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1. Cervellon, Alice. Propriétés en fatigue à grand et très grand nombre de cycles et à haute température des superalliages base nickel monogranulaires : High and Very High Cycle Fatigue of Ni-Based Single Crystal Superalloys at High Temperature.

Degree: Docteur es, Mécanique des solides, des matériaux, des structures et des surfaces, 2018, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique

Les propriétés en fatigue à grand et très grand nombre de cycles des superalliages base Ni monogranulaires ont été étudiées à 1000°C sous trois fréquences (0.5, 70 et 20000 Hz) et quatre rapports de charge (-1, 0.05, 0.3, 0.8), en prenant le CMSX-4 comme alliage de référence.Dans un premier temps, le régime de fatigue à très grand nombre de cycles a été étudié à 20 kHz. A R = -1, la fissure fatale s’amorce à chaque fois depuis un pore de fonderie en interne et se propage suivant les plans cristallographiques {111}, pour des durées de vie entre 106 et 109 cycles, et ce malgré la présence d’autres défauts tels que les eutectiques ou carbures. Le procédé d’élaboration, en impactant directement la taille des pores de fonderie, contrôle la durée de vie alors que la microstructure a peu d’influence. A R = 0.8, le fluage contrôle la durée de vie en fatigue gigacyclique, et rend alors ce régime sensible à la microstructure et à la composition chimique de l’alliage. Les essais à très longues durées de vie (> 109 cycles) ont également été caractérisés et ont permis de proposer un mécanisme d’amorçage dans ce régime de fatigue.Dans un second temps, l’influence de la fréquence d’essai sur les endommagements dépendants du temps tels que l’oxydation et le fluage, et leur interaction, a été étudiée. A R ≤ 0, diminuer la fréquence d’essai revient à inhiber la criticité des défauts internes en favorisant l’endommagement en surface par oxydation. A R ≥ 0.8, le fluage est l’endommagement conduisant à la rupture des éprouvettes quelle que soit la fréquence de sollicitation ou la durée de vie. Les rapports de charge intermédiaires présentent une interaction importante entre les endommagements en oxydation, fatigue et fluage en fonction de la fréquence de sollicitation et des conditions de chargement. A partir de ces observations, un modèle d’endommagement a été proposé afin de prédire la durée de vie du CMSX-4 et présente des résultats satisfaisants par rapport aux données expérimentales.

High and very high cycle fatigue properties of Ni-based single crystal superalloys have been studied at 1000°C using three frequencies (0.5, 70, 20000 Hz), four stress ratios (-1, 0.05, 0.3, 0.8) and CMSX-4 alloy as reference.Firstly, the very high cycle fatigue regime (VHCF) has been studied at 20 kHz. At R = -1, fatal crack always initiates between 106 and 109 cycles from an internal casting pore et then propagates in a crystallographic mode, despite the presence of other metallurgical defects such as eutectics and carbides. The elaboration process controls VHCF life under these conditions as it directly affects casting pore size, whereas microstructure has no relevant influence. At R = 0.8, creep controls VHCF life and makes this regime sensitive to microstructure and alloy’s chemical composition. Long term tests (> 109 cycles) have also been characterized and have enabled to propose a crack initiation mechanism operating in the VHCF regime.Secondly, the influence of frequency on time-dependent damages such as oxidation and creep, and their…

Advisors/Committee Members: Cormier, Jonathan (thesis director), Nadot, Yves (thesis director), Hervier, Zéline (thesis director).

Subjects/Keywords: Superalliage base Ni monogranulaire; Fatigue à grand nombre de cycles; Fatigue gigacyclique; Effet de fréquence; Single crystal superalloy; HCF; VHCF; Frequency effect

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APA (6th Edition):

Cervellon, A. (2018). Propriétés en fatigue à grand et très grand nombre de cycles et à haute température des superalliages base nickel monogranulaires : High and Very High Cycle Fatigue of Ni-Based Single Crystal Superalloys at High Temperature. (Doctoral Dissertation). Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique. Retrieved from http://www.theses.fr/2018ESMA0009

Chicago Manual of Style (16th Edition):

Cervellon, Alice. “Propriétés en fatigue à grand et très grand nombre de cycles et à haute température des superalliages base nickel monogranulaires : High and Very High Cycle Fatigue of Ni-Based Single Crystal Superalloys at High Temperature.” 2018. Doctoral Dissertation, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique. Accessed October 31, 2020. http://www.theses.fr/2018ESMA0009.

