Large Gears Research Articles

Global optimization of reliability design for large ball mill gear transmission based on the Kriging model and genetic algorithm

This paper aims to improve the global optimization operation efficiency in engineering by establishing the Kriging model to simplify the calculated mathematics model. In the case of the large ball mill, this paper presents in detail the application of the stress–strength distribution interference theory to calculate the reliability of gear transmission, establishes the Kriging model for function fitting, and uses genetic algorithm to globally optimize the volume and reliability of large ball mill gear transmission. The optimal result based the Kriging model is contrasted with the Monte Carlo Method in terms of calculation accuracy, greatly improving the efficiency of calculation.

Comparisons of catches of large leptocephali using an IKMT and a large pelagic trawl in the Sargasso Sea

Leptocephali of several elopomorph families can reach sizes of 100–300 mm or larger, but it is questionable if these large eel or notacanth larvae are effectively sampled by small-mesh sampling gear in the open ocean because of net avoidance or insufficient fishing effort. A sampling survey in the Sargasso Sea using both an Isaacs-Kidd Midwater Trawl (IKMT) with fine mesh and a large pelagic trawl with large mesh sizes found that fewer species and individual large leptocephali >100 mm were collected by 25 IKMT tows compared to 4 trawl deployments. Net avoidance of the IKMT by the larger leptocephali appeared to occur at least during the day, and the large trawl did not catch any small leptocephali because of the large mesh size. A combination of net avoidance of the IKMT and greater sampling effort of the much larger mouth-opening trawl seems to have resulted in more large leptocephali being collected by the trawl. This indicates that IKMT surveys undersample large leptocephali species and that large trawls do not sample the whole assemblage of leptocephali. To fully understand the biodiversity and abundance of leptocephali in the world’s oceans, large fine-mesh sampling gear like the IKMT and very large trawls with smaller mesh will likely be needed. This may be important because leptocephali are probably more abundant in the open ocean than is realized, and their role in the ocean surface layer communities and carbon cycle is not understood.

Effect of the Impact Load on the Main Welding Outer Cylinder of Large Aircraft Landing Gear

Analysis about the cause of the main failure and the forces of the main welding outer cylinder of the recent large aircraft landing gear were given. The impact load for main welding outer cylinder in the process of the taking off and landing was calculated of 580MPa. Finite element model of the main welding outer cylinder was then established and the influence of the impact loading to the main welding outer cylinder was analyzed. The results showed that crack was most likely take place on the top of the outer cylinder, and then on the two welds. The crack expanded in an S shape. This study could provide an important basis for the safety of the aircraft landing gear inspection and service life prediction.

Laser tracker performance quantification for the measurement of involute profile and helix measurements

Standard-conforming measurements for a large involute gear were performed with a manually operated laser tracker system and the corresponding task-specific measurement uncertainties were estimated. Especially, readers using laser trackers for inspecting large involute gears will get information of a taskspecific measurement performance for the first time, which significantly differs from the laser tracker machine specification. To ensure unambiguous and repeatable measurement results, user-friendly auxiliary tools are used, which allows the operator to probe the measurement points according to existing guidelines and standards. Measurements were taken on a robust and highly accurate large involute gear measurement standard of the Physikalisch-Technische Bundesanstalt (PTB) under laboratory conditions. The size of this gear measurement standard complies with those gears used in wind power plants. The external gear materializes a left and a right hand gear as well as a spur gear. The obtained results of profile, helix and surface measurements are presented. These research activities were carried out at the PTB in the department of coordinate metrology.

Numerical analysis of a hydraulic gear micro motor

This study investigates the critical parameters that have the most impact on the structural capacity of hydraulic gear micro motors, namely, motor configuration, output torque, and speed. Seven different motor configurations were evaluated in terms of output speed and torque, which depend on the number and size of gears. During motor operation, reactive loads generated by drag forces, viscous damping forces, and oil pocketing within two adjacent teeth in contact were numerically calculated. Stress analysis using the finite element method was also performed to evaluate the structure of the aforementioned gear motor configurations. The results demonstrated that the structural capacity of a hydraulic motor does not necessarily increase when using larger gears or by increasing the number of gears. Reactive loads increase as rotational speed and gear size increase. Higher lubricant pressure is also required to attain the required output torque and velocity.

