JP7721082B2 - Easy dismantling method and easily dismantlable structure - Google Patents

Description

The present invention relates to an easy-to-dismantle method and an easily dismantlable structure.

Various dismantling technologies have been proposed to promote the recycling of used products.
For example, there is an electric pulse demolition method that uses electric pulses to demolition an object in which an insulator and a conductor are bonded or joined together (see, for example, Patent Document 1). In the technology disclosed in Patent Document 1, a pair of electrodes is brought into contact with spaced apart positions on the surface of the object to be demolition, and a pulsed high voltage is applied between the electrodes to demolition the object.
There is also a known technology for dismantling solar panels by generating shock waves using a wire explosion method (see, for example, Patent Document 2). The technology disclosed in Patent Document 2 requires a small amount of energy for dismantling, allows solar panels to be dismantled at low cost, and has a small environmental impact. Furthermore, it is possible to selectively separate and recover useful substances such as silver and copper in a concentrated state, which can greatly contribute to the creation of a resource-circulating society.

Japanese Patent Application Laid-Open No. 2020-069454 Japanese Patent Application Laid-Open No. 2021-023839

In an effort to reduce the weight and improve the rigidity of automobiles, development is underway to use adhesive bonding to join components that make up an automobile body (for example, steel plates). Adhesive bonding techniques are often used in place of or in conjunction with joining techniques such as spot welding and riveting. However, there is a demand for easy disassembly of adhesively bonded parts to allow for recycling of resources. The technologies disclosed in Patent Documents 1 and 2 leave room for improvement when it comes to dismantling automobile joints, particularly joints in the body, and new technologies are needed.

According to the present invention,
A first member;
a second member; and
a joining member made of an insulating member or a semiconductor member sandwiched between the first member and the second member;
A method for easily dismantling a structure having a spacer member, at least the surface of which is conductive, provided in the joining member, comprising:
An easy disassembly method is provided in which the first member and the second member are separated by applying an electric pulse between the first member and the second member to vaporize the spacer member.
According to the present invention,
An easily dismantlable structure,
A first member;
a second member; and
a joining member made of an insulating member or a semiconductor member sandwiched between the first member and the second member;
a spacer member provided in the joining member, at least the surface of which is conductive;
The spacer member is provided with a structure that vaporizes when an electrical pulse is applied between the first member and the second member.

The present invention provides a technology that facilitates dismantling of a structure in which a first member and a second member are joined with a joining member made of an insulating or semiconductor material.

FIG. 1 is a cross-sectional view showing a structure according to an embodiment. 1 is a circuit diagram of an electric pulse generator according to an embodiment. FIG. 10 is a diagram showing an estimated model of the separation mechanism of a metal sphere-added bonded body by an electric pulse according to an embodiment. FIG. 10 is a diagram showing an estimated model of the separation mechanism of a metal sphere-added bonded body by an electric pulse according to an embodiment. 1 is a flowchart showing a procedure for dismantling a structure according to an embodiment by applying an electric pulse to the structure. FIG. 1 is a perspective view showing a structure used in an electric pulse experiment according to Example 1 of the embodiment. FIG. 10 is a diagram showing an example of the arrangement of metal balls and alumina balls at the joint portion of the structure used in the electric pulse experiment according to Example 1 of the embodiment. 10 is an image of an adhesive sample sandwiched between electrodes of an electric pulse device according to Example 1 of the embodiment. FIG. 2 is a schematic diagram of a visualization optical system and an imaging system according to Example 1 of the embodiment. 1 is a graph showing a voltage waveform between capacitors measured when an electric pulse is applied and a current waveform passed through an adhesive sample according to Example 1 of the embodiment. 10 is a visualized image of the discharge position and separation phenomenon of the sample when an electric pulse is applied to samples 1 to 3 of the bonded body samples bonded with an adhesive containing metal balls according to Example 1 of the embodiment. FIG. 10 is a diagram showing an image of a sample after application of an electric pulse according to Example 1 of the embodiment. 10A and 10B are diagrams showing examples of models of structures used in simulations 1 to 3 according to Example 2 of the embodiment. FIG. 10 is a diagram showing an example of an input waveform of a current source as an electrical pulse used in simulations 1 to 3 according to Example 2 of the embodiment. FIG. 10 is a diagram showing conditions used in simulations 1 to 3 according to Example 2 of the embodiment. FIG. 10 is a diagram showing the results of simulation 1 according to Example 2 of the embodiment, illustrating an enlarged view of the temperature distribution of the spacer member and its surrounding area 19 μs after the application of the electric pulse when the capacitor charging energy Ec=30 J. 10 is a graph showing the results of Simulation 1 according to Example 2 of the embodiment, illustrating temperature changes of the first contact portion and the second contact portion under three conditions of capacitor charging energy Ec=10 J, 20 J, and 30 J. 10 is a graph showing the results of Simulation 1 according to Example 2 of the embodiment, illustrating temperature changes at the center position of the spacer member under three conditions of capacitor charging energy Ec=10 J, 20 J, and 30 J. 10 is a graph showing the results of Simulation 2 according to Example 2 of the embodiment, illustrating the temperature change of the first contact portion, which is the contact portion between the spacer member and the first member. 10 is a graph showing the results of Simulation 2 according to Example 2 of the embodiment, illustrating the temperature change at the center position (center of the sphere) of the spacer member. FIG. 10 is a diagram showing the results of Simulation 2 according to Example 2 of the embodiment, illustrating an enlarged view of the temperature distribution of the spacer member and its surrounding area at the end of application of an electric pulse. FIG. 10 is a diagram showing the results of Simulation 2 according to Example 2 of the embodiment, illustrating an enlarged view of the temperature distribution of the spacer member and its surrounding area at the end of application of an electric pulse. FIG. 10 is a diagram showing the results of Simulation 2 according to Example 2 of the embodiment, illustrating an enlarged view of the temperature distribution of the spacer member and its surrounding area at the end of application of an electric pulse. 10 is a graph showing the results of Simulation 3 according to Example 2 of the embodiment, illustrating temperature changes in a first contact portion, which is a contact portion between the spacer member and the first member. 10 is a graph showing the results of Simulation 3 according to Example 2 of the embodiment, illustrating temperature changes at the center position of the spacer member. FIG. 10 is a diagram showing the results of Simulation 3 according to Example 2 of the embodiment, illustrating an enlarged view of the temperature distribution of the spacer member and its surrounding area at the end of application of an electric pulse. FIG. 10 is a diagram showing the results of Simulation 3 according to Example 2 of the embodiment, illustrating an enlarged view of the temperature distribution of the spacer member and its surrounding area at the end of application of an electric pulse.

