JPH1164121A - X-ray stress measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure three-dimensional stress distribution by x-ray stress analyzing method. SOLUTION: This x-ray stress measuring method is to estimate the stress of an object 3 to be measured by radiating white x-ray 15 to the object 3 to be measured and detecting x-ray 16 diffracted by the object 3 to be measured to detect the crystal lattice strain of the object 3 to be measured. Three- dimensional stress distribution of the object 3 to be measured corresponding to the three dimensional distribution of the crystal lattice strain of the object 3 to be measured is estimated by detecting three-dimensional distribution of the crystal lattice strain of the object 3 to be measured in the X, Y, and Z directions by successively changing the white x-ray 15 radiation parts of the object 3 to be measured in the XY plane while keeping the diffraction angle θ.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray stress measuring method, and more particularly to a technique capable of measuring a three-dimensional stress distribution in an XYZ direction of an object to be measured.

[0002]

2. Description of the Related Art In a conventional X-ray stress measurement method, an object is irradiated with low-energy monochromatic X-rays, X-rays diffracted by the object are detected, and the stress of the object is measured. ing. For example, when the amount of stress fluctuation on the XY plane of an object to be measured (for example, an iron plate) is an important characteristic, this is combined with the stress distribution in the depth direction (Z direction) of the object to be measured. 3
It is necessary to quickly measure the three-dimensional stress distribution by the X-ray stress measurement method.

[0003]

However, in the above-mentioned conventional example, since the stress of the object to be measured is measured with only one monochromatic X-ray energy, the information of the stress in the depth direction of the object to be measured is one. Therefore, the measured stress distribution is only two-dimensional in the XY directions. For this reason, in order to obtain a stress distribution in the depth direction of the object to be measured, it is necessary to sequentially convert the energy of the irradiated monochromatic X-ray, but this requires a significant structural change in the X-ray generator. . Therefore, an object of the present invention is to eliminate the above-mentioned disadvantages of the conventional example and to measure a three-dimensional stress distribution of an object to be measured with a simple device.
It is to provide a method for measuring a linear stress.

[0004]

Means for Solving the Problems In order to solve the above problems, the structure of the present invention is to irradiate an object with white X-rays and detect X-rays diffracted by the object. An X-ray stress measurement method for estimating stress of the object by detecting a crystal lattice strain of the object,
While keeping the diffraction angle constant, the white X-ray irradiation site of the object to be measured is sequentially changed on an XY plane to detect a three-dimensional distribution of crystal lattice distortion of the object to be measured in the XYZ directions, An X-ray stress measurement method characterized by estimating a three-dimensional stress distribution of the measured object corresponding to a three-dimensional distribution of crystal lattice strain of the measured object.

According to the X-ray stress measuring method of the present invention, the object is irradiated with white X-rays, and the X-ray diffracted by the object is detected, whereby the crystal lattice distortion of the object is detected. Is detected, the stress of the object is estimated, so that diffraction occurs at a portion having a depth corresponding to each wavelength of the white X-ray. For this reason, it is possible to obtain the distribution of the crystal lattice strain in the depth direction (Z direction) of the measured object. At the same time, while maintaining the diffraction angle constant, the white X-ray irradiation site of the object is sequentially changed on the XY plane, so that the distribution of the crystal lattice strain in the XY direction of the object can be obtained. . Therefore, detecting the three-dimensional distribution of the crystal lattice strain of the device under test in the XYZ directions and estimating the three-dimensional stress distribution of the device under test corresponding to the three-dimensional distribution of the crystal lattice strain of the device under test. Can be.

[0006]

FIG. 1 shows a measuring apparatus used for an X-ray stress measuring method according to an embodiment of the present invention.
Indicates a right side surface of a part of the one shown in FIG. This measuring device is capable of automatically measuring the stress of an object to be measured based on a predetermined procedure. Generally, the DUT 3 placed on the data base 2 (for example, a polycrystalline iron plate)
Is irradiated with white X-rays (X-rays having a spectrum having a continuous wavelength) 15 at a tilt angle ψ and a diffraction angle θ, X-rays of various energies are Bragg at the diffraction angle θ.
g) Selects a grating plane that satisfies the diffraction condition and diffracts it.
At a time, diffracted X-rays from various lattice planes (h, k, l) having plane indices such as the (2, 1, 1) plane can be obtained.

The main body 1 of the diffraction device is mounted on a frame (not shown) so as to be rotatable about a ψ axis 14a. Reference numeral 14 denotes a ψ-axis rotation control unit. An X-ray tube 11, an X-ray detector 12, and a positioning sensor 13 are attached to the diffraction device body 1. The X-ray tube 11 is a solid state semiconductor detector (SS).
D), and the X-ray intensity corresponding to the energy of the X-ray can be detected, so that the diffraction energy value for each diffracted X-ray 16 can be measured. Positioning sensor 13
In order to determine the relative position between the DUT 3 and the X-ray tube 11, the DUT 3 is irradiated with a laser beam 17 to measure the distance between the positioning sensor 13 and the DUT 3. .
The DUT 3 (for example, a polycrystalline iron plate) is placed on the reference table 2. The measurement surface of the device under test 3 is kept horizontal. The data base 2 is a table whose position can be adjusted in the XYZ directions, for example. In FIG. 2, reference numeral 3a denotes a horizontal surface to be irradiated with white X-rays, and 3b denotes a normal line perpendicular to the surface to be measured 3a.

