JPH0749417Y2 - Electric resistance flaw detection probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an electric resistance flaw detection probe suitable for measuring the crack depth on the surface of a metal member.

[Conventional technology]

Conventionally, there is an electric resistance flaw detection probe as one of the devices for nondestructively measuring the crack depth on the surface of a metal member.
For example, as shown in the perspective view of FIG. 3, four through-holes 33 in a box-shaped casing 32 screwed onto a substrate 31 are arranged at equal intervals.
, Four contact needles 34 each having a conical tip portion 34a are provided therethrough, and each contact needle 34 is wound with a coil spring 35 for biasing the tip end direction, and a lead wire at the rear end. 36 are connected.

Then, in measuring the crack depth on the surface of the metal member with this probe, as shown in FIG. 4 (A), the crack 38 having the crack depth d of the metal member 37 is broken into four contact needles 34. Insert the DC power supply 39 to the needles 34 at both ends and hold a constant DC current.
Flow 40 and measure the voltage with a voltmeter 41 connected to the two inner needles 34.

To determine the crack depth d from this voltage measurement value, the voltage value when there is no crack is Vo, and the voltage value when the crack 38 is sandwiched is V
Then, V / Vo and the ratio d / a of the distance a between the needles 34 and the crack depth d
By utilizing the fact that there is a certain relationship as shown in FIG. 7B, the crack depth d can be obtained by measuring V / Vo.

Incidentally, the surface of the metal member 37 to be measured is often not only flat but also has irregularities, but in such a case as well,
Each contact needle 34 freely moves by the urging force of the coil spring 35 and its tip 34a is pressed against the uneven surface of the metal member 37, so that accurate measurement is always performed even on a complicated curved surface.

However, such a probe has the following drawbacks.

That is, when the depth of the cracks 38 is shallow or the distance between the cracks 38 is narrow, it is necessary to reduce the distance a between the contact needles 34, but the biasing coil spring 35 is wound around the contact needles 34. Therefore, there is a limit to reducing the distance a between the contact needles 34. In addition, the pressing force may be insufficient due to deterioration of the coil spring 35, which may result in poor contact between the tip end portion 34a of the contact needle 34 and the surface of the metal member 37 to be measured, making measurement impossible.

[Problems to be solved by the device]

The present invention has been proposed in view of such circumstances,
Since the coil spring for urging the contact needle pressing force is not required, the mechanism around the contact needle can be simplified and the contact needle interval can be reduced, and the urging force is reduced due to deterioration of the contact needle pressing force urging member. Another object of the present invention is to provide an electric resistance flaw detection probe in which the pressing force changes according to the distance between the tip of the contact needle and the surface of the metal member.

[Means for Solving the Problems]

To this end, the present invention provides a ferromagnetic material support body having a plurality of through holes at equal intervals, and a non-magnetic material support rod that passes through the through holes to prevent forward pull-out, so that the central portion of the tip is sharpened. A plurality of ferromagnetic material contact needles and a box-shaped holder provided in front of the support body and provided with a plurality of through holes for holding the contact needles at equal intervals and slidably in the axial direction. The support and the contact needle are magnetized in opposite polarities.

[Action]

In the electric resistance flaw detection probe of the present invention, the repulsive force acts between the opposing magnetic poles of the support and the contact needle, which have the same polarity.
The contact needle is constantly pressed against the surface of the metal member by this repulsive force, and the force acting between the two opposing magnetic poles is proportional to the product of the strengths of both magnetic poles and inversely proportional to the square of the interval. As it is attached, the pressing force between the tip of the contact needle and the surface of the metal member increases.

〔Example〕

An embodiment of a probe for electric resistance flaw detection of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a partial cut thereof, and FIG. 2 is an explanatory view of an operating procedure of the same.

In FIG. 1, a prismatic support 1 made of a ferromagnetic material
Has four through holes 2 at equal intervals along the longitudinal direction on the center line of the side surface. The four contact needles 3 facing the four through-holes 2 are made of a ferromagnetic material, and the tips 3a thereof are formed in a conical shape, and the non-insertion holes 2 are inserted into the base. A support rod 4 made of a magnetic material is attached, and a stopper 5 for preventing falling is attached to the rear end of the support rod 4. A lead wire 6 is connected to the rear end of the support rod 4.

