Bevel Gear Forging Research Articles

904 曲がり歯かさ歯車の鍛造加工法の研究 : 軸角任意の場合(模索潤滑設計I)

904 曲がり歯かさ歯車の鍛造加工法の研究 : 軸角任意の場合(模索潤滑設計I)

The prediction of maximum forging load and effective stress for different material of bevel gear forging

The manufacture of gears by applying hot or cold bulk forming processes is a quite widespread production method due to its well-known basic advantages such as material and time cost reduction and the increased strength of the teeth. However, the associated process planning and tool design are more complicated. In the precision forging of gears, the workpiece volume, the die design, the power requirement and careful processing are more critical than traditional forging technology. For complete filling up, predicting the power requirement is an important feature of the near net-shape forging process. In this paper, a finite element analysis is utilized to investigate the material properties such as yielding stress, strength coefficient and strain hardening exponent effects on forming load and maximum effective stress. The adductive network was then applied to synthesize the data set obtained from the numerical simulation. The predicted results of the maximum forging load and maximum equivalent stress of bevel gear forging from the prediction model are consistent with the results obtained from FEM simulation quite well. After employing the prediction model one can provide valuable references in prediction of the maximum forging load and maximum equivalent stress of bevel gear forging under a suitable range of material parameters.

Process design for closed-die forging of bevel gear by finite element analyses

Abstract In this study, process design for closed-die forging of a bevel gear used for a component of automobile transmission was made using three-dimensional finite element simulations. Process variables of the closed-die forging of the bevel gear were selected to be the pressing type, punch location, and billet diameter. Based on FE simulation results, appropriate process design without causing under-filling and folding defect was determined. In addition, with design of a die set including die insert and stress ring, cold forging of the bevel gear was experimented to estimate effectiveness of the designed process. From experiments, it was found that bevel gear with complete formation of the teeth was obtained without making any forming defects although flash in a forged product and punch fracture was occurred due to a slight difference in the punch stroke during formation. Through comparison of results between experiments and FE simulations, it was found that die clamping device should be modified for increase of the clamping force and improvement of the die safety.

212 曲がり歯かさ歯車の鍛造加工法の研究(OS04 歯車の加工・製造)

212 曲がり歯かさ歯車の鍛造加工法の研究(OS04 歯車の加工・製造)

I17 曲がり歯かさ歯車の鍛造加工法の研究(I1 加工・生産システム1(マイクロ技術の高度化))

I17 曲がり歯かさ歯車の鍛造加工法の研究(I1 加工・生産システム1(マイクロ技術の高度化))

402 曲がり歯かさ歯車の鍛造加工法の研究(OS4-1,OS4 機械加工の最新技術)

402 曲がり歯かさ歯車の鍛造加工法の研究(OS4-1,OS4 機械加工の最新技術)

曲がり歯かさ歯車の鍛造加工法の研究(O.S.03-1 歯車の加工・製造(1))

曲がり歯かさ歯車の鍛造加工法の研究(O.S.03-1 歯車の加工・製造(1))

Process modification of bevel gear forging using three-dimensional finite element analysis

Bevel gear forging has several advantages as compared with conventional gear forming by a cutting process. For example, it reduces the material loss, and the production lead-time and also has the advantage in product quality improvement of using plastic material flow in the gear teeth. In general, gear forging has a process sequence including preforming and final forming because of the geometrical complexity of its tooth profile. Despite the importance of designing the process sequence, conventionally it has been done by the design expert with exhaustive trial-and-error. Recently, there have been many trial approaches to find the optimal process and die design, and to acquire the quality-related information after forming from simulation using the FEM. In this study the bevel gear forging process is simulated by three-dimensional FEM based on rigid–plastic material modeling, and it is applied to the die design consideration to improve the product quality and to secure the effective material flow. Finite element simulations are performed for two types of bevel gear forging processes to find a defect-free forging process, and comparisons are made between the two processes. It has been thus shown how an improvement can be made through an improved design using finite element simulation.

Stress analysis of the precision forging die for a bevel gear and its optimal design using the boundary-element method

The lifespan of a bevel-gear forging die is determined mainly by its stress state. In order to reveal the stress state and to secure the optimal design of the forging die of a miniature automobile level gear, a boundary-element method (BEM) program has been developed and used to assess a doubly-reinforced die for the precision forging of a bevel gear. According to the program developed by authors, the characteristics of the BEM program are given. On the basis of the results calculated by the use of the BEM, the region of dangerous stress is determined and the effect of the amount of interference on the distribution of stress is revealed.

Preform Design for Forging Rotationally Symmetric Parts

Abstract This paper describes an upper bound modelling based technique to design preforms for forging of rotationally symmetric parts. A reversing algorithm which results in improved metal flow in the final stages of filling the cavity is applied to the precision forging of bevel gears. The predicted preform has a simple rotationally symmetrical profile which accommodates the simultaneous filling of the gear teeth. Experimental results show that the preform designed by this technique requires less energy in the final stages of the forging.