The high-voltage power supply 4 is a power supply for the X-ray tube 11,
The capacity is 60kV, 50mA ~ 100kV, 30m
It is about A. The control unit 5 controls the high-voltage power supply unit 4, the ψ-axis rotation control unit 14, and the data processing unit 8. The signal converter 6 amplifies the analog output signal (indicating the intensity of each diffracted X-ray) of the X-ray detector 12 and converts it into a digital signal. The wave height analyzer 7 receives the digital signal from the signal converter 6, analyzes the height (peak energy) of the detected X-ray wave, and detects the distortion of the crystal lattice of the DUT 3. . The data processing unit 8 includes the wave height analysis unit 7
And a control signal is sent to the control unit 5.

In the energy dispersive X-ray stress measurement using the above apparatus, while keeping the diffraction angle θ and the inclination angle 一定 constant, the distance from the measured surface 3a is kept constant, and Scan the white X-ray 15 at the speed
The distribution of stress is analyzed by measuring the variation of the energy peak in line 16. As shown in FIG.
The wire tube 11 is provided at each measurement position (1, 2 to m−1,
m) is irradiated with white X-rays 15. The X-ray detector 12 detects X-rays 16 diffracted by the device under test 3. The strain of the crystal lattice is detected from the detected diffraction X-rays, and the stress corresponding to the strain of the crystal lattice can be estimated by multiplying the strain of the crystal lattice by an elastic constant (Young's modulus).

That is, the object to be measured 3 is set on the data base 2, the measured part is adjusted to the diffraction point, and the measured part is sequentially designated while controlling the posture of the measured surface 3a at right angles to the direction of the measured stress. (A (m / s). The detected diffracted X-rays are sequentially analyzed in energy by the wave height analyzer 7 and integrated for each channel for a specified fixed time (b (sec)), and a serial number is assigned. (S1, s2, ─sn).
{En (hkl) i} is the i-th set of diffraction peak analysis results for each lattice plane (hkl) of the data obtained by integrating the (ik) -th to (i + k) -th 2k data.
And The diffraction peak at zero stress ΔEn (hkl)
｝ ΔEn (hk)
l) Find i｝.

Diffraction peak at zero stress ΔEn (hkl)
o divided by ｛ΔEn (hkl) i｝ / ｛En (hkl)
｝ is calculated. This is (a × b × i) mm from the base point.
It can be said that this is a measure of the strain of the crystal lattice due to the stress in the direction orthogonal to the ψ axis in the vicinity of the advanced state, and the numerical value obtained by multiplying this by the X-ray elastic constant can be said to be a similar measure of the stress. When the diffraction peak at zero stress is unknown, a relative value with respect to the reference can be obtained by applying any En (hkl) i.

The effective penetration depth te of the X-ray diffracted at a certain crystal lattice plane from the surface of the object 3 changes according to the relationship of the equation (1) with respect to the diffraction angle θ. Where θ: diffraction angle ρ: density of DUT 3 μ: mass absorption coefficient of DUT 3

FIG. 3B shows the measurement results. The stress corresponding to each of the measurement positions is measured for each portion of the DUT 3 in the depth direction. The “grating plane” in FIG. 3B is a grating plane of the DUT 3 that satisfies the diffraction condition.

That is, the diffraction angle θ is made constant, and the arbitrary inclination angle ψ
, Successive diffraction peak energies En _ij are measured at desired positions (i, j). i and j are coordinates (i = 1 to n, j = 1 to m) indicating the position of the measurement point on the X-ray irradiation surface 3a. Assuming that the reference peak energy of a certain lattice plane (hkl) is E _no , the deviation rate Δd _ij of an arbitrary ij point with respect to the reference point of the lattice plane spacing in the direction of the inclination で can be expressed by equation (2). The deviation ΔσX _ij of the X-ray stress with respect to the reference point is given by the following equation (3)
Can be obtained by

[0015]

According to the X-ray stress measuring method according to the present invention, the stress distribution in the three-dimensional direction of the measured object can be precisely measured nondestructively without etching the surface of the measured object. Can be. For this reason, the three-dimensional distribution of the residual stress after processing of an iron plate or the like used for an automobile can be accurately measured.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an apparatus used for an X-ray stress measurement method of the present invention.

FIG. 2 is an explanatory view of a part of a side surface of the device shown in FIG. 1;

FIG. 3 is an explanatory diagram of the X-ray stress measurement method and measurement results.

[Explanation of symbols]

 3 DUT 11 X-ray tube 12 X-ray detector 15 Irradiation X-ray 16 Diffraction X-ray θ Diffraction angle

Claims (1)

[Claims] 1. An object to be measured is irradiated with white X-rays to detect X-rays diffracted by the object to detect crystal lattice distortion of the object to detect the X-rays. An X-ray stress measurement method for estimating stress, wherein the white X-ray irradiation site of the object is sequentially changed on an XY plane while the diffraction angle is kept constant, and the crystal of the object is measured. An X-ray stress measuring method comprising: detecting a three-dimensional distribution of lattice strain in the XYZ directions; and estimating a three-dimensional stress distribution of the device under test corresponding to the three-dimensional distribution of crystal lattice strain of the device. .