JP2017089813A - Vibration controlled steel pipe and method for changing natural frequency of steel pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration controlled steel pipe capable of preventing noise or damage or the like caused by vibration in view of restriction against transmittance of vibration and a method for changing natural frequency of the steel pipe.SOLUTION: This invention relates to a vibration controlled steel pipe 1 featuring that its outer peripheral surface has a distribution of several recesses 3 and an interface length of a recess per unit area is in a range of 0.4 to 0.85 mm. Arrangement of recesses at the surface of the steel pipe 1 causes its natural frequency to be changed in respect to that of its original pipe. Accordingly, setting this natural frequency appropriately to such a natural frequency as one not producing any resonance enables this pipe to be changed into a vibration controlled steel pipe. Further, since its natural frequency becomes smaller than that of its original pipe in a range of 0.4 to 0.8 mm of an interface length per unit area of the recess, its vibration transmissibility also becomes low and vibration is hardly transmitted to it.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a steel pipe having damping properties and a method for changing the natural frequency of the steel pipe.

A plurality of steel pipes are connected in a vehicle engine, an exhaust gas member, or the like. Such a steel pipe may generate vibration due to the vibration of the engine body or the influence of a fluid flowing inside the steel pipe.
When the vibration is generated, the vibration is transmitted to the inside of the steel pipe where the vibration is generated or to another connected steel pipe or other member. And if a predetermined condition overlaps, it will resonate between other connected steel pipes and other members.
When vibration is transmitted and resonance occurs, the vibration is amplified, noise is generated, and the connecting portion of the steel pipe, the steel pipe itself, and other members may be damaged.
As a method for preventing noise or damage due to vibration, suppression of vibration generation, avoidance of resonance, suppression of vibration transmission, and the like can be considered.

  For example, to suppress the occurrence of vibration, a technique has been proposed in which a tubular formed body made of a foam having a cavity inside is disposed inside a steel pipe, and the vibration of the structure due to an impact applied from the outside is suppressed. (See Patent Document 1). Moreover, the technique which suppresses a vibration by attaching a support apparatus to a steel pipe is also proposed (refer patent document 2).

JP-A-9-189340 JP-A-60-81588

However, the technology for suppressing the occurrence of these vibrations requires additional members such as a cylindrical formed body and a supporting device, which requires manufacturing costs. Furthermore, as for the steel pipe of patent document 1, the thickness of a steel pipe increases by the part of a cylindrical formation body. In patent document 2, the space which arrange | positions a support apparatus is required.
It is an object of the present invention to provide a steel pipe having damping properties and a method for changing the natural frequency of the steel pipe that can prevent noise and breakage due to vibration from the viewpoint of suppressing vibration transmission.

Generally, when a certain vibration is applied to the steel pipe and the plate thickness is the same, the natural frequency increases as the outer diameter of the steel pipe decreases.
When the concave portions are distributed in the raw tube, the outer diameter of the portion where the convex portion is provided is not different from the outer diameter of the raw tube, but the outer diameter of the portion where the concave portion is provided is larger than the outer diameter of the raw tube. It is getting smaller.
For this reason, it is expected that the natural frequency of the steel pipe in which the concave portions are distributed in the raw pipe is larger than the natural frequency of the raw pipe.

However, the present inventors conducted intensive studies and changed the recess boundary length L2 per unit area.
(1) When L2 is small, the natural frequency of the steel pipe increases. This means that an outer diameter reduction element (concave portion) is added to the surface of the steel pipe. In this case, the change is expected as described above.
(2) Under a condition where L2 is larger than a certain L2, the natural frequency starts to decrease. This change is a newly discovered finding.
(3) When L2 further increases, the natural frequency starts to increase. This is the expected change as described above.
As described above, when the plurality of concave portions are distributed in the raw tube, the present inventors make the natural frequency smaller than that of the raw tube when the boundary length per unit area of the plurality of concave portions is within a predetermined range. Found that you can. When the natural frequency is small, the vibration transmissibility tends to be small. If the vibration transmissibility decreases, vibration transmission is suppressed.

