JPH06109683A - Micro potential difference measuring device - Google Patents

Abstract

(57) [Abstract] [Purpose] The contactor can be pressed against the structure with a constant pressing force regardless of the unevenness of the structure surface, and the electrical contact resistance is set to a small constant value that does not hinder measurement. To be able to measure the potential difference. [Composition] Between the electrodes 31a and 31b which are pressed against the surface of the structure 1 to pass a high-frequency current, and which can move back and forth only in the structure surface direction, and between measurement points in the vicinity of a surface defect portion at an arbitrary position of the structure. At least a pair of contacts (16 _a1 , 16 _a2 , ... 16 _b1 , 16 _b2 ,
,), A circuit board 17 made of a flexible material for circuit connection to the contactor, and a pressing mechanism 27 for pressing the tip of each contactor to the measurement point with an even force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro-potential difference measuring device for quantitatively measuring the risk that a surface defect such as a crack generated in a large structure develops into a fracture.

[0002]

2. Description of the Related Art In general, it is difficult to use a structure so that no surface defects are generated on its surface, and small cracks may occur during use. However, depending on the condition, this crack may develop into destruction.

Therefore, in order to prevent the development of this fracture in advance, an average stress state or the like has been conventionally monitored by a strain gauge, a load cell or the like. Quantitative measurement is difficult, and the detection of the above-mentioned risks has not been performed.

However, if the amount of current used recently, the frequency of current, the position of the current input / output terminal and the potential difference measurement terminal, and the material of the target member are the same, the variation of the potential difference and the stress intensity factor due to the change of the load are It was found that there is a certain proportional relationship between the amounts of change, and a technique for measuring the stress intensity factor of the crack portion has been proposed (Proceedings of the Japan Society of Mechanical Engineers, Vol. 56, Vol. 5).
28, Paper No. 89-0566A).

[0005]

However, in this measurement, since the measurement signal is as small as μV, it is necessary to weld the measurement electrode to the surface of the structure for noise prevention, and the measurement electrode can be moved to any position. No cracks, width of 0.5
Since it is as small as less than mm and a few mm in length, there is a problem that the measurement electrode cannot be accurately positioned with a crack in between. Further, when the structure surface has irregularities, there is a problem that the measuring contact cannot be pressed against the structure surface by a constant pressing force.

In view of the above points, the present invention makes it possible to press the contactor against the structure with a constant pressing force regardless of the unevenness of the surface of the structure, so that the electrical contact resistance does not interfere with the measurement and is small. An object of the present invention is to obtain a measuring device that allows measurement of a minute potential difference such that a measurement part such as a crack is sandwiched between the measuring devices.

[0007]

According to the present invention, an electrode which is pressed against a surface of a structure to pass a high-frequency current and which can advance and retreat only in the direction of the surface of the structure is sandwiched between a surface defect portion at an arbitrary position of the structure. At least a pair of contacts that measure a minute potential difference generated between nearby measurement points, a circuit board made of a flexible material that connects the contacts to the circuit, and measure the tip of each contact with equal force. And a pressing mechanism for pressing on a point.

[0008]

The electrode and the contactor for passing the high frequency current are arranged at positions sandwiching the defective portion on the surface of the structure, and they are pressed against the surface of the structure, and the high frequency current is passed through the electrode, whereby the contactor is provided. A minute potential difference between them can be measured. In this case, since each contact is connected to the flexible circuit board and the tip of each contact is pressed against the measurement point by the pressing mechanism with equal force, each contact will be It is evenly pressed against the measurement points with a sufficient force, and the electric contact resistance can be set to a small constant value that does not interfere with the measurement, and accurate minute potential difference measurement is possible.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 is a crack 2 on the surface.
Which is the object to be measured, and the crack 2 on the object to be measured 1
A micropotential difference measuring device main body 3 is mounted and mounted in the vicinity of, and an operation pendant 4 and a control box 5 are connected to the micropotential difference measuring device main body 3.

