JP2010181245A - Method for controlling crack, tool for setting, and device for controlling therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable easy control of a crack length even if a material has high strength such as commentated carbide, when a specimen is thick, considerable larger, or relatively small. <P>SOLUTION: The method for controlling a crack that a crack 15 is formed on a specimen 3 with a notched groove 13 on the center of the side 3c of a rectangular body having a predetermined length towards the other side 3d, includes the step of loading a compressed load P<SB>O</SB>on a side of a specimen 3 from a direction that controls the open of the notched groove 13 between a side 3c of the specimen 3 and the other side 3d of the specimen 3, the step of supporting a side of the rectangular body at two points on both sides of the notched groove 13 and loading a load P<SB>1</SB>towards the notched groove 13 at two points on the other side, and the step of providing two-point-supporting and three-point-bending by the load P<SB>1</SB>to the specimen 3 and generating the crack 15. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a crack control method, a crack length setting tool, and a crack control device for applying a crack to a test piece in advance.

  Various specimens for fracture mechanics are used to know the material strength related to the progress of cracks. A typical example is a compact tensile standard test piece (hereinafter referred to as “CT test piece”).

  If the CT specimen is a ductile material such as metal, it is possible to easily introduce cracks, which are natural cracks, by a fatigue test. However, when the CT specimen is a brittle material such as ceramics, it is difficult to control cracks as shown in “Testing Method for Fracture Toughness” (Non-Patent Document 1).

On the other hand, the applicant of the present application has proposed “a crack introduction device, a crack introduction jig, and a crack introduction method”. This is a technique for controlling the length of a crack (crack) by utilizing a frictional force induced during compression of materials having different Young's moduli. (Patent Document 1)
In this method, a tensile force is applied in the direction of expanding the notch groove of the test piece to generate cracks from the notch groove, and the Young's modulus of the surface is larger than the Young's modulus of the test piece on the surface where the notch groove exists. Place the pressure plate. The compression length is controlled by applying a compression load to the pressure plate and inducing a compressive friction force on the contact surface of the test piece in contact with the pressure plate. For this reason, the crack to be introduced depends on the material and size of the pressure plate that generates the frictional force of compression. Accordingly, it depends on the size and strength of the test piece with respect to the pressure plate, and cracks can be introduced into a test piece having a relatively thin thickness or a test piece having a low strength.

  On the other hand, when the thickness of the test piece is large or the test piece is quite large, when the material has high strength such as cemented carbide, the length of the crack could not be freely controlled. .

  On the other hand, a concrete structure is designed and constructed on the assumption that cracking occurs due to drying shrinkage of the concrete. For this reason, when the crack which generate | occur | produces becomes a big defect, since it will cause the lack of durability of a structure, many crack repair materials have been developed.

  To repair a crack, it is necessary to grasp the crack condition based on the investigation result of the crack and adopt a method suitable for the purpose of the repair. Therefore, it is necessary to form a crack in a concrete specimen when evaluating a crack repair material.

  However, since concrete specimens are brittle materials and are relatively thick and tend to be large in size, when the cracks are introduced into the specimens, the previously proposed technique uses cracks within the specimens. I couldn't stop it.

JP 2007-155665 A

Ceramics Basic Course 1, Ceramics Experiment, Uchida Otsukuru Publication (April 25, 2001), p. 153. )

  The problem to be solved is the length of the crack when the specimen is thick, when the specimen is quite large or relatively small, or when the material has high strength such as cemented carbide. It was a point that could not be controlled.

  The present invention controls the length of cracks even when the thickness of the test piece is large, when the test piece is considerably large or relatively small, even when the material has high strength such as cemented carbide, A crack control method for forming a crack in a test piece in which a notch groove having a predetermined length is formed in the center of one side of a rectangular body toward the other side, between one side and the other side of the test piece A compressive load is applied to the side surface of the test piece from the direction that regulates the opening of the notch groove, two sides of the test piece are supported at both sides of the notch groove, and the notch is provided on the other side surface. A central load directed toward the groove is applied to the two-point support, and a three-point bend is applied to the test piece by the two-point support and the central load to generate a crack from the notched groove, or the test piece A load is applied in the direction of opening the notch groove to the notch groove. Characterized in the control method cracks that generate beauty cracking.

  This invention is a crack length setting tool used for the said crack control method, Comprising: The direction which adjoins the 1st, 2nd pressurization part made to contact | abut to the side surface of the said rectangular body, and the said 1st, 2nd pressurization part The crack length setting tool is characterized in that it is provided with a pressurizing drive unit that is moved to a position where the compression load is applied.

  The present invention relates to a crack control device used in the crack control method, wherein the two-point support is performed on the base side, and a load from a load generating portion is received and transmitted as the central load to the other side surface. The feature of the crack control device is that the pressure piece is provided.

  The present invention relates to a crack control method for forming a crack in a test piece in which a notch groove having a predetermined length is formed in the center of one side surface of a rectangular body toward the other side surface. A compression load is applied to the side surface of the test piece from the direction of regulating the opening of the notch groove between the two sides, and one side surface of the test piece is supported at two positions of the notch groove, and the other side surface is supported. A center load toward the notch groove is applied to the two-point support, and the test piece is subjected to a three-point bend due to the two-point support and the center load to generate a crack from the notch groove, or In addition, a crack control method for generating a crack from the notch groove by applying a load to the test piece in the direction of opening the notch groove was adopted.

