Gonzalez-Ojeda, Roberto

Preferred name

Official Name

Gonzalez Ojeda, Roberto

Alternative Name

robglez

González-Ojeda, R.

Main Affiliation

ORCID

0000-0003-2319-1631

Scopus Author ID

56314856300

Researcher ID

DTL-2716-2022

Now showing 1 - 10 of 37

Some of the metrics are blocked by your
consent settings
Ultrafine-grain Steels: Mechanical Behavior
(2016)
Quintana Hernández, María José
;
;
MARÍA JOSÉ QUINTANA HERNÁNDEZ;576914
In recent years, both the steelmaking industry and laboratories in different parts of the world, have shown an increasing interest in reaching an industrial-level production of ultrafine grained steels (also known as ultrafine ferrite), which have a grain size d lower than 5 μm, and enhanced mechanical resistance and fracture toughness. At room temperature, the capacity of the material to be deformed during bending or drawing operations (typical of requirements for automotive parts applications) depends on the interaction of a hard and a soft phase in the microstructure. On the other hand, at high temperatures, these steels may show superplastic behavior if deformed at a precise combination of temperature and strain rate.
17
Some of the metrics are blocked by your
consent settings
Superplastic HSLA Steels: Microstructure and Failure
(2013)
Fernández, Sara
;
García García, José Ovidio
;
Verdeja González, Luis Felipe
;
Verdeja González, José Ignacio
;
Quintana, María José
Certain materials can show superplasticity when traction tested at temperatures higher than 50% of their melting point and with low strain rates ( < 10−2 s−1), showing very high elongations (>100%) without localized necking and mainly intergranular fractures. This behavior requires that the starting grain size is small (<10 μm) so the flow of matter can be non-homogeneous (sliding and rotating of the grain boundaries, accommodated by diffusion). This work presents the superplastic characteristic of shipbuilding steel deformed at 800 °C and a strain rate slower than 10−3 s−1. The fine grain size (5 μm) is obtained when using Nb as a microalloying element and manufactured by controlled rolling processes (three stages). After the superplastic deformation, the steel presents mixed fractures: by decohesion of the hard (pearlite and carbides) and ductile (ferrite) phases and by intergranular sliding of ferrite/ferrite and ferrite/pearlite, just as it happens in stage III of the creep behavior. This is confirmed through the Ashby–Verrall model, according to which the dislocation creep (power-law creep) and diffusion creep (linear-viscous creep) occur simultaneously.
Scopus© Citations 4 7 1
Some of the metrics are blocked by your
consent settings
Effect of pressure in the microstructure of die cast Al-8.5Si-3.5cu alloys
(2014)
Barbés Fernández, Miguel Ángel
;
Verdeja González, José Ignacio
;
Quintana, María José
;
Verdeja González, Luis Felipe
;
The microstructure of Pressure Die Casting of an Al-8.5 Si-3.5 Cu alloy used for clean room tiles shows amount of constituents (eutectic and Si phases) that do not correspond to the ones indicated by the phase diagram. Furthermore, there are differences in amount of constituents between the core and the surface zones of parts produced by this process. The work presents quantitative microstructural analysis of this type of industrially produced part, and as a possible cause for these differences, simulations of the effect of pressure on the eutectic (temperature and chemical composition) in the Al-Si system. As the production rate of these parts is very high, and solidification is very fast, microstructural heterogeneity may be related to local entrapment of gasses unable to escape during casting.
43 2
Some of the metrics are blocked by your
consent settings
Mechanical properties of newly developed TiB2 based cermets
(1997)
23 2
Some of the metrics are blocked by your
consent settings
Microscale mechanical properties testing and simulation
(2018)
;
Sánchez-Moreno, José M.
;
Quintana, María José
Characterization of mechanical properties at a micro and nano scale has become increasingly important for manufactured parts, though facilities with accurate and state-of-the-art equipment are scarce, expensive and not always available. For this reason, equipment already in use for traditional characterization can be used to analyze micro and even nano phenomena if calculations and simulations are combined with models representing testing procedures, such as hardness indentation or micro-machining of bending beams. The understanding of the interaction between phases in the material and more accurate finite element models of grains or precipitates with different geometries can contribute in measuring the behavior of very small zones of a manufactured part and design quality control or inspection protocols. © 2018 IEEE.
12 1
Some of the metrics are blocked by your
consent settings
New binder phases for the consolidation of TiB2 hardmetals
(1996)
;
Barandika, M.G.
;
Oña, D.
;
Sánchez, J.M.
;
Villellas, A.
New TiB2-based cermets have been consolidated by hot isostatic pressing of powder mixtures of TiB2 and metallic alloys based on Fe, Ni and Co additions. Relevant thermodynamic aspects of the systems B-Ti-Ni, B-Ti-Fe and B-Ti-Co, essential for avoiding the formation of extremely brittle secondary borides, especially the secondary boride M23B6, are discussed in this work. The role of contaminants like oxygen, carbon and nitrogen, which can also lead to the formation of these compounds is also explained. The hardness, toughness and cutting behaviour of the cermets produced with these new binder phases are comparable with the highest commercial WC-Co grades.
