Mechanics

Research on the Lightweight Drive Axle Housing of Electric Farm Management Machine

Tong ZHANG — 2024-12-21

The paper shows that the drive axle housing of the electric farm management machine not only has the role of carrying and transmitting power, but also plays a supporting role for the main reducer, brake and other components, which needs to meet the requirements of stiffness and strength. Three-dimensional modeling and finite element analysis are used to design the joint, and a reasonable three-dimensional modeling of the drive axle housing is carried out. Aiming at the structural quality of the axle housing, the finite element analysis method is used to reduce the quality of the axle housing. Firstly, the force analysis is carried out according to the maximum vertical force condition of the drive axle housing. Secondly, the static and dynamic characteristics of the axle housing structure are analyzed. Then, with the parameters that have great influence on the quality as the design variables, the quality of the axle housing as the optimization objective, and the maximum static stress and maximum deformation as the constraint conditions, the Latin hypercube experimental design method and genetic optimization algorithm are used to carry out the lightweight design of the axle housing. Finally, through the optimization scheme, the total weight of the axle housing using structural steel is reduced from 169.4kg to 156.83kg, achieving a weight reduction effect of 7.42%, and realizing the lightweight of the axle housing.

Ultrasonic Fatigue Testing Machine Based on Resonance Principle

Yuhang WU — 2024-12-21

With the continuous improvement of reliability and life index of modern equipment, researchers and research institutions pay more and more attention to the problem of ultra-high cycle fatigue of metallic materials. Ultrasonic fatigue testing is the most effective and commonly used method to test ultra high cycle fatigue of metallic materials. It is an accelerated fatigue test method based on the principle of resonance. The typical test frequency is 20 kHz, which has an obvious time advantage and can greatly save the time cost and economic cost of fatigue testing. In this paper, based on the key technical requirements of the ultra-high cycle fatigue test, the design of the ultrasonic fatigue test machine is carried out by using the method of theoretical research and numerical simulation, focusing on key components such as ultrasonic transducer, signal generator, horn and so on. It can realize ultra-high cycle fatigue performance testing with low stress amplitude and high frequency, and complete the test in a short time.

Flows Characteristics of Two Immiscible Swirling Fluids in a Cylinder

Kenza BRAHMA — 2024-12-21

Flows of an oil-glycerin system of immiscible Newtonian fluids, driven by the independent rotation of the boundaries of a vertical cylinder with axial rod are investigated numerically. Moderate lid rotation rates are shown to generate breakdown in the adjacent oil phase, associated to significant interface displacement and flow reversal. The vortex pattern and interface behavior are found to be very sensitive to the distinct and combined effects of fluids volume fraction and background rotation. In particular, a decrease of the oil phase volume causes bubble expansion and evolution into a ring type vortex prior to its suppression as it coalesces onto a convex shaped interface. In addition, the vortex structure may efficiently be prevented (enhanced) by means of low rates of sidewall counter-rotation (co-rotation). Moreover, addition of swirl by means of the central rod rotation is found to have a considerable impact on the lid driven vortex flows characteristics in qualitative accord with prior experiments.

Keywords: immiscible fluids, cylinder, central rod, rotating walls, breakdown, interface behaviour.

Effect of Manta Ray's Flexible Hydrofoil Kinematic Parameters on Autonomous Propulsion Efficiency

Hao DING — 2024-12-21

Marine organisms have evolved various locomotion methods over millions of years to adapt to aquatic environments. Manta rays, with their pectoral fins and flexible hydrofoil propulsion, inspire advancements in underwater propulsion systems. In this study, an overlapping grid was used to create a simplified model based on the pectoral fins of a manta ray. The oscillatory traveling wave equation is programmed and loaded on the pectoral fin model to characterize the motion state of the manta ray cross-section. It explored how wavelength and frequency affect the efficiency of flexible hydrofoil swimming. Results showed that flexible hydrofoils create reverse Kármán vortex streets during autonomous swimming. The size of these vortices, along with frequency and wavelength, impacts propulsive efficiency. When frequency is fixed, increasing wavelength increases turbulence, reducing efficiency but slightly boosting speed. Conversely, fixing wavelength and increasing frequency improves stability, enhancing efficiency and speed. This research offers new insights for designing biomimetic underwater propulsion systems in marine engineering.

