Hydrophobic gel-like elastic coupler for ultrasonic flaw detection equipment and ultrasonic flaw detection equipment including the same

Abstract

To provide a hydrophobic gel elastic body coupler for a supersonic flaw detection device, which does not swell, has sufficient flexibility, and has low supersonic attenuation.SOLUTION: A hydrophobic gel elastic body coupler for a supersonic flaw detection device comprises: a pair of facing ribs 110; and a tire drum 120 provided between the ribs 110, the tire drum 120 using a hydrophobic gel elastic body as a material. As a blended component of the tire drum 120, 30 to 80 wt% of a plasticizer is blended in gel generation, with respect to polyurethane polyisocyanate prepolymer including polyurethane polyol component and polyisocyanate component. The hydrophobic gel elastic body coupler 100 is mounted on the supersonic flaw detection device which performs scanning by using the supersonic received and transmitted by a supersonic probe while bringing the coupler into contact with a flaw detection target. A supersonic scanning area 125 and a supersonic non-scanning area 126 may be provided on the tire drum 120.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an acoustic coupler interposed between a probe of an ultrasonic flaw detector and a flaw detection object. In particular, the present invention relates to an acoustic coupler used in a tire-type ultrasonic flaw detector that can rotate while abutting against a flaw detection object to perform continuous flaw detection inspection. Examples of the flaw detection object include steel structures, metal welded portions, plastic structures, concrete structures, glass structures, and ceramic structures.

Background Art

[0002] As a flaw detection inspection method for checking whether there are surface flaws or internal cracks in flaw detection objects such as steel structures, metal welded portions, plastic structures, concrete structures, glass structures, and ceramic structures, an ultrasonic flaw detector using an ultrasonic imaging means is known. Ultrasonic waves are introduced into the flaw detection object, and the ultrasonic waves reflected inside the flaw detection object are received to check the ultrasonic waveform, or the internal state of the flaw detection object is visualized as an image, thereby inspecting the presence of flaws and cracks in the flaw detection object. In this way, the ultrasonic flaw detector using the ultrasonic imaging means can visualize and inspect the inside of the flaw detection object.

[0003] As described above, ultrasonic flaw detectors for exploring flaws in flaw detection objects have been widely used in the prior art, and tire-type ultrasonic flaw detectors are known as devices for detecting flaws in flaw detection objects covering a wide and long flaw detection range, such as flaws in thin metal plates and rails. Figure 14 is a diagram showing the configuration of a conventional tire-type ultrasonic flaw detector. As shown in Figure 14, a conventional tire-type ultrasonic flaw detection device comprises a fixed central shaft 5 fixed to a frame 3, an ultrasonic wave transmitting and receiving means 7 mounted on the fixed central shaft 5, a tire that rotates relative to the fixed central shaft 5 and houses the ultrasonic wave transmitting and receiving means 7, and an ultrasonic propagation fluid 11 filled inside the tire 9. The tire 9 is driven to rotate using air pressure. The fixed central shaft 5 is designed not to rotate even when the tire 9 rotates, as will be described later. Conventionally, this type of tire-type ultrasonic flaw detection device performed flaw detection by bringing a tire 9 into contact with the object to be inspected, such as a thin plate, and rotating the tire 9 due to friction between the plate and the tire. Ultrasonic waves transmitted from an ultrasonic transmitter / receiver 7 housed inside the tire 9 are sent to the inside of the object to be inspected via an ultrasonic propagation fluid 11 and the tire 9, and the reflected ultrasonic waves are received. Flaw detection is performed to check for defects or other problems by detecting abnormalities in the reflected ultrasonic waves.

[0004] In conventional technology, if air is present between the transducer of an ultrasonic flaw detection device that generates ultrasonic waves and the object being inspected, the ultrasonic waves are reflected by the air surface and detected as noise. Therefore, conventional techniques have involved placing moisture and an acoustic coupler between the transducer of the ultrasonic flaw detection device and the object being inspected to remove the air.

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-267905 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0006] In conventional tire-type ultrasonic flaw detectors, the inside of the tire is filled with water, and measurements are taken with water actively interposed between the tire and the object being inspected. In conventional tire-type ultrasonic flaw detection devices, the tire portion, or acoustic coupler, was almost always made of rubber material such as silicone. Because rubber materials such as silicone have high attenuation and poor acoustic coupling with water, when using rubber materials such as silicone as the material for the acoustic coupler, a large amount of water was required between the tire and the object being inspected. Therefore, in order to reduce the amount of water used between the tire and the object being inspected, there are a small number of conventional technologies that employ hydrophilic urethane materials as the material for the acoustic coupler. However, this conventional hydrophilic elastic coupler had the following problems: Conventional hydrophilic gel-type acoustic couplers are hydrophilic, have good ultrasonic transmission, and are flexible, making them easy to handle. However, because water is interposed between the hydrophilic gel-type acoustic coupler and the object being inspected, prolonged use can cause the hydrophilic gel-type acoustic coupler to swell, altering its crucial ultrasonic properties and leading to problems such as cracking and wear.

[0007] Therefore, assuming that conventional hydrophobic materials are used as the material for the acoustic coupler, hydrophobic gel-like substances generally have a large attenuation of ultrasound, making them unsuitable for detecting defects in objects using hydrophobic gel-like acoustic couplers. Therefore, in conventional technology, there have been examples of using acoustic couplers made of hydrophilic materials that have low attenuation and high flexibility. However, as mentioned above, if acoustic couplers made of hydrophilic materials are used continuously, they swell, which changes the ultrasonic properties and causes problems such as tearing and wear due to use. Furthermore, even if a tire is manufactured using a rubber material such as silicone as a base and a hydrophilic urethane material is attached to its surface, such a structure is not suitable because the damping at the base portion is excessive.

[0008] Therefore, the inventors considered that by adopting a hydrophobic and low-attenuation segmented polyurethane gel as the tire material for a tire-type ultrasonic flaw detector, it would be possible to perform flaw detection inspections while reducing water usage. Furthermore, through repeated improvements to the composition of the hydrophobic gel material, they succeeded in developing a novel segmented polyurethane gel that is highly durable while maintaining flexibility and is ideal for tire probes. The present invention aims to provide a hydrophobic gel-like elastic coupler using a novel segmented polyurethane gel, which is optimal for tire probes used in ultrasonic flaw detection equipment. [Means for solving the problem]

[0009] To achieve the above objective, the hydrophobic gel-like elastic coupler of the present invention is an acoustic coupler used in the following tire-type ultrasonic flaw detection apparatus, which comprises a support part that rotatably supports the acoustic coupler around a rotation axis, an ultrasonic probe housed in the support part, and an ultrasonic propagation fluid filled in the acoustic coupler, and is a tire-type ultrasonic flaw detection apparatus that rotates and moves the acoustic coupler while bringing the probe surface in contact with the object to be inspected, and performs ultrasonic flaw detection on the object to be inspected by ultrasonic waves transmitted and received by the ultrasonic probe. The structure of the acoustic coupler of the present invention comprises a pair of opposing ribs and a cylindrical or spindle-shaped tire drum provided between the pair of ribs, and is characterized in that the tire drum of the above configuration is made of a hydrophobic gel-like elastic material. With the above configuration, the tire drum is made of a hydrophobic gel-like elastic material, and even if water is interposed between the gel-like elastic coupler and the object to be inspected for a long period of time, it will not swell, and excellent ultrasonic properties can be maintained in a stable state.