<Overview>
An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a structure 10 (also referred to as a "bonded body") according to this embodiment. The easy dismantling method of this embodiment is a method for dismantling the structure 10 of FIG. 1. An example of the structure 10 is a structure in which steel plates in the body of a vehicle (automobile or train) are bonded together with an adhesive. The structure 10 is not limited to a vehicle, and may also be, for example, an aircraft or ship, or even a home appliance such as a refrigerator or washing machine.

The structure 10 has a first member 21, a second member 22, a joining member 30 provided between the first member 21 and the second member 22, and a spacer member 40 provided in the joining member 30.
The joining member 30 is provided so as to be sandwiched between the first member 21 and the second member 22 , and joins the first member 21 and the second member 22 together.
In the region where the joining member 30 is provided, a spacer member 40 having at least a conductive surface is provided.
A high-voltage electric pulse is applied between the first member 21 and the second member 22 to explosively vaporize the spacer member 40, thereby separating the first member 21 and the second member 22.
This will be explained in detail below.

<First member 21 and second member 22>
Both the first member 21 and the second member 22 are made of a conductor.
The conductors of the first member 21 and the second member 22 are formed of, for example, a metal, a metal oxide, or a composite containing metal particles.
More specifically, the conductors of the first member 21 and the second member 22 may be, for example, an iron alloy such as a steel plate, or aluminum or an aluminum alloy. The metal particle-containing composite may be a member formed by mixing and integrating particles of a metal such as iron, copper, or aluminum or an alloy of these metals with particles of a resin such as epoxy resin, polyimide, phenol melamine resin, urea unsaturated polyester resin, or alkyd polyurethane resin.
The first member 21 and the second member 22 may be made of different conductors (materials). For example, the first member 21 may be made of steel, and the second member 22 may be made of an aluminum alloy plate.

There are no particular limitations on the thickness of the first member 21 and the second member 22, provided that they are thick enough to provide proper electrical conduction via the spacer member 40 when an electric pulse is applied.
The thicknesses of the first member 21 and the second member 22 may be the same or different.
The lower limit of each thickness can be, for example, 0.1 mm or more, preferably 0.2 mm or more, and more preferably 0.3 mm or more. By setting the thickness of the first member 21 and the second member 22 to the above-mentioned lower limit or more, the rigidity (strength) of the structure 10 can be ensured.
The upper limit of the thickness can be set to, for example, 20 mm or less, preferably 15 mm or less, and more preferably 10 mm or less.

Assuming that proper conduction occurs when an electric pulse is applied, the electrical resistivity (20°C) of the conductors of the first member 21 and the second member 22 is 1.5 x ^10-8 Ω·m or more and 1 x ¹⁰⁴ Ω·m or less. There is no particular lower limit to the electrical resistivity, but a realistic value can be set to the above value or more.
The upper limit of the electrical resistivity depends on the voltage and current values of the electric pulse, but from the viewpoint of suppressing the input energy, it is 1×10 ⁴ Ω·m or less, preferably 5×10 ³ Ω·m or less, and more preferably 1×10 ³ Ω·m or less.

The surfaces of the first member 21 and the second member 22 may be coated with an insulating layer or the like, but when an electric pulse is applied, the electric pulse must be conducted between the first member 21 and the second member 22 via the spacer member 40.

<Joint member 30>
The joining member 30 is a member for joining the first member 21 and the second member 22, and is used in place of or in combination with joining techniques such as welding, riveting, and bolts.

The joining member 30 is made of an insulating material or a semiconductor material. For example, structural adhesive can be used for the joining member 30, which is made of a thermosetting resin.

The thermosetting resin includes one or more resins selected from the group consisting of epoxy resins, phenolic resins, and polyimide resins. Among these resins, epoxy resins are preferred in terms of heat resistance.
The thermosetting resin further contains inorganic particles (excluding the spacer members 40).
Examples of inorganic particles include silica and alumina.
The adhesive may be comprised of a thermoplastic resin instead of a thermosetting resin.

The thickness of the joining member 30, i.e., the distance L between the first member 21 and the second member 22, is, for example, 0.05 mm or more and 20 mm or less. The upper limit of the distance L is preferably 1 mm or less, and more preferably 0.4 mm or less. This distance L is the same as the thickness of the spacer member 40 in the joining direction between the first member 21 and the second member 22 (here, the diameter of the spacer member 40).

