EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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Item Cellular automaton-based simulation of bulk stacking and recovery.(2022) Castro, Matheus Henrique de; Luz, José Aurélio Medeiros da; Milhomem, Felipe de OrquizaStockpiling is a key issue in bulk material handling. A small-scale, quasi-two-dimensional physical model was used to investigate size segregation during stacking and gravitational reclaim of stockpiles and to compare experimental results to those ones generated by a simplified mathematical model. This mathematical model is based on cellular automata and was used to simulate size segregation in conical stockpiles of non-cohesive granular material and gravity flow during its reclaim, through a ground level discharge opening. The present model has taken into account only three particle size class. Banded layers of fine, medium-sized, and coarse particles appear during the pile growth. These stratification patterns have been observed during stockpile formation both in the physical model and in the cellular automaton-based model. Also, experiments in both physical and cellular automaton-based model were carried out to quantify the particle size time evolution of granular material leaving the discharge opening during reclaim. Furthermore, the cellular automaton-based model has successfully simulated segregation phenomena during grav- itational discharging, as well as the topological features of segregation during stockpiling and reclaim.Item Artificial neural network-based committee machine for predicting fuel rate and sulfur contents of a coke blast furnace.(2019) Assis, Paulo Santos; Carvalho, Leonard de Araújo; Irgaliyev, A.Being developed over the centuries, it currently occupies a prominent role in the world production scenario, being the stage of the process related to the obtaining of hot metal an element of great importance to establish the competitiveness of national steel. From this perspective, the control of the process of obtaining hot metal is relevant to ensure competitive prices and a sustainable process. Considering the presented situation, this research developed a committee machine, being three networks to predict each of the study variables, namely: i) fuel rate; ii) sulfur content in hot metal. The committee machine was developed to model the hot metal during the operation of a coke blast furnace, according to the input parameters provided. The results obtained by the committee machine were lower than those of the neural networks acting alone, and the following RMSE values were verified: i) fuel rate: 4.88 (network 1), 4.74 (network 2), 6.14 (network 3) and 4.67 (committee); ii) sulfur content: 0.00915 (network 1), 0.00917 (network 2), 0.00974 (network 3) and 0.00726 (committee). Considering the results obtained, the model can be used to provide important support in monitoring and decision making during the operation.Item Estudo cinético da transformação martensítica no aço microligado USISAR 80T.(2019) Souza, Samuel da Silva de; Moreira, Paulo Sérgio; Faria, Geraldo Lúcio deNo presente trabalho, estudou-se a aplicação de modelos cinéticosde transformação martensíticadisponíveis na literatura técnica a fim de modelar curvas de fração da fase austenita transformada em martensita para o aço USISAR 80T, estrutural, microligado, de boa temperabilidade e considerado de boa soldabilidade. Ensaios dilatométricos foram realizados com taxa de aquecimento de 3°C/s até a temperatura de austenitização de 920°C, tempo de encharque de 180 segundos e taxas de resfriamento de 25°C/s, 50°C/s, 75°C/s e 100°C/s. Um dos modelos estudados apresentou boa correlação com os dados experimentais para todas as taxas de resfriamento estudadas, sendo possível então a obtenção de constantes características da transformação estudada e a proposição de um modelo de previsibilidade para o aço USISAR 80T.Item The influence of flow asymmetry on refractory erosion in the vacuum chamber of a RH degasser.(2019) Melo, Pedro Henrique Resende Vaz de; Peixoto, Johne Jesus Mol; Galante, Gustavo Santos; Loiola, Bruna Helena Malovini; Silva, Carlos Antônio da; Silva, Itavahn Alves da; Seshadri, VaradarajanNozzle blockage in RH reactors is a serious operational problem since it can cause an asymmetric distribution of the steel flow in both the up-leg as well as the lower region of the vacuum chamber. This anomaly can alter the circulation rate in addition to affecting the erosion profile of the lower part of vacuum chamber refractory lining. In this study, the effect of nozzle obstruction on liquid circulation rate, wall shear stress, velocity profiles and flow pattern have been evaluated. In addition, refractory erosion in the vacuum chamber has been estimated through physical modeling and mathematical simulation results. Four blockage conditions were studied for different gas flow rates. There was a good agreement in physical and mathematical models results. Asymmetric flow was observed in vacuum chamber lower region in asymmetric blockage cases, which resulted in preferential wear on one chamber side in physical modeling experiments. The wall shear stress analysis in the vacuum chamber using a fluid dynamic model also indicates preferential erosion. When compared, refractory erosion results in physical modeling and shear stress in mathematical modeling presented good correlation.Item Statistical modeling of fatigue crack growth rate in pre-strained 7475-T7351 aluminum alloy.(2008) Al-Rubaie, Kassim Shamil Fadhil; Barroso, Emerson Kellem Lana; Godefroid, Leonardo BarbosaIn this study, 7475-T7351 aluminum strips were subjected to two tensile pre-strain levels of 3% and 5%. Using compact tension C(T) specimens, fatigue crack growth tests were conducted under constant amplitude loading at stress ratios of 0.1 and 0.5 in air and at room temperature. Three fatigue crack growth rate (FCGR) models, namely, Collipriest, Priddle, and NASGRO were examined. To handle the effect of stress ratio on FCGR, Walker equivalent stress intensity factor model was used. Consequently, generalized Collipriest (GC), generalized Priddle (GP), and generalized NASGRO (GN) models were developed and fitted to the FCGR data. It was shown that both GC and GP models fit the FCGR data in a similar fashion. However, the GP model provided a better fit than the GC model. The GN model was found to be the most appropriate model for the data. Therefore, this model may be suggested for use in critical applications, such as aeronautical structural design.Item Fatigue crack growth analysis of pre-strained 7475–T7351 aluminum alloy.(2006) Al-Rubaie, Kassim Shamil Fadhil; Barroso, Emerson Kellem Lana; Godefroid, Leonardo BarbosaAluminum alloys are widely used in aeronautical design due to their good mechanical properties and low densities. Among these alloys, 7475 (Al–Zn–Mg–Cu), modified from 7075, is successfully used due to strength similar to that of 7075 and superior fracture toughness. In this study, strips of 7475–T7351 were subjected to two tensile pre-strain levels of 3 and 5%. Using compact tension C(T) specimens, fatigue crack growth (FCG) tests were conducted in air under constant amplitude loading at a stress ratio of 0.5. Three FCG rate models, namely Collipriest, Priddle, and modified Forman were examined. The results showed that both fracture toughness and FCG resistance decreased with an increase in the prestrain level. Both Collipriest and Priddle models fit the FCG rate data in a similar fashion. However, the Priddle model provided a better fit than Collipriest. The modified Forman model provided the best fit to the FCG rate data as compared with the other two models. The modified Forman model used to fit other unpublished FCG data and its response was also superior to the others. Therefore, this model may be suggested for use in critical applications, such as aeronautical structural design.