JPH0815240A - Residual stress measuring device - Google Patents

Abstract

PURPOSE:To provide a measuring device for measuring the residual stress of a material comparatively simply and correctly by using an ultrasonic wave. CONSTITUTION:A residual stress measuring device comprises a rotary jig 10 and a slide jig 6. The rotary jig 10 is so constructed that a rotatable ring is fitted to a base plate. The slide jig 6 is fixed to the ring and right and left screws 8 are mounted. An ultrasonic oscillator 1 and geophone 2 can be symmetrically slid within the ring by combination of rotation and sliding. The directions of the maximum main stress sigma1, and orthogonal main stress(2,are measured. Concerning the respective directions, the sound speed V, and V, at the oscillating angle theta of the primary incoming and reflected waves of ultrasonic waves and the sound speeds V1 and V2' at the oscillating angle theta' of the secondary incoming and reflected waves in the same position are measured to calculate residual stress (sigma1-sigma2) from the sound speed differences (V1-V2) and (V1'-V2').

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of measuring residual stress of various materials using ultrasonic waves and a measuring apparatus therefor, and particularly to measuring residual stress inside the surface of a material relatively easily and accurately.

[0002]

2. Description of the Related Art Conventionally, various physical methods have been used as a method for qualitatively knowing the residual stress of various materials. Also,
Mechanical methods and X-ray methods are used as quantitative methods. Among them, the X-ray method is to measure the displacement of the crystal lattice of the material by the diffraction image of the scattered X-ray generated by projecting the X-ray on the surface of the material to be measured, and calculate the stress value from the result. , Has the advantage that it can measure the material nondestructively.

[0003]

However, the above-mentioned X
The line method cannot avoid the influence of material anisotropy caused by, for example, the manufacturing history of the material. Further, the measurement depth is limited to 300 Å at most, which is extremely close to the surface, and it cannot be said that this is the residual stress of the material.

[0004]

In view of the above problems, the present inventor has conducted research based on an idea completely different from the conventional technique, and utilizes the birefringence phenomenon of transverse ultrasonic waves to
We succeeded in measuring the residual stress of the material.

The ultrasonic waves used are shear horizontal shear waves (SH).
A wave), it is preferable that the pulse wave frequency 0.5~100MH _Z.

First, an ultrasonic wave is oscillated toward the inside of the measured material from an oscillator placed in close contact with one surface of the measured material coated with the coupling agent. Then, while receiving the reflected wave from the material to be measured by the geophone, gradually oscillate the ultrasonic wave and the vibration receiving position, and measure the direction in which the received reflected wave has the maximum value to be measured. Specify the direction of maximum principal stress σ ₁ of the material.

Next, the direction of the principal stress σ ₂ orthogonal to the direction of the maximum principal stress σ ₁ is measured by rotating the rotating jig, and 2
Identify the two principal stress directions.

With respect to each of the direction of the obtained maximum principal stress σ _{1 and} the direction of the principal stress σ ₂ orthogonal thereto, the sound velocity V at the oscillation angle θ of the primary incident reflected wave of the ultrasonic wave.
₁ and V ₂ and the oscillating angles are changed at the same positions, and the sound velocities V ₁ ′ and V ₂ ′ at the oscillating angle θ ′ of the secondary incident reflected wave are measured, and the sound velocity difference (V ₁
-V ₂ ) and (V ₁ ′ -V ₂ ′), the residual stress (σ ₁ −
Calculate σ ₂ ).

The material of the shoe forming a part of the ultrasonic oscillator and the geophone is acrylic, polycarbonate,
Epoxy, vinyl chloride, metal, quartz, SiC, graphite, zirconia, TiC-based cermet, WC-based cemented carbide and the like are used.

The residual stress measuring device is composed of a rotating jig which is fitted to a substrate and is composed of a rotatable ring, and a slide jig which is fixed to the ring. The slide jig has an ultrasonic oscillator and a vibration receiving device. Be sure to wear a vessel. The distance between the two is symmetrically separated or approached by the left and right screws provided on the slide jig.

[0011]

The reason why the type of ultrasonic wave used in the present invention is preferably shear horizontal shear wave (SH wave) is because the shear wave has a characteristic of propagating in a perpendicular direction. This is because the horizontal wave does not cause a mode conversion from a transverse wave to a longitudinal wave when reflected on the bottom surface of the material, and has high measurement accuracy.

[0012] why the ultrasonic frequency was preferably in the range of 0.5～100MH _Z is, if the frequency is too small, decreases the measurement accuracy wavelength too long, the frequency is too large in the opposite This is because the wavelength becomes too short and is easily attenuated. More preferably, the frequency 0.
A 5～20MH _Z, in this range, a particularly good Naru measurement accuracy, damping prevention effect is exhibited.

The reason why the waveform of ultrasonic waves is preferably a pulse wave is that the material to be measured can be treated as an infinite medium and that the ultrasonic waves interfere with each other in a complicated manner when reflected on the bottom surface of the material. This is because it has a preventive effect.

