Fatigue damage characterisation of MarBN steel for high temperature flexible operating conditions

2016 ◽  
Vol 231 (1-2) ◽  
pp. 23-37 ◽  
Author(s):  
EM O’Hara ◽  
NM Harrison ◽  
BK Polomski ◽  
RA Barrett ◽  
SB Leen
Keyword(s):  
High Temperature ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Microstructural Analysis ◽  
Strain Range ◽  
Fatigue Behaviour ◽  
Operating Conditions ◽  
Fracture Mechanisms ◽  
Published Data ◽  
Cycle Fatigue

This article is concerned with the high temperature low cycle fatigue behaviour of a new nano-strengthened martensitic-ferritic steel, MarBN. A range of strain-controlled, low cycle fatigue tests are presented on MarBN at 600 ℃ and 650 ℃, and compared with previously published data for a current state-of-the-art material, P91 steel, including microstructural analysis of the fracture mechanisms. A modified Chaboche damage law, incorporating Coffin–Manson life prediction, is implemented within a hyperbolic sine unified cyclic viscoplastic constitutive model. Calibration and validation of the model with respect to the effects of strain-rate and strain-range is performed based on an optimisation procedure for identification of the material parameters. The cyclic viscoplasticity model with damage successfully predicts fatigue damage evolution and life in the cyclically softening materials, MarBN and P91.

scholarly journals A review of low-cycle fatigue of Alloy 617 for use in VHTR components: Experimental outlook

2018 ◽  
Vol 159 ◽  
pp. 02049 ◽  
Author(s):  
Rando Tungga Dewa ◽  
Jeong-Hun Park ◽  
Seon-Jin Kim ◽  
Woo-Gon Kim ◽  
Eung-Seon Kim ◽  
...  
Keyword(s):  
High Temperature ◽  
Oxidation Behavior ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Fatigue Behaviour ◽  
Cycle Fatigue ◽  
Alloy 617 ◽  
Surface Cracking ◽  
The Matrix ◽  
Lower Temperature

The effect of strain range and temperature on the low-cycle fatigue behaviour and microstructure change during cyclic deformation of Alloy 617 for use in very high temperature gas-cooled reactor components were studied at elevated temperature starting from ambient condition. Increasing the strain range and the temperature was noticed to reduce the fatigue resistance of nickel-based Alloy 617 due to facilitating the transformation behavior of the carbides in the grain interior, precipitates along the grain boundary, and oxidation behavior inducing surface connected precipitates cracking. Initial hardening behavior was observed at room temperature condition during cyclic due to the pile-up dislocation of micro-precipitates. The grain size was also taking a role due to the formation of an obstacle in the matrix. In the high temperature regime, the alloy 617 was found to soften for its entire life due to the fast recovery deformation, proved by its higher plasticity compared with lower temperature. The deformation behavior also showing high environmentally assisted damage. Oxidation behavior was found to become the primary crack initiation, resulting in early intergranular surface cracking.

High-Temperature Low-Cycle Fatigue Behavior of MarBN at 600 °C

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Richard A. Barrett ◽  
Eimear M. O'Hara ◽  
Padraic E. O'Donoghue ◽  
Sean B. Leen
Keyword(s):  
High Temperature ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Fatigue Behavior ◽  
Strain Range ◽  
Material Model ◽  
Cyclic Softening ◽  
Cyclic Strength ◽  
Cycle Fatigue ◽  
Viscoplastic Material

This paper presents the high-temperature low-cycle fatigue (HTLCF) behavior of a precipitate strengthened 9Cr martensitic steel, MarBN, designed to provide enhanced creep strength and precipitate stability at high temperature. The strain-controlled test program addresses the cyclic effects of strain-rate and strain-range at 600 °C, as well as tensile stress-relaxation response. A recently developed unified cyclic viscoplastic material model is implemented to characterize the complex cyclic and relaxation plasticity response, including cyclic softening and kinematic hardening effects. The measured response is compared to that of P91 steel, a current power plant material, and shows enhanced cyclic strength relative to P91.

Low-Cycle Fatigue under Biaxial Stress

1974 ◽  
Vol 188 (1) ◽  
pp. 657-671 ◽  
Author(s):  
M. W. Parsons ◽  
K. J. Pascoe
Keyword(s):  
Austenitic Steel ◽  
Abrupt Change ◽  
Low Cycle Fatigue ◽  
Axial Loading ◽  
Strain Range ◽  
Fatigue Behaviour ◽  
Biaxial Stress ◽  
Cycle Fatigue ◽  
Biaxial Strain ◽  
Total Strain Range

The low-cycle fatigue behaviour of a ferritic and an austenitic steel have been studied under various conditions of reversed biaxial strain. These cyclically softened and hardened respectively. In all cases, relationships of the form were found between total strain range Δε t and life Nf for lives in the range 102−105 cycles, with an abrupt change of β at intermediate lives. Variation of state of strain affected both β and κ. Various theories for the correlation of fatigue behaviour under multi-axial loading have been reviewed and compared with these results. None was found to account adequately for the effect of straining régime with the materials tested.

Influence of Creep on Low-Cycle Fatigue Life Assessment of Ultra-Supercritical Steam Turbine Rotor

2014 ◽  
Author(s):  
W. Z. Wang ◽  
J. H. Zhang ◽  
H. F. Liu ◽  
Y. Z. Liu
Keyword(s):  
High Temperature ◽  
Steam Turbine ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Turbine Rotor ◽  
High Temperature Creep ◽  
Cycle Fatigue ◽  
Term Operation ◽  
Start Up

Linear damage method is widely used to calculate low-cycle fatigue damage of turbine rotor in the long-term operation without fully considering the interaction between creep and low cycle fatigue. However, with the increase of steam turbine pressure and temperature, the influence of high-temperature creep on the strain distribution of turbine rotor becomes significant. Accordingly, the strain for each start-up or shut-down process is different. In the present study, the stress and strain during 21 iterations of continuous start-up, running and shut-down processes was numerically investigated by using the finite element analysis. The influence of high-temperature creep on low cycle fatigue was analyzed in terms of equivalent strain, Mises stress and low cycle fatigue damage. The results demonstrated that the life consumption of turbine rotor due to low cycle fatigue in the long-term operation of startup, running and shutdown should be determined from the full-time coverage of the load of turbine rotor.

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