JP2016038381A - Detection method of crack using viscous fluid, and viscous fluid for crack detection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detection method of crack using viscous fluid for easily and certainly detecting, by application of the viscous fluid, a fine crack in an initial stage and a crack occurring in a complicated shape part such as a welded part or structure connecting part, and to provide viscous fluid for crack detection.SOLUTION: Viscous fluid 2 having a high thixotropic property is applied to a base material 1 on which a load repeatedly acts. Occurrence or evolution of a crack 3 is detected on the basis of a recess 5 in the external surface of the viscous fluid 2 formed by suction of the viscous fluid 2 into a crack 3 by opening/closing of the crack 3 in the base material 1 and/or a texture 6 of the base material 1 exposed by the recess 5.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a crack detection method and a crack caused by a viscous fluid, which are applied to a place where a crack is likely to occur or propagate in a structure such as a ship, an offshore structure, a bridge, a vehicle, a machine tool, or a building. The present invention relates to a viscous fluid for detection.

  The inspection of cracks in various structures such as ships, offshore structures, bridges, vehicles, machine tools, buildings, etc. currently depends mostly on visual inspection, but the inspection environment for actual structures is more severe than expected. In addition to limited space and time, there are many cases where a power supply and sufficient lighting equipment cannot be expected, so cracks that occur in complicated shapes such as welds and structural joints are found on site and the dimensions are grasped. Things are not easy.

In Patent Document 1, a second coating layer not containing microcapsules is provided on a first coating in which microcapsules enclosing a visibility liquid are dispersed on the surface of a structure, and the second coating layer is transparent. In addition, when a crack occurs in the first covering layer, a covering layer having an outermost layer having sufficient flexibility not to cause a crack is formed. By being transmitted to one coating layer, the microcapsules in the first coating layer are destroyed along with it, and the visibility liquid flowing out of the microcapsules reaches the second coating layer through the cracks in the first coating layer. A coating for crack inspection of a structure that allows detection of the occurrence of cracks in the structure is described.
Patent Document 2 discloses a first coating layer having a predetermined color tone and a color tone different from that of the first coating layer at a location where cracks on the structure are likely to occur. When the second coating layer that conceals the first coating layer is formed and a crack is generated in the structure, the first coating layer is formed from the gap between the cracks of the second coating layer that is generated along with the crack. A method for detecting the occurrence of cracks in a structure by sensing color is described.
In Patent Document 3 and Patent Document 4, the surface of a structure such as cracked concrete or mortar is wetted with a volatile liquid so that the volatile liquid is volatilized and the normal portion of the dried surface is volatilized. It has proposed a method for detecting cracks on the surface based on the difference in color from the cracks on the surface where the ionic liquid is hard to evaporate and is still wet.
Patent Document 5 includes a polymer and a fluorescent brightening agent, and includes a first layer formed on the surface side of the concrete, a polymer and an ultraviolet absorber, and is formed on the surface side of the first layer. It is described that a cracked and cracked concrete structure provided with a second layer is irradiated with ultraviolet rays to confirm the position of the crack.

International Publication No. 2005/001454 JP 10-38692 A JP-A-1-295142 JP 2005-195564 A JP 2013-88405 A

In the method of using a paint as in Patent Document 1 or 2, it takes time and effort to perform the pre-painting base treatment work or the coating film removal work after the inspection. Further, in many cases, it is not possible to perform recoating on an existing coating film, for example, when an organic solvent-based paint is used or when the compatibility of the paint does not match. In addition, the method of Patent Document 1 requires special techniques and equipment for manufacturing microcapsules enclosing a visibility liquid.
According to the method using a volatile liquid as in Patent Document 3 or 4, the liquid in the crack is also volatilized in a relatively short time, and the color of the crack portion and the normal portion becomes the same, so that the crack cannot be detected. In addition, the volatilization rate depends greatly on the surrounding environment such as the air temperature, and it is necessary to deal with it. In addition, when applied to a vertical surface or the like, there is a risk that the volatile liquid will sag. Furthermore, it is a structure in which a crack has already occurred, and cannot be applied to a site where the occurrence or development of a crack is predicted in the future.
The concrete structure of Patent Document 5 requires an ultraviolet irradiator that irradiates ultraviolet rays, and requires a lot of work.

  Accordingly, the present invention provides a method for detecting cracks caused by viscous fluid, which easily and surely detects micro-cracks in the initial stage and cracks generated in complicated shapes such as welded parts and structural joints by applying viscous fluid. And a viscous fluid for crack detection.

In the crack detection method using a viscous fluid corresponding to the present invention according to claim 1, the viscous fluid having high thixotropic property is applied to a base material to which a load is repeatedly applied, and the viscous fluid is formed by opening and closing the crack of the base material. It is characterized in that the occurrence or development of a crack is detected from the depression of the outer surface of the viscous fluid formed by sucking into the inside of the crack and / or the ground of the base material exposed by the depression.
According to the first aspect of the present invention, the viscous fluid having a high thixotropic property applied to the base material in which cracks are a concern is highly viscous at the surface of the base material without causing sagging in a portion where there is no crack. In the vicinity of a crack that retains its shape and opens and closes due to the action of repeated loads, the shear rate of the viscous fluid increases and the viscosity decreases, so that the fluidity increases, and the viscous fluid near the crack is caused by the pumping action and capillary action of the crack. Along with being sucked into the crack, a viscous dent is formed in the viscous fluid in the vicinity of the crack, so by observing this dent, or the background of the base material exposed by the dent, the crack in the matrix can be removed. It can be easily detected visually.

The present invention described in claim 2 includes a step 1 for preparing a viscous fluid having a high thixotropic property and a base material, a step 2 for specifying a predicted portion of the base material where a crack is predicted to be generated, and a specified base material. Step 3 in which viscous fluid is applied to a predicted portion of the material, Step 4 in which a load is repeatedly applied to the base material to which the viscous fluid has been applied, and a mother exposed by a dent and / or a dent in the outer surface of the viscous fluid in the predicted portion. And step 5 for visually detecting the occurrence of cracks from the surface of the material.
According to the second aspect of the present invention, a viscous fluid can be applied to a site where cracking is predicted in advance, and the viscous fluid having high thixotropic property applied to the specified predicted region of the base material is In the absence of cracks, the fluid retains its shape on the surface of the base material without causing sagging due to high viscosity, and in the vicinity of a crack that opens and closes due to the action of repeated loads, the shear rate of the viscous fluid increases and the viscosity decreases. Since the viscous fluid near the crack is sucked into the crack due to the pumping action and capillary action of the crack, the viscous fluid near the crack forms a remarkable dent. By observing the background of the exposed base material, it is possible to easily detect the portion where the crack is generated in the base material by visual observation.
The predicted portion of the base material where the occurrence of a crack is predicted refers to a predicted portion where the occurrence of a crack is predicted or a portion including a predicted portion where the occurrence of a crack is predicted and its periphery.

According to a third aspect of the present invention, in performing step 3, the pre-coating ground treatment is not performed on the base material before the viscous fluid is applied.
According to the third aspect of the present invention, it is not necessary to perform pre-coating ground treatment on the base material before applying the viscous fluid having high thixotropic properties, and the working time can be shortened.

The present invention according to claim 4 is characterized in that, in step 3, the viscous fluid is applied to the base material on the applied coating layer.
According to this invention of Claim 4, the operation | work which peels off the existing coating film of a base material is unnecessary, and can shorten work time.

According to the fifth aspect of the present invention, in performing Step 3, the base material before applying the viscous fluid or the coating film already applied to the base material is colored with a color different from the color of the viscous fluid. Features.
According to the fifth aspect of the present invention, the contrast between the color of the viscous fluid and the background of the base material or the colored color of the coating film is behind the dent formed in the viscous fluid due to the crack generated in the base material. Visibility when the background or coating film of the base material is visible is improved.

The present invention according to claim 6 further includes step 6 of removing the applied viscous fluid after detecting the occurrence of a crack in step 5.
According to the sixth aspect of the present invention, the highly thixotropic viscous fluid applied to the base material can be easily removed.

The present invention according to claim 7 is characterized in that, in selecting the viscous fluid in step 1, it is selected in consideration of the influence of the frequency of the repeated load applied to the base material on the shear rate and the apparent viscosity of the viscous fluid. To do.
According to the seventh aspect of the present invention, it is possible to more appropriately select the viscous fluid that detects the occurrence of cracks in the base material without causing sagging in consideration of the frequency of the repeated load applied to the base material. it can.

