Micro-geometry Modification Research Articles

A population-based meta-heuristic approach for robust micro-geometry optimization of tooth profile in spur gears considering manufacturing uncertainties

The paper proposes a population-based meta-heuristic approach for the multi-objective robust optimization of tooth profiles, aimed at finding a set of micro-geometry modification parameters that allow to improve mechanical performance of spur gears. With the aim of making the optimization results reliable in real-life applications, a robust formulation of the optimization problem is generated by incorporating noise parameters that account for the influence of manufacturing uncertainties on the objective function. The described multi-objective gear optimization strategy is based on response surface (surrogate) models, allowing for checking the performance of a large number of candidate solutions in very short computational times. The computation efficiency of the proposed approach is the key that enables a simultaneous assessment of both linear and parabolic profile modifications, so that the most appropriate tooth geometry can be selected for the specific application. The proposed approach was successfully employed in a case study in which static transmission error and contact stress of a gear pair loaded by different torques were optimized under fatigue-related constraints and in presence of geometric variability due to manufacturing uncertainties.

Geometrical Structures of the Stepped Profile Bearing Surface of the Piston

The main node piston-pin-piston rings are most responsible for the formation of mechanical losses. It is advisable to reduce friction losses in the piston-cylinder group lead to an increase in the overall efficiency of the engine and thus reduce the fuel consumption. One way of achieving these objectives is modification of microgeometry of the piston bearing surface which cooperates with the cylinder wall. In this paper the results of simulation for the stepped microgeometry piston bearing surface are presented.

Optimum microgeometry modifications of herringbone gear by means of fitness predicted genetic algorithm

This paper presents a systematic methodology focused on herringbone gear microgeometry modifications toward vibration reduction. The dynamic model considering the unique characteristics of aviation herringbone gear is developed to study the vibration behavior. The optimal ease-off shape can be defined as the outcome of a multi-objective optimization process, the objective functions are loaded transmission error, meshing impact excitation and root mean square (RMS) of vibration acceleration. With special attention given to computational efficiency, a novel fitness predicted genetic algorithm is developed. An application to herringbone gear are presented, the results show the proposed method can obtain optimal modifications that significantly improve the gear performance over a wide range of operating conditions. Furthermore, the reduction of the vibration also leads to a reduction of bending stresses. Finally, a test on herringbone gear is executed under various combinations of torque and speed to demonstrate the accuracy of the proposed model.

Multi-objective micro-geometry optimization of gear tooth supported by response surface methodology

This paper shows the application of response surface methodology for gear optimization using micro-geometry profile modifications. The suitability of three distinct metamodeling techniques is studied in this paper: Gaussian Process (stochastic), Shepard k-Nearest (nonparametric deterministic) and Polynomial (parametric deterministic). The described optimization strategy is implemented and tested on a case study consisting of a pair of identical spur gears, in which the goal is to find optimal micro-geometry modifications of tooth profile, providing decreased values of peak-to-peak transmission error and maximal contact stress along the meshing cycle, while maintaining the safety coefficient linked to tooth bending fatigue above a required threshold. The gear pair is analyzed under three different loading scenarios. It is shown that the described optimization strategy allows finding optimal micro-geometry modifications of tooth profile that enable significant improvements in all the observed performance indices with respect to the unmodified gear design, as confirmed by detailed numerical simulations of the optimal gears.

Printing out the pores

Rock Mechanics The diversity of three-dimensional (3D) printing applications now includes fabricating porous rocks. The organization of pore space in rocks strongly influences their strength and fluid flow through them. Head and Vanorio constructed virtual 3D images of rocks by using x-ray tomography, which they followed with a series of pore microgeometry modifications and 3D printing of samples. Measurements of fluid flow through the samples brings deeper understanding to how processes such as mineral precipitation and compaction clog up the pore network. This technique helps reverse-engineer how rocks get their pore structure and offers a method for measuring flow properties through delicate samples. Geophys. Res. Lett. 10.1002/2016GL069334 (2016).

기어 전달오차 측정 장비의 설계에 관한 연구

Transmission error (TE) is the most important cause of gear noise and vibration because TEs affect the changes of the force and the speed of gears. TE is usually expressed as an angular deviation, or a linear deviation measured at the pitch point and calculated at successive positions of the pinion as it goes through the meshing cycle. Accurate measurement of TE for gear transmission will provide a reasonable basis for gear design, manufacturing processes and quality control. Therefore, in order to study the accuracy of the gear transmission, stability, TE, vibration and noise after gear micro-geometry modification, a gear transmission test rig is proposed in this paper, which is based on the existing technical conditions, by using reasonable testing methods, hardware and a signal processing method. All of the details and the experience can be taken into consideration in the next upgraded test rig.