Modeling of distortions after carburization and quenching processes of large gears

A new finite element model is developed to predict the deformations, stresses, phase compositions and carbon concentration gradients that arise as a consequence of the physical processes involved in a carburization and quenching process of a large steel gear. Firstly, the diffusion of carbon at elevated temperatures in the austenitic range is studied in a diffusion model. Secondly, the calculated carbon concentration distribution is used as an input for a model that couples the thermal, metallographic and mechanical effects during the quenching process and calculates the evolution of the temperature, phase composition and deformation history at any point in the gear. Two effects typical for oil quenching of large gears are incorporated in the model. The first is the influence of the gear's own weight while hanging on chains before, during and after entering the quench bath. The second is the three-dimensional effect that it takes time between the moment the gear enters the oil quenching bath and the moment when the gear is fully immersed. The non-uniform temperature distribution over the gear's axis causes a non-homogeneous plastic deformation. A diffusion-thermo-metallo-mechanical model that takes these effects into account is compared with a model that does not. The results show that these effects should be incorporated.

An approach to evaluate the effects of nonlinear traveling joints on dynamic behavior of large machine tools

In order to select the best possible design from various candidates based on structure configurations of traveling components, it is essential to evaluate the effects of traveling joints on dynamic behavior of large machine tools. Firstly, regression analysis and energy method were used to determine the nonlinear parameters of the metal–plastic joints. Then, a nonlinear receptance coupling approach was used to establish a simplified model of a large machine tool including nonlinear joints. The evaluations of the large machine tool were analyzed with different milling forces. The results show that the nonlinearity of traveling joints significantly influences the resonant frequency and the response amplitudes. Experimental verifications were performed on a prototype of a large machine tool for milling large gears.

Current Status and Trends of Large Gears Metrology

Large gears are the indispensable parts of large-scale equipments,but it is a tough task to inspect large gears owing to their increasing technical specifications,large size and heavy weight.Many factors affecting large gears measurement are analyzed.The measuring principals,methods and typical instruments of two kinds of large gears measurement: off-machine measurement and on-machine measurement,are reviewed in detail,as well as their specific advantages and disadvantages are discussed.Based on the analysis of manufacture characters and application requirements for large gears,the general requirements and development direction are summarized,that are holistic model description and fast measurement.The new ideas,principles,solutions and artifact are introduced as well,especially,to inspect large gears with small instruments effectively will become a trend.As a solution,a new on-machine measuring method combining the virtues of laser tracking with coordinate metrology can figure out the problem of establishing relationship between the measuring instrument and large gear,this method also can be applied to the inspection of others complex and large parts,so it shows a favorable application prospect.

The Modification and Design Method of Large Gear

Due to the difficulty in large gear modification, a method that modifying gear tooth in the processing through correcting gear cutter was proposed. In this paper, modification theory of large gear and design method of gear cutter were introduced in detail. Based on gear meshing theory, the tooth equation of large gear was deduced from the equation of correcting cutter. The processing was simulated by using Matlab software, and it verified the validity of theoretical analysis.

Standards for testing freeform measurement capability of optical and tactile coordinate measuring machines

For decades three-dimensional (3D) measurements of engineering components have been made using fixed metrology-room based coordinate measuring machines (CMMs) fitted most commonly with single point or to a much lesser extent, scanning tactile probes. Over the past decade there has been a rapid uptake in development and subsequent use of portable optical-based 3D coordinate measuring systems. These optical-based systems capture vast quantities of point data in a very short time, often permitting freeform surfaces to be digitized. Documented standards, for example ISO 10360, for the verification of fixed CMMs fitted with tactile probes are now widely available, whereas verification procedures and more specifically verification artefacts for optical-based systems are still in their infancy. Furthermore, the industry is seeking traceability in 3D measurements of high precision components. A recent requirement is the demand for highly accurate measurements of large gears with diameters up to 1000 mm as used in gear boxes of wind turbines. Up until now it has been impossible to ensure traceability of 3D measurements of big gears, since no traceable standards were available. This paper describes three different types of artefacts that were developed during the project, namely tetrahedron artefacts for testing the basic measurement capability of optical 3D devices, freeform verification artefacts for testing the capability of measuring complex geometry, and a large gear artefact for task related calibration of different types of CMMs. In addition, artefact calibration data and associated measurement uncertainties and international intercomparisons are presented. These developments will be of considerable value to end users, calibration laboratories and producers of optical and tactile CMMs.

