JP4237387B2 - Stress release device for residual strain and residual stress measurement - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
This invention is capable of greatly damaging the strain and stress remaining on the surface of all solid objects existing in nature (ground, bedrock, trees, metal members, non-metal members, living organisms and cadaver skeletons, etc.) The present invention relates to a method for measuring residual strain / residual stress to be measured and a stress release device for residual strain / residual stress measurement used for that purpose.
[0002]
[Prior art]
Conventionally, there are the following methods for measuring residual strain / residual stress by drilling or cutting in the vicinity of a strain measuring device installed in a target object.
a) A method of drilling by drilling or shot peening in the vicinity of a plurality of appropriately arranged strain gauges, and is generally called a hold-rilling method. (ASTM DESIGNATION D837-95)
b) A method of releasing stress by surrounding a suitably arranged strain gauge by using a concrete cutter or the like and enclosing it into a polygonal shape. (Civil Engineering Papers No.585 / V-38 (1998, 2) p.11-16)
c) A method of releasing stress by surrounding a properly arranged strain gauge by making a circular cut with a core cutter or the like. However, strain measurement corresponds to a so-called disconnection / intermittent method in which the work is interrupted and then the gauge is connected (Structural Engineering Papers Vol.42A (1996, 3) p333-340, Experimental Techniques, Vol. 16 (5) (1992) p17-24, RAM, Vol. 4 (1988) p5-10).
[0003]
[Problems to be solved by the invention]
However, the above-described conventional residual strain measuring method has the following problems.
A) Because the hold-rilling method uses stress concentration and the strain gauge is larger than the drilling diameter, it is difficult to accurately measure the residual strain value, and the drilling position is accurate. Careful attention is required. In addition, complicated and advanced theoretical analysis results on stress concentration mediated by physical properties such as elastic, viscoelastic, and inelastic properties of an object are required.
B) When a concrete cutter is used, the periphery cannot be cut at the same time, which is troublesome and it is impossible to uniformly release stress. Furthermore, the current function of the object to be measured is drastically reduced.
C) When a normal core cutter is used, the strain measuring device is confined within the space of the core bit, and measurement data cannot be taken out of the core bit during operation, so continuous strain measurement is impossible. Also, in order to measure the released strain and stress, it is necessary to stop the operation of the core cutter, pull out the bit, and then connect the strain measurement device to the strain and stress display device to perform measurement. Measurement accuracy is significantly reduced.
In addition, in a normal core cutter, the core cutter's legs are drilled in advance on the surface of the object to be measured or on a rigid surface such as a floor surface, a wall surface, or a ceiling surface in the vicinity thereof, or on a rigid base joined to them. However, if it is not desirable to damage the target object such as bolt holes, or if it is difficult to secure a rigid surface or rigid base, etc., the stress can be released at any position. Is very difficult to do.
[0004]
The present invention solves the above-described various conventional problems, and is capable of quantitatively measuring the residual strain / residual stress of any solid object in a simple, rapid and accurate manner. The purpose of this is to propose a stress relief device for measuring the residual strain and residual stress used therefor.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the residual strain / residual stress measuring method according to the present invention is provided with a device capable of measuring strain / stress on the surface of the object to be measured, and the outer periphery of the device is circular. In addition, the core drill cutter has a mechanism capable of making incisions at the same depth and mounting it on a rigid base, holding it by magnetic force, supporting it by vacuum suction or human power alone, or a combination of them. We propose a method similar to the non-destructive method, characterized by continuously measuring strain / stress values during and after the operation.
The stress release device for residual strain / residual stress measurement according to the present invention is connected to a core bit connecting shaft that is dynamically connected to the drive shaft of the drive motor and a bearing that is press-fitted into the core bit connecting shaft. Core bit, a guide shaft extending in the axial direction in the core bit inserted in a through hole or a blocking hole drilled in the axial direction of the core bit connecting shaft, and a rigid wire inserted in the guide shaft so as to be movable forward and backward and the holder is threaded inserted in rigid wire holder, is one end secured to strain gauge or stress detector to the measurement object connection, and a lead wire to which the other end to the data logger is connected directly or indirectly the guide shaft is Ru der which is characterized in that independent of the rotation of the central opening through the core bit connection axis of the bearing.