<Spacer member 40>
At least the surface of the spacer member 40 is conductive and is in contact with the first member 21 and the second member 22. When an electric pulse is applied, the spacer member 40 serves as a conduction path for the electric pulse. In other words, when an electric pulse is applied, a high current is concentrated in the spacer member 40 by the electric pulse and does not flow into the surrounding joining member 30.

The spacer member 40 has a curved shape, and the curved surface is in direct contact with the first member 21 or the second member 22 or in contact with the first member 21 or the second member 22, or in contact with the first member 21 or the second member 22 via a thin layer. The upper end portion of the spacer member 40 (hereinafter referred to as the "first contact portion 51") contacts the inner surface 21a of the first member 21. The lower end portion of the spacer member 40 (hereinafter referred to as the "second contact portion 52") contacts the inner surface 22a of the second member 22.

The first contact portion 51 and the second contact portion 52 may be in close proximity to the first member 21 and the second member 22, respectively, without being in strict contact with them. That is, the joining member 30 may be provided as a thin layer with a slight thickness between the first contact portion 51 and the inner surface 21a of the first member 21, and between the second contact portion 52 and the inner surface 22a of the second member 22. The thickness is set so that, when an electric pulse is applied, dielectric breakdown occurs, allowing current to flow between the first member 21 and the spacer member 40, and between the second member 22 and the spacer member 40. The thickness can be, for example, 100 μm or less.

In other words, the thickness D of the spacer member 40 (or the diameter if the spacer member 40 is spherical) can be approximately the same as the distance L between the first member 21 and the second member 22, which is the thickness of the joining member 30. That is, the thickness D of the spacer member 40 is, for example, 0.05 mm or more and 20 mm or less. The upper limit of the thickness D is preferably 1 mm or less, and more preferably 0.4 mm or less.

The shape of the spacer member 40 is not particularly limited, but is preferably such that when placed between the first member 21 and the second member 22, the contact portions (first contact portion 51, second contact portion 52) with the first member 21 or the second member 22 are in substantial point contact. Such a shape may be a curved shape, preferably a spherical, oval, or flake-like shape. A spherical shape, which does not require orientation adjustment, is particularly preferable. In the case of a spherical spacer member 40 such as a metal sphere, point contact can be achieved regardless of the orientation of the spacer member 40. The spacer member 40 may also be in the form of a polyhedron in which the contact area of the contact portions (first contact portion 51, second contact portion 52) is minimized, or a cone in which one of the contact portions (first contact portion 51, second contact portion 52) is in substantial point contact.

The contact resistance at the contact points (first contact portion 51, second contact portion 52) between the spacer member 40 and the first member 21 or second member 22 is higher than the resistance value of the spacer member 40. Because the first contact portion 51 and the second contact portion 52 are in point contact (or close proximity), they form high electrical resistance areas that serve as the path for the electric pulse. Therefore, when an electric pulse is applied, the first contact portion 51 and the second contact portion 52 generate Joule heat locally and adiabatically. As a result, the spacer member 40 rises to its vaporization temperature and vaporizes explosively.

The conductor of the spacer member 40 is made of iron, nickel, cobalt, aluminum, copper, or an alloy containing these. The spacer member 40 can be, for example, a stainless steel ball. Furthermore, the spacer member 40 does not need to be entirely made of metal; it can also be a ceramic ball whose surface is coated with the above-mentioned conductor.

<Electric pulse>
The characteristics of the electric pulse applied between the first member 21 and the second member 22 are as follows.
The applied voltage is 1 kV or more and 1000 kV or less. The lower limit of the applied voltage is preferably 5 kV or more, and more preferably 10 kV or more. By setting the lower limit of the applied voltage within the above range, the spacer member 40 can be raised to its vaporization temperature and explosively vaporized. The upper limit of the applied voltage is preferably 500 kV or less, and more preferably 100 kV or less. By setting the upper limit of the applied voltage within the above range, the spacer member 40 can be reliably vaporized and excessive energy input can be avoided.

The pulse width is 1 ns or more and 100 ms or less. The lower limit of the pulse width is preferably 2 ns or more, and more preferably 5 ns or more. By setting the lower limit of the pulse width within the above range, it is possible to input energy to raise the temperature of the spacer member 40 to the vaporization temperature. The upper limit of the pulse width is preferably 1 ms or less, and more preferably 100 μs or less. By setting the upper limit of the pulse width within the above range, it is possible to raise the temperature of the spacer member 40 instantaneously, in other words, adiabatically, to the vaporization temperature.
The electric pulse may have any waveform, such as a sine wave, a unipolar pulse, a bipolar pulse, or a triangular wave, as long as it satisfies the above conditions and can instantaneously vaporize the spacer member 40 .

Figure 2 shows an example of a device that generates an electrical pulse (hereinafter referred to as the electrical pulse device 100), showing a basic circuit example.

The electric pulse device 100 in Figure 2 generates an electric pulse having the above-described characteristics and applies it between the first member 21 and the second member 22. The electric pulse device 100 in Figure 2 is composed of a charging circuit and a discharging circuit, and applies an electric pulse to the structure 10 (labeled "LOAD" in the figure) by switching the charge stored in a capacitor connected to a 5 kV DC power supply. The electric pulse device 100 also has the circuit configuration used in the examples, and the specific configuration will be described later in the examples.