The present invention according to claim 8 provides a step 7 of preparing a viscous fluid having a high thixotropic property and a base material in which a crack is generated, and a viscosity at a crack portion of the base material and / or a predicted growth portion of the crack. Step 8 where fluid is applied, Step 9 where a load is repeatedly applied to the base material to which the viscous fluid has been applied, and dents on the outer surface of the viscous fluid and / or crack growth from the base material exposed by the dents And a step 10 of detecting by the above.
According to the present invention described in claim 8, the viscous fluid having high thixotropic property applied to the crack portion of the crack of the base material and / or the predicted growth portion of the crack has a high viscosity at a portion where there is no crack. Maintains the shape on the surface of the base material without causing sagging, and in the vicinity of the crack that opens and closes due to the action of repeated loads, the shear rate of the viscous fluid increases and the viscosity decreases, so the fluidity increases, the crack pumping action and The viscous fluid near the crack is sucked into the crack due to the capillary phenomenon, and a remarkable dent is formed in the viscous fluid near the crack. Observe the dent or the base material exposed by the dent. Thus, the progress of cracks in the base material can be easily detected visually.
In addition, the crack part of the crack to which the viscous fluid is applied means a part including the crack and its periphery, and the crack prediction part is a part including the prediction part where the crack is predicted and the periphery thereof. Say.

The present invention according to claim 9 is characterized in that in performing step 8, the pre-coating base treatment is not performed on the base material before the viscous fluid is applied.
According to the ninth aspect of the present invention, it is not necessary to perform pre-coating ground treatment on the base material before applying the viscous fluid having high thixotropic properties, and the working time can be shortened.

The present invention according to claim 10 is characterized in that, in step 8, the viscous fluid is applied to the base material in a layered manner on the coated film.
According to the tenth aspect of the present invention, the work of peeling off the existing coating film of the base material is unnecessary, and the working time can be shortened.

According to the eleventh aspect of the present invention, in performing step 8, the base material before applying the viscous fluid or the coating film already applied to the base material is colored with a color different from that of the viscous fluid. Features.
According to the eleventh aspect of the present invention, the contrast between the color of the viscous fluid and the background of the base material or the colored color of the coating film is behind the dent formed in the viscous fluid due to the progress of cracks in the base material. Visibility when the background or coating film of the base material is visible is improved.

The present invention according to claim 12 is characterized by further comprising step 11 of removing the applied viscous fluid after detecting the progress of the crack in step 10.
According to this invention of Claim 12, the highly thixotropic viscous fluid apply | coated to the preform | base_material can be removed easily.

The present invention according to claim 13 is characterized in that, in selecting the viscous fluid in step 7, it is selected in consideration of the influence of the frequency of the repeated load applied to the base material on the shear rate and the apparent viscosity of the viscous fluid. To do.
According to the present invention described in claim 13, it is possible to more appropriately select a viscous fluid that detects the progress of a crack in the base material without causing sagging in consideration of the frequency of a repeated load applied to the base material. it can.

The thirteenth aspect of the present invention is characterized in that a thixotropic index TI representing a high thixotropic property of a viscous fluid is 0.3 to 1.7.
According to the present invention described in claim 14, it is suitable as a crack detection viscous fluid for detecting a crack.

In the present invention according to claim 15, the apparent viscosity η _G of the viscous fluid is 31 (Pa · s) or more when the shear rate is 0.1 (1 / s), and the shear rate is 1 (1 / s). 4.8 to 280 (Pa · s).
According to this invention of Claim 15, the high viscosity in a location without a crack is realizable, and a shape can be hold | maintained, without producing sagging.

In the present invention according to claim 16, the apparent viscosity η _G of the viscous fluid is 0.7 to 37 (Pa · s) when the shear rate is 10 (1 / s), and the shear rate is 100 (1 / s). In this case, it is 0.11 to 4.9 (Pa · s).
According to the present invention as set forth in claim 16, the viscosity in the vicinity and inside of the crack is lowered, the fluidity of the viscous fluid is increased, and the fluid easily enters the crack, and is formed on the outer surface of the viscous fluid. A crack can be visually detected by the dent and / or the background of the base material exposed by the dent.

The present invention according to claim 17 is characterized in that the base material is selected from metal, plastic, composite material, concrete, wood and ceramics.
According to the present invention of the seventeenth aspect, a base material in which a crack may occur or develop due to a repeated load can be an inspection target.

The viscous fluid for crack detection corresponding to the present invention according to claim 18 is characterized by being used in a crack detection method using a viscous fluid.
According to the eighteenth aspect of the present invention, a highly thixotropic viscous fluid can be used for crack detection.

The present invention according to claim 19 is characterized in that the viscous fluid is a paste having high thixotropic properties.
According to the nineteenth aspect of the present invention, a paste having high thixotropic properties can be used for detection of cracks.

The present invention according to claim 20 is characterized in that the viscous fluid is a mixture of fluid and powder.
According to the 20th aspect of the present invention, it is possible to use a mixture of fluid and powder having high thixotropic properties for detection of cracks and to suppress the progress of cracks by the powder.

The present invention according to claim 21 is characterized in that the viscous fluid is a silicone-based viscous fluid.
According to the twenty-first aspect of the present invention, a silicone-based viscous fluid having high thixotropic properties can be used for detection of cracks.

The present invention according to claim 22 is characterized in that the viscous fluid is a pale viscous fluid including white.
According to the twenty-second aspect of the present invention, it becomes easy to visually detect the dent formed on the outer surface of the viscous fluid due to the crack of the base material and the background of the base material exposed by the dent.

According to a twenty-third aspect of the present invention, the viscous fluid is a viscous fluid having a viscosity characteristic selected in consideration of a frequency of a repeated load applied to the assumed base material.
According to the present invention as set forth in claim 23, cracks are generated under the frequency of a repetitive load applied to the base material assuming a viscous fluid having a viscosity characteristic for detecting the occurrence of cracks in the base material without causing sagging. It can be used for detection.

  According to the method for detecting cracks with a viscous fluid of the present invention, a viscous fluid having high thixotropic properties applied to a base material in which cracks are a concern is a base material that has high viscosity and does not sag in a portion where there is no crack. In the vicinity of a crack that retains its shape on the surface and opens and closes under the action of repeated loads, the shear rate of the viscous fluid increases and the viscosity decreases, so that the fluidity increases, and the viscosity near the crack is increased by the pumping action and capillary action of the crack. Since the fluid is sucked into the crack and the viscous fluid in the vicinity of the crack has a remarkable dent, by observing the dent or the base material exposed by the dent, Cracks can be easily detected visually.

  In addition, step 1 for preparing a viscous fluid having high thixotropic properties and a base material, step 2 for specifying a predicted part of the base material in which cracks are predicted to occur, and a viscous fluid in the specified predicted part of the base material , Step 4 in which a load is repeatedly applied to the base material to which the viscous fluid has been applied, and dents on the outer surface of the viscous fluid at the predicted site and / or generation of cracks from the ground of the base material exposed by the dents And the step 5 for visually detecting the viscous fluid can be applied in advance to the site where cracks are predicted to occur, and has a high thixotropic property applied to the predicted site of the specified base material. Viscous fluid has a high viscosity where there is no crack and maintains its shape on the surface of the base material without causing sagging. As the velocity increases and the viscosity decreases, the fluidity increases, and the viscous fluid near the crack is sucked into the crack due to the pumping action and capillary action of the crack. Therefore, by observing the dent or the background of the base material exposed by the dent, it is possible to easily detect the portion where the crack is generated in the base material by visual observation.

  In addition, in performing step 3, when the pre-coating base treatment is not performed on the base material before the viscous fluid is applied, the pre-painting on the base material before applying the viscous fluid having a high thixotropic property is performed. No ground processing is required, and the working time can be shortened.

  Further, in the case where the viscous fluid is applied to the base material over the already applied coating in Step 3, it is not necessary to remove the existing coating on the base material, and the work time can be shortened. it can.

  In addition, when performing step 3, when coloring a color different from the color of the viscous fluid to the base material before applying the viscous fluid or the coating film already applied to the base material, the color of the viscous fluid Visibility is improved when the background of the base material or the coating film is visible behind the dent formed in the viscous fluid due to the crack generated in the base material due to the contrast with the base color of the base material or the colored color of the coating film. .

  In addition, after the occurrence of cracks in step 5 is detected, when step 6 for removing the applied viscous fluid is further provided, the highly thixotropic viscous fluid applied to the base material can be easily removed. .

  Further, when selecting the viscous fluid in step 1 in consideration of the influence of the frequency of the repeated load applied to the base material on the shear rate and the apparent viscosity of the viscous fluid, the base material does not cause sagging. It is possible to more appropriately select a viscous fluid that detects the occurrence of cracks therein.