[0010] Here, even if the tire drum is made of a hydrophobic gel-like elastic material, a plasticizer can be added to the compound of the tire drum to suppress ultrasonic attenuation and to allow it to easily deform along the uneven surface of the object to be inspected. For example, propylene carbonate, ethylene carbonate, N-methyl-2-pyrrolidone, diisononylcyclohexane 1,2-dicarboxylate, or glycol ethers can be used as plasticizers. In order to obtain sufficient flexibility, it is preferable to use a plasticizer blending amount of 30-80 wt% or 50-80 wt%. Thus, by adding a large amount of plasticizer during gel formation for tire drum manufacturing, the wall surface of the tire drum becomes softer, and when it comes into contact with the surface of the object to be inspected, the hydrophobic gel-like elastic coupler of the present invention can follow the irregularities on the surface of the object to be inspected with good performance.

[0011] While a higher proportion of plasticizer increases the flexibility of the tire drum wall, allowing it to conform to minute irregularities on the surface of the object being inspected, uniformly increasing the plasticizer content throughout the entire tire drum to form a gel can increase the overall flexibility of the drum, potentially creating disadvantages. The disadvantage is that if the entire tire drum becomes considerably soft, it becomes difficult to apply to tire-type ultrasonic flaw detection devices. In other words, the hydrophobic gel-like elastic coupler of the present invention requires a certain degree of mechanical structural strength and rigidity for use in tire-type ultrasonic flaw detection devices. This is because structural strength and rigidity of the entire tire drum are necessary to ensure the strength to attach to the ribs of the tire drum, to suppress fluctuations in the diameter of the cylindrical tire drum even when pressed against the object to be inspected as a tire, and to maintain the water retention and leakage prevention properties of the medium such as water filled inside the tire drum.

[0012] In order to achieve both advantages and disadvantages, the inventors conceived of creating a so-called "hybrid" tire drum with different hardness levels depending on the region of the tire drum, by adjusting the amount of OH / NCO incorporated in areas where high flexibility is required and the amount of OH / NCO incorporated in other areas. The "hybrid" tire drum conceived by the inventors is characterized by having an "ultrasonic scanning area" that includes the region through which ultrasonic waves emitted by an ultrasonic probe pass and are reflected from the flaw detection point of the object being inspected, and an "ultrasonic non-scanning area" other than the area where the ultrasonic waves pass. The OH / NCO ratio is adjusted to be large in the part of the tire drum that forms the "ultrasonic scanning area" and small in the "ultrasonic non-scanning area," so that the flexibility of the "ultrasonic scanning area" is adjusted to be larger than the flexibility of the "ultrasonic non-scanning area." With the above configuration, the "ultrasonic scanning area" is sufficiently flexible to follow even minute irregularities on the surface of the object to be inspected, while the "non-ultrasonic scanning area" has a certain degree of mechanical structural strength and rigidity, resulting in a hydrophobic gel-like elastic coupler suitable for tire-type ultrasonic flaw detection equipment.

[0013] Next, we will describe the individual components required to obtain a hydrophobic gel-like elastic coupler. The hydrophobic gel-like elastic material is a polyurethane resin composition using a polyurethane polyisocyanate prepolymer having a polyurethane polyol component and a polyisocyanate component. First, the ratio of hydrophobic alkylene oxide chains to hydrophilic alkylene oxide chains in the polyurethane polyol component is adjusted to a value between 100:0 and 70:30. The active ingredient is a hydrophobic alkylene oxide chain contained in the polyisocyanate component. For example, it is preferable to use any of the following or derivatives: hexamethylene diisocyanate, 4,4-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, naphthalene 1,5-diisocyanate, or xylylene diisocyanate. Furthermore, alicyclic isocyanate species can also be used as polyisocyanates. For example, alicyclic isocyanate species such as isophorone diisocyanate (IPDI), 4,4-methylenebis(cyclohexyl isocyanate) (hydrogenated MDI: H12MDI), and bis(isocyanatomethyl)cyclohexane (hydrogenated XDI: H6XDI) can be used. With the above components, the polyurethane resin composition can be formed from a hydrophobic polyurethane polyol component and a hydrophobic polyisocyanate component, resulting in a hydrophobic gel-like elastic coupler.

[0014] Furthermore, in the above components, the polyurethane polyol component is a component that includes either or both of the following: a polyol with 2 functional groups and a number average molecular weight of 1,000 to 6,000, or a polyol with 3 functional groups and a number average molecular weight of 3,500 to 5,000. The combination of the number of functional groups of the polyurethane polyol component and the number of functional groups of the polyurethane polyisocyanate prepolymer is 2 and 3, 3 and 2, or 3 and 3, and is not a combination of 2 and 3. The number of functional groups in the polyol and polyisocyanate components forms a three-dimensional network structure of urethane bonds. By adjusting the balance between the number of two- and three-functional groups, the elasticity of the urethane resin, which is formed as a gel-like substance, can be obtained.

[0015] Here, it is preferable to adjust the mixing ratio of the polyurethane polyol component and the polyurethane polyisocyanate prepolymer so that the ratio of terminal OH functional groups to NCO functional groups (OH / NCO) is between 0.6 and 1.6. Through the above adjustments, the resulting hydrophobic gel-like elastic coupler can be configured in a well-balanced, three-dimensional network structure.

[0016] The tire-type ultrasonic flaw detector of the present invention comprises the above-described hydrophobic gel elastic coupler for the ultrasonic flaw detector of the present invention, a support section that rotatably supports the hydrophobic gel elastic coupler, an ultrasonic probe housed in the support section, and an ultrasonic propagation liquid filled into the hydrophobic gel elastic coupler, and is a tire-type ultrasonic flaw detector that rotates while bringing the probe surface of the acoustic coupler into contact with an object to be inspected, and performs ultrasonic flaw detection on the object to be inspected by means of ultrasonic waves transmitted and received by the ultrasonic probe. It should be noted that regarding the hardness of the hydrophobic polyurethane gel elastic body of the present invention provided, it is preferably adjusted such that the hardness measured by an Asker rubber hardness tester type F is in the range of 35 to 80.

[0017] The tire-type ultrasonic flaw detector of the present invention is suitable for performing ultrasonic flaw detection on any one or a combination of steel structures, metal welded parts, plastic structures, concrete structures, glass structures, ceramic structures, semiconductor substrates, and human bodies.

[0018] With the above configuration, since the hydrophobic gel elastic coupler of the present invention is hydrophobic, it can be used without swelling even in measurement where water is interposed on the surface of the object to be inspected, has good ultrasonic permeability, and has sufficient flexibility to deform following the irregularities on the surface of the object to be inspected, so it can be provided as an excellent gel elastic coupler for tire-type ultrasonic flaw detectors. Effects of the Invention

[0019] By adopting the novel segmented polyurethane gel invented by the present inventor as the hydrophobic gel elastic coupler for the tire portion of a tire-type ultrasonic flaw detector, the gel elastic coupler does not swell with water even when used for a long period of time, can maintain excellent ultrasonic characteristics in a stable state, has sufficient flexibility to easily follow and deform even when continuously rotating while abutting along the surface of an object to be inspected with irregularities, and furthermore, a hydrophobic gel elastic coupler for ultrasonic flaw detectors with high durability has been realized. In short, the gel-like elastic coupler for the tire-type ultrasonic flaw detection device of the present invention is effective because, due to its hydrophobic composition, it can be used without swelling even when water is present on the surface of the object being inspected. As a gel-like elastic material, it has good ultrasonic transmission properties and sufficient flexibility to deform to conform to the surface irregularities of the object being inspected. Furthermore, it has high durability, making it suitable for long-term use. [Brief explanation of the drawing]

