JP4832136B2 - Shaft enlargement processing method - Google Patents

Description

  The present invention relates to a shaft enlargement processing method for a hollow shaft material.

Conventionally, as an aspirational idea aimed at drastically reducing the total machining cost, the intermediate part of a shaft with a uniform diameter is obtained by applying a rotational bending stress to the shaft in a compressive stress state using the mechanical ratchet phenomenon. There is a plastic working method (hereinafter referred to as a shaft enlargement processing method) in which an enlarged portion having a shaft diameter locally enlarged is formed.
Using the shaft enlargement processing method, a machining experiment is performed on a solid shaft material, and the deformation behavior in the machining process is expressed numerically (see Patent Document 1).
According to this, for the influence of each machining condition (bending angle θ, axial compressive stress σ _c ), a unified cycle parameter N ₀ is derived, and the axial enlargement deformation behavior under various machining conditions can be estimated. ing. Furthermore, the fatigue characteristics of the workpiece and the soundness against fatigue damage have been clarified.

However, there are many hollow shaft materials for weight reduction and insertion hole requirements, and it is highly expected that the enlarged portion is directly processed from the hollow shaft material. The application and development of the shaft enlargement processing method to the partial enlargement processing of the hollow shaft material is meaningful from an engineering and industrial viewpoint, and it can be expected to be a useful processing method. There is not enough elucidation about the deformation behavior of the shaft.
JP 2003-39133 A

  The problem to be solved is to elucidate the deformation behavior when integrally forming the enlarged portion from the hollow shaft material using the shaft enlargement processing method, and to make it possible to form the desired enlarged portion.

According to the first aspect of the present invention, in order to integrally form a desired enlarged portion in the intermediate portion of the workpiece W having an outer diameter D ₀ and a wall thickness t, a pair of holding portions facing each other are separated by a predetermined interval L ₀ . The workpiece W is held in a state, and the axial pressure stress P is applied by moving at least one holding portion relatively closer to the other holding portion, and rotation around the workpiece and at least one holding. The portion is biased in a direction inclined with respect to the axis of the other holding portion, thereby causing the workpiece W to be rotated and bent at a bending angle θ to be generated inside the workpiece W between the two holding portions. In the shaft enlargement processing method of stopping the rotation and the shaft pressurizing state after straightening the workpiece W by bending back after cumulatively enlarging the convex portion, the thick portion of the workpiece W projecting length W _i to slit notch length h and the inner diameter side occurring , And carrying out under the conditions to obtain the enlargement portion shape of the inner diameter side to be h = 0 and _{W i} ≧ 0 becomes _{(L 0 / D 0) ≦} 0.8.
According to the second aspect of the present invention, in order to integrally form a desired enlarged portion at the intermediate portion of the workpiece W having an outer diameter D ₀ and a wall thickness t, a pair of holding portions facing each other are separated by a predetermined interval L ₀ . The workpiece W is held in a state, and the axial pressure stress P is applied by moving at least one holding portion relatively closer to the other holding portion, and rotation around the workpiece and at least one holding. The portion is biased in a direction inclined with respect to the axis of the other holding portion, thereby causing the workpiece W to be rotated and bent at a bending angle θ to be generated inside the workpiece W between the two holding portions. In the shaft enlargement processing method in which the workpieces W are straightened by bending back after the convex portions are cumulatively enlarged and then rotated and the shaft pressurization state is stopped, the width L and the diameter D after N rotations. Formula model that forms the enlarged part that becomes
Where ε ₀ is the average distortion in the circumferential direction when D / D ₀ = 2 (ε ₀ = ln (D / D ₀ ) = ln (2)), and N is the number of revolutions , N ₀ is a rotation time constant, and this rotation time constant N ₀ is
Where the bending angle dependence coefficient N ₀ ^* and the pressure stress dependence index α of the rotation time constant N ₀ are
And then, where D _i is the inner diameter of the inner diameter of the extending portion,
B _i is the overhang width of the inner diameter, so that when the desired enlarged portion (diameter D, width L) is formed, the shaft enlargement processing conditions (bending angle θ, axial pressure stress σ _c ) derived from these model equations ) To form the enlarged portion integrally .