The material of the shoe that constitutes part of the ultrasonic oscillator and the geophone has an appropriate acoustic impedance difference from the material to be measured, is transparent, and is made to come into contact with the material to be measured. While sliding, a material with good wear resistance is selected.

One surface of the shoe constituting a part of the ultrasonic oscillator and the geophone is assumed to have a shape capable of closely adhering to the surface shape of the material to be measured. For example, if the material surface is flat, one surface of the shoe is flat, and if it is a cylindrical outer peripheral surface, the one surface of the shoe is a concave surface with the same curvature, so that ultrasonic waves propagate without being attenuated. It can be so.

Under the above-mentioned conditions, the measurement range of the residual stress of the material to be measured finally obtained by the measurement means of the present invention is the measurement range of the residual stress of the ultrasonic oscillator and the geophone in the width direction. Is the range in contact with, and the range from the material surface to the reflection point of the ultrasonic wave in the depth direction. Since the obtained measured values are average values in a wide range as described above, the residual stress value of the material to be measured is highly reliable as compared with the conventional measuring method.

[0017]

Next, an embodiment of the residual stress measuring device of the present invention will be described with reference to the drawings.

In FIG. 1 and FIG. 2, the ultrasonic oscillator 1 and the ultrasonic receiver 2 are fixed to two mounting plates 3, respectively. A dovetail groove 4 is provided on the rear surface of the mounting plate 3, and an arm 5 extends rearward. The slide jig 6 includes a base 7, left and right screws 8 attached to the base 7 and rotatable,
The slide rail 9 is fixed to the base 7. The dovetail groove 4 of the mounting plate 3 is fitted to the slide rail 9, and the screw hole formed in the arm 5 is screwed to the left and right screws 8.

By making the pitches of the left and right screws 8 the same on the left and right and assembling the respective components symmetrically, the ultrasonic oscillator 1 and the vibration receiver 2 can be symmetrically separated or approached by rotating the left and right screws 8. Like

The slide jig 6 is the ring 1 of the rotary jig 10.
Fixed to 1. The ring 11 is fitted in a ring-shaped base plate 12 in the same manner and is rotatable. If the ultrasonic oscillator 1 and the geophone 2 are arranged symmetrically with respect to the center of the rotating jig 10, the ultrasonic oscillator 1
The geophone 2 can be moved to an arbitrary position within the inner diameter of the ring 11 by combining turning and sliding.

FIG. 3 is a schematic diagram showing an embodiment of the oscillator 1 (or the geophone 2). The outer shell is formed of a box-shaped shoe 13, and the inner surface of the bottom surface 14 thereof partially projects in a semicylindrical shape. A contactor 15 formed so that its tip comes into surface contact along the surface of the protrusion is incorporated, and a cable 16 extends outward. By operating the set screw 18 on which the cursor 17 is mounted, the contactor 15 can be swung about the central axis of the semi-cylindrical protrusion, and the angle of the oscillation (or vibration receiving) direction can be adjusted. You can do it.

The bottom surface 14 of the shoe 13 has a material 19 to be measured.
Is a flat surface, and if the measured material 19 is a curved surface, the curved surface has the same curvature as the curved surface. Shoe 13
A coupling agent is applied between the bottom surface 14 and the material to be measured 19 so that ultrasonic waves can propagate into the material to be measured 19 without being attenuated. The material of the shoe 13 is acrylic, polycarbonate, epoxy, which has a proper acoustic impedance difference and transparency, and has wear resistance.
Vinyl chloride, metal, quartz, SiC, graphite, zirconia,
Suitable are TiC-based cermet and WC-based cemented carbide.

4 and 5 are schematic views for explaining the principle of the present invention.

Now, ultrasonic waves are oscillated from the oscillator 1 toward the material to be measured 19, and while the reflected wave from the bottom surface of the material to be measured 19 is received by the geophone 2, the oscillator 1 and the geophone 2 are gradually slid. It is assumed that the reflected wave has the maximum value when it is moved to the state shown in FIG. At this time, the direction of the maximum principal stress σ ₁ inside the material to be measured and the direction of another principal stress σ ₂ orthogonal thereto are as shown in FIG. 4 (b).

FIG. 4A is a left side view of FIG. 4B, where the oscillation angle of the primary incident reflected wave at the above position is θ and the sound velocity is V ₁ . Next, the oscillation angle is adjusted to oscillate and receive the secondary incident reflected wave based on the birefringence phenomenon in which the reflection is repeated in the order of the bottom surface to the top surface to the bottom surface of the measured material 19. At this time, the oscillation angle is θ ′ and the sound velocity is V ₁ ′.

After that, the ring 11 is turned 90 degrees to bring it into the state shown in FIG. 5, and the same measurement as above is repeated.
FIG. 5A is a front view of FIG. 5B. The sound velocity at the oscillation angle θ of the primary incident reflected wave is V _2, and the sound velocity at the oscillation angle θ ′ of the secondary incident reflected wave is V ₂ ′. At this time,
If the substrate 12 is engraved with angle scales, it is easy to operate.