Residual strain-residual stress measuring stress relief device of this invention, strain gauges or stress detector rigid wire shell measuring object at a position surrounding the is fixed, inside the guide shaft or rigid wire holder rigid wire shell It is also characterized by the fact that the
Therefore, first, a device capable of measuring strain / stress on the surface of the solid object to be measured is installed, and the outer periphery of the device is cut into a circular shape with equal depth. Next, after the operation is finished, the core drill cutter has a mechanism that can be installed on a rigid base, etc., held by magnetic force, supported by vacuum suction or supported by human power alone, or a combination of them. We have developed a device that can continuously measure strain during operation.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a stress release device for measuring residual strain / residual stress according to the present invention will be described below with reference to the drawings.
In the residual strain / residual stress measuring method according to the present invention, a strain measuring device is installed on the surface of a measurement target object in which strain / stress is actually generated, and a cut is made around the strain measuring device. Next, the operation of the core drill cutter is terminated while the stress is evenly released by the core drill cutter with a mechanism that can be supported by mounting on a rigid base, holding by magnetic force, vacuum suction, human power alone or a combination thereof After that, of course, strain can be measured continuously during operation.
[0007]
An example of a stress relief device used for this purpose is shown in FIG. The stress relief device 10 is devised so that a hole is formed in the center of the rotating shaft to which the core bit is attached, and the lead wire of the strain measuring device installed inside the core bit can be led out of the core bit without breaking. ing. That is, the stress relief device 10 has the core bit connecting shaft 13 inserted in the gear box 12 of the drive motor 11. The core bit connecting shaft 13 rotatably connects the hollow cylindrical core bit 15 via a bearing 14a having a central opening press-fitted into the front end portion. A similar bearing 14 b is also press-fitted into the rear end portion of the core bit connecting shaft 13. Bearing 14a. The central opening of 14b coincides with a through hole 13a (FIGS. 2 and 3) extending in the axial direction of the core bit connecting shaft 13, and becomes a part of the guide shaft 16 insertion hole.
[0008]
FIG. 2 shows a case where the rotation shaft (core bit connection shaft 13) to which the core bit 15 is attached and the drive shaft 17 are not collinear, and is an example in which the through hole 13a is provided only on the shaft to which the core bit 15 is attached. . Both ends of the lead wire or the like passed through the through hole 13a are connected to a strain gauge and a data logger, respectively, and continuous measurement can be performed even during the overcore operation. The drive shaft 17 is connected to a power source, and power is transmitted to the core bit connecting shaft 13 via a gear 18 or the like.
[0009]
FIG. 3 shows a case where the core bit connecting shaft 13 and the drive shaft 17 are in the same straight line, and a through hole 17a is provided from the shaft end of the core bit connecting shaft 13 to which the core bit is attached to the shaft end of the drive shaft 17. This is an example. Both ends of the lead wire or the like passed through the through-hole 17a are connected to a strain gauge and a data logger, respectively, and continuous measurement can be performed even during overcore work. The core bit 15 is driven by a power source (drive motor 11) provided on this shaft.
[0010]
FIG. 4 shows an example in which the through-hole 13 b is provided halfway through the core bit connecting shaft 13. As can be seen from the figure, since the through hole 13b is closed in a bag shape and the lead wire cannot be directly taken out, the data measured by installing a plurality of conductive rings 20 at the end of the through hole 13b is externally provided. To communicate. The thickness of the conductive ring 20 is continuous from the inner wall to the outer wall of the core bit connecting shaft 13, and the end of the lead wire or the like is in contact with the inner wall side of the conductive ring 20, and another lead wire is provided on the opposite outer wall side. Etc., and this is connected to a data logger or the like. Therefore, the measured value inside the core bit 15 can be transmitted to the outside even while the core bit connecting shaft 13 is rotating, and continuous measurement can be performed even during the overcore operation. Further, the power source to the core bit connecting shaft 13 may be installed on the same straight line as shown in FIG. 3, or may not be the same straight line as shown in FIG.
[0011]
More specifically, the core bit connecting shaft 13 is transmitted with power from the driving shaft 17 of the driving motor 11 via the gear 18 (FIG. 2) or directly connected to the driving shaft 17 (FIG. 3). But you can. In the case of FIG. 2, it is only necessary to form the through hole 13 a in the core bit connecting shaft 13, but in the case of FIG. 3, a similar through hole 17 a is also formed in the drive shaft 17.
