JP2013057521A - Ultrasonic wave generation method and nondestructive inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic wave generation method which prevents generation of laser marks due to ablation and suitably generates an ultrasonic wave without depending on the material or the shape of an object, and a nondestructive inspection method.SOLUTION: An ultrasonic wave generation method typically includes generation of an ultrasonic wave transmitted through an object 100 having a base material 102 of metal. At least a part of a surface 102a of the base material is provided with a resin film 106 of a high polymer material which is laser beam-impermeable and fire-resistant. The region with the resin film in the surface of the object is exposed to a laser beam causing ablation, so that an ultrasonic wave transmitting through the object is generated.

Description

  The present invention relates to an ultrasonic generation method for generating an ultrasonic wave propagating through an object by irradiating a laser beam toward the surface of the object to generate ablation, and a nondestructive inspection method using the same. is there.

  Nondestructive inspection is an inspection method for detecting internal defects, fine scratches, thin film peeling (hereinafter simply referred to as defects) in an object (inspected object) without destroying the object. For nondestructive inspection, radiation, ultrasonic waves, infrared rays, or the like is used. Among these, in the case of using an ultrasonic wave, there is a method of generating an ultrasonic wave using ablation (also referred to as removal processing) by laser light (hereinafter referred to as a laser ultrasonic method).

  In the laser ultrasonic method, the surface (work surface) of an object is irradiated with laser light (laser irradiation). The energy of the laser beam causes ablation, which is a phenomenon in which the surface layer of the object evaporates and vaporizes. Ultrasonic waves are generated as a reaction of the ablation and propagate through the object. And the defect of a to-be-tested object is detected by the intensity | strength change etc. of the propagated ultrasonic wave or reflected wave.

  In the nondestructive inspection using the laser ultrasonic method described above, the object is not destroyed, but the surface of the object is damaged by ablation, which causes a laser mark on the appearance. ing. In order to solve this problem, for example, in Patent Document 1, a thin plate is placed in contact with the surface of an object (test object), and the thin plate is irradiated with laser light (pulse light or intensity-modulated light). According to Patent Document 1, when laser light is irradiated, ablation occurs on the surface of a thin plate, and ultrasonic waves generated thereby propagate to the thin plate, the contact surface between the thin plate and the device under test, and eventually to the device under test. , It does not cause damage to the DUT.

Japanese Patent Laid-Open No. 10-128236

  Furthermore, Patent Document 1 describes that the same material is used for the thin plate and the object in order to suppress the generation of reflected waves when ultrasonic waves propagate from the thin plate to the object (test object). . However, in industrial products, there are many materials that are difficult to process into a thin plate shape even if processing such as casting and extrusion is easy. For this reason, in Patent Document 1, it is difficult to say that the applicable materials are limited and the versatility is excellent, and if the thin plate and the object are made of different materials, as described above, accurate inspection is performed due to the generation of reflected waves. You may not be able to. In addition to industrial products, processed products rarely have a flat surface, and generally have undulations, irregularities or roughness. Therefore, it is extremely difficult to bring the thin plate into contact with the object. Then, a gap due to poor contact occurs, and a reflected wave is generated at the interface between the thin plate and the object, which also causes a decrease in inspection accuracy.

  In view of such a problem, the present invention provides an ultrasonic generation method capable of suitably generating ultrasonic waves and obtaining high accuracy without depending on the material or shape of an object while preventing generation of laser marks due to ablation. It aims to provide a non-destructive inspection method.

  In order to solve the above problems, a typical configuration of an ultrasonic wave generation method according to the present invention is an ultrasonic wave generation method for generating an ultrasonic wave propagating through an object having a metal base material. A resin film made of a polymer material having laser light impermeability and flame retardancy is formed on at least a part of the surface of the substrate, and the region of the surface of the object on which the resin film is formed is irradiated with laser light. An ultrasonic wave propagating through the object is generated by causing ablation.