Kinematic Modeling of the Gear Shaping Based Novel Cutting Area Analytical Method for Large Gear Shaper

Large gear is widely used as a key component of heavy machineries. Gear shaping is the most commonly process of large gear manufacturing. For the design of large gear shaper, the determination of its main driving force depends on the empirical formula. However, its result has shown that the main driving force is much larger than what really needs, which produces a lot of waste. A novel analytical method is proposed in this paper. According to this method, the cutting area can be calculated precisely, and the design of main driving force will be more reasonably, it also provides the theoretical foundation for the design of large gear shaper.

Study on the Calibration Method for Orthogonal 3D Scanning Probe System Based on the Linear Calibration Matrix

Gear Measuring Center(GMC) is a kind of instrument for measuring the accuracy of the tooth surface. For the gears whose modulus is not small, the contact measuring method is commonly used. 3D scanning probe is the key component. Because it can reflect the trend of 3D error of the tooth surface, and has the advantages of high-speed and high-precision, it is generally used in the measurement of complex and large gear. However, due to the anisotropy of the mechanical structure of the probe itself and the influence of the external environment factors, it will result in mutual influence among the three deformation directions of the probe, that is coupling phenomenon, therefore it must be calibrated before measurement. In the paper, on the basis of the structure of 3D scanning probe and measurement principle, the varying coefficients linear calibration matrix was innovatively proposed. Through measuring the points planned on the standard ball, based on the spherical equation, the overdetermined nonlinear equations were established. The equations were iteratively solved with the least squares method and genetic algorithm. The calibration matrix was finally experimental verified. The experimental results show that the linear calibration matrix has higher calibration precision than traditional constant coefficient calibration matrix, the calibration method has the advantages of high-efficiency and high-precision, it has a certain reference meaning for the research of the calibration of the probe.

Design and Research of Double-Drum Winch for Lowering Mooring Anchor Chains

The designed double-drum winch is applied to the development of Liwan 3-1 gas field of the South China Sea for lowering mooring anchor chains, which is composed of motor, brake, reducer, front and rear drums, two-stage gear transmission devices, rack and base. There is an intermediate axle between two drums of the winch. On the intermediate axle there are two gears, a large one and a small one. The large gear installed on the intermediate axle goes into mesh with the pinion gear installed on the output shaft of reducer, and the small gear installed on intermediate axle meshes with the large gears installed on the front and rear drums separately. The speed of rotate from the motor is sent to the two-stage gear transmission devices by the reducer, to realize two drums rotate simultaneously in the same direction. Compared to the double-drum winch of multi-motor synchronous drive, the designed double-drum winch can be more reliable and avoid the difficult technical problems of multi-motor synchronous drive and control in a large extent.

Experimental and Numerical Determination of Cutting Forces and Temperatures in Gear Hobbing

Hobbing is one of the most productive methods for manufacturing external gears. According to the requirements of green manufacturing, the lubrication in gear hobbing has to be reduced with the final aim of dry machining. Influences due to thermal aspects during machining have to be considered, especially in hobbing of large modules or ring gears, because in this case, hobbing could be the last step in the process chain. Within the priority program (SPP) “Modeling, Simulation and Compensation of Thermal Effects for Complex Machining Processes”, founded by the DFG, special emphasis is laid on the thermally caused geometrical deviation in dry cutting. To predict the heat flux, which leads to thermal expansions and geometrical deviations of the gear, a validated model for forces and temperatures is necessary. The validation of single generation positions and chips is focused in this paper.

Research on Machining Simulation of Large Scale Spiral Bevel Gear Machine Tool

The machining coordinate system of spiral bevel gear machine tool is established through analyzing the machining mechanism of spiral bevel gear, and the three dimensional structure model of large scale spiral bevel gear machine tool is also established using the new cutting feed method. The numerical control machining model of large scale spiral bevel gear machine tool is proposed. Finally, the machining simulation of one pair of given large scale spiral bevel gears has been done, the result indicates that the machining simulation model meets the prospective design requirement.