In the invention of claim 1, when forming the enlarged portion in the intermediate portion of the workpiece W having the outer diameter D ₀ and the wall thickness t, an axial enlargement processing method is used, and the initial gripping interval L ₀ and the outer diameter D ₀ are set. It is assumed that the ratio is 0.8 or less. When the shaft enlargement process is performed under this condition, the inner diameter overhanging portion is in the plus direction, and the slit notch does not enter from the inner diameter surface. Therefore, after forming the enlarged portion, by performing an inner diameter process such as a turning process, a hollow shaft material with an integral flange having no defect portion can be obtained.
In the invention of claim 2, the processing conditions (bending angle θ, axial compressive stress σ _c ) for forming a desired enlarged portion can be derived by a mathematical model. Therefore, in actual work, there is an effect that the enlarged portion can be formed in the intermediate portion of the workpiece W without repeating the trial production for forming the desired enlarged portion (diameter D, width L).

In order to integrally form a desired enlarged portion in the intermediate portion of the workpiece W having an outer diameter D ₀ and a wall thickness t, the workpiece W is placed in a state where a pair of holding portions facing each other are separated by a predetermined interval L _0. Axial pressure stress P is applied by holding at least one holding part relatively close to the other holding part, and rotation around the workpiece and at least one holding part is moved to the other holding part. By biasing the workpiece W in a direction inclined with respect to the axis, the workpiece W is rotated and bent at a bending angle θ, and the convex portions generated on the inner side of the workpiece W between the holding portions are accumulated all around the circumference. After the enlargement, the workpiece W is straightened by bending back, and then in the shaft enlargement processing method in which the rotation and the shaft pressurization state are stopped under the condition of (L ₀ / D ₀ ) ≦ 0.8. Do.

In order to elucidate the deformation behavior when integrally forming the enlarged portion from the hollow shaft material in the present invention, the following experiment was conducted.
First, as a test material, a precision carbon steel pipe (OST) for hydraulic piping having an outer diameter D ₀ = 10 mm and a wall thickness t = 2 mm is used. Thickness t = 1 mm, 1.25 mm, 1.5 mm, 1.75 mm, 2 mm) was used as a test material. In addition, a D ₀ = 10 mm round bar of the same material was also used for comparison with the enlargement deformation behavior of the solid shaft material. For shaft enlargement processing experiments with large-diameter and thick-walled pipe materials, five types of hollow shafts with different wall thicknesses were obtained by processing the inner diameter using a cold-drawn steel bar (SGD400) receiving material with an outer diameter D ₀ = 31 mm. A material (wall thickness t = 6 mm, 7.5 mm, 9 mm, 11 mm, 12.5 mm) was used as a test material.

A shaft enlargement processing experiment was performed on each specimen using a shaft enlargement processing apparatus 1 as shown in FIG.
This processing apparatus mainly comprises a shaft rotation driving unit 2, a shaft pressing force adding unit 3, and a bending angle adding unit 4.
In addition, the tensile test was done with respect to each test material, and the obtained mechanical characteristic is shown in the following table.

Next, the experimental method will be described with reference to FIG.
First, in a state where the shaft rotation driving side chuck 5 and the shaft pressing side chuck 6 serving as a pair of holding parts are arranged on the same shaft, the specimen is mounted with a grip width l (see FIG. A).
Thereafter, the set axial pressure P was applied. A change in the gripping width of the time was measured and the initial value L ₀ of the length of the portion to be processed (see Diagram b).
Then, the shaft rotation drive side chuck 5 is biased to add a bending angle θ to the test material. Next, the rotation of the shaft is started and enlargement molding is performed. At this time, changes in the length L and the maximum outer diameter D of the workpiece in each machining process were continuously and automatically measured (see c and d).
Thereafter, when the target shaft diameter enlargement ratio (D / D ₀ ) is reached, the bending angle θ is returned to 0 ° and the rotation of the shaft is stopped (see FIG. E).

