Journal of The Brazilian Society of Mechanical Sciences and Engineering最新文献

Milling is one of the most important processes in the manufacturing industry, and it uses rotating cutting tools to sculpt raw materials into intricate shapes and structures. However, tool wear and breakage present significant challenges influenced by various factors, such as machining parameters and tool fatigue, which directly impact surface quality, dimensional accuracy, and production costs. Therefore, monitoring cutter wear conditions is essential for ensuring milling process efficiency. This study proposes applying BiLSTM networks to classify end mill cutter conditions based on vibration signals. Significant improvements in classification accuracy are achieved by extracting features and employing spectrogram analysis. Specifically, using dual spectral features, instantaneous frequency and spectral entropy, increases the BiLSTM’s average accuracy from 86 to 98.5%, based on a comparative analysis of models trained with raw vibration signals and those trained with extracted spectral features. These findings demonstrate the effectiveness of the proposed method for real-time cutter condition monitoring in milling operations, offering potential benefits for manufacturing processes.

Poromechanical computational homogenization models relate the behavior of a macro-scale poroelastic continuum to phenomena occurring at smaller (and also poroelastic) spatial scales. This paper presents a comprehensive analysis of classical micro-scale boundary conditions for the pore pressure field, namely Taylor boundary condition (TBC-p), linear boundary condition (LBC-p), periodic boundary condition (PBC-p) and uniform boundary flux (UBF-p), in terms of their accuracy in representing primary (pore pressure) and dual (relative fluid velocity) fields in finite-strain multiscale poromechanical problems. A specific benchmark problem was formulated to investigate the performance of these approaches in scenarios where the rate of the volumetric Jacobian is nonzero, a condition of significant physical interest, especially in contexts such as swelling. Numerical results show that the UBF-p and PBC-p approaches effectively capture the behavior of direct numerical simulation (DNS) during the early time steps. However, deviations from the expected behavior occur when the representative volume element (RVE) undergoes significant volume changes. It is concluded that the observed limitations are due to the first-order nature of the multiscale model. This study highlights the need for more sophisticated computational homogenization poromechanical models that can accurately capture the complex interplay between fluid flow and deformation at different length scales. Second-order computational homogenization models can be alternatives to overcome the limitations of first-order multiscale poromechanical models by enriching the information coming from the macro-scale and relaxing the constraints on the fluid flow at the RVE boundaries.

During the actual transportation process, overhead cranes are always affected by the double-pendulum effect, resulting in excessive swinging angles that affect the control performance of the anti-swing system. Moreover, the viscous resistance, air resistance, and swing angle suppression force encountered during transportation have uncertainties and cannot be accurately fed back to the controller’s input, resulting in poor swing angle suppression capability. In order to suppress the undesired swinging of the hook and load, this paper proposes an adaptive coupling anti-swing control strategy with enhanced swing angle suppression under initial input constraints. Specifically, more system parameters are included in the design of the coupling signal, and a sine term is introduced to adjust the oscillation of the hook and load swing angle. At the same time, a hyperbolic tangent term is introduced to suppress the driving force of the overhead crane to prevent excessive driving force from affecting the control performance. Furthermore, for the problem of uncertain parameters, an adaptive law is used to estimate the uncertain parameters online, ultimately designing an adaptive coupling anti-swing controller with enhanced swing angle suppression under initial input constraints. The asymptotic stability of the equilibrium point of the closed-loop system is proven using the Lyapunov method and LaSalle’s invariance principle. Through extensive experimental simulations, the proposed control strategy demonstrates good control performance.

