JP2002286699A - Apparatus and method of striking used for evaluation of soundness of concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus, of striking, wherein the generation of a noise and an irregularity in striking energy can be suppressed by a constitution which excludes a mechanical rotation part, when the soundness of concrete is evaluated by analyzing a striking sound generated at a time when the surface of the concrete is stuck. SOLUTION: The striking method is provided with a process in which a striking head is pulled by a rubber body toward the surface or in parallel to the surface, a process in which the striking head in a pulled state is attracted by an electromagnet so as to be moved away from the surface, and a process in which the moved-away striking head strikes the surface. The striking apparatus is provided with a contact plate which is to be brought into contact with the surface, the striking head, the rubber body which pulls the striking head toward the contact plate or in parallel to the contact plate, and the electromagnet by which the striking head is moved away from the contact plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the evaluation of concrete soundness, and more particularly, to the evaluation of concrete soundness for evaluating the soundness of concrete by analyzing the sound of a blow when the surface of the concrete is hit. And a hitting device and a hitting method used therefor.

[0002]

2. Description of the Related Art Conventionally, non-destructive techniques for evaluating the difference in thickness and quality of lining concrete or the state of internal defects such as internal cracks and voids in concrete structures include: 1. Concrete surface Or a configuration in which the percussion sound is directly sampled by a microphone as air vibration and the collected percussion sound is analyzed (described in Japanese Patent Publication No. 4-10987), or 2. Concrete with a hammer having a spherical head. A configuration in which a sound of a surface hit and transmitted through the concrete itself is collected by a microphone, and the collected transmitted sound is analyzed (described in JP-A-5-328661).
It has been known.

[0003]

However, there is no specific description of the impact on the concrete surface in the above-mentioned prior art, and in the above-mentioned prior art, a hammer having a spherical head, a hammer having a spherical head, etc. However, it is described that it is preferable to perform the impact mechanically. That is, the hammer is a rotatably supported rod, a sphere fixed to the rod, a spring or rubber for applying a rotational force to the rod, and a rod to which the rotational force is applied. Is constituted by the locking means for detachably locking the lock, there are the following problems. That is,

[0004] 1. Since the rod is mechanically rotatably supported, sound or vibration (hereinafter, collectively referred to as noise) is generated from the mechanical part, and the noise hinders soundness evaluation.
In particular, when hitting hard, the obstacle becomes apparent.

[0005] 2. If the surface formed by the trajectory of the rod (same as the surface formed by the trajectory of the sphere, hereinafter referred to as a rotating surface) is not vertical, the mechanical part is flat on the out-of-plane direction of the rotating surface. Since a load is applied, the impact energy may vary depending on the impact posture. Further, the flat load contributes to the wear or damage of the mechanical part and, consequently, the generation of the noise. 3.Because the steel ball does not collide with the concrete surface vertically,
A longitudinal force acts on the mechanical part, which contributes to the wear or damage of the mechanical part and thus to the noise. 4. Since the hit point of the steel ball is limited to one place, the hit point is locally worn, and the hit energy varies.

The present invention has been made in view of such a conventional problem, and has a structure in which a mechanical rotating portion is eliminated, thereby suppressing generation of noise and variation in impact energy. It is an object to provide a hitting device and a hitting method used for evaluation.

[0007]