  Since the resin film has flame retardancy, it does not burn even if ablation occurs on the surface of the resin film due to laser irradiation. Further, since the resin film does not transmit laser light (laser light non-transmitting property), it is possible to prevent the laser light from reaching the surface of the object. Therefore, by forming a resin film in the region irradiated with laser light in the object as in the above configuration, the surface of the object can be protected by the resin film when ultrasonic waves are generated by ablation. It is possible to prevent generation of laser marks due to ablation. Further, since the resin film has flexibility, it can easily follow the surface of the curved substrate. Therefore, the resin film and the object can be satisfactorily contacted (adhered) without depending on the shape of the object. Therefore, no gap is generated between the object and the resin film, and noise caused by the gap is suppressed. For this reason, if the ultrasonic wave generation method of the present invention is applied to a nondestructive inspection method, high inspection accuracy can be obtained.

  The resin film may be made of triacetyl cellulose or polyvinyl chloride. These substances are most suitable as resin films because they are excellent in laser beam impermeability and flame retardancy among many polymer materials.

  The region where the resin film is formed in the substrate is preferably curved. As described above, the ultrasonic wave generation method of the present invention is particularly suitable for a curved substrate.

  Said resin film is a sheet-like film, Comprising: It is good to form by apply | coating an adhesive material on a base material and adhere | attaching a film. According to this configuration, it is possible to easily form the resin film on the substrate.

  In order to solve the above problems, a typical configuration of a nondestructive inspection method according to the present invention is a nondestructive inspection method for inspecting a defect of an object having a metal base material by ultrasonic waves. A resin film made of a polymer material having laser light impermeability and flame retardancy is formed on at least a part of the surface of the substrate, and the region of the surface of the object on which the resin film is formed is irradiated with laser light. By generating ablation, ultrasonic waves that propagate through the object are generated, and the receiving apparatus disposed on the opposite side of the object on which the resin film is formed receives the ultrasonic waves propagated through the object and is opposed to it. The displacement measurement of the surface of the side is performed. The component corresponding to the technical idea in the ultrasonic wave generation method mentioned above and its description are applicable also to the said nondestructive inspection method.

  According to the present invention, there is provided an ultrasonic generation method and a nondestructive inspection method capable of suitably generating ultrasonic waves and obtaining high accuracy without depending on the material or shape of an object while preventing generation of laser marks due to ablation. Can be provided.

It is the schematic explaining the ultrasonic wave generation method and nondestructive inspection method concerning this embodiment. It is a figure which illustrates the displacement measurement result by the nondestructive inspection method of this embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  FIG. 1 is a schematic diagram illustrating an ultrasonic generation method and a nondestructive inspection method according to the present embodiment. As shown in FIG. 1, in the ultrasonic wave generation method according to the present embodiment, laser light (illustrated by a one-dot chain line) is irradiated toward the surface of the object 100 to cause ablation to propagate through the object 100. Ultrasound (illustrated with wavy lines) is generated. Further, in the nondestructive inspection method of the present embodiment, the presence or absence of a defect in the object 100 by the ultrasonic wave generated by the above-described ultrasonic wave generation method and propagated in the object 100 (strictly, in the base material 102 described later). Inspect.

  The object 100 of the present embodiment is an aluminum alloy base material 102 on which a plating layer 104 is formed. As a defect of the object 100, the presence or absence of the peeling of the plating layer 104 from the base material 102 is nondestructively inspected. Inspect by method. However, such a configuration is merely an example, and the ultrasonic wave generation method described in detail below can be applied to an object that does not have the plating layer 104. The nondestructive inspection method of the present embodiment is the base material 102. You may use for the inspection of defects other than the presence or absence of peeling of the plating layer 104 from. Moreover, the material of the base material 102 is not limited to the above, and may be an alloy other than an aluminum alloy or another metal.

  As a feature of the present embodiment, the object 100 includes a resin film 106 on the surface 102a of the substrate 102 on the side irradiated with the laser light. The resin film 106 is made of a polymer material having laser light impermeability and flame retardancy. As such a polymer material, triacetyl cellulose or polyvinyl chloride, which is particularly excellent in laser beam impermeability and flame retardancy, can be suitably used. However, the present invention is not limited to this, and it is possible to use other substances having laser beam impermeability and flame retardancy.

  In this embodiment, a sheet-like film (TAC film) made of triacetyl cellulose is used as the resin film 106. Then, the resin film 106 is formed on the surface 102a by adhering the film with an adhesive layer 108 formed by applying an adhesive on the surface 102a of the base material 102 (or on the back surface of the resin film 106). Yes. Thereby, the resin film 106 can be easily formed on the base material 102.