Nodular cast iron is an important material for internal combustion engines inside automobiles and tractors. However, its poor machinability, low efficiency, and severe tool wear during cutting limit the application to a certain extent. In this paper, a novel type of uncoated and coated PcBN milling inserts (C-PcBN) are used for high-speed dry milling of nodular cast iron. The effects of the cutting speed on the wear characteristics, mechanisms, and service life of the milling inserts are systemically investigated by comparing the counterparts of cemented carbide-coated milling inserts (C-YG) with the same model. Additionally, the relationships between cutting speed and the cutting force, temperature, system vibration, and service life are analyzed. The results revealed that the cutting speed has a significant influence on the cutting performance of the three milling inserts. PcBN and C-PCBN are superior to C-YG milling inserts in cutting performance with small wear amount, long service life, and low machining surface roughness value at high speed (more than 400 mm/min).

The manufacturing industry recognizes drilling operations as a significant portion of production, often accounting for a substantial part of overall costs. In the transformative wave of Industry 4.0, new technologies have emerged, presenting remarkable opportunities to enhance machining processes. Thus, this study integrates digital twins (DT) technology to refine drilling operations. Within this framework, a robot actively executed drilling tasks, with the DT closely monitoring and regulating the drilling speed. This research further established a connectivity bridge that facilitates synchronizing the virtual system with the operational process. The article presents a design of experiments in a virtual simulation space to analyze the impact of various parameters. This approach aimed to pinpoint the robot joints wielding the most significant influence on the comprehensive drilling operations sequence. The findings underscored that the J4 joint of the FANUC robot model M-16iB/20 stood out as a critical contributor to the process, influencing it by an impressive margin of 16%. This research demonstrates a promising avenue for harnessing digital twin technology to streamline and optimize manufacturing production, setting a precedent for future explorations in the field.

The pursuit of enhancing manufacturing and production processes has given rise to Additive Manufacturing, a methodology characterized by the production of polymeric, metallic, or composite components with high precision, commonly referred to as three-dimensional printing technology (3D printing). Currently gaining momentum across various sectors, 3D printing is favored for its streamlined production using CAD models in software, finding applications in health, structural and numerical optimization, industrial and construction, automotive, aerospace, and other fields. Furthermore, in the realm of advanced materials, research aims to discover unique structures with noteworthy properties. Auxetic structures, notable for their negative Poisson's ratio, present a characteristic that diverges from conventional materials, showcasing volumetric expansion under tensile forces, in contrast to the contraction experienced by conventional materials. This study endeavors to fabricate auxetic tubes filled with a PU core using Additive Manufacturing and subject them to compression tests. The mechanical test responses will be analyzed and compared with existing literature to assess the enhancement in mechanical rigidity without a significant increase in structural weight. Results indicate that the re-entrant structure yielded the best outcomes, with an energy absorption ratio of 1.08 J/g and an incremental ratio of 23.59, correlating the percentage increase in energy absorption with the percentage increase in mass. Additionally, unexpected behaviors were observed in certain structures: the anti-trichiral structure exhibited a Zero Poisson Ratio (ZPR) behavior, and the dragonfly structure, while inconclusive, leaned toward a ZPR behavior due to the foam diminishing the auxetic effect of the structure.

In order to improve the static and dynamic performance of the crossbeam of five-axis machining centers, a bionic optimization design method based on honeycomb sandwich structures was proposed. The finite element model of a crossbeam was established, and the static and dynamic performance indexes were analyzed. In order to obtain the honeycomb sandwich bionic structure crossbeam, the crossbeam sizes with high static and dynamic performance correlations were obtained using the sensitivity analysis method, and the bionic design for the original crossbeam was carried out based on honeycomb sandwich structures. To select the honeycomb sandwich bionic structure crossbeam with excellent performance, the weight of each index of the total performance of the crossbeam was determined using the analytic hierarchy process, and the variation formula of the total performance of the honeycomb sandwich bionic structure crossbeam was constructed. To obtain the excellent size of the honeycomb sandwich bionic structure crossbeam, the response surface optimization was carried out on the honeycomb sandwich structure crossbeam using the central composite test design method. To select the best candidate points of optimization scheme, the formula for the total performance variation of the crossbeam of the optimized honeycomb sandwich bionic structure was constructed using the analytic hierarchy process. The results show that compared with the original crossbeam, the optimized bionic crossbeam has a small reduction in mass, its maximum total displacement is reduced by 10.16%, its maximum equivalent stress is reduced by 27.61%, its first-order natural frequency is increased by 2.47%, and its second-order natural frequency is increased by 4.85%. The optimization results show that the lightweight of the crossbeam is achieved and its static and dynamic performance is improved, thus proving that the proposed bionic optimization design method based on the honeycomb sandwich structure is reasonable.