SUMMARY OF THE INVENTION The present invention has the following arrangement to solve the above-mentioned problems. The gist of the invention according to claim 1 is that, in analyzing the soundness of a concrete hitting the surface of the concrete, the soundness of the concrete is evaluated in order to evaluate the soundness of the concrete. A face plate, a support plate installed on the front plate via a support, a hitting point having a spherical hitting point, hitting the surface of the concrete, and both ends being installed on the front plate and the hitting head, and being pulled. A rubber body, and an electromagnet installed on the support plate to suck the impact head and move the impact head away from the front plate,
The hitting head hits the surface of the concrete when the attraction of the electromagnet is stopped. The hitting device is used for evaluating the soundness of concrete. The gist of the invention according to claim 2 is that, by analyzing a striking sound generated when striking the surface of the concrete, the soundness of the concrete is evaluated in order to evaluate the soundness of the concrete. A face plate, a support plate installed on the front plate via a support, a hitting point having a spherical hitting point, and hitting the surface of the concrete,
A compression spring disposed between the support plate and the striking head and compressed; and an electromagnet disposed on the support plate for sucking the striking head and moving the striking head away from the front plate; The hitting head hits the surface of the concrete by stopping the attraction of the electromagnet. The hitting device is used for evaluating the soundness of concrete. The gist of the invention according to claim 3 is that the hitting head includes:
It is composed of a steel ball and a suction plate having a spherical or conical concave portion, and both ends of the rubber body are respectively installed on the suction plate and the front plate, and the steel ball is rotatable. The hitting device according to claim 1, which is used for evaluating the soundness of concrete. The gist of the invention according to claim 4 is that the impact head is constituted by a steel ball and a suction plate having a spherical or conical concave portion, and the compression spring is disposed between the suction plate and the support plate. The steel ball according to claim 2, wherein the steel ball is rotatable.
It is a hitting device used to evaluate the soundness of concrete.
The gist of the invention according to claim 5 is that a microphone having a cylindrical hood for collecting the impact sound is installed via a cushioning material, and the cylindrical hood is formed of a vinyl chloride pipe and an inside of the vinyl chloride pipe. 5. A hard sponge tube inserted into a hard sponge tube between which a rubber tube is sandwiched, and a cork tube inserted into the hard sponge tube. The impact device used for the evaluation of the soundness of concrete. The gist of the invention described in claim 6 is that
In the soundness evaluation of concrete for evaluating the soundness of concrete by analyzing the sound of hitting when the surface of the concrete is hit, a hitting head having a spherical hitting point is formed by a rubber body or a tension spring. A step of pulling toward the surface of, or a step of radially pulling in a plurality of directions in parallel with the surface; a step of causing the striking head in the pulled state to be attracted by an electromagnet to move it away from the surface of the concrete; And stopping the suction of the concrete so that the hitting head that has been moved away hits the surface of the concrete. The gist of the invention according to claim 7 is that a hitting head having a spherical hitting point is used in the evaluation of the soundness of concrete in which the soundness of the concrete is evaluated by analyzing the sound of hitting when the surface of the concrete is hit. By pushing the pressing head toward the surface of the concrete by a compression spring, causing the striking head in the extruded state to be attracted by an electromagnet, and moving it away from the surface of the concrete, and stopping the attraction of the electromagnet. Having the struck impact head strike the surface of the concrete;
It is a hitting method used to evaluate the soundness of concrete.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a hitting apparatus and a hitting method used for evaluating the soundness of concrete according to an embodiment of the present invention will be described in detail with reference to the drawings.

First Embodiment (Striking Apparatus 1) FIGS. 1 and 2 are a sectional view and a front view, respectively, showing a striking apparatus 1 used for evaluating the soundness of concrete according to an embodiment of the present invention. is there. In FIGS. 1 and 2, a support 11 is provided upright on a support plate 10, and an annular front plate 12 is installed by the support 11 in parallel with the support plate 10. The front plate 12 has rubber support portions 1 at equal intervals on a concentric circle with a through hole 13 provided in the front plate 12.
4 is provided, and one end of a rubber body 30 described later is provided on the rubber support portion 14.

A striking head is formed by a steel-made substantially hemisphere 21 and a disk-shaped suction plate 22 fixed to the hemisphere 21 and made of a ferromagnetic material. Further, rubber mounting portions 23 are installed at equal intervals along the outer periphery of the suction plate 22, and one end of a rubber body 30 described later is installed on the rubber mounting portion 23. The rubber body 30 has its both ends mounted on the rubber support portion 14 and the rubber mounting portion 23, respectively, and is radially arranged in a pulled state (extended state) to elastically support the striking head. That is, the hitting head is the front plate 1
It is in a state of being radially pulled in a plurality of directions (8 directions at 45 ° intervals) in a plane parallel to 2 and is in equilibrium.