  Therefore, it is not a technique to control the crack length by using frictional force, but it is possible to accurately control the crack length by applying a compressive load to the side surface of the test piece from the direction of regulating the opening of the notch groove. Can be done.

  In addition, the crack length is reliably controlled even when the thickness of the specimen is large, when the specimen is quite large, when the specimen is relatively small, or when the material has high strength such as cemented carbide. can do.

  This invention is a crack length setting tool used for the said crack control method, Comprising: The direction which adjoins the 1st, 2nd pressurization part made to contact | abut to the side surface of the said rectangular body, and the said 1st, 2nd pressurization part It was set as the crack length setting tool provided with the pressurization drive part which is moved to and applies the said compression load.

  For this reason, when the thickness of a test piece is thick, even when a material has high strength like a cemented carbide, a compressive load for controlling the length of cracks can be easily applied.

  The present invention is a crack control device used in the crack control method, wherein the two-point support is disposed on the base side, receives a load from a load generating portion, and transmits the load to the other side as the central load. It was set as the crack control apparatus provided with a pressurization piece.

  For this reason, when the thickness of the test piece is large, even when the material has high strength such as cemented carbide, it is possible to easily apply a bending load that generates a crack from the notch groove.

It is a schematic front view which shows a crack control apparatus notionally (Example 1). The dimension of a CT test piece is shown, (a) is a front view, (b) is an end view. (Example 1) It is a schematic plan view of the state which attached the crack length setting tool. (Example 1) It is a schematic side view of the state which attached the crack length setting tool. (Example 1) It is a front view of an acrylic CT test piece. (Example 1) It is a table | surface of the dimension of an acrylic CT test piece. (Example 1) It is a graph which shows the implementation conditions of an acrylic CT test piece. (Example 1) It is a graph which shows the implementation result of an acrylic CT test piece. (Example 1) It is a graph which shows the implementation result of an acrylic CT test piece. (Example 1) It is a graph which shows the result of FIG. (Example 1) It is a graph which shows the result of FIG. (Example 1) It is a chart corresponding to FIG. 6 and showing the magnitude | size of an acrylic CT test piece. (Example 1) FIG. 9 is a chart corresponding to FIG. 7 and showing experimental conditions for an acrylic CT test piece. (Example 1) It is a graph corresponding to FIG. 8 and showing the implementation result of an acrylic CT test piece. (Example 1) Regarding the crack control method and apparatus, (a) is a schematic front view conceptually showing the crack control apparatus corresponding to FIG. 1, and (b) is a schematic side view thereof. (Comparative example) It is a front view of the acrylic CT test piece which shows the measurement position of crack length. (Comparative example) It is a chart corresponding to FIG. 6 and showing the magnitude | size of an acrylic CT test piece. (Comparative example) FIG. 9 is a chart corresponding to FIG. 7 and showing experimental conditions for an acrylic CT test piece. (Comparative example) It is a graph corresponding to FIG. 8 and showing the implementation result of an acrylic CT test piece. (Comparative example) It is a chart corresponding to FIG. 6 and showing the magnitude | size of a glass CT test piece. (Example 1) FIG. 9 is a chart corresponding to FIG. 7 and showing experimental conditions for glass CT test pieces. (Example 1) It is a graph corresponding to FIG. 8 and showing the implementation result of a glass CT test piece. (Example 1) It is a chart corresponding to FIG. 6 and showing the magnitude | size of the gypsum CT test piece. (Example 1) FIG. 9 is a chart corresponding to FIG. 7 and showing experimental conditions for a gypsum CT test piece. (Example 1) It is a graph corresponding to FIG. 8 and showing the implementation result of the gypsum CT test piece. (Example 1) It is a chart corresponding to FIG. 6 and showing the magnitude | size of a super steel alloy CT test piece. (Example 1) FIG. 9 is a chart corresponding to FIG. 7 and showing experimental conditions of a super steel alloy CT test piece. (Example 1) FIG. 9 is a chart corresponding to FIG. 8 and showing the results of the super steel alloy CT specimen. (Example 1) It is a chart corresponding to FIG. 6 and showing the magnitude | size of the mortar CT test piece. (Example 1) FIG. 8 is a chart corresponding to FIG. 7 and showing experimental conditions of a mortar CT test piece. (Example 1) It is a graph corresponding to FIG. 8 and showing the implementation result of the mortar CT test piece. (Example 1) The test piece for mortar concrete crack repair material evaluation is shown, (a) is a front view, (b) is an end view. (Example 2) FIG. 7 is a chart corresponding to FIG. 6 and showing the size of a test piece for evaluating a mortar / concrete crack repair material. (Example 2) FIG. 9 is a chart corresponding to FIG. 7 and showing experimental conditions of a test piece for evaluating a mortar / concrete crack repair material. (Example 2) (A) is an implementation result of mortar, (b) is a chart showing an implementation result of concrete. (Example 2) It is a graph which shows the results table of the cement which is the material used for a test piece. (Example 2) FIG. 7 is a chart corresponding to FIG. 6 and showing the size of a test piece. (Example 2) FIG. 9 is a chart corresponding to FIG. 7 and representing experimental conditions. (Example 2) It is a perspective view of the test piece which shows the length and width of a crack. (Example 2) It is a principal part expansion perspective view of the test piece which shows the length and width of a crack. (Example 2) It is an implementation result of the test piece for mortar crack repair material evaluation. (Example 2) It is an implementation result of the test piece for concrete crack repair material evaluation. (Example 2) It is a schematic front view which shows a crack control apparatus notionally. (Example 3) FIG. 7 is a chart corresponding to FIG. 6 and showing the size of a test piece. (Example 3) FIG. 9 is a chart corresponding to FIG. 7 and representing experimental conditions. (Example 3) FIG. 9 is a chart corresponding to FIG. 8 and showing an implementation result. (Example 3)

