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Testing principle and method of residual stress detector

  • Source: Unknown
  • Date: April 28, 2020
  • Number of views: three hundred and forty-eight
The measurement methods of residual stress can be divided into two categories: destructive testing and nondestructive testing. The destructive test method is the stress release method, which can also be called the mechanical method; Non destructive method is physical method.
 
Test principle of residual stress detector
Based on the famous Bragg equation 2dsin θ= n λ ： That is, when a certain wavelength of X-ray is irradiated on the crystal material, the optical path difference of the X-ray diffracted by two adjacent atomic planes is exactly an integral multiple of the wavelength. By measuring the diffraction angle change Δθ So as to obtain the change of lattice spacing Δ d. According to Hooke's law and the principle of elasticity, the residual stress of the material is calculated. (X-ray diffraction method)
The principle of measuring residual stress by blind hole method is shown in the figure below. Assuming that there is a general residual stress field in a certain area of an isotropic material, the maximum and minimum principal stresses are σ 1 and σ 2. Paste a special strain rosette on the surface of the area, punch a small hole in the center of the strain rosette, causing stress release at the hole edge, so as to generate release strain in the strain rosette deletion area. According to the release strain measured by the strain rosette, the residual stress can be calculated: the following figure is the schematic diagram of blind hole method residual stress measurement.
 
In the formula:
ε 1、 ε 2、 ε 3 - Release strain in three directions;
σ 1、 σ 2 - maximum and minimum principal stress;
θ — σ The included angle between No. 1 and the reference axis of No. 1 sheet;
E - elastic modulus of material;
A. B - Two release coefficients.
The A and B coefficients are related to the hole diameter, strain rosette size and hole depth.
 
Residual stress detector test method
 
The measurement methods of residual stress can be divided into two categories: destructive testing and nondestructive testing. The destructive test method is the stress release method, which can also be called the mechanical method; Non destructive method is physical method.
 
The mechanical method (destructive) is the drilling method (blind hole method), followed by the ring core method for certain objects. X-ray diffraction is the most widely used physical method (non-destructive), and other main physical methods include neutron diffraction, magnetic method and ultrasonic method.
 
Each test method has its own advantages and disadvantages. Generally, the test method that is more suitable for the workpiece is selected by taking advantage of the advantages and avoiding the disadvantages. Sigmar residual stress detector mainly adopts blind hole method for testing, and other methods are used as auxiliary means.
 
The above is the sharing of Dongyi Seiko on the "testing principle and method of residual stress detector". Professional supply of Shenzhen Dongyi Precision Equipment Co., Ltd Stress tester , glass stress tester, Japanese original stress tester, fsm-6000le surface stress tester and other kinds of stress detection equipment, providing professional laboratory solutions and equipment support services, consultation hotline: 400-992-8117
 
 

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