  A step 7 of preparing a viscous fluid having a high thixotropic property and a base material in which a crack has occurred, and a step 8 of applying a viscous fluid to a crack portion of the base material and / or a predicted progress portion of the crack; Step 9 in which a load is repeatedly applied to the base material to which the viscous fluid is applied, and Step 10 for visually detecting the progress of a crack from the dent of the outer surface of the viscous fluid and / or the base material exposed by the dent. In the case where it is provided, the viscous fluid having high thixotropic property applied to the crack portion of the base material and / or the predicted growth portion of the crack has a high viscosity and does not cause sagging in a portion where there is no crack. In the vicinity of a crack that retains its shape on the surface of the material and opens and closes under the action of repeated loads, the shear rate of the viscous fluid increases and the viscosity decreases. The viscous fluid near the crack is sucked into the crack due to the capillary phenomenon, and a remarkable dent is formed in the viscous fluid near the crack. Observe the dent or the base material exposed by the dent. Thus, the progress of cracks in the base material can be easily detected visually.

  In addition, when performing the pre-painting base treatment on the base material before applying the viscous fluid when executing step 8, before applying the base material before applying the viscous fluid having a high thixotropic property. No ground processing is required, and the working time can be shortened.

  In addition, in step 8, when the viscous fluid is applied to the base material overlying the coated film, it is not necessary to remove the existing coating film on the base material, and the working time can be shortened. it can.

  In addition, when executing step 8, when coloring the base material before applying the viscous fluid or the coating film already applied to the base material with a color different from the color of the viscous fluid, Visibility is improved when the background of the base material or the coating film is visible behind the dent formed in the viscous fluid due to the development of cracks in the base material due to the contrast with the colored background of the base material or the coating film. .

  In addition, after detecting the progress of the crack in step 10, when the step 11 for removing the applied viscous fluid is further provided, the highly thixotropic viscous fluid applied to the base material can be easily removed. .

  Further, when selecting the viscous fluid in step 7 in consideration of the influence of the frequency of the repeated load applied to the base material on the shear rate and the apparent viscosity of the viscous fluid, the base material does not cause sagging. It is possible to more appropriately select a viscous fluid that detects the progress of cracks therein.

  Further, when the thixotropic index TI representing the high thixotropic property of the viscous fluid is 0.3 to 1.7, it is suitable as a crack detection viscous fluid for detecting a crack.

The apparent viscosity η _G of the viscous fluid is 31 (Pa · s) or more when the shear rate is 0.1 (1 / s), and 4.8 to 280 when the shear rate is 1 (1 / s). In the case of (Pa · s), a high viscosity can be achieved at a crack-free location, and the shape can be maintained without sagging.

The apparent viscosity η _G of the viscous fluid is 0.7 to 37 (Pa · s) when the shear rate is 10 (1 / s), and 0.11 to 0.1 when the shear rate is 100 (1 / s). When it is set to 4.9 (Pa · s), the viscosity in the vicinity and inside of the crack is lowered, the fluidity of the viscous fluid is increased, and it is easy to enter the crack, forming on the outer surface of the viscous fluid. The crack can be visually detected by the dent and / or the background of the base material exposed by the dent.

  In addition, when the base material is selected from metal, plastic, composite material, concrete, wood, and ceramics, the base material in which cracks may occur or develop due to repeated loads can be the inspection target. .

  According to the viscous fluid for detecting cracks of the present invention, a highly thixotropic viscous fluid can be used for detecting cracks.

  Further, when the viscous fluid is a paste having high thixotropic properties, the paste having high thixotropic properties can be used for detection of cracks.

  In addition, when the viscous fluid is a mixture of fluid and powder, the mixture of fluid and powder with high thixotropic properties can be used for crack detection, and the development of cracks is suppressed by the powder. It becomes possible to do.

  When the viscous fluid is a silicone-based viscous fluid, a silicone-based viscous fluid having high thixotropic properties can be used for detection of cracks.

  Further, when the viscous fluid is a light colored viscous fluid including white, it is possible to visually detect a dent formed on the outer surface of the viscous fluid due to a crack in the matrix or the base material exposed by the dent. It becomes easy.

  In addition, when the viscous fluid is a viscous fluid having a viscosity characteristic selected in consideration of the frequency of the repeated load applied to the assumed base material, the viscosity for detecting the occurrence of cracks in the base material without causing sagging It can be used for crack detection under the frequency of repeated load applied to the base material assuming a viscous fluid having characteristics.

Explanatory drawing which shows the action principle of the crack detection by the viscous fluid which has high thixotropic property by embodiment of this invention Table showing viscous fluid composition and relative viscosity of viscous fluid in each example of viscous fluid having high thixotropic properties according to an embodiment of the present invention Characteristic diagram showing the relationship between apparent viscosity of viscous fluid and spindle rotation speed Characteristic diagram showing the relationship between apparent viscosity and shear rate of viscous fluid Characteristic diagram showing the relationship between apparent viscosity and shear rate of viscous fluid at 0.167 times the viscous fluid viscosity of Example 1 to 6 times the viscous fluid viscosity of Example 2 Table showing apparent viscosity and viscous fluid thixotropy index by shear rate in the same viscosity range The characteristic diagram which shows the relationship between the apparent viscosity of a viscous fluid and a shear rate in 0.25 times the viscous fluid viscosity of Example 1-4 times the viscous fluid viscosity of Example 2 Table showing apparent viscosity and viscous fluid thixotropy index by shear rate in the same viscosity range Characteristic diagram showing the relationship between apparent viscosity and shear rate of viscous fluid from 0.4 times the viscous fluid viscosity of Example 1 to 2.5 times the viscous fluid viscosity of Example 2 Table showing apparent viscosity and viscous fluid thixotropy index by shear rate in the same viscosity range Diagram showing notched flat plate test piece used for crack growth test Table showing test results for Comparative Example 1 and Tests 1-5 Photo showing the state during the crack growth test in Comparative Example 1 Photograph showing change of viscous fluid during crack growth test in Test 1 The figure which shows the relationship between the dent length of a viscous fluid, and the actual crack length from the test result of Test 1. Photograph showing change of viscous fluid during crack growth test in Test 2 The figure which shows the relationship between the dent length of a viscous fluid, and the actual crack length from the test result of Test 2. Photograph showing change of viscous fluid during crack growth test in Test 3 The figure which shows the relationship between the dent length of a viscous fluid, and the actual crack length from the test result of Test 3. Photograph showing change of viscous fluid during crack growth test in Test 4 The figure which shows the relationship between the dent length of a viscous fluid, and the actual crack length from the test result of Test 4. Photograph showing change of viscous fluid during crack growth test in Test 5 The figure which shows the relationship between the dent length of a viscous fluid, and the actual crack length from the test result of Test 5.

FIG. 1 is an explanatory diagram showing an operation principle of crack detection by a viscous fluid having high thixotropic properties according to an embodiment of the present invention.
FIG. 1A shows a state in which a viscous fluid 2 having high thixotropic properties is applied to a vertical surface of a base material 1 such as a metal substrate. The viscous fluid 2 may be applied by brushing or applicator coating, or by dipping or spraying. In a state where the viscous fluid 2 is simply applied to the base material 1, since the shear rate is zero, the viscous fluid 2 has a high viscosity and maintains its shape without causing sagging or deformation.

  FIG. 1B shows an initial crack generation state in which a crack 3 is generated by the action of a repeated load and an opening / closing port is started on the surface of the base material 1. The viscosity of the viscous fluid 2 in the vicinity of the crack opening is increased and the viscosity is decreased to become a medium / low-viscosity viscous fluid 4, and the fluidity is increased, so that the fluid can easily enter the crack 3.

FIG.1 (c) has shown the state where the opening and closing port of the crack 3 became active. In the range affected by the movement of the opening / closing opening of the crack 3, the shear rate of the viscous fluid 2 increases, the viscosity decreases, and the fluid becomes a medium / low viscosity viscous fluid 4, and the fluidity increases, and the medium / low viscosity viscous fluid 4 Flows into the crack 3 and it becomes easier to form a recess 5 wider than the crack 3 on the outer surface. The occurrence of the crack 3 in the base material 1 can be easily detected by observing the wide recess 5.
On the other hand, since the viscous fluid 2 located at a certain distance from the crack 3 remains highly viscous, the shape of the viscous fluid 2 as a whole is maintained without sagging or deformation.

  FIG. 1D shows a state where the recess 5 of the viscous fluid 4 is further deepened. Eventually, the background 6 of the base material 1 near the crack 3 becomes exposed. On the other hand, since the viscous fluid 2 located at a certain distance from the crack 3 remains highly viscous, the shape of the viscous fluid 2 as a whole is maintained without sagging or deformation. In addition, when the relatively low-viscosity viscous fluid 2 is applied thinly, the background 6 of the base material 1 is easily visible, and the visibility is further improved. Moreover, if it coat | coats so that the outer surface of the viscous fluid 2 may become as flat as possible, the dent 5 will become easy to detect.

