Effects Of Defect Depth Research Articles

Research on the defect depth detection for pipeline steel with double defects using metal magnetic memory method

Metal magnetic memory testing is an effective method to detect the stress state of ferromagnetic materials, and shows great application potential in the field of defect detection of oil and gas pipelines recently. In this paper, the correlation between the normal component of residual magnetic field (RMF) and the defect depth, as well as the applied loading were investigated by tensile tests. The X70 pipeline steels were processed into specimens with double defects of six types of depths and three types of spacings. Some magnetic parameters are defined to characterize the distortion of the RMF in the defect area. The effect of defect depth and applied loading on the magnetic parameters is discussed. The RMF signals measured on the smooth side of the specimens were compared with those on the defective side. Results show that the normal parameters, obtained from the front and back of the specimens, are capable of detecting the defect depth. The slope of the linear relationship between the two increases with the increase of defect spacing. The expressions of normal magnetic parameters were derived based on the Jiles model and magnetic dipole model. The simulation results of defective side and smooth side were compared, as well as the simulation results of different defect spacing. The experimental and numerical simulation results show that the defect depth of pipeline steel can be evaluated by the characteristic parameters of the normal RMF signal under a certain stress level.

Experimental investigation for multi-defect detection of industrial pipeline based on passive infrared thermal imaging analysis: A case study

Corrosion of pipe walls is a major hidden hazard for the safety of chemical enterprises; therefore, detection of the depth of pipe wall corrosion defects is extremely important. In this study, passive thermal imaging technology was used to detect and evaluate corrosion defects of different shapes in pipe walls and of different depths for the same shape. Three-dimensional finite element models of defects with different depths were established using COMSOL, and the thermal response mechanisms of defects with different depths and the effects of defect depth and shape on heat transfer were analyzed. The thermal response mechanism of defects with different shapes and depths (1–3 mm) was also analyzed experimentally and compared with that of defect-free parts to analyze the safety of the pipeline and verify the results of the numerical simulation analysis. The results indicated that the level of fluid temperature determined the accuracy of the test, and at the same temperature, the defects at a depth of 3 mm exhibited multiple peaks and a large peak area. However, defects with a depth of 2 mm exhibited the opposite behavior, and the heating rate of 3-mm deep defects during the temperature change was 1.08 times higher than that for 2 mm-deep defects. This study provides a reference for detecting leaks in chemical pipelines.

The evolution of the out-of-phase dipole beams in the repulsive defect photonic moiré lattice with saturable self-focusing nonlinearity media

We demonstrate in a numerical manner the intriguing transmission of the out-of-phase (OOP) dipole beams in the repulsive defect photonic moiré lattice with rotation angle and defect depth under saturable self-focusing nonlinearity. Photonic moiré lattices, that are created by two mutually rotated square patterns with a relative rotation angle . We introduce a single-site repulsive defect in periodic photonic moiré lattices, and excite this site with the OOP dipole beams. We reveal that the OOP dipole beams undergoes two evolution stages during propagation, for the first time to our knowledge. It is shown that the OOP dipole beams maintain stable propagation over a certain distance in the first stage, which depends on the defect depth. Then the energy of the OOP dipole beams flows between its two spots, exhibiting periodic-like oscillation in the second stage, along with discussion about the effect of defect depth on the stable propagation distance of the OOP dipole beams, one finds that the stable propagation distance decreases linearly with increasing defect depth . At the same time, we perform a polynomial fit between the oscillation period of the OOP dipole beams and the defect depth . These two fitting curves fully demonstrate that the repulsive defect can profoundly affect the propagation behavior of the OOP dipole beams. Our results may provide novel insights into the localization and oscillation of beams in defect structures.

Effect of boundary position and defect shape on the mechanical properties of ball bearings

This paper presents a mechanical model of angular contact ball bearing with local and extended defects in the outer raceway and the analytical formulations of varying stiffness under combined loads are obtained. The effects of radial load and clearance on variable stiffness of the bearing at the boundary positions are analyzed. Results show that the load distribution is not necessarily continuous and the maximum and minimum stiffness of the angular contact ball bearing can be located at either of the two boundary positions or even at non-boundary position under the effect of the contact angle. Meanwhile, the effects of defect depth and loads on the mechanical properties and varying stiffness of the bearing under localized and extended defects are studied, respectively, and the mechanism of “limit depth” and “critical load” is analyzed. These results are useful for quantitative fault diagnosis and reliability analysis of rotor-bearing systems.

