Journal of Mechanical Science and Technology最新文献

In long-term operation, the gradual degradation process of automotive friction pads significantly affects the expected performance of mechanical equipment. In addition, the intrinsic correlations between friction properties and the multi-stage degradation process have been mostly ignored, leading to less accurate prediction of results under multifactorial influences on working conditions. In this paper, we propose a novel prediction method using the CNN-BiLSTM-Att model to overcome the problem. The model uses CNN to extract the friction features in the processed data, and combines with BiLSTM to evaluate the time series features hidden in the friction data. To improve the prediction accuracy, the attention mechanism is fed into the proposed model, which has the advantage of automatically assigning appropriate weights to the hidden layer states to distinguish the importance of different data features. Compared with other machine learning algorithms, the method has high prediction accuracy and can provide reference for braking.

The research attempted to enrich the aluminium alloy (Al/Mg) nanocomposite with silicon carbide (SiC). The ultrasonic assist stir cast established that the Al/Mgnanocomposite is involved in microstructure, hardness and tensile performance. Its result is uniform dispersion without agglomeration, and 7.5 wt% SiC owns higher microhardness and better tensile strength of 161±1.5 H V and 238±2 MPa. This nano Al/Mg alloy composite is subjected to machining studies by using a vertical CNC milling setup & titanium nitride (TiN) coated end mill functioned by 300–1200 rpm spindle speed (N), 0.01–0.04mm/rev feed rate (FR) and 0.1–0.4 mm depth of cut (DOC). The impact DOC, FR, and N on material removal rate (MRR), temperature (T), and tool wear (Tw) are measured, and the L16 design experiment (ANOVA-GLM) is defined. Finally, the best interaction input milling parameter pairs on obtaining high MRR with the least T and Tw. The DOC is the most significant factor in controlling the MRR, T and Tw.

Valveless micropump, important components of a microfluidic system, are widely used in biomedicine, chemical industry, microelectronics cooling and other fields. At present, the driving mode of micropump is mainly single drive, resulting in insufficient driving force and low output pressure. In this study, the overall structure of valveless micropump is designed, and the driving component and the internal inlet and outlet are compared and analyzed by finite element simulation. Moreover, the valveless micropump prototype is processed and developed for performance test. Results show that the output performance of the valveless micropump driven by piezoelectric and heating coupling is better than that of the piezoelectric micropump. When the ambient temperature was 20 °C, 140 V voltage and 40 Hz frequency were added to the piezoelectric component, as well as a 3A current to the heating plate. Furthermore, the liquid flow rate through the microneedle was 0.98 µl/s after a period of time.

Steel-coped beams are used in industrial structures to accommodate a cluster of water mains, fire hydrants, power cables and telecommunication wires. The coped regions restrict the ultimate capacity and cause unfavorable failure modes. The current study investigates the structural assessment of the coped section in offshore topsides while their use enhances operational safety for drilling and production. The structural evaluation is done through 2D digital image correlation (DIC) experiments to quantify the influence of various cope geometries. The DIC technique illustrated the strain and deformation measurements under different loading conditions for different coped geometry. The primary failure mode observed in local web buckling is characterized by noticeable lateral displacement and the development of buckling lines over the coped web. Studies showed the influence of the cope depth on the load-carrying capacity and buckling processes for different cope geometries. The results of the DIC analysis are strongly aligned with experimental data and finite element numerical results, suggesting this technique to the structural assessment of coped section.

The computer numerical control swivel head drive system has a number of states from ideal operation to complete failure, and dividing these states into success and failure is not rational and may even lead to fatal errors. Given this problem, this study proposed a method of building a multistate reliability evaluation model based on a Bayesian network (BN). First, BN was built in accordance with the mechanism of the drive system and in consideration of the interaction between different failure modes. Second, stable working data were used to determine the failure probabilities in the different life cycles of nodes. Last, a probability distribution table was employed to describe the multistate characteristics of nodes, and a BN model of the multistate system was built. The ranking of the importance of risks that may lead to drive system failure was determined using the posterior probability calculation method of BN.

