scholarly journals Accurate Effective Stress Measures: Predicting Creep Life for 3D Stresses Using 2D and 1D Creep Rupture Simulations and Data

2021 ◽  
Author(s):  
Andrea Rovinelli ◽  
Mark C. Messner ◽  
David M. Parks ◽  
Ting-Leung Sham
Keyword(s):  
Effective Stress ◽  
Creep Rupture ◽  
Creep Life

Effects of microstructure and lattice misfit on creep life of Ni-based single crystal superalloy during long-term thermal exposure

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Wenyan Gan ◽  
Hangshan Gao ◽  
Haiqing Pei ◽  
Zhixun Wen
Keyword(s):  
Single Crystal ◽  
Rupture Life ◽  
Precipitation Amount ◽  
Lattice Misfit ◽  
Thermal Exposure ◽  
Phase Evolution ◽  
Creep Rupture ◽  
Simultaneous Increase ◽  
Creep Life ◽  
The Matrix

Abstract According to the microstructural evolution during longterm thermal exposure at 1100 °C, the creep rupture life of Ni-based single crystal superalloys at 980 °C/270 MPa was evaluated. The microstructure was characterized by means of scanning electron microscopy, X-ray diffraction and related image processing methods. The size of γ’ precipitates and the precipitation amount of topologically close-packed increased with the increase in thermal exposure time, and coarsening of the γ’ precipitates led to the simultaneous increase of the matrix channel width. The relationship between the creep rupture life and the lattice misfit of γ/γ’, the coarsening of γ’ precipitate and the precipitation of TCP phase are systematically discussed. In addition, according to the correlation between γ’ phase evolution and creep characteristics during thermal exposure, a physical model is established to predict the remaining creep life.

scholarly journals Creep rupture properties of bare and coated polycrystalline nickel-based superalloy Rene®80

2021 ◽  
pp. 36-36
Author(s):  
M.M. Barjesteh ◽  
S.M. Abbasi ◽  
K.Z. Madar ◽  
K. Shirvani
Keyword(s):  
Elevated Temperatures ◽  
Life Time ◽  
Creep Rupture ◽  
Polycrystalline Nickel ◽  
Creep Life ◽  
Nickel Based Superalloy ◽  
Platinum Aluminide ◽  
Rupture Properties ◽  
Low Activity ◽  
Rupture Behavior

Creep deformation is one of the life time limiting reasons for gas turbine parts that are subjected to stresses at elevated temperatures. In this study, creep rupture behavior of uncoated and platinum-aluminide coated Rene?80 has been determined at 760?C/657 MPa, 871?C/343 MPa and 982?C/190 Mpa in air. For this purpose, an initial layer of platinum with a thickness of 6?m was applied on the creep specimens. Subsequently, the aluminizing were formed in the conventional pack cementation method via the Low Temperature-High Activity (LTHA) and High Temperature-Low Activity (HTLA) processes. Results of creep-rupture tests showed a decrease in resistance to creep rupture of coated specimen, compared to the uncoated ones. The reductions in rupture lives in LTHA and HTLA methods at 760?C/657 MPa, 871?C/343 MPa and 982?C/190 MPa were almost (26% and 41.8%), (27.6% and 38.5%) and (22.4% and 40.3%), respectively as compared to the uncoated ones. However, the HTLA aluminizing method showed an intense reduction in creep life. Results of fractographic studies on coated and uncoated specimens indicated a combination of ductile and brittle failure mechanisms for all samples. Although, the base failure mode in substrate was grain boundary voids, cracks initiated from coating at 760?C/657MPa and 871?C/343. No cracking in the coating was observed at 982?C/190MPa.

Application and Standard Error Analysis of the Parametric Methods for Predicting the Creep Life of Type 316LN SS

2005 ◽  
Vol 297-300 ◽  
pp. 2272-2277 ◽  
Author(s):  
Woo Gon Kim ◽  
Song Nam Yoon ◽  
Woo Seog Ryu
Keyword(s):  
Experimental Data ◽  
Standard Error ◽  
Rupture Life ◽  
Large Error ◽  
Creep Rupture ◽  
Parametric Methods ◽  
Creep Life ◽  
Statistical Process ◽  
316Ln Ss ◽  
Type 316Ln Stainless Steel