  That is, the present invention is a steel pipe having vibration damping properties in which a plurality of recesses are distributed on the outer peripheral surface, and the boundary length of the recesses per unit area is 0.4 mm to 0.85 mm.

  It is preferable that the ratio t1 / t2 of the thickness t1 in the concave portion to the thickness t2 other than the concave portion is 0.5 to 0.8.

  Moreover, this invention is a change method of the natural frequency of a steel pipe which changes the natural frequency of the said steel pipe by forming a some recessed part in the outer peripheral surface of a steel pipe.

  In the changing method, it is preferable that the boundary length of the recess is 0.4 to 0.85 mm per unit area.

  ADVANTAGE OF THE INVENTION According to this invention, the change method of the natural frequency of the steel pipe which has the damping property which can prevent the noise, damage, etc. by vibration from a viewpoint of transmission suppression of vibration and a steel pipe can be provided.

It is a perspective view of the steel pipe which has damping property concerning an embodiment. It is an expanded sectional view of the steel pipe of FIG. It is a figure which shows the pay-out reel, the two-high rolling mill, and the take-up reel which are included in the steel pipe manufacturing apparatus having vibration damping properties of the embodiment. It is a figure which shows the pipe making machine contained in the manufacturing apparatus of the steel pipe which has damping property of embodiment. It is a figure explaining the measuring method of a natural frequency. It is a figure which shows the position of the vibration sensor attached to the steel pipe. It is a figure which shows an excitation position. It is a figure explaining the flow of the measuring method of the natural frequency of a steel pipe. It is a graph which shows the natural frequency of the measured steel pipe.

FIG. 1 is a perspective view of a steel pipe 1 having vibration damping properties according to an embodiment of the present invention. FIG. 2 is a developed sectional view of the steel pipe 1 of FIG.
As shown in the drawing, the steel pipe 1 according to the embodiment has a convex portion 2 having a thickness t2 and a concave portion 3 having a thickness t1 formed by forming a groove 5 on the outer surface of the steel pipe 1.
The grooves 5 of the embodiment are formed in a plurality of first grooves 5a that are formed in a spiral shape with respect to the axis A of the steel pipe 1 and in a spiral shape that is opposite to the first grooves 5a with respect to the axis A. And a plurality of second grooves 5b parallel to each other.
By the first groove 5 a and the second groove 5 b, rhomboid convex portions 2 (thick portions) are formed on the surface of the steel pipe 1. However, the shape of the convex part 2 and the recessed part 3 (thin wall part) is not limited to this shape, Other shapes may be sufficient.
The material of the steel pipe is preferably stainless steel, and in particular, a steel pipe made of ferritic stainless steel or austenitic stainless steel is preferred.

Next, the manufacturing apparatus 100 of the steel pipe 1 of embodiment is demonstrated. 3 and 4 are views showing a steel pipe manufacturing apparatus having vibration damping properties according to the embodiment.
The steel pipe 1 manufacturing apparatus 100 includes a pay-out reel 21, a two-high rolling mill 22, a take-up reel 23, and a pipe making machine 24.
FIG. 3 is a view showing the payout reel 21, the two-high rolling mill 22, and the take-up reel 23. FIG. 4 is a view showing the pipe making machine 24.

  The two-high rolling mill 22 includes a pair of rolling rolls 12 and 12 '. The upper rolling roll 12 has a concavo-convex shape formed by etching. The lower rolling roll 12 'is a flat roll that is not provided with an uneven shape.

The pipe making machine 24 includes a payout reel 25, a bending part 13, and a pipe making part 14.
The bending part 13 is provided with a plurality of pairs of bending rolls 15 arranged so as to sandwich the steel strip 61 from above and below. The pipe making unit 14 includes a pipe making roll 16 and a pipe making roll 17. The pipe making rolls 16 are a plurality of pairs of rolls arranged so as to sandwich the steel strip 61 that is a raw material of the steel pipe 1 from the left-right direction. The pipe making roll 17 is a plurality of pairs of rolls arranged so as to sandwich the steel strip 61 from above and below.