The minute potential difference measuring device body 3 has a support mechanism 6 mounted at a predetermined position on the object to be measured 1, and the support mechanism 6 has a swivel plate rotatable by a swivel mechanism 7. 8 is attached, and a CCD camera 9 for measuring the position of the crack 2 is attached to one end of the swivel plate 8,
Further, at the other end of the swivel plate 8, a measuring device main body 11 is attached which is movable by an advancing / retreating mechanism 10 toward or away from the object to be measured.

The measuring instrument body 11 is shown in FIG. 2, FIG. 3, and FIG.
As shown in FIG. 3, the frame 12 has a rectangular cross section, and a front plate 14 is fixed to the front side of the frame 12 via a shield plate 13. The front plate 14 has a plurality of openings 15
_a1 and 15 _a2 , ... And 15 _b1 , 15 _b2 , ... Are bored in two rows at a predetermined interval, and the openings 15 _a1 , 1 in one row are provided.
5 _a2 , ... _Are paired with the openings 15 _b1 , 15 _b2 ,. Each of these openings 15 _a1 ,
15 _a2 , ... 15 _b1 , 15 _b2 , ... are contacts 16 _a1 , 16 _a2 , ... 16 _b1 , 16 _b2 ,.
Are respectively inserted so as to be slidable in the axial direction.

The contacts 16 _a1 , 16 _b1 , ... _Are mounted so that their heads are electrically coupled to the circuit board 17 made of a flexible material. This circuit board 17 is shown in FIG.
As shown in FIG. 3, a circuit 18 connected to each of the contacts 16 _a1 , 16 _b1 , ... Is provided, and both side edges of the circuit 18 are connected to the frame 1
The two sockets 19 are mounted and connected to the inner surfaces of the two facing each other (see FIGS. 3 and 6). In addition, in the socket 19, a plug 21 provided at the tip of the signal cable 20 is formed in the frame 12 and the opening 12 is formed in the frame 12.
It is fitted through a.

A lid 22 is mounted on the back side of the frame 12, and an air bag is provided on the inner surface of the lid 22 via a support plate 23, a spacing plate 24, a base plate 25 and a cushion plate 26. The air bag 27 is fitted with a cushion plate 28 bent in a U shape on the front side of the air bag 27 (see FIGS. 3 and 7). The heads of _a1 , 16 _b1 , ... Are contact-supported. In addition, reference numeral 29 in FIGS. 4 and 7 denotes an air inlet / outlet tube for the air bag 27.

Further, on the outer surfaces of both side walls of the frame body 12 facing each other, terminal support plates 30a, 30b extending in parallel to the left and right of the row of contactors are provided respectively.
are arranged so as to be movable in a direction parallel to the axes of _a1 , 16 _b1 , ..., And terminals 32a for insulating and supporting the power feeding contacts 31a, 31b are provided on the front surfaces of the central portions of the terminal supporting plates 30a, 30b.
32b is attached. On the other hand, brackets 33, 33, ... Are projectingly provided on the outer sides of the four corners of the frame body 12, and the air cylinder 3 attached to the brackets 33, 33 ,.
The tips of piston rods 34a, 34a, ... Of 4, 34, ... Are connected to both ends of the terminal support plates 30a, 30b, and the operation of the air cylinder 34 causes the terminal support plates 30a, 30b to contact the contactors 16a1 ,. 16b1, ... Can be moved in the axial direction. Incidentally, reference numeral 3 in FIG.
Reference numerals 5a and 35b are cables for supplying power to the power supply contacts 31a and 31b, respectively.

As shown in FIG. 8, the internal configuration of the control box 5 takes in a measurement signal switch 40 connected to a signal cable from the measuring instrument main body 11 and a signal selected by the measurement signal switch 40. A lock-in amplifier 41, a power supply device 42 for supplying a measuring current to the minute potential difference measuring device 3, an advancing / retreating mechanism 10 of the minute potential difference measuring device 3, a swivel mechanism 7, and an air pressure control section 43 for controlling the air bag 27, and these. And a computer 44 for controlling the.