[0020] [Figure 1] This diagram shows the basic structure of the hydrophobic gel-like elastic coupler 100. [Figure 2] This figure shows an example configuration of a tire-type ultrasonic flaw detection device 200 equipped with a hydrophobic gel-like elastic coupler 100. [Figure 3] This diagram briefly illustrates the ultrasonic flaw detection process of a tire-type ultrasonic flaw detection device 200 equipped with a hydrophobic gel-like elastic coupler 100. [Figure 4] This diagram shows the structural formula of the polyol used as the main component for polyurethanes. [Figure 5] This figure shows the structural formula of the polyisocyanate prepolymer that serves as the curing agent. [Figure 6] This figure shows the structural formula of a polyurethane polyisocyanate prepolymer. [Figure 7] This diagram shows the composition of the samples used for verification. [Figure 8] This figure shows the results of a 24-hour water immersion experiment for each sample. [Figure 9] This is a photographic diagram showing the changes in Sample 1 before and after 24 hours of water immersion. [Figure 10] This figure shows the results of the physical property measurements for each sample. [Figure 11] This figure shows the change in ultrasonic attenuation due to differences in plasticizer content in hydrophobic gel-like elastic couplers. [Figure 12] This figure shows the basic structure of the hydrophobic gel-like elastic coupler 100a according to Example 2. [Figure 13]This diagram simply illustrates the emission and reception process during ultrasonic testing of a tire-type ultrasonic flaw detection device 200 equipped with a hydrophobic gel-like elastic coupler 100a. [Figure 14] This figure shows an example of the configuration of a tire-type ultrasonic flaw detection device disclosed in the prior art Japanese Patent Publication No. 10-267905. [Best Mode for Carrying Out the Invention]

[0021] The following describes examples of the hydrophobic gel-like elastic coupler for ultrasonic flaw detection equipment according to the present invention. However, the present invention is not limited to these examples. The hydrophobic gel-like elastic coupler for a tire-type ultrasonic flaw detection device of the present invention will be described below with examples. Example 1 is the basic structure of a hydrophobic gel-like elastic coupler for a tire-type ultrasonic flaw detection device. Example 2 is an application of a hydrophobic gel-like elastic coupler for a tire-type ultrasonic flaw detection device, in which the tire drum has a structure that includes an "ultrasonic scanning area" and an "ultrasonic non-scanning area". [Example 1]

[0022] Figure 1 shows the basic structure of the hydrophobic gel-like elastic coupler 100 of the present invention according to Example 1. Figure 1(a) is a diagram showing the configuration of the hydrophobic gel-like elastic coupler 100, and Figure 1(b) is an exploded view showing the configuration with the ribs 110 at both ends removed from the state in Figure 1(a). Figure 2 shows the hydrophobic gel-like elastic coupler 100 shown in Figure 1 attached to a tire-type ultrasonic flaw detection device 200. Figure 3 is a simplified diagram showing ultrasonic testing on an object 300 to be tested using a tire-type ultrasonic testing device 200 equipped with a hydrophobic gel-like elastic coupler 100.

[0023] As shown in Figure 1, the hydrophobic gel-like elastic coupler 100 has a structure comprising a pair of opposing ribs 110 and a cylindrical or spindle-shaped tire drum 120 formed between the ribs. Figure 1(a) is an external view of the hydrophobic gel-like elastic coupler 100, but a portion of the internal structure is shown with dotted lines to illustrate it. Figure 1(b) is an exploded view of the tire drum 120 with the ribs 110 at both ends removed. Similarly, a portion of the internal structure is shown with dotted lines to illustrate the internal design.

[0024] The rib 110 is a component that forms the end of the hydrophobic gel-like elastic coupler 100, and although the material is not limited, it is made of plastic resin, for example. The hydrophobic gel-like elastic coupler 100 is provided with a certain degree of rigidity, giving it mechanical structural strength, and is provided with sufficient rigidity to allow the hydrophobic gel-like elastic coupler 100 to be rotatably mounted on the tire-type ultrasonic flaw detection device 200, as will be described later. In this configuration example, the rib 110 has multiple screw holes 111 on its edge to connect with the tire drum 120, and screws 112 are screwed into these screw holes 111.

[0025] The tire drum 120 has a cylindrical or spindle-shaped central portion 121 with a wall thickness, and mounting edges 122 at both ends to which ribs 110 are attached. Multiple screw holes 123 are provided on the edges of the mounting edges 122 to which screws 112 are attached. On the outside of the mounting edge 122, a flange 124 is provided that forms an end face along the inside of the rib 110 when the rib 110 is attached. A cylindrical space 125 is opened in the center of the flange, which connects to the inside of the hydrophobic gel-like elastic coupler 100. In the example shown in Figure 1, the central portion 121 is a gently bulging spindle shape. As shown in Figure 2, which will be described later, when the hydrophobic gel-like elastic coupler 100 is rotatably attached to a tire-type ultrasonic flaw detection device 200 and rolls while in contact with the object to be inspected 300, the contact surface of the central portion 121 with the object to be inspected 300 deforms to conform to the surface of the object to be inspected 300.

[0026] The tire drum 120 is integrally formed as a hydrophobic gel-like elastic material. The components and the reaction that produced it will be described later. The tire drum 120 can be a single, uniform hydrophobic gel-like elastic body. The method for varying the concentration of the plasticizer added during the formation of the tire drum 120 between the ultrasonically scanned area and the non-ultrasonically scanned area will be described later in Example 2.

[0027] Figure 2 shows the hydrophobic gel-like elastic coupler 100 shown in Figure 1 attached to a tire-type ultrasonic flaw detection device 200. The diagram is shown in six views, and in the front, rear, top, and bottom views, the internal components are simply indicated with dotted lines, and the wall thickness of the tire drum 120 is also shown. In other words, the internal structure of the tire drum 120 is shown as in the vertical cross-sectional view.

[0028] As shown in Figure 2, the tire-type ultrasonic flaw detection device 200 has a structure comprising a support section 210, an ultrasonic probe 220, a front guide tire 230, a rear guide tire 240, and an ultrasonic propagation fluid 250. The tire-type ultrasonic flaw detector 200 shown in Figure 2 rotates while keeping the contact surface of the acoustic coupler 100 in close contact with the object to be inspected 300, and performs ultrasonic flaw detection on the object to be inspected 300 using ultrasonic waves transmitted and received by the ultrasonic probe 220. The hydrophobic gel-like elastic coupler 100 is used by being attached to this tire-type ultrasonic flaw detector 200.

[0029] The support section 210 comprises a frame 211, a fixed central shaft 212 fixed to the frame, and a support section 213 for the ultrasonic probe. The tire drum 120 of the acoustic coupler 100 is supported by the frame 211 and rotatably supported around the fixed rotation shaft 212. A fixed central shaft 212 is fitted and fixed to this frame 211. Therefore, as will be described later, even if the tire drum 120 rotates, the fixed central shaft 212 itself will not rotate. The material of the support part 210 is not particularly limited; it may be made of resin or metal.

[0030] The ultrasonic probe 220 is equipped with an ultrasonic transducer that emits ultrasonic waves for ultrasonic detection and receives reflected waves, and outputs the reflected ultrasonic signal to the outside. Although it is simply illustrated with a rectangular dotted line, it has the function of transmitting and receiving ultrasonic waves. This ultrasonic probe 220 (ultrasonic transducer) is positioned to transmit ultrasonic waves of a predetermined frequency in an oblique downward direction. The tire-type ultrasonic flaw detector 200 scans the surface of the object to be inspected 300 by rolling in close contact with it, but it is necessary to support the ultrasonic probe 220 itself so that it does not rotate. For this reason, the ultrasonic probe 210 is supported in the cavity inside the tire drum 120 of the acoustic coupler 100, but is supported by the support part 220 so that it does not rotate.

