In order to analyze the possibility of detecting defects in bend pipe using low-frequency ultrasonic guided wave, the propagation of T(0,1) mode and L(0,2) mode through straight-curved-straight pipe sections was studi...In order to analyze the possibility of detecting defects in bend pipe using low-frequency ultrasonic guided wave, the propagation of T(0,1) mode and L(0,2) mode through straight-curved-straight pipe sections was studied. FE(finite element) models of bend pipe without defects and those with defects were introduced to analyze energy distribution, mode transition and defect detection of ultrasonic guided wave. FE simulation results were validated by experiments of four different bend pipes with circumferential defects in different positions. It is shown that most energy of T(0,1) mode or L(0,2) mode focuses on extrados of bend but little passes through intrados of bend, and T(0,1) mode or L(0,2) mode is converted to other possible non-axisymmetric modes when propagating through the bend and the defect after bend respectively. Furthermore, L(0,2) mode is more sensitive to circumferential notch than T(0,1) mode. The results of this work are beneficial for practical testing of pipes.展开更多
While a small-radius induction bend is manufactured,various cross-section distortions may occur,such as its cross section tending to be elliptic,and wall thickness reduction or increase.These defects may deteriorate t...While a small-radius induction bend is manufactured,various cross-section distortions may occur,such as its cross section tending to be elliptic,and wall thickness reduction or increase.These defects may deteriorate the bearing capacity of pipelines.In order to study the effect of cross-section distortion on the performance of small-radius induction bends,3D(D refers to pipe diameter)induction bends were manufactured based on different combinations of process parameters.Then,the cross-section distortion,structure properties and their correlation of 3D bends and conventional 5D bends were analyzed comprehensively by means of cross-section geometry analysis,distortion analysis,physical and chemical property test,micro-structural analysis and so on.The following results were obtained.First,the wall thickening/thinning rate of 3D bends is about 2 times that of 5D bends,and the roundness of 3D bends is about 2e4 times that of 5D bends.Second,the cross-section distortion of 3D bends is obvious,so its heating temperature varies greatly in different parts,leading to different structure morphologies and contents.As a result,the numerical distribution of mechanical properties of each part of 3D bends(e.g.intrados,extrados and neutral zone)is discrete.Third,the strength at the intrados of most bends doesn't meet the standard,and it is sorted form the higher to the lower as extrados,neutral zone and intrados while the sequence of Charpy impact toughness is right contrary to the strength.Fourth,the strength at intrados and extrados decreases with the increase of roundness.The strength at intrados decreases with the increase of thickening rates.And the strength at extrados increases with the increase of thinning rates.展开更多
基金Project(51265044)supported by the National Natural Science Foundation of ChinaProject(2013TT2028)supported by the Science and Technology Project of Hunan Province of ChinaProject(2012QK162)supported by the Science and Technology Project of General Administration of Quality Supervision,Inspection and Quarantine of China
文摘In order to analyze the possibility of detecting defects in bend pipe using low-frequency ultrasonic guided wave, the propagation of T(0,1) mode and L(0,2) mode through straight-curved-straight pipe sections was studied. FE(finite element) models of bend pipe without defects and those with defects were introduced to analyze energy distribution, mode transition and defect detection of ultrasonic guided wave. FE simulation results were validated by experiments of four different bend pipes with circumferential defects in different positions. It is shown that most energy of T(0,1) mode or L(0,2) mode focuses on extrados of bend but little passes through intrados of bend, and T(0,1) mode or L(0,2) mode is converted to other possible non-axisymmetric modes when propagating through the bend and the defect after bend respectively. Furthermore, L(0,2) mode is more sensitive to circumferential notch than T(0,1) mode. The results of this work are beneficial for practical testing of pipes.
基金supported by the National Major Research and Development Project“Research on Disaster-caused Mechanism and Evolution Rules of Damages of Oil&Gas Pipelines and Storage&Transportation Facilities”(No.:2016YFC0802101)Scientific New Star Project of Shaanxi Province“Quality Forecast and Defect Control of Mold-free Hot-bending Cross Section with Small Radius of Pipe Material with Large Caliber”(No.:2015KJXX-73).
文摘While a small-radius induction bend is manufactured,various cross-section distortions may occur,such as its cross section tending to be elliptic,and wall thickness reduction or increase.These defects may deteriorate the bearing capacity of pipelines.In order to study the effect of cross-section distortion on the performance of small-radius induction bends,3D(D refers to pipe diameter)induction bends were manufactured based on different combinations of process parameters.Then,the cross-section distortion,structure properties and their correlation of 3D bends and conventional 5D bends were analyzed comprehensively by means of cross-section geometry analysis,distortion analysis,physical and chemical property test,micro-structural analysis and so on.The following results were obtained.First,the wall thickening/thinning rate of 3D bends is about 2 times that of 5D bends,and the roundness of 3D bends is about 2e4 times that of 5D bends.Second,the cross-section distortion of 3D bends is obvious,so its heating temperature varies greatly in different parts,leading to different structure morphologies and contents.As a result,the numerical distribution of mechanical properties of each part of 3D bends(e.g.intrados,extrados and neutral zone)is discrete.Third,the strength at the intrados of most bends doesn't meet the standard,and it is sorted form the higher to the lower as extrados,neutral zone and intrados while the sequence of Charpy impact toughness is right contrary to the strength.Fourth,the strength at intrados and extrados decreases with the increase of roundness.The strength at intrados decreases with the increase of thickening rates.And the strength at extrados increases with the increase of thinning rates.