<Estimated model of the separation mechanism of adhesive bodies containing metal spheres due to electric pulses>
An estimated model of the separation mechanism of a metal-sphere-added bonded body using an electric pulse will be described with reference to Figures 3 and 4. Figures 3 and 4 are cross-sectional views illustrating the procedure (model) for dismantling a structure 10 by applying an electric pulse to the structure 10. The model shown in this procedure is an estimated model of the separation mechanism of a metal-sphere-added bonded body (a bonded body using a metal-sphere-added adhesive) using an electric pulse, and was estimated from the experimental results of Example 1, which will be described later.

FIG. 3 shows a model in which a metal ball (spacer member 40) and a base material (first member 21, second member 22) are in contact with each other.
3A, the spacer member 40 is in contact with the first member 21 at a first contact portion 51 and is in contact with the second member 22 at a second contact portion 52. A joining member 30 is provided around the spacer member 40.
As shown in FIG. 3B, when an electric pulse is applied between the first member 21 and the second member 22, a pulse current 55 flows on the surface of the spacer member 40 (metal sphere).
As a result, as shown in Fig. 3(c), the spacer members 40 (metal spheres) are turned into plasma and vaporized by Joule heat generated by the current flow. It is believed that the high temperature caused by this plasma also vaporizes the bonding members 30 (adhesive) around the spacer members 40. This vaporization is accompanied by a rapid volume expansion, and it is believed that this gas expansion destroys the bonding members 30 (adhesive) and separates the structure 10 (the bonded state between the first member 21 and the second member 22) as shown in Fig. 3(d).

4 shows a model in which the metal ball (spacer member 40) and the base material (first member 21, second member 22) are not in contact with each other. In this case, as shown in FIG. 4(a), the first member 21 and the spacer member 40 are not in contact with each other, and the second member 22 and the spacer member 40 are in contact with each other.
When the metal balls (spacer members 40) and the base materials (first member 21, second member 22) are not in contact with each other, and the breakdown voltage Vdb [kV] of the adhesive (joining members 30) between the base materials and the metal balls is lower than the breakdown voltage Vda [kV] of the atmosphere between the base materials (i.e., between the first member 21 and the second member 22), as shown in Figures 4(b) to (d), the electric pulse causes breakdown of the adhesive (joining members 30), current flows through the metal balls (spacer members 40), and a separation mechanism similar to that shown in Figure 3 is thought to occur.
The breakdown voltage is calculated as Vda = Eala and Vdb = Eblb using the breakdown strengths Ea and Eb [kV/mm] of the air and adhesive and the distances la and lb [mm] between the base materials and between the base material and the metal ball.
4(e) and (f), when the metal balls (spacer members 40) are not in contact with the base materials (first member 21, second member 22), the distance between the base materials and the metal balls is long, and Eala<Eblb (Vda<Vdb), dielectric breakdown of the adhesive (joining members 30) does not occur when an electric pulse is applied, but dielectric breakdown occurs in the atmosphere along the surface of the adhesive from the edge 21c of the upper base material (first member 21), and creeping discharge in the atmosphere occurs between the upper and lower base materials (first member 21, second member 22). This creeping discharge only creates discharge marks on the base materials, and it is presumed that, as can be seen in FIG. 9(c) of Example 1 described later, the adhesive body did not separate under these electric pulse conditions.

<Method for dismantling the structure 10>
5 is a flowchart of a method for dismantling the structure 10 (metal sphere-added bonded body). The method for dismantling the structure 10 will be described with reference to this flowchart.
S10: Pulse application device setting step The electric pulses to be applied to the structure 10 to be dismantled are set in the electric pulse device 100 shown in Fig. 2. For example, the voltage, pulse width, number of pulses, etc. are set.

S12: Pulse application execution step After the setting is completed (S10), as shown in FIG. 4(a), the electrodes 61 of the electric pulse application device are brought into contact with the outer surfaces 21b, 22b of the first member 21 and the second member 22 of the structure 10, and the set electric pulse is applied.

S14: Vaporization and Separation Step When an electric pulse is applied, a high current due to the electric pulse flows through a path formed by the first member 21, the spacer member 40, and the second member 22. On the other hand, no current flows through the joining member 30 around the spacer member 40. At this time, the first contact portion 51 and the second contact portion 52 locally and adiabatically generate Joule heat. As a result, they are explosively vaporized as shown in FIG. 3( c) and FIG. 4(c). The explosive force destroys the joining member 30, and the first member 21 and the joining member 30, and the second member 22 and the joining member 30 are separated. In other words, the first member 21 and the second member 22 are separated.

As described above, according to this embodiment, an electric pulse is applied to the first member 21 and the second member 22 of the structure 10, a high current is instantaneously introduced to the spacer member 40 at the intended position, and adiabatic temperature rise is caused particularly at the first contact portion 51 and the second contact portion 52 of the spacer member 40, causing a vaporization explosion of the spacer member 40. As a result, the joining member 30 is destroyed at the intended position (i.e., the position of the spacer member 40), and the first member 21 and the second member 22 are separated.
By using this technology, it is possible to improve the ease of separation and dismantling of products having the above-described structure 10, thereby increasing the recycling rate. Furthermore, the electric pulse is instantaneous and requires little input energy. Furthermore, the device itself can be realized with a standard circuit configuration. Therefore, dismantling can be performed in a short time with low energy, thereby reducing dismantling costs. Furthermore, the electric pulse applied between the first member 21 and the second member 22 flows through the spacer member 40, regardless of the position of the electrode 61. In other words, since the position where the electrode 61 is to be contacted is not substantially limited, there is no need to specify the contact position of the electrode 61, which eliminates the need for specific work.

