scholarly journals Effect of Internal Pressurization on the Creep-Fatigue Performance of Alloy 617 Based on Simplified Model Test Method

2019 ◽  
Author(s):  
Y. Wang ◽  
B. Jetter ◽  
T.-L. Sham
Keyword(s):  
Model Test ◽  
Design Method ◽  
Local Stress ◽  
Fatigue Loading ◽  
Test Method ◽  
Simplified Model ◽  
Alloy 617 ◽  
Primary Stress ◽  
Creep Fatigue ◽  
The Impact

Abstract The Simplified Model Test (SMT) is an alternative approach to determine cyclic life at elevated temperature and avoids parsing the damage into creep and fatigue components. The original SMT concept [1] considered that the effects of sustained primary stress loading could be safely neglected because the allowable local stress and strain levels were much higher than the allowable sustained primary stress levels. This key assumption is critically evaluated on Alloy 617 using internal pressurized cylindrical SMT specimens at 950 °C. The impact of combined internal pressurization and displacement-controlled creep-fatigue loading on the SMT cycle life is demonstrated at different strain ranges. The effect of primary load on the SMT design method is discussed.

scholarly journals Evaluation of Primary-Load Effects on Creep-Fatigue Life of Alloy 617 Using Simplified Model Test Method

2021 ◽  
Author(s):  
Yanli Wang ◽  
Peijun Hou ◽  
Robert I. Jetter ◽  
T.-L. Sham
Keyword(s):  
Fatigue Life ◽  
Internal Pressure ◽  
Model Test ◽  
Test Method ◽  
Simplified Model ◽  
Evaluation Procedure ◽  
Alloy 617 ◽  
Creep Fatigue ◽  
Fatigue Evaluation ◽  
Primary Load

Abstract Current creep-fatigue evaluation approaches based on the creep-fatigue Damage-diagram are complex and very conservative. Simplified Model Test (SMT) method is an alternative approach to determine cyclic life at elevated temperatures. The SMT-based creep-fatigue evaluation methodology avoids parsing the damage into creep and fatigue components and greatly simplifies the evaluation procedure for elevated-temperature cyclic service. In this study, the effects of sustained primary-stress loading are evaluated in support of the development of SMT-based creep-fatigue design curves for Alloy 617. Experiments were designed and performed using internal pressurized tubular specimens at 950 °C on Alloy 617. The sustained primary-load was introduced by the internal pressure. A newly developed SMT technique, single-bar SMT, was extended to these tests and SMT creep-fatigue test data were generated with various elastic follow-ups, internal pressures and strain ranges. The test results from this study along with the original SMT data on Alloy 617 demonstrate that, although internal pressure is within the allowable stress limit per ASME Section III Division 5 Code Case N-898, the SMT creep-fatigue cycles to failure were reduced for the cases tested with primary-pressure load. The reduction of SMT creep-fatigue life due to primary-load was found to be dependent on strain ranges and elastic follow up. Approaches to handle the primary-load effect on SMT design curves are discussed.

Pressurized Creep-Fatigue Testing of Alloy 617 Using Simplified Model Test Method

2017 ◽  
Author(s):  
Yanli Wang ◽  
Robert I. Jetter ◽  
T.-L. Sham
Keyword(s):  
Elevated Temperature ◽  
Hysteresis Loop ◽  
Fatigue Damage ◽  
Model Test ◽  
Test Method ◽  
Simplified Model ◽  
Damage Evaluation ◽  
Primary Stress ◽  
Creep Fatigue ◽  
Cyclic Damage

The Simplified Model Test (SMT) is an alternative approach to determine cyclic life at elevated temperature and avoids parsing the damage into creep and fatigue components. The Elastic-Perfectly Plastic (EPP) combined integrated creep-fatigue damage evaluation approach incorporates the SMT data based approach for creep-fatigue damage evaluation into the EPP methodology to avoid the separate evaluation of creep and fatigue damage and to eliminate the requirement for stress classification as in current methods; thus greatly simplifying evaluation of elevated temperature cyclic service. The conceptual basis of the SMT approach is that if the effects of plasticity, creep and strain redistribution in the SMT specimen result in a stress-strain hysteresis loop that envelopes the hysteresis loop at the peak strain location in the component, then the SMT results can be used to assess the cyclic damage in the component. The original SMT concept (Jetter, 1998) considered that the effects of sustained primary stress loading could be safely neglected because the allowable local stress and strain levels were much higher than the allowable sustained primary stress levels. This key assumption requires experimental verification. The influence of the internal pressure on SMT creep-fatigue life is demonstrated and the effect of primary load on the SMT design approach is discussed.

