Gonzalez-Ojeda, Roberto
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Preferred name
Gonzalez-Ojeda, Roberto
Official Name
Gonzalez Ojeda, Roberto
Alternative Name
robglez
González-Ojeda, R.
Main Affiliation
ORCID
Scopus Author ID
56314856300
Researcher ID
DTL-2716-2022

Research Output
Now showing 1 - 10 of 36
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Microstructural changes of a construction steel caused by hot deformation

2013 , Verdeja González, José Ignacio , Quintana, María José , Gonzalez-Ojeda, Roberto , Verdeja González, Luis Felipe

A construction steel (shipbuilding strip) obtained by Advanced Thermomechanical Controlled Rolling Processes presents a room temperature banded ferrite-pearlite microstructure, and when superplastically deformed at 800°C with a strain rate of 5.85x10-5 s-1, the bands disappear as there is grain boundary sliding and grain cluster rotation. Nevertheless, the superplastic deformation does not imply a decrease in mechanical properties, as room temperature tests with strain rates of 1.46x10-3 s -1 with the steel previously deformed in superplastic conditions (until a 110% of straining) result in similar mechanical data. If the steel is deformed at 750°C with low strain rates, cooling results in a microstructure formed only by ferrite and carbides (the pearlitic phase disappears). This behavior may be explained, from a thermodynamical point of view, by the effect of negative hydrostatic pressure during the tensile test and the pronounced ferrite- and carbide-former capacity of Ti and Nb microalloying elements. The samples, tensile tested, in both the hot rolled raw state and superplastically deformed and then room temperature tested, show in the fracture surface SEM analysis almost identical features: decohesions surrounding MnS and (C,N)(Ti,Nb) precipitates and between ferrite and pearlite grains, as well as bedding.

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Open surgery while wearing night vision goggles

2010 , Mosso Vázquez, José Luis , Stetz, Melba C. , Gonzalez-Ojeda, Roberto , Wiederhold, Brenda K. , Arrellín Rosas, Gerardo , Rodríguez Schlögl, Elizabeth María , Mosso Lara, Dejanira

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

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Mechanical properties of newly developed TiB2 based cermets

1997 , Gonzalez-Ojeda, Roberto

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Sintering + HIP of Ultrafine WC-Co Hardmetals

2007 , Ordóñez, Alejandro , Gonzalez-Ojeda, Roberto , Sánchez, J.M.

Abstract not available.

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Cooling efficiency in furnace design

2013-12 , Gonzalez-Ojeda, Roberto , Quintana Hernández, María José , Ruiz Bustinza, Iñigo , García Carcedo, Fernando , Barbés, Miguel Ángel , Florentina Barbés, María

During melting, reduction or thermal treatment of a steel charge, the input of energy (either chemical or electrical) is indispensable to guarantee the viability of the process. Under these circumstances, it will be reasonable to design the furnace lining in such a way that heat loss through the walls is minimized. Nevertheless, it can be proved that, for some situations, it is more efficient to withdraw as much heat as possible from the walls than trying to thermally isolate the system. The work presents recommendations for the design of walls and cooling systems in furnaces obtained by quantitative analysis of temperatures reached in specific locations of the furnace using the nodal wear model. The analysis indicates that the wear process of the lining may be controlled if all the elements that intervene in the process are known.

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Wear in ultrafine hardmetal mills manufactured by sinter + HIP

2006-12-01 , Ordóñez, Alejandro , Gonzalez-Ojeda, Roberto , Sánchez-Moreno, José Manuel

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)

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Dmaic of structural steel parts through FEM and DOE

2016 , Gonzalez-Ojeda, Roberto , Quintana, María José , Verdeja, Luis Felipe

DMAIC in the automotive sector is applied to the design and manufacturing processes of structural steel parts in order to assess variability in mechanical properties of the raw materials, use of different types of steel in the same part, modifications in thickness of the steel sheet and even changes in geometry to produce lighter and stronger parts. The work presents an example of three stamped automotive structural components, mechanically interacting together when deformed under load. Minitab design of experiments module was used to evaluate two level factors, one of them being the thickness of each part, and the other the material properties: DP600, DP780 steel or a boron-based steel alloy. A FEM model of the three parts, with structural supports and loads, was performed to evaluate displacement of the system, max. equivalent stress, strain and total weight, allowing data correlation to determine best practices to accomplish low weight, high stiffness designs. Copyright © 2016 MS&T16®.