  When the thickness of the test piece is thick, the test piece is quite large, when it is relatively small, the purpose of being able to control the crack length even when the material has a high strength such as cemented carbide, This was realized by compressive load in the direction to regulate the opening of the notch groove and three-point bending.

[Crack control device]
FIG. 1 is a schematic front view conceptually showing a crack control device.

  The crack control device 1 in FIG. 1 realizes a crack control method for introducing a crack into a test piece 3, and includes a load generation unit 5, a support base 7, a pressure piece 9, and a crack length setting tool 11. Yes.

  The test piece 3 is formed of a brittle material such as concrete in a rectangular shape, and has a notch groove 13 having a predetermined length toward the other side surface 3d at the center of one side surface 3c.

  This test piece 3 shows a CT test piece for fracture mechanics as an example. The CT specimen is in accordance with the American material test standard ASME, E-399 shown in FIG. 2, and the dimensions of this CT specimen are as shown in the front and end views of FIGS. 2 (a) and 2 (b), respectively. The dimensions are determined based on the length W, where B is the width of the test piece. If it demonstrates with the same code | symbol as FIG. 1, the notch (Notch) 13 is provided in the center part of CT test piece 3, and the crack (crack) (Precrack) 15 which is a natural crack is formed from the front-end | tip 13a.

  The length from the crack tip to the center of the tensile pin holes 3a and 3b provided to know the material strength is represented by a, and the material is evaluated by using the value of a / W.

As shown in FIG. 1, the load generator 5 is configured to generate a load P ₁ with the base 17. Load generating unit 5 for generating a load P ₁ is of a manual using a screw mechanism, or can be various selected such that using a hydraulic pressure.

  The support base 7 is made of, for example, steel, and the two-point support of the test piece 3 is arranged on the base 17 side. In addition, the material of the support base 7 is not specifically limited, If it can support the test piece 3, various types can be selected, for example, acrylic, die steel, etc. can also be used.

  Support portions 7 a and 7 b are projected from the support base 7. The upper surfaces 7aa and 7ba of the support portions 7a and 7b are formed in a plane in accordance with one side surface 3c of the test piece 3.

  The test piece 3 is placed on the upper surfaces 7aa and 7ba of the support portions 7a and 7b, and one side surface 3c of the test piece 3 is supported on the base 17 at both sides of the notch groove 13 by the support portions 7a and 7b.

Top 7aa, width of 7ba can load the bending moment on the test piece 3 by the load _{P 1,} is and what top 7aa by the load _{P 1,} the specimen 3 by the reaction force from 7ba so as not to crush.

The length of the support portions 7a and 7b in the width direction of the test piece 3 (the direction orthogonal to the plane of FIG. 1) is formed to be equal to the width of the test piece 3. However, the bending can load moment specimen 3, and the upper surface due to the load P ₁ 7aa, as long as the extent to which the test piece 3 by the reaction force does not collapse from 7ba, the support portion 7a, 7b of the length specimen 3 can be selected as large or small.

  Note that the support portions 7 a and 7 b can be configured as separate bodies without being integrally formed as the support base 7.

The pressure piece 9 is formed in a rectangular bar shape from, for example, aluminum, receives the load P ₁ from the load generating portion 5, and transmits it to the other side surface 3 d of the test piece 3 as a central load.

  In addition, the material of the pressurization piece 9 is not specifically limited, As long as it can transmit a load to the test piece 3, various kinds can be selected, for example, acrylic, die steel, etc. can also be used.

Width of face 9a, 9b of the pressure piece 9 can load the bending moment on the test piece 3 by the load P _1, and a force from the surface 9a by the load P ₁ test piece 3 is of an extent that does not crush .

The length dimension of the pressure piece 9 in the width direction of the test piece 3 (in the direction orthogonal to the plane of FIG. 1) is formed to be equal to the width of the test piece 3. However, if the test piece 3 can be loaded with a bending moment and the test piece 3 is not crushed by the force from the surface 9 b due to the load P ₁ , the length of the pressure piece 9 is set to the length of the test piece 3. Large and small can be selected.

  FIG. 3 is a schematic plan view of a state in which a crack length setting tool is attached, and FIG. 4 is a schematic side view thereof.

  As shown in FIGS. 1, 3, and 4, the crack length setting tool 11 includes first and second pressure units 19 and 21 and pressure drive units 23 and 25.