A guide shaft 16 is inserted into the through-hole 13a, and a plurality of lead wires 19 whose ends are respectively connected to the strain gauge G and the data logger P are inserted into the guide shaft 16. The guide shaft 16 is bent at a right angle at a smooth angle at a position past the rear bearing 14b and then fixed to the gear box 12 with an adhesive or the like. With this arrangement, the guide shaft 16 is also fixed in the thrust direction without rotating while the core bit connecting shaft 13 is rotating. Since the lead wire 19 is inserted into the fixed guide shaft 16, it does not contact the inner wall of the core bit connecting shaft 13, and the broken line / breakage due to the rotation of the core bit 15 is prevented, and continuous measurement is performed even during overcore work. Is possible.
Instead of the through hole 13a, a core bit connecting shaft 13 having a blocking hole 13b extending halfway can be used (FIG. 4). In this case, a conductive ring 20 having the same wall thickness or the same thickness as the shaft wall of the core bit connecting shaft 13 is fitted into the core bit connecting shaft 13 at the closing side end position of the closing hole 13 b, and the lead wire 19 is connected to the conductive ring 20. Silk the inner wall. An external lead 21 reaching the data logger P is connected to the outer wall of the conductive ring 20. Data detected by the strain gauge G is output to the data logger P through the lead wire 19, the conductive ring 20, and the external lead 21.
During the overcore operation, the distance from the core bit 15 to the measurement target object B (FIG. 5) may be shortened, and the lead wire 19 may be slack. For example, the lead wire 19 is loosened by inserting a rigid wire holder 22 into the tip of the guide shaft 16 so as to be able to advance and retreat, and pulling out the lead wire 19 by a length L corresponding to the length in which the rigid wire holder 22 is accommodated in the guide shaft 16. This can be prevented (FIG. 6). The rigid wire holder 22 is made of a rigid hollow cylindrical body into which the lead wire 19 is inserted, and has an outer diameter substantially equal to the inner diameter of the guide shaft 16. One or more small-diameter rigid wire holders may be further inserted into the distal end of the rigid wire holder 22, and a multistage rigid wire holder such as an extendable antenna may be used.
[0012]
Next, a residual strain measurement method will be described. When a stress detector is used instead of the strain gauge G, the residual stress is measured by the same method.
A strain gauge G is attached to the surface of the measurement object B, and the lead wire 19 inserted through the guide shaft 16 and the rigid wire holder 22 is connected to the strain gauge G (FIGS. 5A and 5B). The stress relief device 10 is fixed to a rigid base (not shown) by an appropriate method such as mechanical, magnetic, vacuum suction, and human power.
Next, the power from the drive motor 11 is transmitted to the core bit 15, and the core bit 15 is rotationally moved in the overcore direction D toward the measurement target object B (FIG. 5C). Since the rigid wire holder 22 is accommodated in the guide shaft 16 as the overcore progresses, the lead wire 19 does not contact the inner wall of the core bit 15 (FIG. 5D). At this time, the lead wire 19 is pulled out from the rear by a length L corresponding to the length of the rigid wire holder 22 accommodated in the guide shaft 16, so that the lead wire 19 is not loosened in the guide shaft 16 and the rigid wire holder 22. The
[0013]
The measurement target object B is perforated by the rotation of the core bit 15, and the stress is gradually and uniformly released corresponding to the depth of the perforated part H. A strain corresponding to the released stress is indicated to the strain gauge G. Since the perforated portion H is formed by the rotating core bit 15, the residual stress around the strain gauge G is released uniformly. Moreover, since the core bit 15 can be reduced in diameter as long as the inner diameter can accommodate the strain gauge G, damage to the measurement target object B can be minimized. When a multiaxial strain gauge is used as the strain gauge G, the multiaxial strain state at that point, that is, the magnitude and direction of the multiaxial principal strain are measured.