On the Evaluation and Consideration of Fracture Mechanical Notch Support Within a Creep Fatigue Lifetime Assessment

2018 ◽  
Author(s):  
Christian Kontermann ◽  
Henning Almstedt ◽  
Falk Müller ◽  
Matthias Oechsner
Keyword(s):  
Fatigue Loading ◽  
Experimental Program ◽  
Energy Market ◽  
Steam Turbines ◽  
Fatigue Lifetime ◽  
Global Strain ◽  
Creep Fatigue ◽  
Main Components ◽  
Flexible Operation ◽  
The Impact

Changes within the global energy market and a demand for a more flexible operation of gas- and steam-turbines leads to higher utilization of main components and raises the question how to deal with this challenge. One strategy to encounter this is to increase the accuracy of the lifetime assessment by quantifying and reducing conservatisms. At first the impact of considering a fracture mechanical notch support under creep-fatigue loading is studied by discussing the results of an extensive experimental program performed on notched round-bars under global strain control. A proposal how to consider this fracture mechanical notch support within a lifetime assessment is part of the discussion of the second part. Here, a theoretical FEM-based concept is introduced and validated by comparing the theoretical prediction with the results of the previously mentioned experimental study. Finally, the applicability of the developed and validated FEM-based procedure is demonstrated.

scholarly journals Development of Simplified Model Test Methods for Creep-Fatigue Evaluation

2019 ◽  
Author(s):  
Y. Wang ◽  
B. Jetter ◽  
M. C. Messner ◽  
T.-L. Sham
Keyword(s):  
Model Test ◽  
Evaluation Method ◽  
Test Methods ◽  
Simplified Model ◽  
Test Results ◽  
Interaction Diagram ◽  
Creep Fatigue ◽  
Fatigue Evaluation ◽  
Creep Regime ◽  
Further Development

Abstract The Simplified Model Test (SMT) approach is an alternative creep-fatigue evaluation method that no longer requires the use of the damage interaction diagram, or D-diagram. The reason is that the combined effects of creep and fatigue are accounted for in the test data by means of a SMT specimen that is designed to replicate or bound the stress and strain redistribution that occurs in actual components when loaded in the creep regime. However, creep-fatigue experiments on SMT key feature articles are specialized and difficult to perform by the general research community. In this paper, two innovative SMT based creep-fatigue experimental methods are developed and implemented. These newly-developed SMT test methods have resolved all the critical challenges in the SMT key feature article testing and enable the potential of further development of the SMT based creep-fatigue evaluation method into a standard testing method. Scoping test results on Alloy 617 and SS 316H using the newly developed SMT methods are summarized and discussed. The concepts of the SMT methodology for creep-fatigue evaluation are explained.

Acceleration of Grain Boundary Cracking in Ni-Base Alloy 617 Under Creep-Fatigue Loading at 800°C

2020 ◽  
Author(s):  
Kenta Ishihara ◽  
Yifan Luo ◽  
Hideo Miura
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Power Plants ◽  
Base Alloy ◽  
Thermal Power ◽  
Fatigue Loading ◽  
Intergranular Cracking ◽  
Alloy 617 ◽  
Effective Lifetime ◽  
Creep Fatigue