The measurement signal switching device 40 includes a measurement device main body 11
Pairs of contacts (16 _a1 and 16 _b1 , 16 _a2 and 1
6 _b2 , ...) Incorporating changeover switches 45 a, 45 b, ... The operation pendant 4 is composed of an air bag pressure gauge 46 of the air bag 27, a monitor TV 47 of the CCD camera 9, and an operation switch 48 of the pneumatic control unit 43.

As shown in FIG. 9, the monitor TV 47 has a horizontal reference line 50a and a vertical reference line 50 on its screen.
b, each contact (16 _a1 , 16 _a2 , ... 16 _b1 , 16 _b2 ,
...) marks 51a and 51b are drawn.

However, when measuring a minute potential difference in a crack portion generated on the surface of a structure, the crack 2 is as small as 0.5 mm or less in width and several mm in length. The crack 2 is displayed on the screen of the monitor TV 47 so that the crack 2 is located between the marks 51a and 51b, and the position is detected. Then, based on the detected value, the turning mechanism 7 is operated to move the measuring instrument main body 11 to the position of the CCD camera 9, and the advancing / retreating mechanism 10 causes a crack 2 in the measuring instrument main body 11. Press on the structure surface.

After that, when air is further supplied into the air bag 27 and the air bag 27 is inflated, the expansion force causes the respective contacts 16 _a1 , 16 _a2 , ..., 16 _b1 , 16 _b2 ,.
However, as shown in FIG. 8, the crack 2 is sandwiched and pressed against the surface of the structure which is the object to be measured. In this case, each contact 1
Since 6 _a1 , 16 _a2 , ..., 16 _b1 , 16 _b2 , ... _Are pressed by the air bag 27, even if the structure surface has irregularities, the tips of the respective contact elements are reliably and evenly structured. It is pressed against the surface of the object.

On the other hand, at the same time, the air cylinder 34 is actuated, and the feeding contacts 31a, 31b are pressed against the surface to be measured via the terminal supporting plates 30a, 30b.

Therefore, while supplying power to the power feeding contacts 31a and 31b, the measurement signal switch 40 selects any pair of measuring contacts (16 _a1 , 16 _a2 , ..., 16 _b1 , 16 _b2 , ...). By doing so, it is possible to measure a minute electric potential difference between both the contacts sandwiching the crack 2 and obtain the stress intensity factor of the crack portion.

That is, the position of the contact for measurement is set to the CCD.
Since the camera 9 can be accurately positioned, the distance between each pair of contacts can be minimized, and the internal resistance of the DUT proportional to this distance can be minimized. further,
Since the contact resistance due to the pressing force of the contact can also be made constant, the accurate minute potential difference of the crack as a whole can be measured. Moreover, since the distance between each contactor and the power feeding contactor and the surface of the object to be measured can be adjusted by the air bag or the air cylinder, the measurement can be accurately performed even on the object to be measured having irregularities.

10 and 11 are views showing another embodiment of the present invention, in which reference numeral 60 designates a measuring instrument body positioning frame into which the measuring instrument body 11 can be fitted. A transparent plate 61 capable of opening and closing the opening of the frame body 60 is swingably attached to the frame body 60 about a shaft 62. On the transparent plate 61, the horizontal reference line 50a, the vertical reference line 50b, and the mark 5 drawn on the screen of the monitor TV 47 are displayed.
Horizontal reference lines 63a, vertical reference lines 63b, and marks 64a, 64b are drawn in exactly the same way as 1a, 51b.

