JP2003004410A - Device and method for fitting strain gauge inside tubular body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and a method for fitting a strain gauge at a specified position inside a tubular body, so that strain is measured accurately during tubulation. SOLUTION: This device is used to fit a strain gauge inside a tubular body, and it is provided with a bar-like grip which is provided with such a guide roll on its tip that rolls in the inside of the tubular body in its lengthwise direction, a slide lever which is slidable in parallel to and along the grip, and a strain gauge pedestal, in which its one end is connected with the grip and the other end is connected with the slide lever, and which rises, when a distance between both ends becomes small and is lowered when it becomes large. Therefore, strain measurement can be made continuously during molding in a roll stand, contributing to future roll forming technology.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for attaching a strain gauge to an inner surface of a tubular body such as a steel pipe that enables highly accurate strain measurement.

[0002]

2. Description of the Related Art Recently, a technique of forming by applying water pressure to a tubular body, for example, an inner surface of a steel pipe, has become widespread.
What is important when forming by hydraulic pressure is that no distortion remains in the steel pipe before forming. If strain remains, cracking tends to occur during processing. Therefore, there is a strong demand for a pipe forming method in which no distortion remains. For that purpose, it is necessary to accurately measure the strain of the steel pipe that occurs during the pipe making, and to search for a pipe making method in which the strain is small, and a technique for accurately measuring the strain during the pipe making is important. .

Conventionally, the scribed circle method or the strain gauge measuring method has been used as a method for measuring the amount of strain. The scribed circle method is a method in which a scribed circle is transferred to the surface of a tube, the amount of change in its shape is measured after processing, and the strain is calculated. On the other hand, the strain gauge measuring method is a method in which a strain gauge is attached to the surface of a tube, the amount of change after processing is measured, and the strain is calculated.

In order to measure the strain in the middle of pipe making by a roll or the like, it is necessary to attach a strain gauge to the inner surface of the pipe.
Further, it is more accurate to measure the position where the strain gauge is attached at a position distant from the end of the pipe, which is the stationary part. Since the scribed circle method can be applied to the outer surface of the pipe, it is possible to measure the strain at the center away from the pipe end,
Since the amount of strain is determined by measuring the amount of change in the scribed circle, the measurement accuracy is at most 0.001 mm, which is insufficient. In comparison, a strain gauge has a measurement accuracy of 0.0000001 mm, which is sufficient. Conventionally, as a method of attaching the strain gauge to the inner surface of the pipe, there has been a method of attaching the strain gauge to a rubber balloon, inserting the strain gauge into the pipe, inflating the balloon at a predetermined position, and attaching the strain gauge to the pipe.

[0005]

However, in the above method of attaching a strain gauge using a balloon, when the pipe cross section is a perfect circle, the strain gauge can be evenly contacted with the inner surface of the pipe and the strain gauge can be attached at any position. However, if the tube cross section is not a perfect circle such as an ellipse, it cannot be evenly contacted and cannot be attached. There was a problem. An object of the present invention is to provide a strain gauge mounting device and a mounting method capable of accurately measuring even the strain on the inner surface of the tubular body away from the end portion.

[0006]

The gist of the present invention is (1) a device for attaching a strain gauge to the inner surface of a tubular body, the guide guard roll rolling the inner surface of the tubular body at the tip of the device in the longitudinal direction of the tubular body. With a rod-shaped grip with a
A strain gauge having a structure in which a slide lever that is slidable along the grip in parallel with the grip and one end is connected to the grip and the other end is connected to the slide lever, and rises when the distance between both ends is narrowed and descends when the space is widened. An apparatus for attaching a strain gauge to an inner surface of a tubular body, which has a pedestal. (2) A tubular body is fixed, and then a strain gauge coated with an adhesive is lightly fixed to the strain gauge pedestal with a double-sided tape or the like, and the device is fixed until the strain gauge pedestal is positioned at a predetermined position of the steel pipe. A method for attaching a strain gauge to an inner surface of a tubular body, which comprises inserting the strain gauge into the inner surface of the tubular body by inserting it into a steel pipe, pulling a grip, or pushing a slide lever. Is.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a strain gauge attaching apparatus which is excellent in convenience of the present invention will be described. INDUSTRIAL APPLICABILITY The present invention is an apparatus and method capable of securely attaching a strain gauge to a portion apart from a pipe end, that is, a pipe inner surface substantially at the center in the pipe axial direction. The target size of the pipe is, for example, an outer diameter of about 100 mm
Hereafter, the length is about 2000 mm. Conventionally, since the strain gauge is attached by hand, it is not possible to insert the hand into the steel pipe with such a size, and the strain gauge cannot be attached to the inner surface of the pipe.

Therefore, according to the present invention, the scale of the strain gauge mounting portion on the inner surface of the steel pipe, the plating layer and the like are removed and polished by using a grinder, sandpaper or the like, and the steel pipe wiped with a solvent such as acetone is fixed, and then the steel pipe is fixed. A strain gauge with adhesive applied to the surface is fixed to the jig with double-sided tape, inserted to the prescribed inner surface of the steel pipe, and a grip is pulled to attach the strain gauge to the inner wall of the steel pipe by the action of a spring. Invented a method and a device for sticking a gauge.