The looseness of the lead wire 19 accompanying the movement of the core bit 15 in the over-core direction D direction is also absorbed by the relatively large-diameter rigid wire shell 23 disposed on the measurement target object B at a position surrounding the strain gauge G ( FIG. 7A, B). When the core bit 15 advances in the over-core direction D, the slack of the lead wire 19 is accommodated in the rigid wire shell 23, and the contact of the lead wire 19 with the inner wall of the rotating core bit 15 is prevented (FIGS. 7C and D). ). In this case, it is not necessary to pull out the loose lead wire 19 from the rear end. The rigid wire shell 23 can be used in combination with the rigid wire holder 22.
In addition, a leg for fixing to a rigid base, a holding by magnetic force, an adsorption by vacuum, or an appropriate handle for supporting by human power can be assembled on the body outer surface of the stress releasing device shown in FIG.
[0014]
【Example】
A mortar specimen was used as an object to be measured, and uniaxial strain gauges 31R and 31L and a triaxial strain gauge 32 were fixed to the surface position of the mortar specimen 30 shown in FIG. The installation positions of the uniaxial strain gauges 31R and 31L were set equidistant from the center point of the mortar specimen 30. Similar uniaxial strain gauges 31R and 31L were fixed to the back surface of the mortar specimen 30 at positions corresponding to the uniaxial strain gauges 31R and 31L on the front surface side.
A compressive load F was applied to the mortar specimen 30 to which the strain gauges 31R, 31L, and 32 were fixed, and the mortar specimen 30 was compressed in the uniaxial direction to maintain the compressed state (FIG. 8B). When a compressive load F of 10,000 tons was applied, a stress value of 66.67 kgf / cm ² was shown.
Next, the core bit 15 was overcored around the triaxial strain cage 33 along the overcore locus T. At this time, the center of the core bit 15 was aligned with the center of the mortar specimen 30, and the rigid wire shell 23 was disposed between the mortar specimen 30 and the core bit 15.
In the overcore, the value from each strain gauge 31R, 31L, 32 is output to the data logger P and recorded every 0.1 cm until the depth of the perforated portion H reaches 3 cm, and the depth of the perforated portion H is recorded. From the time when the value of 3 exceeded 3 cm, recording was performed every 0.5 cm. Strain in the direction of compressive load F (channel number: Ch.1, Ch.2) for uniaxial strain gauges 31R and 31L arranged on the surface of the mortar specimen 30, and compressive load for uniaxial strain gauges 31R and 31L arranged on the back surface Strain in the F direction (channel number: Ch.3, Ch.4), strain in the compressive load F direction (channel number: Ch.5) in the triaxial strain gauge 32, strain in a direction orthogonal to the compressive load F (channel number) : Ch.6) and strain (channel number: Ch.7) in a direction inclined 45 degrees in the direction of the compressive load F were measured.
[0015]
Each strain continuously measured in the overcore changed as shown in FIG.
When the depth of the perforated part H is zero, Ch. The measured strain values of 1 to 5 are almost the same value, and it can be seen that the compressive load F is uniformly applied to the mortar specimen 30 without being biased. Although vertical distortion is calculated to -333μm蛩Young's modulus 20 La L0〓kgf / cm ² compressive load F = 66.67kgf / cm ² and mortar specimen 30 at this time, Ch. The actually measured strain values of 1 to 5 are approximate to the calculated values.
When overcore is started, Ch. The measured strain value of 5-7 gradually approached zero, and became almost zero when the depth of the perforated part H became 1.5 cm. Further over-core, Ch. 5 and Ch. 7 is positive (tensile strain), Ch. The measured strain value of No. 6 became negative (compression strain). The measured strain values of 5 to 7 are also asymptotic to zero, indicating that the stress has been released. On the other hand, Ch. In 1 to 4, it can be seen that the measured strain value is almost constant even in the overcore, and that a uniform load stress continues to act.
[0016]
【The invention's effect】
As described above, the stress releasing device for measuring residual strain / residual stress according to the present invention can achieve the following effects.
<A> Since it is possible to measure using a simple device, there is no cost, and accurate measurement can be performed with a simple operation.
<B> Since the stress release method does not include inclusions, accurate residual strain / residual stress should be measured regardless of the positional relationship, as long as the strain measurement device and lead wires are not damaged. Can do.
<C> Since a cylindrical core bit is used for the stress release device, the outer periphery of the strain measurement device can be formed into a circular shape, and can be quickly cut at an equal depth. Can be released uniformly.
