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O ensaio de resistência à fadiga é um meio de especificar limites de tensão e de tempo de uso de uma peça ou elemento de máquina. A ruptura por fadiga começa a partir de uma trinca (nucleação) ou pequena falha superficial, que se propaga ampliando seu tamanho. Sempre que possível, deve-se evitar a concentração de tensões. Em um eixo, geralmente, encontra-se um elemento que concentra tensão e, consequentemente, diminui a resistência à fadiga. Esse elemento trata-se de
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Em 1922, Rockwell desenvolveu um método de ensaio de dureza que utilizava um sistema de pré-carga. O método de ensaio de dureza Rockwell apresenta algumas vantagens em relação ao método de ensaio de dureza Brinell. Assinale a alternativa que apresenta uma DESVANTAGEM que o método de ensaio Brinell apresenta em relação ao método de ensaio Rockwell.
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O ensaio de dureza Brinell consiste em comprimir lentamente uma esfera de aço temperado, de diâmetro D, sobre uma superfície plana, polida e limpa de um metal, por meio de uma carga F, durante um tempo t, produzindo uma calota esférica de diâmetro d. É correto afirmar que, ao ensaiar uma chapa, usando uma esfera com 10 mm de diâmetro, produzindo uma profundidade da calota em 0,62 mm, a espessura mínima da chapa, em mm, deve ser de
Provas
Ao ocorrer o corte, as partes se movimentam paralelamente, por escorregamento, uma sobre a outra, separando-se. A esse fenômeno dá-se o nome de cisalhamento. É correto afirmar que o material, cuja tensão de tração é 690 MPa, terá a tensão de cisalhamento em
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Ao realizar o projeto de uma máquina, é comum executar ensaios mecânicos nas suas peças. Esse ensaio consiste em sujeitar uma peça já fabricada, ou o material do qual a peça será executada, a situações que simulam os esforços que irá sofrer nas reais condições de uso.
A figura anterior representa uma peça sofrendo esforço de uma força que provoca uma deformação elástica. Trata-se de um esforço de
Provas
Science and the olympics: technology's increasing role in the games
People used to rarely associate science with sports, but increased engineering research and investment in technology by professional sporting organizations have merged the two industries, especially in the 2012 London Olympics.
Scientists and engineers played a significant role in shaping the Great Britain Olympic team, according to BBC News. Though the partnership between sports and science has been a relatively new development, the impact of it can be seen across a number of different events.
Mobile technology, smartphones and tablet computers are found in droves at the London Olympics, as coaches, players and country officials can be seen using these devices to gauge and improve their performance.
According to the news outlet, the ease with which these devices can be integrated into sports has been surprising, but the results are hard to ignore.
(http://why.knovel.com/all-engineering-news/1752-science-and-the-olympics-technologys-increasing-role-in-the-games.html – Com adaptações.)
The conjunction highlighted in “Though the partnership between sports and science has been a relatively new development…” could be replaced, without change of meaning, by
Provas
Science and the olympics: technology's increasing role in the games
People used to rarely associate science with sports, but increased engineering research and investment in technology by professional sporting organizations have merged the two industries, especially in the 2012 London Olympics.
Scientists and engineers played a significant role in shaping the Great Britain Olympic team, according to BBC News. Though the partnership between sports and science has been a relatively new development, the impact of it can be seen across a number of different events.
Mobile technology, smartphones and tablet computers are found in droves at the London Olympics, as coaches, players and country officials can be seen using these devices to gauge and improve their performance.
According to the news outlet, the ease with which these devices can be integrated into sports has been surprising, but the results are hard to ignore.
(http://why.knovel.com/all-engineering-news/1752-science-and-the-olympics-technologys-increasing-role-in-the-games.html – Com adaptações.)
The passive voice in “Mobile technology, smartphones and tablet computers are found in droves at the London Olympics” in the active voice is
Provas
Science and the olympics: technology's increasing role in the games
People used to rarely associate science with sports, but increased engineering research and investment in technology by professional sporting organizations have merged the two industries, especially in the 2012 London Olympics.
Scientists and engineers played a significant role in shaping the Great Britain Olympic team, according to BBC News. Though the partnership between sports and science has been a relatively new development, the impact of it can be seen across a number of different events.
Mobile technology, smartphones and tablet computers are found in droves at the London Olympics, as coaches, players and country officials can be seen using these devices to gauge and improve their performance.
According to the news outlet, the ease with which these devices can be integrated into sports has been surprising, but the results are hard to ignore.