Then, the frame 60 is placed on the object 1 to be measured, and the crack 2 is aligned so that the crack 2 is located between the marks 64a and 64b and is temporarily fixed. Then, as shown in FIG. 11, if the transparent plate 61 is opened and the measuring instrument main body 11 is inserted into the frame body 60, the measuring instrument main body 11 is reliably positioned, and each contact has a predetermined crack. Set to position. Therefore, as in the first embodiment, it is possible to measure the minute electric potential difference between the contacts that sandwich the crack.

In the first embodiment, the CCD camera and the measuring instrument main body are exchanged around a vertical axis, but the turning axis for this exchange may be an axis in any direction such as a horizontal axis. .

[0027]

As described above, the present invention provides a flexible circuit board for circuit connection to a contactor for measuring a minute potential difference between measurement points in the vicinity of a surface defect portion at an arbitrary position of a structure. In addition to being composed of a material that has a contact point, a pressing mechanism that presses the tip of each contact to the measurement point with an even force is provided, so the contact of the measuring instrument can always be applied with a constant pressing force regardless of the unevenness of the structure surface. It can be pressed against the surface of the structure, the electric contact resistance can be maintained at a constant small value that does not hinder the measurement, and the minute potential difference can be accurately measured.

Further, when a measuring device main body moving device for moving the measuring device main body to a measuring point whose position is measured by a camera for picking up an image of a desired measuring point is provided or a contactor positioning device is provided, an arbitrary position is measured. The contact for measurement can be accurately and easily positioned even for a small crack.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a minute potential difference measuring device of the present invention.

FIG. 2 is a perspective view of a measuring device main body.

FIG. 3 is a sectional view taken along the line III-III in FIG.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a plan view of a circuit board.

FIG. 6 is a partial view of a measuring contact portion.

FIG. 7 is an exploded perspective view of an air bag mounting portion.

FIG. 8 is an explanatory diagram of a configuration of a measurement system.

FIG. 9 is an explanatory diagram of a monitor TV screen.

FIG. 10 is a perspective view of a measuring device main body positioning frame.

FIG. 11 is a diagram showing a state in which a transparent plate of the measuring device main body positioning frame is opened.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Object to be measured 2 Crack 3 Micropotential difference measuring device main body 6 Support mechanism 7 Swivel mechanism 8 Swivel plate 9 CCD camera 10 Advance / retract mechanism 11 Measuring device main body 12 Frame 14 Front plate 16 _a1 , 16 _a2 , ... Contactor 16 _b1 , 16 _b2 , ... Contact 17 Circuit board 19 Socket 20 Signal cable 21 Plug 27 Air bag 28 Cushion board 30a, 30b Terminal support plate 31a 31b Feed contact 34 Air cylinder 47 CCD camera monitor TV 50a Horizontal reference line 50b Vertical reference line 51a , 51b Mark 60 Measuring device main body positioning frame

Claims (4)

[Claims] 1. An electrode which is pressed against a surface of a structure to pass a high-frequency current, and which can advance and retreat only in the direction of the surface of the structure, and which is generated between minute measuring points in the vicinity of a surface defect portion at an arbitrary position of the structure. At least a pair of contacts for measuring the potential difference,
A circuit board made of a flexible material for circuit connection to the contact, and a pressing mechanism for pressing the tip of each contact to the measurement point with an even force,
Micro potential difference measuring device. 2. The micro-potential difference measuring device according to claim 1, wherein the pressing mechanism is an air bag that presses the heads of the contacts from above the circuit board. 3. A camera having an image of a desired measuring point on the surface of a structure, and a measuring device main body moving device for moving the measuring device main body so that the contactor is located at the measuring point measured by the camera. The minute potential difference measuring device according to claim 1 or 2, characterized in that. 4. A frame body provided with a mark for matching the pressing positions of the contacts corresponding to the mark created on the monitor TV screen, and temporarily fixed to the surface of the structure at the point where the two marks coincide. 3. The minute potential difference measuring device according to claim 1 or 2, further comprising a contactor positioning device configured to position the contactor by fitting the measuring device main body in the frame body.