The structure is a component that plays an extremely important role in the equipment's performance, it must withstand efforts without compromising the function, receive and transfer heat, dampen vibrations and position the elements, as well as promote ergonomics and aesthetics. In lightweight and precision equipment's the raw material used must also allow thin walls, rigid, resistant and low density. The objective of the present work is the development of a synthetic granite composite for manufacturing of equipment's structures. For this, an abundant Brazilian granite, a high strength epoxy resin and segmented carbon fibers were selected as materials. Test specimens, with maximized packing with granite gravel less than 2.0 mm were fabricated and tested for tensile strength, compression, flexural, damping, hardness, dilatometry, thermal conductivity and density. The maximized composition supported flexural stresses above 42 MPa, without fiber reinforcement and 51 MPa with carbon fiber reinforcement. The damping coefficient was about 7 times higher than cast iron, coefficient of thermal expansion of 1.4E-05 m/m.K, thermal conductivity coefficient of 1.2 W/m.K and density of 2.1 g/cm³. The developed composite showed potential for refining structures, with ease of molding of thin-walled elements, use of inserts, re-machining, providing economical manufacture of single parts, and is still able to perform the function with high damping coefficient and low weight.

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The use of vibration monitors is a well-established practice in industrial maintenance, usually vibration sensors are positioned at specific points on the monitored machinery and data are continuously collected to feed a machine operating health control system. Nevertheless, the technology for obtaining the signal, its treatment and analysis is generally expensive, and the financial return is not evident, which justifies the development of low-cost alternatives technologies. In this work was performed an analysis of the responses of two Micro-Electro-Mechanical accelerometers, models ADXL345 and MPU6050, exposed to a low intensity random signal and standard operating frequency. The objective of the analysis was to verify the capacity of these devices to be used as mechanical vibration sensors for rotating machines. For this purpose, offset shift analyzes of the sensors due to the Earth's gravitational field were performed, as well as vibrational spectrum and rectification errors analysis under multiple conditions. The data pointed to a greater uniformity of the MPU6050 response, while several behavioral anomalies were seen in the ADXL345, when these sensors are exposed to the same mechanical signal. The qualitative and quantitative behavior of MPU6050 rectification error was consistent with reported in the literature. It was noted that the methodology used can profile the behavior of sensors, however, it is not sufficient to safely justify the inaccuracies, requiring that the tests be performed on a statistically representative number of sensors from different manufacturers and batches.

No abstract

This work deals with the design and manufacturing of a mini machine for grinding of green ceramic balls. Balls of advanced ceramics find wide application in high-precision components such as hybrid bearings or as bearings of hip prostheses. The large demand for advanced ceramic balls in these components is due to their unique combination of properties such as high dimensional stability, high hardness, low coefficient of thermal expansion, biocompatibility (bio inert) and high compressive strength. However the high performance can only be achieved if the balls have narrow tolerances (size and shape) and ultra-fine surface finish. This work aims to design and manufacture a mini prototype machine to obtain a green ceramic balls up to 30 mm in diameter. The project development was driven by a mechanical design methodology and after the concept generation a virtual pre-design has been generated followed by manufacturing a prototype, the initial concept is composed of three wheels, two of drag that having variables turning speeds and directions, promote a random orbital effect in the balls necessary to reduce the sphericity error. Spherical zirconia blanks were shaped by isostatic pressing and machined in the built prototype. The balls were characterized by measuring sphericity error and surface roughness.