Finite element simulation study on the forging pro

Research on finite element simulation of no flash forging process of sliding fork

Abstract: sliding fork is traditionally produced by open die forging process, which has large flash, serious material waste and poor dimensional accuracy. In order to reduce the cost of forgings, according to the shape characteristics of the sliding fork, this paper proposes a new process of less flash die forging, which makes the preform form in the closed die chamber and realizes the near net shape of forgings. According to the principle of constant volume, the calculated blank is processed to obtain the prefabricated blank. In this paper, deform 3D software is used to simulate and study the forging process of sliding fork without flash and small flash. The simulation results show that the new process significantly improves the material utilization and forming quality, and reduces the forging load

key words: finite element simulation of sliding fork closed flangeless forging

1 preface

the development of automobile industry has an increasing demand for high-quality and low-cost forgings. The steering universal joint sliding fork (as shown in Figure 1) is an important automobile part, which has complex shape, dimensional accuracy and form and position tolerance requirements. The integration development of auto parts and new energy vehicles is high, and the forging process is poor. At present, the main domestic forging plants mainly use open die forging process for production, with poor forging quality and low material utilization [1]. Factories urgently need a new processing technology to improve the forming quality, reduce material waste and reduce costs

Figure 1 sliding fork forgings

no flash forging process is an advanced forging process, which is usually used in the production of high-quality forgings. As shown in Figure 2, compared with the forging process with flash, the forging process without flash is formed in a closed die cavity, which does not produce flash, saves materials, has high forming accuracy, and can achieve near net shape or net shape of forgings [2]

as shown in Figure 1, the shape of the sliding fork is complex, and the cross section of the fork rod is circular, so the traditional integral closed die forging process is difficult to achieve no flash forging. Based on the study of traditional flash free forging process [3,4] and extrusion process [5], a new closed die forging process without flash for sliding fork is developed to meet the requirements of flash free forging for sliding fork

Fig. 2 Comparison between open die forging with flash and closed die forging without flash

Fig.2: compare between open die forging with flash and closed die forging without flash

structural design of no flash forging die

according to the shape characteristics of sliding fork, a set of new structure forging die is designed in this paper to meet the requirements of no flash forging. The die consists of upper and lower dies and punches, as shown in Figure 3. The upper punch is installed on the slider of the press, and the lower punch is fixed on the base

Figure 3 forging die structure

fig.3: structrue of the dies

Figure 4 shows the die action sequence in the forging process, and the specific actions are as follows:

i) blank 1 is placed in the die chamber of lower die 4

ii) the sliding block descends, the upper and lower cylinder pistons are linked, so that the upper die 3 and the lower die 4 are in contact, and the clamping force is applied to the upper and lower dies to form a closed die cavity and clamp the pre pressed blank 1

iii) the sliding block continues to descend, the pressure of the upper and lower oil cylinders remains unchanged, and the metal of the fork blank is roughly extruded and deformed under the action of the upper and lower punches until the die chamber is filled. The die consists of upper and lower dies and punches, as shown in Figure 3

Figure 4 mold action sequence

fig.4: tooling movement sequence

3 finite element analysis of non flash forging process

3.1 preformed blank design

in mass production of sliding forks, cross wedge binding process is usually used to produce preformed blanks. According to the principle of constant volume, based on the calculation of the blank of the sliding fork and the design experience of the cross wedge binding die, the prefabricated blank of the sliding fork is designed. Figure 5 shows the design of the prefabricated blank fork of the sliding fork. Figure 6 shows the geometric parameters of the preformed blank

Fig. 5 prefabricated blanks

fig. 5 Preform

Figure 6 geometric parameters of preform

Fig.6: sketch of perform

3.2 simulation analysis of sliding fork forming process

root market confidence rebounds, according to the shape and symmetrical characteristics of the sliding fork, select the 1/4 model of the sliding fork for simulation analysis, and the 1/4 finite element model is shown in Figure 7. The prefabricated blank a is higher (as shown in Figure 5), and will be clamped when the upper and lower dies are closed. The input parameters of clamping analysis are shown in Table 1. Table 1 clamping step input parameters

Figure 7 FE analysis model

fig7: FE simulation model

figure 8 shows the equivariant distribution of the blank after clamping, and the prefabricated blank only has a small deformation at a. Figure 9 shows the load stroke curve of the clamping process. It can be seen from Figure 9 that about 160000n force is required to clamp the whole prefabricated blank

Fig. 8 equivalent strain distribution of clamping process

fig.8: effective strain distribution of holding process

Fig. 9 load stroke curve of clamping process

fig.9: punch force curve of holding process

Fig. 10 shows the metal flow state at different times in the blank deformation process under the ideal state (precise blanking and precise size of prefabricated blank)

Figure 10 metal flow in forging of a slide fork

fig.10: material flow in forging of a slide fork

according to the simulation results, under the action of the punch, the fork of the preformed blank is first upset, and the metal quickly flows to both sides of the die bore until it contacts the side wall of the die bore, and then as the punch continues to press down, the metal flows to the die bore of the fork boss with the minimum flow resistance, The metal under the punch flows upward along the side wall of the die bore until the forming is completed. In the whole forming process, the deformation velocity field of the blank is evenly distributed without disorder, so there will be no folding defects in the whole forming process and the forming is complete. As shown in Figure 12, during the pressing process of the punch, the strain of the fork of the forging is mainly concentrated in the fork and the connecting skin of the fork mouth, while the strain at the part connected with the rod is very small