As described above, the viscous fluid 2 having high thixotropic property has a shape on the surface of the base material 1 without maintaining a high viscosity at a portion where the crack 3 is not present and the shear rate is extremely small (including zero) and no sagging occurs. In the vicinity of the crack 3 that is held and opened and closed with the action of repeated load, the shear rate of the viscous fluid 2 increases and the viscosity decreases, so that the fluidity increases, and the viscosity in the vicinity of the crack 3 is caused by the pump action and capillary action of the crack 3. In combination with the suction of the fluid 4 into the crack 3, a remarkably wide recess 5 is formed in the viscous fluid 4 near the crack 3. Accordingly, the viscous fluid 2 having a high thixotropic property is applied to the base material 1 on which a load is repeatedly applied, and the viscous fluid 4 is sucked into the crack 3 by opening and closing the crack 3 of the base material 1. The crack 3 in the base material 1 is easily detected visually by detecting the occurrence or progress of the crack 3 from the wide recess 5 on the outer surface of the fluid 4 and / or the ground 6 of the base material 1 exposed by the recess 5. can do.
If the crack 3 opens and closes and the shear rate of the viscous fluid 2 near the crack 3 increases, a wide recess 5 is formed on the outer surface in a relatively short time. The time lag between is short.

As a first step, a viscous fluid 2 having high thixotropic properties and a base material 1 to be detected are prepared.
FIG. 2 is a table showing configurations and relative viscosities in respective examples of viscous fluids having high thixotropic properties according to an embodiment of the present invention.
As the viscous fluid 2 having high thixotropic properties, grayish white silicone grease or a mixture of grayish white silicone grease and transparent silicone oil was used. As described above, as the highly thixotropic viscous fluid 2 for crack detection, a silicone-based viscous fluid (such as grease) that can be obtained relatively easily can be used. As the viscous fluid 2, it is possible to use all greases including silicone grease, all greases and oil mixtures, various creams, and various pastes. Silicone greases having low temperature dependence of viscosity and chemically stable are suitable. . However, the thixotropy index TI of general silicone grease, silicone oil, or a mixture thereof, which is a target silicone fluid as the viscous fluid 2, varies from large to small. As a viscous fluid, it is necessary to narrow down and use it.
Further, when the viscous fluid 2 is white (light color) and opaque, it is easier to visually detect the dent 5 formed on the outer surface of the viscous fluid 2 due to the crack 3 of the base material 1 and the background 6 of the base material 1. However, this does not apply depending on the color of the base material 1 to be detected, the color of the coating film applied to the surface of the base material 1, and the colored color.

Figure 3 is a characteristic diagram showing the relationship between the rotational speed N _R of the viscosity eta _G and spindle apparent viscous fluid, the viscous fluid 2 of Examples 1 to 3 of FIG. 2, the viscosity eta _G at room temperature, B type The measurement result is shown using a rotary viscometer (Viscolead one manufactured by Fungilab, using R7 spindle).
In common with the first to third embodiments, the apparent viscosity η _G decreases as the rotational speed N _{R of the} spindle increases and the shear rate increases, and linear regression is performed by the least square method on the logarithmic coordinates. The slopes of the straight lines in Examples 1, 2, and 3 are −0.82, −0.88, and −0.87, respectively, indicating high thixotropic characteristics.
FIG. 4 is a characteristic diagram showing the relationship between the apparent viscosity η _G and the shear rate D of the viscous fluid. The horizontal axis spindle rotation speed N _R (rpm) in FIG. 3 is converted into the shear rate D (1 / s). It is a thing.

The thixotropic index TI showing the thixotropic characteristic in the present invention is defined as follows.
TI = − [Slope of regression line in FIG. 4 (relationship of apparent viscosity η _G −shear rate D expressed in double logarithmic coordinates)]
In Section 5.2 of the Japanese Industrial Standard JIS Z3284-1994 Solder Paste, a method for obtaining the thixotropy index TI from the viscosity-shear rate (shear rate) curve is shown. In this method, a straight line passing through two specific points is shown. It is defined by the slope of. The thixotropy index TI in the present invention is the same as the method defined by this JIS, but is not defined by the slope of a straight line passing through two specific points.

FIG. 5 is a characteristic diagram showing the relationship between the apparent viscosity η _G and the shear rate D from 0.167 times the viscous fluid viscosity of Example 1 to 6 times the viscous fluid viscosity of Example 2, and FIG. It is a table | surface which shows the apparent viscosity (eta) _G and the thixotropy index TI of a viscous fluid according to the shear rate D in the range.
In addition, “Adhesives and Adhesive Technology” CMC Technical Library 272, supervised by Koji Nagata, (FIG. 7 on p. 313) describes the shear rate history of the paint and should be considered with respect to sagging and sedimentation stability. The range of the shear rate is about 0.01 to 1 (1 / s), and the range of the shear rate to be considered for the conveyance and coating of the paint is about 10 to 100 (1 / s).
Referring to this, the range of the shear rate D = 0.01 to 1 (1 / s) corresponds to the viscous fluid 2 applied to the portion without the crack 3, and it is applied without causing sagging even on a vertical surface or the like. It retains the shape of the time and exhibits the ability to withstand mild environmental factors such as moisture (rainwater, swaying water).
Further, the range of the shear rate D = 10 to 100 (1 / s) corresponds to the vicinity of the crack 3 and the viscous fluid 2 in the crack 3, reduces the viscosity, increases the fluidity, and sucks into the crack 3. And exerts the function of generating dents.

  From this, the shear rate D (1 / s) at the location without the crack 3 is set to D ≦ 0.1 and D = 1, and the shear rate D (1 / s) in the vicinity of the crack 3 and inside is D = 10 and D = 100.

  In FIG. 5, the square indicates the measurement value of Example 1, the circle indicates the measurement value of Example 2, and the triangle indicates the measurement value of Example 3. Moreover, the solid line thick line shown by "Example 2 * 6.0" has shown the viscosity upper limit, and the broken line thick line shown by "Example 1 * 0.167" has shown the viscosity minimum.

The upper limit of TI, which is the upper limit value of the thixotropy index TI, can be defined by the shear rate D = 1 (1 / s) in a straight line due to the upper limit of viscosity and the shear rate D = 100 (1 / s) in a straight line due to the lower limit of viscosity.
Further, the lower limit of the TI, which is the lower limit value of the thixotropy index TI, is determined by the shear rate D = 0.1 (1 / s) in the straight line due to the lower viscosity limit and the shear rate D = 100 (1 / s) in the straight line due to the upper limit of viscosity. Can be defined.
As shown by the slope of the straight line between the TI upper limit and the TI lower limit, the thixotropy index TI of the viscous fluid 2 is 0.3 to 1.7.

  As described above, if the thixotropic index TI representing the high thixotropic property of the viscous fluid 2 is 0.3 to 1.7, it is suitable as a crack detection viscous fluid for detecting the crack 3.

The apparent viscosity η _G of the viscous fluid 2 is 31 (Pa · s) or more when the shear rate D is 0.1 (1 / s) or less, and 4 when the shear rate D is 1 (1 / s). By setting it to .8 to 280 (Pa · s), it is possible to realize a high viscosity at a portion where there is no crack 3 and to maintain the shape without causing sagging.
The apparent viscosity η _G of the viscous fluid 2 is 0.7 to 37 (Pa · s) when the shear rate D is 10 (1 / s), and is 0 when the shear rate D is 100 (1 / s). .11 to 4.9 (Pa · s) reduces the viscosity in the vicinity or inside of the crack 3, increases the fluidity of the viscous fluid, and makes it easier to enter the crack 3. The crack 3 can be visually detected by the dent 5 and / or the ground 6 of the base material 1 exposed by the dent 5 formed on the outer surface.

FIG. 7 is a characteristic diagram showing the relationship between the apparent viscosity η _G and the shear rate D from 0.25 times the viscosity fluid viscosity of Example 1 to 4 times the viscosity fluid viscosity of Example 2, and FIG. It is a table | surface which shows the apparent viscosity (eta) _G and the thixotropy index TI of a viscous fluid according to the shear rate D in the range.
As in the case shown in FIG. 6, the shear rate D (1 / s) in the portion where there is no crack 3 is D ≦ 0.1 and D = 1, and the shear rate D (1 / s) in the vicinity of and inside the crack 3. ), D = 10 and D = 100.

  In FIG. 7, the square indicates the measurement value of Example 1, the circle indicates the measurement value of Example 2, and the triangle indicates the measurement value of Example 3. Moreover, the solid line thick line shown by "Example 2 * 4.0" shows the viscosity upper limit, and the broken line thick line shown by "Example 1 * 0.25" shows the viscosity lower limit.

