JPS6255625B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for ultrasonic flaw detection of a welded part of a material to be flawed. )
The present invention relates to an ultrasonic flaw detection device equipped with an automatic gate position setting mechanism that automatically determines the gate position in accordance with changes in the gate position.

Conventionally, an ultrasonic flaw detection device in which a gate position is automatically set is known from Japanese Patent Publication No. 52-43597 (hereinafter, the ultrasonic flaw detection device described in this publication will be referred to as the known device). The configuration of the known device includes an oscillator that oscillates at a frequency corresponding to the speed of sound, and a preset counter that counts signal pulses from this oscillator to determine the starting point of the gate. Another oscillator is provided which outputs one pulse every time the object moves a predetermined distance from As the contact moves forward and backward, the count value of the preset counter is increased or decreased to change the starting point of the gate, so that a gate suitable for the welding area can always be automatically set.

However, the known device has the following problems.

(1) The configuration circuit of the known device is complicated.

(2) In Fig. 1 explaining the gate start point of the known device, the _P1 point is set at t/2cosθ (t: plate thickness, θ: refraction angle of the probe), but in reality Looking at the welded part, the weld metal width L varies depending on the groove shape and other various welding conditions. Therefore, if the weld metal width becomes wider than the initial weld metal width, the initially set starting point _P1 of the gate will enter the weld metal part as shown in Figure 2, and conversely, the weld metal If the width becomes narrower, the starting point P ₁ of the gate will be the third
As shown in the figure, it ends up entering the base material, making it impossible to perform a correct evaluation.

(3) The automatic setting of the gate position in the known device uses an oscillator that oscillates at a frequency corresponding to the speed of sound propagating through the material to be tested. In this case, if the material of the welded part frequently changes, the initial gate position setting conditions will result in deviations in the gate position.

As a result of research, the inventors have developed a device that solves these problems. In other words, the gist of the present invention is to provide a circuit that changes the gate start output voltage every time the probe distance changes by a predetermined amount as the probe moves, and to automatically adjust the gate position based on this voltage change. This is where I tried to change it. This will be explained in detail below with reference to FIG.

FIG. 4 is a diagram in which oblique angle flaw detection is performed using the probe 1 having a refraction angle θ on a material 2 to be tested having a thickness t. Normally, flaw detection of welded parts is carried out over the entire area on one or both sides between 0.5S and 1S. The above-mentioned S represents the distance from which the ultrasonic wave is incident, hits the back surface, is reflected, and reaches the front surface. Here, regarding the probe position in FIG. 4, if Y ₁ -Y ₂ =Y ₂ , the probe will move over the entire Y area. By moving the entire area of Y, the probe distance W to the weld becomes 2t/cosθ - t/cosθ = t/cosθ, and the gate start point moves from t/cosθ to 2t/cosθ during flaw detection. I will do it.

By the way, the gate width only needs to be kept constant, so if the gate start point is determined, the gate end point is automatically determined. Therefore, it is important to be able to automatically set the gate start point according to the probe distance.

FIG. 5 is a block diagram for automatically setting the gate start point of the apparatus of the present invention. In FIG. 5, first, the voltage at the reference point position of the probe for flaw detection is set in the voltage setting device 6.

Next, the moving distance from the flaw detection starting reference point is measured using the probe position detection signal A from the probe position detector attached to the probe, and the change in the probe distance due to the moving distance is measured. Voltage divider 4 that outputs a proportional voltage
The voltages output from the voltage divider 4 and the voltage setter 6 are offset by the voltage adder 5. For example, in Figure 4, the flaw detection starting reference point is set to point E,
Assume that the probe is moved in the direction from point E to point D. The set voltage of voltage setting device 6 at point E now is Va
When the probe moves 1 mm, voltage divider 4
Assuming that a voltage of Vb is output from Vb, when the probe moves by Ymm, the voltage adder 5 outputs a voltage of Va+YVb. The voltage of the voltage adder 5 is then input to a voltage comparator 7. The sweep voltage of the flaw detector (the voltage displayed on the cathode ray tube) is also input to the voltage comparator 7 from B, so the input voltage from the voltage adder 5 and the sweep voltage from the flaw detector are compared here. , a sweep voltage equal to the voltage adder input voltage is taken out and output as a gate start pulse.

In other words, if the probe moves Ymm, Va+
A sweep voltage corresponding to YVb is taken out from C as a gate start pulse output. A time chart of this operation is shown in FIG. In FIG. 6, sweep voltages are shown. is the flaw detection starting reference point E
The output voltage of the voltage setting device in , V, indicates the gate start pulse voltage when the probe moves Ymm from the flaw detection start reference point E. is the flaw detection starting reference point E
The gate pulse output at the point shows the gate start pulse output when the probe moves Ymm from the flaw detection start reference point E. From this, the gate start point moves from G ₁ to G ₂ . become.

Note that the probe position detection signal provided to the voltage divider 4 is obtained by an encoder, potentiometer, etc. attached to the probe. The start position of the gate is determined by the circuit of the present invention described above, but the gate end position is automatically determined by providing a circuit following the gate start output C to determine the gate width.

Although the configuration of the apparatus of the present invention is as described above, the following unique effects can be obtained by implementing the present invention.

(1) The circuit configuration is extremely simplified, making maintenance, inspection, and maintenance extremely easy, and can contribute to accurate flaw detection and evaluation.

(2) Even if the material to be tested contains materials with different weld metal widths, if the reference point for starting flaw detection is clearly defined each time, the appropriate gate start point can be automatically set.

(3) Even if the sound velocity changes due to different materials being tested, it is possible to eliminate errors in the gate setting position by adjusting the slope of the sweep voltage (gate start pulse) determined in advance. This can be prevented from occurring.

(4) With the simplification of the circuit configuration, the entire ultrasonic flaw detection device can be made smaller and lighter, and the workability of ultrasonic flaw detection can be improved.

[Brief explanation of the drawing]

Figures 1, 2, and 3 are diagrams explaining the inconvenience of determining the gate start point in known devices, and Figure 4 is a diagram illustrating the scanning method of the probe when detecting flaws in welded parts. 5 is a diagram showing an automatic gate position setting circuit according to the present invention, and FIG. 6 is a time chart showing the operation of the circuit according to the present invention. 1... Probe, 2... Material to be tested, 3... Welding section, 4... Voltage divider, 5... Voltage adder, 6... Voltage setting device, 7... Voltage comparator.

Claims (1)

[Claims] 1. In an ultrasonic flaw detection device in which a gate position is automatically set as the probe distance changes when testing a welded part of a material to be flaw-detected, a voltage proportional to the change in the probe distance is output. a voltage divider, a voltage setter that sets an initial voltage at the flaw detection starting reference point position of the probe, a voltage adder that offsets the output of the voltage divider voltage and the voltage setter voltage, and an output from the voltage adder. 1. An ultrasonic flaw detection device for a welded part, comprising a voltage comparator that compares the voltage detected by the flaw detector with the sweep voltage from the flaw detector and outputs a gate start pulse.