The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples as long as the gist of the invention is not exceeded.
In the following, as Example 1, an experiment was conducted in which an adhesive sample corresponding to the structure 10 was actually used and an electric pulse was applied to separate the adhesive sample. As Example 2, suitable conditions for separation by applying an electric pulse were calculated by computer simulation.

[Example 1]
<Electric pulse application experiment>
<Adhesive sample>
FIG. 6A is a schematic diagram of a structure 10 (bonded body sample) used in an electric pulse application experiment. Here, it is shown as a perspective view. FIG. 6B is a diagram showing an example of the arrangement of metal balls (spacer members 40) and alumina balls 70 at the bonded portion of the structure 10 used in the electric pulse application experiment. Here, it is shown as a cross-sectional view of the bonded surface. As the bonded body sample, a structure 10 was used in which a first member 21 and a second member 22 were bonded with a bonding member 30 via a spacer member 40. The bonded body sample was prepared with reference to the shape of a sample for testing the tensile shear strength of adhesives specified in JIS K6850.
The materials (steel plates) and dimensions of the first member 21 and the second member 22 are as follows:
Materials of the first member 21 and the second member 22: SUS304
Dimensions: 100mm x 25mm x 0.5mm
Area of the joint portion (joint member 30): 25 mm x 25 mm
Thickness of the joint (joining member 30): 0.3 mm
Material of the joining member 30: One-component curing epoxy resin adhesive (EP138, Cemedine)
As shown in FIG. 6B, the area (i.e., the bonding area) of the bonded portion (bonding member 30) was a square with sides of 25 mm. One conductive spacer member 40 (0.3 mm diameter, SUS440C) was placed at the center of the bonding surface, and four insulating alumina spheres 70 (0.3 mm diameter) were placed around it, and the adhesive was cured. The curing conditions were 120°C for 30 minutes. To investigate the effect of the metal spheres added to the adhesive on adhesive separation due to electric pulses, three samples were prepared.

<Electric pulse generator (circuit) and electric pulse conditions>
The electric pulse was generated using the electric pulse device 100 described above in Fig. 2 and applied to the structure 10. Fig. 6C is an image of the adhesive sample (structure 10) sandwiched between the electrodes 61 (electrode (+) 61a, electrode (-) 61b) of the electric pulse device 100.
The electric pulse device 100 is composed of a charging circuit and a discharging circuit. In the charging circuit, a DC power supply (152 A, manufactured by TDK-Lambda) is charged to a charging voltage of 5 kV using a controller, and three capacitors (FL40W804KWFAAA, manufactured by Shizuki Electric Co., Inc.) are connected in parallel with a capacitance of C = 2.4 μF. The discharge circuit is switched on by switching a mechanical switch.

As shown in Figure 6C, both ends of the bonded sample (structure 10) were sandwiched between electrodes 61 (electrode (+) 61a, electrode (-) 61b) in a discharge circuit (electric pulse device 100 in Figure 2) and secured with bolts, and an electric pulse was applied to the bonded sample. The distance between the electrodes was 9 cm. The discharge circuit was an RLC circuit formed by the total resistance R of the discharge circuit, the inductance L of the discharge circuit, and the capacitor capacitance C. The voltage across the capacitor when the electric pulse was applied was measured with a voltmeter (HV-P60A, manufactured by Iwasaki Electric Co., Ltd.), and the current flowing through the sample was measured with an ammeter (Model 110A-EOR, manufactured by Peason Electronics). The measured voltage and current were recorded on an oscilloscope (HDO4104A, manufactured by TELEDYNE LECROY).

<Method for visualizing the electric pulse phenomenon on adhesive samples>
In this example, the shadowgraphy method, a visualization measurement method, was used to visualize the location of discharge occurrence in the adhesive sample and the adhesive separation phenomenon upon application of an electric pulse. These visualized phenomena were then photographed using a high-speed video camera (HPV-X2, manufactured by Shimadzu Corporation). Figure 7 shows a schematic diagram of the visualization optical system and imaging system. The optical system's light source was a pulsed diode laser (Cavilux Smart, manufactured by Cavitor Ltd.) with a wavelength of 640 nm and an output of 500 W, and the pulse width was set to 20 ns. To achieve clear visualization while suppressing discharge emission, an ND filter (product name: ND400) was attached to the camera lens of the high-speed video camera. The focal length of the camera lens was 300 mm, and the aperture value was 3.5. The high-speed video camera's imaging speed was 2.0 x 10 ⁵ frames/sec, the imaging interval was 5.0 μs, and the exposure time was 200 ns/frame. As shown in Figure 8, which will be described later, a TTL signal was input to a high-speed video camera via a function generator, triggered by the rising edge of the voltage in the voltage-current waveform measured by the oscilloscope, and recording was started. A synchronization signal was output from this camera to the laser light source, allowing visualization and recording to be synchronized between the application of an electric pulse to the adhesive sample between the electrodes, the emission of the laser light source, and the start of recording by the high-speed video camera.

<Impedance measurement>
The electrical properties of the sample were measured using impedance measurement (PSM1750, manufactured by Iwasaki Electric Co., Ltd.) at a measurement frequency of 1 kHz and an applied voltage of 10 V. Before the electric pulse application experiment, the sample was clamped with Kelvin leads at positions 1 cm from both ends, and the voltage was applied in the same direction as during the electric pulse application experiment.