  Note that examples of the adhesive constituting the adhesive layer 108 include an acrylic adhesive, but other adhesives may be used. The thickness of the adhesive layer 108 is preferably as thin as possible. For example, the thickness may be 90 μm as in the present embodiment. This is because if the adhesive layer 108 is extremely thick, noise may occur due to reflection at the interface.

  In the present embodiment, the configuration in which the sheet-like (film) resin film 106 is bonded to the surface 102a of the base material 102 is illustrated, but a solution in which triacetyl cellulose is dissolved is applied onto the base material 102 by spraying or the like. Alternatively, the resin film 106 may be formed by other methods. Further, the range of the resin film 106 provided on the surface 102a of the substrate 102 may be provided on a part of the surface 102a as shown in FIG. 1, or the resin film 106 may be provided on the entire surface 102a.

  Then, laser light is oscillated from the Q switch pulse laser 110 toward the region where the resin film 106 is formed on the surface of the object 100 (the surface 102a of the base material 102). The oscillated laser light is condensed by the condensing lens 112 and applied to the resin film 106. Then, ablation occurs in the resin film 106, and ultrasonic waves generated by the ablation propagate in the base material 102 (inside the object 100).

  At this time, in the prior art, a laser mark appears on the surface 102a of the base material 102 due to ablation. In contrast, in the present embodiment, as described above, the resin film 106 is formed in the region irradiated with the laser light on the surface 102a. Since the resin film 106 has flame retardancy and does not burn even when ablation caused by laser irradiation occurs, the surface 102 a of the substrate 102 is protected by the resin film 106. Further, since the resin film 106 is non-transparent to the laser beam, the arrival of the laser beam to the surface 102a of the base material 102 is suppressed. Therefore, it is possible to prevent laser marks when generating ultrasonic waves using ablation.

  The resin film 106 has flexibility. For this reason, although the resin film 106 has a planar shape on the surface 102a of the base material 102 of the present embodiment, the region where the resin film 106 is formed can easily follow even if the region is a curved shape. Therefore, regardless of the shape of the object 100 (strictly speaking, the surface 102a of the base material 102), the resin film 106 and the object 100 can be satisfactorily contacted (adhered to). Therefore, it is difficult for a gap to be formed between the object 100 (the surface 102a of the base material 102) and the resin film 106, and noise resulting therefrom can be suppressed.

  Preferably, the resin film 106 has a spectral characteristic that absorbs the wavelength of the laser light oscillated from the Q switch pulse laser 110. Specifically, spectral characteristics can be imparted to the resin film 106 by mixing pigments or the like. Thereby, since the absorption rate of the laser beam in the resin film 106 can be improved, the generation efficiency of ultrasonic waves by ablation on the surface of the resin film 106 can be increased with respect to the irradiation energy of the laser beam. Further, since the laser beam is absorbed by the resin film 106, the laser beam is prevented from being transmitted through the resin film 106, so that it is possible to more reliably prevent the laser mark from being generated on the object 100.

  The details of the ultrasonic wave generation method of the present embodiment have been described above. In the nondestructive inspection method of this embodiment described below, the defect of the object 100 (peeling of the plating layer 104 from the base material 102) is inspected using the ultrasonic waves generated by the ultrasonic generation method described above. In addition, description is abbreviate | omitted about the part which overlaps with the ultrasonic wave generation method mentioned above.

  As shown in FIG. 1, a receiving device 120 is arranged on the opposite side of the object 100 from the side on which the resin film 106 is formed, in other words, on the side on which the plating layer 104 is formed. In the nondestructive inspection method according to the present embodiment, ultrasonic waves generated by the above-described ultrasonic wave generation method and propagated through the object 100 are received by the receiving device 120, and displacement measurement of the surface of the object 100 on the plating layer 104 side is performed. Do. That is, the receiving device 120 according to the present embodiment is a surface displacement measuring device, and for example, a laser interferometer can be suitably used. Then, the displacement measurement result obtained in the receiving device 120 is transmitted to the PC 130 (computer), and in the peeling determination unit 132 provided in the PC 130, peeling of the plating layer 104 from the base material 102 (defect of the object 100). Presence or absence is detected.

