Influence of Different Modified Gears on the Vibration and Noise of Electric Vehicle Reducer

The tooth profile crowning modification was applied onto paired gears for reducing the noise of an electric vehicle reducer. The simulated gear contact spots are compared before and after modification, and are validated by a contact spot experiment. Based on the rigid-flexible coupling model of the gear transmission system, the time-varying meshing stiffness, time-varying meshing force, and the vibration and noise of the gear pairs with different modified gears obtained by simulating calculation are analyzed. The results showed that the selection of modified gear has a great influence on the modification effect. In the way of tooth profile crowning, it is not advisable to modify the pinion independently, as it may increase the frequency and degree of meshing impact between the helical gear pair, making the transmission become less smooth; while modifying the wheel and pinion at the same time can effectively reduce the time-varying meshing stiffness and force, and the vibration and noise. Also, the optimized gear modification scheme is verified by the noise test.

Analysis of the influence of design parameters on the agro-ecological qualities of tractor tires

Experimental studies of the impact of agricultural mobile machinery movers on the soil are seasonal in nature and require complex experimental equipment. The complexity of the physical processes occurring in the elastic wheel-ground system requires the introduction of many assumptions and limitations that reduce the accuracy of the results, according to the design of simulation models performed in the software environment. The aim of the research was to study the influence of the design parameters of the tire on the efficiency of the normal deflection along the contact spot zone X. Studies have shown that 65% to 77% of the normal deflection of the tire is used when passing the contact spot. The reinforcement parameters of the tire frame have the greatest impact on the efficiency of the normal deflection along the contact spot zone. With an increase in the number of layers of the frame cord from 2 to 8, the coefficient of usability of the normal deviation for the stroke of the contact spot decreases from 0.761 to 0.689, with an increase in the angle of inclination of the frame cords - decreases from 0.755 to 0.693.

Wheel drive with integrated differential

The performance indicators of wheeled arable machine-tractor units, which are accelerated on the working gear, depend on the operating modes of the wheels during this period. When the wheel is skidding, soil lumps break down in the contact spot, the soil structure is destroyed. Based on the system analysis of the wheels operation, the method of their improvement is justified by continuous control of the eccentric point of application of the driving torque and external load. As a result of the analysis for the first time, a soil-sparing wheel mover with the properties of a differential, a tangential force regulator and clearance regulator was developed. In the case of an eccentric application of a vertical load and a longitudinal pushing force, one of the satellites of the wheeled planetary gearbox is the leading and bearing one. The purpose of the article is to analyze the factors influencing the automatic adaptation of the wheel drive to changing operating conditions. It is established the relationship between the driving moment and the rolling resistance moment, the moments of inertia of the wheel and the drive gear of the integrated differential.

Erosion potential of ultrasonic food processing

Introduction. Cavitation is the most significant factor that affects liquid food products during ultrasound treatment. Ultrasonic treatment intensifies diffusion, dissolution, and chemical interactions. However, no physical model has yet been developed to unambiguously define the interaction between ultrasonic cavities and structural particles of liquid food media. Physical models used to describe ultrasonic interactions in liquid food media are diverse and, sometimes, contradictory. The research objective was to study ultrasonic devices in order to improve their operating modes and increase reliability. Study objects and methods. The present research featured ultrasonic field generated in water by the cylindrical emitter, the intensity of flexural ultrasonic waves and their damping rate at various distances from the emitter. Results and discussion. The paper offers a review of available publications on the theory of acoustic cavitation in various media. The experimental studies featured the distribution of cavities in the ultrasound field of rod vibrating systems in water. The research revealed the erosion capacity of ultrasonic waves generated by the cylindrical emitter. The article also contains a theoretical analysis of the cavitation damage to aluminum foil in water and the erosive effect of cavitation on highly rigid materials of ultrasonic vibration systems. The obtained results were illustrated by semi-graphical dependences. Conclusion. The present research made it possible to assess the energy capabilities of cavities generated by ultrasonic field at different distances from the ultrasonic emitter. The size of the contact spot and the penetration depth can serve as a criterion for the erosion of the surface of the ultrasonic emitter.

Modeling of Frictional Stick-Slip of Contact Interfaces Considering Normal Fractal Contact

In this paper, a physics-based approach is proposed to represent the tangential frictional stick-slip behaviors of contact interfaces in mechanical systems. The modeling idea of the discrete Iwan model is adopted, where the yield forces of Jenkins elements are determined by considering the surface fractal feature and normal loading conditions. Initially, surrogate asperities are defined to express the fractal features of the contact surface topography, and Jenkins elements are used to describe the tangential stick-slip motions between surrogate contact asperities. Then, a geometric series distribution principle of the normal loads at contact asperities is proposed to determine the yield forces of the Jenkins elements. The criterion for identifying the micro- and macro-slips of the contact interfaces is proposed, which are determined by the stick and slip conditions of the largest contact spot. An experimental setup for measuring frictional stick-slip of contact interfaces was constructed, upon which tangential quasi-static experiments were conducted. Satisfactory agreements between the theoretical and experimental results indicates that the proposed modeling approach can perfectly predict the stick-slip behavior of the contact interfaces. Finally, mechanical characteristics of the contact interfaces were investigated in detail by employing the validated modeling approach. Owing to the definite physical significance of the proposed modeling approach, the mechanism of the tangential stick-slip behavior of contact interfaces is partially demonstrated.