<Experimental Results>
<Voltage and current waveforms when an electric pulse is applied>
Figure 8 shows the voltage waveform between the capacitors measured when an electric pulse was applied and the current waveform passed through the adhesive sample. As can be seen from Figure 8, the voltage and current in this experiment exhibited damped oscillation. This damped oscillation is thought to have occurred because ^R2 < 4LC in the discharge circuit of the electric pulse device 100 in Figure 2 in this experiment. In Figure 8, the maximum voltage was 5.0 kV, which is the charging voltage, and the maximum current was 3.8 kA.

<Discharge position in adhesive sample and adhesive separation phenomenon when electric pulse is applied>
Figure 9 shows visualized images of the discharge location and sample separation phenomenon upon application of an electric pulse for Samples 1 to 3, which were bonded with adhesive containing metal spheres. Figure 10 shows images of Samples 1 to 3 after application of an electric pulse. Figures 9(a) and 10(a) correspond to Sample 1, Figures 9(b) and 10(b) correspond to Sample 2, and Figures 9(c) and 10(c) correspond to Sample 3. As shown in Figures 9(a) and 9(b), discharge light emission was observed at the location of the metal spheres in the adhesive for Samples 1 and 2. This demonstrates that adding metal spheres to the adhesive can apply an electric pulse to the metal spheres and induce a discharge within the adhesive. Furthermore, as shown in Figures 9(a) and 9(b), gas expansion was observed within the adhesive upon application of an electric pulse. This gas expansion accompanied separation of the bonded structure.

In Figures 10(a) and (b), the adhesive surface of the separated bonded body after the electric pulse had undergone cohesive failure, with no remaining metal balls, and discharge marks were observed where the metal balls had been added. The surface of the base steel plate was exposed in these discharge marks, creating crater-like depressions in the steel plate (depressions 51a and 52a in Figures 3 and 4). It was also observed that part of the fractured surface of the adhesive had turned black. These observations suggest that the application of the electric pulse turned the metal balls into plasma, vaporized them, and expanded them, and that the high temperature of this plasma also vaporized the adhesive around the metal balls. Therefore, it is surmised that the bonded body separated due to the gas expansion and adhesive vaporization that accompanied the plasma transformation of the metal balls in the adhesive caused by the electric pulse.

On the other hand, in sample 3, as can be seen in Figure 9(c), discharge occurred at the edge of the steel plate connected to the negative and positive electrodes, and the adhesive did not separate. In Figure 10(c), discharge marks were observed at the edge of the steel plate after the electric pulse, but no destruction of the adhesive was confirmed. If the metal balls in the adhesive were not in contact with the base steel plate, the electric pulse would not be applied to the metal balls, and it is thought that discharge due to the electric pulse would occur not within the adhesive but at the edge of the steel plate where the electric field is concentrated. Therefore, it is inferred that in sample 3, the metal balls added to the adhesive were not in contact with the base material.

<Consideration of the relationship between the impedance value of the adhesive body and the discharge position>
To evaluate the induction of discharges within the adhesive when an electric pulse is applied by adding metal spheres to the adhesive, we considered the relationship between the impedance value of the adhesive sample before the electric pulse and the discharge position. Table 1 shows the measurement results of the impedance value Z of each sample at a frequency of 1 kHz. For sample 1, Z = 8.13 x ^10-1 Ω, an impedance value more than ¹⁰⁴ times smaller than that of the other two samples, suggesting that the base steel plate and the metal spheres in the adhesive are in contact and in a state of conduction. On the other hand, for samples 2 and 3, Z = 1.46 x ¹⁰⁴ and 1.70 x ¹⁰⁴ Ω, respectively, suggesting that the metal spheres are not in contact with the base material.

When the metal ball and base material are in contact, an electric pulse is applied to the metal ball, which is thought to cause a discharge within the adhesive at the position of the metal ball. On the other hand, in Sample 2, it is presumed that the metal ball and base material are not in contact, but in Figure 9(b), a discharge occurred at the position of the metal ball within the adhesive. When the metal ball and base material are not in contact, adhesive fills the space between them. Here, if the breakdown voltage of the adhesive between the metal ball and base material is lower than the voltage that causes breakdown in the air surrounding the adhesive filled between the two base materials, it is presumed that the electric pulse causes dielectric breakdown in the adhesive between the metal ball and base material, and then the electric pulse is applied to the metal ball, causing a discharge within the adhesive.

[Example 2]
<Simulation>
In Example 2, the conditions for the electric pulse that vaporizes (explodes) the spacer member 40 (SUS304 metal balls) were confirmed using a computer-based current and heat transfer simulation, depending on the physical properties (resistance, diameter, material) of the spacer member 40 (metal balls).
Specifically, the following items (1) to (3) were confirmed.
(1) Simulation 1: Investigation of Input Energy Dependence The energy of the applied electric pulse (capacitor charging energy Ec) was changed to check the temperature change of the spacer member 40.
(2) Simulation 2: Investigation of Pulse Width Dependence The charge amount was kept constant (0.1 C (coulomb)), and the pulse width and current were changed to check the temperature change of the spacer member 40.
(3) Simulation 3: Investigation of Sphere Radius Dependence The pulse current waveform was kept constant (1 kA, 100 μs), and the sphere radius was changed to check the temperature change of the spacer member 40.
As temperature changes, (a) the temperature of the first contact portion 51 and the second contact portion 52 of the spacer member 40 (metal ball) and (b) the temperature of the center portion of the spacer member 40 were calculated, and it was confirmed whether or not they exceeded the boiling point.

