Navegando por Autor "Abrão, Alexandre Mendes"

Agora exibindo 1 - 2 de 2

Effect of Nb addition on the machinability of a pearlitic gray cast iron.
(2022) Reis, Bárbara Cristina Mendanha; Santos, Anderson Júnior dos; Pereira, Natália Fernanda Santos; Carmo, Denilson José do; Faria, Geraldo Lúcio de; Câmara, Marcelo Araújo; Faria, Paulo Eustáquio de; Abrão, Alexandre Mendes
Due to its high thermal conductivity, good damping performance and superior machinability, gray cast iron (GCI) has found many applications in the automotive industry. However, this material has given way to other cast irons due to the need for materials with higher mechanical strength and toughness. Actual efforts have been made to reformulate the GCI chemical composition to obtain different microstructures for improving its mechanical properties. In this study, the influence of Nb content on the microstructure and machinability of GCI was investigated when turning under cutting speeds of 240, 360, and 480 m/min, feed rates of 0.25 and 0.50 mm/rev, and using two different chip breaker geometries (Flat Top and GH). The Nb addition decreased the graphite size and refined the pearlitic interlamellar spacing. However, it did not produce significant alteration in the number of eutectic cells and hardness. Regardless of the Nb content, the presence of chip breaker GH and the lower levels of cutting speed and feed rate were associated with superior machinability. The increase in the Nb content in the GCI raised all the components of the machining forces, yet it did not promote significant changes in the chip temperature and decreased the surface roughness after turning.
Tool life monitoring in end milling of AISI H13 hot work die steel using a low‑cost vibration sensor connected to a wireless system.
(2022) Vianello, Pedro Ivo Alves; Abrão, Alexandre Mendes; Maia, Antônio Augusto Torres; Pereira, Igor Cezar
Machining of complex components with high added value requires the development and implementation of technologies for monitoring the processes outputs and to ensure the performance and reliability of the manufactured part. Cutting tool wear is one of the most relevant variables in machining due to its efect on both the machining cost and quality of the manufactured component. Although tool wear has been extensively investigated for more than a century, the advent of Industry 4.0 has required more accurate and reliable monitoring systems. This work investigates the feasibility of using a low-cost vibration sensor, based on a micro-electromechanical system (MEMS), connected to a wireless data transmission system attached to a rotary tool (milling cutter) for tool wear monitoring when milling annealed AISI H13 hot work die with coated tungsten carbide inserts. A microcontroller with an integrated internet connection connected to a local server through the Wi-Fi network was employed. In order to validate the proposed system, tests were performed comparing its behavior with a conventional piezoelectric sensor in terms of sensitivity to changes in the cutting conditions and tool wear evolution. The results indicated that the proposed system responds satisfactorily to changes in the cutting conditions, with approximately a four-fold increase in the acceleration amplitude when either cutting speed or axial depth of cut were doubled. Although neither the MEMS nor the piezoelectric accelerometer was capable to detect tool wear evolution (considering a tool life criterion VBB=0.3 mm), the RMS value of the signal generated by the vibration sensor based on MEMS is approximately four times higher than that provided by the piezoelectric accelerometer, thus indicating a better representation of the vibration phenomenon resulting from fxing the MEMS on the tool (in contrast to the piezoelectric accelerometer attached to the workpiece).