The upper limit of TI, which is the upper limit value of the thixotropy index TI, can be defined by the shear rate D = 1 (1 / s) in a straight line due to the upper limit of viscosity and the shear rate D = 100 (1 / s) in a straight line due to the lower limit of viscosity.
Further, the lower limit of the TI, which is the lower limit value of the thixotropy index TI, is determined by the shear rate D = 0.1 (1 / s) in the straight line due to the lower viscosity limit and the shear rate D = 100 (1 / s) in the straight line due to the upper limit of viscosity. Can be defined.
As indicated by the slope of the straight line between the TI upper limit and the TI lower limit, the thixotropy index TI of the viscous fluid 2 is 0.4 to 1.5.

  As described above, when the thixotropic index TI representing the high thixotropic property of the viscous fluid 2 is 0.4 to 1.5, it is more suitable as a crack detection viscous fluid for detecting the crack 3.

The apparent viscosity η _G of the viscous fluid 2 is 47 (Pa · s) or more when the shear rate D is 0.1 (1 / s) or less, and 7 when the shear rate D is 1 (1 / s). By setting it to .2 to 190 (Pa · s), it is possible to realize a high viscosity at a portion where there is no crack 3 and to maintain the shape without causing sagging.
The apparent viscosity η _G of the viscous fluid 2 is 1.1 to 25 (Pa · s) when the shear rate D is 10 (1 / s), and is 0 when the shear rate D is 100 (1 / s). .17 to 3.2 (Pa · s) reduces the viscosity in the vicinity or inside of the crack 3, increases the fluidity of the viscous fluid, and makes it easier to enter the crack 3. The crack 3 can be visually detected by the dent 5 and / or the ground 6 of the base material 1 exposed by the dent 5 formed on the outer surface.

FIG. 9 is a characteristic diagram showing the relationship between the apparent viscosity η _G and the shear rate D between 0.4 times the viscous fluid viscosity of Example 1 and 2.5 times the viscous fluid viscosity of Example 2, and FIG. It is a table | surface which shows the apparent viscosity (eta) _G and the thixotropy index | exponent TI of a viscous fluid according to the shear rate D in the same viscosity range.
As in the case shown in FIG. 6, the shear rate D (1 / s) in the portion where there is no crack 3 is D ≦ 0.1 and D = 1, and the shear rate D (1 / s) in the vicinity of and inside the crack 3. ), D = 10 and D = 100.

  In FIG. 9, the square indicates the measurement value of Example 1, the circle indicates the measurement value of Example 2, and the triangle indicates the measurement value of Example 3. Moreover, the solid line thick line shown by "Example 2 * 2.5" has shown the viscosity upper limit, and the broken line thick line shown by "Example 1 * 0.4" has shown the viscosity minimum.

The upper limit of TI, which is the upper limit value of the thixotropy index TI, can be defined by the shear rate D = 1 (1 / s) in a straight line due to the upper limit of viscosity and the shear rate D = 100 (1 / s) in a straight line due to the lower limit of viscosity.
Further, the lower limit of the TI, which is the lower limit value of the thixotropy index TI, is determined by the shear rate D = 0.1 (1 / s) in the straight line due to the lower viscosity limit and the shear rate D = 100 (1 / s) in the straight line due to the upper limit of viscosity. Can be defined.
As indicated by the slope of the straight line between the TI upper limit and the TI lower limit, the thixotropy index TI of the viscous fluid 2 is 0.5 to 1.3.

  As described above, when the thixotropic index TI representing the high thixotropic property of the viscous fluid 2 is 0.5 to 1.3, it is most suitable as a crack detection viscous fluid for detecting the crack 3.

The apparent viscosity η _G of the viscous fluid 2 is 76 (Pa · s) or more when the shear rate D is 0.1 (1 / s) or less, and 11 when the shear rate D is 1 (1 / s). By setting it to -120 (Pa * s), the high viscosity in the location without the crack 3 is realizable, and a shape can be hold | maintained, without producing sagging.
The apparent viscosity η _G of the viscous fluid 2 is 1.7 to 16 (Pa · s) when the shear rate D is 10 (1 / s), and is 0 when the shear rate D is 100 (1 / s). .27-2 (Pa · s) reduces the viscosity in the vicinity of or inside the crack 3, enhances the fluidity of the viscous fluid, and makes it easier to enter the crack 3. The crack 3 can be visually detected by the dent 5 formed on the surface and / or the ground surface 6 of the base material 1 exposed by the dent 5.

  FIG. 11 is a view showing a notched flat plate test piece used in the crack growth test. As the base material (test piece) 1, a JIS SM490A steel plate test piece having a thickness of 5 mm and a notch having a length of 10 mm and a width of 0.3 mm was used.

As the next step, the predicted portion of the test piece 1 where the occurrence of the crack 3 is predicted is specified.
Here, the both side parts of the notch end of the center part of the test piece 1 were specified as a predicted part.

As the next step, the viscous fluid 2 is applied to the predicted portion of the specified test piece 1.
In Examples 1 to 3, the viscous fluid 2 shown in FIG. 2 was applied to the test piece 1 shown in FIG. 11 and tested. The viscous fluid 2 was applied to the test piece 1 using a plastic plate simple applicator so that the thickness of the viscous fluid 2 was about 0.7 mm.

As a next step, a load is repeatedly applied to the test piece 1 to which the viscous fluid 2 is applied.
As a tester, an electro-hydraulic servo type fatigue tester (manufactured by Shimadzu Corporation, dynamic capacity: 10 tonf) was used, and Comparative Example 1 (Comparative Test), Test 1 using Viscous Fluid 2 of Example 1, Example 2 Test 2 using the viscous fluid 2 and Tests 3 to 5 using the viscous fluid 2 of Example 3 were performed. Test conditions are: nominal stress range Δσ _n = 104 MPa, stress ratio R = 0 (complete swing), load frequency f (f = 4.2 Hz in Comparative Example 1 and Tests 1-3, f = 10.3 Hz in Test 4) In Test 5, f = 20.6 Hz). In tests 1 to 5, the viscous fluid 2 was applied to a vertical surface, and the presence or absence of sagging was also examined.

As the next step, the occurrence of the crack 3 is visually detected from the dent 5 on the outer surface of the viscous fluid 2 and / or the ground 6 of the test piece 1 exposed by the dent 5 at the predicted site.
FIG. 12 is a table showing test results for Comparative Example 1 and Tests 1-5. In Comparative Example 1, the test was performed without applying the viscous fluid 2 but with the metal substrate.
13 is a photograph showing the state during the crack propagation test in Comparative Example 1, FIG. 14 is a photograph showing the change of the viscous fluid during the crack propagation test in Test 1, and FIG. FIG. 16 is a photograph showing the relationship between the dent length and the actual crack length, FIG. 16 is a photograph showing the change of the viscous fluid during the crack growth test in Test 2, and FIG. 17 is the dent length of the viscous fluid and the actual crack length from the test results in Test 2. FIG. 18 is a photograph showing changes in viscous fluid during the crack growth test in Test 3, and FIG. 19 is a diagram showing the relationship between the dent length of the viscous fluid and the actual crack length from the test results in Test 3. 20 is a photograph showing changes in the viscous fluid during the crack growth test in Test 4, FIG. 21 is a diagram showing the relationship between the dent length of the viscous fluid and the actual crack length based on the test results in Test 4, and FIG. Of viscous fluid during crack growth test Photographs showing, FIG. 23 is a diagram showing a relationship between the recess length and the actual crack length of the viscous fluid from the test results of Test 5.

  In Comparative Example 1, FIG. 13 is a photograph of a state in which a crack 3 of about 10 mm has developed on both sides of the notch at a load repetition number N = 480,000, but the crack 3 is hardly visible. Thus, in the comparative example 1, even if the crack 3 progressed to some extent, it was difficult to detect it visually.

In Test 1 using the viscous fluid 2 of Example 1 (low viscosity), FIG. 14A shows the load repetition number N = 192,000, FIG. 14B shows the load repetition number N = 480,000, and FIG. 14C shows the load repetition. Number N = 576000 times, (e) is a photograph of the state at load repetition number N = 648,000 times, (d) is a partially enlarged photograph of (c), and (f) is a partially enlarged photograph of (e). It is a photograph.
In FIG. 15, circles indicate the relationship between the length of the recess 5 on the left side of the notch and the actual crack length, and squares indicate the relationship between the length of the recess 5 on the right side of the notch and the actual crack length.
From FIG. 14 and FIG. 15, it can be seen that a clear dent 5 is observed on the surface of the viscous fluid according to the progress of the crack 3, and the followability of the viscous fluid 2 is good.
FIGS. 14D and 14F are photographs taken with illumination near the crack on the left side, and the background 6 of the base material 1 is visible behind the recess 5. By illuminating in this way, the depression 5 of the viscous fluid 2 and the background 6 of the base material 1 can be easily detected. Furthermore, by adjusting the type of illumination, the irradiation range, and the irradiation angle, it is possible to make it easier to detect.
A slight sagging was observed immediately after application at the end of the viscous fluid applied to the portion without the crack 3 (sound part), but no sagging occurred during the test.