At this time, the suction plate 22 and the rubber body 30 are located in the through holes 13 and are substantially in the same plane as the front plate 12.
On the other hand, the tip of the hemisphere 21 of the striking head (hereinafter, referred to as a striking point) is located substantially on the central axis of the through hole 13, and the striking point penetrates the through hole 13 to support the front plate 12. It protrudes to the side opposite to 10.

Further, the support plate 10 has an electromagnet 40 which is movable on a line whose center substantially coincides with the center of the through hole 13.
Is installed. Pinion 4 installed on electromagnet 40
1 is engaged with a rack 42 installed on the support plate 10 and rotated by pinion rotating means (not shown). Therefore, the electromagnet 40 rotates the pinion 41 (forward rotation).
As a result, the suction plate 22 can be moved forward to the position of the front plate 12 to suck the suction plate 22, and further, by the rotation (reverse rotation) of the pinion 41, the suction plate 22 can be retracted by a predetermined distance in the suction state.

Further, a fixed arm 52 is provided on one of the columns 11, and a microphone 50 for collecting a striking sound is provided on the fixed arm 52 via a buffer 58.
The cushioning material 58 is used to collect the below-described impact sound (generally 2.2 kHz).
(target of z or more), the shape is so rigid that the vibration of a relatively high frequency is not propagated, and is substantially frustoconical. The microphone 50 (audible range 2)
(Up to 0 kHz), a cylindrical hood 51 is provided. The hood 51 includes an outer rigid sponge tube 55 and an inner rigid sponge tube 55 sandwiched between a vinyl chloride tube 53 having an outer diameter of 70 mm and a rubber tube 54 having a thickness of 2 mm interposed therebetween. And a cork tube 57 (inner diameter 21 mm, wall thickness 13 mm) inserted inside the inner hard sponge tube 56 (inner diameter 32 mm) (hereinafter, the state of FIG. 1 is referred to as an initial state). The number, shape, material, and the like of the fixed arm 52, the cushioning material 58, and the hood 51 are not limited to those described above. Further, the microphone 50 may be installed on the support plate 10 or the front plate 13. Further, the fixing arm 52 may not be provided, and may be installed via only the cushioning material 58.

(Striking Method) FIGS. 3 and 4 are cross-sectional views illustrating a striking method used for evaluating the soundness of concrete according to an embodiment of the present invention. FIG. 3 shows a state immediately before striking. FIG. 4 shows the state at the time of impact. Note that FIG.
The same parts as those described in the initial state are denoted by the same reference numerals, and some description thereof will be omitted. FIG.
The electromagnet 40 in the initial state shown in (1) moves forward to the position of the front plate 12 by the rotation (forward rotation) of the pinion 41 and sucks the striking head (formed by the hemisphere 21 and the suction plate 22). , Rotation of the pinion 41 (reverse rotation)
Indicates a state of being retracted by a predetermined distance in the suction state, that is, a state immediately before impact (hereinafter, the state of FIG. 3 is referred to as a standby state).

That is, since the impact head moves from the initial state to the standby state and moves by a predetermined distance, the rubber body 30 pulled in advance is parallel to the front plate 12 in the initial state. In the standby state, the front plate 12 is inclined at a predetermined angle with respect to the front plate 12. Therefore, in the standby state, the rubber body 3
A pulling force of 0 generates a component force in the normal direction of the front plate 12 (horizontal right direction in FIG. 3), and the component force (hereinafter referred to as a striking force) pulls the striking head toward the front plate 12. Becomes At this time, since the rubber body 30 is further extended by a predetermined length, a larger tensile force is applied to the rubber body 30.

