Thermal Fatigue Evaluation

2009 ◽  
pp. 163-163-26 ◽  
Author(s):  
AE Carden
Keyword(s):  
Thermal Fatigue ◽  
Fatigue Evaluation

Investigation of Thermal Fatigue Characteristics of Charging Line of RCV in PWR

2017 ◽  
Author(s):  
Naeem Ahmad ◽  
XiangBin Li ◽  
Iftikhar Ahmad ◽  
Nan Li ◽  
Shahroze Ahmed ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Thermal Fatigue ◽  
Nuclear Power ◽  
Thermal Loading ◽  
Structural Model ◽  
Fatigue Cracks ◽  
Volume Control ◽  
Piping System ◽  
Thermal Transients ◽  
Fatigue Evaluation

Nuclear Power Plant (NPP) components need to tolerate thermal constraints, internal pressure and thermal transients. These thermal transients being repeated again and again can lead to thermal fatigue of the component. It has significant effect on the degradation of the NPP components in long term. Studies of thermal fatigue on different NPP components such as mixing tees and valves have been carried out before but the charging line in the chemical and volume control system (RCV) of the NPP seems to have been ignored for thermal fatigue analysis. Charging Line is the connection from RCV towards Reactor Coolant System (RCP). To enhance the safety of the charging line, thermal fatigue evaluation of piping system was performed using the Fluid Structure Interaction (FSI) analysis. Temperature distributions in the pipes were determined via thermal hydraulic analysis (CFX) and the results were applied to the structural model of the piping system to determine the thermal stress (Transient Structural). Results revealed the location of fatigue cracks. Types of stress were identified that caused the fatigue damage. The CFD analysis enabled us to clarify the role of turbulence with respect to the thermal loading of the structure. The study will provide valuable information for establishing a permanent methodology to help minimize thermal fatigue damage in NPP components.

Thermal Fatigue Evaluation Method of Pipes by Equivalent Stress Amplitude

2012 ◽  
Author(s):  
Takafumi Suzuki ◽  
Naoto Kasahara
Keyword(s):  
Fatigue Damage ◽  
Thermal Fatigue ◽  
Evaluation Method ◽  
Stress Amplitude ◽  
Equivalent Stress ◽  
Safety Margin ◽  
Evaluation Procedure ◽  
Fatigue Evaluation ◽  
High Cycle Thermal Fatigue ◽  
Equivalent Stress Amplitude

In recent years, reports have increased which are about failure cases caused by high cycle thermal fatigue both at light water reactors and fast breeder reactors. One of the biggest reasons of the cases is a turbulent mixing at a Tee-junction, where hot and cold temperature fluids are mixed, in a coolant system. In order to prevent thermal fatigue failures at Tee-junctions, The Japan Society of Mechanical Engineers (JSME) published the guideline S017-2003 (or JSME guideline) which is an evaluation method of high cycle thermal fatigue damage at a nuclear piping. It has some limitations in terms of its inconstant safety margin and its complexity in evaluation procedure, however. In order to solve these limitations, this paper proposes a new evaluation method of thermal fatigue damage with use of the “equivalent stress amplitude” which represents random temperature fluctuation effects on thermal fatigue damage. Because this new method makes methodology of evaluation clear and concise, it will contribute to improving the guideline for thermal fatigue evaluation.

Thermal Fatigue Evaluation Model of a Microelectronic Chip in Terms of Interfacial Singularity

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Xiaoguang Huang ◽  
Zhiqiang Wang
Keyword(s):  
Thermal Fatigue ◽  
Evaluation Method ◽  
Evaluation Model ◽  
Thermomechanical Properties ◽  
Fatigue Tests ◽  
Strain Intensity ◽  
Intensity Factors ◽  
Singular Stress ◽  
Stress Strain ◽  
Fatigue Evaluation

Abstract Thermal fatigue failure of microelectronic chip often initiates from the interface between solder and substrate, and the service life of the chip is largely dependent on the singular stress–strain at this interface. To provide a reasonable life evaluation method, three thermal fatigue evaluation models, including strain-based and stress–strain based, have been established in terms of the interfacial singular fields. Thermal fatigue lives of different chips under different thermal cycles are obtained by thermal fatigue tests, and the stress and strain intensity factors and singular orders at the solder/substrate interface are computed at the same conditions, to determine the material constants in the established models. The thermal fatigue lives predicted are in acceptable agreement with the experimental results. What is more, the application of these thermal fatigue models demonstrates a fact that the thermal fatigue of the microelectronic chips can be evaluated uniformly no matter what the shapes, dimensions of the chip, and the thermomechanical properties of the solders are, as long as the relevant stress–strain intensity factors and singular orders are obtained.

