Gear Form Research Articles

Fault Diagnosis Platform Development Based on Wavelet Transform for Wind Turbines Transmission System

Wind turbine transmission system with complex structure and abundant fault features, also the fault features are variable, three typical fault and failure forms of rolling bearings, shafts and gears in wind turbine drive train were analyzed, also the failure mechanism and corresponding vibration signal characteristics was proposed. In the wind turbines transmission system, the vibration signal can reflect most of the fault information, as there was non-stationary signals in the vibration signals and wavelet transform for feature extraction was proposed. The whole framework of the fault diagnosis platform was constructed, the lower machine based on the measurement unit and the PC based host computer diagnosis system was designed, the diagnosis system was powerful and easily cut, which was strong help to the fault character extraction, also it was practical and available for wind turbine fault diagnosis.

Strength and Stiffness Optimization of Heavy-Duty Gear

In this paper, a kind of advanced gear body form is proposed, which has the structure characteristics of no weight reducing whole, thin spoke platesthick rim and large fillet. The optimization effect is confirmated by comparative analyzing the structure before and after optimization on strengthstiffnessweight and frequency adjustment performance of gear. The results show that the kind of optimization gear body is suitable for application in aviation, for which has the features of high strengthgood stiffness and light weight and which is easy to adjust gear frequency.

Characteristic Value Extraction of Gear Defect based on Image Processing

Aiming at pitting of gear failure forms and attrition, this paper uses image processing software of MATLAB and the research image extractive technique of image character. Based on the two different image expressions of defect forms, this paper abstract defect area ratio as well as the characteristic value and abstract contrast with gray co-occurrence matrix as image characteristics. In order to verify the abstracted image characteristic for evaluating pitting and wearing effectiveness, we use the neighboring method to construct a recognition model, and analyze the collected image samples. The result is correct, but the recognition accuracy needs to be improved. At last, eccentricity ratio and circularity is abstracted as the characteristic value based on image morphological characteristics.

Effects of Wheel Dressing Errors on the Accuracy of CNC Gear Form Grinding

Gear form grinding is a finish machining method for hard tooth surface with a form wheel. Wheel dressing is an important process in gear form grinding, and affects the precision of the ground gear directly. Based on the envelope theory the mathematical model of the dressed wheel surface was built in the case of wheel dressing errors. Then the real profile of the ground tooth in the transverse plan was solved and its deviations from the designed profile were evaluated. Finally the effects of each dressing error on the precision of the ground gear were analyzed using the proposed mathematical model. The results provided theoretical foundation for the precision control during manufacturing a gear form grinding machine. A grinding experiment was implemented using the gear form grinding machine and the ground gear was measured by a three-coordinate measuring machine. The measure result indicated that the accuracy grade of the ground gear achieved 4 (ISO1328-1: 1997).

Study on Influencing Factors of Tooth Forming Quality for Gear Shaft with Cross Wedge Rolling

The feature of the gear shaft with Cross wedge rolling technology is high efficiency, low material loss and higher strength of the gear shaft forming. A research model of cross wedge rolling plastic forming adopting tri-dimensional thermal elastic-plastic finite element method is put forward. Forming mold divided into two parts as the wedge-shaped molds and tooth mold is designed. Depending on orthogonal test program, applying Deform-3D to numerical simulate for the gear shaft with cross wedge rolling, the influence of temperature, number of teeth, module and feet rate for gear shaft tooth forming quality is studied. The results are analyzed with the temperature of the workpiece, number of teeth, module and feet rate of the die movement during CWR and the best combination of produce conditions is reached.

Virtual Assembly and Kinematic Simulation of Gear Form Grinding Machine Based on Pro/E

On the basis of establishing 3D modeling of gear form grinding machine, all levels of subassemblies of the grinding machine were assembled. Then the virtual assembly of total grinding machine was completed. Based on the kinematic simulation module of Pro/EMechanism, and combined with the virtual machine assembly model, the simulation analysis on machine movement was carried out. By simulating the actual working situation of the model, it could be checked whether the location, movement and load of the product could meet actual requirements before manufacturing the physical prototype of the product. This method is helpful for improving one-time success rate of new product development and saving product development cost.

Calculation and Analysis of Gears in MW Wind Turbine Gearbox

Gearbox was a key component of wind turbine but with the highest failure rate, so it was necessary to analyze its safety and reliability. In this paper, gears in MW wind turbine gearbox were analyzed by nonlinear finite element contact analysis method. The changing regularity of the stress was found as tooth mesh, and it was proved to be reliable by comparing with the result of theoretical calculations. The maximum contact stress existed on the second engaged tooth as well as the vicinity of the pitch circle of gears. The stress concentration phenomena occurred at the tooth root fillet which caused the main failure form of gears.

Dynamics Behaviors Analysis on the Column of Gear Grinding Machine

Aiming at the issue on the development of gear form grinding machine, a method for analyzing the dynamic behaviors of the machine column was introduced. Based on the model of gear grinding machine developed before, a suitable finite element model of the column was established firstly. Modal analysis on the column was carried out by means of ANSYS software, and the first five natural frequencies and vibration modes of the column were obtained. According to the analysis results, some improvements on the original column structure were made. By comparing the static and dynamic behaviors of several different rib structures presented, the best column structure is selected. This method offers theoretical basis for the structural improvement of gear grinding machine.