(http://why.knovel.com/all-engineering-news/1752-science-and-the-olympics-technologys-increasing-role-in-the-games.html – Com adaptações.)
The main idea of the first paragraph is that
Provas
Mechanical engineers develop an “intelligent co-pilot” for cars
Semiautonomous system takes the wheel to keep drivers safe.
Jennifer Chu, MIT News Office
July 13, 2012
Barrels and cones dot an open field in Saline, Mich., forming an obstacle course for a modified vehicle. A driver remotely steers the vehicle through the course from a nearby location as a researcher looks on. Occasionally, the researcher instructs the driver to keep the wheel straight – a trajectory that appears to put the vehicle on a collision course with a barrel. Despite the driver’s actions, the vehicle steers itself around the obstacle, transitioning control back to the driver once the danger has passed.
The key to the maneuver is a new semiautonomous safety system developed by Sterling Anderson, a PhD student in MIT’s Department of Mechanical Engineering, and Karl Lagnemma, a principal research scientist in MIT’s Robotic Mobility Group.
The system uses an onboard camera and laser rangefinder to identify hazards in a vehicle’s environment. The team devised an algorithm to analyze the data and identify safe zones – avoiding, for example, barrels in a field, or other cars on a roadway. The system allows a driver to control the vehicle, only taking the wheel when the driver is about to exit a safe zone.
Anderson, who has been testing the system in Michigan since last September, describes it as an “intelligent co-pilot” that monitors a driver’s performance and makes behind-the-scenes adjustments to keep the vehicle from colliding with obstacles, or within a safe region of the environment, such as a lane or open area.
“The real innovation is enabling the car to share (control) with you,” Anderson says. “If you want to drive, it’ll just… make sure you don’t hit anything.”
The group presented details of the safety system recently at the Intelligent Vehicles Symposium in Spain.
(http://web.mit.edu/newsoffice/2012/mechanical-engineers-develop-intelligent-car-co-pilot-0713.html – Com adaptações.)
Mark the alternative that presents the correct relation between the fragment and the brackets.
I. “Anderson, who has been testing the system in Michigan since last September, describes it as an ‘intelligent copilot’ that monitors a driver’s performance…” (Anderson)
II. “… the researcher instructs the driver to keep the wheel straight – a trajectory that appears to put the vehicle on a collision course with a barrel.” (trajectory)
III. “Anderson, who has been testing the system in Michigan since last September, describes it as an ‘intelligent copilot’ that monitors a driver’s performance” (co-pilot)
Provas
Mechanical engineers develop an “intelligent co-pilot” for cars
Semiautonomous system takes the wheel to keep drivers safe.
Jennifer Chu, MIT News Office
July 13, 2012
Barrels and cones dot an open field in Saline, Mich., forming an obstacle course for a modified vehicle. A driver remotely steers the vehicle through the course from a nearby location as a researcher looks on. Occasionally, the researcher instructs the driver to keep the wheel straight – a trajectory that appears to put the vehicle on a collision course with a barrel. Despite the driver’s actions, the vehicle steers itself around the obstacle, transitioning control back to the driver once the danger has passed.
The key to the maneuver is a new semiautonomous safety system developed by Sterling Anderson, a PhD student in MIT’s Department of Mechanical Engineering, and Karl Lagnemma, a principal research scientist in MIT’s Robotic Mobility Group.
The system uses an onboard camera and laser rangefinder to identify hazards in a vehicle’s environment. The team devised an algorithm to analyze the data and identify safe zones – avoiding, for example, barrels in a field, or other cars on a roadway. The system allows a driver to control the vehicle, only taking the wheel when the driver is about to exit a safe zone.
Anderson, who has been testing the system in Michigan since last September, describes it as an “intelligent co-pilot” that monitors a driver’s performance and makes behind-the-scenes adjustments to keep the vehicle from colliding with obstacles, or within a safe region of the environment, such as a lane or open area.
“The real innovation is enabling the car to share (control) with you,” Anderson says. “If you want to drive, it’ll just… make sure you don’t hit anything.”
The group presented details of the safety system recently at the Intelligent Vehicles Symposium in Spain.
(http://web.mit.edu/newsoffice/2012/mechanical-engineers-develop-intelligent-car-co-pilot-0713.html – Com adaptações.)
Each verb tense presents verb aspects which reveal what we want to express about the point in time the action takes place. The highlighted verb tense in “The system uses an onboard camera and laser rangefinder…” expresses
Provas
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