Abstract In recent years, in order to solve the global warming issue, the operating temperature of advanced thermal power plants has attempted to improve thermal efficiency and reduce CO2 emissions. Under the creep and creep-fatigue conditions at elevated temperature, however, the effective lifetime of heat-resistant alloys such as Ni-base Alloy 617, which has high strength and good corrosion resistance at about 750°C, was found to decrease drastically. Main reason for this short lifetime was attributed to the change in the crack initiation and propagation paths from transgranular one to intergranular one. Therefore, it is important to understand and express the criteria for grain boundary cracking. In this study, electron back-scatter diffraction (EBSD) analysis was applied to the visualization of the degradation process of the quality of grain boundaries in the alloy. The change in the crystallinity of grains and grain boundaries were continuously monitored during creep and creep-fatigue tests. It was found that accumulation of vacancies and dislocations degraded the crystallinity of grain boundaries and thus, their strength. The accumulation occurred around the specific grain boundaries which consisted of grains with large difference of Schmid factor during creep test. On the other hand, it occurred around all grain boundaries under the creep-fatigue loading. Thus, the accumulation of defects was clearly accelerated under the creep-fatigue loading. The critical image quality (IQ) value of intergranular cracking was almost the same regardless of the loading mode. Once the IQ value of the damaged grain boundaries decreased to a critical value, intergranular cracking started to occur at the grain boundaries.

Change of the Effective Strength of Grain Boundaries in Alloy 617 Under Creep-Fatigue Loadings at 800°C

2019 ◽  
Author(s):  
Wataru Suzuki ◽  
Kenta Ishihara ◽  
Ryo Kikuchi ◽  
Ken Suzuki ◽  
Hideo Miura
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Evaluation Method ◽  
Accumulation Rate ◽  
Ion Beam ◽  
Fatigue Loading ◽  
Test System ◽  
Total Density ◽  
Alloy 617 ◽  
Creep Fatigue

Abstract In this study, both EBSD (Electron Back-Scatter Diffraction) analysis and a micro tensile test system with FIB (Focused Ion Beam) equipment were applied to bicrystal specimens of Alloy 617 in order to establish a quantitative theory of the lifetime evaluation method under creep-fatigue loadings. The IQ (Image Quality) value which is obtained from the diffraction pattern (Kikuchi pattern) indicates the total density of defects such as vacancies, dislocations, and local strain was used for quantitatively evaluating the crystallinity of the alloy. KAM (Kernel Average Misorientation) value was also used for density analysis of GN (Generally Necessary) dislocations. Continuous changes of microtexture of grains and grain boundaries were observed by applying an intermittent creep fatigue test. As a result, it was confirmed that the IQ value around specific grain boundaries in damaged specimen was drastically degraded compared to that of the initial specimen. Intergranular cracks always occurred when the IQ value decreased to a certain value. Therefore, there is a correlation between the IQ value and the strength of a grain boundary in this alloy. The decrease of the IQ value was attributed to the accumulation of both dislocations and vacancies around the specific grain boundaries under creep loading. The accumulation rate under the creep-fatigue loading was clearly higher than that under simple fatigue and creep loadings. Finally, it was clarified that the degradation of the crystallinity in the vicinity of a grain boundary was a criterion of an intergranular crack under creep-fatigue loadings.

scholarly journals Perancangan dan Pembuatan Game “Pembelajaran Bahasa Jepang Untuk Pemula” Metode User Centered Design Berbasis Android

2017 ◽  
Vol 2 (2) ◽  
pp. 137
Author(s):  
Michael Agustav ◽  
Kathryn Widhiyanti ◽  
Edwin Meinardi Trianto
Keyword(s):  
Design Method ◽  
Usability Testing ◽  
Test Method ◽  
Japanese Language ◽  
User Centered Design ◽  
Dynamic Design ◽  
Adobe Flash ◽  
Asian Pacific ◽  
The Impact ◽  
User Centered