In Test 2 using the viscous fluid 2 of Example 2 (medium viscosity), FIG. 16A shows the number of load repetitions N = 215,000, FIG. 16B shows the number of load repetitions N = 480000, and FIG. Number N = 624,000 times, (f) is a photograph of the state at load repetition number N = 648,000 times, (c) is a partially enlarged photograph of (b), and (e) is a partially enlarged view of (d). It is a photograph.
In FIG. 17, circles indicate the relationship between the length of the recess 5 on the left side of the notch and the actual crack length, and squares indicate the relationship between the length of the recess 5 on the right side of the notch and the actual crack length.
From FIG. 16 and FIG. 17, it can be seen that a clear dent 5 is observed on the surface of the viscous fluid according to the progress of the crack 3, and the followability of the viscous fluid 2 is good.
FIG. 16C is a photograph taken with illumination in the vicinity of the center, and the background 6 of the base material 1 is visible behind the recess 5. FIG. 16 (e) is a photograph taken with illumination near the crack on the left side, and the background 6 of the base material 1 is visible behind the recess 5. By illuminating in this way, the depression 5 of the viscous fluid 2 and the background 6 of the base material 1 can be easily detected. Furthermore, by adjusting the type of illumination, the irradiation range, and the irradiation angle, it is possible to make it easier to detect.
There was no dripping of the viscous fluid 2 applied to the healthy part.

In test 3 (load frequency f = 4.2 Hz) using the viscous fluid 2 of Example 3 (high viscosity), FIG. 18A shows the load repetition number N = 624000 times, and FIG. 18C shows the load repetition number N = It is the photograph which image | photographed the state in 654000 times, (b) is the partially expanded photograph of (a), (d) is the partially expanded photograph of (c).
In FIG. 19, circles indicate the relationship between the length of the recess 5 on the left side of the notch and the actual crack length, and squares indicate the relationship between the length of the recess 5 on the right side of the notch and the actual crack length.
18 and 19, it can be seen that the dent 5 was observed on the viscous fluid surface after the actual crack length was close to 10 mm, but the followability to the crack 3 was not necessarily sufficient. The maximum value of the error between the length of the recess 5 of the viscous fluid 2 and the actual crack length was 10.25 mm.
FIG. 18B is a photograph taken with illumination in the vicinity of the center. FIG. 18D is a photograph taken with illumination in the vicinity of the crack 3 on the right side, and the background 6 of the base material 1 is visible behind the recess 5. By illuminating in this way, the depression 5 of the viscous fluid 2 and the background 6 of the base material 1 can be easily detected, and by adjusting the type of illumination, the irradiation range, and the irradiation angle, the state can be further easily detected. be able to.
There was no dripping of the viscous fluid 2 applied to the healthy part.

In Test 4 (load frequency f = 10.3 Hz) using the viscous fluid 2 of Example 3 (high viscosity), FIG. 20A is a photograph of a state taken at a load repetition number N = 660000 times. b) is a partially enlarged photograph of (a).
In FIG. 21, the circles indicate the relationship between the length of the recess 5 on the left side of the notch and the actual crack length, and the squares indicate the relationship between the length of the recess 5 on the right side of the notch and the actual crack length.
20 and 21, a dent 5 is observed on the surface of the viscous fluid even in the initial stage where the actual crack length is 5 mm or less, and the followability to the crack 3 is significantly larger than that in the test 3 (load frequency f = 4.2 Hz). It can be seen that there is an improvement. The maximum error between the length of the recess 5 of the viscous fluid 2 and the actual crack length was 6.04 mm.
FIG. 20B is a photograph taken with illumination in the vicinity of the crack 3 on the left side, and the background 6 of the base material 1 is visible behind the recess 5. By illuminating in this way, the depression 5 of the viscous fluid 2 and the background 6 of the base material 1 can be easily detected, and by adjusting the type of illumination, the irradiation range, and the irradiation angle, the state can be further easily detected. be able to.
There was no dripping of the viscous fluid 2 applied to the healthy part.

In Test 5 using the viscous fluid 2 of Example 3 (high viscosity) (load frequency f = 20.6 Hz), FIG. 22A is a photograph of a state taken at a load repetition number N = 708000 times. b) is a partially enlarged photograph of (a).
In FIG. 23, circles indicate the relationship between the length of the recess 5 on the left side of the notch and the actual crack length, and squares indicate the relationship between the length of the recess 5 on the right side of the notch and the actual crack length.
From FIG. 22 and FIG. 23, the dent 5 is observed on the viscous fluid surface even in the initial stage where the actual crack length is 5 mm or less, and the followability to the crack 3 is significantly larger than that of the test 3 (load frequency f = 4.2 Hz). It can be seen that there is an improvement. The maximum value of the error between the length of the recess 5 of the viscous fluid 2 and the actual crack length was 4.29 mm.
FIG. 22B is a photograph taken with illumination in the vicinity of the crack 3 on the left side, and the ground surface 6 of the base material 1 is visible behind the recess 5. By illuminating in this way, the depression 5 of the viscous fluid 2 and the background 6 of the base material 1 can be easily detected, and by adjusting the type of illumination, the irradiation range, and the irradiation angle, the state can be further easily detected. be able to.
There was no dripping of the viscous fluid 2 applied to the healthy part.

From the results of Tests 3 to 5, when the relative viscosity of the viscous fluid 2 to be applied is large as in Example 3, repeated load applied to the base material 1 as in Test 3 (load frequency f = 4.2 Hz). Although the crack detection effect due to the dent 5 of the viscous fluid 2 cannot be expected when the frequency of the fluid is low, the load frequency is low as in test 4 (load frequency f = 10.3 Hz) or test 5 (load frequency f = 20.6 Hz). When it is high, it can be seen that the shear rate of the viscous fluid 2 near or inside the crack 3 increases and the apparent viscosity decreases, and the crack detection effect by the dent 5 of the viscous fluid 2 is greatly improved.
Therefore, when selecting the relative viscosity of the viscous fluid 2 having a high thixotropic property used for detecting the crack 3, the frequency of the main repeated load applied to the base material 1 depends on the shear rate and the apparent viscosity of the viscous fluid 2. It is desirable to consider the effect on viscosity.
That is, the influence of the frequency of the repeated load applied to the base material 1 on the shear rate and the apparent viscosity of the viscous fluid 2 is considered based on the known high thixotropic viscosity characteristics of the viscous fluid 2, and the relative viscosity of the viscous fluid 2 By appropriately increasing or decreasing the appropriate viscosity according to the frequency of the repeated load applied to the base material 1, the viscous fluid 2 that detects the occurrence of the crack 3 in the base material 1 can be selected more appropriately without causing sagging. .
Moreover, the frequency of the repeated load applied to the base material 1 is measured or predicted, and when the measured value or the predicted value is equal to or greater than a predetermined value, the relatively high viscosity viscous fluid 2 is selected, and the measured value or the predicted value is If it is less than the predetermined value, a relatively low or medium viscosity fluid 2 may be selected.

