Abstract:

In the transportation and distribution of goods, cardboard boxes are often subjected to mechanical impacts such as shocks and random vibrations, which can cause damage to the goods. Many studies have focused on the durability of corrugated cardboard boxes. However, there is very limited research on compact cardboard boxes, especially in the case of exposure to random vibrations. In this study, static and dynamic tests on cardboard boxes were designed and conducted to determine compression strength, natural frequencies, and modal characteristics of the boxes. Subsequently, a finite element model of cardboard boxes taking into account the effects of the box manufacturing process on the mechanical properties of the cardboard, was developed to perform numerical simulations under compression and random vibrations. In this context, the in-plane orthotropic elastic-plastic behavior model of rigid cardboard was implemented in the Abaqus software through a VUMAT subroutine. Additionally, the parameters of the model were determined through an inverse identification process. Finally, numerical simulations of compression and random vibration tests were carried out to validate the experimental results. The comparison results show that the power spectral density (PSD) response of the mass/box system under random vibrations obtained through numerical simulations is consistent with the responses obtained from experimental measurements. Furthermore, the predicted force-displacement curves demonstrate good agreement with the measured curves.

Abstract:

Based on the small perturbation method, the transient pressure control equation considering real gas effects was solved, and the fitting expression for the dynamic characteristic parameters of the gas film during the start-up process was obtained. Subsequently, the influence of structural parameters of spiral groove dry gas seals on the dynamic tracking of the stationary ring's motion during the non-steady-state start-up process under three degree of freedom perturbations was analyzed. The results show that when the stationary and rotating rings initially separate, the stationary ring exhibits good tracking performance for both axial and angular motions of the rotating ring, although the tracking capability varies significantly. As time and film thickness increase, the tracking capability gradually weakens, and at the working film thickness, the tracking parameters tend to stabilize when the working film thickness is reached. Larger spiral angles and deeper dynamic pressure grooves, the poorer the axial and angular tracking performance of the sealing ring. The number of grooves has a minimal impact on the axial and angular tracking performance of the stationary ring. A higher balance coefficient improves the axial and angular tracking performance of the stationary ring.

Abstract: This study presents the kinematic synthesis of planar mechanisms using precision point analysis for three, four, and five target positions. The research explores the application of graphical synthesis techniques to design mechanisms that accurately follow prescribed motion paths. Various configurations are examined, comparing their synthesized motion with theoretical precision points to evaluate the accuracy and feasibility of the proposed designs. Additionally, numerical optimization methods are considered to refine the results and improve motion fidelity. The study also extends the discussion to higher-order synthesis, incorporating additional precision points for improved accuracy in motion generation. The graphical results highlight the effectiveness of the synthesis approach, demonstrating its applicability to practical mechanism design. The findings contribute to the understanding of planar mechanism synthesis and provide insights into enhancing design methodologies for motion control applications. This paper presents GIM software, an educational and research software designed to facilitate the kinematic analysis of planar mechanisms. The software was developed to address the challenges students face in understanding kinematic theory and mechanism synthesis, providing an interactive and user-friendly platform for modeling and analyzing n-degree-of-freedom linkages.

Abstract:

Inside the closed, thin-walled hollow cylinder, there is a solid state of phase change material (NePCM) that has been nano-enhanced. This NePCM is heated at its bottom. Nanoparticles (Al2O3) were inserted and homogenized within the PCM (sodium acetate trihydrate, C2H3O2Na), to create the NePCM. The hollow cylinder is thermally insulated from the outside ambient temperature, while the heat supplied is enough to cause a phase change. Once the entire NePCM has converted from a solid to a liquid due to heating, it is then cooled, and the thermal insulation is removed. The cylindrical liquefied NePCM bar is cooled in this manner. Thermal entropy, entransy dissipation rate, and bar efficiency during the heating and cooling of NePCM bar were analyzed by changing variables. The volume fraction ratio of nanoparticles, inlet heat flux, and liquefied bar height were the variables considered. The results indicate a significant impact on the NePCM bar during liquefaction and convective cooling when the values of these variables are altered. For instance, with an increase in the volume fraction ratio from 3% to 9%, at a constant heat flux of 104 Wm-2 and a liquefied bar height of 0.02m, the NePCM bar efficiency decreases to 99%. The thermal entropy from heat conduction through liquefied NePCM bar is significantly lower compared to thermal entropy from convective air cooling on its surface. The thermal entropy of the liquefied NePCM bar increases on average by 110% without any cooling. With a volume fraction ratio of 6%, there is an 80% increase in heat flux as the bar height increases to 0.02m.