As the experimental conditions, in the specimen having an outer diameter D ₀ = 10 mm, the initial gripping width L ₀ = 12 mm and the axial pressure stress σ _c = 0.92σ _y , 0.97σ _y , 1.10σ _y , 1.20σ _y was added and the bending angle θ = 3 °, 4 °, 5 °, 6 ° was set for each axial pressure stress σ _c / σ _y normalized by the yield stress σ _y . Then, this experiment was performed at room temperature (25 ° C.) and in the atmosphere at a shaft rotation speed ω = 10 rpm.
For the test material having an outer diameter D ₀ = 31 mm, the initial grip width L ₀ = 10.5 to 25.2 mm, the axial pressure σ _c = 1.20σ _y , and the bending angle θ = 1 ° were set. Then, this experiment was performed at room temperature (25 ° C.) and in the atmosphere at a shaft rotation speed ω = 15 rpm.
The internal shape was observed by cutting in the axial direction, polishing the cut surface, and further etching.

FIG. 3 shows an outer diameter of a hollow shaft member having a wall thickness of t = 2 mm under processing conditions of axial pressure stress σ _c = 0.97σ _y , bending angle θ = 3 °, 4 °, 5 °, 6 °. The enlargement ratio D / D ₀ = 1.49 to 1.53 is processed, and the final shape of each specimen is shown in the appearance photograph. It can be seen that there is almost no difference in the final shape under any of the processing conditions.
FIG. 4 is a sectional view in the axial direction showing the change in the shape of the workpiece as the shaft rotational speed N increases in the machining process under the machining conditions of axial pressure stress σ _c = 0.97σ _y and bending angle θ = 5 °. This is shown in the photo. It can be seen that the enlarged portion is clearly formed as the rotational speed N increases. As the deformation behavior, the enlargement deformation proceeds while the members between the chucks 5 and 6 are shifted from the lantern shape to the barrel shape so as to be pushed at the ends of both chucks 5 and 6.
FIG. 5 shows a case where hollow shaft materials having different wall thicknesses were subjected to a machining experiment under processing conditions of axial pressure stress σ _c = 0.97σ _y and bending angle θ = 5 °. The change in shape is shown in the appearance photograph.
At any wall thickness, it became clear that the deformation behavior progressed from the lantern shape to the barrel shape so as to be pushed by the side surfaces of both chucks, and there was almost no difference in the final shape.

FIG. 6 shows axial enlargement deformation in a specimen having a wall thickness t = 2 mm, with bending pressure θ = 3 °, 4 °, 5 °, 6 ° as parameters at axial pressure stress σ _c = 0.92σ _y . The behavior, that is, changes in the shrinkage ratio L / L ₀ of the width of the workpiece and the enlargement ratio D / D ₀ of the shaft diameter are shown in relation to the rotational speed N.
FIG. 7 shows specimens having wall thicknesses t = 1 mm, 1.25 mm, 1.5 mm, 1.75 mm, and 2 mm under the processing conditions of axial pressure stress σ _c = 0.92σ _y and bending angle θ = 5 °. The shaft enlargement deformation behavior is shown. In either case, as the number of revolutions N increases, the width of the processed part decreases and the shaft diameter increases.
These shaft enlargement deformation behaviors can be summarized as follows: the shaft diameter enlargement behavior as the rotational speed N increases and the shrinkage behavior of the width of the work piece tend to saturate exponentially. As shown by the approximate curve in FIG.

In this shaft enlargement processing condition, when the enlargement rate D / D ₀ > 1.6, a saturation tendency of the enlargement rate appears, and the enlargement speed decreases, so the number of rotations required for the final processing rate increases. As a result, fatigue damage becomes a concern. Therefore, from such a viewpoint, the strain ε _{0 in the} equation (1) is the average strain in the circumferential direction when D / D ₀ = 2: ε ₀ = ln (D / D ₀ ) = ln (2) . N ₀ is a rotation time constant as a cycle parameter, and is determined so that an error with respect to the actually measured value (D / D ₀ , N) is minimized. After obtaining the equation (1) representing the hypertrophic deformation behavior of the shaft diameter, the shrinkage ratio L / L ₀ of the length of the workpiece is obtained by volume invariance. As can be seen from each of the approximate curves in FIGS. 6 and 7, both can be approximated well to the actual measured values of the contraction rate L / L ₀ and the enlargement rate D / D ₀ .