Next, the manufacturing method of the steel pipe 1 of this embodiment using the said manufacturing apparatus 100 is demonstrated.
First, the coil 10 around which the steel strip 11 with no irregularities as the original plate is wound is set on the delivery reel 21.
Next, the steel strip 11 is delivered from the delivery reel 21 and fed into the two-high rolling mill 22.
In the two-high rolling mill 22, the steel strip 11 is reduced by a pair of rolling rolls 12 and 12 ′.
Thereby, the uneven | corrugated shape currently formed in the upper rolling roll 12 is transcribe | transferred to the surface of the steel strip 11, and the steel strip 61 with which the unevenness | corrugation was provided is manufactured.
By winding this around the take-up reel 23, the coil 60 of the steel strip 61 provided with irregularities is obtained.
A rolling mill other than the two-high rolling mill 22 can be used for manufacturing the coil of the steel strip 61.

Next, the coil 60 of the steel strip 61 is set on the delivery reel 25 of the pipe making machine 24 shown in FIG.
Then, the steel strip 61 is paid out from the pay-out reel 25, and is gradually formed into a tubular shape through the bending portion 13 and the pipe forming portion 14.
Finally, the steel pipe 1 provided with irregularities is manufactured by welding the butt portions which are both ends of the steel strip 61.

Here, the length L2 per unit area of the boundary (edge) of the recess 3 formed on the surface of the manufactured steel pipe 1 is a range S of the length W on the surface of the steel pipe 1 as shown in FIG. Is a value obtained by dividing the total length L (mm) of the boundary 2a of the recess 3 existing in the area by W × 2πr (r: radius of the outer surface of the steel pipe 1) (mm ² ) which is the area of the range S.

L2 = L / (W × 2πr)

Hereinafter, this is referred to as a recess boundary length L2 per unit area.
The reason for selecting the recess boundary length L2 is that it focuses on the ratio (degree) of unevenness on the outer surface, and as an index for evaluating the ratio, the length of the boundary that separates the recess and the protrusion A recess boundary length L2 was selected.
Since the concave boundary is also a convex boundary, the concave boundary length L2 is the same length as the convex boundary length.
It should be noted that the range S for obtaining L2 is selected broadly so that the selected range S does not cause variations in the number of irregularities included therein. If the unevenness formed on the surface of the steel pipe 1 is not uniform, the recess boundary length L2 per unit area in the plurality of ranges S may be measured, and the average thereof may be obtained.
Moreover, this recessed part boundary length L2 can be adjusted by changing the uneven | corrugated shape currently formed in the rolling roll 12 of the upper side of the two-high mill 22.

  Further, the ratio t1 / t2 (hereinafter referred to as the plate thickness ratio) of the thickness t1 of the concave portion 3 and the thickness t2 of the convex portion 2 shown in FIG. 2 is adjusted by changing the rolling load of the two-high rolling mill 22. it can.

Hereinafter, effects and features of the steel pipe 1 manufactured by the manufacturing apparatus 100 and the manufacturing method described above will be described.
In the embodiment, the material is SUS409 made of ferritic stainless steel, the recess boundary length L2 per unit area is four types A, B, C, and D shown in Table 1 below, and the plate thickness ratio t1 / t2 is below The steel pipe 1 which is a total of 16 types of 4 types of a, b, c, and d shown in Table 2 was manufactured.

  Further, the material is SUS304 made of austenitic stainless steel, and the recess boundary length L2 per unit area is four types A, B, C, and D shown in Table 1 below, and the plate thickness ratio t1 / t2 is one type. A total of four types of steel pipes 1 with b (58%) were produced.