Scopus© Citations 49 38 1
Some of the metrics are blocked by your
consent settings
High temperature mechanical behavior and microstructural evolution of 304 stainless steel
(2010-05)
Quintana Hernández, María José
;
The use of stainless steel at very high temperatures requires a detailed study of stress-strain and microstructure relationships. The tests made with a 304 type stainless steel are presented in order to study tensile properties at both 700 and 850oC, as well as microstructure characteristic such as austenite grain size (predominant phase in this steel), twinning and carbide M23C6 precipitates distribution and size, comparing them also to room temperature data. Though the resistance is reduced in considerable amount, the results indicate that the time the samples are maintained at the test temperature is a critical factor in the stress-strain curve, which is related to the presence of twins and its different concentration at the core or exterior part of the sample, as well as the amount of carbide precipitates at the interior or borders of the austenite crystals.
5 1
Some of the metrics are blocked by your
consent settings
Open surgery while wearing night vision goggles
(2010)
;
Stetz, Melba C.
;
;
Wiederhold, Brenda K.
;
Rodríguez Schlögl, Elizabeth María
Night vision technology is nothing new. In fact, the military rely significantly on this technology during nighttime operations. A surgeon is like a medical soldier in the battlefield. His/her only mission is that of keeping people alive. Due to many technological advances, patients cannot only train on relaxation while visiting their doctors but also get distracted by playing videogames while waiting for them. Furthermore, this virtual reality experience can be enhanced if the patient wears goggles or Head Mounted Displays under dimmed or absence of lights. The purpose of this study was to test if a surgeon could operate when extending into such a dark condition situation, but in the surgical suite. Therefore, a surgeon performed seven open surgeries on rabbits. All surgeries were performed on the thorax and abdomen regions. Specifically, the surgeon was able to perform these surgeries by wearing on his head a micro camera with infrared light and a night vision goggles. The first assistant used this same system while the scrub nurse and the anesthesiologist did not. There were no complications either during or after these procedures. It is possible to make open surgeries wearing a night vision system. Further approaches should be tested with human volunteers. Keywords: Night Vision Goggles, Open Surgery, Cyber-medicine
43 2
Some of the metrics are blocked by your
consent settings
Wear in ultrafine hardmetal mills manufactured by sinter + HIP
(Metal Powder Industries Federation (MPIF), 2006-12-01)
Sánchez-Moreno, José Manuel
;
Ordóñez, Alejandro
;
Ultrafine WC-Co milling tools were wear-tested in finishing machining conditions. Mills manufactured in the laboratory followed the powder metallurgy route for ultrafine grades. Total density in hardmetal grades of 0.2 and 0.4 μm was achieved through the Sinter + HIP technique. Wear in laboratory mills was compared with wear in coarse and ultrafine grade commercial mills. All mills cutting edges suffered wear mainly in the abrasive and chipping form. Chipping was excessive and peculiar in form in the laboratory mills; a slight presence of the fragile η phase was discovered. Laboratory mills showed similar wear to the commercial coarse grades, and much more than that of commercial ultrafine grades. A lack of toughness is suggested due to a small difference in the WC mean grain size, in the Co mean free path (λ) and in its distribution: homogeneous in laboratory mills and heterogeneous in the commercial ones. ©Metal Powder Industries Federation (MPIF)
47 1
Some of the metrics are blocked by your
consent settings
La temperatura de la intercara arrabio/refractario como variable determinante de los mecanismos de corrosión del crisol del horno alto
(1998)
Verdeja González, Luis Felipe
;
Pusek, P., Alfonso
;
Fernández, Ángel Alejandro
;
El desgaste de materiales en el horno alto puede realizarse bajo la consideración de mecanismos estrictamente abrasivos o con el predominio de las componentes químicas y erosivas resultantes de la circulación de fluidos sobre el refractario. No obstante, aunque en determinadas situaciones, la abrasión o las componentes químicas pueden resultar los mecanismos controlantes, es necesario considerar que todos ellos (abrasión, erosión, desgaste químico, adhesión y desgaste térmico-choque térmico) "cooperan" en la degradación del refractario del horno, Para cualquiera de los mecanismos que intervenga en el desgaste de los materiales, resulta conveniente conocer el valor de la temperatura a lo largo de las intercaras del refractario con los sólidos, líquidos o gases presentes en el horno. En la ponencia será desarrollada de forma específica, la importancia que tiene la temperatura en la intercara refractario-arrabio sobre el desgaste de los materiales del crisol. Se discutirán las diferentes hipótesis de transporte (energía, cantidad de movimiento y materia) más adecuadas para la obtención de la temperatura de intercara.
Scopus© Citations 4 8 2

Gonzalez-Ojeda, Roberto

Filters

Settings

Sort By

Results per page