Also in the case of hollow shafts having the same wall thickness t, as in the case of solid shafts, the rotation time constant N ₀ depends on the bending angle θ and the axial pressure stress σ _c / σ _y , as shown in FIG. In any processing condition (θ, σ _c / σ _y ), it is well expressed by the following equation. Note that the bending angle dependence coefficient N ₀ ^* and the pressure stress dependence index α are both determined so that the error with respect to (N ₀ , σ _c / σ _y ) is minimized.

However, there is a relationship between the rotation time constant N ₀ and the bending angle θ as shown in FIG. 9 if the thickness is the same. The relationship between the bending angle dependence coefficient N ₀ ^* , the pressure stress dependence index α and the bending angle θ is shown in FIG.

here,
, Α ₀ ^* and n are material constants, both of which are determined so that the error with respect to (N ₀ ^* , θ) and (α, θ) is minimized.
Therefore, by substituting the equations (4) and (5) into the equation (3), the rotation time constant N ₀ can be expressed by the following equation as a uniform parameter of the machining conditions (θ, σ _c / σ _y ), and the hollow shaft It can be applied to the estimation of axial enlargement deformation behavior of wood.

Therefore, with respect to the influence of the wall thickness t of the hollow shaft material on the rotation time constant N ₀ which is a deformation behavior parameter in the process of shaft enlargement, the rotation time constant normalized with the axial pressure stress σ _c / σ _y
11 and 12 are arranged using the bending angle θ as a parameter. Incidentally, the vertical axis indicates the rotation time constant that scales the rotation time constant N ₀ of the hollow shaft member in rotation time constant N ₀ of solid shaft member, the outer radius D of the abscissa axis the thickness t _0/2 The wall thickness (2t / D ₀ ) normalized by. It shows the same behavior under different processing conditions and can be formulated by the following formula.

here,
Is a material constant. This tendency suggests that as the wall thickness t of the hollow shaft increases, the hollow shaft gradually approaches the shaft enlargement deformation behavior of the solid shaft.

FIG. 13 shows the relationship between D / D ₀ and (L / L ₀ ) (D / D ₀ ) ² in the shaft enlargement deformation process of the solid shaft material and the hollow shaft material. As indicated by the black circles in FIG. 13, in the case of a solid shaft material , (L / L ₀ ) (D / D ₀ ) ² = 1 suggests that the volume invariant holds. In the case of a hollow shaft material, it turns out that it differs from the deformation behavior of a solid shaft material.
That is, in the case of (L / L ₀ ) (D / D ₀ ) ² <1, it is suggested that the compression deformation of the shaft precedes and is faster. (L / L ₀ ) (D / D ₀ ) ² > 1 until D / D ₀ <1.34 as in the case of t = 1.0 mm because the bending rigidity is small and the outer diameter is This suggests that the increase is ahead. Thereafter, the shaft shifts to compressive deformation and proceeds rapidly.
The cause can be considered from the behavior of the bending moment M in the axial enlargement process of FIG. That is, in the lantern-shaped deformation process in FIG. 4, after the bending moment M exhibits a linear increase, it shifts to barrel-shaped deformation, and when the enlargement ratio D / D ₀ is saturated, the bending moment M is rapidly increased. Increase. This is because the compression ratio L / L _{0 in} this process only narrows the bellows gap, and therefore, precedes the enlargement ratio D / D ₀ as shown in FIG. 15 and shows rapid deformation. The thick solid line in FIG. 15 shows an ideal volume invariant deformation. Here, a difference in deformation mechanism appears between the hollow shaft member and the solid shaft member as shown in FIG. 13, but the volume invariance also holds.

FIG. 16 shows an example of estimation of deformation behavior (L / L ₀ , D / D ₀ ) in the process of shaft enlargement of a hollow shaft material (OST) having a wall thickness t = 2 mm. The curve in the figure is based on the processing conditions (θ, σ _c / σ _y ) = (5 °, 0.97), and uses the estimated value of the rotation time constant N _{0 in} equation (7), This is an estimated value calculated by equation (2), and the measured value can be estimated relatively well.
On the other hand, FIG. 17 shows estimations for the case of hollow shaft materials of t = 1 mm, 1.25 mm, 1.5 mm, 1.75 mm, and 2.00 mm. It was found that it can be estimated well even for test materials with different wall thicknesses.