To predict the creep-rupture life of type 316LN stainless steels which are major structural components of liquid metal reactors, a number of creep-rupture data were collected through literature survey and experimental data of KAERI. Using the data, the creep-rupture life was analyzed by means of the Larson-Miller, the Orr-Sherby-Dorn and the Manson-Haferd parametric methods. Polynomial equations for predicting the creep life were obtained. In order to analyze the acceptance and use of the parametric methods, standard error values were accurately investigated by statistical process of the creep data. As for the results, the three parametric methods are found to be favorable in predicting the creep life of type 316LN stainless steel. Each method did not generate a large error in the standard error of the estimate with variations of the temperatures, but the Orr-Sherby-Dorn and the Manson-Haferd methods showed a better agreement than the Larson-Miller one. Especially, at higher the 700oC, the Manson-Haferd method conformed well to the experimental data. The reason is because the Manson-Haferd method includes two constants of ta and Ta.

Creep Life of Ceramic Components Using a Finite Element Based Integrated Design Program (CARES/CREEP)

1996 ◽  
Author(s):  
Lynn M. Powers ◽  
Osama M. Jadaan ◽  
John P. Gyekenyesi
Keyword(s):  
Finite Element ◽  
High Temperatures ◽  
Failure Modes ◽  
Integrated Design ◽  
Systems Design ◽  
Creep Rupture ◽  
Creep Life ◽  
Time Step ◽  
Design Program ◽  
Structural Applications

The desirable properties of ceramics at high temperatures have generated interest in their use for structural applications such as in advanced turbine systems. Design lives for such systems can exceed 10,000 hours. The long life requirement necessitates subjecting the components to relatively low stresses. The combination of high temperatures and low stresses typically places failure for monolithic ceramics in the creep regime. The objective of this paper is to present a design methodology for predicting the lifetimes of structural components subjected to creep rupture conditions. This methodology utilizes commercially available finite element packages and takes into account the time varying creep strain distributions (stress relaxation). The creep life of a component is discretized into short time steps, during which, the stress and strain distributions are assumed constant. The damage is calculated for each time step based on a modified Monkman-Grant creep rupture criterion. Failure is assumed to occur when the normalized accumulated damage at any point in the component is greater than or equal to unity. The corresponding time will be the creep rupture life for that component. Examples are chosen to demonstrate the CARES/CREEP (Ceramics Analysis and Reliability Evaluation of Structures/CREEP) integrated design program which is written for the ANSYS finite element package. Depending on the components size and loading conditions, it was found that in real structures one of two competing failure modes (creep or slow crack growth) will dominate. Applications to benchmark problems and engine components are included.

Evaluation of Creep Properties of Alloy 690 Steam Generator Tubes at High Temperature Using Tube Specimen

2019 ◽  
Author(s):  
Jongmin Kim ◽  
Woogon Kim ◽  
Minchul Kim
Keyword(s):  
High Temperature ◽  
Steam Generator ◽  
Creep Test ◽  
Rupture Life ◽  
Creep Rupture ◽  
Severe Accident ◽  
High Temperature Creep ◽  
Creep Life ◽  
Temperature Creep ◽  
Alloy 690

Abstract Thermally induced steam generator (SG) tube failures caused by hot gases from a damaged reactor core can result in a containment bypass event and may lead to release of fission products to the environment. A typical severe accident scenario is a station blackout (SBO) with loss of auxiliary feedwater. Alloy 690 which has increased the Cr content has been replaced for the SG tube due to its high corrosion resistance against stress corrosion cracking (SCC). However, there is lack of research on the high temperature creep rupture and life prediction model of Alloy 690. In this study, creep test was performed to estimate the high temperature creep rupture life of Alloy 690. Based on reported creep data and creep test results of Alloy 690 in this study, creep life extrapolation was carried out using Larson-Miller Parameter (LMP), Orr-Sherby-Dorn (OSD), Manson-Haferd Parameter (MHP), and Wilshire’s approach. And a hyperbolic sine (sinh) function to determine master curves in LMP, OSD and MHP methods was used for improving the creep life estimation of Alloy 690 material.

scholarly journals Multiaxial Creep Life Prediction of Ceramic Structures Using Continuum Damage Mechanics and the Finite Element Method

1998 ◽  
Author(s):  
Osama M. Jadaan ◽  
Lynn M. Powers ◽  
John P. Gyekenyesi
Keyword(s):  
Life Prediction ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Creep Rupture ◽  
Creep Life ◽  
Current State ◽  
Creep Life Prediction ◽  
Uniaxial Creep ◽  
Multiaxial Creep ◽  
Temperature Time