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Dual-phase ultrafine grained steels produced by controlled rolling processes

2011 , Quintana, María José , Gonzalez-Ojeda, Roberto , Verdeja González, Luis Felipe , Verdeja González, José Ignacio

Double-phase steels are an excellent alternative in the production of automotive parts that require high mechanical resistance, high impact strength and elevated elongation. These materials are produced using low-alloy steels as a basis, reducing costs and resulting in a combination of martensite and ferrite structures with ultrafine grain sizes. These characteristics are accomplished through a strict control of rolling conditions: strain rate, cooling rate and direct quenching. This work presents the results of tension testing of two types of double phased steels, along with microstructural characterization, in order to understand the effect of the advanced thermomechanical controlled rolling processes on the formation of the microstructure and the resulting mechanical properties.

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Mechanical development, production and testing of a miniaturized high fidelity accelerometer for a Cubesat

2022 , Zarate-Villazon, Ángel M. , Aizpuru-Gutierrez, Lorenzo , Espinosa-Juarez, Erick , Martinez-Quintana, Eduardo , Sanchez-Zavala, Alejandro , Gonzalez-Ojeda, Roberto

There are numerous scientific missions that rely on a high fidelity accelerometer. The application of these devices ranges from fundamental physics and on-orbit thruster characterization, to modeling gravitational and aerodynamic perturbations in orbit. These high fidelity accelerometers have been used across different missions like the Gravity Probe, the LISA Pathfinder and Champ. Moreover, this technology has not yet been successfully miniaturized for its usage within the Cubesat form factor . While the specific scientific application of the accelerometer defines its feasibility for usage in a Cubesat, studies suggest there are possible missions such as atmospheric density characterization in this type of spacecraft. This paper presents the development and validation of the mechanism for a miniaturized high fidelity accelerometer. The high fidelity accelerometer here presented measures the relative displacement of a free flying test mass isolated from external perturbations to which the satellite is subjected to. The most important mechanical advancement from this proposal is a mechanism that constrains the test mass during the launch phase and releases it at the center of the test chamber once it is in orbit. Additionally, a convenient feature is to have the ability to enact this mechanism whenever the test mass needs to be recentered. Moreover, the selection of materials has to comply with the scientific requirements on how good the test mass shall be isolated from external forces while meeting the mass and wear requirements of the mechanism. All of these with a target volume of 1U of the Cubesat. The work presents the design and testing phases of the mechanical device associated with this high fidelity accelerometer. The design phase considers a variety of finite element analysis on different configurations of the mechanism. It also presents a study on the convenience of the materials selected using Ashby materials charts. The production phase identifies the appropriate manufacturing processes for a Cubesat’s scale. The testing campaign consists of functionality testing, a durability analysis of the mechanism and finally a comparative test once the mechanism has been subjected to vibration testing. Additionally, the tests must also determine the need and quality of lubrication on the mechanism as well as define operational requirements to be considered in the operations design of the mission.

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Superplasticity of ultrafine grained low-carbon HSLA steels

2012 , Verdeja González, José Ignacio , Quintana, María José , García García, José Ovidio , Verdeja González, Luis Felipe , Gonzalez-Ojeda, Roberto , Fernández Fernández, Sara

Steels with ultrafine grained structure may present superplastic behavior at specific temperatures and strain rates that allow the grain boundary sliding mechanisms to be activated. The work presents high temperature tension tests in a low carbon, low alloy steel obtained by advanced thermomechanical controlled rolling processes, showing at 800°C elongations as high as 200%. The microstructure of the steel was analyzed in order to identify ferrite and pearlite grain boundaries, and their interaction after the specimens were deformed, showing intergranular decohesions, restored ferrite grains and elimination of banded structure, which are evidence of superplastic mechanisms in this material which is, in fact, ultrafine grained as demonstrated by quantitative metallographic techniques and grain size distribution analysis.

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