When a shaft enlargement processing experiment was performed using a hollow shaft material, it was found that a slit notch was generated on the inner diameter side of the enlarged portion and also protruded to the inner diameter.
FIG. 18 shows a schematic sectional view after the shaft enlargement processing experiment. Here, W _i represents the inner diameter overhang length, and W _o represents the outer diameter overhang length. h represents the slit notch length in the thick part. L is the final width of the enlarged portion. The values of the slit notch length h, the inner diameter overhang length W _i, and the outer diameter overhang length W _o change according to changes in the processing conditions. After the axial enlargement processed shape of the hollow rotary shaft member, but of no length-out slit notch h also internal diameter projecting length W _i is ideal, that is axially enlarged working in practice, removed inside diameter overhang Since it can be processed, there is no problem if the slit notch length h = 0 and the inner diameter overhang length W _i ≧ 0.

Shaft enlargement processing with a pressing stress σ _c = 1.2σ _y , bending angle θ = 1 °, and wall thickness t = 9 mm for a hollow shaft material having an initial grip width L ₀ = 15.5 mm and 22.6 mm The experiment was conducted. FIG. 19 shows the change in the shape of the workpiece at each rotation speed N as an axial cross-sectional photograph.
From FIG. 19, the inner diameter overhanging portion is formed at the initial gripping interval L ₀ = 15.5 mm, but the inner diameter overhanging portion is not formed at the initial gripping interval L ₀ = 22.6 mm. In both cases, the internal shape up to 5 revolutions has grown to the final internal shape. In addition, it is apparent that the enlarged portion and the inner diameter overhanging portion grow as the rotational speed N increases. It became clear that the deformation behavior of the outer shape is not much different from the deformation behavior of the outer shape of the solid shaft material.

In addition, with respect to the hollow shaft material in which the inner diameter of the receiving material having the outer diameter D ₀ = 31 mm is expanded by drilling and the wall thickness t = 6 mm, 7.5 mm, 9 mm, and 11 mm, the pressing stress σ _c = 1. Processing experiments were performed in the range of the enlargement ratio D / D ₀ = 1.19 to 1.22 under the processing conditions of 2σ _y and bending angle θ = 1 °. The final shape after machining, the relationship between the normalized value of an outer diameter projecting length W _o of the scaled values and the inner diameter projecting length W _i with an initial diameter D ₀ of the wall thickness t in FIG. 20 Show.
As the influence of the wall thickness, the final enlarged portion width L is clearly increased as the wall thickness is increased. Further, when the wall thickness is 2t / D ₀ = 0.6 at the enlargement rate D / D ₀ = 1.19 to 1.22, the inner diameter overhanging portion length W _i is the longest. From these, it is clear that the inner diameter overhang length W _i also depends on the wall thickness t.

In the experiment on the influence of the wall thickness on the shaft enlargement shape, a test material having a wall thickness t = 9 mm having the largest standardized value at the outer diameter overhang length W _o of the inner diameter overhang length W _i was used. Under the processing conditions of pressure stress σ _c = 1.2σ _y and bending angle θ = 1 °, the initial grip width L ₀ = 10.5 mm to 25.2 mm and the grip width effect on the shaft enlargement portion shape changed Experiments on effects were conducted. FIG. 21 shows axial sectional photographs of the final shapes of the test materials.
Further, the normalized value of an outer diameter D ₀ of the initial gripping width L _0, the relationship between the normalized value of the wall thickness t of the scaled values and hypertrophic portion width L of the wall thickness t of the inner diameter overhang W _i Shown in FIG. Shape or a slit notch existence of internal diameter overhang seen to be dependent on the initial gripping width L _0. The enlarged portion, the initial gripping enlarged section width shorter width L ₀ is short, enlarged section width the longer the initial gripping width L ₀ is also revealed that longer.