Steps for preparing a viscous fluid 2 having a high thixotropic property and a base material (test piece) 1 as in Tests 1 to 5, and a step for specifying a predicted portion of the base material 1 where the occurrence of a crack 3 is predicted A step of applying the viscous fluid 2 to the predicted portion of the identified base material 1, a step of repeatedly applying a load to the base material 1 to which the viscous fluid 2 is applied, and a dent on the outer surface of the viscous fluid 2 at the predicted portion. 5 and / or the step of visually detecting the occurrence of the crack 3 from the ground surface 6 of the base material 1 exposed by the dent 5, so that the viscous fluid 2 is applied to a site where the occurrence of the crack 3 is predicted in advance. The viscous fluid 2 having a high thixotropic property applied to the predicted portion of the base material 1 that has been identified can retain its shape on the surface of the base material 1 without causing a sagging due to a high viscosity at a location where there is no crack 3. , Repetitive In the vicinity of the crack 3 that opens and closes due to the action of the load, the shear rate of the viscous fluid 2 increases and the viscosity decreases, so that the fluidity increases. Due to the pumping action and capillary action of the crack 3, the viscous fluid 4 near the crack 3 In combination with being sucked into the crack 3, a remarkable dent 5 is formed in the viscous fluid 4 near the crack 3, so that the dent 5 or the ground surface 6 of the base material 1 exposed by the dent 5 is observed. Thus, the location where the crack 3 in the base material 1 is generated can be easily detected visually.
Further, the viscous fluid 2 does not need to be subjected to special pre-coating ground treatment such as blasting, degreasing, and chemical conversion treatment like a paint. Therefore, in executing the step of applying the viscous fluid 2 to the predicted portion of the identified base material 1, the pre-painting base treatment is not performed on the base material 1 before the viscous fluid 2 is applied, and the working time is shortened. Can do.
Further, the viscous fluid 2 can be overcoated on the existing coating film of the base material 1. Therefore, even if the base material 1 is coated, in the step of applying the viscous fluid 2 to the predicted portion of the specified base material 1, the viscous fluid 2 is applied to the base material 1 over the applied coating film. The work which peels off the existing coating film of the base material 1 is unnecessary, and working time can be shortened.
In addition, when executing the step of applying the viscous fluid 2 to the predicted portion of the specified base material 1, the viscous fluid is applied to the base material 1 before the viscous fluid 2 is applied or to the coating film already applied to the base material 1. You may color the color different from 2 colors. In this case, due to the contrast between the color of the viscous fluid 2 and the background 6 of the base material 1 or the colored color of the coating film, the base material is located behind the dent 5 formed in the viscous fluid 2 by the development of the crack 3 of the base material 1. The visibility when 1 background 6 or a coating film is seen improves. In addition, it is preferable to color the base material 1 or the coating film already applied to the base material 1 with a color that contrasts with the color of the viscous fluid 2 with a red paint or the like, and may be simply performed with a felt pen or the like. .
Moreover, after detecting generation | occurrence | production of the crack 3 by the step which detects generation | occurrence | production of the crack 3 visually, the step which removes the apply | coated viscous fluid 2 can be further provided. The highly thixotropic viscous fluid 2 applied to the base material 1 can be removed simply by wiping with a cloth, etc., unlike a paint which requires a considerable amount of time and labor to remove because a firm coating film is formed. can do.
In addition, in selecting the viscous fluid 2 in the step of preparing the viscous fluid 2 and the base material 1 having high thixotropic properties, the frequency of the repeated load applied to the base material 1 depends on the shear rate and the apparent viscosity of the viscous fluid 2. Considering the influence exerted on the basis of the known high thixotropic viscosity characteristics of the viscous fluid 2, when the relative viscosity of the viscous fluid 2 is appropriately increased or decreased according to the frequency of the repeated load applied to the base material 1, The viscous fluid 2 for detecting the occurrence of the crack 3 in the base material 1 without causing sagging can be selected more appropriately.
Further, the frequency of a repeated load applied to the base material 1 is measured or predicted. If the measured value or the predicted value is equal to or greater than a predetermined value, a relatively high viscosity viscous fluid 2 is selected, and the measured value or predicted value is If it is less than the predetermined value, a relatively low or medium viscosity fluid 2 may be selected.

In this embodiment, silicone grease is used as the viscous fluid 2. However, the viscous fluid 2 may be a paste having high thixotropic properties. In this case, the paste having high thixotropic properties is cracked 3. It can be used for detection.
The viscous fluid 2 may be a mixture of a fluid and powder (particles having a higher hardness and a higher elastic modulus than the base material 1, such as a metal oxide such as alumina), and in that case, a high thixotropic property. A mixture of fluid and powder (particles) having the above can be used to detect the crack 3. In this case, when the powder (particles) entering the crack 3 together with the viscous fluid 2 has a predetermined hardness and toughness, the base material 1 scraped by the powder (particles) accompanying opening and closing of the crack 3 It can be expected that the detection of the crack 3 is promoted by the discoloration of the structure (black) and the effect of suppressing the progress of the crack 3 because the powder is sandwiched between the cracks 3.
Further, the dent 5 generated on the outer surface of the paste with the progress of the crack 3 varies depending on the degree of the effect of suppressing the progress of the crack 3 of the powder. When the progress suppressing effect is effective, the amount of the base material powder generated by scraping the base material 1 with the opening of the crack 3 in the powder entering the crack 3 increases, and the outer surface of the paste becomes convex black. Sometimes it comes up.
The material of the base material 1 can mainly be a metal material, but may be a material other than a metal material such as ceramics, resin, or fiber reinforced resin.
Moreover, as powder (particles), other than alumina, silica, silicon nitride, silicon carbide, zirconia, zirconium carbide, boron carbide, boron nitride, titanium carbide, tungsten carbide, cemented carbide, white metal elements (ruthenium, rhodium) , Palladium, osmium, iridium, platinum), iron, steel, aluminum, aluminum alloy, aluminum nitride, yttria, magnesium, magnesium alloy, titanium, titanium alloy, titanium oxide, copper, copper alloy, diamond, carbon, and carbon fiber It is preferable to include one or more kinds, and the powder (particles) is a powder (particles) including particles having a particle size larger than the opening size of the target crack 3 and passes through a sieve having a mesh size of 20 μm. It is preferable to use a diameter.
When the conditions of the paste that exhibits the effect of suppressing the progress of the crack 3 are arranged, the paste has a high thixotropic property in which the powder (particles) having a hardness higher than the hardness of the base material 1 and the viscous fluid 2 are mixed. Or a paste having a high thixotropic property in which powder (particles) having a rigidity higher than that of the base material 1 and the viscous fluid 2 are mixed.
According to the paste that suppresses the progress of the cracks 3, the progress suppressive paste has a high thixotropic property in which powder (particles) having a hardness equal to or higher than the hardness of the base material 1 and the viscous fluid 2 are mixed. Has a high viscosity at a location where there is no crack 3 and maintains the shape and homogeneity on the surface of the base material 1 without causing sagging, and when the crack 3 is generated and the opening and closing is started, the shear rate near the crack is increased. At the location, the viscosity decreases and the fluidity increases, so that the powder (particles) can easily enter the crack 3, and the progress of the crack 3 can be suppressed by the wedge effect of the powder (particles) that has entered the crack 3. Further, in the case of a progress suppressing paste having a high thixotropic property in which powder (particles) having a rigidity equal to or higher than the rigidity of the base material 1 and the viscous fluid 2 are mixed, the mother of the crack 3 surface to be further closed is used. The development of the crack 3 can be suppressed by the wedge effect of the powder (particle) that has entered the crack 3 without the powder (particle) being crushed and deformed due to the rigidity of the material 1.
In selecting a paste in which powder (particles) exhibiting the effect of suppressing the progress of the crack 3 and the viscous fluid 2 are selected, the frequency of the repeated load applied to the base material 1 depends on the shear rate of the paste and It can also be selected in consideration of the influence on the apparent viscosity.
The relationship between the thixotropy index TI, the apparent viscosity η _G and the shear rate D representing the high thixotropic property of the paste exhibiting the effect of suppressing the growth of the crack 3 is slightly different from the above-mentioned numerical values.
In this case, the thixotropy index TI is preferably 0.3 to 1.6.
The apparent viscosity η _{G of the} paste is 88 (Pa · s) or more when the shear rate D is 0.1 (1 / s), and 13 to 490 (when the shear rate D is 1 (1 / s). Pa · s).
The apparent viscosity η _G is 2.1 to 76 (Pa · s) when the shear rate D is 10 (1 / s), and 0.33 to 12 when the shear rate D is 100 (1 / s). (Pa · s) is preferable.