MLA Handbook (7th Edition):

Cervellon, Alice. “Propriétés en fatigue à grand et très grand nombre de cycles et à haute température des superalliages base nickel monogranulaires : High and Very High Cycle Fatigue of Ni-Based Single Crystal Superalloys at High Temperature.” 2018. Web. 31 Oct 2020.

Vancouver:

Cervellon A. Propriétés en fatigue à grand et très grand nombre de cycles et à haute température des superalliages base nickel monogranulaires : High and Very High Cycle Fatigue of Ni-Based Single Crystal Superalloys at High Temperature. [Internet] [Doctoral dissertation]. Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique; 2018. [cited 2020 Oct 31]. Available from: http://www.theses.fr/2018ESMA0009.

Council of Science Editors:

Cervellon A. Propriétés en fatigue à grand et très grand nombre de cycles et à haute température des superalliages base nickel monogranulaires : High and Very High Cycle Fatigue of Ni-Based Single Crystal Superalloys at High Temperature. [Doctoral Dissertation]. Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique; 2018. Available from: http://www.theses.fr/2018ESMA0009


Ohio University

2. Lee, Jaewoo. Thermoplastic Composite with Vapor Grown Carbon Fiber.

Degree: PhD, Industrial and Manufacturing Systems Engineering (Engineering), 2005, Ohio University

Vapor grown carbon fiber (VGCF) is a new class of highly graphitic carbon nanofiber and offers advantages of economy and simpler processing over continuous-fiber composites. VGCF used in this work (Pyrograf® III) is grown by means of gas phase catalyst synthesis. The diameter of this fiber ranges from 60 and 200 nanometers and the length varies from 50 to 100 micrometers. There are several issues that must be resolved before VGCF can be a suitable reinforcement. The VGCF must be dispersed in the polymer matrix, a good interface with matrix must be obtained, and the VGCF must be aligned in a specific direction. The object of this study is the extrusion of VGCF/nylon composites. To produce the composite, VGCF and nylon 6 were premixed, and then extruded by twin-screw extruder. An annular converging die was used to produce different volume fractions of VGCF/nylon 6 composite in the form of a continuous strand. SEM analysis and X-ray diffraction results showed that VGCF is well dispersed, wetted, and aligned in the nylon 6 matrix. The tensile strength and modulus for extruded VGCF/nylon 6 composites increased as VGCF volume fraction increased, whereas the ductility decreased. For composite strands subjected to additional extension by drawing, it was seen that both the tensile strength and modulus of composites were increased as draw ratio increased. The theoretical strength prediction performed in this study is a combination of a strength prediction model based on fiber alignment, a model for fiber rotation in the polymer melt, and POLYFLOW simulation, which are sequentially correlated. The theoretical prediction was comparable with experimental results when fiber orientation was evaluated by x-ray diffraction; but the theory overestimated composite strength when fiber rotation was incorporated with the model. Advisors/Committee Members: Alam, M. (Advisor).

Subjects/Keywords: Composite; Vapor Grain Carbon Fiber (VHCF); Thermoplastic Extrusion; Fiber Alignment; Strength Prediction; Nanofiber

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APA (6th Edition):

Lee, J. (2005). Thermoplastic Composite with Vapor Grown Carbon Fiber. (Doctoral Dissertation). Ohio University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1127335929

Chicago Manual of Style (16th Edition):

Lee, Jaewoo. “Thermoplastic Composite with Vapor Grown Carbon Fiber.” 2005. Doctoral Dissertation, Ohio University. Accessed October 31, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1127335929.

MLA Handbook (7th Edition):

Lee, Jaewoo. “Thermoplastic Composite with Vapor Grown Carbon Fiber.” 2005. Web. 31 Oct 2020.

Vancouver:

Lee J. Thermoplastic Composite with Vapor Grown Carbon Fiber. [Internet] [Doctoral dissertation]. Ohio University; 2005. [cited 2020 Oct 31]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1127335929.