Method of On-Machine Spacing-Tooth Measuring Large Gear Pitch Accumulated Errors and Technology of Compensating a Geometric Eccentric

The method of on-machine measuring pitch accumulated errors of large gears is much convenient and there are no dimension limits of measured gears. The technology of non-synchro-drive and synchro-measurement is utilized to ensure continuous measurement. The spacing-tooth method of measuring pitch accumulated errors of large gears is used to decrease measuring errors. The technology of compensating a geometric eccentric is applied in data treatment, and the high accurate measurement is carried out

Studies on Insert-Type Gear Formed Milling Cutters

In roughing of large module gears, high efficient gear cutting with a formed milling cutter is noticed. In this case, the milling cutter is an insert type with both negative top rake and side rake angles. It is well known that negative rake angles increase cutting force and produce undesirable cutting surfaces. In this paper, a design method of insert-type gear formed milling cutters with both positive top rake and side rake angles is proposed. Firstly, the profile of cutting edge is calculated from the axial profile of the cutter by giving the design parameters such as the top rake angle, side rake angle and cutting edge angle, and the shape of insert pocket for the cutter body is designed by giving the thickness, length and width of the insert. However, these obtained design parameters are not always available because interference between the flank face and the work may occur. Therefore, a simulator that can interactively decide these design parameters was developed. Finally, the formed milling cutter were designed and made using the proposed method. Cutting tests using the trial-made milling cutter were carried out. As the results, the sufficient accuracy as the cutter in roughing of large module gears was obtained.

Measuring large 3D structures using four portable tracking laser interferometers

A new concept that allows measuring 1D–3D objects in the range of several centimeters to 5m×5m×5m is presented. In general terms the concept can be seen as a task specific correction of geometrical errors of coordinate measuring machines (CMMs). The developed system comprises a commercial CMM, its measurement and its evaluation software and a set of at least four high accurate tracking laser interferometers. The CMM is simply used as a mover which allows to capture points on the surface of a measuring object. In parallel the tracking laser interferometers follow a retro-reflector located close to the stylus tip of the tactile probe of the CMM. Based on a multi-lateration algorithm 3D-positions are calculated from the measured interferometric distances. Finally, two sets of coordinates emerged, namely, one by the CMM and the second from the metrological frame of the tracking laser interferometers. The interferometrically measured positions are usually more precise than the positions measured by the CMM. This is due to the high accuracy of the interferometric system and also due to the fact that the measurement positions are taken in a manner which almost avoids Abbe errors. Because of that, the measurement positions of the CMM are substituted with the more accurate measurement points calculated from distance measurements of the tracking interferometers. The position coordinates thus obtained are used for the further computerized evaluations, which yield the geometric parameters of the object measured. First measurements under laboratory condition show very promising results. It has been demonstrated that the concept is suitable for the high precision calibration of large workpieces with small tolerances, for instance, for the calibration of large gears for the windmill industry.

Intergranular Fracture of Spoke Plate of a Large Gear

A crack occurred on the spoke plate of a large marine gear apparently when the gear was being moved at the fabrication site. Fractographic analysis of the fracture surfaces in this study revealed that the crack initiated from the core of spoke plate, and propagated circumferentially toward the surfaces of two holes on the spoke plate and simultaneously to the upper and low ends of the gear. Intergranular fracture was found in crack origin and in regions where the fracture developed slowly. The intergranular facets were associated with ductile shearing between the facets. Transgranular cleavage fracture was apparent in the fast crack propagation region. Metallographic observations also revealed that a type of macro-casting defect, general spot segregation, was generally present on the gear material. A large size macro-spot segregation zone was present near the crack origin and presented a favorable metallurgical condition for hydrogen-induced fracture. The conditions conductive to hydrogen embrittlement include the presence of excessive amounts of S and P, and the appearance of bainite. Therefore, it was concluded that the crack of the spoke plate of the gear was hydrogen induced. The probable source for hydrogen was introduction during the melting and casting process.

The Technology Research on Milling Large-Size Spiral Bevel Gears of the Finger Cutter

This paper refers to the finger cutter forming method to process large-size spiral bevel gears by using processing principles, tools, processing technology and path equations. In the actual production process, the method is made a rapid development for the revolutionary innovative process of large spiral bevel gear. The method of research is different from the disc cutter, so the processing of large spiral bevel gears have a new processing method to achievement.