With the growing rate of Asian Pacific free trading business in Indonesia, Indonesians need to be multilingual, rather than communicating only with mother language. Since recently there are quite number of investors come from Japan to Indonesia, Japanese language is fairly important to learn nowadays. And therefore this application is made to aid the process of learning Japanese for beginner by using the user centered design method. In this method the process includes making three prototypes. The first is called hand sketches prototype, then the second is the realization from the result of the first prototype, the third is called dynamic design prototype. These three prototypes are also combined with evaluation towards the user and debugging. There are two testing done, using the usability testing method which one of them includes “completing a transaction” and “evaluating the impact of subtle changes”. The result of the tests have been analyzed and according to the result it can be concluded that the test on completing a transaction shows that 92,3% of the users understood the features and buttons provided in the application, and as for the another test method which is “evaluating the impact of subtle changes” shows that 100% of the users are able to learn Japanese language with this application.Keywords: Android, Bahasa Jepang, User Centered Design, Usability Testing, Starling, Action Script 3, Adobe Flash Builder. AbstrakSeiring perkembangan jaman dimana perdagangan bebas Asia Pasifik mulai sering terjadi, maka penduduk Indonesia perlu mempelajari bahasa lain selain bahasa Indonesia. Bahasa Jepang perlu dipelajari karena mulai banyak investor asing dari negara Jepang di Indonesia. Oleh sebab itu dibuat aplikasi sederhana untuk membantu proses pembelajaran bahasa Jepang untuk pemula menggunakan metode user centered design. Dalam metode user centered design pada pembuatan aplikasi pembelajaran aplikasi pembelajaran bahasa Jepang untuk pemula ini dilakukan dengan membuat prototype pertama berupa hand-sketches prototype, kemudia dibuat  kedua berupa realisasi dari hasil hand-sketches, dan yang terakhir dibuat prototype ketiga berupa dynamic design prototype. Dari ketiga jenis prototype juga dilengkapi dengan evaluasi terhadap pengguna dan dilakukan perbaikan. Kemudian untuk pengujian telah dilakukan dua kali pengujian menggunakan metode dari usability testing yaitu completing a transaction dan evaluating the impact of subtle changes. Hasil dari kedua pengujian itu telah dianalisa dan dihitung, berdasarkan hasil analisa tersebut disimpulkan bahwa pada pengujian completing a transaction mendapatkan hasil 92,3% menunjukkan bahwa pengguna telah memahami fitur dan fungsi dari tombol yang telah disediakan pada aplikasi pembelajaran bahasa Jepang yang telah dibuat dan pada hasil pengujian evaluating the impact of subtle changes mendapatkan hasil 100% hasil tersebut menunjukkan bahwa pengguna telah dapat mempelajari bahasa Jepang dengan menggunakan aplikasi pembelajaran bahasa Jepang yang dibuat. Kata kunci: Android, Bahasa Jepang, User Centered Design, Usability Testing, Starling, Action Script 3, Adobe Flash Builder

scholarly journals Evaluation of Creep-Fatigue Damage Based on Simplified Model Test Approach

2013 ◽  
Author(s):  
Yanli Wang ◽  
Tianlei Li ◽  
T.-L. (Sam) Sham ◽  
Robert I. Jetter
Keyword(s):  
Fatigue Damage ◽  
High Temperatures ◽  
Test Data ◽  
Model Test ◽  
Hold Time ◽  
Simplified Model ◽  
Creep Fatigue ◽  
Asme Code ◽  
Cyclic Damage ◽  
Very High

Current methods used in the ASME Code, Subsection NH for the evaluation of creep-fatigue damage are based on the separation of elevated temperature cyclic damage into two parts, creep damage and fatigue damage. This presents difficulties in both evaluation of test data and determination of cyclic damage in design. To avoid these difficulties, an alternative approach was identified, called the Simplified Model Test or SMT approach based on the use of creep-fatigue hold time test data from test specimens with elastic follow-up conservatively designed to bound the response of general structural components of interest. A key feature of the methodology is the use of the results of elastic analysis directly in design evaluation similar to current methods in the ASME Code, Subsection NB. Although originally developed for current material included in Subsection NH, recent interest in the application of Alloy 617 for components operating at very high temperatures has caused renewed interest in the SMT approach because it provides an alternative to the proposed restriction on the use of current Subsection NH simplified methods at very high temperatures. A comprehensive review and assessment of five representative simplified methods for creep-fatigue damage evaluation is presented in Asayama [1]. In this review the SMT methodology was identified as the best long term approach but the need for test data precluded its near term implementation. Asayama and Jetter [2] is a summary of the more comprehensive report by Asayama [1] with a summary of the SMT approach presented by Jetter [3]. In this paper, the previously documented development of the SMT approach and applicable restrictions are discussed and reviewed; the design of the SMT specimen, measurement issues and constraints are presented; the test apparatus and measurement system is described; initial test results and their application to a prototypic design curve are presented; and further testing and analysis for ASME Code incorporation are discussed.

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