Fiber bragg grating based detection of part-thickness cracks in bent composite laminates using feature-guided waves

Composite structures with bends are widely used in aerospace and industrial sectors. However health monitoring of such structures is challenging due to their complex topographical features. Recent literature shows that bends in composite laminates can confine and guide ultrasonic energy along their length, known as feature-guided waves (FGW). This article demonstrates a fiber Bragg grating based technique using FGW modes for defect detection and identification in bent composite laminates. In addition, the effects of defect depth and excitation frequency on the FGW mode reflection coefficient are reported using 3D finite element simulations. Physical insight into the reflection behavior is discussed based on an analysis of mode interaction with part-thickness cracks.

Finite Element Analysis and Research on Corrosion Defect of Tank Floor

Storage tank is an essential vessel in petrochemical industry, and the corrosion of tank is an important reason for the safety hazard. The corrosion of tank bottom plate is more serious than the tank wall, and it is not easy to check and repair, when damaged to a certain extent it will cause the leakage of the media, then lead to waste of energy, environmental pollution, at the same time it will cause a major accident. Magnetic flux leakage testing is widely used in the field of tank floor inspection with the advantages of fast scanning speed, accurate results and so on. In this paper, the finite element simulation and analysis of the corrosion defect leakage magnetic field is used to obtain the data, and the characteristic of the leakage magnetic field is extracted. The effect of defect depth and width and shape on the magnetic flux leakage field is studied, and the distribution curve of the magnetic flux leakage field is obtained.

Effect of defect depth on surface plasmon scattering by subwavelength surface defects

Surface plasmon scattering by bidimensional indentations and protrusions is examined, mainly in the optical regime. The width of the defects is fixed, while their height is varied. Both individual defects and arrays of defects are considered. Protrusions mainly reflect the incident plasmons in the optical range. Indentations mainly radiate the incident plasmon out of plane. An indentation produces maximum reflection and out-of-plane radiation at the same wavelength when its interaction with the incident surface plasmon is resonant. Protrusions, in general, exhibit maximum reflection and radiation at different wavelengths. Shallow arrays of either defects produce a photonic band gap, whose spectral width can be broadened by increasing the defects height or depth. At wavelengths inside the band gap, ridge arrays reflect surface plasmon polaritons (SPP's) better than groove arrays while groove arrays radiate SPP's better than ridge arrays.

Quantitative study of metal magnetic memory signal versus local stress concentration

The technique of metal magnetic memory (MMM) has attracted great attentions in the field of non-destructive tests due to its unique advantages of easy-operation, low cost, and high efficiency. However, a thorough understanding of the physical mechanism of MMM phenomenon has not been clearly addressed. Generally, MMM tests can only find the possible locations of defects without quantitative descriptions about the defect characteristics. To promote study in this area, a linear magnetic-charge model is employed to analyze the self-magnetic flux leakage (SMFL) distribution in the local stress-concentration zone. Theoretical results based on this model can capture some basic characteristics of SMFL signals of ferromagnets observed in experiments. Specially, the model provides some quantitative results about the effects of defect depth and location (surface- or inner-defects) on SMFL signals.

The effects of defect depth and bending stress on magnetic Barkhausen noise and flux-leakage signals

Magnetic-flux-leakage (MFL) measurements are used for corrosion inspection of buried oil and gas pipelines. MFL signals are sensitive to the depth of defects, such as corrosion pits, in the pipe wall and to external stresses generated mainly by the line pressure. MFL signal variations have been studied from the inside wall in the presence of various circumferential bending stresses and magnetic flux densities for three outside wall pits of depths 30%, 50% and 80% of the wall thickness. Magnetic Barkhausen noise (MBN) measurements have been used to study the stress-induced changes in the direction of the bulk magnetic easy axis and directional anisotropies of the pipe wall. These help one to understand the stress-dependent MFL results.