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Measuring method of depth of metal surface hardening layer with curve surface

A technology of hardened layer depth and metal surface, applied in measuring devices, instruments, optical devices, etc., can solve the problems of complex post-processing and difficult application, and achieve the effect of good consistency and simple and practical measurement methods.

Inactive Publication Date: 2009-10-07
SUZHOU UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, these studies show that for the PTR detection of curved samples, the post-processing is extremely complex and needs to introduce the shape information and curvature of the surface, so it is difficult to apply in practical detection

Method used

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  • Measuring method of depth of metal surface hardening layer with curve surface
  • Measuring method of depth of metal surface hardening layer with curve surface
  • Measuring method of depth of metal surface hardening layer with curve surface

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Experimental program
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Effect test

Embodiment 1

[0041] Embodiment 1: A method for measuring the depth of a hardened layer on a metal surface with a curved surface. The specific implementation process is as follows:

[0042] The experimental sample is a non-uniform cylinder of AISI1020 steel (C: 17%-23%, Mn: 35%-65%, P≤3.5%, S≤3.5%) that has undergone surface heat treatment. The sample diameters are D=18mm, D =10mm and D=4mm, both of which are 30mm in length. There are two cylindrical samples of each size, one of which is surface hardened and the other is not hardened, as a reference sample. The thermophysical coefficient of AISI1020 steel is k=50.63W / mK, ρ=7850g / cm 3 , C=468.608J / kg℃, α=k / ρc=13.7663×10 -6 (m 2 / s). The experimental measuring device is attached figure 1 As shown (see Table 1 for the performance and parameters of each instrument), it is mainly composed of Jenoptik semiconductor laser 1, power supply 8, beam expansion system, off-axis parabolic mirror 2, HgCdTd infrared detector 3, Ge filter, preamplifier 4, The l...

Embodiment 2

[0066] Embodiment 2: Theoretical analysis of the detection method of the present invention

[0067] (1) Cylindrical sample model and calculation formula

[0068] Set a beam of light intensity I 0 , The laser beam with modulation frequency f(w=2πf) is irradiated on the cylindrical sample, the sample absorbs the light and causes the temperature change and the change of infrared radiation, and the corresponding infrared detector (such as HgCdTe) can detect the sample Thermal radiation-the photothermal signal. It is assumed that the surface hardening layer is an uneven layer composed of multiple layers, that is, a multi-layer cylindrical model composed of N layers of different materials. k i , Α i Respectively represent the thermal conductivity and thermal diffusivity of the i-th layer; a i And a i+1 Denote the outer radius and inner radius of the i-th layer, respectively.

[0069] The temperature field at any point on the cylindrical surface can be expressed as:

[0070]

[0071] W...

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Abstract

The invention discloses a measurement method of the depth of a metal surface hardening layer with a curve surface, which is characterized by comprising the following steps of: adopting a photothermal radiation measurement method for measurement, respectively obtaining the amplitude of the surface temperature field of the sample before and after hardening and the measurement value of frequency variation relative to modulated light; then carrying out self normalization processing to obtain normalized amplitude and phase value corresponding to the frequency value; utilizing plan theory and adopting a forward numerical fitting algorithm for fitting so as to obtain a profile curve with thermal conductivity changing along the depth; and the hardening depth is analyzed by the profile curve of the thermal conductivity. The measurement method obtains the depth of the surface hardening layer of the metal sample, thus conveniently realizing non-destructive measurement to the thickness of the surface hardening layer of the metal sample with the curve surface.

Description

Technical field [0001] The invention relates to a non-contact non-destructive testing method for materials, in particular to a method for non-destructive testing of the depth profile of the surface hardened layer of a metal sample that has undergone surface hardening treatment. Background technique [0002] The depth and profile of the surface hardened layer of metal materials (especially steel) is an important indicator of materials, and it is a required parameter for key components in industries such as aerospace, shipbuilding, automobiles, and heat treatment. The existing international standard measurement method is destructive contact measurement, which uses the so-called "indentation" method. A specially designed needle-shaped indentation head is placed on the surface of a polished sample to be tested, and a specific load and corresponding time are applied to the indentation head to leave an indentation on the surface of the sample. By measuring the size of the indentation a...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01B11/22G01B11/24
Inventor 王钦华陈珠英刘立旺曲宏
Owner SUZHOU UNIV
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