Abstract:

Orbital TIG welding is widely applied to weld pipes to pipes in many fields, such as food, chemical, oil, gas, and transportation. Optimizing welding parameters such as voltage, current, and travel speed is critical to achieve a good quality weld. This study investigates the impacts of orbital welding parameters and filler wire diameters on the tensile strength of 304 stainless steel pipes. The 304 stainless steel pipe has an outer diameter of 76 mm and a thickness of 2 mm. Filler wire is used with the workpiece and is available in three diameters of 0.8 mm, 1 mm, and 1.2 mm; wire feed speed from 3.8 mm/s to 5.6 mm/s; current from 90 A to 110 A; travel speed is fixed at 5.5 mm/s. The highest tensile strength of 562 Mpa is achieved with the heat input of 0.32 KJ/mm and wire feed speed of 3.8 mm/s. In addition, the best parameters via the Taguchi method were found. The parameters’ influence trends on the weld quality were also revealed.

Abstract: In the current energy landscape, efficiency is a critical topic. Therefore, even in the case of geared transmissions, it is essential to predict and calculate power losses as accurately as possible from the design phase. There are mainly three categories of losses in a gear unit: friction - the power losses due to the contact between teeth in rotation on the one hand and the seals with the spindles on the other hand, churning - the power losses generated by the air-lubricant mixture compression around teeth roots during rotation and windage - the power losses due to the teeth aerodynamic trail in the air-lubricant mixture. While the first two categories of losses are intensively studied in the literature, the papers focusing on windage power losses are less representative. Estimation of windage power losses can be done by numerical simulation, the accuracy of the results depending on the mesh density and the available computing power. The present study discusses the influence of meshing on the windage torque of an orthogonal face gear immersed in air and compares numerical results generated by SolidWorks Flow Simulation software with experimental data measured on a test rig.

Abstract: Additive manufacturing processes such as the material extrusion of metals (MEX/M) enable the production of complex and functional parts that are not feasible through traditional manufacturing methods. However, achieving high-quality MEX/M parts require significant experimental and financial investments for suitable parameter development. In response, this study explores the application of machine learning (ML) to predict the surface roughness and density in MEX/M components. The various models are trained with experimental data using input parameters such as layer thickness, print velocity, infill, overhang angle, and sinter profile enabling a precise predictions of surface roughness and density. The various ML models demonstrate an accuracy up to 97 % after training. In conclusion, this research showcases the potential of ML in enhancing the efficiency in control over component quality during the design phase, addressing challenges in metallic additive manufacturing, and facilitating exact control and optimization of the MEX/M process, especially for complex geometrical structures.

Abstract:

An optimal design methodology of Maxwell Coulomb friction damper is proposed for minimization of resonant vibration of dynamic structures. The simple Coulomb friction damper has the problem of zero or little damping effect to the vibration of spring-mass dynamic system at resonance. This problem does not exist in the case of Maxwell Coulomb friction damper which can be formed by combining a Coulomb friction damper with a spring element in series. However, the design and analysis of Maxwell Coulomb friction damper is more complicated and an optimal design methodology of such nonlinear damper is proposed in this article. The nonlinear equations of motion of the proposed damper is modelled and its hysteresis loop can be constructed by combining the four different cases of stick-slide motion. Its nonlinear equations of motion are solved numerically and the optimal values of friction and stiffness of the proposed damper is determined by using a Newton search method. Experimental validation of the optimal design of Maxwell Coulomb friction damper is carried out with a prototype of the proposed damper mounted on a linear slide block platform. Close correlation with its numerical predictions is observed in its contour plot of resonant vibration amplitude of the primary system. Damping performance of proposed damper is compared to viscous damper in seismic response design of adjacent single-storey buildings and also for damping turbine blade vibrations.

Abstract: Experiments and computational fluid dynamics (CFD) have been utilized to study the operating characteristics of a high performance single stage transonic axial compressor at both peak operating efficiency and at the onset of stall. A single path CFD simulation of the Transonic Compressor Rig (TCR) was created to model transonic operations at 85% rated speed and was validated against experimental data collected from the TCR in the same configuration. Detailed analysis of the CFD model identified the mechanism responsible for stall in this compressor and why simple slot and groove casing treatments were previously ineffective at extending stall margin.

