Mechanics

Impact Analysis of the Key Engine Parameters on Piston Lubrication and Friction Performance in Diesel Engines Using GT-SUITE Program

Brahim MENACER — 2024-06-28

In Compression ignition engines combustion occurs at higher temperatures that leads to a rapid rise in combustion pressure and amount of heat released. This may lead to lesser emissions during engine cycle. Moreover, occurrence of combustion takes place for a very small crank angles duration resulting in better thermal efficiency. On the other hand, the oil used for lubrication in IC engines is responsible for a significant amount of pollution and particles emitted into the environment. In order to comply with increasingly strict pollution standards, manufacturers make considerable efforts to minimize the impact of oil consumption on engine emissions. The purpose of this study is to develop a one dimensional numerical simulation method using GT-Suite software to assess how the engine speed and load affect the oil film thickness, frictional force, and power losses during the operating engine cycle. The results obtained in this simulation were validated using experimental data, and there is good agreement between the numerical and experimental results. It was found in this paper that the maximum friction power losses were found to be 1.6 kW at middle of strokes and the minimum Oil film thickness was obtained in range of 9-38 μm.

An Unsteady Flow Control Technology Based on Vortex Injection for Centrifugal Compressor

Shuli HONG — 2024-06-28

The flow structures at the blade tip in a centrifugal compressor usually have an important impact on compressor performance, especially the TLV, which often plays a dominant role in its performance. In order to weaken TLV and improve compressor performance, an unsteady flow control method based on the concept of vortex injection is proposed. The numerical simulation shows that VID method can enlarge the stall margin of the compressor by 8.5%. Meanwhile, the total pressure ratio and efficiency of the compressor can be slightly improved from the design point to the stall point. The maximum efficiency increment and the maximum pressure ratio increment are 0.56% and 0.75%, respectively. A proof experiment on a micro centrifugal compressor shows that the VID can enlarge stall margin of 6.6% and the maximum relative pressure can increase by 2.6%. Therefore, both the simulation and experiment prove that the VID method is effective which utilizes both unsteady excitation and injection of negative circulation to weaken TLV. Finally, enhancing the efficiency of each unsteady jet/suction and separation flow interaction is highly recommended.

The Thermal Error Characteristic Analysis and Thermal Error Modeling Compensation of Aspheric Grinder

Bo YU — 2024-06-28

According to the literature analysis, the thermal error of CNC machine tools is the main factor affecting its processing accuracy, accounting for about 40% -70% ; This paper discusses the structure assembly of Aspherical Grinder, which is the research carrier of thermal error analysis of NC machine tool, and analyzes the characteristics and concrete forms of thermal error in aspherical grinder Based on the multi-input and single-output characteristics of the multi-linear regression model in the statistical theory, a multi-linear regression method is proposed to realize the thermal error modeling of aspheric grinder, the thermal error model of aspherical grinder is constructed based on matrix calculation, and the thermal error compensation system is designed in practice, the results show that the thermal error model of aspherical grinder based on the multiple linear regression theory can effectively compensate the thermal error of aspherical grinder and calculate the compensation data, the residual error after compensation has been reduced to 4.216E -002, greatly improving the aspheric surface grinder processing accuracy, making it meet the aspheric surface precision grinding processing needs.

Active Control for Transverse Vibration of the Marine Stern Shaft-Bearing System with LQR Strategy

Qianwen HUANG — 2024-06-28

The vibration control is essential to suppress am-plitude and improve efficiency for the marine stern shaft-bearing systems. An active controller for transverse vibra-tion is proposed by a combination of damping absorber and electromagnetic actuator with LQR strategy. The con-troller is designed with control methods, the parameters are defined based on the system and the disturbance input is obtained from experiments. The displacement of suspen-sion travel and soleplate deflection, as well as the velocity of shaft and bearing is investigated. The robustness is ana-lyzed with a pulse disturbance to study the maintenance of stability margins. The results demonstrated that the con-trolled behavior of the LQR strategy is preferable to that of the passive control. Moreover, the effect of damping ab-sorber is explored through results discussion with different damping coefficient. The control weighting matrix is proved to be significant for setting time, overshoot rate and reduction rate of the controlled behavior. A smaller damp-ing coefficient and control weighting matrix are demon-strated to be more satisfied for the control objectives. Therefore, the vibration reduction of the marine stern shaft-bearing systems can be achieved with the proposed LQR strategy.

Lie Group Variational Integrator for Multi-Body System with Rotation Coupling in Space

Long BAI — 2024-06-28

In multi-body system dynamics modeling, the body which rotate in space is complex and not easily to be expressed by Newton method, because the space rotation is realized by multi-joints rotation coupling with different direction. In this exploration, the Lie group variational integrator method is used to the dynamics modeling problem of multi-body system with three orthogonal direction joints coupling. Firstly, a mechanism accords with Cardan rotation regular is designed which can represent 3 different directions coupling, the kinematics model is derived out by matrix operation without triangle function. With inertia matrix and mass matrix of the multi-body system according to the topology structure, and the Lagrange function is built, and the dynamics equation is derived out with Lie group variational integrator method. With Legendre transformation, the Hamilton dynamics model is obtained. The differential computation of the momentum part is avoided, the scale of the dynamics model is greatly reduced. The Hamilton dynamics model with two different kinematics part are compared in simulation. The simulation results indicates that the different kinematic expression can lead to different structure conservation characters under same numerical computation method. This exploration offers a benefit attempt of using geometry method to dynamics modeling problem of tree structure multi-body system with different structure rotation matrixes coupling.

