Application of Damage Concepts to Predict Creep-Fatigue Failures

1979 ◽  
Vol 101 (3) ◽  
pp. 284-292 ◽  
Author(s):  
J. Lemaitre ◽  
A. Plumtree
Keyword(s):  
High Temperature ◽  
High Frequency ◽  
Low Frequency ◽  
Strain Range ◽  
Ofhc Copper ◽  
Unified Approach ◽  
Alloy 800 ◽  
Sequential Tests ◽  
Creep Fatigue ◽  
Fatigue Failures

The damage concept has been developed in terms of strain range in order to give a unified approach to high temperature failure. Interactive tests have been carried out on OFHC copper at 540°C and Sanicro 31 (Alloy 800) at 600°C. For the former, combined strain controlled low frequency and high frequency tests were undertaken whereas the latter metal was subjected to sequential tests involving monotonic creep and high frequency cycling. The damage concept based on non-linear accumulation predicted lives which were in agreement with those observed experimentally for the two materials.

scholarly journals On Creep Fatigue Interaction of Components at Elevated Temperature

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Daniele Barbera ◽  
Haofeng Chen ◽  
Yinghua Liu
Keyword(s):  
High Temperature ◽  
Mechanical Load ◽  
Direct Method ◽  
Bending Moment ◽  
Strain Range ◽  
Cyclic Plasticity ◽  
Element Analysis ◽  
Total Strain Range ◽  
Creep Fatigue ◽  
A Direct Method

The accurate assessment of creep–fatigue interaction is an important issue for industrial components operating with large cyclic thermal and mechanical loads. An extensive review of different aspects of creep fatigue interaction is proposed in this paper. The introduction of a high temperature creep dwell within the loading cycle has relevant impact on the structural behavior. Different mechanisms can occur, including the cyclically enhanced creep, the creep enhanced plasticity and creep ratchetting due to the creep fatigue interaction. A series of crucial parameters for crack initiation assessment can be identified, such as the start of dwell stress, the creep strain, and the total strain range. A comparison between the ASME NH and R5 is proposed, and the principal differences in calculating the aforementioned parameters are outlined. The linear matching method (LMM) framework is also presented and reviewed, as a direct method capable of calculating these parameters and assessing also the steady state cycle response due to creep and cyclic plasticity interaction. Two numerical examples are presented, the first one is a cruciform weldment subjected to cyclic bending moment and uniform high temperature with different dwell times. The second numerical example considers creep fatigue response on a long fiber reinforced metal matrix composite (MMC), which is subjected to a cycling uniform thermal field and a constant transverse mechanical load. All the results demonstrate that the LMM is capable of providing accurate solutions, and also relaxing the conservatisms of the design codes. Furthermore, as a direct method, it is more efficient than standard inelastic incremental finite element analysis.

Constitutive Modeling of Haynes 230 for High Temperature Fatigue-Creep Interactions

2014 ◽  
Author(s):  
Paul R. Barrett ◽  
Raasheduddin Ahmed ◽  
Tasnim Hassan
Keyword(s):  
High Temperature ◽  
Nuclear Power ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Model Development ◽  
Strain Range ◽  
Uniaxial Stress ◽  
Cycle Fatigue ◽  
Modeling Framework ◽  
Creep Fatigue

Non-linear stress analysis for high temperature cyclic viscoplasticity is increasingly becoming an important modeling framework for many industries. Simplified analyses are found to be insufficient in accurately predicting the life of components; such as a gas turbine engine of an airplane or the intermediate-heat exchanger of a nuclear power plant. As a result, advanced material models for simulating nonlinear responses at room to high temperature are developed and experimentally validated against a broad set of low-cycle fatigue responses; such as creep, fatigue, and their interactions under uniaxial stress states. . This study will evaluate a unified viscoplastic model based on nonlinear kinematic hardening (Chaboche type) with several added features of strain-range-dependence, rate-dependence, temperature-dependence, static recovery, and mean-stress-evolution for Haynes 230database. Simulation-based model development for isothermal creep-fatigue responses are all critically evaluated for the developed model. The robustness of the constitutive model is demonstrated and weaknesses of the model to accurately predict low-cycle fatigue responses are identified. Paper published with permission.