  The first and second pressure units 19 and 21 are in contact with the side surfaces 3e and 3f of the test piece 3, and the pressure driving units 23 and 25 are the first and second pressure units 19 and 21, respectively. They are moved in directions close to each other to apply a compressive load to the test piece 3.

  The first and second pressure units 19 and 21 include pressure plates 27 and 29 and pressure tables 31 and 33.

  The pressure plates 27 and 29 are formed in a rectangular shape from steel or the like. The material of the pressure plates 27 and 29 is not particularly limited, and various types can be selected as long as the material can transmit a load to the test piece 3. For example, aluminum or the like can be used.

The length of the pressure plates 27 and 29 as viewed from the plane of FIG. 3 is larger than the thickness of the test piece 3 so that the compressive load P ₀ can be evenly applied to the side surfaces 3e and 3f of the test piece 3. The same effect can be obtained with a length equivalent to the thickness.

The pressurization bases 31 and 33 are coupled to the pressurization driving units 23 and 25 and are brought into contact with the pressurization plates 27 and 29. The pressurization bases 31 and 33 are made of, for example, metal, and are formed in a mountain shape protruding toward the pressurization plates 27 and 29. The pressurization bases 31 and 33 are formed in a mountain shape to increase rigidity and prevent deformation when the compressive load P _{0 is} generated.

  Through holes 31 a and 33 a are formed at both ends of the pressurization bases 31 and 33.

A ball 35 such as a steel ball is interposed between the one pressure plate 27 and the pressure table 31. The presence of the ball 35, the compressive load _{P 0} by pressurized圧台31,33 side 3e of the test piece 3, can be applied equally securely to 3f.

  The pressure driving units 23 and 25 are constituted by bolts 23a and 25a and nuts 23b and 25b as fasteners disposed on both sides of the test piece 3. The bolt bolts 23 a and 25 a are disposed through the through holes 31 a and 33 a of the pressurization bases 31 and 33.

The pressurization bases 31, 33 can be fastened and moved by fastening the bolts 23a, 25a and the nuts 23b, 25b.
[Crack control method]
In the crack control method according to the embodiment of the present invention, the crack control device 1 is used, and a crack 15 is formed on a test piece 3 in which a notch groove 13 having a predetermined length is formed at the center of one side surface 3c of the rectangular body toward the other side surface 3d. This is a crack control method for forming a crack.

Using the crack length setting tool 11, a compressive load P ₀ is applied to the side surfaces 3 e and 3 f of the test piece 3 from the direction in which the opening of the notch groove 13 is regulated between the one side surface 3 c and the other side surface 3 d of the test piece 3. To load.

The value of the compressive load P ₀ is measured by using the minute displacement of the pressurization bases 31 and 33. That is, the strain cage G affixed to the pressurization table 31 and a static strain meter (not shown) can be connected and converted from the static strain meter. Therefore, the compressive load P ₀ can be easily applied by tightening the nuts 23b and 25b to the bolts 23a and 25a while looking at the static strain meter.

The test piece 3 loaded with the compressive load P ₀ is placed on the support portions 7 a and 7 b of the support base 7, and one side surface 3 c of the test piece 3 at the positions on both sides of the notch groove 13 by the upper surfaces 7 aa and 7 ba. Make point support. Note that this two-point support is support on the long upper surfaces 7aa and 7ba, and refers to support at two locations on both sides when viewed from the side surface of FIG.

In this state, a load P ₁ toward the notched groove 13 through the other side surface 3d in pressure piece 9 to the two-point support by the load generation section 5. This load P _{1 is} also applied to the entire thickness direction of the test piece 3.

A crack 15 is generated from the notch groove 13 by giving the test piece 3 two-point support by the support base 7 and three-point bending by the load P ₁ .

  The length of the crack 15 at this time can be approximately λ. Here, λ is the distance between the tip 13a of the notch groove 13 and the lowermost surface of the pressure plates 27 and 29 in FIG.

When the load P ₁ is applied as described above, a maximum tensile stress is generated in the notch groove 13. When the load P ₁ is increased, the induced maximum tensile stress reaches the fracture stress of the test piece 3. For this reason, a crack is generated from the tip 13a of the notch groove 13 and progresses.

However, since the compressive load P ₀ is applied to the test piece 3 in advance, the tip of the generated crack cannot be opened, and the progress of the crack stops in the vicinity thereof.

Therefore, not only the thickness B of the test piece 3 but also the crack can be retained in the test piece 3 regardless of the size. Furthermore, the length and width of the crack can be controlled by the position of the distance λ by changing the position of the crack length setting tool 11 and the compression load P ₀ .

As a matter of course, instead of the test piece 3 which is a CT test piece, cracks are similarly introduced to other rectangular test pieces having notches irrespective of the thickness and size of the test piece. Can do.
[Acrylic CT specimen: thickness 20 mm]
Here, the control of cracks was attempted using a transparent body that clearly shows the state of cracks retained in the test piece, and acrylic that makes it extremely easy to produce the test piece. The acrylic used in this case was Sumitomo Chemical Co., Ltd. trade name Sumipex, thickness 20 mm.