Biomechanical Study of the Wing of the Dragonfly Aeshna Cyanea

Kamilė Gabrielė ZURLYTĖ — 2024-06-28

Aeshna Cyanea is a species of dragonfly in the Aesnidea family. In this study, morphology and mechanical properties of dragonfly were investigated. The location of the nodus on the wing was observed. A SEM study was also carried out to get a closer look at the mechanical structure of the dragonfly wing. A dynamic study of the wing was carried out to and the first resonant frequency of the wing was found. Future research will cover dragonfly wing mathematical model and simulation of the wing dynamics.

Simulation Study On Energy Recovery and Reuse of Hybrid Loader Actuator

Lili ZHANG — 2024-06-28

It is necessary to reduce engine fuel consumption for loaders to overcome the energy crisis faced by today's society. To this end, a hybrid loader arm energy recovery and reuse system is proposed, adding an electrical energy recovery and reuse system to the conventional loader arm system and effectively reducing the loader engine fuel consumption and emissions. The principle of the system is analyzed, the mathematical model of the system components is analyzed, and AMESim models the system. The simulation results show that the system does not affect the regular motion characteristics of the boom arm cylinders. The energy recovery efficiency of the system reaches 58.9 %, and the energy reuse efficiency reaches 86.9 % after four operation cycles. The system can recover energy in hybrid, pure engine, and motor modes. The system's engine provides 24.8 % less energy, engine fuel consumption is reduced by 24.9 %, and pollutant emissions CO, HC, and NOx are reduced by 19.2 %, 25.9 %, and 23.6 %, respectively. The system provides a reference for the research of energy-saving technology for loaders.

Investigation of Dynamics of the Manipulator with Self-Stopping Mechanism and Vibration Drive Based on Centrifugal Forces

Kazimieras RAGULSKIS — 2024-06-28

Manipulators of this type can be used as constituent parts of robots of several dimensions. Vibration drive based on centrifugal forces is often used in elements of manipulators and robots. In this paper manipulator with vibration drive based on centrifugal forces and with the self-stopping mechanism is investigated. The model of the investigated manipulator is described and equations determining the motion of the manipulator are obtained. The conservative system is investigated. Then the full dynamic model is investigated. Also, the model with excitation of unlimited power is investigated. Numerical solution of the obtained equations is performed. First the results for the conservative system are described and investigated. Then the full dynamic model is investigated in detail. Also, the model with excitation of unlimited power is described and investigated. Various typical graphical relationships determining the dynamic behavior of the investigated manipulator with vibration drive based on centrifugal forces in steady state regimes of motion are presented. Experimental investigations are performed. The obtained results are used in the process of design of manipulators with vibration drive based on centrifugal forces.

Multiaxial Fatigue Criterion Using Total Strain Energy Parameters Associated with Cumulative Damage Model

Abdelghani BALTACH — 2024-06-28

The Knowledge of the causes of damage of materials is a priority for design engineers to avoid sudden failure of equipment in service. One of the most important reasons for the failure of materials is fatigue, this phenomenon can be defined as damage to the metal under repeated stress and lower than the yield stress. The main objective of this study is the development of multiaxial fatigue criterion using total strain energy, then validating this proposal by the results of literature and a comparison with another criterion. The majority of the results obtained by our proposal give conservative results. These predicted results are compared with bending-torsion tests and the agreement is found to be fairly good.

Adaptability of Burgers Rheological Model and its Improved Model to the Creep Properties of Glue Laminated Bamboo

Ke DING — 2024-06-28

The proportion of bamboo material used in industrial production has increased year by year. The glue laminated bamboo (GLB) is a kind of bamboo engineering material. GLB can be used in modern buildings, bridges, furniture and other fields. It is necessary to study its mechanical properties, especially its creep properties. In the paper, the short-term creep performance of GLB is studied at four stress levels. At first, the Burgers rheological model (BRM) and the improved Burgers rheological model (IBRM) are used to study the creep properties of GLB. The parameters of the two models are obtained by fitting the experimental data. The results show that BRM is only suitable for the elastic deformation part of the GLB material. But the nonlinear viscosity coefficient is introduced into IBRM, so it can better describe the creep characteristics of GLB. On this basis, IBRM and BRM are used to predict the long-term creep performance of GLB based on the obtained creep parameters. The results show that the prediction error of BRM is large, and the prediction result of IBRM is in good agreement with the experimental data. It shows that IBRM is more suitable to describe the creep characteristics of GLB.

Fatigue Life Assessment of Cruciform Welded Joints Based on Interval Dissipation Energy Method

Liuping WANG — 2024-06-28

In order to take uncertain factors of welding process into account, a dissipated energy-based interval fatigue life estimation approach is presented in this paper. The infrared thermography fatigue life tests are conducted on the specimens of butt welded joints and cruciform welded joints. Then, the dissipated energy-based interval fatigue life prediction model is built, while interval fatigue parameters are determined and interval curve of asymptotic dissipated energy and fatigue life is obtained. The lifetime assessment of cruciform welded joints based on the suggested model is performed, and the predicted results agree well with the experimental data.

Finite Element Analysis of Laser Ablation Damage and Buckling Mode of Axially Compressed CFRP Cylindrical Shell

Guang YANG — 2024-06-28

Laser ablation damage has an important impact on the load-bearing capacity of the structure. This paper first uses ABAQUS ALE adaptive grid technology to establish and verify the numerical simulation analysis method of laser irradiation ablation of CFRP laminates. Then a finite element simulation analysis was conducted on the buckling process of the CFRP cylindrical shell under the combined loading conditions of laser irradiation and axial compression, and the critical buckling load and buckling mode of the cylindrical shell under different conditions were obtained. The effects of ablation damage and laser irradiation position on the critical buckling load are discussed. When the laser irradiation position is between the end and the midpoint of the axis in the axial direction of the cylindrical, and is farthest from the axis in the radial direction, buckling failure is prone to occur.