The magnitude of the impact force is determined by the magnitude of the tensile force applied in advance in the initial state,
0, the spring coefficient, and the angle at which the stretched rubber body 30 is inclined with respect to the front plate 12, that is, the electromagnet 40
Is determined by the retreat distance, etc., and is a design matter.

The transition from the initial state to the standby state (state in which the electromagnet is excited) is performed before the front plate 12 is brought into contact with the concrete surface 90 at a position to be hit by a manipulator (not shown). Also,
It may be after confrontation. In the standby state, the front end surface of the hood 51 of the microphone 50 is in contact with the concrete surface 90 to assist in collecting the impact sound.

FIG. 4 is a cross-sectional view showing a state in which the striking head strikes the concrete surface 90 when the excitation of the electromagnet 40 is stopped, which is in the standby state shown in FIG. (Hereinafter, the state of FIG. 4 is referred to as a hit state). The same parts as those described in the initial state of FIG. 1 are denoted by the same reference numerals, and a part of the description is omitted. That is,

In FIG. 4, the front plate 12 is opposed to a concrete surface 90 by a manipulator (not shown) at a position where the front surface 12 is hit.
The striking head, which is attracted and pulled back and is given a striking force, has the excitation of the electromagnet 40 stopped.
Is released from the suction, and jumps out toward the concrete surface 90 by the impact force, and the impact point of the hemisphere 21 collides with the concrete surface 90 soon.

The striking head striking the concrete surface 90 rebounds and strikes again or repeatedly. However, in the case where the sampling time for sampling the sound for soundness evaluation is short (for example, In the case of about 20 msec), the sampling is completed before the second blow, so that it does not hinder the soundness evaluation.

As described above, since the present invention does not include a mechanical rotation support portion, there is no generation of noise due to rotation.
In addition, since the tensile force of the rubber body 30 is sufficiently large compared to the weight of the striking head, regardless of the striking posture (same as the direction in which the striking head projects or the direction normal to the front plate 12), A constant impact energy can be guaranteed. Further, the present invention is to easily and quickly collect a large amount of data because the impact head strikes the surface of the concrete only by moving the electromagnet 40 forward and exciting, then retreating and stopping the excitation, and the impact head strikes the concrete surface. it can.

In the present invention, the tensile force applying means is not limited to a rubber body, and a metal or resin tension spring may be provided instead of the rubber body. The striking head may be formed by assembling the hemisphere 21 and the suction plate 22 separately, or may be integrally formed. Further, instead of the hemisphere 21, a substantially cylindrical or conical shape formed into a spherical shape only at the tip or a flat body having a convex lens shape may be used. Further, the driving means of the electromagnet is not limited to the rack / pinion, but may be an encoder, an electric cylinder, or the like, or
A combination of a hydraulic cylinder and mechanical locking means may be used.

(Data collection method) Next, the impacting device 1 used for evaluating the soundness of concrete of the present invention was used.
A method for collecting data of the propagation impact sound transmitted through the concrete itself will be described. 1. In the standby state, the microphone 50 is in a standby state in which the hood 51 surrounding the microphone 50 is pressed against the concrete surface 90 and sound can be collected. 2. Next, as the excitation of the electromagnet 40 is stopped, the striking head pops out, and strikes the concrete surface 90. 3. Then, using the impact sound of the impact as a trigger, data is collected only for a predetermined time (for example, 20 msec), and the collected data is transmitted to the calculating means for soundness evaluation. Note that the data is collected from the time of the first hit to the time when the hitting head rebounds hits the concrete surface 90 twice by the tensile force of the rubber body 30 instead of the predetermined time. There may be. In addition, the trigger may use a signal for stopping excitation of the electromagnet 40 instead of the hitting sound, or may be a timing delayed by a predetermined time from the signal.