  FIG. 5 is a front view of an acrylic CT test piece, and FIG. 6 is a chart of the dimensions of the test piece. The dimensions of the CT specimen are 48 × 50 mm rectangular plates according to ASTM standard E-399, thickness B = 20 mm, width W = 40 mm. In the CT test piece, a drill (dimension: φ10 mm) was used at two predetermined positions on a drilling machine using a drill (dimension: φ10 mm) for examining the fracture toughness value. Further, N in the figure is a notch groove, which is provided with a length l = 19 mm by milling with a blade width t = 1.0 mm.

  FIG. 7 is a chart showing implementation conditions. As shown in FIG. 7, the specifications of the pressure piece 9, the pressure plates 27 and 29, the support bases 31 and 33, and the distance λ were determined.

3, compressive load P ₀ as shown in FIG. _4, a load P ₁ was loaded was measured breaking load P _F and crack length δmax when cracking occurs in CT specimen. Here, δmax indicates the longest crack length, and in the case of a transparent body such as acrylic or glass, it is mainly given by the length at the center of the plate thickness.

8 and 9 are diagrams showing the results of the implementation. FIG. 8 shows the relationship between the pressing stress σ _k and the crack length δmax when λ = 15 mm is constant, and FIG. 9 shows the pressing stress σ. ₄ is a chart showing a relationship between a distance λ and a crack length δmax when _k = 16 MPa is constant. FIG. 10 is a graph showing the result of FIG. 8, and FIG. 11 is a graph showing the result of FIG.

8, as shown in FIG. 10, when a distance lambda = 15 mm constant, crack length δmax varies by applying pressure stress sigma _k, and when cracking length δmax is that a pressing pressure stress sigma _k = 16 MPa constant, As shown in FIG. 9 and FIG. 11, it varies depending on λ, and δmax has a relationship depending on σ _k and λ.

This shows that the crack length can be controlled with respect to the acrylic CT test piece.
[Acrylic CT specimen: thickness 30 mm]
FIGS. 12 to 14 show an attempt to control cracks in the same manner as described above for an acrylic CT test piece having a thickness of 30 mm, and FIG. 12 corresponds to FIG. 6 and is a chart showing the size of the test piece. Is a chart corresponding to FIG. 7 and representing experimental conditions, and FIG. 14 is a chart corresponding to FIG.

  The test piece here is a transparent acrylic CT test piece having the same dimensions as in FIG. 5 except for a thickness of 30 mm as shown in FIG.

  The crack length δmax as shown in FIG. 14 could be controlled by the CT test piece having a thickness of 30 mm shown in FIG. 12 under the conditions shown in FIG.

  15A and 15B relate to a crack control method and apparatus according to a comparative example, in which FIG. 15A is a schematic front view conceptually showing the crack control apparatus corresponding to FIG. 1, and FIG. 15B is a schematic side view thereof.

The crack control method and apparatus of the comparative example of FIG. 15 will be described with the same reference numerals given to the components corresponding to FIG. Similar to Patent Document 1, the pressure plates 27 and 29 are configured to control the length of cracks by applying a compression load P ₀ to the surface where the notch groove 13 exists. Under this compressive load P ₀ , a load P ₁ (tensile force) is applied in the direction of expanding the notch groove 13 of the test piece 3 to generate a crack from the notch groove 13, and the crack length is controlled by the compressive load P _0. Do.

  FIG. 16 is a front view of the test piece showing the measurement position of the crack length. The crack length δmax according to the comparative example was measured at the position shown in FIG.

  FIG. 17 corresponds to FIG. 6 and represents a test piece size. FIG. 18 corresponds to FIG. 7 and represents a test condition. FIG. 19 corresponds to FIG. It is.

  With the crack control method and apparatus of the comparative example of FIG. 15, as shown in FIG. 17, the thickness B is changed to B = 5, 10, 15, 20, and 30 mm to introduce cracks into the acrylic CT test piece, It was proved that cracks could not be controlled due to insufficient frictional force when the thickness was thicker than a predetermined value.

That is, the compression load P ₀ is applied by the pressure plates 27 and 29 separated from the tip of the notch groove 13 by a distance λ = 3 mm (constant), and then the pins inserted into the pulling pin holes 3a and 3b are tested with a testing machine or the like. tension, was a load _{P 1.}

In this way, it notched groove 13 tip 13a Karahibiware was introduced at a load _P 1 = _{P F} of values.
To obtain a crack length δmax when the value of the load P ₁ becomes P _{1 =} P _F in the experiment. In addition, since the crack in this case is curved, the deviated distance δv was also measured in addition to the crack length δmax shown in FIG.

  The result was as shown in FIG. 19 under the implementation conditions of FIG.

  The crack was controllable when the thickness B of the test piece 3 was 20 mm or less. By this crack control, it was possible to keep the crack in the test piece 3.

However, at B = 30 mm, the compressive load P ₀ that induces friction to stop the cracks is considerably high, and cracks are not generated before trying to pull, but the surface of the test piece 3 is indented by the pressure plates 27 and 29. Some wounds remained. This is because the portions directly under the pressure plates 27 and 29 are considerably compressed. And the internal pressure acted on the outer side of the test piece 3, and the crack 15 was generated by bending as shown in FIG. 16 from the notch groove 13. As a result, it was found that there is a limit to control of cracks in the case of the thick specimen 3.
[Glass CT specimen: thickness 18mm]
20 to 22 show an attempt to control cracks in the same manner as the acrylic CT test piece with respect to the glass CT test piece, and FIG. 20 corresponds to FIG. 6 and is a chart showing the size of the test piece, FIG. FIG. 22 is a chart corresponding to FIG. 7 and representing experimental conditions, and FIG. 22 is a chart corresponding to FIG.

