JP2936231B2 - Internal defect detection device for rubber and plastic materials - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting internal defects of a rubber / plastic material which non-destructively detects internal defects of a test material by ultrasonic waves.

[Related Art] As a method for non-destructively detecting a defect to be detected in a material, a method using ultrasonic waves is widely known. Ultrasonic defect detection, for example, is easier to operate than X-ray methods and the like, and has many advantages such as no need for labor such as film development and almost no danger to the human body. Used in numerous fields.

For example, as one method of such defect detection by ultrasonic waves, a so-called water immersion method in which a test material is immersed in a liquid and the ultrasonic waves are transmitted and received through the liquid is known.
It has been attracting attention as a method with good detection sensitivity and high reliability.

[Problems to be Solved by the Invention] However, in polymer materials such as rubber and plastic, the attenuation of ultrasonic waves due to absorption is severe, and the detection sensitivity to minute defects is often insufficient. For example, cross-linked polyethylene used as the main insulator of power cables called CV cables requires detection of micro defects of about several hundred μm, but in such a case, detection by conventional ultrasonic testing is not possible. This is not possible, and the advantages described above with ultrasound are often not exploited.

A recent study by the present inventors to solve this problem showed that when the temperature of a polymeric soft material was set to a high temperature of, for example, 40 ° C. or higher, the sensitivity of ultrasonic defect detection was improved compared to that at normal temperature. It is clear that it will be.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a device for detecting internal defects of a rubber / plastic material that can detect defects favorably by ultrasonic waves under high temperature conditions.

[Means for Solving the Problems] An apparatus for detecting an internal defect of a rubber / plastic material according to the present invention for achieving the above-mentioned object is provided by an ultrasonic probe from the outside to a test material made of a polymer material. An ultrasonic signal is transmitted, a reflected signal of the ultrasonic signal is received, and an internal defect of the test material is detected from the reflected signal. And the liquid is heated to a predetermined high temperature, and in the high temperature state, the test material is inspected from the entire circumference using a rotating mechanism.

[Operation] In the device for detecting internal defects of a rubber / plastic material having the above-described structure, a medium liquid is heated by a heating unit, and a test sample made of a polymer and an ultrasonic probe are heated via the heated liquid. In this state, detection is performed on the test material from the entire circumference.

[Example] The present invention will be described in detail based on an illustrated example.

FIG. 1 shows an embodiment of the present invention, in which a test material is crosslinked polyethylene as a main insulator of a CV cable. In FIG. 1, a liquid container 1 is filled with a liquid 2 serving as a medium, and a test cable C as a test sample is submerged in the liquid 2. A heating means 3 made of a nichrome wire or the like is provided. On the other hand, liquid 2
A water immersion ultrasonic probe 4 is provided in the vicinity of the liquid surface, and is connected to a drive / analysis device (not shown) via a lead wire 5. The tip of the probe 4 is in the liquid 2 and covered. Test cable C
Is oriented. The test cable C is supported by a bearing mechanism 6, and the bearing mechanism 6 is rotated by a handle 8 via a bevel gear mechanism 7.

In the above configuration, when the heating means 3 heats the liquid 2 in the liquid container 1 to, for example, 80 ° C., the temperatures of the cable under test C and the probe 4 also gradually rise, and after a sufficient time has elapsed, Almost the same predetermined temperature is reached. Here, the probe 4 is operated by the driving / analyzing device, and the ultrasonic signal is transmitted to the cable C to be measured. This ultrasonic signal propagates through the liquid 2 and enters the cable C to be tested. At this time, the signal reflected on the surface of the cable C to be tested or a defect to be detected propagates through the liquid 2 again and the probe 4. It is the same as the known water immersion flaw detection method that the drive / analysis device determines the presence / absence, depth, size, and the like of the defect to be inspected based on the round trip time and peak value of the received signal.

In the case where the test sample has a cylindrical shape such as a cable as in this embodiment, the test cable C is rotated by the handle 8 via the bearing mechanism 6 and the bevel gear mechanism 7, and the high-temperature liquid 2 The test cable C immersed inside can be easily rotated,
Inspection over the entire circumference of the cable under test C becomes possible.

However, at this time, the ultrasonic attenuation rate and the magnitude of the characteristic noise of the probe 4 in the test sample change depending on the temperature of the cable C to be tested and the temperature of the probe 4. That is, in the crosslinked polyethylene which is the material of the test cable C in this case, as compared with the case of normal temperature at a high temperature of 80 ° C., for example, the ultrasonic attenuation rate decreases, and the characteristic noise of the probe 4 also decreases. Defect detection sensitivity is improved.

Further, a control device for controlling the amount of heat generated by the heating means 3 and a temperature measuring means for measuring the temperature of the liquid 2 are provided, and if necessary, a heat retaining means is provided so that the set temperature matches the temperature of the liquid 2. It is preferable to control the calorific value of the heating means 3 in this way, so that more stable and reliable measurement can be performed. At this time, as the volume of the liquid 2 is increased, the heat capacity of the temperature control target increases, so that accurate temperature control can be easily performed.

In a measurement performed by the present inventors using a crosslinked polyethylene resin as the test material, the relationship between the depth and the size of the test defect at the detection limit is represented by a curve A in FIG. Of the relationship, the device of the present invention
In the case of detection at a high temperature of ° C., the curve B was improved in the case of a spherical defect, and the curve C was improved in the case of a planar defect. That is, at room temperature, for example, 700μ exists at a depth of 20mm.
It was confirmed that a defect having a size of m was the detection limit, whereas a high temperature of 80 ° C. could detect a defect of 100 to 200 μm at a depth of 20 mm at a high temperature of 80 ° C.

Although water may be used as the liquid 2, it is preferable to select a substance having a high boiling point, such as silicon oil, for example, since generation of air bubbles at a high temperature hinders measurement.

[Effect of the Invention] As described above, the apparatus for detecting internal defects in a rubber / plastic material according to the present invention detects defects as a result of heating a test material made of a polymer material and an ultrasonic probe via a liquid. The sensitivity is improved, and moreover, highly reliable and accurate detection of the test material can be performed from all around.

[Brief description of the drawings]

The drawings show an embodiment of the apparatus for detecting internal defects in rubber and plastic materials according to the present invention. FIG. 1 is a configuration diagram, and FIG. 2 is a graph showing measurement results. Reference numeral 1 denotes a liquid container, 2 denotes a liquid, 3 denotes a heating means, 4 denotes a probe, and C denotes a cable to be tested.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-98358 (JP, A) JP-A-60-46407 (JP, A) Fully open 48-18565 (JP, U) Really open 89857 (JP, U) Japanese Utility Model Showa 61-140963 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 29/00-29/28

Claims (1)

(57) [Claims] An ultrasonic signal is transmitted from an external device to a test material made of a polymer material via an ultrasonic probe, a reflected signal of the ultrasonic signal is received, and the test signal is obtained from the reflected signal. In an apparatus for detecting an internal defect of a material, the test material and the ultrasonic probe are settled in a liquid, the liquid is heated to a predetermined high temperature, and the rotation mechanism is used in the high temperature state using a rotating mechanism. An apparatus for detecting internal defects in a rubber or plastic material, wherein an inspection is performed on a test material from all around.