<D> Since a mechanism capable of guiding a lead wire or the like is incorporated in the stress release device, strain can be continuously measured during and after the stress release operation.
<E> The stress relief device can be supported by a method such as fixing to a rigid base, holding by magnetic force, adsorption by vacuum or supporting by human power, or a combination of these methods, so that stress can be relieved according to the situation in the field. I can work.
<F> Since the diameter of the core bit used can be made sufficiently small, it is possible to minimize damage to the target object for local site measurement and residual strain / residual stress measurement.
<G> Based on the measurement results obtained by simple operations, it becomes possible to accurately grasp the dynamic state of the target object in more detail than before, contributing to the elucidation of phenomena in various fields. Can do.
<H> It is possible to quantitatively measure the strain / stress at the current position that is non-destructive as viewed globally without substantially degrading the function of the target object.
<L> Normally, the present invention can also be applied to a portion of a target object having a complicated shape or the like that is considered impossible to measure residual strain / residual stress.
Further, according to the stress relief device of the present invention, the lead wire connecting the strain gauge and the data logger is separated from the rotation of the core bit connecting shaft and the core bit. Therefore, the lead wire is not twisted by the rotation of the core bit connecting shaft and the core bit, and the residual strain and residual stress can be measured even in the overcore. In particular, since the lead wire is inserted into the fixed guide shaft, it does not contact the inner wall of the core bit connection shaft, preventing broken lines and disconnection due to the rotation of the core bit, enabling continuous measurement even during overcore work. Become.
In addition, since a notch having a depth equal to the outer periphery of the strain gauge is formed using a cylindrical core bit, the release of stress is made uniform. In addition, since the residual strain and residual stress are measured in the overcore, the reliability of the measured value is also improved.
[Brief description of the drawings]
FIG. 1 is an overall perspective view of a stress release device for measuring residual strain and residual stress according to the present invention.
FIG. 2 is a perspective view showing an example of lead wire processing when the core bit connecting shaft and the drive shaft are not on the same straight line.
FIG. 3 is a perspective view showing an example of lead wire processing when the core bit connecting shaft and the drive shaft are on the same straight line.
FIG. 4 is a perspective view when a blocking hole is provided in the core bit connecting shaft.
FIG. 5 is a schematic view showing an example of a lead wire loosening prevention mechanism using a rigid wire holder system.
FIG. 6 is a perspective view showing a state in which a rigid wire holder is inserted into the tip of a guide shaft so as to be able to advance and retract.
FIG. 7 is a schematic view showing an example of a lead wire loosening prevention mechanism using a rigid wire shell method.
FIG. 8 is an explanatory diagram of an example in which a compressive load is applied to a mortar specimen (a) as a measurement target object (b) and a change in strain (c) according to the progress of overcore is obtained.
[Explanation of symbols]
10: Stress release device 11: Drive motor 12: Gear box 13: Core bit connecting shaft 13a: Through hole 13b: Closing holes 14a, 14b: Bearing 15: Core bit 16: Guide shaft 17: Drive shaft 18: Gear 19: Lead wire 20 : Conductive link 21: External lead 22: Rigid wire holder 23: Rigid wire shell G: Strain gauge P: Data logger B: Measurement object D: Overcore direction H: Perforated part

Claims (2)

A core bit connecting shaft that is dynamically connected to the drive shaft of the drive motor, a core bit that is rotatably connected via a bearing press-fitted into the core bit connecting shaft, and is drilled in the axial direction of the core bit connecting shaft. A guide shaft extending in the axial direction in the core bit, a rigid wire holder inserted in the guide shaft so as to be able to advance and retreat, and inserted into the rigid wire holder. A lead wire having one end connected to the fixed strain gauge or stress detector and the other end connected directly or indirectly to the data logger; the guide shaft passes through a central opening of the bearing; and the core bit connecting shaft Stress release device for measuring residual strain and residual stress, characterized by being independent of rotation of The residual strain / residual stress measurement stress according to claim 1, wherein a rigid wire shell is fixed to an object to be measured at a position surrounding a strain gauge or a stress detector, and a guide shaft or a rigid wire holder faces inside the rigid wire shell. Release device.

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