[0031] The front guide tire 230 has a bottom surface at the same height as the bottom surface of the rotating tire drum 120 (the surface in contact with the object to be inspected 300). In other words, it acts like a spinning top that guides the front of the tire drum 120 when it is being scanned. The rear guide tire 240 also has the same height as the bottom surface of the rotating tire drum 120 (the surface in contact with the object to be inspected 300) and the bottom surface of the front guide tire 230. It acts like a spinning top that guides the rear of the tire drum 120. In other words, because the front guide tire 230 and rear guide tire 240 are positioned in front of and behind the tire drum 120, and the height of the bottom surfaces of the front guide tire 230, rear guide tire 240, and tire drum 120 are the same, the inclination of the frame 211 becomes parallel to the surface of the object to be inspected 300, and the frame 211 is always kept at an inclination parallel to the surface of the object to be inspected 300. Assuming that the surface of the object to be inspected 300 is a horizontal plane, the effect is obtained that the frame 211 is kept horizontal.

[0032] The ultrasonic propagation fluid 250 is an ultrasonic transmission medium filled inside the acoustic coupler 100, and can be, for example, water or oil. The ultrasonic waves transmitted from the ultrasonic probe 220 (ultrasonic transducer) travel through the ultrasonic propagation fluid 250 filled inside the tire drum 120, and are further transmitted to the object to be inspected 300 via the thickness of the tire drum 120. At this time, adjustments are made to minimize the attenuation of the ultrasonic signal. Furthermore, a sealing member or the like is installed between the tire drum 120 and the frame 211 to prevent the ultrasonic propagation fluid 250 from leaking outside the tire drum 120.

[0033] This document describes the operation of the tire-type ultrasonic flaw detection device 200. Figure 3 is a simplified diagram showing the ultrasonic flaw detection process of a tire-type ultrasonic flaw detection device 200 equipped with a hydrophobic gel-like elastic coupler 100. Figure 3(a) shows the ultrasonic scanning process from the front, and Figure 3(b) shows the movement of the tire-type ultrasonic flaw detection device 200 from a top view. As shown in Figure 3, ultrasonic waves of a predetermined frequency are transmitted diagonally downward from an ultrasonic transducer 220 housed inside the tire drum 120 of the hydrophobic gel-like elastic coupler 100. The ultrasonic waves transmitted from the ultrasonic transducer 220 travel through the ultrasonic propagation fluid 250 filled inside the tire drum 120, and are further transmitted to the object to be inspected 300 via the thickened portion of the tire drum 120. A medium such as moisture (not shown) is interposed between the tire drum 120 and the object to be inspected 300. If air or the like is interposed between the ultrasonic transducer 220 and the object to be inspected 300, a change will occur in the acoustic impedance of the ultrasonic propagation path. Due to this impedance mismatch, ultrasonic waves will be reflected at the interface of air or the like, and the ultrasonic waves will not be efficiently transmitted from the ultrasonic transducer 220 to the object to be inspected 300, reducing the inspection capability. Therefore, a medium such as moisture that easily matches the impedance is interposed. The ultrasonic waves propagated to the object to be inspected 300 are reflected from its surface and returned to the ultrasonic probe 220, where the reflected ultrasonic signal is received. This reflected ultrasonic signal is converted into an electrical signal and sent to a signal analysis device (not shown), where the presence or absence of defects on the surface of the object to be inspected 300 is detected by detecting any disturbances or changes in the signal.

[0034] Next, the composition of the tire drum 120 in the hydrophobic gel-like elastic coupler 100 of the present invention will be described in detail. Due to these properties, the hydrophobic gel-like elastic coupler 100 is hydrophobic, does not swell due to moisture, and does not become cloudy.

[0035] The tire drum 120 is formed of a hydrophobic gel-like elastic material. In this example, the material for the tire drum 120 is obtained from a polyurethane resin composition which is a hydrophobic gel-like elastic body using a polyurethane polyisocyanate prepolymer having a polyurethane polyol component and a polyisocyanate component. A hydrophobic gel-like elastic material is produced using a polyurethane polyol as the main component and a polyisocyanate or polyurethane polyisocyanate prepolymer as the curing agent. Furthermore, plasticizers are added to reduce damping and impart flexibility to the gel elastic material, while catalysts are added to accelerate the urethane reaction.

[0036] The polyol and polyisocyanate components used in producing the tire drum 120 of the hydrophobic gel-like elastic coupler 100 of the present invention are as follows. First, we will explain the polyol component used in the tire drum 120 of the hydrophobic gel-like elastic coupler 100 of the present invention. Figure 4 shows the structural formula of the polyurethane polyol, which is the main component. Polyols can be monofunctional, difunctional, or trifunctional. As shown in Figure 4, the polyol component contains alkylene oxide (AO) chains. In this invention, a key feature of the polyol component is that the alkylene oxide (AO) chain is primarily a "hydrophobic AO," while the hydrophilic ethylene alkylene oxide (EO) chain is kept to a very small amount. For example, the ratio of hydrophobic alkylene oxide chains (Hydrophobic AO) to hydrophilic alkylene oxide chains (ethylene alkylene oxide chains (EO)) is within the following range. Hydrophobic alkylene oxide chain AO: Hydrophilic alkylene oxide chain EO =100:0~70:30

[0037] Here, "hydrophobic alkylene oxide chains (AO)" are defined as alkylene oxide chains that primarily consist of propylene oxide (PO), butylene oxide (BO), or mixtures thereof, with only trace amounts of ethylene oxide (EO). In other words, in this invention, the component ratio of "hydrophobic alkylene oxide chain (AO)" is: [Propylene oxide (PO), butylene oxide (BO), or mixtures thereof]:[Ethylene oxide (EO)] = 100:0~70:30 This will be within the range of [the specified range]. Thus, although the polyol component used to produce tire drum 120 contains alkylene oxide chains, the main component of the alkylene oxide chain is "hydrophobic alkylene oxide (Hydrophobic AO)," and hydrophilic alkylene oxide chains are either absent or present in trace amounts.

[0038] If the alkylene oxide chain contained in the polyol component is ethylene oxide (EO), the resulting urethane resin will be hydrophilic. However, the tire drum 120 of the gel-like elastic coupler 100 of the present invention is characterized by being hydrophobic. Therefore, by not containing ethylene oxide (EO) as the alkylene oxide chain in the polyol component, or by keeping it to a trace amount, hydrophobicity is achieved by using propylene oxide (PO), butylene oxide (BO), or a mixture thereof. The polyol can be either a polyether polyol or a polyester polyol. These can be used alone, or mixed with other known polyols as long as it does not interfere with the reaction or the final product.

[0039] Next, we will describe the polyisocyanate component used as a curing agent in the tire drum 120 of the hydrophobic gel-like elastic coupler 100 of the present invention. Figure 5 shows the structural formula of the polyisocyanate prepolymer used as a curing agent. In this example, a prepolymerized polyisocyanate is used. In this example, diisocyanates are used as polyisocyanates. Examples of suitable isocyanate species include hexamethylene diisocyanate (HDI) and its derivatives, 4,4-diphenylmethane diisocyanate (MDI), 2,4-toluene diisocyanate (TDI), naphthalene 1,5-diisocyanate (NDI), and xylylene diisocyanate (XDI). Other known polyisocyanates may be mixed and used as long as they do not interfere with the reaction or the final product.