Figure 11 shows an example model of the structure 10 used in simulations 1 to 3, showing the geometry and boundary conditions. The model was a solid obtained by rotating the region shown in Figure 11 around an axis. In other words, a model was used in which a SUS304 metal sphere (corresponding to spacer member 40) was sandwiched between two SUS304 cylinders (corresponding to first member 21 and second member 22).

12 shows an example of an input waveform of a current source as an electric pulse, where the current value is 1.0 kA and the pulse width is 10×10 ⁻⁵ s.
13 shows the conditions used in Simulations 1 to 3. Here, the physical property values and constitutive equations of SUS304 are shown.

<Simulation results>
The simulation results are shown below.
(1) Results of Simulation 1 (Investigation of Input Energy Dependence) The energy of the applied electric pulse (capacitor charging energy Ec) was 10J, 20J, and 30J.
The spacer member 40 is a SUS304 metal ball having a diameter of 0.3 mm.
The results of Simulation 1 are shown in FIGS.
FIG. 14 is an enlarged view showing the temperature distribution of the spacer member 40 and its surrounding area when the capacitor charging energy Ec=30 J and 19 μs has elapsed since the application of the electric pulse.
FIG. 15 is a graph showing the temperature changes of the first contact portion 51 and the second contact portion 52 under three conditions of capacitor charging energy Ec=10 J, 20 J, and 30 J.
FIG. 16 is a graph showing the temperature change at the center position 53 (center of the metal ball) of the spacer member 40 under three conditions of capacitor charging energy Ec=10 J, 20 J, and 30 J.

It was confirmed that the first contact portion 51 (or the second contact portion 52), which is the contact portion between the first member 21 (or the second member 22) and the spacer member 40, has a high electrical resistance value and the temperature rises particularly.
It was confirmed that under all three conditions of capacitor charging energy Ec = 10 J, 20 J, and 30 J, the temperature of the first contact portion 51 (or the second contact portion 52) was sufficiently higher than the boiling point of 3134 K of iron, the main component of the spacer member 40 (SUS304).
Under two conditions of capacitor charging energy Ec = 20 J and 30 J, it was confirmed that 5 μs after the application of the electric pulse, the temperature at the center of the spacer member 40 was sufficiently higher than the boiling point of 3134 K of the main component, iron, and the spacer member 40 explosively vaporized.

(2) Results of Simulation 2 (Investigation of Pulse Width Dependence) In Simulation 2, the charge amount was kept constant (0.1 C (coulomb)), and the pulse width and current were varied to confirm the temperature change of the spacer member 40. The following seven combinations of current and pulse width were used.
1: 100kA, 1μs
2: 10kA, 10μs
3: 1kA, 100μs
4: 100A, 1ms
5: 10A, 10ms
6:1A, 100ms
7: 0.1 A, 1 s
Hereinafter, for the sake of convenience, the above combinations will be referred to as "current/pulse width pairs 1 to 7." (1) to (7) in the graphs of Figures 17 and 18 correspond to current/pulse width pairs 1 to 7. (8) in the figures indicates the boiling point of iron.

The results of Simulation 2 are shown in FIGS.
FIG. 17 is a graph showing the temperature change of the first contact portion 51 (or the second contact portion 52) which is the contact portion between the spacer member 40 and the first member 21 (or the second member 22).
FIG. 18 is a graph showing the temperature change at the center position (center of the sphere) of the spacer member 40.
19 to 21 are enlarged views showing the temperature distribution of the spacer member 40 and its surrounding area at the end of the application of the electric pulse. Figures 19(a) to 19(c) show the temperature distribution of current/pulse width sets 1 to 3, Figures 20(a) and 20(b) show the temperature distribution of current/pulse width sets 4 and 5, and Figures 21(a) and 21(b) show the temperature distribution of current/pulse width sets 6 and 7.

As can be seen from the results in Figures 17 to 21, the shorter the pulse width, the higher the temperature tended to be. Furthermore, it was confirmed that when the charge amount was 0.1 C and the pulse width was 1 ms or less, the temperature at the center of the spacer member 40 (center of the sphere) exceeded the boiling point of iron.

(3) Results of Simulation 3 (Investigation of Dependence on Sphere Radius) In Simulation 3, the pulse current waveform was kept constant (1 kA, 100 μs), and the sphere radius of the spacer member 40 was changed to check the temperature change of the spacer member 40.
There are 10 types of sphere radius r in the range of 0.05 mm to 0.5 mm in increments of 0.05 mm.

The results of Simulation 3 are shown in FIGS.
FIG. 22 is a graph showing the temperature change of the first contact portion 51 (or the second contact portion 52) which is the contact portion between the spacer member 40 and the first member 21 (or the second member 22).
FIG. 23 is a graph showing the temperature change at the center position (center of the sphere) of the spacer member 40.
In the graphs of FIGS. 22 and 23, (1) to (10) correspond to the above-mentioned 10 types of sphere radii (ranging from 0.05 mm to 0.5 mm in 0.05 mm increments) in order from smallest to largest.
(11) in the figure indicates the boiling point of iron.
24 and 25 are enlarged views showing the temperature distribution of the spacer member 40 and its surrounding area at the end of the application of the electric pulse. Figures 24(a) to 24(c) show the temperature distribution when the radius r is 0.1 mm, 0.2 mm, and 0.3 mm, and Figures 25(a) and 24(b) show the temperature distribution when the radius r is 0.4 mm and 0.5 mm.

As can be seen from the results in Figures 22 to 25, it was confirmed that the central temperature tends to decrease as the spherical radius of the spacer member 40 increases. Furthermore, it was confirmed that when the spherical radius r of the spacer member 40 is 0.2 mm or less (diameter 0.4 mm or less), i.e., when the distance between the first member 21 and the second member 22 is 0.4 mm or less, the boiling point of iron, the main component of the spacer member 40, is exceeded.

