Journal of Mechanical Science and Technology最新文献

We attempted to optimize the process-based parameters during friction stir welding of AZ80A - AZ31B Mg alloys with the objective of enhancing the mechanical properties of the fabricated joints. A response surface method based grey relational analysis was employed using three factors and three distinctive levels. A central composite design based multi-objective numerical model using the technique of grey relational analysis was formulated for optimizing the tool dependent parameters, namely tool’s rotational speed, its speed of traverse and geometry of the pin. Grey relational grade was determined for all the responses: tensile strength and elongation percentage. Analysis of variance was employed for attaining grey relational grade to determine the most influential parameter of the FSW process. It was observed that the geometry of the tool pin had a greater impact in ascertaining the quality of the fabricated Mg alloy joints, and the tool possessing tapered cylindrical pin geometry exhibited larger values of grey relational grade. Optimized process parameter settings based on the attained GRG values were recorded to be 1100 rpm rotational speed, speed of traverse of 1.5 mm/sec and a tool with taper cylindrical pin geometry. The anticipated values were validated through confirmation investigational runs performed during employment of optimized parameter combinations, which exhibited a perfect agreement with the investigational run values and the confirmatory joint exhibited a tensile strength of 260.42 MPa and elongation percentage of 6.53.

In this paper, the noise reduction performance of the active steering bogie, developed to address wheel and rail wear and reduce noise during train operation in curved sections, was evaluated. A prototype of the active steering bogie was installed on the test train, and noise reduction performance by active steering control was measured in curved sections of a commercial line with a radius of curve of 300 m or less. The results of the test run confirmed that both the wheel and car interior noise were reduced when active steering control was applied, compared with the case where it was not applied. According to the test results in the curved section with the most noise reduction effect, the equivalent noise level was reduced by 6.6 dB for wheels and 4.7 dB for the car body by active steering control. In addition, analyzing the frequency characteristics by wheel steering control has confirmed that the squeal noise mode generated in the 300 to 2000 Hz band during curve running was significantly reduced. Therefore, the noise reduction performance of the active steering bogie, developed to improve steering performance in curved sections, has been sufficiently verified through the test results.

Error transformation can be used to evaluate the kinematic performance of a parallel manipulator. However, the terminal error of redundantly actuated parallel manipulators is difficult to calculate from joint errors. This paper proposes a method to approximate the terminal error of a redundantly actuated parallel manipulator by taking the minimum terminal error among all corresponding nonredundant counterparts. The local Frobenius norm index (LFNI) is proposed to estimate the expectation of terminal error. Additionally, the global Frobenius norm index (GFNI) is introduced to describe the worst case of terminal error in the workspace, which is then used for the optimum design of a RPU-UPR-2UPU redundantly actuated parallel manipulator. After the optimum design, the average root mean square error of the manipulator is reduced. Furthermore, a control mode determination strategy for allocating force/position control to a certain chain is also proposed to minimize the terminal error, whose effectiveness is validated through simulation.

In autonomous driving of the mobile robot, the robot’s current location should be identified first to plan and move a path to the target location. Accordingly, research on the robot’s localization using GPS, 3D LiDAR, and Vision has been actively conducted. However, there is a limitation in that it is difficult to locate robots in indoor spaces where signals are disturbed by walls or ceilings, or in areas where sufficient environmental information cannot be obtained. This paper introduces the robot’s position estimation method to overcome these environmental problems by using sensor fusion in an indoor tennis court. We propose a localization method that has low latency performance and high location accuracy through the use of Kalman filters to fuse data from wheel odometry and visual-inertial odometry. To evaluate its performance, this method was compared against wheel odometry, visual-inertial odometry, and LIO-SAM after the robot completed three rectangular paths. The resultant mean absolute errors in the x and y directions were 1.908 m and 0.707 m for wheel odometry, 1.169 m and 1.430 m for visual-inertial odometry, and 0.400 m and 0.383 m for LIO-SAM, respectively. In contrast, the wheel-visual-inertial odometry introduced in this study reported errors of 0.209 m and 0.103 m in the x and y directions, respectively, indicating superior accuracy compared to the other algorithms. This underscores the effectiveness of the proposed method in indoor environments where signals can be obstructed by walls or ceilings, or in areas lacking abundant environmental information.

