JPH0259644A - Detector with blow method for structural change - Google Patents

Abstract

PURPOSE:To detect an abnormality for an object to be inspected in a high accuracy and without a skill by detecting the pulse widths of pulse waveforms for the forces to act upon a hammer and a surface of the object to be inspected at the time of blowing with the hammer. CONSTITUTION:An electrical signal with the pulse waveform which is detected by a force detecting sensor 2 mounted on the hammer 1 for the blow is induced into a calculating circuit 8 for the pulse width wherein converted to a signal having the value proportional to the pulse width. Then, this signal is induced into an arithmetic circuit 3 for a spring constant, wherein the spring constant K is calculated by an equation, K=m.pi<2>/T<2> (where, T is a pulse width and m is a hammer mass), and converted to the signal shown as the value of K. In the first place, when a normal part is being blowed with the hammer 1, a value K0 is stored as the reference value in a storage part 5 for the reference spring constant by a switch 4. When the inspection is made, a ratio of the values C1=K/K0 is calculated by means of inducing the signals to a comparator circuit 6 to compare the signal shown by the spring constant K and the reference value K0. This value C1 is inputted to a display device 7, and the variation from the normal value is informed to the outside with a light or a sound.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to honeycomb board peeling M inspection, tile peeling inspection,
This invention relates to an impact type structural change inspection device that is used for a wide range of purposes, such as inspecting the occurrence of cracks in materials and further inspecting the presence or absence of joists in wallboards.

[Conventional technology]

Generally speaking, when you strike the surface of an object with a hammer, you often experience that the thickness of the object changes, or if there is a support inside, the tone changes.

This is because the struck object vibrates and generates sound when struck, but when the structure changes due to peeling or the like, the frequency and amplitude of the sound change.

The most commonly used method is exactly the same as this one, in which an expert hits the specimen with a small hammer called a test hammer or coin tap hammer, and the change is detected by the person's ears. It is.

However, the disadvantages of this method are that only an experienced person can distinguish it, and it takes a long time when inspecting a large area, but the human nerves may get tired and it becomes impossible to distinguish, or the normal part and the defective part may be separated. If the test object is in a dangerous location, people may not be able to go there to measure it, and it may not be possible to automate it.

On the other hand, in a mechanized version of the above manual method, the striking is performed by a machine, and the sound generated is converted into an electrical signal by a microphone, which is then used for frequency analysis or voice recognition to distinguish the tone. There are things that can be automated.

However, the drawbacks of mechanization are that the equipment is large and expensive, and the method for distinguishing between normal and abnormal parts is complicated. There are things that must be done every time the test object changes.

Therefore, as a countermeasure, it is possible to detect abnormalities such as changes in the structure of the object to be inspected by detecting the force acting between the hammer and the object to be inspected when the hammer hits the object, or by detecting the pulse width of the pulse waveform of the acceleration of the hammer itself. can be easily detected without
The invention of JP-A-63-58124 relates to a compact and inexpensive impact type structural change detection device, and the impact type structural change detection device in this invention is a hammer for impact equipped with a force detection sensor or an acceleration detection sensor. It consists of a pulse width calculation circuit that detects the pulse width of the force or acceleration pulse waveform when the test object is struck by the reference test object. A more preferable configuration is to add a reference pulse width storage unit to store the reference pulse width, a comparison circuit to compare the pulse width of the pulse waveform of the force or acceleration of the object to be inspected and the reference pulse width, and a display device for displaying the comparison result. .

Therefore, in the above-mentioned known invention, the time period during which the hammer with hammer mass m is in contact with the object to be inspected, that is, the pulse width T
is the time it takes for the displacement to move positively and return to its original position, so if pi is expressed as π, the pulse width T = πφm /
K, and the pulse width T is determined only by the mass m of the hammer and mainly the spring constant of the object to be inspected.

Therefore, if the pulse width T, which is the contact time, is measured from the waveform of the output electric signal of the force detection sensor or acceleration detection sensor, the above T-πJ';'J'7T'
The spring constant K of the object to be inspected can be calculated from the equation C.

Therefore, the present inventors proposed that T=
Since we focus on the spring constant K in the equation for πr and convert this second spring constant K as the main component, the resolution is higher than when comparing by the time T itself, as in the equation for T - π, and the above-mentioned The present invention was achieved by paying attention to the fact that the detection accuracy is improved compared to the known example of JP-A-63-581'24.

[Purpose of the invention]

The present invention has been made for the purpose of providing a percussion type structural change detector that can detect abnormalities such as structural changes of an object to be inspected without requiring any skill, with higher detection accuracy than the conventional one.

