A short wavelength characteristic x-ray diffraction near-surface residual stress nondestructive testing device and method

Abstract

This invention provides a short-wavelength characteristic X-ray diffraction near-surface residual stress nondestructive testing device and method. The incident X-rays and diffracted X-rays are collimated by an incident collimator and a receiving collimator, respectively. Both rays are parallel light with rectangular beam cross-sections, exhibiting high positioning accuracy along the axis of sample thickness movement. The method includes the following steps: testing the diffraction peaks of a stress-free powder standard sample from its surface to its interior, and recording the diffraction peak P at location i. i The average peak value P was determined by the internal diffraction peaks of the stress-free powder standard. avg Based on the standard, according to formula m i =P i / P avg Calculate the spurious shift correction factor m of the diffraction peak from the surface to the interior i region of the stress-free powder standard. i Based on the diffraction peak spurious shift correction factor m i Correction yielded the sample diffraction peak P' i试样 and the diffraction peak P' of the stress-free reference sample i无应力参考样品； Calculate the near-surface residual stress. The method described in this invention enables non-destructive testing and analysis of the near-surface residual stress in materials / workpieces.

Description

Technical Field

[0001] This invention belongs to the field of X-ray diffraction detection technology, specifically relating to a short-wavelength characteristic X-ray diffraction near-surface residual stress nondestructive testing device and a method for nondestructive testing of near-surface residual stress. Background Technology

[0002] Short-wavelength characteristic X-ray diffraction technology can be used to non-destructively detect residual stress, texture and phases inside materials / workpieces. The specific scheme can be found in the apparatus and method disclosed in existing literature ZL2004100688802 / US7583788B2 / EP2541238.

[0003] The aforementioned apparatus and method constitute a crucial foundational technology for short-wavelength characteristic X-ray diffraction testing. Many subsequent related testing methods (such as CN2014108421013, a non-destructive testing method for pinpoint internal stress in plate-shaped materials using short-wavelength X-ray diffraction, and CN2018115468262, a method for locating test samples using short-wavelength X-ray diffraction) are based on further innovations of this technology. However, to date, no related apparatus or method has been found for testing near-surface residual stress in materials / workpieces. Summary of the Invention

[0004] The purpose of this invention is to provide a short-wavelength characteristic X-ray diffraction non-destructive testing device and method for near-surface residual stress. The near-surface layer typically refers to a depth of 3 mm extending from the material surface into the material's interior.

[0005] The present invention adopts the following technical solution.

[0006] A short-wavelength characteristic X-ray diffraction non-destructive testing device for near-surface residual stress includes a radiation source and a detector, located on opposite sides of the sample. The short-wavelength characteristic X-rays emitted by the radiation source are incident in the same direction as the sample thickness. The sample testing position is adjusted by precisely moving the sample stage along the sample thickness direction. The incident X-rays and diffracted X-rays are collimated by an incident collimator and a receiving collimator, respectively. All X-rays are parallel beams with rectangular cross-sections, and the positioning accuracy along the axis of motion of the sample thickness is high. The residual stress is the near-surface residual stress of the sample.

[0007] As a preferred embodiment, the light-transmitting cross-sections of both the incident collimator and the receiving collimator are rectangular, with a width of 0.05mm-0.2mm and a height of 4mm-20mm in the diffraction plane.

[0008] To improve detection accuracy, the ratio of the slit width to the slit length of the incident collimator and the receiving collimator should not exceed 0.0067.

[0009] To further improve detection accuracy, the sample position adjustment accuracy along the sample thickness direction is better than ±3μm.

[0010] A method for nondestructively testing near-surface residual stress of a material using the aforementioned device, comprising the following steps: Step 1: Place the stress-free powder standard on the sample stage. The stress-free powder standard has the same material and specifications as the sample being tested. Step 2: Measure the diffraction peaks of the stress-free powder standard sample from different parts of the surface to the interior, and record the diffraction peak P at part i. i ; Step 3: Determine the average peak value P using the internal diffraction peaks of the stress-free powder standard. avg Based on the standard, according to formula m i =P i / P avg Calculate the spurious shift correction factor m of the diffraction peak from the surface to the interior i region of the stress-free powder standard. i ; The internal diffraction peaks refer to the diffraction peaks that occur when the stress-free powder standard completely fills the diffraction volume. Step 4: Remove the stress-free powder standard from the sample stage, then install the test sample on the sample stage, and test the diffraction peak P at different depths i of the test sample. i试样 ; Step 5: Remove the test sample from the sample stage, then install a stress-free reference sample on the sample stage, and test the sample diffraction peak P at different depths i of the stress-free reference sample. i无应力参考样品 ; Step 6, based on the diffraction peak spurious shift correction factor m i Correction yielded the sample diffraction peak P' i试样 and the diffraction peak P' of the stress-free reference sample i无应力参考样品 ; Step 7: Calculate the near-surface residual strain based on the corrected diffraction peaks, and calculate the near-surface residual stress according to Hooke's Law.