Embodiment 2 (Striking Apparatus 1) FIG. 5 is a sectional view showing a striking apparatus 1 used for evaluating the soundness of concrete according to another embodiment of the present invention. Indicates the initial state.
FIG. 5 has substantially the same configuration as that of FIG. 1 (the first embodiment), and is used by substantially the same hitting method. The same parts as those described in FIG. 1 are denoted by the same reference numerals, and a part of the description will be omitted. That is,

In FIG. 5, the rubber member 30 which has been pulled in advance is inclined at a predetermined angle with respect to the front plate 12 even in the initial state. At this time, the rubber body 3
The tensile force of 0 generates a component force in the normal direction of the front plate 12 (horizontal right direction in FIG. 5), and the suction plate 22 is pressed against the stopper 15 installed on the front plate 12. Further, the electromagnet 40 is fixed to the support plate 10 and does not move forward and backward. Therefore, the state shifts from the initial state to the standby state only by exciting the electromagnet 40.

Next, in a standby state (a state in which the electromagnet 40 is excited), the angle formed between the rubber body 30 and the front plate 12 is further increased, and the rubber body 30 is further extended. Of the front plate 12 in the normal direction (hereinafter, referred to as impact force) becomes large as compared with the initial state. Also, if the angle formed by the rubber body 30 and the front plate 12 is relatively large in the initial state, the difference between the angle between the initial state and the standby state becomes small, so that the standby state (same at the start of impact). From the standby state to the striking state, the decrease in the striking force decreases. Therefore, the present invention can be used by the same hitting method as in the first embodiment, and has the same operation and effect. The electromagnet 40 is not limited to a fixed one, and may be one that can move forward and backward freely as in the first embodiment.

Embodiment 3 (Striking Apparatus 1) FIG. 6 is a cross-sectional view showing a striking apparatus 1 used for evaluating the soundness of concrete according to another embodiment of the present invention. Indicates the status. FIG.
, The same parts as those described in FIG. 5 (the second embodiment) are denoted by the same reference numerals, and a part of the description will be omitted. That is,

FIG. 6 shows a state in which the rubber body 30 in FIG. 5 is removed, and instead, compression springs 60 are arranged between the support plate 10 and the suction plate 22 at equal intervals on the concentric circle with the through hole 13. It is. Since the outer diameter of the suction plate 22 is larger than the inner diameter of the through hole 13 of the front plate 12, the impact head does not pass through the front plate 12 and come off. In an initial state shown in FIG. 6 (a state in which the electromagnet 40 is not excited), the compression spring 60 is in a compressed state (a state in which a repulsive force is applied).
The suction plate 22 is pushed out toward the front plate 12, and the suction plate 22 is pressed against the stopper 15 provided on the front plate 12.

That is, in the second embodiment, the rubber body 3
In the present invention, the force for hitting is applied by the repulsive force of the compression spring 60, whereas the force for hitting is applied by the tensile force of 0. Therefore, since the rubber body 30 and the tensile force described in the second embodiment can be read as the compression spring 60 and the repulsive force, respectively, the present invention is used by the same striking method as in the second embodiment. And have the same functions and effects. The material of the compression spring is rubber, synthetic resin,
Any of metal and the like may be used. Further, the electromagnet 40 may be capable of moving back and forth as in the first embodiment.

Fourth Embodiment (Striking Apparatus 1) FIG. 7 is a cross-sectional view showing a striking apparatus 1 used for evaluating the soundness of concrete according to another embodiment of the present invention. Indicates the initial state.
7, the same parts as those described in FIG. 1 (the first embodiment) are denoted by the same reference numerals, and a part of the description will be omitted. That is,

In FIG. 7, the hitting head is a steel ball 71.
And a disk-shaped suction plate 72 having a spherical or conical concave portion, which are separable. And, at regular intervals along the outer periphery of the suction plate 72, a spring mounting portion 73 on which one end of a tension spring 80 described later is provided, is provided.
Also, at equal intervals on the concentric circle with the through hole 13 of the front plate 12,
A spring support 16 on which one end of a tension spring 80 described later is provided is provided. The tension spring 80 has its both ends mounted on the spring mounting portion 73 and the spring support portion 16, respectively, and is radially arranged in a stretched state (extended state) to elastically support the suction plate 72. . That is, the suction plate 72
Are radially pulled in a plurality of directions (for example, 8 directions at 45 ° intervals) in a plane parallel to the front plate 12 and are balanced.

