X-ray stress analyzer
X-ray stress analyzer
Use background
Various mechanical components tend to produce residual stress during manufacture. In the manufacturing process, the appropriate residual stress may become part of the strengthening factor, inappropriate residual stress may lead to defects such as deformation and cracking process; After processing, the residual stress will affect the static load strength, fatigue strength, stress Corrosion resistance and shape and size stability. A member of the residual stress state, designers, manufacturers and users of the common concern. Non-destructive determination of residual stress is necessary to improve strength design, improve process effectiveness, test product quality and perform safety analysis of equipment.
Measuring principle
Among various methods of non-destructive determination of residual stress, X-ray diffraction is recognized as the most reliable and practical. It is mature in principle and perfect in methodology. It has undergone more than 70 years of progress and is widely used in mechanical engineering and materials science both at home and abroad with outstanding achievements. Based on the well-known Bragg equation 2dsinθ = nλ, that is, a certain wavelength of X-ray radiation onto the crystalline material, the diffraction of two adjacent atomic planes when the X-ray optical path difference is exactly an integral multiple of the wavelength. The change in lattice spacing Δd was obtained by measuring the change in diffraction angle Δθ. According to Hooke's law and the principle of elastic mechanics, the residual stress of the material was calculated.
In the case of non-textured, untextured polycrystalline material, there are many grains in a beam of X-rays, in which there must be many grains whose specified (hkl) planes are parallel to The surface of the sample, the normal angle between crystal plane and the surface normal ψ is 0; there must be many crystal grains, the normal of the (hkl) crystal plane and the surface normal at any ψ. First, a certain point (point o) normal to the sample as the axis, a beam of light of the appropriate wavelength and detector (counter tube) symmetrically point to the point O, and synchronously scanned to change the angle of incidence and reflection angle . According to Bragg's Law, the diffraction peak parallel to the (h k 1) plane of the sample surface and the corresponding diffraction angle 2θ can be found. The plane consisting of the X-ray and counter tube axis is called the scanning plane. The normal to the diffraction plane must lie in the scanning plane and at the bisector of the angle between the X-ray beam and the counter-tube axis. Let us remember, at this time the scanning plane and the sample surface perpendicular to the diffraction crystal plane parallel to the sample surface, ψ = 0. Then, the scanning plane is rotated by a ψ angle along the line OY in Figure A, and the diffraction peak of the (hkl) crystal plane and the corresponding diffraction angle 2θ can be obtained. In this case, the normal of the diffraction crystal plane and the surface of the sample Line angle is ψ.
X-ray stress meter is a simplified and practical X-ray diffraction device, so it also has an additional function ─ ─ Determination of residual austenite steel content. Since it works on a variety of solid workpieces and can be tested at different angles of φ, Ψ for the same point to detect the effects of texture, this feature has important and unique uses.
Use background
Various mechanical components tend to produce residual stress during manufacture. In the manufacturing process, the appropriate residual stress may become part of the strengthening factor, inappropriate residual stress may lead to defects such as deformation and cracking process; After processing, the residual stress will affect the static load strength, fatigue strength, stress Corrosion resistance and shape and size stability. A member of the residual stress state, designers, manufacturers and users of the common concern. Non-destructive determination of residual stress is necessary to improve strength design, improve process effectiveness, test product quality and perform safety analysis of equipment.
Measuring principle
Among various methods of non-destructive determination of residual stress, X-ray diffraction is recognized as the most reliable and practical. It is mature in principle and perfect in methodology. It has undergone more than 70 years of progress and is widely used in mechanical engineering and materials science both at home and abroad with outstanding achievements. Based on the well-known Bragg equation 2dsinθ = nλ, that is, a certain wavelength of X-ray radiation onto the crystalline material, the diffraction of two adjacent atomic planes when the X-ray optical path difference is exactly an integral multiple of the wavelength. The change in lattice spacing Δd was obtained by measuring the change in diffraction angle Δθ. According to Hooke's law and the principle of elastic mechanics, the residual stress of the material was calculated.
In the case of non-textured, untextured polycrystalline material, there are many grains in a beam of X-rays, in which there must be many grains whose specified (hkl) planes are parallel to The surface of the sample, the normal angle between crystal plane and the surface normal ψ is 0; there must be many crystal grains, the normal of the (hkl) crystal plane and the surface normal at any ψ. First, a certain point (point o) normal to the sample as the axis, a beam of light of the appropriate wavelength and detector (counter tube) symmetrically point to the point O, and synchronously scanned to change the angle of incidence and reflection angle . According to Bragg's Law, the diffraction peak parallel to the (h k 1) plane of the sample surface and the corresponding diffraction angle 2θ can be found. The plane consisting of the X-ray and counter tube axis is called the scanning plane. The normal to the diffraction plane must lie in the scanning plane and at the bisector of the angle between the X-ray beam and the counter-tube axis. Let us remember, at this time the scanning plane and the sample surface perpendicular to the diffraction crystal plane parallel to the sample surface, ψ = 0. Then, the scanning plane is rotated by a ψ angle along the line OY in Figure A, and the diffraction peak of the (hkl) crystal plane and the corresponding diffraction angle 2θ can be obtained. In this case, the normal of the diffraction crystal plane and the surface of the sample Line angle is ψ.
X-ray stress meter is a simplified and practical X-ray diffraction device, so it also has an additional function ─ ─ Determination of residual austenite steel content. Since it works on a variety of solid workpieces and can be tested at different angles of φ, Ψ for the same point to detect the effects of texture, this feature has important and unique uses.