[0011] Furthermore, when testing the diffraction peaks at various locations along the depth distribution of the stress-free standard sample, the test should be conducted at a depth of at least three times the length of the major axis of the rhomboid cross-section of the diffraction volume.

[0012] As a preferred embodiment, the stress-free powder standard and the test sample have the same diffraction crystal plane, and the test sites of the two are at the same depth from the surface.

[0013] As a preferred embodiment, the particle size of the stress-free powder standard is 50±5μm, and the particles of the stress-free powder standard are solidified by bonding.

[0014] Beneficial effects: The present invention enables non-destructive testing and analysis of near-surface residual stress in materials / workpieces, solving the problem that current near-surface residual stress testing methods often employ destructive testing such as electrolytic polishing and delamination, resulting in stress release and making the tested workpiece / material unusable. The present invention's solution provides unparalleled advantages for near-surface stress tracking testing, enabling non-destructive testing and analysis of near-surface residual stress. Attached Figure Description

[0015] Figure 1 This is the step in the embodiment of short-wavelength characteristic X-ray diffraction nondestructive testing of near-surface residual stress; Figure 2 This is a schematic diagram of the diffraction volume and relative position of the sample in the short-wavelength characteristic X-ray diffraction non-destructive testing device for near-surface residual stress in the embodiment. Figure 3 This is a schematic diagram of the correction factor for the near-surface diffraction peaks of the α-Fe(110) crystal plane of the high-strength steel stress-free powder standard sample in the embodiment; Figure 4 This is a schematic diagram of the α-Fe(110) crystal plane diffraction peak correction of the high-strength steel stress-free powder standard sample in the embodiment; Figure 5 This example shows the near-surface residual stress distribution of high-strength steel after surface strengthening. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0017] Combination Figure 2As shown, a short-wavelength characteristic X-ray diffraction non-destructive testing device for near-surface residual stress is described. The main structure of this device, referencing reference ZL2004100688802, includes a radiation source and a detector located on either side of the sample. The short-wavelength characteristic X-rays emitted by the radiation source are incident in the same direction as the sample thickness. The sample testing position is adjusted by precisely moving the sample stage along the sample thickness direction. The incident X-rays and diffracted X-rays are collimated by an incident collimator and a receiving collimator, respectively. All X-rays are parallel beams with rectangular cross-sections, exhibiting high positioning accuracy along the axis of sample thickness movement. The residual stress is the near-surface residual stress of the sample. The light-transmitting cross-sections of both the incident and receiving collimators are rectangular, with a width of 0.05mm-0.2mm and a height of 4mm-20mm within the diffraction plane. The ratio of the slit width to the slit length of the incident and receiving collimators is no greater than 0.0067. Along the sample thickness direction, the sample position adjustment accuracy is better than ±3μm (specifically, a high-precision position sensor is configured on the motion axis along the sample thickness direction, and the position sensor measurement accuracy is better than ±3μm).

