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RISS 인기검색어
- 검색키워드
- 저자 : Gutierrez-Vargas, Gildardo (검색결과 4 건)
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Gutierrez-Vargas, Gildardo,Ruiz, Alberto,Lopez-Morelos, Victor H.,Kim, Jin-Yeon,Gonzalez-Sanchez, Jorge,Medina-Flores, Ariosto Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.9
One of the consequences of the 475 ℃ embrittlement of duplex stainless steels is the reduction of the resistance to localized corrosion. Therefore, the detection of this type of embrittlement before the material exhibits significant loss in toughness, and corrosion resistance is important to ensure the structural integrity of critical components under corrosion threats. In this research, conductivity measurements are performed using the alternating current potential drop (ACPD) technique with using a portable four-point probe as a nondestructive evaluation (NDE) method for detecting the embrittlement in a 2507 (UNS S32750) super duplex stainless steel (SDSS) aged at 475 ℃ from as-received condition to 300 h. The electric conductivity results were compared against two electrochemical tests namely double loop electrochemical potentiokinetic reactivation (DL-EPR) and critical pitting temperature (CPT). Mechanical tests and the microstructure characterized using scanning electron microscopy (SEM) imaging are conducted to track the progress of embrittlement. It is shown that the electric conductivity correlates with the changes in impact energy, microhardness, and CPT corrosion tests result demonstrating the feasibility of the four-point probe as a possible field-deployable method for evaluating the 475 ℃ embrittlement of 2507 SDSS.
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Evaluation of thermal embrittlement in 2507 super duplex stainless steel using thermoelectric power
Gildardo Gutierrez-Vargas,Alberto Ruiz,김진연,Víctor H. Lopez-Morelos,Ricardo R. Ambriz 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.7
This research investigates the feasibility of using the thermoelectric power to monitor the thermal embrittlement in 2507 super duplex stainless steel (SDSS) exposed to a temperature between 280 °C and 500 °C. It is well known that the precipitation of Cr-rich α′ phase as a result of the spinodal decomposition is the major cause of the embrittlement and the loss of corrosion resistance in this material. The specimens are thermally aged at 475 °C for different holding times. A series of mechanical testing including the tensile test, Vickers microhardness measurement, and Charpy impact test are conducted to determine the property changes with holding time due to the embrittlement. The mechanical strengths and ferrite hardness exhibit very similar trends. Scanning electron microscopy images of impact-fractured surfaces reveal a ductile to brittle transition in the fracture mode as direct evidence of the embrittlement. It is shown that the thermoelectric power is highly sensitive to the thermal embrittlement and has an excellent linear correlation with the ferrite hardness. This paper, therefore, demonstrates that the thermoelectric power is an excellent nondestructive evaluation technique for detecting and evaluating the 475 °C embrittlement of field 2507 SDSS structures.
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Tick-borne rickettsial pathogens in questing ticks, removed from humans and animals in Mexico
Carolina G. Sosa-Gutierrez,Margarita Vargas-Sandoval,Javier Torres,Guadalupe Gordillo-Pérez 대한수의학회 2016 Journal of Veterinary Science Vol.17 No.3
Tick-borne rickettsial diseases (TBRD) are commonly encountered in medical and veterinary clinical settings. The control of these diseases is difficult, requiring disruption of a complex transmission chain involving a vertebrate host and ticks. The geographical distribution of the diseases is related to distribution of the vector, which is an indicator of risk for the population. A total of 1,107 ticks were collected by tick dragging from forests, ecotourism parks and hosts at 101 sites in 22 of the 32 states of Mexico. Collected ticks were placed in 1.5 mL cryovials containing 70% ethanol and were identified to species. Ticks were pooled according to location/host of collection, date of collection, sex, and stage of development. A total of 51 ticks were assayed by polymerase chain reaction (PCR) to confirm species identification using morphological methods. A total of 477 pools of ticks were assayed using PCR techniques for selected tick-borne pathogens. Anaplasma phagocytophilum was the most commonly detected pathogen (45 pools), followed by, Ehrlichia (E.) canis (42), Rickettsia (R.) rickettsii (11), E. chaffeensis (8), and R. amblyommii (1). Rhipicephalus sanguineus was the tick most frequently positive for selected pathogens. Overall, our results indicate that potential tick vectors positive for rickettsial pathogens are distributed throughout the area surveyed in Mexico.
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Adolfo Preciado,Alejandro Ramírez-Gaytan,Nayar Gutierrez,David Vargas,Jose Manuel Falcon,Gil Ochoa 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.2
This paper focuses on the seismic protection of slender old masonry structures by the implementation of prestressing devices at key locations. The devices are vertically and externally located inside the towers in order to be reversible and calibrated. An extensive parametric study on a selected slender tower is carried out based on more than 100 nonlinear static simulations aimed at investigating the impact of different parameters on the seismic performance: (i) different prestressing levels; (ii) shape memory alloy superelasticity and (iii) changes in prestressing-forces in all the stages of the analysis until failure and masonry toe crushing. The tendon materials under analysis are conventional prestressing steel, fiber-reinforced polymers of different fibers and shape memory alloys. The parametric study serves to select the most suitable prestressing device and optimal prestressing level able to dissipate more earthquake energy. The seismic energy dissipation is evaluated by comparing the structural capacity curves in original state and retrofitted.
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