One of the most crucial considerations when developing any slurry transportation system is evaluating slurry erosion because it significantly contributes to the system’s many component’s ineffective operation and eventual failure. In the present work, the impact of the thermo-mechanical process (TMP) on the resistance of the slurry erosion wear of the target material has been investigated at a high solid concentration (50–70% fly ash by weight) and different rotational speeds (300–600 rpm) of the specimen. SS431 was used as the target material, and the Gleebles® 3800 simulator was used to perform the TMP on the target material. In the Gleebles® 3800 simulator, four strain rates (0.01, 0.1, 1, and 10 s⁻¹) were used for the deformation at two temperatures (950 °C and 1050 °C). A slurry pot tester evaluated the slurry erosion wear for 15 h at room temperature. TMP specimens exhibit superior resistance to slurry erosion wear compared to as-received SS431 material at all flow parameters. The best resistance to slurry erosion was observed in specimens that had been TMP at 1050 °C with a strain rate of 1 s⁻¹. Correlations had been found between various target material properties (hardness and grain size) as well as flow properties (solid concentration and rotational speed of the specimens) and the slurry erosion wear, all of which contribute to the erosion mechanism.

The rational design of artificial materials with dynamic performance abilities is necessary due to their applications in different fields. Meta-structures are being explored intensively because of their unusual qualities from natural materials, and these traits include Negative Poisson's ratio, high stiffness, high energy absorption, and negative thermal expansion. Meta-structures can be fabricated using additive manufacturing (AM) and obtained from macro- to meso scale; hence are scale-independent. AM fabricates designed geometry using materials like metals, metal alloys, composites, shape memory alloys, and elastomers. AM is a versatile process that can manufacture meta-structures with different geometries, including chiral, re-entrant, cellular, etc. This work comprehensively reviews the materials necessary to manufacture meta-structures, their alternative geometries, and the impact of configuration changes on their mechanical properties. Subsequently, the applications in many disciplines, such as vibration mitigation, noise cancellation, and electromagnetic shielding, as well as their limits and future potential, are also examined.

Graphical abstract

Vibration-assisted cutting (VAC) is an effective way of improving machining quality. Through vibration-assisted cutting experiments, the cutting mechanism of carbon fiber-reinforced polyetheretherketone (CF/PEEK) composites during vibration-assisted cutting and the influencing factors on the quality of machined surfaces were investigated. The effect of cutting-directional vibration-assisted (CDVA) and normal-directional vibration-assisted (NDVA) on cutting force, cutting temperature evolution, chip and surface morphology were analyzed. The experimental results demonstrate that compared with the traditional cutting (TC), the cutting ability of the tool in VAC was enhanced. When the fiber orientation is 0°, 45°, 90° and 135°, the maximum reduction of cutting force in CDVA is 36.48%, 23.43%, 27.19% and 13.04%, and the maximum increase of cutting temperature in NDVA is 23.91%, 28.88%, 14.07% and 19.82%, respectively. VAC can effectively cut fibers and reduce machining damage, and the quality of machined surface is the best in NDVA. Intermittent cutting with vibration in the direction of the main cutting force results in shorter chip contact times and thus lower chip temperatures in CDVA. This study provides insight into the ultrasonic vibration-assisted cutting performance of CF/PEEK and offers ideas for the next generation of high-performance manufacturing of composite materials.