As described above, according to Examples 1 and 2, in a structure 10 in which two steel plates (first member 21 and second member 22) are joined with a joining member 30, if small metal balls (spacer members 40) are placed inside the joining member 30 in advance so that their upper and lower ends are in contact with the steel plates and bonded together, a high-voltage pulse is applied to both steel plates during dismantling and separation, causing the spacer members 40 to explosively vaporize, allowing the structure 10 to be dismantled in a short period of time and with low input energy.

REFERENCE SIGNS LIST 10 Structure 21 First member 22 Second member 30 Joining member 40 Spacer member 51 First contact portion 52 Second contact portion 70 Aluminum ball 100 Electric pulse device

Claims (28)

A first member;
a second member; and
a joining member made of an insulating member or a semiconductor member sandwiched between the first member and the second member;
A method for easily dismantling a structure having a spacer member, at least the surface of which is conductive, provided in the joining member, comprising:
An easy disassembly method for separating the first member and the second member by applying an electric pulse between the first member and the second member to vaporize the spacer member. the spacer member is in contact with the first member or the second member,
The easy disassembly method according to claim 1 , wherein a contact resistance at a contact point between the spacer member and the first member or the second member is higher than a resistance value of the spacer member. The easy-disassembly method described in claim 1 or 2, wherein the first member and the second member are both made of a conductor. The easy-disassembly method described in claim 3, wherein the conductor is formed from a metal, a metal oxide, or a composite containing metal particles. 5. The method for easily dismantling according to claim 3, wherein the electrical resistivity of the conductor at 20° C. is 1.5×10 ⁻⁸ Ω·m or more and 1×10 ⁴ Ω·m or less. The easy-disassembly method described in any one of claims 1 to 5, wherein the conductor of the spacer member is formed from metal. The easy-disassembly method described in claim 6, wherein the spacer member is made of iron, nickel, cobalt, aluminum, copper, or an alloy containing any of these. The easy-disassembly method described in any one of claims 1 to 7, wherein the spacer member has a spherical, elliptical, or flake-like shape. The easy-disassembly method described in any one of claims 1 to 8, wherein the spacer member has a shape with a curved surface, and the curved surface is in direct contact with the first or second member or in contact with the first or second member via a thin layer having a thickness of 100 μm or less. The distance between the first member and the second member is L,
10. The easy-disassembly method according to claim 1, wherein when the length of the spacer member in the joining direction between the first member and the second member is D, the length D is equal to the distance L. The easy-disassembly method described in claim 10, wherein the length D is 0.05 mm or more and 20 mm or less. The easy-disassembly method described in any one of claims 1 to 11, wherein the joining member is made of a thermosetting resin. The easy-disassembly method described in claim 12, wherein the thermosetting resin includes one or more resins selected from the group consisting of epoxy resin, phenolic resin, and polyimide resin. The easy-disassembly method described in claim 13, wherein the thermosetting resin further contains inorganic particles (excluding the spacer members). The easy-disassembly method described in any one of claims 1 to 14, wherein the applied voltage of the electric pulse is 1 kV or more and 1000 kV or less, and the pulse width is 1 ns or more and 100 ms or less. An easily dismantlable structure,
A first member;
a second member; and
a joining member made of an insulating member or a semiconductor member sandwiched between the first member and the second member;
a spacer member provided in the joining member, at least the surface of which is conductive;
the spacer member vaporizes when an electric pulse is applied between the first member and the second member;
the spacer member is in contact with the first member or the second member,
a contact resistance at a contact point between the spacer member and the first member or the second member is higher than a resistance value of the spacer member;
A structure , wherein the first member and the second member are both formed of a conductor . 17. The structure of claim 16 , wherein the conductor is formed from a metal, a metal oxide, or a composite containing metal particles. 18. The structure according to claim 16 , wherein the conductor has an electrical resistivity at 20° C. of 1.5×10 ⁻⁸ Ω·m or more and 1×10 ⁴ Ω·m or less. 19. The structure of any one of claims 16 to 18 , wherein the conductors of the spacer members are formed from metal. 20. The structure according to claim 19 , wherein the spacer members are made of iron, nickel, cobalt, aluminum, copper, or an alloy containing any of these. 21. The structure according to claim 16, wherein the spacer members have a shape selected from the group consisting of a sphere, an ellipsoid, and a flake. 22. The structure according to claim 16 , wherein the spacer member has a shape having a curved surface, and the curved surface is in direct contact with the first or second member or in contact with the first or second member via a thin layer of 100 μm or less. The distance between the first member and the second member is L,
23. The structure according to claim 16, wherein when the length of the spacer member in the joining direction between the first member and the second member is D, the length D is equal to the distance L. 24. The structure of claim 23 , wherein the length D is equal to or greater than 0.05 mm and equal to or less than 20 mm. 25. The structure according to claim 16 , wherein the joining member is made of a thermosetting resin. 26. The structure according to claim 25 , wherein the thermosetting resin comprises one or more resins selected from the group consisting of epoxy resins, phenolic resins, and polyimide resins. 27. The structure of claim 26 , wherein the thermosetting resin further comprises inorganic particles (excluding the spacer members). 28. The structure according to claim 16 , wherein the applied voltage of the electric pulse is 1 kV or more and 1000 kV or less, and the pulse width is 1 ns or more and 100 ms or less.