The steel strips of SUS409 and SUS304 both have a thickness of 1.2 mm and a width of 94.2 mm. Since the width of these steel strips is 94.2 mm, the outer diameter of the manufactured steel pipe 1 is 30 mm. The rolling load in the two-high rolling mill 22 is 100 to 200N. The shape of the manufactured unevenness is the shape shown in FIG. 1, the thickness t1 of the concave portion 3 is 0.5 to 1.0 mm, the thickness t2 of the convex portion 2 is 1.2 mm, and the size of the convex portion is shown in Table 1. As shown.
The recess boundary length L2 per unit area was calculated by measuring a diagonal line with calipers, and the thickness t1 of the recess 3 and the thickness t2 of the protrusion 2 were measured with a micrometer.
In addition, the material, size, etc. of the steel pipe 1 of this invention are not limited to this.

  Next, the natural frequency of the manufactured steel pipe 1 was measured. FIG. 5 is a diagram for explaining a method of measuring the natural frequency. As shown in the drawing, the steel pipe 1 was suspended from a tripod 31 with a wire 32.

FIG. 6 is a diagram showing positions 33A and 33B of the vibration sensor 33 attached to the steel pipe 1. As shown in FIG. As shown in the figure, vibration sensors 33 were attached to a position 33A of 75 mm and a position 33B of 231 mm from the lower end of the steel pipe 1 with a cyanoacrylate adhesive.
Then, a position 89 mm from the lower end (excitation position 34) was vibrated with an impulse hammer 37, and vibration was measured with a vibration sensor 33.

  FIG. 7 is a diagram showing the vibration position 34. The vibration position 34 was set at two locations, a position 34a of the welded portion of the steel pipe 1 and a position 34b rotated 90 degrees from the welded portion 1a. The position of the vibration sensor 33 was a position rotated 180 degrees from the vibration position 34. That is, as shown in FIG. 7, when the vibration of the impulse hammer 37 is at the vibration position 34a, the position of the vibration sensor 33 is 33Aa and 33Ba, and when the vibration of the impulse hammer 37 is at the vibration position 34b, The positions are 33Ab and 33Bb.

FIG. 8 is a diagram for explaining the flow of the method for measuring the natural frequency of the steel pipe 1.
In addition, Table 3 below shows the measurement-use equipment used.

As shown in FIG. 8, the vibrations measured by the vibration sensors 33A and 33B were amplified by vibration amplifiers 35A and 35B, and the natural frequency was determined by the frequency analyzer 36 based on the peak in the power spectrum waveform.
In addition, the variation in the measured value among the positions 33Aa, 33Ab, 33Ba, and 33Bb of the vibration sensor 33 and the variation in the measured value depending on how the vibration sensor is attached were in the range of ± 2 in terms of natural frequency.

  FIG. 9 is a graph showing the measured natural frequency of the steel pipe 1. For comparison, the graph also shows the measurement result of the natural frequency of the raw pipe not formed with unevenness. As shown in FIG. 9, the steel pipe 1 of this embodiment has the following characteristics.

(1) The natural frequency of the steel pipe 1 (steel pipes A, B, C, and D) according to the present embodiment in which unevenness is provided on the surface is changed with respect to the raw pipe.
When members having close natural frequencies (steel pipe 1 and other steel pipes, steel pipe 1 and other members, etc.) are connected, resonance occurs. Therefore, in order to prevent resonance, members having different natural frequencies may be connected.
However, the natural frequency varies depending on the length, material, diameter, thickness, etc. of the steel pipe, but since the length and material are often determined by other factors, it is difficult to change the natural frequency freely. is there.
As for the steel pipe 1 of this embodiment, the unevenness | corrugation is provided to the surface and the natural frequency is changed with respect to the elementary pipe. By setting this natural frequency to a natural frequency at which resonance does not occur as appropriate in relation to other members, it is possible to impart damping properties to the steel pipe 1.