[0040] Furthermore, alicyclic isocyanate species can also be used as polyisocyanates. For example, alicyclic isocyanate species such as trans-1,4-bis(isocyanatomethyl)cyclohexane (1,4-H6 XDI), isophorone diisocyanate (IPDI), 4,4-methylenebis(cyclohexyl isocyanate) (hydrogenated MDI: H12MDI), and bis(isocyanatomethyl)cyclohexane (hydrogenated XDI: H6XDI) can be used.

[0041] Although the polyisocyanate components mentioned above also contain alkylene oxide chains, the alkylene oxide chains in the polyisocyanate components of this Example 1 mainly consist of propylene oxide (PO), butylene oxide (BO), or mixtures thereof, and hydrophobicity is achieved by limiting the amount of ethylene oxide (EO) to a very small amount. If ethylene oxide (EO) is the main alkylene oxide chain contained in the polyisocyanate component, the resulting urethane resin will be hydrophilic. However, since the tire drum 120 of the gel-like elastic coupler of the present invention is characterized by being hydrophobic, it is preferable to use propylene oxide (PO), butylene oxide (BO), or a mixture thereof as the main alkylene oxide chain in the polyisocyanate component, and to keep the amount of ethylene oxide (EO) to a minimum. Furthermore, the alkylene oxide chains (AO) contained within it mainly consist of propylene oxide (PO), butylene oxide (BO), and hydrophobic alkylene oxide chains (Hydrophobic AO), which are mixtures thereof, while the hydrophobic properties are achieved by keeping the amount of ethylene oxide (EO) to a minimum.

[0042] While polyisocyanates primarily consist of difunctional and trifunctional polyisocyanates, it is acceptable for them to be a mixture of difunctional and trifunctional polyisocyanates, rather than being 100% monofunctional. Furthermore, while difunctional and trifunctional polyisocyanates are primarily used to form the network structure of gel-like elastic materials, as will be discussed later, monofunctional polyisocyanates may be used when used as plasticizers.

[0043] Next, we will describe the polyurethane polyisocyanate prepolymer produced under these conditions. Figure 6(a) shows the structural formula of a bifunctional polyurethane polyisocyanate prepolymer. Figure 6(b) shows the structural formula of a trifunctional polyurethane polyisocyanate prepolymer. As described above, the (AO) chain included in the above structural formula refers to a hydrophobic alkylene oxide chain. It mainly consists of either propylene oxide (PO) or butylene oxide (BO) or a mixture thereof, with ethylene oxide chain (EO) present in only trace amounts. Thus, in this invention, the alkylene oxide chain is defined as a "hydrophobic alkylene oxide chain (Hydrophobic AO)". Generally, alkylene oxide chains also contain ethylene oxide chains (EO), but those containing a large amount of ethylene oxide chains (EO) tend to be hydrophilic. Therefore, in the hydrophobic gel-like elastic coupler 100 of the present invention, the amount of ethylene oxide chains (EO) is kept to a very small level in the tire drum 120.

[0044] Thus, by using a "hydrophobic alkylene oxide chain (Hydrophobic AO)" for the alkylene oxide chain of the polyurethane polyisocyanate prepolymer, a hydrophobic gel elastic body can be obtained after curing with a curing agent. As will be described later, the tire drum 120 of the gel elastic body coupler 100 that was actually manufactured exhibits hydrophobic properties.

[0045] Next, we will describe the number of functional groups and the average molecular weight of the polyol component that forms the main component of the tire drum 120 of the hydrophobic gel-like elastic coupler 100 of the present invention. As polyol components, polyols with two functional groups and a number-average molecular weight of 1,000 to 6,000, and polyols with three functional groups and a number-average molecular weight of 3,500 to 5,000 are used. Furthermore, preferably, the number-average molecular weight of the polyol with two functional groups is in the range of 3,000 to 3,500, and the number-average molecular weight of the polyol with three functional groups is in the range of 4,000 to 4,500.

[0046] Thus, the number of functional groups in the polyol for polyurethane is configured as a three-dimensional network structure of urethane bonds, resulting in the elasticity of the urethane resin formed as a gel-like substance. On the other hand, in order to produce a tire drum 120 of the hydrophobic gel-like elastic coupler 100 of the present invention with great flexibility, it is necessary to increase the molecular weight, OH / NCO ratio, or plasticizer content.

[0047] In the following explanation, we will use difunctional and trifunctional polyether polyols as examples, but the number of functional groups in polyols for polyurethane does not need to be 100% uniform; it is acceptable for some to be difunctional and trifunctional, and for a very small amount to be monofunctional.

[0048] Regarding polyols with two functional groups and a number-average molecular weight of 1,000 to 6,000, the lower the number-average molecular weight, the higher the hardness of the resulting polyurethane resin. Therefore, if the number-average molecular weight is less than 2,500, the hardness of the resulting polyurethane resin will be greater than 80 on the Asker rubber hardness meter F, which is undesirable for the hydrophobic gel-like elastic coupler of the present invention. On the other hand, if the number-average molecular weight exceeds 4,000, it is presumed that the chemical reaction does not proceed sufficiently, and the resulting polyurethane resin lacks shape stability, which is undesirable.

[0049] Next, regarding polyols with three functional groups and a number-average molecular weight of 1,000 to 6,000, if the number-average molecular weight is less than 2,000, the hardness of the resulting polyurethane resin will be greater than 80 on the Asker rubber hardness meter F-type, which is undesirable for the hydrophobic gel-like elastic coupler of the present invention. On the other hand, if the number-average molecular weight exceeds 6,000, it is presumed that a sufficient crosslinking density cannot be obtained, which is undesirable because the surface of the resulting polyurethane resin becomes too tacky (adhesive) or curing is poor. Polyols for polyurethanes primarily consist of difunctional and trifunctional polyols. However, it is not necessary for polyurethane polyols to be 100% difunctional or trifunctional; a mixture of difunctional and trifunctional polyols is acceptable, as is a small amount of monofunctional polyols. While polyisocyanates primarily consist of difunctional and trifunctional polyisocyanates, it is acceptable for them to be a mixture of difunctional and trifunctional polyisocyanates, rather than being 100% monofunctional. Furthermore, while difunctional and trifunctional polyisocyanates are primarily used to form the network structure of gel-like elastic materials, as will be discussed later, monofunctional polyisocyanates may be used when used as plasticizers.

[0050] Here, the number of functional groups in the polyisocyanate is adjusted so that the polyol component and the polyisocyanate component do not have a combination of two functional groups. In other words, the combinations of functional groups in the polyol and polyurethane polyisocyanate prepolymer are 2 and 3, 3 and 2, or 3 and 3, and are adjusted so that there are no combinations of 2. Thus, the number of functional groups in the polyol and polyisocyanate components is configured as a three-dimensional network structure of urethane bonds, and the elasticity of the urethane resin formed as a gel-like substance is obtained, so it is sufficient to adjust the balance between the number of difunctional groups and the number of trifunctional groups.

[0051] Next, we will describe the methods for producing the hydrophobic gel-like elastic coupler of the present invention in a way that gives it great flexibility. Some of the techniques used to achieve this include increasing the molecular weight or OH / NCO ratio, or increasing the plasticizer content. For example, regarding the mixing ratio of the polyol component to the polyurethane polyisocyanate prepolymer, if the ratio of terminal OH functional groups to NCO functional groups (OH / NCO) is adjusted to be between 0.6 and 1.6, the resulting hydrophobic gel-like elastic coupler will be well-balanced as a three-dimensional network structure.

