An Approach for Nondestructive Remaining Life Estimation of High Temperature Materials for Creep-Fatigue Failure

1992 ◽  
pp. 137-142
Author(s):  
M. Hashimoto ◽  
M. Okazaki ◽  
T. Yada
Keyword(s):  
High Temperature ◽  
Fatigue Failure ◽  
Remaining Life ◽  
Life Estimation ◽  
High Temperature Materials ◽  
Creep Fatigue

Creep-Fatigue Strength of Long-Term Post-Service 2 · 1/4 Cr-1 · Mo Steel and Remaining Life Estimation

1991 ◽  
Vol 113 (4) ◽  
pp. 549-555 ◽  
Author(s):  
M. Okazaki ◽  
M. Hashimoto ◽  
T. Mochizuki
Keyword(s):  
High Temperature ◽  
Fatigue Strength ◽  
Fatigue Damage ◽  
Estimation Method ◽  
Remaining Life ◽  
Life Estimation ◽  
Creep Fatigue ◽  
Long Time ◽  
Longitudinal Ultrasonic Wave

Creep-fatigue strength of post-service 2 · 1/4 Cr-1 · Mo steel used for about one hundred-thousand hours in a fossil fuel power plant was studied. The creep-fatigue strength of the post-service material was lower than that of the virgin material, whereas it was comparable to that of thermally aged material, which was artificially exposed at high temperature for a long time so that it had an equivalent value of the Larson-Miller parameter to the post-service material. The nondestructive detection of the long-term degradation damage due to long-term thermal aging, as well as due to creep-fatigue, was also investigated by applying an ultrasonic technique. It was found that the energy attenuation coefficient, α, which is defined by the ratio of input to output energies of a longitudinal ultrasonic wave, had a good correlation with creep-fatigue damage in the virgin, aged and post-service materials; and hence, α was a successful parameter to detect creep-fatigue damage. Based on the results thus obtained, a new remaining life estimation method for creep-fatigue of in-service high-temperature materials was proposed. The application of the method to the post-service material tested gave good predicted results.

Creep-Fatigue Interaction Effects On Pressure-Reducing Valve Under Cyclic Thermo-Mechanical Loadings Using Direct Cyclic Method

2021 ◽  
Author(s):  
Nak-Kyun Cho ◽  
Youngjae Choi ◽  
Haofeng Chen
Keyword(s):  
High Temperature ◽  
Power Plant ◽  
Fatigue Failure ◽  
Material Properties ◽  
Structural Integrity ◽  
Direct Method ◽  
Element Model ◽  
Critical Loading ◽  
Creep Fatigue ◽  
Pressure Reducing Valve

Abstract Supercritical boiler system has been widely used to increase efficiency of electricity generation in power plant industries. However, the supercritical operating condition can seriously affect structural integrity of power plant components due to high temperature that causes degradation of material properties. Pressure reducing valve is an important component being employed within a main steam line of the supercritical boiler, which occasionally thermal-fatigue failure being reported. This research has investigated creep-cyclic plastic behaviour of the pressure reducing valve under combined thermo-mechanical loading using a numerical direct method known as extended Direct Steady Cyclic Analysis of the Linear Matching Method Framework (LMM eDSCA). Finite element model of the pressure-reducing valve is created based on a practical valve dimension and temperature-dependent material properties are applied for the numerical analysis. The simulation results demonstrate a critical loading component that attributes creep-fatigue failure of the valve. Parametric studies confirm the effects of magnitude of the critical loading component on creep deformation and total deformation per loading cycle. With these comprehensive numerical results, this research provides engineer with an insight into the failure mechanism of the pressure-reducing valve at high temperature.

Fatigue

1989 ◽  
pp. 111-182
Keyword(s):  
Fatigue Crack ◽  
High Temperature ◽  
Fatigue Crack Growth ◽  
Thermal Fatigue ◽  
Low Cycle Fatigue ◽  
Remaining Life ◽  
Material Defects ◽  
Processing History ◽  
Creep Fatigue ◽  
Tools And Techniques

Abstract This chapter describes the phenomenological aspects of fatigue and how to assess its effect on the life of components operating in high-temperature environments. It explains how fatigue is measured and expressed and how it is affected by loading conditions (stress cycles, amplitude, and frequency) and factors such as temperature, material defects, component geometry, and processing history. It provides a detailed overview of the damage mechanisms associated with high-cycle and low-cycle fatigue as well as thermal fatigue, creep-fatigue, and fatigue-crack growth. It also demonstrates the use of tools and techniques that have been developed to quantify fatigue-related damage and its effect on the remaining life of components.

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