Advances in additive manufacturing technology have made it possible to produce complex structures. Utilizing this manufacturing technology, compact heat exchangers with triple periodic minimal surface (TPMS) structures have been proposed and implemented for highly thermal-efficient devices with limited space. However, design process of complex compact heat exchangers is still time-consuming and labor dependent. This study aims to develop a design framework for TPMS-based compact heat exchangers. In the first step, a TPMS structure and compact heat exchanger geometries are modeled based on implicit modeling techniques. In the next step, a parametric study based on computational fluid dynamics (CFD) simulations is performed to evaluate the heat exchanging performance for three structures: gyroid, Schwarz-P, and diamond. In the final step, a design modification algorithm for compact heat exchangers is proposed. The proposed approach performs automatic shape correction based on resulting pressure drop distribution from the CFD simulation.

This study concerns the position tracking control of the hybrid-powered barrel elevator (HPBE) with dual-channel model uncertainty and output constraints. To realize an outstanding control performance, a dual-extended-state-observer-based command filtered adaptive prescribed performance control (DESO-CFAPPC) strategy is presented based on the dynamic model considering various nonlinearities and model uncertainties. The conjunction of the PPC and barrier Lyapunov function in the DESO-CFAPPC not only prevents violation of output constraints of the barrel, but also prevents the complex calculation caused by the logarithmic ETF in the traditional PPC. The adaptive laws are constructed to estimate uncertain parameters. The DESO further estimates the unknown velocity, mismatched and matched model uncertainties. The obtained estimates are incorporated into the control law to enhance the tracking performance. The stability and convergence of the DESO-CFAPPC are theoretically proved and comparative experimental results indicate the effectiveness of the proposed strategy.

This work provides novel insights into the uncertainty quantification and reliability sensitivity analysis of a direct-operated relief valve undergoing vibration. A reliability model for pressure tolerance failure of the relief valve is developed based on the criterion that the pressure tolerance exceeded the allowable value, incorporating the vibration and multiparameter uncertainty. The Simulink simulation is employed to analyze the nonlinear behaviors of the valve. To avoid excessive nonlinear calculations, a Kriging-based strategy is adopted for reliability sensitivity analysis, allowing for rapid estimation of nonlinear responses. The results are compared with those obtained by MCS to verify the performance of the proposed method. The sensitivity results indicate that the proposed method saves 98 % of computational time without much loss of accuracy. Furthermore, more attention should be paid to the spring stiffness, valve element mass, and controlled chamber volume in the structural reliability design of relief valves.

The residual stress causes a premature failure of the manufactured product by a directed energy deposition (DED) process. The stress-relief annealing process can effectively decrease the residual stress. However, the research on the stress-relief annealing on residual stress characteristics of the fabricated part by the DED process consisting of heterogeneous materials has hardly performed yet. The goal of this research work is to investigate the effects of the furnace temperature of stress-relief annealing on residual stress and hardness characteristics of heterogeneous materials fabricated from the DED process. The as-built specimen was created by the deposition of Gridur 6 (G6) powders on AISI 1045 substrates using the DED head of DVF-8000AML. The stress-relief annealing process of the as-built specimen was carried out using an electric furnace. The influence of the furnace temperature on the surface morphology, the residual stress of the boundary region and the hardness of top and bottom surfaces was discussed. Finally, proper furnace temperatures of the stress-relief annealing were proposed.

The motto of research is to attempt to enrich the mechanical and fracture resistance quality of AA5052 alloy composite composed by the adaptations of 0, 3, 6, and 9 weight percentages (wt%) of silicon carbide (SiC) nanoparticle and 5 wt% of chopped E-glass fiber through vacuum-assisted stir processing under 500 rpm. The metallography analysis of composite samples is analyzed and spots the good interfacial with void-less structure. The composite’s mechanical and fracture qualities enriched through the inclusion of SiC (9 wt%) / E-glass fiber (5 wt%) in AA5052 alloy composite attained the highest tensile strength, better hardness, improved elongation percentage and excellent fracture toughness, which is enhanced by 25.5, 33.8, 22, and 15 % comparable to the value of monolithic AA5052 alloy cast. The E-glass configured hybrid AA5052/SiC alloy composite is suggested for automotive body structural applications.

A joystick set for controlling different degrees of freedom was designed, materialized and characterized. The joystick was designed for 3D printing, improved through several iterations, producing multiple samples using multi-material additive manufacturing. Two different materials (one structural and another conductive) were used in the filament material extrusion process to obtain resistive-based sensing unit elements. The sensor was put into operation via a voltage divider circuit. Experimentation was implemented in a testing bed (analogic sensor), in a real context (binary mode) and in a simulation environment (multiple-state signal) for the command of a robotized wheelchair. The final design is capable to meet the requirements of reducing the material used and the printing times. The results reveal the possibility of using 3D printed resistive-based sensing units to implement binary signals as well as multiple state signals and the sensor set has been evaluated by controlling a robotized wheelchair.