Council of Science Editors:

Lee J. Thermoplastic Composite with Vapor Grown Carbon Fiber. [Doctoral Dissertation]. Ohio University; 2005. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1127335929


Karlstad University

3. Pernefur, Emil. Extremvärdesanalys (SEV) av högkvalitativt verktygsstål : Uppskattning av maximal inneslutningsstorlek i pulverstål.

Degree: Science and Technology (starting 2013), 2017, Karlstad University

This work were requested by Uddeholms AB. Uddeholm is the worldś leading manufacturer of high performance tool steel for industrial tools. The company exists worldwide and is present in over 100 countries. One of the company’s main production processes is manufacturing powder steels with extremely high quality. In this work, one of these steels has been analyzed to evaluate the presence and distribution of non-metallic inclusions. Higher demands on quality and more global competition worldwide means that you always have to strive towards perfection in the manufacturing processes. Non-metallic inclusions have severe effects on the mechanical properties of steels. That's why it's of utmost importance to investigate their presence in the tool steel and especially their size. The reason for this is because it's the largest inclusions that's the most dangerous for the material. To obtain a statistically number of certainty of the largest of inclusions, very vast areas of steel have to be examined. Therefore a theoretical method of extrapolation is often used instead to approximate the distribution of the largest inclusions. The precision of this method is still very uncertain. Different methods of this kind of analysis do exist. The method applied in this work of degree is extreme values analysis by statistics of extreme values (SEV). To ensure the pre-conditions of the extreme values analysis, a large quantity of powder steel was analyzed. This was done by light-optic microscopy (LOM) and exclusively performed by Uddeholms AB at their R&D-facility (Research and development-facility) in Hagfors. At Karlstad Universityś test-facility specimens were subjected to ultrasonic fatigue testing at 20 kHz. The specimens derived from the same material as the ones examined in LOM. The result from the ultrasonic fatigue testing were that the largest inclusions in the material were found. This was done by applying very high cycle fatigue (VHCF). To calculate the maximum theoretical inclusion size, SEV was used. The extreme values analysis was performed on gathered data from both LOM and VHCF. All fracture surfaces from the ultrasonic fatigue testing were then examined in scanning electron microscope (SEM) at Karlstad University. In SEM, the largest inclusion in every fractured surface was identified and measured. The maximum real inclusion size from the fractured surfaces was then compared to the maximum theoretically calculated inclusion size from the extreme values analysis. As it turned out the real inclusion size proved to be slightly larger than the theoretical. The difference between them was found to be 3,25 µm. Conclusions drawn were that Uddeholms powder steel exhibits very high purity and that extreme values analysis as an analytical method is recommended. However, the analysis should be repeated to underline the chosen solution methodology.

Subjects/Keywords: Material science; Inclusions; Metallurgy; Tool steel; Powder steel; Extreme values analysis; SEV; Ultrasonic fatigue; VHCF; SS 11 11 16; Light-optical microscope; Scanning electron microscope; Materialteknik; Inneslutningar; Metallurgi; Verktygsstål; Pulverstål; Extremvärdesanalys; Ultraljudsutmattning; SS 11 11 16; Ljusoptiskt mikroskop; Svepelektronmikroskop; Metallurgy and Metallic Materials; Metallurgi och metalliska material

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Pernefur, E. (2017). Extremvärdesanalys (SEV) av högkvalitativt verktygsstål : Uppskattning av maximal inneslutningsstorlek i pulverstål. (Thesis). Karlstad University. Retrieved from http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-63859

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Pernefur, Emil. “Extremvärdesanalys (SEV) av högkvalitativt verktygsstål : Uppskattning av maximal inneslutningsstorlek i pulverstål.” 2017. Thesis, Karlstad University. Accessed October 31, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-63859.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Pernefur, Emil. “Extremvärdesanalys (SEV) av högkvalitativt verktygsstål : Uppskattning av maximal inneslutningsstorlek i pulverstål.” 2017. Web. 31 Oct 2020.

Vancouver:

Pernefur E. Extremvärdesanalys (SEV) av högkvalitativt verktygsstål : Uppskattning av maximal inneslutningsstorlek i pulverstål. [Internet] [Thesis]. Karlstad University; 2017. [cited 2020 Oct 31]. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-63859.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Pernefur E. Extremvärdesanalys (SEV) av högkvalitativt verktygsstål : Uppskattning av maximal inneslutningsstorlek i pulverstål. [Thesis]. Karlstad University; 2017. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-63859

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

.