scholarly journals Hydro-Thermal Fatigue of Polymer Matrix Composite Biomaterials

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3650 ◽  
Author(s):  
Daniel Pieniak ◽  
Krzysztof Przystupa ◽  
Agata Walczak ◽  
Agata M. Niewczas ◽  
Aneta Krzyzak ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Flexural Strength ◽  
Thermal Fatigue ◽  
Bending Strength ◽  
Artificial Saliva ◽  
Filler Particle ◽  
Ceramic Composites ◽  
Inorganic Particles ◽  
Dental Restorations ◽  
Fatigue Evaluation

This study discusses a quantitative fatigue evaluation of polymer–ceramic composites for dental restorations, i.e., commercial (Filtek Z550) and experimental Ex-nano (G), Ex-flow (G). Their evaluation is based on the following descriptors: mechanical strength, elastic modulus and strain work to fracture. Supposed to reflect factors of environmental degradation conditions, thermal fatigue was simulated with a special computer-controlled device performing algorithms of thermocycling. The specimens intended for the strength test underwent 104 hydro-thermal fatigue cycles. This procedure of thermocycling was preceded by aging, which meant immersing the specimens in artificial saliva at 37 °C for 30 days. The strength tests after aging only and after aging and thermocycles were performed in line with the three-point flexural strength (TFS) test, specified in ISO 4049, and the biaxial flexural strength (BFS) test, specifically piston-on-three-ball in accordance with ISO 6872. Based on the results, it can be stated that composites with higher volume content of inorganic particles after aging only show higher strength than materials with lower filler particle content. For example, the average flexural bending strength of the Ex-flow (G) composite was about 45% lower than the value obtained for the Ex-nano (G) material. The residual strength after thermocycles is significantly lower for the experimental composites, whereas a smaller decrease in strength is recorded for the commercial composites. Decreases in strength were about 4% (Filtek Z550), 43% (Ex-nano (G)), and 29% (Ex-flow (G)) for the BFS test; and about 17% (Filtek Z550), 55% (Ex-nano (G)), 60% (Ex-flow (G)) for the TFS test. The elastic modulus of the experimental composites after only aging is higher (about 42%) than that of the commercial composite, but the elastic modulus of the commercial composite increases significantly after thermocycling. A descriptor known as strain work to fracture turns out to be a good descriptor for evaluating the hydro-thermal fatigue of the tested polymer–ceramic composites.

Thermal Fatigue Evaluation Based on the Methods for Structural Stress Determination According to EN 13445-3 Annex NA: Comparison With Other Codes

2018 ◽  
Author(s):  
Ralf Trieglaff ◽  
Martin Beckert ◽  
Jürgen Rudolph ◽  
Daniel Friers
Keyword(s):  
Finite Element ◽  
Thermal Fatigue ◽  
Pressure Vessel ◽  
Structural Stress ◽  
Stress Determination ◽  
User Friendliness ◽  
Shell Elements ◽  
European Working ◽  
Detailed Assessment ◽  
Fatigue Evaluation

The European Pressure Vessel Standard EN 13445 provides in its part 3 (Design) a simplified method (Clause 17) and a detailed method for fatigue assessment (Clause 18) of unwelded and welded components. Clause 18 “Detailed Assessment of Fatigue Life” is under principal revision within the framework of the European working group “CEN/TC 54/WG 53 – Design methods” in order to reach a significant increase in user-friendliness and a clear guideline for the application. This paper is focused on the new recommendations for the thermal fatigue evaluation given in the new informative annex NA “Instructions for structural stress oriented finite element analyses using brick and shell elements”. In this annex NA different application methods for the determination of structural stresses are explained in connection with the requirements for finite element models and analyses. This paper will give a short overview of the proposed approaches of structural stress determination in the new draft annex NA of the revised EN 13445-3 with special recommendations for thermal fatigue evaluation application. This constitutes an extension of the usual and established application of the structural stress approach for welds subjected to mechanical loading conditions. It will present the current state of the approaches based on the results of fatigue analyses according to EN 13445-3 Clause 18 for two different application examples. For validation purposes, these different approaches are compared with the results of Clause 17 of the EN 13445 and other pressure vessel design codes.

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