FIG. 23 shows the axial enlargement deformation behavior of the test material having the initial grip width L ₀ = 14.7 and the thickness t = 9 mm under the axial pressure stress σ _c = 1.2σ _y , that is, the grip width. The relationship between the change in the shrinkage ratio L / L ₀ and the shaft diameter enlargement ratio D / D ₀ and the rotational speed N is shown. The shrinkage behavior of the grip width L accompanying the increase in the rotational speed N is expressed by the following equation in the same manner as the shrinkage behavior equation (equation (1)) for the solid shaft member.

Here, the strain ε ₀ was an average strain in the circumferential direction when D / D ₀ = 2: ε ₀ = ln (D / D ₀ ) = ln (2). N ₀ is a rotation time constant as a cycle parameter, and is determined so that an error with respect to the actually measured value (L / L ₀ , N) is minimized.
The change of the shaft diameter enlargement ratio D / D ₀ is expressed by the following equation using the volume invariant, assuming that the inner diameter does not change and only the outer diameter is enlarged from the equation (8).

As shown by the approximation curve in FIG. 23, shrinking behavior is well approximated error occurs in the enlargement ratio D / D _0. This is because there is actually an inner diameter overhanging portion.
When the enlargement rate D / D ₀ is predicted from the shape of the final-shaped inner diameter overhanging portion in consideration of the deformation behavior of the inner diameter overhanging portion, the change in the shaft diameter enlargement rate D / D ₀ is expressed by the following equation: in good agreement to the experimental results of the enlargement ratio D / D ₀ of the diameter.

Here, B _i is the width of the inner diameter overhang portion at the final shape, and the pressure stress dependent index α is also W ₀ / W _i at the final shape. Thus, the deformation behavior can be estimated by considering the deformation behavior of the inner diameter overhanging portion.
The relation between the width gripping and rotation time constant N ₀ in FIG. 24. According gripping width increases, the rotation time constant N ₀ increases, indicates that the deformation resistance is increased. This is the same tendency as the solid shaft material.

As described above, with the aim of expanding the application to the shaft enlargement processing method, a shaft enlargement processing experiment was tried for hollow shaft materials having different wall thickness t, and the plastic deformation behavior obtained for the solid shaft material was examined. As a result of examining the application of the model formula and the effects of shaft enlargement processing conditions (θ, σ _c / σ _y ) and wall thickness t, the following results were obtained.
First, the shaft enlargement deformation of the hollow shaft material is slightly different from that of the solid shaft material, and after the lantern-like deformation progresses, it first shifts to the barrel-shaped deformation, and the enlarged portion is formed.
And the deformation behavior in this shaft enlargement process can be formulated with the same mathematical model as in the case of a solid shaft material. That is, the processing conditions (bending angle θ, axial pressure stress σ _c / σ _y ) can also predict the effects of the axial pressure stress σ _c and the bending angle θ uniformly with only the rotation time constant N ₀ as one parameter. . In other words, the processing conditions for obtaining a desired enlarged portion can be appropriately selected.
Further, the shaft enlargement deformation of the hollow shaft material tends to increase the machining rotational speed, approach the deformation behavior of the solid shaft material, and increase the bending moment as the wall thickness t increases under the same processing conditions. I understand that.
The parameter N _Op (t) in the shaft enlargement deformation of the hollow shaft member having the wall thickness t can be converted into an equivalent parameter N _Ob (t) in the shaft enlargement deformation of the solid shaft member by the following equation.

Furthermore, the shape of the inner diameter overhang at atmospheric径肉thickness pipe is dependent on the thickness t and the initial grasp width L _0. Therefore, to find a width L ₀ suitable gripping for the thickness t, it is possible to eliminate-out slit notch.
Finally, by predicting the deformation behavior of the inner diameter overhanging portion from the final inner diameter overhanging portion shape, the outer diameter deformation behavior can be formulated with the same mathematical model.