High temperature and long duration applications of monolithic ceramics can place their failure mode in the creep rupture regime. A previous model advanced by the authors described a methodology by which the creep rupture life of a loaded component can be predicted. That model was based on the life fraction damage accumulation rule in association with the modified Monkman-Grant creep rupture criterion. However, that model did not take into account the deteriorating state of the material due to creep damage (e.g., cavitation) as time elapsed. In addition, the material creep parameters used in that life prediction methodology, were based on uniaxial creep curves displaying primary and secondary creep behavior, with no tertiary regime. The objective of this paper is to present a creep life prediction methodology based on a modified form of the Kachanov-Rabotnov continuum damage mechanics (CDM) theory. In this theory, the uniaxial creep rate is described in terms of stress, temperature, time, and the current state of material damage. This scalar damage state parameter is basically an abstract measure of the current state of material damage due to creep deformation. The damage rate is assumed to vary with stress, temperature, time, and the current state of damage itself. Multiaxial creep and creep rupture formulations of the CDM approach are presented in this paper. Parameter estimation methodologies based on nonlinear regression analysis are also described for both, isothermal constant stress states and anisothermal variable stress conditions This creep life prediction methodology was preliminarily added to the integrated design code. CARES/Creep (Ceramics Analysis and Reliability Evaluation of Structures/Creep), which is a postprocessor program to commercially available finite element analysis (FEA) packages. Two examples, showing comparisons between experimental and predicted creep lives of ceramic specimens, are used to demonstrate the viability of this methodology and the CARES/Creep program.

Optimization of NDE Reexamination Locations and Intervals for Grade 91 Piping System Girth Welds

2015 ◽  
Author(s):  
Marvin J. Cohn ◽  
Michael T. Cronin ◽  
Fatma G. Faham ◽  
David A. Bosko ◽  
Erick Liebl
Keyword(s):  
Crack Growth ◽  
Creep Crack Growth ◽  
Creep Rupture ◽  
Piping System ◽  
Creep Life ◽  
Stress Increase ◽  
Creep Crack ◽  
Grade 91 ◽  
Girth Welds ◽  
Stress Analyses

It has become apparent with the development of creep strength enhanced ferritic steels, the mandatory ASME B31.1 Chapter VII and the non-mandatory ASME B31.1 Appendix V guidelines require a more rigorous method to manage the Grade 91 piping integrity at Genesee Unit 3. Given the relatively young age of Genesee Unit 3, three questions have been asked: 1) when do the examinations start, 2) what locations should be examined first, and 3) how often should the same location be reexamined? To ensure that the best value is obtained from the reexamination budget, a five-step process can be effectively used to define and categorize the scope of each set of reexaminations in the girth weld integrity management program. The five processes are performing the following analyses: 1) an evaluation of the historical information, 2) piping system hot and cold walkdowns, 3) as-designed and as-found piping stress analyses, 4) creep life consumption evaluations, including elastic and inelastic axial and radial stress redistributions, and 5) creep crack growth curve analyses. Reexaminations of the few critical lead-the-fleet weldments are performed with lower examination costs and higher confidence. Evaluations of the Genesee Unit 3 main steam (MS) piping system revealed that the applicable weldment stress is probably the most significant parameter in determining the Grade 91 girth weld critical reexamination locations and intervals. ASME B31.1 piping stress analyses of the MS piping system have sustained load stress variations of more than 100% among the girth welds. The lower bound American Petroleum Institute (API) 579 creep rupture equation for Grade 91 operating at 1,060°F (571°C) indicates that the creep life is a function of stress to the power of 8.9; consequently, a 15% stress increase results in about 2/3 reduction of creep rupture life. Creep crack growth analyses of several of the MS piping system weldments revealed that the creep crack growth time to grow from 1/8 inch to through-wall is a function of stress to the power of 8.8; consequently, a 15% stress increase results in about 2/3 reduction of time for a 1/8-inch crack to grow through-wall. This evaluation reveals that a few critical lead-the-fleet locations should be reexamined most frequently and justification can be provided for much longer reexamination intervals of the remaining girth welds with much lower applied stresses.