(2) When the boundary length L2 per unit area of the concave portion 2 provided on the surface of the steel pipe 1 is in the range of 0.4 to 0.8 mm, the natural frequency of the steel pipe 1 is greater than the natural frequency of the raw pipe. Is also getting smaller.
Generally, when a certain vibration is applied to the steel pipe and the plate thickness is the same, the natural frequency increases as the outer diameter of the steel pipe decreases. In this embodiment, the unevenness | corrugation is formed by forming the groove | channel 5 in a base tube. Accordingly, the outer diameter of the portion where the convex portion 2 is provided is not different from the outer diameter of the raw tube, but the outer diameter of the portion where the concave portion 3 is provided is smaller than the outer diameter of the raw tube. For this reason, the natural frequency of the steel pipe 1 was expected to be larger than the natural frequency of the raw pipe.

However, in the present embodiment, as described above, the natural frequency of the steel pipe 1 is smaller than that of the raw pipe when the recess boundary length L2 per unit area is in the range of 0.4 to 0.8 mm. I understood.
The reason is not clear. Different vibrations are generated in the convex portion 2 and the concave portion 3, and when the vibration is generated in the range where the concave portion boundary length L2 per unit area is 0.4 to 0.8 mm, the vibration in the convex portion 2 is It is presumed that the natural frequency has been reduced by canceling out the vibrations in the recess 3.

  Generally, when the natural frequency is small, the vibration transmissibility tends to be small. If the convex portion 2 is formed on the surface of the steel pipe 1 in the above range where the natural frequency is small (0.4 ≦ the concave boundary length L2 ≦ 0.8 per unit area), the natural frequency is higher than that of the base tube. Therefore, the vibration transmissibility is also reduced. Therefore, the steel pipe 1 having a vibration damping property in which vibration is difficult to be transmitted can be manufactured by forming the convex portion having the concave portion boundary length L2 ≦ 0.8 per unit area.

(3) As clearly shown when the recess boundary length L2 per unit area is 0.65 mm (graph indicated by a circle in FIG. 9), the plate thickness ratio t1 / t2 is 0.5-0. In the range of 8, the natural frequency decreases. Further, the thickness ratio t1 / t2 is particularly reduced in the range of 0.60 to 0.75.
Therefore, if the steel pipe 1 is manufactured in the range of 0.4 ≦ recess boundary length L2 ≦ 0.8 per unit area and 0.5 ≦ plate thickness ratio t1 / t2 ≦ 0.8, the natural frequency And the effect of reducing the vibration transmissibility can be further increased.

(4) According to the example in which t1 / t2 is 0.58, the same tendency is shown even if the materials are different. Therefore, it is considered that the feature of the present invention does not depend on the materials.

L2 Convex part boundary length 1 Steel pipe 2 Convex part 2a Boundary 3 Concave part 5 Groove 10 Coil 11 Steel strip 12 Rolling roll 13 Bending part 14 Pipe making part 15 Roll 16 Pipe making roll 17 Pipe making roll 21 Dispensing reel 22 Step rolling machine 23 Take-up reel 24 Pipe making machine 25 Dispensing reel 31 Tripod 32 Wire 33 Vibration sensor 34a Position 35A Vibration amplifier 35B Vibration amplifier 36 Impulse hammer 36 Frequency analyzer 60 Coil 61 Steel strip

Claims (4)

A plurality of recesses are distributed on the outer peripheral surface,
The boundary length of the recess per unit area is 0.4 mm to 0.85 mm.
Steel pipe with damping properties. The ratio t1 / t2 of the thickness t1 of the steel pipe to the thickness t2 other than the concave portion is 0.5 to 0.8.
A steel pipe having vibration damping properties according to claim 1. Changing the natural frequency of the steel pipe by forming a plurality of recesses on the outer peripheral surface of the steel pipe;
How to change the natural frequency of a steel pipe. The boundary length of the recess is 0.4 to 0.85 mm per unit area.
The method for changing the natural frequency of a steel pipe according to claim 3.

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