Abstract: For a two-stage variable-pitch axial fan, a perforation design in first-stage rotor blades was proposed to improve aerodynamic performance and reduce acoustic noise. Utilizing steady-state simulations in Fluent, the internal flow characteristics of the fan before and after perforation were studied, and the changes in noise and vortex structure were ex-amined by the large eddy simulation. Additionally, the perforation diameter with better performance was applied to the second-stage rotor blades and both first- and sec-ond-stage rotor blades, and the effects of perforation on blades of different stages were compared. The results show that an appropriate perforation diameter can improve the performance of the fan. Considering the changes in total pressure rise and efficiency, d=6mm is the optimal choice. Proper perforation diameter has a significant effect on noise suppression, and the noise reduction effect is more pronounced in the high-frequency range. Among the models, d=10mm shows the best noise reduction effect. At this perforation diameter, the vortex at the trailing edge of the rotor blades forms a regular ring-like vortex chain, resulting in lower noise levels. Perforating in the first-stage rotor blade can enhance the fan's performance, while perforating in the second-stage rotor blades leads to a decrease in performance. Additionally, perforation can effectively reduce the noise at each stage. Considering both performance and noise variations, the optimal perforation scheme is simultaneous perforating in the first- and second-stage rotor blades with a perforation diameter of 10mm.

Abstract:

Arc welding is a complex multi-physics process, and its finite element simulation requires significant computational resources to determine temperature distributions in engineering problems accurately. Engineers and researchers aim to achieve reliable results from finite element analysis while minimizing computational costs. This research extensively studies the application of conventional ellipsoidal heat source formulation to obtain improved temperature distribution during arc welding for practical applications. Approximated ellipsoidal heat source model, which artificially modifies the coefficient of thermal conductivity in the welding pool area to simulate stirring effects, (Modified Ellipsoidal Model) is shown to be scientifically valid by comparing its results with those of Comsol's multi-physics arc welding models. The results show that, in comparison to the conventional ellipsoidal model, the temperature distributions obtained using the modified ellipsoidal model closely approach those from multi-physics simulations. In particular, the temperature history in the middle of the weld pool significantly changes and approaches the multiphysics solutions. Additionally, several points near the heat-affected zone were analyzed, and both ellipsoidal methods produced similar temperature histories until the metal melted. After melting, the modified ellipsoidal method gradually aligns more closely with the multiphysics solution. Additionally, both ellipsoidal methods produce similar temperature histories at points within the heat-affected zone.

Abstract:

This study focuses on how varying layer thickness by interlayer machining affects microstructure refinement, mechanical properties, and residual stresses of Wire Arc Additive Manufacturing (WAAM) components. It compares four types of WAAM samples: As built with uneven layer thickness without interlayer machining and uniform layer thicknesses of 2mm, 1.5mm, and 1mm achieved through interlayer machining. It reveals that the machining force reduces grain size and residual stress in WAAM components. Moreover, uniform and smaller layer thickness enhances inter-layer bonding, improving mechanical properties but increases the build time with more layers of deposition.

Abstract: A novel expandable wheel body assembly is designed in this paper. The wheel body assembly utilizes the elastic deformation of the hub clamp the bearing assembly. The gaps between them are effectively eliminated by this structure, improving the rotational precision and operational stability of the momentum wheel. A finite element model of the momentum wheel was established, and stress analysis was conducted under constant acceleration using finite element analysis software ANSYS. The results demonstrate that the designed momentum wheel meets the required strength specifications. Additionally, the random vibration characteristics of the momentum wheel in space environments were analyzed, and a random vibration test study was conducted. The results indicate that this new type of momentum wheel can work reliably in aerospace conditions.

Abstract:

The dynamic study of current and rapid movements of rigid and multibody mechanical systems, according to differential principles from dynamics, is based on advanced concepts from analytical mechanics: kinetic energy, higher-order acceleration energies and their absolute time derivatives. In advanced dynamics, the study will extend to higher-order acceleration energies. This paper, reflecting the authors’ research, presents new and revised formulations in advanced kinematics and dynamics, with a focus on acceleration energies of higher order. Explicit and matrix representations of the defining expressions for higher-order acceleration energies, relevant to the current and rapid movements of rigid bodies and multibody mechanical systems, will be presented. These formulations include higher-order absolute time derivatives of advanced concepts, following the specific equations from analytical dynamics. Based on authors’ findings, acceleration energies play a central, decisive role in formulating higher-order differential equations, which describe both rapid and transient motion behavior in rigid and multibody systems.

Abstract: This paper comprehensively reviews research on the buckling failure performance of curved shell structures. It covers various aspects, including industrial applications, the development of buckling theory and guidelines, common failure modes, and recent advancements in experimental and numerical analysis. The paper also discusses the role of imperfections in triggering buckling and outlines potential future research directions to enhance the design and safety of lightweight structures. The study identifies research directions and future tasks concerning curved shells by suggesting several areas (such as experimental, numerical, analytical, and control variables) that require further investigation and utilisation.

