initiation life ti and crack growth life tp. In the case of ductile creep at high stresses, ti is evaluated by the creep deformation criteria. In addition, in the case of brittle creep at low stresses, ti is evaluated by Kachanov’s damage mechanics theory. Materials constants in Kachanov’s theory can be determined by the relatively short-term creep rupture test of notched specimen, etc., according to the present method. Creep rupture test, interrupted creep test, and micro-structural observation, have been used, which can explain the variety of material behavior, i.e., notch weakening at low stresses and notch strengthening at high stresses. In addition, in this analysis the analytically estimated creep crack initiation life corresponds to the time to creep void initiation just inside the notch root.

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