At this time, although a part of the steel ball 71 penetrates through the through hole 13 and protrudes to the side opposite to the support plate 10 of the front plate 12, the outer diameter of the steel ball 71 is However, since the inner diameter of the through hole 13 of the front plate 12 is larger than that of the steel ball 71, the steel ball 71 itself does not pass through the front plate 12 and slip out. That is, in the initial state, the steel ball 71 is held in a pocket formed by the concave portion of the suction plate 72 and the inner edge of the through hole 13, and in the standby state, is attracted to the electromagnet 40 via the suction plate 72, At the time of hitting, since it is pressed against the concave portion of the suction plate 72 and jumps out, it does not separate from the hitting device 1.

Therefore, the electromagnet 4 in the initial state
0 by the rotation (forward rotation) of the pinion 41
To the position shown in FIG.
1 and the suction plate 72, and the pinion 41
With the rotation (reverse rotation), the slider is retracted by a predetermined distance in the attracted state, and the excitation of the electromagnet 40 is stopped. According to the above steps, the steel ball 71 hits the concrete surface 90, so that the present invention can be used in the same manner as in the first embodiment, and has the same functions and effects. In particular, since the steel ball 71 is freely rotatable, the hit point is not limited to one location. Therefore, local wear can be suppressed even by multiple impacts, and long-term use with constant impact energy is possible.

The present invention is not limited to the suction plate 72 formed of a ferromagnetic material, but may be formed of a non-magnetic material such as stainless steel or resin.
At this time, the suction plate 72 is sucked together with the steel ball 71. Further, the material of the tension spring may be any of rubber, synthetic resin, metal and the like. Further, the electromagnet 40 is not limited to one that can move forward and backward, and may be fixed to the support plate 10.

[0035]

According to the present invention, since the striking force is directly applied to the striking head by a pulling force or a repulsive force of rubber or the like, and no mechanical rotary support portion is provided, the striking force is reduced. In addition, a remarkable effect is obtained in that no noise is generated and variation in the impact energy can be suppressed. Further, only by stopping the excitation after the electromagnet is excited, the impact head strikes the surface of the concrete, so that a large amount of data can be collected easily and quickly and repeatedly.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a striking device used for evaluating the soundness of concrete according to an embodiment of the present invention, showing an initial state in a striking method.

FIG. 2 is a front view showing a striking device used for evaluating the soundness of concrete according to one embodiment of the present invention, showing an initial state in a striking method.

FIG. 3 is a cross-sectional view illustrating a striking method used for evaluating the soundness of concrete according to an embodiment of the present invention, and shows a state (standby state) immediately before striking in the striking method.

FIG. 4 is a cross-sectional view showing a hitting device used for evaluating the soundness of concrete according to an embodiment of the present invention, showing a hitting state in a hitting method.

FIG. 5 is a cross-sectional view showing a striking device used for soundness evaluation of concrete according to another embodiment of the present invention;
3 shows an initial state in a hitting method.

FIG. 6 is a cross-sectional view showing a striking device used for evaluating the soundness of concrete according to another embodiment of the present invention,
3 shows an initial state in a hitting method.