Overall perspective view showing shaft enlargement processing device Machining process explanatory diagram showing the experimental method Photograph showing enlarged part shape with different bending angles Cross-sectional photo showing changes in enlarged portion shape with increasing number of rotations Photograph showing enlarged part shape due to different wall thickness Graph showing shaft enlargement deformation behavior at different bending angles Graph showing shaft enlargement deformation behavior at different wall thickness Graph showing the relationship between rotational time constant and axial pressure stress at different bending angles A graph showing the relationship between rotational time constant and bending angle at different axial pressure stresses A graph showing the relationship between the bending angle dependence coefficient and the pressure stress dependence index and the bending angle Graph showing the relationship between normalized rotational time constant and normalized wall thickness at different axial pressure stresses Graph showing the relationship between normalized rotation time constant and normalized wall thickness at different bending angles Graph showing the relationship between volume change rate and enlargement rate at different wall thicknesses Graph showing the relationship between bending moment and enlargement rate at different wall thicknesses Graph showing the relationship between compression rate and enlargement rate at different wall thicknesses Graph showing deformation behavior during shaft enlargement processing at different bending angles in hollow shaft material Graph showing deformation behavior during shaft enlargement processing at different wall thickness in hollow shaft material Cross-sectional schematic diagram after shaft enlargement processing in hollow shaft material Cross-sectional photograph showing changes in enlarged portion shape with increasing number of rotations at different wall thicknesses Graph showing the relationship between the standard value of the overhang and the standardized wall thickness Axial cross-sectional photograph of the final shape Explanatory drawing showing the effect of initial grip width Graph showing shaft enlargement deformation behavior of hollow shaft material Graph showing the relationship between rotation time constant and initial gripping interval

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Axis enlargement processing apparatus 2 Axis rotation drive part 3 Axis pressurizing force addition part 4 Bending angle addition part 5 Axis rotation drive side chuck 6 Axis pressure side chuck

Claims (2)

In order to integrally form a desired enlarged portion in the intermediate portion of the workpiece W having an outer diameter D ₀ and a wall thickness t, the workpiece W is placed in a state where a pair of holding portions facing each other are separated by a predetermined interval L _0. Axial pressure stress P is applied by holding at least one holding part relatively close to the other holding part, and rotation around the workpiece and at least one holding part is moved to the other holding part. By biasing the workpiece W in a direction inclined with respect to the axis, the workpiece W is rotated and bent at a bending angle θ, and the convex portions generated on the inner side of the workpiece W between the holding portions are accumulated all around the circumference. After the enlargement, the workpiece W is straightened by bending back, and then the slit notch length generated in the thick part of the workpiece W in the shaft enlargement processing method in which the rotation and shaft pressurization are stopped. h and the overhanging length W _i to the inner diameter side are h = 0 and W _i A shaft enlargement processing method, which is performed under the condition of (L ₀ / D ₀ ) ≦ 0.8 in order to obtain a shape of the enlarged portion on the inner diameter side that satisfies ≧ 0 . In order to integrally form a desired enlarged portion in the intermediate portion of the workpiece W having an outer diameter D ₀ and a wall thickness t, the workpiece W is placed in a state where a pair of holding portions facing each other are separated by a predetermined interval L _0. Axial pressure stress P is applied by holding at least one holding part relatively close to the other holding part, and rotation around the workpiece and at least one holding part is moved to the other holding part. By biasing the workpiece W in a direction inclined with respect to the axis, the workpiece W is rotated and bent at a bending angle θ, and the convex portions generated on the inner side of the workpiece W between the holding portions are accumulated all around the circumference. After the enlargement, the workpiece W is straightened by bending back, and then the enlarged portion having the width L and the diameter D is formed after N rotations in the shaft enlargement processing method in which the rotation and the shaft pressurization state are stopped. Formula model
Where ε ₀ is the average distortion in the circumferential direction when D / D ₀ = 2 (ε ₀ = ln (D / D ₀ ) = ln (2)), and N is the number of revolutions , N ₀ is a rotation time constant, and this rotation time constant N ₀ is
Where the bending angle dependence coefficient N ₀ ^* and the pressure stress dependence index α of the rotation time constant N ₀ are
And then, where D _i is the inner diameter of the inner diameter of the extending portion,
B _i is the overhang width of the inner diameter, so that when the desired enlarged portion (diameter D, width L) is formed, the shaft enlargement processing conditions (bending angle θ, axial pressure stress σ _c ) derived from these model equations The shaft enlargement processing method for a metal pipe, wherein the enlarged portion is integrally formed by the following method.