[0052] Next, I will explain methods for increasing the plasticizer content and improving flexibility. In the hydrophobic gel-like elastic coupler 100 of the present invention, the tire drum 120 is designed to have sufficient flexibility and the ability to easily follow deformation even when continuously rotating while in contact with the uneven surface of the object to be inspected. To achieve this, a large amount of plasticizer is incorporated to ensure flexibility. Examples of plasticizers include propylene carbonate, ethylene carbonate, N-methyl-2-pyrrolidone, diisononylcyclohexane 1,2-dicarboxylate, or glycol ethers. Glycol ethers may include propylene glycol dimethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, and tetrapropylene glycol dimethyl ether.

[0053] The hardness of the hydrophobic polyurethane gel elastic material, as indicated by the Asker rubber hardness tester Type F, is preferably adjusted to a range of 35 to 80. This level of flexibility allows the material to deform to conform to the surface irregularities of the object being inspected, providing excellent physical properties as an elastic coupler during ultrasonic measurement.

[0054] The following describes a prototype example of a hydrophobic gel-like elastic coupler for ultrasonic flaw detection equipment according to the present invention. The results of investigating the physical properties of the hydrophobic gel-like elastic coupler using the actually produced sample are shown. Figure 7 shows the composition of the samples used for verification. As shown in Figure 7, Samples 1 and 2, which belong to the hydrophobic gel-like elastic coupler of the present invention, were produced, and Sample 3, a conventional hydrophilic elastic coupler, was prepared as a control. The main component, a polyurethane polyol, the curing agent, a polyisocyanate, and the plasticizer are as shown in the list in Figure 7, but Sample 1 and Sample 2 differ from Sample 3 in the presence or absence of alkylene oxide chains (AO).

[0055] The composition of Sample 1 was as follows: For Sample 1, a trifunctional PPG polyether polyol was used as the main component, a polyol for polyurethane. In other words, the alkylene oxide chain (AO) is a polypropylene glycol (PPG) chain in which the alkylene oxide chain (Hydrophobic AO) is present. As an example, Primepol FF-3320 (manufactured by Sanyo Chemical Industries, Ltd.) was used. For Sample 1, an HDI polyisocyanate prepolymer was used as the curing agent. In other words, a prepolymer obtained by the reaction of propylene oxide (PO), in which the alkylene oxide chain (AO) is hydrophobic alkylene oxide (Hydrophobic AO), with hexamethylene diisocyanate (HDI) was used. As an example, Duranate AE700-100 (manufactured by Asahi Kasei Corporation) was used. Diisononylcyclohexane 1,2-dicarboxylate (DINCH) was used as the plasticizer in Sample 1. Hexamol DINCH (manufactured by BASF) was used as an example. The plasticizer content was 50 wt%. This sample 1 is a prototype of a hydrophobic gel-like elastic coupler.

[0056] The composition of Sample 2 was as follows: The main component of Sample 2, a polyurethane polyol, was also a trifunctional PPG polyether polyol. In other words, propylene oxide (PO), in which the alkylene oxide chain (AO) is hydrophobic alkylene oxide (Hydrophobic AO), polymerizes to form polypropylene glycol (PPG) chains. As an example, Primepol FF-3320 (manufactured by Sanyo Chemical Industries, Ltd.) was used. For Sample 2, the curing agent, a polyisocyanate prepolymer containing bis(isocyanatomethyl)cyclohexane (H6XDI) as the isocyanate species, was used. As an example, Fortimo XHL-8120A (manufactured by Mitsui Chemicals, Inc.) was used. Fortimo XHL-8120A is a polyisocyanate prepolymer obtained by reacting an ether-based polyol with bis(isocyanatomethyl)cyclohexane (H6XDI), and its alkylene oxide chain (AO) is propylene oxide (PO), i.e., a hydrophobic alkylene oxide chain (Hydrophobic AO). For Sample 2, diisononylcyclohexane 1,2-dicarboxylate (DINCH) was used as the plasticizer. Hexamol DINCH (manufactured by BASF) was used as an example. The plasticizer content was 50 wt%. This Sample 2 is also a prototype of a hydrophobic gel-like elastic coupler.

[0057] The composition of Sample 3, which served as the control for comparison, was as follows: The main component of Sample 3, a polyurethane polyol, is a bifunctional polyether polyol, specifically polyoxyethylene polyoxypropylene glycol, formed by the polymerization of ethylene oxide (EO), which has a hydrophilic alkylene oxide chain (AO), and propylene oxide, which has a hydrophobic alkylene oxide chain (AO). As an example, Toho Polyol PB-3050 (manufactured by Toho Chemical Industry Co., Ltd.) was used. This Toho Polyol PB-3050 is a polyether polyol with an EO to PO ratio of 50:50, and is an amphiphilic and hydrophilic urethane gel. For Sample 3, the curing agent, polyisocyanate, was an HDI polyisocyanate prepolymer. This prepolymer was obtained by the reaction of polyoxyethylene polyoxypropylene glycol, which is formed by the polymerization of ethylene oxide (EO), a hydrophilic alkylene oxide chain (AO), and propylene oxide, a hydrophobic alkylene oxide chain (AO), with hexamethylene diisocyanate (HDI). As an example, H-6X35-2 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used. This H-6X35-2 is a prepolymer obtained by reacting a polyether polyol with an EO to PO ratio of 50:50 with HDI, and is amphiphilic and hydrophilic. Sample 3 uses tetraethylene glycol dimethyl ether (TG) as the plasticizer. As an example, Tetragrime (manufactured by Maruzen Yuka Shoji Co., Ltd.) was used. The plasticizer content was 55 wt%. Sample 3 is a prototype of a highly hydrophilic gel-like elastic coupler.

[0058] As described above, we conducted a comparative physical property test using Sample 1, Sample 2, and Sample 3. First, the results of the hydrophobic-hydrophilic physical property tests are shown. Figure 8 shows the results of a 30-day water immersion experiment for Sample 1, Sample 2, and Sample 3. Figure 8 summarizes the mass before water immersion (g), the mass after 24 hours of water immersion (g), and the percentage change in mass (%).

[0059] In Sample 1 of the present invention, there was little change in mass after 24 hours of immersion in water, as shown in Figure 8. This confirmed that the material did not absorb water and possessed hydrophobic properties. Figure 9(a) is a photograph showing the changes in Sample 1 before and after 24 hours of water immersion. There was no swelling or shrinkage, and there was almost no change in appearance. Excellent hydrophobicity was confirmed.

[0060] In Sample 2 of the present invention, the hydrophobic gel-like elastic material showed little change in mass after 24 hours of immersion in water, as shown in the list in Figure 8. This result confirmed that the material did not absorb water and possessed hydrophobic properties. Figure 9(b) is a photograph showing the changes in Sample 2 before and after 24 hours of water immersion. There was no swelling or shrinkage, and the appearance remained almost unchanged. Excellent hydrophobicity was confirmed.

[0061] In the conventional hydrophilic gel-like elastic material of Sample 3, immersion in water for 24 hours resulted in a significant increase in mass, as shown in the list in Figure 4. This confirmed that it absorbs water well and exhibits hydrophilicity. Figure 9(c) is a photograph showing the condition of sample 3 after 24 hours of water immersion. The entire sample has swollen significantly, and its composition has deteriorated considerably, with cracks already forming and the sample becoming brittle after just 24 hours. This result clearly illustrates why conventional hydrophilic materials are unsuitable as elastic couplers for industrial applications where water is frequently used.

