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.

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

2018 ◽  
Vol 140 (12) ◽  
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 lead to higher utilization of main components and raise 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 of how to consider this fracture mechanical notch support within a lifetime assessment is discussed within the second part of the paper. Here, a theoretical finite element method (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 Dynamic Response of Rub Caused by a Shedding Annular Component Happening in a Steam Turbine

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
J. M. Chen ◽  
D. X. Jiang ◽  
N. F. Wang ◽  
S. P. An
Keyword(s):  
Dynamic Response ◽  
Steam Turbine ◽  
Structural Features ◽  
Frequency Domain Analysis ◽  
Steam Turbines ◽  
Contact Constraint ◽  
Fault Features ◽  
Rotor Bearing ◽  
Main Components ◽  
The Impact

Rub caused by a shedding annular component is a severe fault happening in a steam turbine, which could result in a long-term wearing effect on the shaft. The shafting abrasion defects shortened the service life and damaged the unit. To identify the fault in time, the dynamic response of rub caused by a shedding annular component was studied as follows: (I) a rotor-bearing model was established based on the structural features of certain steam turbines; node-to-node contact constraint and penalty method were utilized to analyze the impact and friction; (II) dynamic response of the rotor-bearing system and the shedding component was simulated with the development of rub after the component was dropping; (III) fault features were extracted from the vibration near the bearing position by time-domain and frequency-domain analysis. The results indicate that the shedding annular component would not only rotate pivoting its axis but also revolve around the shaft after a period of time. Under the excitation of the contact force, the peak-peak vibration fluctuates greatly. The frequency spectrum contains two main components, that is, the working rotating frequency and revolving frequency. The same phenomenon was observed from the historical data in the field.

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 Fatigue life assessment of TTC streetcar concrete pavements

2021 ◽  
Author(s):  
Bahram Farhang
Keyword(s):  
Life Cycle ◽  
Service Life ◽  
Fatigue Cracks ◽  
Fatigue Loading ◽  
Life Assessment ◽  
Superior Performance ◽  
Experimental Program ◽  
Impact Fatigue ◽  
Construction Methods ◽  
The Impact

The Toronto Transit Commission, TTC traditional embedded track for mechanically jointed rails, is performing satisfactory except for accelerated surface concrete deterioration. By far the most damaging group of deterioration processes in streetcars concrete pavement is due to wheel impact on the joints which will subsequently excite a response on the track. The enhancement of special trackwork, STW service life was the initiative to explore encapsulation technology advances in embedded track materials and construction methods. This aimed to extend the life cycle of the track from current average of 15 years towards target life of 50 years. In the present study, attempts at finding and patterning the localized cracks, especially wheel impact fatigue cracks, are carried out. This issue was investigated during the course of an experimental program demonstrated by simulating the wheel impact loading in concrete under repeated load application. Specially designed specimens were used to represent sheet rubber and urethane encapsulation system proposal against the current assembly. This research reviews the pros and cons of various factors influencing the life cycle of the current assembly and examining and assessing between alternative track construction methods and materials at the joints and examining the concrete's performance both during the impact fatigue loading resulting in inclined cracking and ongoing service life and durability issues under combined environmental and mechanical loadings. Experimental results show that it is possible to achieve the targeted service life of 50 years, based on minimum of 10 time superior performance for either of the proposed encapsulation technologies vs. current construction methods.

Considerations to the An-Isothermal Creep-Fatigue Assessment of Steam Turbine Rotor Steels

2007 ◽  
Author(s):  
Martin Reigl ◽  
Harish N. Dave
Keyword(s):  
Steady State ◽  
Creep Damage ◽  
Fatigue Loading ◽  
Turbine Rotor ◽  
Steam Turbines ◽  
Compression Phase ◽  
Warm Start ◽  
Steady State Operation ◽  
Creep Fatigue ◽  
Isothermal Creep

The high creep-fatigue loading of fast starting steam turbines is investigated. Based on real turbine operation, but assuming worse conditions like increased notch factors, typical stress-strain cycles of the rotor are calculated. These an-isothermal cycles consists of phases of different start-types (cold start, warm start and hot start), of steady-state operation, shut-down and stand-still. Experiments, performed with these cycles, are evaluated with different methods. For the LCF fraction of the lifetime consumption, several reference temperatures are compared, whereby the so-called ‘corner temperature’ is preferably incorporated, which is the temperature at the end of the compression phase. The creep fraction of the lifetime consumption is firstly assessed with the time fraction rule, either considering the midlife cycles only or considering each individual cycle, either considering all phases of the cycles or the steady state operation phase only. Then, the ductility exhaustion method for the creep damage is applied, after defining the ductility for several experiments.

scholarly journals Fatigue life assessment of TTC streetcar concrete pavements

2021 ◽  
Author(s):  
Bahram Farhang
Keyword(s):  
Life Cycle ◽  
Service Life ◽  
Fatigue Cracks ◽  
Fatigue Loading ◽  
Life Assessment ◽  
Superior Performance ◽  
Experimental Program ◽  
Impact Fatigue ◽  
Construction Methods ◽  
The Impact