Optimization of Restrictor Parameters and Static Characteristics Study on Orifice Type Hydrostatic Thrust Bearing

Yuanlong CHEN — 2024-12-21

Gas bearings play a crucial role in maintaining the precision of ultra-precision machine tools. However, the bearing capacity is inferior to that of rolling bearings. The bearing capacity of gas bearings is directly influenced by restrictor structural parameters. To clarify the combined effect of restrictor structural parameters on the static bearing capacity of gas bearings and enhance the bearing capacity. The orthogonal test method was used to investigate the impact of various combinations of parameter levels (e.g. diameter of orifices d₁, thickness of gas film h₁, diameter d₂ of pressure-equalizing groove (PEG), and PEG depth h₂ on the static load carrying capacity of the bearings). The load-carrying capacity (LCC) and mass flow rate (MFR) were selected as the experimental indicators. Results showed that gas film thickness, orifice diameter, PEG diameter and PEG depth dominated LCC. Additionally, it was observed that diameter of orifices has the most significant impact on MFR, followed by thickness of gas film, PEG diameter, and PEG depth having the smallest influence on MFR. LCC serves as a critical manifestation of the static bearing capacity of bearings. However, this increase in LCC unavoidably resulted in higher gas consumption, leading to an elevated MFR. Consequently, the structural parameters of restrictor were optimized based on the principle of optimal LCC, while also ensuring that there was no significant rise in MFR. The optimized parameter combinations were thickness of gas film h₁=0.01 mm, diameter of orifices d₁=0.25 mm, PEG diameter d₂=5 mm, and PEG depth h₂=0.07 mm. This study can contribute to a profound understanding of the nonlinear dynamic mechanism and structural optimization design application of air bearing.

Enhancing Terrain Adaptability of Micro Tracked Chassis: A Structural Design and Performance Evaluation

Chang SU — 2024-12-21

Mobile robots operating in complex terrains require superior traversability and adaptability. This study addresses this challenge by proposing a novel micro-tracked chassis design with enhanced adaptive terrain capabilities. The design leverages track chassis as the bearing mechanism and optimizes its structure for improved performance. A combined approach of theoretical analysis (e.g., mechanics calculations) and RecurDyn software simulations is employed to evaluate the chassis's ability to traverse various obstacles, including longitudinal and transverse slopes, trenches, and vertical barriers. The analysis reveals key performance parameters, demonstrating a maximum climbing angle of 35°, a maximum side slope of 30°, a maximum trench crossing width of 400 mm, and a maximum surmountable vertical obstacle height of 150 mm. Furthermore, simulations on different soil types (sand, clay, and heavy clay) show superior passability on sandy terrain. Additionally, a forward and downward center of mass configuration enhances obstacle crossing performance and driving stability. This research provides valuable insights and a theoretical foundation for the design of micro tracked chassis with exceptional off-road capabilities.

Optimization of Tensile Strength in AA6063 Friction Stir Welds using ANOVA and ANFIS: A Statistical Analysis of Process Parameters

Deepika MISHRA — 2024-12-21

The tensile strength of 12 mm thick joints created by friction stir welding (FSW) on AA6063 was taken into account through statistical optimization of process parameters based on experimental research. The process variables including the spindle speed, the tool pin length, and the tool pin shoulder rise determine how well this friction stir welding type welds. Experiments were conducted as per full factorial and L9 orthogonal array. By using ANOVA (analysis of variance) the effect of parameters and its significance were examined on the tensile strength. The multiple variable regression equation and ANFIS (artificial neuro fuzzy inference system) based mathematical model were used to determine the optimized tensile strength value with the percent error of 23.27% and 6.04% respectively. As evident from the results the tool pin length has the higher impact with percentage contribution ratio (PCR) of 79.65.