[0062] From the above, it was found that the hydrophobic gel-like elastic material of the present invention possesses hydrophobic properties and does not swell without absorbing water. This hydrophobic property prevents the swelling problem that plagued conventional hydrophilic gel-like elastic couplers, thus preventing changes in ultrasonic properties and deterioration such as cracking and wear during use.

[0063] The hydrophobic gel-like elastic coupler 100 of the present invention possesses flexible and pliable physical properties, and does not have the rigid physical properties typical of general hydrophobic gel-like elastic materials. Therefore, it has been confirmed that it is suitable for detecting flaws in objects with uneven surfaces.

[0064] Next, we investigated the ultrasonic properties of the hydrophobic gel elastic coupler 100 of the present invention. The ultrasonic properties of hydrophobic polyurethane gel elastic couplers, specifically their ultrasonic transmission, can be verified by the value of the ultrasonic attenuation coefficient. For ultrasonic attenuation measurements, a Smartor ultrasonic flaw detector (manufactured by Shantou Institute of Ultrasonic Instruments Co., Ltd.) was used. The probe used was a TGM5-10 (manufactured by Shantou Institute of Ultrasonic Instruments Co., Ltd.). The frequency used was 5 MHz. Measurements were taken in a room with the air conditioning set to 20°C.

[0065] As shown in Figure 10, the ultrasonic attenuation of Sample 1 of the present invention was 4.32 dB / cm, Sample 2 of the present invention was 4.79 dB / cm, and the hydrophilic Sample 3 of the prior art was 3.43 dB / cm. The measurement results showed that Sample 3, a hydrophilic gel-like elastic coupler from the conventional technology, exhibited the lowest ultrasonic attenuation. However, Samples 1 and 2, which are hydrophobic gel-like elastic couplers of the present invention, also showed similarly low ultrasonic attenuation and were superior in this respect. From the above, it has been verified that the hydrophobic gel elastic coupler 100 of the present invention has excellent ultrasonic properties.

[0066] As described above, the advantages of the ultrasonic properties of the hydrophobic gel-like elastic coupler of the present invention compared to hydrophilic elastic couplers of the conventional technology were verified. Furthermore, we investigated the changes in acoustic impedance and attenuation coefficient as ultrasonic properties due to differences in the plasticizer content of the hydrophobic gel-like elastic coupler.

[0067] Figure 11 shows the changes in ultrasonic acoustic impedance and attenuation coefficient due to differences in plasticizer content in hydrophobic gel-like elastic couplers. As shown in Figure 11, it was found that the attenuation of ultrasound is also affected by the plasticizer content.

[0068] First, regarding the plasticizer content, it was found that in the range of 0 to 80 wt%, the ultrasonic attenuation decreased as the plasticizer content increased. For both Sample 1 and Sample 2, ultrasonic attenuation characteristics were obtained when the plasticizer content was 30 wt%. In samples 1 and 2, the ultrasonic attenuation was sufficiently reduced when the plasticizer content was 50 wt%.

[0069] Regarding the upper limit, exceeding 80 wt% may make it difficult to stabilize the shape of the urethane resin, so it is considered appropriate to keep it around 80 wt%. In summary, the plasticizer content in the hydrophobic gel-like elastic coupler of the present invention is preferably in the range of 0 wt% to 80 wt%, more preferably 30 wt% to 80 wt%, and more preferably 50 wt% to 80 wt%. [Example 2]

[0070] Example 2 is an application of a hydrophobic gel-like elastic coupler for a tire-type ultrasonic flaw detection device, in which the tire drum has a structure that includes an "ultrasonic scanning area" and an "ultrasonic non-scanning area". Figure 12 shows an example configuration of a tire-type ultrasonic flaw detection device 200 equipped with a hydrophobic gel-like elastic coupler 100a according to Example 2. Figure 12(a) is a front view, part 1, which primarily depicts the ultrasonic scanning area 125 and the surrounding non-ultrasonic scanning area 126 in the external view. Figure 12(b) is a second front view, in which a portion of the internal structure of the hydrophobic gel-like elastic coupler 100a is depicted with dotted lines. The thickness of the tire drum 120a is also shown. Figure 12(c) is a plan view, and similarly, a portion of the interior of the hydrophobic gel-like elastic coupler 100a is drawn with dotted lines to show its internal structure, and the thickness of the tire drum 120a is represented.

[0071] As shown in Figure 12, the hydrophobic gel-like elastic coupler 100a has a structure similar to that of Example 1, with ribs 110 and a tire drum 120a. However, as shown in Figure 12(a), the tire drum 120a of Example 2 has a structure in which the area near the center of the tire drum 120a is an ultrasonic scanning area 125 and the peripheral area is an ultrasonic non-scanning area 126.

[0072] In this configuration example, the ultrasonic scanning area 125 is a circulating area that includes the area directly below the ultrasonic transducer 220 near the center. In other words, it is an area that passes directly below the ultrasonic transducer 220 due to the rotation of the tire drum 120a. The range of the ultrasonic scanning area 125 on the tire drum 120a is an area that encompasses the region through which the ultrasonic waves emitted by the ultrasonic transducer 220 pass and are reflected from the inspection point of the object 300 being inspected.

[0073] The area forming the ultrasonic scanning area 125 has a large OH / NCO ratio. On the other hand, the area forming the non-ultrasonic scanning area 126 has a small OH / NCO ratio. In this way, the flexibility of the ultrasonic scanning area 125 is adjusted to be greater than the flexibility of the non-ultrasonic scanning area 126. For example, the amount of plasticizer added in the ultrasonic scanning area 125 is set to 50-80 wt%, and the amount of plasticizer added in the non-ultrasonic scanning area 126 is set to 30 wt% or more and less than 50 wt%.

[0074] In the hydrophobic gel-like elastic coupler 100a shown in this embodiment 2, the ultrasonic scanning area 125 is sufficiently flexible to follow even minute irregularities on the surface of the object to be inspected 300. On the other hand, the ultrasonic non-scanning area 126 has a certain degree of mechanical structural strength and rigidity, resulting in a hydrophobic gel-like elastic coupler 100a suitable for a tire-type ultrasonic flaw detection device 200.

[0075] Regarding the boundary between the ultrasonic scanning area 125 and the non-ultrasonic scanning area 126, a clear boundary is acceptable, but a gradient is also acceptable. A gradient can be achieved by clearly adjusting the OH / NCO ratio for each area when forming a gel from a polyurethane polyisocyanate prepolymer containing a polyurethane polyol component and a polyisocyanate component, or by increasing the OH / NCO ratio near the center of the area forming the ultrasonic scanning area 125 and decreasing the OH / NCO ratio near the area forming the non-ultrasonic scanning area 126.

[0076] Next, we will explain the emission and reception of ultrasonic waves during ultrasonic testing using a tire-type ultrasonic flaw detection device 200a equipped with the hydrophobic gel-like elastic coupler 100a according to Example 2. Figure 13 is a simplified diagram showing the emission and reception of ultrasonic waves during ultrasonic testing by a tire-type ultrasonic flaw detection device 200a equipped with a hydrophobic gel-like elastic coupler 100a. Figure 13 shows the ultrasonic scanning process from the front.

[0077] As shown in Figure 13, ultrasonic waves of a predetermined frequency are transmitted diagonally downward from an ultrasonic probe 220 housed inside the tire drum 120a of the hydrophobic gel-like elastic coupler 100a. The ultrasonic waves transmitted from the ultrasonic probe 220 travel through the ultrasonic propagation fluid 250 filled inside the tire drum 120a, and are further transmitted to the object to be inspected 300 via the ultrasonic scanning area 125 of the tire drum 120a. The ultrasonic waves propagated to the object to be inspected 300 are reflected from its surface and return to the ultrasonic probe 220 via the ultrasonic scanning area 125, where the reflected ultrasonic signal is received.