스퍼기어의 전달오차에 관한 연구

Nowadays, lower gear vibration and noise are necessary for drivers in automotive gearbox, which means that transmission gearbox should be optimized to avoid noise annoyance and fatigue before quantity production. Transmission error (T.E.) is the excitation factor that affects the noise level known as gear whine, and is also the dominant source of noise in the gear transmission system. In this paper, the research background, the definition of T.E. and gear micro-modification were firstly presented, and then different transmission errors of loaded torques for the spur gear pair were studied and compared by a commercial software. It was determined that the optimum gear micro-modification could be applied to optimize the transmission error of the loaded gear pair. In the future, a transmission test rig which is introduced in this paper is about to be used to study the T.E. after gear micro-geometry modification. And finally, the optimized modification can be verified by B&K testing equipment in the semi-anechoic room later.

Specifics of Surface Micro-Geometry Modification under the Action of Temperature and Electric Field of Electrode Spots

The paper presents the results of experimental research on the possibilities of micro-geometry modification of conductible and semiconductor surfaces, that gives them new functional properties. It emphasizes that surface micro-geometry modification occurs in practically all cases of the action by concentrated sources of energy, but a prescribed geometry can be reached only under strict conditions. The process of this geometry formation is a function of the physical and mechanical properties and the chemical composition of the processed material, the gradient of applied energy, the intensity of electric field applied in the interstice between the workpiece and the tool-electrode, the connection mode of the workpiece (as anode or as cathode) in the discharge circuit of the current impulse generator, etc. It highlights the fact that on the processed surface can be formed spherical shaped craters, round asperities or Taylor cone shaped asperities. Depending on the shape and the size of asperities, the active surface area, and, respectfully, the emission and absorption properties of elementary particles and light radiation are modified.

The Results on Metal Surface Micro Geometry Modification by Applying Electric Discharges in Impulse

Abstract The experimental results aimed at modification of metal surface micro geometry by applying electric discharges in impulse are presented in this paper. Taylor cone-shaped asperities were extracted from the metal piece on the flat and cylindrical surface. SEM and EDX analysis of the processed surfaces were investigated

An approach for powertrain gear transmission error prediction using the non-linear finite element method

Research has established that gear transmission error (TE) is the predominant source of system excitation and via a complex transfer function produces noise in the powertrain system. Thus, reduction and control of TE will result in improved NVH performance. This paper will introduce an accurate method for estimating TE in powertrain transmission systems through an accurate gear contact analysis. To achieve high geometry accuracy, gear tooth geometry will be mathematically generated by using Python script interfacing with finite element analysis (FEA) software instead of importing from other computer aided design (CAD) packages. Real rolling and sliding contact simulations have been achieved by the latest nonlinear FEA techniques. High-quality meshes for contact surfaces have been obtained by advanced surface-based tie constraint techniques. An effective way to reduce TE is through gear microgeometry modification, i.e. crowning, tip relief, and lead correction. Gear micro-geometry modification will be mathematically achieved through Python script interfaced with finite element models.

Gear tooth contact analysis and its application in the reduction of fatigue wear

The present paper will concentrate on the gear fatigue wear reduction through micro-geometry modification method. An accurate non-linear finite element method will be employed to provide a quantitative understanding of gear tooth contact behaviour. Shaft misalignment and assembly deflection effects on the gear surface wear damage will be investigated as well. To achieve high accuracy of the gear geometry, the tooth profile will be mathematically generated though using Python script interfacing with the finite element analysis (FEA) software instead of importing from other computer aided design (CAD) packages. Real rolling and sliding contact simulations have been achieved through using the latest non-linear FEA techniques. An investigation has been carried out on automotive transmission gear surface failure due to shaft misalignment and assembly deformations. The solution for the wear is consequently proposed based on gear micro-geometry modification approach, i.e. tip relief, facewidth crowning and lead correction.

Updating fracture theory of wear

So-called adhesive wear is caused by microscopic fractures on sliding surfaces. An approach is described in which the wear process is broken down into several elemental processes, i.e. formation of real contact points, action of forces on real contact points, distribution of stresses and strains, accumulation of damage in the subsurface, initiation and propagation of cracks, removal of particles leading to wear and modification of microgeometry so as to form a feedback loop. This paper discusses updated theories on selected elemental processes.