The Toronto Transit Commission, TTC traditional embedded track for mechanically jointed rails, is performing satisfactory except for accelerated surface concrete deterioration. By far the most damaging group of deterioration processes in streetcars concrete pavement is due to wheel impact on the joints which will subsequently excite a response on the track. The enhancement of special trackwork, STW service life was the initiative to explore encapsulation technology advances in embedded track materials and construction methods. This aimed to extend the life cycle of the track from current average of 15 years towards target life of 50 years. In the present study, attempts at finding and patterning the localized cracks, especially wheel impact fatigue cracks, are carried out. This issue was investigated during the course of an experimental program demonstrated by simulating the wheel impact loading in concrete under repeated load application. Specially designed specimens were used to represent sheet rubber and urethane encapsulation system proposal against the current assembly. This research reviews the pros and cons of various factors influencing the life cycle of the current assembly and examining and assessing between alternative track construction methods and materials at the joints and examining the concrete's performance both during the impact fatigue loading resulting in inclined cracking and ongoing service life and durability issues under combined environmental and mechanical loadings. Experimental results show that it is possible to achieve the targeted service life of 50 years, based on minimum of 10 time superior performance for either of the proposed encapsulation technologies vs. current construction methods.

MODERN PROBLEMS OF ACCOUNTING AND ANALYTICAL ENSURING FINANCIAL RESULTS MANAGEMENT

2020 ◽  
Author(s):  
Yuliia Peniak ◽  
◽  
Nataliia Horokhovatska ◽  
Keyword(s):  
Performance Management ◽  
Enterprise Management ◽  
Goods And Services ◽  
Financial Condition ◽  
General Evaluation ◽  
Net Profit ◽  
Business Entities ◽  
Results Management ◽  
Main Components ◽  
The Impact

The main purpose of any enterprise in the market economy is to obtain high financial results. One of the main conditions for the effective functioning of the enterprise is ability to generate profit in the amount that will create the financial basis for further development and expansion of the enterprise, comply with social and material needs, ensure competitiveness in the market of goods and services. The need for accounting and analytical management of financial results stems from needs of owners, the state and employees in information that will enable them to identify patterns and trends in financial results, identify and assess the main factors influencing the process of their creation, distribution and usage, identify reserves and thus increase the level of profitability. Despite the significant scientific contribution in the field of research of financial results of the enterprises, the issue of improvement aims to the accounting and analytical maintenance of management of financial results of the enterprise remains actual. That is why the purpose of the study is to substantiate the theoretical and practical aspects and develop approaches to improving the mechanism of formation of accounting and analytical support for the management of financial results of the enterprise. Accounting and analytical management of financial results of the enterprise is a set of interconnected elements of production and management system, activities carried out by the subject of management, creation of a certain structure, as well as collection, accumulation, storage and analysis of information necessary for effective operation of the enterprise. The main components of the study of accounting and analytical support of financial performance management are the formation of methods of analysis, control and forecasting of financial results, which requires specification of the components of the analytical and controlled process within the organizational and information model. Namely, the formation of reliable information about the financial condition of the enterprise, the analysis of economic indicators of the enterprise is of great importance in the system of general evaluation of business entities. Their research makes it possible to assess the dynamics of the structure of income and expenses, to determine the impact of factors on the company's profit from various activities, as well as to find reserves to increase the net profit of enterprises. Thus, the improvement of accounting and analytical support of enterprise management is based on the use of modern forms, methods and principles that place new demands on the formation of unbiased, complete, timely, clear and useful accounting and analytical information about the enterprise and its financial results.

TEACH-POT: Provide Opportunities in Teaching

2020 ◽  
pp. 79-91 ◽  
Author(s):  
Maria Giulia Ballatore ◽  
Ettore Felisatti ◽  
Laura Montanaro ◽  
Anita Tabacco
Keyword(s):  
Academic Community ◽  
Real Effect ◽  
The Real ◽  
Main Components ◽  
The Impact ◽  
Training Opportunities ◽  
Different Levels

This paper is aimed to describe and critically analyze the so-called "TEACHPOT" experience (POT: Provide Opportunities in Teaching) performed during the last few years at Politecnico di Torino. Due to career criteria, the effort and the time lecturers spend in teaching have currently undergone a significant reduction in quantity. In order to support and meet each lecturers' expectations towards an improvement in their ability to teach, a mix of training opportunities has been provided. This consists of an extremely wide variety of experiences, tools, relationships, from which everyone can feel inspired to increase the effectiveness of their teaching and the participation of their students. The provided activities are designed around three main components: methodological training, teaching technologies, methodological experiences. A discussion on the findings is included and presented basing on the data collected through a survey. The impact of the overall experience can be evaluated on two different levels: the real effect on redesigning lessons, and the discussion on the matter within the entire academic community.

FORMATION OF HUMAN CAPITAL IN THE DIGITAL TRANSFORMATION PARADIGM

2020 ◽  
Vol 2 (5) ◽  
pp. 115-119
Author(s):  
M. V. SAVINA ◽  
◽  
A. A. STEPANOV ◽  
I.A. STEPANOV ◽  
◽  
...  
Keyword(s):  
Human Capital ◽  
Digital Age ◽  
Digital Transformation ◽  
Educational Process ◽  
Knowledge And Skills ◽  
Main Components ◽  
The Impact ◽  
Modern Era

The article highlights the problems of the impact of "digitalization" of society on the formation and transformation of human capital, and above all, the development of new competencies, knowledge and skills. The main components of human capital in the modern era, the features of the formal and informal educational process are clarified and disclosed. The necessity of minimizing the precariat class is proved. The main directions of qualitative improvement of human capital adequate to the challenges of the digital age and globalization are defined.

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