[0078] Thus, the emission and reception of ultrasonic waves during ultrasonic testing are performed in the same manner as in Example 1. The physical properties of the ultrasonic scanning area 125 are such that they possess an ultrasonic attenuation coefficient and acoustic impedance suitable for testing the object 300. They are highly flexible and can adequately follow the surface irregularities of the object 300, and do not swell or become cloudy even after prolonged exposure to moisture. Therefore, the hydrophobic gel-like elastic coupler 100a of this Example 2 is an excellent acoustic coupler. Furthermore, by providing an ultrasonic non-scanning area 126 to increase rigidity, the disadvantage that the ultrasonic scanning area 125 alone does not provide sufficient rigidity can be compensated for.

[0079] As described above, preferred embodiments of the configuration of a hydrophobic gel-like elastic coupler for an ultrasonic flaw detection device of the present invention have been illustrated and explained, but it will be understood that various modifications are possible without departing from the technical scope of the present invention. [Industrial applicability]

[0080] The hydrophobic gel-like elastic coupler for ultrasonic flaw detection equipment of the present invention can be widely applied as a hydrophobic gel-like elastic coupler for ultrasonic flaw detection equipment used for surface flaw detection of steel structures, metal welds, plastic structures, concrete structures, glass structures, ceramic structures, semiconductor substrates, and the like. [Explanation of symbols]

[0081] 100 Hydrophobic gel-like elastic coupler 110 Rib 111 Screw holes 112 Screw 120 Tire Drum 121 Central part 122 Edge 123 Screw holes 124 Flange 125 Space 200 Tire-type ultrasonic flaw detector 210 Support part 211 frames 212 Fixed center axis 213 Support part for ultrasonic probe 220 Ultrasonic probe 230 Front Guide Tire 240 Rear guide tire 250 Ultrasonic Propagation Solution 300 Objects to be inspected for defects

Claims

1. An acoustic coupler used in a tire-type ultrasonic flaw detection apparatus, comprising a support part that rotatably supports the acoustic coupler around a rotation axis, an ultrasonic probe housed in the support part, and an ultrasonic propagation fluid filled inside the acoustic coupler, wherein the acoustic coupler rotates while its probe surface is in contact with the object to be inspected, and ultrasonic flaw detection is performed on the object to be inspected by ultrasonic waves transmitted and received by the ultrasonic probe, The acoustic coupler comprises a pair of opposing ribs and a cylindrical or spindle-shaped tire drum provided between the pair of ribs. The aforementioned tire drum is made of a hydrophobic gel-like elastic material, In the aforementioned tire drum, an ultrasonic scanning area is provided that includes the region through which ultrasonic waves emitted by the ultrasonic probe pass and are reflected from the flaw detection location of the object to be inspected, and an ultrasonic non-scanning area is provided that includes the rest of the area. A hydrophobic gel-like elastic coupler for a tire-type ultrasonic flaw detection device, characterized in that the flexibility of the ultrasonic scanning area is adjusted to be greater than the flexibility of the non-ultrasonic scanning area.

2. The tire drum of the hydrophobic gel-like elastic coupler is obtained from a polyurethane resin composition which is a hydrophobic gel-like elastic body produced by adding a plasticizer to a polyurethane polyisocyanate prepolymer formed from a polyurethane polyol component as the main component and a polyisocyanate component as a curing agent. The hydrophobic gel-like elastic coupler for an ultrasonic flaw detection apparatus according to claim 1, characterized in that the amount of plasticizer added is 30 to 80 wt%.

3. The hydrophobic gel-like elastic coupler for an ultrasonic flaw detection apparatus according to claim 2, characterized in that propylene carbonate, ethylene carbonate, N-methyl-2-pyrrolidone, diisononylcyclohexane 1,2-dicarboxylate, or glycol ethers are added as plasticizers when the tire drum is formed.

4. As the polyisocyanate component of the tire drum curing agent, A hydrophobic gel-like elastic coupler for an ultrasonic flaw detection apparatus according to claim 2, comprising any isocyanate species of hexamethylene diisocyanate, 4,4-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, naphthalene 1,5-diisocyanate, xylylene diisocyanate or a derivative thereof, or any alicyclic isocyanate species of isophorone diisocyanate, 4,4-methylenebis(cyclohexane isocyanate), bis(isocyanatomethyl)cyclohexane or a derivative thereof.

5. In the hydrophobic gel-like elastic material of the tire drum, the ratio of hydrophobic alkylene oxide chains to hydrophilic alkylene oxide chains among the alkylene oxide chains contained in the hydrophobic polyurethane polyol component, i.e., the ratio of hydrophobic alkylene oxide chains to hydrophilic alkylene oxide chains, is adjusted to between 100:0 and 70:

30. The alkylene oxide chain contained in the polyisocyanate component is a hydrophobic alkylene oxide chain, The hydrophobic gel-like elastic coupler for an ultrasonic flaw detection apparatus according to claim 2, wherein the hydrophobic gel-like elastic body of the tire drum is a non-foam hydrophobic polyurethane gel-like elastic body.

6. The polyurethane polyol component of the hydrophobic gel-like elastic body of the tire drum is a component that includes either or both of the following: a polyol with 2 functional groups and a number average molecular weight of 1,000 to 6,000, or a polyol with 3 functional groups and a number average molecular weight of 3,500 to 5,000. The hydrophobic gel-like elastic coupler for an ultrasonic flaw detection apparatus according to claim 2, characterized in that the combination of the number of functional groups of the polyurethane polyol component and the number of functional groups of the polyisocyanate prepolymer is 2 and 3, 3 and 2, or 3 and 3, and is not a combination of 2 and 3.

7. The hydrophobic gel-like elastic coupler for an ultrasonic flaw detection apparatus according to claim 6, characterized in that the mixing ratio of the polyurethane polyol component and the polyurethane polyisocyanate prepolymer is adjusted so that the ratio of terminal OH functional groups to NCO functional groups (OH / NCO) is between 0.6 and 1.

6.

8. The hydrophobic gel-like elastic coupler for an ultrasonic flaw detection apparatus according to claim 7, characterized in that, in the OH / NCO ratio, which is the ratio of terminal OH functional groups to NCO functional groups in the mixture of the polyurethane polyol component and the polyurethane polyisocyanate prepolymer, the ratio of the portion of the tire drum that forms the non-ultrasonic scanning area is adjusted to be smaller than the ratio of the ultrasonic scanning area.

9. A hydrophobic gel-like elastic coupler for an ultrasonic flaw detection apparatus according to any one of claims 1 to 8, A support portion that rotatably supports the hydrophobic gel-like elastic coupler, The ultrasonic probe housed in the support section, The hydrophobic gel-like elastic coupler is filled with an ultrasonic propagation liquid, A tire-type ultrasonic flaw detection device that rotates and moves the acoustic coupler while bringing its probe surface into contact with the object to be detected, and performs ultrasonic flaw detection on the object using ultrasonic waves transmitted and received by an ultrasonic probe.

10. The ultrasonic flaw detection apparatus according to claim 9, wherein the object to be inspected is any of the following: a steel structure, a metal weld, a plastic structure, a concrete structure, a glass structure, a ceramic structure, a semiconductor substrate, the human body, or a combination thereof.

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