Enhanced Creep Life Evaluations for Grade 91 Circumferential Weldments

2017 ◽  
Author(s):  
Marvin J. Cohn
Keyword(s):  
Applied Stress ◽  
Hoop Stress ◽  
Axial Stress ◽  
Creep Damage ◽  
Creep Rupture ◽  
Piping System ◽  
Remaining Life ◽  
Creep Life ◽  
Rupture Properties ◽  
Applied Stresses

The basic power piping creep life calculations consider the important variables of time, temperature and stress for the creep rupture properties of the unique material. Some engineering evaluations of remaining life estimate the applied stress as the design stress obtained from a conventional piping stress analysis. Other remaining life evaluations may assume that a conservative estimate of the applied stress is no greater than the hoop stress due to pressure. The creep rupture properties of the unique material are usually obtained from the base material creep rupture properties. The typical methodologies to estimate remaining life do not consider the actual applied stress due to malfunctioning supports, multiaxial stress effects, axial and through-wall creep redistribution, time-dependent material-specific weldment creep rupture properties, residual welding stresses, and actual operating temperatures and pressures. It has been determined that the initiation and propagation of Grade 91 creep damage is a function of stress to about the power of 9 at higher applied stresses. There have been many examples of malfunctioning piping supports creating unintended high stresses. When the axial stress is nearly as high as the hoop stress, the applicable corresponding uniaxial stress for creep rupture life is increased about 30%. Multiaxial stress effects in circumferential weldments (e.g., when the axial stress is nearly as high as the hoop stress) can reduce the weldment creep life to less than 1/6th of the predicted life assuming a uniaxial stress or hoop stress due to pressure only. Since 2012, the ASME B31.1 Code has required that significant piping displacement variations from the expected design displacements shall be considered to assess the piping system’s integrity [1]. This paper discusses a strategy for an enhanced creep life evaluation of power piping circumferential weldments. Piping stresses can vary by a factor greater than 2.0. Consequently, the range of circumferential weldment creep rupture lives for a single piping system may vary by a factor as high as 40. Although there is uncertainty in the operating times at temperatures and pressures, all of the weldments within the piping system have the same time, temperatures, and pressures, so the corresponding uncertainties for these three attributes are normalized within the same piping system. Since the applied stresses are the most important weld-to-weld variable within a piping system, it is necessary to have an accurate evaluation of the applied stresses to properly rank the creep rupture lives of the circumferential weldments. This methodology has been successfully used to select the lead-the-fleet creep damage in circumferential weldments over the past 15 years.

scholarly journals Influence of thermal ageing on creep rupture mechanism and creep life of P92 ferritic steel

2020 ◽  
Vol 7 (8) ◽  
pp. 086517
Author(s):  
Hui Kang ◽  
Junjie Shen ◽  
Shanjun Zhang ◽  
Hongguang Han ◽  
Fuyong Hu ◽  
...  
Keyword(s):  
Ferritic Steel ◽  
Thermal Ageing ◽  
Creep Rupture ◽  
Creep Life ◽  
Rupture Mechanism

Influence of Testing Environment and Radius of Die Shoulder on SP Creep Rupture Life

2011 ◽  
Author(s):  
Ken-ichi Kobayashi ◽  
Masahiro Kaneko ◽  
Hideo Koyama ◽  
Gavin C. Stratford ◽  
Masaaki Tabuchi
Keyword(s):  
Oxide Scale ◽  
Rupture Life ◽  
High Vacuum ◽  
Creep Rupture ◽  
Test Duration ◽  
Creep Life ◽  
Destructive Testing ◽  
Creep Tests ◽  
Testing Environment ◽  
High Temperature Components

Small Punch, hereinafter designated as SP, creep test has been proposed as a semi destructive testing methodology to examine the residual creep life of high temperature components. Employing low alloy steel, a series of SP creep tests were conducted on disc specimens at 600°C in air and in high vacuum to investigate the influence of oxide scale on the creep rupture life. Thickness of the oxide scale on disc specimens in air increased with the test duration, e.g., about 30μm in thickness after 400 hours. The creep rupture life in air reduced to a half of the life in vacuum due to an increase in the actual stress in the disc thickness. In addition, the magnitude of radius of a lower die shoulder affected the SP creep rupture life. The influence of this radius on the SP creep life was also studied experimentally and numerically. The creep rupture life with the die radius of 0.5mm had twice longer than that with 0.6mm. This fact was also demonstrated by the FE analysis.

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