The influence of manufacturing method on the running-in of gears

Striving for higher gear transmission efficiency by using a low-viscosity transmission lubricant affects the lubricant film thickness. To keep the Λ-ratio (the ratio between the film thickness and the surface roughness) intact, more effort must be put on the surface topography. This paper presents a study of how running-in affects the dry elastic contact area ratio in spur gears using real surface topographies from three common manufacturing methods (green-shaving, honing, and grinding). The test gears were manufactured in case-hardened steel, similar to 20MnCrS5. Surface topography measurements were used as input to a contact analysis boundary element software program. An important hypothesis used in this work is that the dry elastic contact area ratio, i.e. the ratio between real and nominal contact area, can be used as a measure of the contact conditions in gears. It is concluded that running-in differs significantly for the studied manufacturing methods and that the dry elastic contact area ratio gives a consistent description of these changes. The shaved gears have the highest dry elastic contact area ratio after running in, where the ground gears have the lowest dry elastic contact area ratio. The increase in dry elastic contact area ratio is about 30 per cent for the shaved gears, 12 per cent for the honed gears and less than 5 per cent for the ground gears. Extreme value parameters, such as Rp and Rz, showed relatively good correlation to dry elastic contact area ratio. However no genuine correlation could be found between dry elastic contact area ratio and two-dimensional (2D) surface roughness parameters. Furthermore, traditional gear metrology form parameters do not serve as a good measure on the changes occurring during the running-in.

A flank correction methodology for a five-axis CNC gear profile grinding machine

Form grinding is the most popular finishing process for large-size gear because of its high accuracy, efficiency, and flexibility in tooth flank modification. Theoretically, this tooth flank topographical modification is calculated using loaded tooth contact analysis (LTCA), which takes into account the gear tooth, shaft, and housing deflections. Such topographical modification, however, is difficult in the existing gear form grinding method. To simplify production of the ground tooth flank topography, this paper proposes a tooth flank modification grinding method with high-order correction based on the degrees of freedom in the five-axis computer numerical control (CNC) gear profile grinding machine. Each axis of the grinding machine is formulated as a high-order polynomial, and the sensitivity of the polynomial coefficient is derived based on the topographic normal deviation on the gear tooth flank. The ground tooth flank can be approximated to the theoretical tooth flank by adjusting the coefficients of the polynomials based on their sensitivity. We demonstrate the validity of this flank correction method numerically using a helical gear made by the five-axis CNC gear profile grinding machine.

Comparative Study of the Two Bar Billets for Bevel Gear Based on Multi-Objective Comprehensive Assessment

The two bar billets with different height-diameter ratio in enterprise were studied on the process of gear blank thermal forming. The rigid-viscoplastic finite element simulations in multifactor coupling condition of stress ,heat and wear were established. The metal flow in the process was simulated. The temperature distribution and varying of the mold and blank was forecast. The single-step wear depth and distribution of the die in forging was analysed based on Archard ,which provided sufficient data to evaluate life of the die. The reasonable aspect ratio for blank can be obtained upon the results, which will offer basis to the product.

Original Research on Logarithmic Spiral Bevel Gear

In this article, logarithmic spiral curve is successfully applied to bevel gear transmission and used as dentiform line of helicoid bevel gear. Put forward a novel logarithmic spiral bevel gear drive. Because spiral angle on each point of logarithmic spiral curve is constant, the problem of variational spiral angle is solved faultlessly. Analyze the basic characteristics of logarithmic spiral curve and demonstrates the condition of the logarithmic spiral curve used as pitch curve. Put forward the new kind of transmission form of logarithmic spiral bevel gear and it makes up the deficiency in current bevel gear transmission area.

Development of Software System for NC Dressing Form Grinding Wheel

A software system for CNC dressing involute grinding wheel was developed. When the ordinary grinding wheel was used in gear form grinding, the key was to handle the on-line dressing of involute wheel. Based on involute generation principle, an algorithm by taking straight line to approach involute with equal error was mainly studied. The NC program for dressing involute wheel was prepared by using VC++6.0 as programming tool, and wheel dressing experiment was completed. Experimental result shows that the proposed algorithm is valid，and the developed program is feasible with friendly interface. The success of this software system lays the foundation for further developing CNC gear form grinding system.

Design and Finite Element Analysis on Crown Gear Coupling of High Torque Considering Radial Restriction

In order to meet the requirements of high torque and small center distance of the twin screw pulping extruder, an improved design method of the crown gear coupling (CGC) was studied. Based on the preliminary structural design, the paper selected parameters of tooth form of the crown gear firstly, and according to the contact strength solved the tooth width, then the discussed influences of radius of displacement circle and unilateral thinning amount on tooth thickness, finally through the finite element analysis verified the design results. The results show that under the condition of radial restriction the most effective ways to increase load-bearing capability of the CGC are to improve the tooth stiffness and increase the tooth width, and the increasing of tooth width should consider the tip strength of the crown gear and avoid over-cutting. The CGC design method of the paper can meet the requirements of the twin screw extruder.