Abstract: This study investigates the influence of pressure pulse characteristics on the noise level generated by a swashplate axial piston pump. Axial piston pumps are widely used in hydraulic systems, but their inherent pulsating flow can lead to significant noise and vibration, affecting system performance and operator comfort. This research focuses on understanding the relationship between pressure pulses generated within the pump and the resulting airborne noise. Experiments were conducted by varying key pump operating parameters, such as rotation speed and discharge pressure, and measuring the pressure pulses at the pump outlet and the noise levels emitted.

Abstract: Recent findings have demonstrated that the desalination and purification of contaminated water, and the separation of ions and gases, besides solutions to other related issues, may all be achieved with the use of membranes based on artificial nanoporous materials. Before the expensive stages of production and experimental testing, the optimum size and form of membrane nanopores could be determined using computer-aided modeling. The notion that rectangular nanopores created in a multilayered hexagonal boron nitride (h-BN) membrane in a way that results in different inner lining atoms would exhibit unique property in terms of water penetration rate is put forth and examined in the current study. Nanopores in Boron nitride sheets can be generated with the inner lining of boron atoms (B-edged), nitrogen atoms (N-edged), or both boron and nitrogen atoms (BN-edged). In this study, we compared the three different inner-lined nanopores of boron nitride nanosheets to a comparable-sized graphene nanopore and evaluated the water conduction.

Abstract: Sediment-laden water significantly exacerbates cavitation damage in hydraulic machinery compared to clear water, underscoring the importance of investigating the effects of sediment on cavitation. This study examines cavitation in sediment-laden water using a Venturi flow channel and a high-speed camera system is utilized to capture the morphology and evolution of cavitation clouds. Natural river sand samples with a median diameter of 0.05, 0.07, and 0.09 mm are selected, and sediment-laden water with a concentration of 10, 30, and 50 g/L is prepared for the study. The results indicate that increasing sediment concentration or reducing sediment size intensifies cavitation, shortens the evolution cycle of cavitation clouds, and elevates the frequency of cavitation cloud shedding. Meanwhile, numerical simulation is conducted based on a gas-liquid-solid phase mixing model. The findings indicate that a higher sediment concentration corresponds to a greater shear effect near the wall, which raises the drag on the attached sheet-like cavitation clouds and enhances the re-entrant jet which can intensify the shedding of cavitation clouds. Furthermore, sediment particles contribute to more vortex: they enhance the impact on smooth, wall-adjacent sheet-like vortex, while simultaneously consuming more energy during the vortex return process, resulting in the creation of additional small-scale vortices.

Abstract: This study investigates the effect of incorporating an electromagnetic harvester inside the bluff body of a 2-DoF hybrid harvester in comparison to a standalone piezoelectric harvester for various external loads. The design consists of an electromagnetic harvester embedded inside a cylindrical bluff body, which is attached to the free end of a composite PZT cantilever beam. The harvester is excited through a vortex-induced vibration owing to the resultant wake vortices created behind the bluff body. The coupled equations of motion of the harvester are derived using the lumped-mass equivalent representation and Lagrange formulation. Numerical results show that at high operating flow speed and large electrical load, the standalone piezoelectric harvester outperforms the hybrid harvester. Nevertheless, for small electrical loads and at low-speed flow, the hybrid harvester outperforms the standalone ones for a wider range of the flow speed. In these operating conditions, numerical simulations also showed that an optimum spring stiffness of the electromagnetic harvester exists at a certain flow speed for a maximized harvested output power. In general, such hybrid energy harvester showed to be more effective at low-speed fluid flow and small electrical loads.

Abstract:

To investigate the performance of high-speed miniaturized screw refrigeration compressors, this study designed rotors with identical theoretical displacement but varying rated speeds. A normalized analysis established quantitative evaluation criteria for geometric performance, while an exergy analysis model assessed leakage exergy losses. Thermodynamic modeling evaluated the impact of different clearances and rated speeds on performance. The computational fluid dynamics (CFD) simulations analyzed gas forces and torque acting on the rotors. The study reveals that while tooth tip leakage represents the largest volumetric leakage in screw compressors, contact line leakage contributes most significantly to power losses. When the rated speed increases from 3000 rpm to 15000 rpm, contact line leakage remains the dominant source of power loss, with its relative contribution showing a marked increase. The rate of efficiency improvement with increasing speed follows a non-linear relationship, demonstrating diminishing returns at ultra-high speeds where further speed elevation provides negligible efficiency gains. For compressors with identical cylinder dimensions, reducing the number of lobes decreases discharge pressure fluctuations and power consumption. Larger wrap angles increase contact line length and discharge port area, reducing volumetric efficiency while creating a trade-off between leakage and discharge losses, resulting in an optimal wrap angle that maximizes adiabatic efficiency.