Application of the 2D finite element method to simulation of cold-forging processes

In recent years, computer aided engineering (CAE) techniques have been increasingly applied with great success in metal-forming research, as well as in the cold- and hot-forging industry. Initially, computer simulation of metal flow and detailed stress analysis of dies were conducted by forging companies that supply the aerospace industry ( J. Mater. Process. Technol., 27 (1991) 43–51). During the last several years, however, the two dimensional computer code Deform, developed by Battelle Columbus Laboratories and supported by Scientific Forming Technologies Co., has been fully commercialized. This code is now used extensively also by non-aerospace forgers for the investigation of die fill, defect analysis and prevention, as well as for prediction of part properties. At the Engineering Research Center for Net Shape Manufacturing (ERC/NSM), Deform is one of the available computer aided tools used in cold-forging research and for educational purposes. This paper, adapted for cold-forging applications from an earlier publication ( J. Mater. Process. Technol., 33 (1992) 31–55) summarizes industrially relevant research results obtained with Deform. It reports on an investigation of a suck-in type extrusion defect, forging of bevel gears, stress analysis of forging tooling, design of multi-stage cold-forging operations, design of a net-shape cold-forging operation for pipe fittings and development of a new test to evaluate lubrication in cold forging.

Treatment of contact traction at the die-workpiece interface for the elastic analysis of die deformation

A method to calculate the contact traction on the die-workpiece interface is proposed. A systematic method for performing the elastic finite element analysis of the die deformation by using the information obtained from the finite element analysis of the workpiece deformation is proposed. The proposed method can be applied to both the two-dimensional and three-dimensional analyses of die deformation independently of the friction modelling and the constitutive equations. A rigid-plastic finite element analysis of workpiece deformation is carried out for the upsetting of a cylindrical workpiece. In order to check the validity of the present method for both flat and curved contact surfaces, the elastic finite element analysis of die deformation is then performed for flat square block forging as well as for a bevel gear forging (Yoon and Yang, Int. J. Mech. Sci. 32, 277–291, 1990) [8]. From the computation it is shown that the error due to the transfer of data from the workpiece mesh to the die mesh does not influence appreciably the elastic deformation of the die. The proposed method can be applied to arbitrarily curved die geometries in three-dimensional metal forming problems.

Application of the 2D finite element method to simulation of various forming processes

In recent years, computer-aided engineering (CAE) techniques have been applied increasingly with great success in metal forming research, as well as in the cold and hot forming industry. Initially, computer simulation of metal flow and detailed stress analysis of dies were conducted by forging companies that supply the aerospace industry. During the last several years, however, the two-dimensional computer code DEFORM, developed by Battelle Columbus Laboratories, has been fully commercialized. This code is now also used extensively by non-aerospace forgers for the investigation of die fill, defect analysis and prevention, as well as for the prediction of part properties. At the Engineering Research Center for Net Shape Manufacturing (ERC/NSM), deform is one of the available computer-aided tools used in metal forming research and for educational purposes. This paper summarizes some of the industrially relevant research results obtained with deform, including the prediction of flow-induced defects, precision forging of aluminium alloys, investigation of a suck-in type extrusion defect, forging of bevel gears, stress analysis of forging dies, and development of a new test to evaluate lubrication in cold forging.

Numerical and physical modelling of cold forging of bevel gears

Bevel gears are high-volume parts used in the automotive industry, which are being increasingly produced to net shape by cold forging. However, complex multi-action tooling designs and long die try-out phases needed to produce a net shape part and to guarantee a robust process, result in long development times. High punch pressures can cause frequent punch failures during production, leading to unwanted downtimes. In this paper, two modelling techniques, finite element (FE) based numerical modelling and physical modelling with plasticine, are being presented as process design tools in cold forging. A strategy has been developed to allow successful 2D FE modelling of bevel gear forging. The results from the process simulation are then used as load input data for a punch stress analysis. It is, thus, possible to modify the punch geometry in order to reduce the punch stresses. Physical modelling is then applied to verify the results of the 2D FE simulations.

A three-dimensional rigid-plastic finite element analysis of bevel gear forging by using a remeshing technique

A three-dimensional remeshing scheme implemented by using a modular concept is proposed for the finite element analysis of a complicated forging process. In order to show the effectiveness of the scheme, forging of a bevel gear is simulated by using several basic modules in the general rigid-plastic finite element code (Yoon and Yang, Int. J. Mech. Sci. 30, 887, 1988; Yang et al., Int. J. Mech. Sci. 31, 145, 1989) developed for cold forging. Criteria for remeshing as well as a scheme for the mapping of state variables are proposed for three-dimensional remeshing. The computational results are compared with experimental data in order to check the validity of the simulation. The computational results show that the computation can be effectively carried out by using the proposed remeshing scheme and that it can be extended to other more complicated product geometry.

Application of CAD/CAM Techniques to Close Tolerance Forging of Spiral Bevel Gears

Close tolerance forging of spiral bevel gears, requiring only a single or no finish machining operation, offers considerable advantages because this method of manufacture (a) reduces material losses and machining costs and (b) Increases the fatigue life of the gears. A few companies around the world are able to produce spiral bevel gears by precision forging. However, the development of the process for each new gear design requires usually a considerable amount of trial and error. Thus, application of computer techniques to die design and manufacture of the gear forging dies represents an attractive alternative. This paper describes the computer techniques, used for generating the spiral bevel tooth surface geometry by simulating the gear cutting process. Further, the calculation of die corrections, the manufacturing of EDM electrodes and of the forging dies are discussed. Finally, the results of forging trials are summarized and a brief progress report on this on-going development project is given.