Cuprate High Temperature Superconductors and the Vision for Room Temperature Superconductivity

SPIN ◽  
2017 ◽  
Vol 07 (02) ◽  
pp. 1750006 ◽  
Author(s):  
Dennis M. Newns ◽  
Glenn J. Martyna ◽  
Chang C. Tsuei
Keyword(s):  
High Temperature ◽  
High Frequency ◽  
Room Temperature ◽  
Phonon Frequency ◽  
High Temperature Superconductors ◽  
Low Frequency ◽  
Unconventional Superconductivity ◽  
Superconducting Transition ◽  
Strongly Coupled ◽  
Room Temperature Superconductivity

Superconducting transition temperatures of 164 K in cuprate high temperature superconductors (HTS) and recently 200 K in H3S under high pressure encourage us to believe that room temperature superconductivity (RTS) might be possible. In considering paths to RTS, we contrast conventional (BCS) SC, such as probably manifested by H3S, with the unconventional superconductivity (SC) in the cuprate HTS family. Turning to SC models, we show that in the presence of one or more van Hove singularities (vHs) near the Fermi level, SC mediated by classical phonons ([Formula: see text]phonon frequency) can occur. The phonon frequency in the standard [Formula: see text] formula is replaced by an electronic cutoff, enabling a much higher [Formula: see text] independent of phonon frequency. The resulting [Formula: see text] and isotope shift plot versus doping strongly resembles that seen experimentally in HTS. A more detailed theory of HTS, which involves mediation by classical phonons, satisfactorily reproduces the chief anomalous features characteristic of these materials. We propose that, while a path to RTS through an H3S-like scenario via strongly-coupled ultra-high frequency phonons is attractive, features perhaps unavailable at ordinary pressures, a route involving SC mediated by classical phonons which can be low frequency may be found.

scholarly journals A Miniaturized Thin-Plate Low Cycle Fatigue Test Method at Elevated Temperature

2021 ◽  
Author(s):  
Li M. ◽  
Maskill S. ◽  
Wen Z.X. ◽  
Yue Z.F. ◽  
Sun W.
Keyword(s):  
High Temperature ◽  
Thin Plate ◽  
Reference Strain ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Test Method ◽  
Data Conversion ◽  
Creep Fatigue ◽  
Equivalent Conditions ◽  
Good Agreement

This study aims to develop a high temperature LCF test method using a non-standard miniature thin-plate (MTP) specimen in order to characterize cyclic visco-plasticity behavior of component materials. For demonstration, fully reversed strain-range controlled LCF and creep-fatigue (CF) tests at 600 °C have been performed for a martensitic steel using both standard-sized full-scale (SSFS) and MTP specimens. A scaling factor is determined using cyclic visco-plastic finite element (FE) for geometry constraint evaluation and data conversion based on the reference strain approach. The equivalent energy principal is proposed to assess the geometry constraint effect that non-standard MTP specimen has. The high temperature LCF results from the MTP specimen based on the proposed testing methodology have shown a good agreement with SSFS specimen data under equivalent conditions. The methodology can therefore be used to conduct accurate transferability to achieve equivalent LCF behavior between the conventional standard specimen and the MTP specimen.

scholarly journals Constitutive Modeling of High Temperature Uniaxial Creep-Fatigue and Creep-Ratcheting Responses of Alloy 617

2013 ◽  
Author(s):  
P. G. Pritchard ◽  
L. Carroll ◽  
T. Hassan
Keyword(s):  
High Temperature ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Cyclic Hardening ◽  
Parameter Determination ◽  
Model Framework ◽  
Alloy 617 ◽  
North Carolina State University ◽  
Uniaxial Creep ◽  
Creep Fatigue

Inconel Alloy 617 is a high temperature creep and corrosion resistant alloy and is a leading candidate for use in Intermediate Heat Exchangers (IHX) of the Next Generation Nuclear Plants (NGNP). The IHX of the NGNP is expected to experience operating temperatures in the range of 800°–950°C, which is in the creep regime of Alloy 617. A broad set of uniaxial, low-cycle fatigue, fatigue-creep, ratcheting, and ratcheting-creep experiments are conducted in order to study the fatigue and ratcheting responses, and their interactions with the creep response at high temperatures. A unified constitutive model developed at North Carolina State University is used to simulate these experimental responses. The model is developed based on the Chaboche viscoplastic model framework. It includes cyclic hardening/softening, strain rate dependence, strain range dependence, static and dynamic recovery modeling features. For simulation of the alloy 617 responses, new techniques of model parameter determination are developed for optimized simulations. This paper compares the experimental responses and model simulations for demonstrating the strengths and shortcomings of the model.

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