In the present embodiment, the base material 1 in which the occurrence of the crack 3 is predicted is prepared, but the base material 1 in which the crack 3 has occurred can also be used. That is, a step of preparing a viscous fluid 2 having a high thixotropic property and a base material (test piece) 1 in which a crack 3 is generated, and a crack part of the crack 3 and / or a progress prediction part of the crack 3 of the base material 1 are provided. The step of applying the viscous fluid 2, the step of repeatedly applying a load to the base material 1 to which the viscous fluid 2 is applied, and the recesses 5 and / or the background of the base material 1 exposed by the recesses 5 of the viscous fluid 4. 6 to visually detect the progress of the crack 3, the viscous fluid 2 having a high thixotropic property applied to the crack 3 of the base material 1 has a high viscosity in a place where there is no crack 3. In the vicinity of the crack 3 that maintains its shape on the surface of the base material 1 without being generated and opens and closes due to the action of repeated loads, the shear rate of the viscous fluid 2 increases and the viscosity decreases, so that the fluidity increases, and the crack 3 Pump In addition, the viscous fluid 4 near the crack 3 is sucked into the crack 3 due to the capillary phenomenon, so that a significant recess 5 is formed in the viscous fluid 4 near the crack 3. By observing the ground surface 6 of the exposed base material 1, the progress of the crack 3 in the base material 1 can be easily detected visually.
Further, the viscous fluid 2 does not need to be subjected to a special pre-painting base treatment like a paint. Therefore, in performing the step of applying the viscous fluid 2 to the progress prediction portion of the crack 3 of the base material 1, the pre-painting base treatment is not performed on the base material 1 before the viscous fluid 2 is applied, and the working time is shortened. can do.
Further, the viscous fluid 2 can be overcoated on the existing coating film of the base material 1. Therefore, even if the base material 1 is coated, the viscous fluid 2 is applied to the base material 1 in the step of applying the viscous fluid 2 to the cracked portion of the crack 3 and / or the progress predicted portion of the crack 3 of the base material 1. It can be applied over the already-coated film, and the work of peeling off the existing coating film of the base material 1 is not necessary, and the working time can be shortened.
Further, when executing the step of applying the viscous fluid 2 to the crack portion of the crack 1 and / or the predicted portion of the crack 3 of the base material 1, the base material 1 or the base material 1 before the viscous fluid 2 is applied is applied. The applied coating film may be colored with a color different from that of the viscous fluid 2. In this case, due to the contrast between the color of the viscous fluid 2 and the background 6 of the base material 1 or the colored color of the coating film, the base material is located behind the dent 5 formed in the viscous fluid 2 by the development of the crack 3 of the base material 1. The visibility when 1 background 6 or a coating film is seen improves. In addition, it is preferable to color the base material 1 or the coating film already applied to the base material 1 with a color that contrasts with the color of the viscous fluid 2 with a red paint or the like, and may be simply performed with a felt pen or the like. .
Moreover, after detecting the progress of the crack 3 in the step of visually detecting the progress of the crack 3, a step of removing the applied viscous fluid 2 can be further provided. The highly thixotropic viscous fluid 2 applied to the base material 1 can be removed simply by wiping with a cloth, etc., unlike a paint which requires a considerable amount of time and labor to remove because a firm coating film is formed. can do.
In addition, in selecting the viscous fluid 2 in the step of preparing the viscous fluid 2 having high thixotropic properties and the base material 1 in which the crack 3 is generated, the frequency of the repetitive load applied to the base material 1 is the shear of the viscous fluid 2. The effect on speed and apparent viscosity is considered based on the known high thixotropic viscosity characteristics of viscous fluid 2, and the relative viscosity of viscous fluid 2 is appropriately increased or decreased according to the frequency of repeated loads applied to the base material 1. In this case, the viscous fluid 2 that detects the progress of the crack 3 in the base material 1 without causing sagging can be selected more appropriately.
The
Further, the frequency of a repeated load applied to the base material 1 is measured or predicted. If the measured value or the predicted value is equal to or greater than a predetermined value, a relatively high viscosity viscous fluid 2 is selected, and the measured value or predicted value is If it is less than the predetermined value, a relatively low or medium viscosity fluid 2 may be selected.

In this embodiment, a metal is used for the base material (test piece) 1, but even if it is not a fatigue crack generated in the metal, it can be detected if the crack 3 opens and closes. Therefore, the base material 1 is made of plastic, composite material (FRP). Etc.), concrete, wood, ceramics, and the like, and not only metal, but also a base material 1 in which a crack 3 may occur or develop due to repeated load can be an inspection object. That is, fatigue cracks (metal, plastic, composite material, ceramics, etc.) that open and close by repeated loads and cracks (metal, plastic, concrete, wood, ceramics, etc.) that open and close by repeated loads can be applied to the present invention.
In addition, the application of the viscous fluid 2 is a predicted portion where the crack 3 of the base material 1 is predicted to be generated and the vicinity thereof, and a crack portion of the crack 3 of the base material 1 and the periphery thereof and / or a predicted portion of progress of the crack 3. Further, it can be applied widely around the periphery.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a portion where a crack is likely to occur or develop in a structure such as a ship, an offshore structure, a bridge, a vehicle, a machine tool, or a building.

DESCRIPTION OF SYMBOLS 1 Base material 2 Viscous fluid 3 Crack 4 Viscous fluid of medium and low viscosity 5 Recess 6 Ground

Claims (23)

  An outer surface of the viscous fluid formed by applying a viscous fluid having a high thixotropic property to a base material to which a load is repeatedly applied, and the viscous fluid is sucked into the crack by opening and closing the crack of the base material. A method for detecting cracks with a viscous fluid, comprising detecting the occurrence or development of the cracks from a dent and / or a ground surface of the base material exposed by the dents.   Step 1 for preparing the viscous fluid having high thixotropic properties and the base material, Step 2 for specifying a predicted portion of the base material where occurrence of the crack is predicted, and the prediction of the specified base material Step 3 of applying the viscous fluid to a site, Step 4 of repeatedly applying a load to the base material to which the viscous fluid has been applied, and a depression and / or a depression of the outer surface of the viscous fluid at the predicted site. The method for detecting a crack by a viscous fluid according to claim 1, further comprising: a step 5 of visually detecting the occurrence of the crack from the ground surface of the exposed base material.   3. The method for detecting cracks due to a viscous fluid according to claim 2, wherein when performing the step 3, the base material before coating is not applied to the base material before the viscous fluid is applied.   The method for detecting cracks caused by a viscous fluid according to claim 2 or 3, wherein, in the step 3, the viscous fluid is applied on the base material in a layered manner on a coated film.   In performing the step 3, the base material before the viscous fluid is applied or a coating film already applied to the base material is colored with a color different from the color of the viscous fluid. The method for detecting a crack by a viscous fluid according to any one of claims 2 to 4.   The viscosity according to claim 2, further comprising a step 6 of removing the applied viscous fluid after detecting the occurrence of the crack in the step 5. A method for detecting cracks caused by fluid.   3. The selection of the viscous fluid in the step 1 is performed by considering the influence of the frequency of the repeated load applied to the base material on the shear rate and the apparent viscosity of the viscous fluid. The detection method of the crack by the viscous fluid of any one of Claim 6 from.   Step 7 of preparing the viscous fluid having high thixotropic properties and the base material in which the crack has occurred, and applying the viscous fluid to a crack portion of the crack and / or a predicted progress portion of the crack of the base material Step 9 in which the load is repeatedly applied to the base material to which the viscous fluid is applied, and the cracks from the ground of the base material exposed by the dents and / or dents in the outer surface of the viscous fluid. The method for detecting cracks with viscous fluid according to claim 1, further comprising: a step 10 for visually detecting the progress of the fluid.   9. The method for detecting cracks due to a viscous fluid according to claim 8, wherein when performing the step 8, pre-coating ground treatment is not performed on the base material before the viscous fluid is applied.   The method for detecting cracks due to a viscous fluid according to claim 8 or 9, wherein, in the step 8, the viscous fluid is applied on the base material so as to overlap the applied coating.   In performing the step 8, the base material before the viscous fluid is applied or a coating film already applied to the base material is colored with a color different from the color of the viscous fluid. The method for detecting a crack by a viscous fluid according to any one of claims 8 to 10.   The viscosity according to claim 8, further comprising a step 11 of removing the applied viscous fluid after detecting the progress of the crack in the step 10. A method for detecting cracks caused by fluid.   9. In selecting the viscous fluid in the step 7, the frequency is selected in consideration of the influence of the frequency of the repeated load applied to the base material on the shear rate and the apparent viscosity of the viscous fluid. The detection method of the crack by the viscous fluid of any one of Claim 12.   The thixotropic index TI representing the high thixotropic property of the viscous fluid is 0.3 to 1.7, and the crack caused by the viscous fluid according to any one of claims 1 to 13 is provided. Detection method. The apparent viscosity η _G of the viscous fluid is 31 (Pa · s) or more when the shear rate D is 0.1 (1 / s), and from 4.8 to when the shear rate D is 1 (1 / s). The method for detecting a crack by a viscous fluid according to any one of claims 1 to 14, wherein 280 (Pa · s) is set. The apparent viscosity η _G of the viscous fluid is 0.7 to 37 (Pa · s) when the shear rate D is 10 (1 / s), and 0.11 when the shear rate D is 100 (1 / s). The method for detecting a crack by a viscous fluid according to any one of claims 1 to 15, wherein the crack is detected to be -4.9 (Pa · s).   The detection of a crack by a viscous fluid according to any one of claims 1 to 16, wherein the base material is selected from metal, plastic, composite material, concrete, wood, and ceramics. Method.   A viscous fluid for crack detection used in the method for detecting a crack by a viscous fluid according to any one of claims 1 to 17.   The viscous fluid for crack detection according to claim 18, wherein the viscous fluid is a paste having high thixotropic properties.   The viscous fluid for crack detection according to claim 18 or 19, wherein the viscous fluid is a mixture of a fluid and a powder.   The viscous fluid for crack detection according to any one of claims 18 to 20, wherein the viscous fluid is a silicone-based viscous fluid.   The viscous fluid for crack detection according to any one of claims 18 to 21, wherein the viscous fluid is a pale viscous fluid including white. 23. The viscous fluid according to any one of claims 18 to 22, wherein the viscous fluid is a viscous fluid having a viscosity characteristic selected in consideration of a frequency of the repeated load applied to the assumed base material. Viscous fluid for crack detection.