Calculation Method of Complete Dynamic Characteristics Coefficients for Tilting Pad Bearings Based on Equivalent Motion of Babbitt Pads

Xiaoming SONG — 2024-12-21

As energy equipment advances towards higher speeds and greater capacities, the issue of instability in tilting pad bearings has correspondingly grown more pronounced. The method of eight-coefficients dynamic characteristics of the tilting pad bearing expose many shortcomings. This paper introduces the geometric interplay between the tilting pad bearing and journal movement, advancing a novel method for calculating the comprehensive characteristic coefficients of the bearing, grounded in the concept of tile motion equivalence. According to the geometric relationship between tilting pad bearing and journal movement, the coordinate system of the tilting pad bearing pad performance is established. The motion of the pad is equivalent to the movement of the journal to solve the complete characteristic coefficient, and the relationship between the complete kinetic coefficients is deduced. In contrast to the tile perturbation approach, our method alleviates the complexities associated with determining the complete characteristic coefficients, streamlines the computational workflow, boasts high efficiency and reliability, and is more readily embraced and comprehended by engineering professionals. It provides the support for the calculation of the tilting pad bearing-rotor system stability.

Dynamic Modelling and Analysis of a new Design Variable Inertia Flywheel for Diesel Engine using Bond Graph Technique

Prabhat R. MAHTO — 2024-12-21

The work proposed a new methodology to obtain variable inertia that reduces the speed fluctuations of the diesel engine during sudden load variations in terms of a variable inertia flywheel (VI_F). In the proposed VI_F, the inertia variation technique is based on the slider mass movement supported by the springs. The sliders of the VI_F travel outward or inward according to the speed increase or decrease of the diesel engine, and hence, it produces variable inertia. It helps to reduce sudden speed fluctuations by adjusting the inertia before adjusting the fuel supply to the diesel engine. A dynamic model of the VI_F with a diesel engine is developed using the bond graph technique and simulated in SYMBOLS SHAKTI software. Moreover, the simulation responses of the VI_F with a diesel engine are compared with the same diesel engine when a fixed inertia flywheel (FI_F) is attached to it. The simulation results show that the inertia of the flywheel can be varied from 0.48 kg/m⁴ to 0.57 kg/m², and speed fluctuations of the diesel engine can be reduced when a VI_F is attached to it instead of a FI_F. Moreover, it is found that the viscous friction resistance (C_F) and spring stiffness of the VI_F (k_s) effect the system performance significantly and another parameter i.e. sliding friction resistance (R_sfrtn) does not effect the system performance.

Simulation and Analysis of the Crankshaft System of the High-Power Marine Engine

Yang XIAO — 2024-12-21

The crankshaft is one of the most important parts of the engine and is likened to the "backbone" of the engine. In this paper, NL9340 high power diesel engine crankshaft system as the research object, the finite element free mode simulation model of crankshaft was established, and the inherent frequency and vibration mode of crankshaft were calculated. Through the rigid-flexible coupling finite element simulation of the crankshaft system, the dynamic and kinematic characteristics of the crankshaft system were analyzed. It was calculated that the load spectrum of each cylinder connecting rod journal and piston pin mainly fluctuated in the range of 20000 kN, in which the maximum exciting forces of the first connecting rod journal and the second connecting rod journal are above 30000 kN. On this basis, the static strength of the crankshaft was simulated and analyzed. The results show that the stress is the greatest and most concentrated at the over-rounded corner between connecting rod journal and crank. The maximum equivalent stress and deformation occur at the second cylinder connecting rod journal, which are 14.103 MPa and 8.3683 e^-3mm respectively.