Twin symmetry roll axial rolling: new method of plastic forming profiles demonstrated using manufacture of spiral bevel gears

When using conventional manufacturing methods for machining gears, the percentage of stock material utilisation in the finished article is low due to the amount of swarf removed during machining. In addition, the machining process itself may result in low tooth strength. Adopting a plastic forming method to produce gear forms can greatly enhance the mechanical properties of the product. The size of the automotive transmission driven by a rear axle spiral bevel gear which is used as a case study in this paper is larger than that usually manufactured by the plastic forming method. Objects of this size require high capacity hot forming equipment, and even then it is difficult to obtain a full profile. In this paper, a new method of plastic forming profiles: twin symmetry roll axial rolling is described using a spiral bevel gear as a case study. The technology was analysed by producing a three‐dimensional model of the spiral bevel gear, and finite element analysis was used to simulate the process. It can be seen that the teeth were completely filled with a well defined outline and only a small amount of horizontal overfilling and vertical flash occurred because there was small contact area between the blank and rolls which minimised the rolling force.

Laser Interferometric Measuring Method of Involute Artifact and Stabilization of Measurement

Vibration and noise are serious problems with involute spur and helical gears used, e.g., in drivetrains of vehicles such as automobiles. The gear tooth flank form of micrometer order markedly affects gear vibration and noise; therefore, the tooth flank form quality must be strictly controlled to maximize gear performance. Tooth profile measuring machines used in calibration for form error inspection of involute gears usually use an involute artifact, which itself must be calibrated highly accurately. However, it is typically difficult for current tooth profile measuring machine using contact stylus to calibrate the involute artifact with a high accuracy while satisfying traceability to a national standard. A highly precise and traceable measuring technology for the involute artifact is therefore required. The direct measurement of the involute artifact we propose uses a laser interferometer, whose measurement stability is confirmed in experiments measuring the detailed form of an involute tooth flank.

Error Analysis and Simulation of Gear Form Grinding

Gear form grinding is an efficient finish machining method for the gears with hard face. There are many factors which have an influence on tooth error in grinding process. In addition to the form error of form grinding wheel, the radial feed depth of grinding wheel has large impact on the tooth error. Based on the principle of gear form grinding, the influence of wheel feed depth on tooth error is analyzed theoretically. The magnitude of error is also analyzed quantitatively according to the simulation result obtained by means of tooth error analysis module, which is developed based on VC + +6.0 software analysis. The research result has a certain reference value for preparing CNC form grinding process and setting machine tool properly.

Failure analysis on tread throw of the tire of B737-800 airplane

This paper provides an analysis of tread throw of B737-800 airplane tire. The plane experienced tire tread throw during takeoff. Laboratory observation shows that there exist numerous dense beach marks around one shoulder area of the tire. These beach marks shows that the repair exposed cords area around tire shoulder is the origin of tread separation of the incident tire. It is believed that the poor adhesion of the repair exposed cords area caused fatigue accumulative damage to develop into a tread separation. The structure form of the main landing gear of B737-800 airplane leads to unbalanced loadings on the double-tire (wheel) of the main landing gear, this gave a promotion to tread throw of the tire. For this reason, repair limits for damages at tire shoulder should be controlled more strictly for tires of B737-800 airplane. A large deep foreign object damage (FOD) cut found on the center tread rib is ruled out to be the cause of the tire tread throw according to the sequencing crack method called T-junction procedure in wreckage analysis. Tire FOD cut simulation test was carried out to confirm this viewpoint about FOD cut.

Multi-Speed Ratio Variable System to Transmit Power and Motion Continuously

Ratio variable transmissions are used when a wide range of speed and torque is required for mechanical devices. Geared transmissions are applied for a wide variety of machines. However, power and motion transmission from the input shaft to the output shaft is interrupted during the ratio changing process in geared transmissions. In order to solve this problem, a novel ratio variable system has been proposed in the previous report. This system uses a noncircular gear that can realize the reduction ratios of two gear pairs and has accomplished the ratio change from the first ratio to the second ratio while transmitting power and motion. In this report, multi-speed ratio variable system to transmit power and motion continuously is proposed in which a noncircular gear with multi-speed ratio is incorporated. Geometrical form of the noncircular gear for this system is analyzed. The experimental apparatus is constructed and the experimental result shows that this ratio variable system can realize multi-speed ratio change while transmitting torque and rotation.

Research on Mathematical Model of Grinding Force in Gear Form Grinding

Based on grinding force formation theory and the surface grinding force formula, the formula of gear form grinding force is obtained by integrating the grinding force in unit width along the involute direction. Simulation analysis and inspection result show that the mathematical model of gear form grinding force is validated. This research is helpful for selecting the technological parameters rationaly in gear form grinding, controlling the wheel dressing and ensuring gear grinding quality.