The mounting method and device will be described in detail below. First, the polishing and cleaning of the inner surface of the steel pipe will be described. The length that reaches the center of the table of the table grinder in the tube axis direction (about 1100 mm when the tube length is 2000 mm)
Attach sandpaper to the end of the long mandrel. Insert the long mandrel into the center of the inner surface of the steel pipe, and use a grinder at the specified strain gauge attachment position to scale the inner surface of the steel pipe.
Remove the plating layer. Next, the inner wall of the steel pipe inner surface of the portion polished by the grinder on the inner surface of the steel pipe is washed with gauze in which the tip of the long mandrel is impregnated with a solvent such as acetone.

Next, a strain gauge mounting device and method will be described with reference to FIGS. The polished and washed steel pipe 1 is fixed to the jig 2, and the height of the mounting device is adjusted by the device insertion height adjuster 3 so that the device can be placed inside the steel pipe 1. Next, the stopper 4 for determining the strain gauge attachment location is fixed on the slide lever 10 to determine the strain gauge attachment location.

When the grip 5 is pushed inward, the legs at both ends of the strain gauge pedestal 6 are opened so that the strain gauge pedestal 6 is lowered, and the grip 5 is pushed in advance to lower the strain gauge pedestal 6 (see FIG. 2). (A)). A strain gauge adhesive is applied to the upper surface of the strain gauge 9, and the strain gauge 9 is attached to the lower surface of the strain gauge 9 with a double-sided tape. The stopper 4 is installed in advance on the slide bar 10 or the like so that the strain gauge 9 stops at a predetermined position of the tube so that the gauge position stops at a desired position when the device is inserted into the tube. Then, while holding the grip 5 in the pipe, that is, the pedestal 6
Insert it into the inner surface of the steel pipe from the position of the guide and guide roll 8 while lowering it, and stop the insertion when reaching the position of the stopper 4. Next, as shown in FIG. 2B, the grip 5 is pulled toward the front, and the strain gauge pedestal 6 is lifted by the action of the strain gauge lifting auxiliary springs 7 provided at the mounting positions at both ends of the strain gauge pedestal 6. Then, the strain gauge 9 is attached to the inner wall of the steel pipe. In that state, hold for about 1 minute, push in the grip 5, lower the strain gauge pedestal 6 again, and pull out the device from the steel pipe 1.

The guide guide roll 8 attached to the tip of the apparatus is preferably provided with a groove. The lead wire of the strain gauge is designed to fit in this groove so that the lead wire can be inserted and removed without cutting the lead wire when the device is taken in and out. When attaching strain gauges at multiple points in the pipe circumferential direction,
The entire jig may be rotated at a predetermined angle while the device is fixed by the device insertion height adjuster 3, and the device may be attached in the same manner.

[0013]

[Example] Four continuous triaxial strain gauges were attached in the tube circumferential direction at the central portion of a tube having a length of 2000 mm and an elliptical cross section to measure the continuous strain on the inner surface of the tube during molding on a roll stand. The results are shown in Table 1. From Table 1, in the present invention, highly accurate measurement results were obtained even if the cross-sectional shape of the tube was elliptical. On the other hand, according to the air-rubber balloon method, when the tube cross section was elliptical, the strain gauge could not be attached properly and measurement was impossible. Further, the scribed circle method has not been able to obtain the measurement accuracy up to a predetermined level.

[0014]

[Table 1]

[0015]

With the above-described mounting apparatus and method according to the present invention, continuous strain measurement at the time of molding on a roll stand can be measured with high accuracy, and this can greatly contribute to the future development of roll forming technology.

[Brief description of drawings]

FIG. 1 is an overall view of the present invention, showing a state in which a steel pipe is fixed to a jig.

2A and 2B are enlarged views of the tip of the jig, in which FIG. 2A shows a state where the jig is inserted into the pipe, and FIG. 2B shows a state where the jig inserted into the pipe attaches a strain gauge.

[Explanation of symbols]

1: Test steel pipe 2: Steel pipe fixing jig 3: Device insertion height adjuster 4: Sticking position confirmation stopper 5: Grip 6: Strain gauge pedestal 7: Strain gauge lifting spring 8: Information guide roll 9: Strain gauge 10: Slide bar

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Mukai             1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel shares             Company Kimitsu Works (72) Inventor Hideki Takeda             1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel shares             Company Kimitsu Works (72) Inventor Shinya Sakamoto             1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel shares             Company Kimitsu Works (72) Inventor Daigo Sumimoto             1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel shares             Company Kimitsu Works F term (reference) 2F063 AA25 BA30 BD12 CA11 DA02                       EC03 EC24 ZA01

Claims (2)

[Claims] 1. A device for attaching a strain gauge to the inner surface of a tubular body, comprising a rod-shaped grip having a guide guard roll at the tip of the device for rolling the inner surface of the tubular body in the longitudinal direction of the tubular body, and the grip. A slide lever that can be slid along the grip in parallel, and a strain gauge pedestal that has a structure in which one end is connected to the grip and the other end is connected to the slide lever, and rises when the distance between both ends becomes narrower and descends when the gap widens. An apparatus for attaching a strain gauge to an inner surface of a tubular body, which is characterized by having. 2. A tubular body is fixed, and then a strain gauge coated with an adhesive is lightly fixed to the strain gauge pedestal with a double-sided tape or the like, and the strain gauge pedestal is placed at a predetermined position of a steel pipe. A method for attaching a strain gauge to an inner surface of a tubular body, wherein the strain gauge is attached to the inner surface of the tubular body by inserting the device into a steel pipe, pulling a grip, or pushing a slide lever.