Simulation and experimental investigation of contact spot temperature for electrical contact components

The contact spot temperature of electrical contact components substantially affects the reliability and electrical life of any electrical connections within the electrical engineering. In this paper, finite element model of typical spring structure components is built by using COMSOL Multiphysics software. Furthermore, the transient process of contact temperature is simulated by taking account of film resistance on the contact surface. Moreover, a test rig is introduced that makes it possible to measure the electrical contact resistance and temperature within the electrical contact components simultaneously. Finally, correlation between contact resistance and contact spot temperature with different contact force and current levels are investigated explicitly.

Development of a device for determining the coefficient of adhesion of a tire simulator with a flat support surface

To ensure optimal braking performance, i.e. minimum braking distance while maintaining the stability of the car at the limit of controllability, anti-lock systems are currently installed on cars. The relative fraction of the rest friction in the contact spot, which is used to form the longitudinal reaction of the support surface at the appropriate value of the slip coefficient, in relation to the total fraction of the rest friction in the contact spot is a constant value for any type and condition of the road surface. The coefficient of adhesion in physical essence is the coefficient of friction at rest. The proposed device for determining the coefficient of adhesion of a tire simulator with a flat horizontal support surface will simplify the design and increase the measurement accuracy. Keywords: coefficient of adhesion, a device for determining the coefficient of adhesion, a device

Snow Temperature Behind Sliding Skis as an Indicator for Frictional Meltwater

For many years, a frictional meltwater film has been assumed to be the reason for the low friction between skis and snow, but experimental studies have been inconclusive. Therefore, the aim of our study was to find indications or evidence for the presence of frictional meltwater. The friction between snow at −4°C and an XC ski as well as a flat ski was measured on a large-scale linear snow tribometer at realistic skiing speeds from 5 to 25 m/s. We used an infrared camera to analyze the snow temperature behind the skis. From the maximum snow surface temperature, we estimated the temperature at the spots where ski and snow contacted. Assuming that the contact spot temperature does not notably exceed 0°C, we calculated the relative contact area between ski and snow. Maximum snow surface temperatures were very close to 0°C. Given that not the entire snow surface is in contact with the ski, this finding is a strong indication for snow melting. Heat flow considerations led to the conclusion that there must be energy dissipation beyond the heat flow into ski and snow. The most obvious mechanism for the additional energy dissipation is snow melting. Presuming that the contact spot temperatures are at most slightly above 0°C, we calculated relative contact areas of 21–98%. Previous research has reported much lower values; however, most studies were conducted under conditions that are not realistic for skiing.

Basic Theory and Design Method of Variable Shaft Angle Line Gear Mechanism

In this paper, a novel line gear mechanism is proposed; it is called the variable shaft angle line gear mechanism (VSALGM). VSALGM has two rotational degrees of freedom, one is the rotation of the two gears with a constant transmission ratio, and the other is the relative swing of the two gears shafts. First, a novel contact model of VSALGM composed of one driven contact curve and one driving line teeth working surface (DLTWS) was proposed. With the concept, the basic design equations for VSALGM were derived on the basis of the space curve meshing theory of line gear. Moreover, the design criterion of pressure angle for VSALGM was analysed and proposed on the basis of the contact model. A basic design method for VSALGM was thus developed. A design example was given, and prototypes were manufactured using three-dimensional (3D) printing. Kinematic experiments and gear contact spot testing were carried out on a self-made kinematic test rig by the prototypes. The results show that the VSALGM designed in this paper can achieve a continuous, smooth and stable meshing transmission while the shaft angle is continuously changed within its setting range.

Research on the centre distance separability of parallel shaft line gear pair

For gear pairs with centre-distance separability, transmission ratios are not affected by centre distance error. Based on space curve meshing theory, the centre distance separability of a line gear pair was studied. A novel line gear pair called the separable and pure rolling parallel shaft line gear pair (SPRPSLG) was proposed, which has centre-distance separability characteristics and pure rolling transmission. The basic design theory of the SPRPSLG pair was established. A design method of the SPRPSLG pair with an eccentric arc tooth profile was given. An SPRPSLG pair example was designed and manufactured using the form milling method. Kinematic experiments and meshing efficiency experiments were conducted. Gear contact spot testing and gear contact simulation analysis were carried out. The SPRPSLG pair was shown to have centre distance separability, which provides a further theoretical basis for the popularization and application of line gears.