FIG. 7 is a cross-sectional view showing a striking device used for evaluating the soundness of concrete according to another embodiment of the present invention,
3 shows an initial state in a hitting method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 hitting device 10 support plate 11 support 12 front plate 13 through-hole 14 rubber support 15 stopper 16 spring support 21 hemisphere 22 suction plate 23 rubber mounting portion 30 rubber body 40 electromagnet 41 pinion 42 rack 50 microphone 51 hood 52 fixed arm 53 Vinyl chloride pipe 54 Rubber pipe 55 Outer hard sponge pipe 56 Inner hard sponge pipe 57 Cork pipe 58 Buffer material 60 Compression spring 71 Steel ball 72 Suction plate 73 Spring mounting part 80 Tension rubber 90 Concrete surface

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiharu Inagawa 2-8-8 Hikaricho, Kokubunji-shi, Tokyo Inside the Railway Technical Research Institute (72) Inventor Hirotomo Matsubayashi 2-2-2 Nakamagome, Ota-ku, Tokyo 12 Japan Geophysical Exploration Co., Ltd. (72) Inventor Bundai Suzuki 2-1-2 Nakamagome, Ota-ku, Tokyo Japan Geophysical Exploration Co., Ltd. F-term (reference) 2G047 AA10 BA04 BC09 BC11 CA03 EA10 EA11 GA01 GA03

Claims (7)

[Claims] The present invention relates to a concrete soundness evaluation for evaluating the soundness of concrete by analyzing a striking sound generated when the surface of the concrete is hit, wherein: a front plate facing the surface of the concrete; A support plate installed on the face plate via a support, a hitting point having a spherical hitting point and hitting the surface of the concrete, and a rubber body having both ends installed on the front plate and the hitting head and pulled. An electromagnet provided on the support plate, for sucking the impact head and moving the impact head away from the front plate, wherein the stop of the attraction of the electromagnet causes the impact head to strike the surface of the concrete. A striking device used for evaluating the soundness of concrete. 2. A soundness evaluation of concrete for evaluating the soundness of concrete by analyzing a striking sound generated when the surface of the concrete is hitted, comprising: a front plate facing the surface of the concrete; A support plate installed on the face plate via a support, a hitting point having a spherical hitting point, hitting the surface of the concrete, and a compression spring disposed between the support plate and the hitting head and compressed. An electromagnet provided on the support plate, for sucking the impact head and moving the impact head away from the front plate, wherein the stop of the attraction of the electromagnet causes the impact head to strike the surface of the concrete. A striking device used for evaluating the soundness of concrete. 3. The hitting head is composed of a steel ball and a suction plate having a spherical or conical concave portion, and both ends of the rubber body are installed on the suction plate and the front plate, respectively. The impact device according to claim 1, wherein the steel ball is rotatable. 4. The hitting head comprises a steel ball and a suction plate having a spherical or conical recess, wherein the compression spring is disposed between the suction plate and the support plate. 3. The impact device according to claim 2, wherein the steel ball is rotatable. 5. A microphone having a cylindrical hood for collecting the impact sound is provided via a cushioning material, and the cylindrical hood is inserted into a vinyl chloride tube and the inside of the vinyl chloride tube. 5. A concrete sponge according to any one of claims 1 to 4, comprising a hard sponge tube having a rubber tube interposed therebetween, and a cork tube inserted in the hard sponge tube. Blow device used for degree evaluation. 6. A concrete soundness evaluation for evaluating the soundness of concrete by analyzing the sound of striking when the surface of the concrete is struck. A step of pulling toward the surface of the concrete by a tension spring or a step of pulling in a plurality of directions in parallel with the surface in a radial direction; A method for evaluating the soundness of concrete, comprising the step of: stopping the attraction of the electromagnet so that the hitting head that has been moved away hits the surface of the concrete. 7. A concrete soundness evaluation for evaluating the soundness of concrete by analyzing the sound of striking when the surface of the concrete is hit, wherein a hitting head having a spherical impact point is compressed by a compression spring. Extruding toward the surface of the concrete, causing the striking head in the extruded state to be attracted by an electromagnet, and moving away from the surface of the concrete; and A hitting method used for evaluating the soundness of concrete, comprising a step of hitting the surface of the concrete with a hitting head.