[0027] When the above-mentioned measurement, ultrasonic wave oscillation, a shear horizontal waves of transverse waves of frequency 0.5~100MH _Z (SH waves), and is preferably a pulse wave.

The residual stress is calculated from the following equations 1 and 2. The speed of sound V ₀ is obtained by measurement of the sample in the natural state (non-loaded state) of the measured material 19, and is the average speed of the speeds of sound V ₁ and V ₂ at this time. The sound speed V ₀ ′ is also the sound speed V ₁ ′ and the sound speed V ₂ ′ obtained by the measurement of the same sample as described above.
Is the average speed of. C _ik is the elastic modulus of the material crystal, S
_ik is an elastic coefficient, which is a constant separately obtained from experiments or calculations.

[0029]

[Equation 1]

[0030]

[Equation 2] However,

[0031]

(Equation 3)

[0032]

[Equation 4] Calculated from the simultaneous equations of Equations 1 and 2 (σ ₁ −σ ₂ )
Is the required residual stress.

FIG. 6 shows an embodiment of the system of the residual stress measuring apparatus of the present invention, which is constructed as a whole by connecting an ultrasonic pulse oscillation and vibration receiving apparatus, a sound velocity measuring apparatus and a computer. The ultrasonic pulse oscillating and vibration receiving device is configured by functions such as synchronous pulse oscillating, ultrasonic pulse oscillating, amplifying, and zero-cross time detection.

[0034]

INDUSTRIAL APPLICABILITY As described above, the residual stress measuring method and the measuring apparatus thereof according to the present invention provide an unprecedented method of measuring residual stress of various materials using ultrasonic waves. It has a feature that it can measure even inside the surface layer, and can be measured relatively easily and accurately.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a residual stress measuring device of the present invention.

FIG. 2 is a front view of a vertical cross section including the center of FIG.

FIG. 3 is a front view showing an embodiment of an oscillator (or a geophone).

FIG. 4 is an explanatory view of the principle of the present invention, (a) is a left side view,
(B) is a plan view.

FIG. 5 is an explanatory view of the principle of the present invention, (a) is a front view,
(B) is a plan view.

FIG. 6 is a diagram showing an example of a system configuration relating to the residual stress measuring device of the present invention.

[Explanation of symbols]

 1 Oscillator 2 Geophone 6 Slide jig 8 Left and right screws 10 Rotating jig 13 Shoe 15 Contactor 16 Cable 19 Material to be measured

[Procedure amendment]

[Submission date] February 24, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

FIG.

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 5]

[Figure 6]

Claims (6)

[Claims] 1. A material to be measured 19 which oscillates ultrasonic waves toward the inside of the material to be measured 19 from an oscillator 1 which is placed in close contact with one surface portion of the material to be measured 19 to which a coupling agent is applied. While the reflected wave from 19 is being received by the geophone 2, the oscillating position of the ultrasonic wave is gradually slid, and the direction in which the received reflected wave takes the maximum value is measured to obtain the measured material 19
After determining the direction of the maximum principal stress σ ₁ of the two, the rotating jig 10 is rotated to measure the direction of the principal stress σ ₂ which is orthogonal to the direction of the maximum principal stress σ _1. And the acoustic velocities V ₁ and V _{2 at} the oscillation angle θ of the primary incident reflected wave of the ultrasonic wave in the directions of the maximum principal stress σ ₁ and the principal stress σ ₂ orthogonal to the maximum principal stress σ ₁ and The oscillation angle is changed at the same position, and the oscillation angle of the secondary incident reflected wave is θ '
Sound velocities V ₁ ′ and V ₂ ′ are measured, and sound velocity differences (V ₁ −V ₂ ) and (V ₁ ′ −) obtained from the measurement results are measured.
A residual stress measuring device using a birefringence phenomenon, which is adapted to calculate a residual stress (σ ₁ −σ ₂ ) from V ₂ ′). 2. The type of ultrasonic wave is shear horizontal wave (S
The residual stress measuring device according to claim 1, wherein the residual stress measuring device is an H wave. 3. The frequency of ultrasonic waves is 0.5 to 100 MH.
It is _Z , The residual stress measuring device of Claim 1 and Claim 2 characterized by the above-mentioned. 4. The residual stress measuring device according to claim 1, wherein the ultrasonic wave is a pulse wave. 5. The material of the shoe 13 forming part of the ultrasonic oscillator 1 and the geophone 2 is acrylic, polycarbonate, epoxy, vinyl chloride, metal, quartz, Si.
2. C, graphite, zirconia, TiC-based cermet, WC-based cemented carbide, etc. are used.
~ The residual stress measuring device according to claim 4. 6. A rotating jig 10 is constituted by fitting a rotatable ring 11 to a substrate 12, and the ring 11 is provided.
A slide jig 6 is fixed to the slide jig 6, and the ultrasonic oscillator 1 and the geophone 2 are attached to the slide jig 6.
The residual stress measuring device according to any one of claims 1 to 5, characterized in that the distance between the two can be symmetrically separated or approached by the left and right screws 8 incorporated in the slide jig 6. .