Metal flow law of spur gear for truck under different cold shaping modes

Figure 1 shows the equivalent stress distribution of spur gear under different cold shaping methods. During full tooth shaping, the deformation area is the whole tooth, including tooth top and tooth root, as shown in Figure 1 (a); During the cold shaping of tooth surface and tooth root, although there is no shaping amount at the tooth top, the excess metal on the tooth surface will flow to the tooth top, which plays the role of diversion, as shown in Fig. 1 (b); When only shaping the tooth surface, the excess metal on the tooth surface flows to the tooth top, and the plastic deformation only occurs at the tooth surface and tooth top, as shown in Figure 1 (c).

(a) Full tooth shaping (b) Tooth surface and root shaping (c) Only shaping tooth surface

Figure 2 shows the section equivalent stress distribution in the deformation zone of spur gear under different cold shaping methods. It can be seen from the figure that during full tooth shaping and tooth surface root shaping, the deformation area is mainly concentrated on the whole tooth profile, and the deformation area of full tooth shaping is larger than that of tooth surface root shaping. When only shaping the tooth surface is adopted, the deformation area is the tooth surface and tooth top, and the inner metal does not undergo plastic deformation, mainly axial rigid movement.

(a) Full tooth shaping (b) Tooth surface and root shaping (c) Only shaping tooth surface

Fig. 3 (a) – (c) respectively show the effect change distribution of spur cylindrical gear after full tooth shaping, tooth surface root shaping and only shaping the tooth surface. It can be seen from the figure that the upper and lower ends of spur cylindrical gear are in an unconstrained state during shaping, so the equivalent strain values at these two places are the smallest. Only shaping the tooth surface is used for cold shaping, the equal effect deformation distribution of the tooth surface is more uniform, and the deformation is more uniform than the first two shaping methods.

(a) Full tooth shaping (b) Tooth surface and root shaping (c) Only shaping tooth surface

Fig. 4 (a) – (c) respectively show the distribution of effects such as full tooth shaping, tooth surface root shaping and straight tooth cylindrical gear section after only shaping the tooth surface. It can be seen from the figure that with the full tooth shaping method, the equal effect at the tooth top becomes the largest, and the deformation of the tooth top is the largest in the cold shaping process. When the tooth surface and root shaping method is adopted, the equal effect deformation distribution of the tooth surface is uneven, and the uneven tooth surface deformation will have some impact on the accuracy of the reshaped spur gear. Only shaping the tooth surface is adopted, the distribution of equivalent strain on the tooth surface is more uniform, and the plastic deformation only occurs on the surface of the tooth surface, and its shaping effect is better than the first two shaping methods.

(a) Full tooth shaping (b) Tooth surface and root shaping (c) Only shaping tooth surface

Fig. 5 shows the distribution of the maximum principal stress of the tooth concave die of spur cylindrical gear under different cold shaping methods. When the full tooth shaping and tooth surface root shaping methods are adopted, the tooth top of the tooth concave die bears a large compressive stress. For example, FIG. 5 (a) shows the stress of the full tooth shaping concave die, and the maximum compressive stress at the tooth top is about 1800mpa. Fig. 5 (b) shows the stress of the concave die during tooth surface root shaping, The maximum compressive stress at the tooth top is about 2010mpa; The compressive stress in the contact area with the tooth surface is in the range of 800-1200mpa. When only shaping the tooth surface is adopted, because the tooth root is not shaped, the tooth top of the tooth concave die does not bear large compressive stress, and the compressive stress value in the contact area with the tooth surface is within the range of 700-1200mpa, as shown in Fig. 5 (c). Cold shaping by shaping only the tooth surface can significantly reduce the stress and die deformation of the tooth concave die and prolong the service life of the shaping die.

(a) Full tooth shaping (b) Tooth surface and root shaping (c) Only shaping tooth surface

Figure 6 shows the forming force curve of spur gear under different cold shaping methods. It can be seen from the figure that the cold shaping process can be roughly divided into three processes: initial shaping stage, stable shaping stage and final shaping stage. Only the deformation degree of shaping tooth surface is the smallest, so the forming force is the smallest; The deformation degree of full tooth shaping is the largest, and the forming force is larger than the other two shaping methods. The maximum forming force of full tooth shaping is about 297.2kn, the maximum forming force of only shaping tooth surface is about 174.4kn, and the forming force of only shaping tooth surface is only 58.7% of the forming force of full tooth shaping.

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