[0018] Combination Figures 1 to 5 As shown, based on the strong penetrating power of short-wavelength characteristic X-rays, non-destructive testing and analysis were performed on the near-surface residual stress of high-strength steel materials after surface strengthening. The specific steps are as follows: (1) First, place the stress-free powder standard of high-strength steel (with a particle size of 50±5μm) of the same material and specification as the high-strength steel sample to be tested (i.e. the test sample) on the sample stage of the device (i.e. the short-wavelength characteristic X-ray diffraction near-surface residual stress non-destructive testing device). (2) Testing the diffraction peaks P of high-strength steel stress-free powder standard samples from the surface to the interior. i ,like Figure 4 The curve before correction is shown; When testing the diffraction peaks of high-strength steel stress-free powder standard samples at various depth locations, the test should be conducted to a depth of at least three times the length of the major axis of the rhomboid cross-section corresponding to the diffraction volume. (3) Using the average peak value Pavg of the diffraction peaks inside the high-strength steel stress-free powder standard as a benchmark, the false shift correction factor m of the diffraction peaks from the surface to the i-th part of the high-strength steel stress-free powder standard is calculated. i , where m i =P i / Pavg, the result is as follows Figure 3 As shown; (4) Remove the stress-free powder standard of high-strength steel from the sample stage, install the high-strength steel sample to be tested (i.e., the test sample) on the sample stage, and after positioning the high-strength steel sample in its depth and horizontal directions, control the sample stage to move along the horizontal and depth directions to test the sample diffraction peak P at different depths i of the test high-strength steel sample. i试样 ; (5) Remove the high-strength steel sample to be tested from the sample stage, install the high-strength steel stress-free reference sample on the sample stage, and after positioning the high-strength steel stress-free reference sample in its depth and horizontal directions, control the movement of the sample stage along the horizontal and depth directions to test the sample diffraction peak P at different depths i of the high-strength steel stress-free reference sample. i无应力参考样品 ; (6) Based on the obtained diffraction peak false shift correction factor m i The diffraction peak P' of the high-strength steel sample was obtained after correction. i试样 The diffraction peak P' of the high-strength steel stress-free reference sample i无应力参考样品 The result is as follows Figure 4 As shown; (7) The near-surface residual strain was calculated based on the diffraction peaks at different depths of the calibrated high-strength steel sample and the high-strength steel stress-free reference sample. The residual stress was calculated according to Hooke's law, and the near-surface residual stress distribution along the depth was obtained. The results are as follows: Figure 5 As shown.

Claims

1. A method for nondestructively testing near-surface residual stress in materials using a residual stress nondestructive testing device, characterized in that, The residual stress nondestructive testing device includes a radiation source and a detector, which are located on both sides of the sample. The short-wavelength characteristic X-rays emitted by the radiation source are incident in the same direction as the sample thickness. The sample test position is adjusted by controlling the sample stage to move precisely along the sample thickness. The device is characterized in that the incident X-rays and diffracted X-rays are collimated by the incident collimator and the receiving collimator, respectively. All the rays are parallel light and the beam cross-sections are rectangular. The steps include: Step 1: Place the stress-free powder standard on the sample stage. The stress-free powder standard has the same material and specifications as the sample being tested. Step 2: Measure the diffraction peaks of the stress-free powder standard sample from different parts of the surface to the interior, and record the diffraction peak P at part i. i ; Step 3: Determine the average peak value P using the internal diffraction peaks of the stress-free powder standard. avg Based on the standard, according to formula m i =P i / P avg Calculate the spurious shift correction factor m of the diffraction peak at location i from the surface to the interior of a stress-free powder standard. i ; The internal diffraction peak refers to the diffraction peak that occurs when the diffraction volume completely enters the interior of the stress-free powder standard. Step 4: Remove the stress-free powder standard from the sample stage, then install the test sample on the sample stage, and test the diffraction peak P at different depths i of the test sample. i试样 ; Step 5: Remove the test sample from the sample stage, then install a stress-free reference sample on the sample stage, and test the sample diffraction peak P at different depths i of the stress-free reference sample. i无应力参考样品 ; Step 6, based on the diffraction peak spurious shift correction factor m i Correction yielded the sample diffraction peak P ’ i试样 and the diffraction peak P of the stress-free reference sample ’ i无应力参考样品； Step 7: Calculate the near-surface residual strain based on the corrected diffraction peaks, and calculate the near-surface residual stress according to Hooke's Law.

2. The method according to claim 1, characterized in that: Both the incident collimator and the receiving collimator have rectangular light-transmitting cross sections. The width of the light-transmitting cross section in the diffraction plane is 0.05mm-0.2mm, and the height is 4mm-20mm.

3. The method according to claim 1, characterized in that: The ratio of the slit width to the slit length of the incident collimator and the receiving collimator is no greater than 0.0067.

4. The method according to claim 1, characterized in that: Along the sample thickness direction, the sample position adjustment accuracy is better than ±3μm.

5. The method according to claim 1, characterized in that: When testing the diffraction peaks of stress-free standard samples at various depths, the test should be conducted at a depth of at least three times the length of the major axis of the rhomboid cross-section of the diffraction volume.

6. The method according to claim 5, characterized in that: The stress-free powder standard and the test sample have the same diffraction crystal plane, and the test sites of the two are at the same depth from the surface.

7. The method according to claim 6, characterized in that: The stress-free powder standard has a particle size of 50±5μm, and the particles of the stress-free powder standard are solidified by bonding.

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