  The glass used in this case was a float glass manufactured by Central Glass Co., Ltd., and the product name FL18 was used.

Also for glass, the crack length δmax could be controlled as shown in FIG. 22 by the test piece of FIG.
[Gypsum CT specimen: thickness 20 mm]
23 to 25 show an attempt to control cracks in the same manner as the acrylic CT test piece with respect to the gypsum CT test piece. FIG. 23 corresponds to FIG. 6 and is a chart showing the size of the test piece. FIG. 25 is a chart corresponding to FIG. 7 and representing experimental conditions, and FIG. 25 is a chart corresponding to FIG. Here, δmax of a non-transparent test piece such as gypsum, mortar, and cemented carbide was determined by measuring the length of cracks generated on both surfaces of the test piece and adopting the longer value.

  Moreover, the gypsum in this case is an industrial thing manufactured with the amount of mixed water 25% using the gypsum powder of type RC-150 by San-S gypsum Co., Ltd.

With regard to gypsum, the crack length δmax could be controlled as shown in FIG. 25 under the conditions shown in FIG.
[Super steel alloy CT specimen: thickness 12mm]
26 to 28 show an attempt to control cracking in the same manner as the acrylic CT test piece with respect to the super steel alloy CT test piece, and FIG. 26 is a chart corresponding to FIG. FIG. 27 is a chart corresponding to FIG. 7 and showing experimental conditions, and FIG. 28 is a chart corresponding to FIG. 8 and showing the implementation results.

  As the super steel alloy in this case, Fujiloy super steel alloy type D60 manufactured by Fuji Dice Co., Ltd. was used.

Also for the super steel alloy, the crack length δmax could be controlled as shown in FIG. 28 under the conditions shown in FIG.
[Mortar CT specimen: thickness 40mm]
29 to 31 show an attempt to control cracking in the same manner as the acrylic CT test piece with respect to the mortar CT test piece, and FIG. 29 corresponds to FIG. 6 and is a chart showing the size of the test piece, FIG. FIG. 31 is a chart corresponding to FIG. 7 and representing experimental conditions, and FIG. 31 is a chart corresponding to FIG.

  As the mortar in this case, a base mortar was produced according to JIS R 5201 (cement physical test method). A cement mortar with a water cement ratio of 50% and a cement fine aggregate ratio of 1: 3 (mass ratio) was molded to a size of 100 × 100 × 400 mm, 1d wet air [20 ° C., 90% (RH)] and 27d Curing was performed in water (20 ° C.). Next, the base material mortar was cut into dimensions of 100 × 100 × 50 mm and 100 × 100 × 100 mm, and natural cracks were formed from the cutout grooves.

  For the mortar as well, the crack length δmax was controlled as shown in FIG. 31 under the conditions shown in FIG.

[Test specimen for evaluating mortar / concrete crack repair material: thickness 50mm]
FIG. 32 shows a test piece for evaluating a mortar / concrete crack repair material, where (a) is a front view and (b) is an end view. The size was 100 × 100 × 50 mm, and a test piece having a thickness of 50 mm was used.

  FIG. 33 is a chart corresponding to FIG. 6 and representing the size of the test piece, and FIG. 34 is a chart corresponding to FIG. 7 and representing the experimental conditions.

  FIG. 35A is a chart showing the results of mortar, and FIG. 35B is a chart showing the results of concrete.

For the test piece thickness 50 mm for mortar / concrete crack repair material evaluation, the test piece of FIGS. 32 and 33 can be used to stop the crack in the test piece with respect to the breaking load of FIG. (Remarks ○)
[Test specimen for mortar / concrete crack repair material evaluation: thickness 100mm]
36 is a chart showing a result table of cement as a material used for the test piece, FIG. 37 is a chart showing the size of the test piece corresponding to FIG. 6, and FIG. 38 is corresponding to FIG. It is a chart showing. The size of the test piece was 100 × 100 × 100 mm, and a test piece having a thickness of 100 mm was used.

  As the material used, ordinary Portland cement specified in JIS R 5210 (Portland cement) was used. The general properties are as shown in FIG.

  The fine aggregate was river sand, the coarse aggregate was sandstone crushed stone, the mixing water was tap water, and the admixture was AE water reducing agent.

  Creation of material mortar is as follows. That is, cement, fine aggregate and tap water are used as materials, and mortar with 50% water cement ratio and 3 sand cement ratio is kneaded according to JSCE-F 505 (how to make mortar in the laboratory). Molding was performed using a 100 × 100 × 400 mm metal mold. Then, it was left still for one day at a temperature of 20 ± 2 ° C and a relative humidity of 80% or more, and was cured in water at 20 ± 2 ° C for 27 days. And it cut | disconnected with the concrete cutter to the predetermined dimension of the test piece shape, and also provided the notch groove with the concrete cutter of 2 mm of blade width.