Figure 11 velocity distribution in the forging of a slide fork

figure.11: velocity distribution in the forging of a slide fork

Figure 12 fork strain distribution

figure.12: effective strain distribution in fork section

the key to forming quality is to strictly control the metal flow in the whole forming process, and try to ensure that the metal only flows along the thick and radial directions, and there is no displacement or minimal displacement in the axial direction. The realization of this process must ensure accurate blanking. The length accuracy of the prefabricated blank is required to be high. When the blank is placed into the mold cavity, it has been accurately positioned in the length direction. After clamping, the axial flow of the material is further limited

Figure 13 shows the load stroke curve of the forging process. According to the load stroke curve, the load required for forging half of the sliding fork is about 7.4mn, that is, 15mn press can meet the forging requirements of the whole sliding fork

Figure 13 sliding fork forging load curve

fig.13: punch force curve of forging a slide fork

4 simulation of small flash closed die forging process

the sliding fork closed flash free die forging process has a very high material utilization rate, but the volume accuracy of the preformed blank used in this process is very high, resulting in a high processing cost of preformed blank. In order to reduce the processing cost of prefabricated blanks and improve the utilization rate of materials, the closed die forging process of small flash of sliding fork is also designed in this paper

4.1 structural design of small flash forging die

based on the non flash die forging process of sliding fork, this paper also puts forward the small flash die forging process (flash accounts for about 2% of the blank volume). The structure of the small flash forging die is the same as that of the non flash forging die, except that a small flash structure is added at the middle parting position at the bottom of the upper and lower die forks, as shown in Figure 14. The action of the die is the same as that of the forging die without flash

Figure 14 flash structure

fig.14: flash structure/div

4.2 simulation analysis of small flash die forging process

the volume of preformed blank is 1% larger than that shown in Figure 6, and the implementation of new EU regulations on blank volume increase. Figure 15 shows the 1/4 finite element analysis model of sliding fork

Figure 15 finite element analysis model

figure.15: FE simulation model

Figure 16 shows the metal flow during the molding process. It can be seen from Figure 16 that the metal flow condition in the small flash forging process is similar to that in the non flash forging process. When the punch goes down 26mm, the metal near the flash bridge at the bottom of the fork is under enough pressure to open and move towards the flash bridge to form a flash. After filling the mold cavity with metal, as the punch continues to descend, the excess metal flows to the warehouse through the flash bridge

Figure 16 fork into our cooperation with customers to improve the design, production, market attractiveness and performance of their products

fig.16: material flow in fork section

Figure 17 fork equivalent effect variation distribution

Fig.17: effective strain in fork section

Figure 18 shows the forging load stroke curve in the process of small flash forging. It can be seen from the figure that in order to ensure the integrity of blank forming, the height of the flash bridge is low, and the flow resistance of metal to the flash bridge is large, resulting in a slight increase in the load required for the forming of the sliding fork, and the load required for the forming of the whole sliding fork reaches 17.2mn

Fig. 18 load stroke curve of forging a slide fork

fig.18: force curve of forging a slide fork

as a comparison, the load required for the sliding fork open die forging is calculated. The length of L pieces of sliding fork forgings is 21cm, and the horizontal projection area (including the area of fork mouth skin and flash) is 340cm2, that is, the converted diameter D pieces and the average width b are 20.8cm and 16.3cm respectively, and the value is 65n/mm2 according to the corresponding chart

according to the empirical calculation formula of die forging tonnage on hammer [4]:

it is calculated that g = 24930n, that is, 25MN press is required for open die forging of this sliding fork forging

5 Conclusion

according to the shape characteristics of the sliding fork, on the basis of the traditional integral closed die forging, combined with the advantages of the extrusion process, a new forging process without flash and small flash of the sliding fork has been successfully developed. The finite element simulation research shows that, compared with the open die forging process, the new closed die forging process without flash and with small flash proposed in this paper has the advantages of high forging precision, good forming quality, high material utilization rate, small equipment tonnage and so on, and has a good industrial application prospect

References:

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[2] E. Doege, R. bohnsack Closed die technologies for hot forging［J］. Journal of materials processing technology 98 (2000):165-170

[3] T. Altan et al Modern forging equipment, materials and processes [M] Beijing: National Defense Industry Press, 1982

[4] Zhang Zhiwen Forging technology [M] Xi'an: Northwestern Polytechnic University Press, 1988

[5] Hong Shenze Extrusion process and die design [M] Beijing: China Machine Press, 1996

[6] Victor Vazquez, Taylan altan Die design for Fashless forging of complex parts［J］. Journal of Materials Processing Technology 98 (2000) ：81－89

[7] T. Takemasu, V. Vazquez, T. Altan. Investigation of metal flow and preform optimization in flashless forging of a connecting rod［J］. Journal of materials processing technology 1996, (59):