Heat characteristics of air vehicle motors are essential for the design of electric aircraft because of heat generation when air vehicle takes off. In this study, the numerical simulation of a water-cooled AFPM motor was carried out to obtain heat transfer characteristics. A simplified computational domain was adopted with coolant passages, and electromagnetic losses of copper, iron, and eddy currents were considered. The steady-state and incompressible flows were assumed to represent the cruising flying condition of the 150-kW power rating in the motor. The system pressure loss and coil temperature were analyzed by changing passage configurations in 4-partition cases. To resolve thermal imbalance, it is best to have the number of channel partitions increase upstream and gradually decrease as you go downstream. This study allows motor designers for air vehicles to evaluate various coolant passage configurations numerically in advance.

Rapid prediction of substrate deformation for thin-wall component repairing of Ti–6.5Al–3.5Mo–1.5Zr–0.3Si alloy by laser deposition technology was investigated for the optimization of the laser scanning strategy and improvement of the repair efficiency. A local model based on thermo elastic-plastic theory was established for inherent strain extraction. On this basis, an inherent strain model was built to simulate the deformation of long side and short side reciprocating deposition. Prediction accuracy and computational efficiency of the proposed inherent strain model were compared with the classic thermo elastic-plastic predictive and the experimental results. The results show that prediction error of the inherent strain model was 7.35 %. Though lower than the classic thermo elastic-plastic prediction (2.42 %), calculation time was reduced to 18 %∼41 % of that based on the thermo elastic-plastic model. Moreover, substrate distortion was well controlled when the scanning path was parallel to the fixed constraint surface since the residual stress was smaller.

This paper presents a numerical exploration of shock waves and high-speed microjets induced by the collapse of bubbles near a wall in a pressurized liquid using a recently developed compressible multiphase flow model. The mathematical model utilized in this study ensures full conservation, which is a critical factor for faithfully representing shock phenomena. The numerical methodology integrates the principles of compressibility and thermodynamics to accurately simulate the intricate flow behavior. A shock-capturing method is employed along with a precise Riemann solver and a high-order scheme to capture intense shocks effectively. This investigation examines the propagation of pressure waves, shock structures, and highspeed liquid jets generated by bubble collapses near a wall under various pressurized ambient conditions. This study aims to provide a comprehensive understanding of the bubble collapse phenomena in high-pressure environments, thereby elucidating the associated physical aspects.

Advanced forming manufacturing technology is developing toward high efficiency, low energy consumption, green environmental protection, and precision, which promotes the development trend of high-strength and lightweight metal structural materials. This study employs the selective laser melting technology to form a periodic spatial lattice structure model with optimal load-bearing capacity by using TC4 as the experimental material to prepare experimental samples. Using orthogonal tests, loading tests, and metallographic structure analysis methods, the influence of different combinations of laser power, scanning speed, and support form on the mechanical properties of different weight reduction scale models is explored. When the SLM laser power is 290 W, the scanning speed is 900 mm/s, and the volume support is 3, the process combination has the best load-bearing capacity when forming periodic spatial mesh structure models with different weight reduction ratios (30 %, 50 % and 70 %).

The consideration of aeroelasticity is essential during the development phase of axial flow compressors, and its implications should be factored into the operational planning of gas turbines. While synchronous vibration can typically be mitigated during the blade design stage, the complete avoidance of non-synchronous vibration remains a challenge, prompting ongoing research efforts for predictive solutions. The study utilized an industrial gas turbine axial compressor with 1.5-stage blades for aerodynamic performance and flutter assessments. The calculated results were comprehensively compared with those of 1.5-stage scaled rig test. The comparative analysis demonstrated a strong alignment between predictions regarding aerodynamic performance and the presence or absence of flutter. Furthermore, unsteady flutter calculations were conducted for cases both with and without flutter, allowing for a detailed analysis of the factors contributing to flutter occurrence. Through this investigation, the study established methodologies for aeroelastic design and evaluation, along with a proposed approach for preventing flutter generation.