Torsional guided waves have been widely utilized to inspect the surface corrosion in pipelines due to their simple displacement behaviors and the ability of longrange transmission.Especially,the torsional mode T(0,1),...Torsional guided waves have been widely utilized to inspect the surface corrosion in pipelines due to their simple displacement behaviors and the ability of longrange transmission.Especially,the torsional mode T(0,1),which is the first order of torsional guided waves,plays the irreplaceable position and role,mainly because of its non-dispersion characteristic property.However,one of the most pressing challenges faced in modern quality inspection is to detect the surface defects in pipelines with a high level of accuracy.Taking into account this situation,a quantitative reconstruction method using the torsional guided wave T(0,1)is proposed in this paper.The methodology for defect reconstruction consists of three steps.First,the reflection coefficients of the guided wave T(0,1)scattered by different sizes of axisymmetric defects are calculated using the developed hybrid finite element method(HFEM).Then,applying the boundary integral equation(BIE)and Born approximation,the Fourier transform of the surface defect profile can be analytically derived as the correlative product of reflection coefficients of the torsional guided wave T(0,1)and the fundamental solution of the intact pipeline in the frequency domain.Finally,reconstruction of defects is precisely performed by the inverse Fourier transform of the product in the frequency domain.Numerical experiments show that the proposed approach is suitable for the detection of surface defects with arbitrary shapes.Meanwhile,the effects of the depth and width of surface defects on the accuracy of defect reconstruction are investigated.It is noted that the reconstructive error is less than 10%,providing that the defect depth is no more than one half of the pipe thickness.展开更多
The inspection of thickness thinning defects and corrosion defects is greatly significant for the health prediction of plate structures.The main aim of this research is to propose a novel and effective approach to ach...The inspection of thickness thinning defects and corrosion defects is greatly significant for the health prediction of plate structures.The main aim of this research is to propose a novel and effective approach to achieve the accurate and rapid detection of arbitrary defects using shear horizontal(SH)guided waves,particularly for large-depth and complex defects.The proposed approach combines the quantitative detection of Fourier transform with a reference model-based strategy to improve the accuracy of large-depth defect detection.Since the shallow defect profile is theoretically constructed by inverse Fourier transform of the product of reflection coefficients and integral coefficients of reference models,the unknown large-depth defect can be initially assessed using the relevant information from a predefined reference model.By iteratively updating the integral coefficients of reference models,the accuracy of reconstruction of large-depth defects is much improved.To achieve the converged defect profile,a termination criterion,the root mean square error,is applied to guarantee the construction of defects with a high level of accuracy.Moreover,the hybrid finite element method is used to simulate the propagation of SH guided waves in plates for calculating the reflection coefficients of plates with defects.Finally,to demonstrate the capability of the developed reconstruction method for defect detection in terms of accuracy and efficiency,three types of large-depth defect profiles,i.e.,a rectangular flaw,a double-rectangular flaw and a complex flaw,are examined.Results show that the discrepancy between the predicted defect profile and the real one is quite small,even in the largest-depth defect case where the defect depth is equal to 0.733 times the plate thickness,the minimal difference is observed.It is noted that the fast convergence of the proposed approach can be achieved by no more than ten updates for the worst case.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.11502108 and 1611530686)the State Key Laboratory of Mechanics and Control of Mechanical Structures at Nanjing University of Aeronautics and Astronautics(NUAA)(No.MCMS-E-0520K02)and the Key Laboratory of Impact and Safety Engineering,Ministry of Education,Ningbo University(No.CJ201904)。
文摘Torsional guided waves have been widely utilized to inspect the surface corrosion in pipelines due to their simple displacement behaviors and the ability of longrange transmission.Especially,the torsional mode T(0,1),which is the first order of torsional guided waves,plays the irreplaceable position and role,mainly because of its non-dispersion characteristic property.However,one of the most pressing challenges faced in modern quality inspection is to detect the surface defects in pipelines with a high level of accuracy.Taking into account this situation,a quantitative reconstruction method using the torsional guided wave T(0,1)is proposed in this paper.The methodology for defect reconstruction consists of three steps.First,the reflection coefficients of the guided wave T(0,1)scattered by different sizes of axisymmetric defects are calculated using the developed hybrid finite element method(HFEM).Then,applying the boundary integral equation(BIE)and Born approximation,the Fourier transform of the surface defect profile can be analytically derived as the correlative product of reflection coefficients of the torsional guided wave T(0,1)and the fundamental solution of the intact pipeline in the frequency domain.Finally,reconstruction of defects is precisely performed by the inverse Fourier transform of the product in the frequency domain.Numerical experiments show that the proposed approach is suitable for the detection of surface defects with arbitrary shapes.Meanwhile,the effects of the depth and width of surface defects on the accuracy of defect reconstruction are investigated.It is noted that the reconstructive error is less than 10%,providing that the defect depth is no more than one half of the pipe thickness.
基金supported in part by the State Key Laboratory of Mechanics and Control of Mechanical Structures at NUAA[Grant Number MCMS-E-0520K02]in part by the Key Laboratory of impact and Safety Engineering,Ministry of Education,Ningbo University[CJ201904]in part by the National Natural Science Foundation of China[Grant Numbers 11502108,1611530686].
文摘The inspection of thickness thinning defects and corrosion defects is greatly significant for the health prediction of plate structures.The main aim of this research is to propose a novel and effective approach to achieve the accurate and rapid detection of arbitrary defects using shear horizontal(SH)guided waves,particularly for large-depth and complex defects.The proposed approach combines the quantitative detection of Fourier transform with a reference model-based strategy to improve the accuracy of large-depth defect detection.Since the shallow defect profile is theoretically constructed by inverse Fourier transform of the product of reflection coefficients and integral coefficients of reference models,the unknown large-depth defect can be initially assessed using the relevant information from a predefined reference model.By iteratively updating the integral coefficients of reference models,the accuracy of reconstruction of large-depth defects is much improved.To achieve the converged defect profile,a termination criterion,the root mean square error,is applied to guarantee the construction of defects with a high level of accuracy.Moreover,the hybrid finite element method is used to simulate the propagation of SH guided waves in plates for calculating the reflection coefficients of plates with defects.Finally,to demonstrate the capability of the developed reconstruction method for defect detection in terms of accuracy and efficiency,three types of large-depth defect profiles,i.e.,a rectangular flaw,a double-rectangular flaw and a complex flaw,are examined.Results show that the discrepancy between the predicted defect profile and the real one is quite small,even in the largest-depth defect case where the defect depth is equal to 0.733 times the plate thickness,the minimal difference is observed.It is noted that the fast convergence of the proposed approach can be achieved by no more than ten updates for the worst case.