[Summary of the invention]

In order to achieve the above object, the impact type structural change detection device of the present invention has a pulse width T of a pulse waveform of force or acceleration when an object to be inspected is impacted by a hitting hammer equipped with a force detection sensor or an acceleration detection sensor. In other words, a pulse width calculation circuit is provided to detect the time period during which the hammer is in contact with the object to be inspected, and the pulse width T is expressed by the Hane constant K, the hammer mass m, and the pi ratio π. −π
v] "The formula for the spring constant is provided with a comparison circuit that compares the spring constant with a reference spring constant and a display device for displaying the comparison result, and the formula for the spring constant is In this case, since the pulse width, that is, the contact time T becomes effective in □, the expression for the pulse width T has higher resolution and detection accuracy than when comparing by T itself.

〔Example〕

The present invention will be described in detail below with reference to the drawings, which are block diagrams of an impact type structural change detection device in one embodiment of the present invention.

First, this device has a force detection sensor 2 or an acceleration detection sensor attached to a hammer 1 for striking.In the case of force detection sensor 2, this is attached near the tip of hammer 1, but the acceleration detection sensor is attached to the hammer 1. When used, it can be installed in any position on the hammer ■.

Note that the hammer 1 may be an automatic hammer that automatically strikes the object 10 to be inspected, or may be a hammer that strikes the object 10 manually, since the discrimination method of the present invention does not depend on the strength of the strike. This is due to a number of things.

Next, the pulse waveform electrical signal detected by the force detection sensor 2 is introduced into a pulse width calculation circuit 8 and converted into a voltage or digital signal represented by a value proportional to the pulse width'.

Therefore, when the hammer 1 is striking the normal part, a value proportional to the pulse width is stored in the reference pulse width storage section by an instruction using a switch (not shown).
At the time of inspection, the pulse width signal and the stored reference pulse width value are compared and the difference or ratio between them is calculated. That is, the pulse width T is as follows, where m is the hammer mass and π is the circumference, T=Ewama, as described in the above-mentioned Japanese Patent Application Laid-Open No. 58124/1983.

Therefore, in the present invention, a spring constant K, which is calculated using the above equation of T=2, is introduced into the spring constant calculation circuit 3, and is converted into a voltage or a digital signal represented by a value of K that is proportional to the spring constant K.

Therefore, when the hammer 1 is striking the normal part, the switch 4 is used to cause the reference spring constant storage section 5 to store a value of 0, and the stored reference value is set to 0.

At the time of inspection, the spring constant signal is led to a comparator circuit 6 that compares the reference value with 0, and the ratio of the values, that is, C,=/KO, is calculated.

This value C3 is led to the display device 7, and a change from the normal value is notified to the outside by light or sound.

Using the conventional example of pulse width display and the impact-type structural change detection device between spring constants, aluminum honeycomb surface plates of various thicknesses were inspected, and a normal part and a defective part of 1 inch in diameter were detected. The table below shows a comparison of experimental values.

As mentioned above, the comparison between the normal part and the defective part is based on the pulse width (T
) It has been found that displaying the spring constant (K) improves resolution because it can be expressed with a larger number.

Note that the above spring constant (K) can actually be expressed as a reciprocal of the spring constant, resulting in a larger numerical ratio.

〔Effect of the invention〕

As explained above, in the conventional method of discriminating changes based on the sound generated by the object to be inspected by impact, when automatic discrimination is performed electrically, complex circuits such as frequency analysis and pattern recognition are used. On the other hand, in the device of the present invention, since only the pulse width is measured, the circuit is extremely simple, it can be formed into a Pokeso I-sized device that can be held with one hand, and it can be provided at low cost.

Furthermore, since the pulse width does not change depending on the magnitude of the striking force, no skill is required even when striking manually, and automatic striking can be easily performed mechanically.

Furthermore, since the contact time due to impact is very short, there is an advantage that a wide area can be inspected at high speed by mechanically performing automatic impact at high speed.

In particular, the device of the present invention has the advantage that since it is displayed in terms of a spring constant, it can be expressed in a larger number than in the pulse width, which improves the resolution accordingly and improves the detection accuracy of the device. .

[Brief explanation of the drawing]

The drawing is a configuration diagram of an impact type structural change detection device according to an embodiment of the present invention. 1... Hammer, 2... Force detection sensor 3...
Spring constant calculation circuit, 5... Reference spring constant storage section, 6.
... Comparison circuit, 7 ... Display device, 8 ... Pulse width calculation circuit, 10 ... Test object.

Claims (1)

[Claims] A pulse width calculation circuit is provided to detect the pulse width T of the pulse waveform of force or acceleration when a hammer of mass m to which a force detection sensor or acceleration detection sensor is attached is used to strike an object to be inspected. A spring constant calculation circuit that converts the equation of pulse width T = π√ (m/K) expressed in π into the equation of K = m (π^2/T^2) with the spring constant K as the main component. An impact-type structural change detection device comprising a comparison circuit for comparing a spring constant and a reference spring constant stored in a reference spring constant storage unit, and a display device for displaying the comparison result.