(Examples and Comparative Examples)
FIG. 2 is a diagram illustrating a displacement measurement result by the nondestructive inspection method of the present embodiment, and FIG. 2A is a displacement measurement result of the object 100 (example) provided with the resin film 106 of the present embodiment. FIG. 2B is a diagram illustrating a displacement measurement result of a comparative example in which the resin film 106 is not provided. In the target object 100 as an example, a 90 μm-thick resin film 106 having a spectral characteristic (SC640) that absorbs a wavelength of 640 nm or less was bonded to a base material 102 made of an aluminum alloy. A comparative example is a base material 102 made of an aluminum alloy not provided with the resin film 106. For these examples and comparative examples, a laser beam having a laser output of 60 mJ, a pulse width of 5 ns, and a wavelength of 532 nm was irradiated from the Q switch pulse laser 110.

  Comparing FIG. 2 (a) and FIG. 2 (b), they show almost the same waveform. From this, it can be understood that even when the resin film 106 is formed on the base material 102 like the object 100 of the present embodiment, no noise component is generated due to reflection at the interface between them. Moreover, when the surface of the base material 102 was observed after removing the resin film 106 from the object 100 of the example, no laser mark was generated. Therefore, the ultrasonic generation method described above is effective as a generation method of laser ultrasonic waves used in nondestructive inspection. According to the nondestructive inspection method of the present embodiment using the ultrasonic generation method, generation of laser marks due to ablation is prevented. However, it was confirmed that high accuracy can be obtained by suitably generating ultrasonic waves regardless of the material and shape of the object.

  In the above-described embodiment, the resin film 106 having the spectral characteristic (SC640) that absorbs a wavelength of 640 nm or less is exemplified, but the present invention is not limited to this. For example, when a YAG laser fundamental wave (wavelength 1064 nm) is irradiated as laser light, it is preferable to use a resin film 106 having spectral characteristics for absorbing infrared rays (or a resin film 106 with an infrared absorption layer added).

  Further, in the above-described embodiment, the case where the ultrasonic generation method of the present embodiment is applied to the nondestructive inspection method is exemplified, but the present invention is not limited to this, and the ultrasonic generation method of the present embodiment is applied to other technical fields. It is also possible to apply to.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  INDUSTRIAL APPLICABILITY The present invention can be used in an ultrasonic wave generation method for generating ultrasonic waves in an object by irradiating the surface of the object with laser light to generate ablation, and a nondestructive inspection method using the same.

DESCRIPTION OF SYMBOLS 100 ... Object, 102 ... Base material, 102a ... Surface, 104 ... Plating layer, 106 ... Resin film, 108 ... Adhesive layer, 110 ... Q switch pulse laser, 120 ... Receiver, 130 ... PC

Claims (5)

An ultrasonic generation method for generating an ultrasonic wave propagating through an object having a metal substrate,
On at least a part of the surface of the base material, a resin film made of a polymer material having laser light impermeability and flame retardancy is formed,
A method for generating ultrasonic waves, comprising: generating ultrasonic waves propagating through an object by irradiating a laser beam to a region of the surface of the object on which the resin film is formed to cause ablation.   2. The ultrasonic generation method according to claim 1, wherein the resin film is made of triacetyl cellulose or polyvinyl chloride.   The ultrasonic wave generating method according to claim 1 or 2, wherein a region of the base material on which the resin film is formed has a curved surface shape.   4. The resin film according to claim 1, wherein the resin film is a sheet-like film, and is formed by applying an adhesive on the base material and bonding the film. 5. Ultrasonic generation method. A non-destructive inspection method for inspecting defects of an object having a metal substrate by ultrasonic waves,
On at least a part of the surface of the base material, a resin film made of a polymer material having laser light impermeability and flame retardancy is formed,
Generate ultrasonic waves propagating through the object by irradiating laser light to the region where the resin film is formed on the surface of the object to cause ablation,
The receiving apparatus disposed on the opposite side of the object on which the resin film is formed receives the ultrasonic wave propagated through the object and measures the displacement of the surface on the opposite side. Non-destructive inspection method.

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