  The production of the concrete material is as follows. In other words, cement, fine aggregate, coarse aggregate, tap water and admixture are used as materials, and concrete with a 50% water cement ratio is mixed in accordance with JIS A1138 (How to make concrete in a laboratory). Molding was performed using a 100 × 100 × 400 mm metal mold. Then, it was left still for one day at a temperature of 20 ± 2 ° C. and a relative humidity of 80% or more, and was cured in water at 20 ± 2 ° C. for 27 days. And it cut | disconnected with the concrete cutter to the predetermined dimension of the test piece shape, and also provided the notch groove 13 with the concrete cutter of 2 mm of blade width.

  The crack control method and apparatus are the same as those in FIG. 1 of Example 1, but the crack width is particularly controlled in the test piece for repair material evaluation, and therefore the crack width is controlled here.

  FIG. 39 is a perspective view of a test piece showing the length and width of a crack, and FIG. 40 is an enlarged perspective view of the main part.

As shown in FIGS. 39 and 40, crack length δ _A (δ _B ), width α _A (α _B ), etc. ( _{A and B} are measurements on one side and the other side in the thickness direction of the test piece. Are measured). The crack widths α _A and α _B were measured using a non-contact type biaxial measuring microscope (manufactured by Vision Engineering).

41 and 42 correspond to FIG. 8, FIG. 41 is a chart showing the results of the test specimen for evaluating the mortar crack repair material, and FIG. 42 is a chart showing the results of the test specimen for evaluating the concrete crack repair material. The widths α _A and α _B are added. In the implementation, the average crack width α _AB of α _A and α _B was controlled by being divided into the following three.

S: α _AB ≦ 0.15 mm, M: 0.15 mm <α _AB <0.30 mm, L: α _AB ≧ 0.30 mm
Figure 41, as shown in FIG. 42, mortar and concrete cracking repair material test piece for evaluation: For even thickness 100 mm, the test piece of FIG. 37, in the exemplary conditions in FIG 38, the breaking load _{P F} of FIG. 41 and 42 On the other hand, cracks could be stopped in the test piece. In addition, a test piece having an average crack width α _AB in accordance with the desired three categories was obtained.

  FIGS. 43 to 46 relate to the third embodiment, FIG. 43 is a schematic front view conceptually showing the crack control device, FIG. 44 is a chart corresponding to FIG. FIG. 46 is a chart corresponding to FIG. 7 and showing experimental conditions, and FIG. 46 is a chart corresponding to FIG.

In this embodiment, a load P ₁ is applied to the test piece 3 in the direction of opening the notch groove 13 to generate a crack 15 from the notch groove 13. Load of the load P _1, it is possible to use a tensile force applying device described in Patent Document 1 or the like.

Also in this example, the compressive load P ₀ was applied to the side surfaces 3e and 3f of the test piece 3 from the direction in which the opening of the notch groove 13 is regulated by the crack length setting tool 11.

As a result, for the acrylic CT test piece: thickness 20 mm, the crack length δmax could be controlled as shown in FIG. 46 using the test piece of FIG.
[Effect of Example]
The embodiment of the present invention is a crack control method for forming a crack 15 in a test piece 3 in which a notch groove 13 having a predetermined length is formed in the center of one side surface 3c of a rectangular body toward the other side surface 3d. A compression load P ₀ is applied to the side surface of the test piece 3 from the direction in which the opening of the notch groove 13 is regulated between the one side surface 3c and the other side surface 3d of the piece 3, and the side surfaces of the notch groove one side of the rectangular body supporting two points, the load P ₁ toward the other side notched groove 13 and the load to the two-point support, a three-point bending by the two-point support and the load P ₁ A crack 15 is generated from the notch groove 13 by being applied to the test piece 3, or a crack P is generated from the notch groove 13 by applying a load P ₁ in the direction of opening the notch groove 13 to the test piece 3. The crack control method is used.

  Therefore, it is not a technique to control the crack length by using frictional force, but it is possible to accurately control the crack length by applying a compressive load to the side surface of the test piece from the direction of regulating the opening of the notch groove. Can be done.

  In addition, the crack length is reliably controlled even when the thickness of the specimen is large, when the specimen is quite large, when the specimen is relatively small, or when the material has high strength such as cemented carbide. can do.

The test strip 3 can also be applied to thinner unless buckled and deformed by the load of the compressive load P _0.

  The embodiment of the present invention is a crack length setting tool 11 used in the crack control method, and includes first and second pressurizing portions 19 and 21 which are brought into contact with the side surfaces 3e and 3f of the test piece 3, and the first The crack length setting tool 11 includes the pressure driving units 23 and 25 that apply the compression load by moving the second pressure units 19 and 21 in the approaching direction.

  For this reason, if the thickness of the specimen is large, if the specimen is fairly large or relatively small, and even if the material has high strength such as cemented carbide, it is easy to apply a compressive load that controls the length of the crack. Can be loaded. The length and width of the crack can be controlled by changing the position λ of the notch groove 13 and the pressure plate 27, 29 from the bottom surface in FIG. 1 by changing the position of the crack length setting tool 11. .