A box-shaped holder 7 having four through holes 8 for holding the contact needles 3 at equal intervals and slidably in the axial direction is fixed to the front portion of the support 1 with screws 9. Has been done.

In such an apparatus, the support 1 made of a ferromagnetic material and the contact needle 3 made of a ferromagnetic material are magnetized in opposite polarities so that the opposite ends are S poles as shown in FIG. As described above, the tip 11a of the four contact needles 3 are brought into contact with the surface of the metal member 10 to be measured with the crack 11 in the center, and the tip 3a of the two contact needles 3 at both ends are brought into contact. A direct current is passed through the two contact needles 3 at both ends, and the voltage is measured by the inner two contact needles 3.

At this time, since a repulsive force acts between the S poles of the support 1 and the contact needle 3 which face each other, the contact needle 3 is always pressed against the uneven surface of the metal member 10 by this repulsive force, and also acts between the two opposing magnetic poles. Since the force is proportional to the product of the strengths of both magnetic poles and inversely proportional to the square of the distance, the pressing force between the tip 3a of the contact needle 3 and the surface of the metal member 10 increases as the probe is pressed. The tips 3a of the four contact needles 3 come into contact with any uneven surface, and no contact failure occurs.

Further, since the stopper 5 is attached to the rear end of the support rod 4 of the contact needle 3, the contact needle 3 does not drop out due to the repulsive force, and the current supplied for the measurement is a direct current. It can be measured without being affected by magnetization.

Thus, this device has the following advantages.

(1) By using a magnetic force instead of the conventional coil spring, the pressing force of the contact needle 3 does not decrease due to deterioration unlike the coil spring.

(2) The coil spring is unnecessary.

(3) Since the mechanism around the contact needles 3 is simplified, the distance between the contact needles 3 can be reduced.

(4) The biasing force of the coil spring is constant, but when the magnetic force is applied, the repulsive force becomes stronger as the probe is pressed. Therefore, the tip of the contact needle 3 and the surface of the metal member 10 are pressed. Power increases.

[Effect of device]

In short, according to the present invention, a ferromagnetic material support body having a plurality of through holes at equal intervals and a non-magnetic material supporting rod that passes through the through holes to prevent forward pull-out are provided, and the tip central portion is sharpened. A plurality of ferromagnetic material contact needles, and a box-shaped holder provided in front of the support body and having a plurality of through holes for holding the contact needles at equal intervals and slidably in the axial direction. Since the support and the contact needle are magnetized in opposite polarities, the coil spring for urging the contact needle pressing force is not required, and the mechanism around the contact needle is simplified and the contact needle interval can be reduced. In addition, it is possible to obtain a probe for electric resistance flaw detection in which the urging force does not decrease due to deterioration of the contact needle pressing force urging member, and the pressing force changes according to the distance between the contact needle tip and the metal member surface The present invention is extremely useful in industry.

[Brief description of drawings]

FIG. 1 is a perspective view of a partially cutaway showing an embodiment of the electric resistance flaw detection probe of the present invention, and FIG. 2 is an explanatory view of the operating procedure of the same. FIG. 3 is a perspective view of partial cutting of a conventional probe, and FIG. 4 is an explanatory view of a crack depth measuring procedure. 1 ... Support, 2 ... Through hole, 3 ... Contact needle, 3a ... Tip part, 4
... Support rod, 5 ... Stopper, 6 ... Lead wire, 7 ... Holding body, 8 ... Through hole, 9 ... Screw, 10 ... Metal member, 11 ... Crack.

Claims (1)

[Scope of utility model registration request] 1. A support member made of a ferromagnetic material having a plurality of through holes at equal intervals, and a non-magnetic material support rod passing through the through holes so as to prevent the through hole from being pulled forward. A plurality of ferromagnetic material contact needles, and a box-shaped holder provided in front of the support and having a plurality of through holes for holding the contact needles at equal intervals and slidably in the axial direction, A probe for electrical resistance flaw detection, wherein the support and the contact needle are magnetized in opposite polarities.