  The first and second pressure units 19 and 21 are coupled to the pressure plates 27 and 29 that contact the side surfaces 3e and 3f of the test piece 3 and the pressure driving units 23 and 25, respectively. And pressurization bases 31 and 33 which are in contact with each other.

For this reason, the pressurization bases 31 and 33 are driven by the pressurization drive units 23 and 25, and the compression load P ₀ is applied to the test piece 3 through the pressurization plates 27 and 29 by the drive of the pressurization bases 31 and 33. be able to.

Therefore, the pressure plates 27 and 29 can be made into a shape and material suitable for applying the compressive load P ₀ to the test piece 3.

  The pressurization bases 31 and 33 have a mountain shape that protrudes toward the pressurization plates 27 and 29.

For this reason, the rigidity of the pressurization bases 31 and 33 can be ensured, and the compression load P ₀ can be reliably applied to the pressurization plate 27.

  A load transmitting ball 35 is interposed between the pressure plates 27 and 29 and the pressure tables 31 and 33.

Therefore, even if pressure圧台31 are slightly displaced posture relative to the pressure plate 27, it can be loaded accurately compressive load P ₀ to the side surface 3e of the pressure plate 27 via the pressure plate 27, pressure The compressive load P ₀ on the side surface 3f of the pressure plate 29 can be accurately applied.

  The pressure driving units 23 and 25 are arranged on both sides of the test piece 3 and are connected to the pressure tables 31 and 33 so as to fasten and move the pressure tables 31 and 33. 25a and nuts 23b and 25b.

  For this reason, the pressurization bases 31 and 33 can be easily driven by tightening the nuts 23b and 25b with respect to the bolts 23a and 25a.

  The embodiment of the present invention is a crack control device 1 used in the crack control method, wherein the other side surface receives a load from the support base 7 that performs the two-point support on the base 17 side and the load generating portion 5. It was set as the crack control apparatus 1 provided with the pressurization piece 9 which transmits to 3d as said center load.

For this reason, when the thickness of the test piece 3 is large, when the test piece is considerably large or relatively small, even when the material has high strength such as a cemented carbide, the load P ₁ is applied in the thickness direction of the test piece 3. It is possible to easily apply a bending load that gives the entire structure accurately and generates a crack from the notch groove 13.

As described above, the embodiment of the present invention has the following effects.
(1) Cracks can be easily introduced by using the presented jig (support 7 and pressure piece 9).
(2) Cracks can be introduced regardless of the thickness, size, and material strength of the specimen.
(3) Cracks can be stopped at the approximate desired position of each specimen.
(4) Cracks to be introduced can be introduced relatively straight.
(5) Cracks can be introduced not only in cemented carbide, which has been difficult to introduce cracks, but also in CT specimens made of gypsum, thick glass, acrylic and mortar.
(6) Cracks can be introduced not only in mortar but also in test pieces for evaluation of crack repair materials in concrete.

DESCRIPTION OF SYMBOLS 1 Crack control apparatus 3 Test piece 3c One side 3d Other side 3e, 3f Side 5 Load generation part 9 Pressurization piece 11 Crack length setting tool 13 Notch groove 15 Crack 17 Base 19 First pressurization part 21 2nd pressurization part 23, 25 Pressurization drive unit 27, 29 Pressurization plate 31, 33 Pressurization table 35 Ball P ₀ Compression load P ₁ Load

Claims (7)

A crack control method for forming a crack in a test piece in which a notch groove having a predetermined length is formed in the center of one side of a rectangular body toward the other side,
A compressive load is applied to the side surface of the test piece from the direction of regulating the opening of the notch groove between one side surface and the other side surface of the test piece,
One side of the test piece is supported at two positions on both sides of the notch groove, and a central load directed to the notch groove is applied to the other side with respect to the two-point support. Applying a three-point bend to the test piece to generate cracks from the notch groove,
Or, a load is applied to the test piece in the direction of opening the notch groove to generate a crack from the notch groove.
A crack control method characterized by that. A crack length setting tool for use in the crack control method according to claim 1,
First and second pressurizing parts to be brought into contact with the side surface of the test piece;
A pressurizing drive unit configured to move the first and second pressurizing units in directions close to each other and apply the compressive load;
A crack length setting tool characterized by comprising: The crack length setting tool according to claim 2,
The first and second pressurizing sections are a pressurizing plate that contacts the side surface of the test piece,
A pressurization table coupled to the pressurization drive unit and contacting the pressurization plate;
A crack length setting tool characterized by comprising: The crack length setting tool according to claim 3,
The pressurization table has a mountain shape that protrudes toward the pressurization plate.
A crack length setting tool characterized by that. The crack length setting tool according to claim 3 or 4,
A load transmitting ball is interposed between the pressure plate and the pressure table.
A crack length setting tool characterized by that. The crack length setting tool according to any one of claims 2 to 5,
The pressure driving unit is a fastener that is disposed on both sides of the test piece and is coupled to the pressure table to move the pressure table.
A crack length setting tool characterized by that. A crack control device used in the crack control method according to claim 1,
A support base for performing the two-point support on the base side;
A pressure piece that receives a load from a load generation portion and transmits the load to the other side surface as the central load;
A crack control device characterized by comprising:

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