1、Geomaterials,2014,4,55-63 Published Online April 2014 in SciRes.http:/www.scirp.org/journal/gm http:/dx.doi.org/10.4236/gm.2014.42006 How to cite this paper:Liu,B.,Sun,W.R.and Lin,Y.R.(2014)The Study of Electromagnetic Stress Testing Method on Oil-Gas Pipelines Based on WT.Geomaterials,4,55-63.http:
2、/dx.doi.org/10.4236/gm.2014.42006 The Study of Electromagnetic Stress Testing Method on Oil-Gas Pipelines Based on WT Bin Liu,Wanru Sun,Yiren Lin School of Information Science and Engineering,Shenyang University of Technology,Shenyang,China Email: Received 28 October 2013;revised 28 January 2014;acc
3、epted 7 February 2014 Copyright 2014 by authors and Scientific Research Publishing Inc.This work is licensed under the Creative Commons Attribution International License(CC BY).http:/creativecommons.org/licenses/by/4.0/Abstract This paper proposes an effective method for early diagnosis(stress conce
4、ntrating)of the oil-gas pipeline.Based on the principle of electromagnetic induction Faraday,we have designed and rea-lized the nondestructive testing system for stress concentration area of ferromagnetic materials by means of the research of metal materials inverse magnetostrictive effect mechanism
5、.The sys-tem changes the influence degree of the stress in ferromagnetic materials magnetic conductance to the corresponding voltage array by using discrete wavelet analysis method to process the data,in which not only the measuring accuracy is improved,but also the stress concentration is more dire
6、ctly reflected.The experiments confirm that the electromagnetic stress testing method is feasible and valid.Keywords Oil-Gas Pipeline,Electromagnetic Induction,Magnetic Conductance,Stress Concentration,Nondestructive Testing 1.Introduction To our country national economy,oil and gas pipeline transpo
7、rtation called the“energy blood”which is one of the five major transportation industries in China plays a very important role.With the growth of service time,ferromagnetic oil and gas pipelines will be the formation of a variety of fatigue damages and defects caused by stress concentration due to co
8、rrosion,abrasion,welding and other reasons.If not repaired in time,it will even-tually lead to the accident of pipeline leakage.Pipeline inspection technology can obtain the position of the pipeline damage,type,degree and other precise information,so as to provide reliable basis for pipeline safety
9、B.Liu et al.56 evaluation,life prediction and maintenance,etc.1 2.Although traditional nondestructive testing(NDT)me-thods(such as ultrasonic,magnetic,eddy current and magnetic flux leakage and penetration,etc.)can find what has been forming macro or most microscopic defects by testing one hundred p
10、ercent related parts of equipment and components,but for the early damage of metal components,especially in not yet forming contact disconti-nuity changing area,it is difficult to implement effective evaluation.As a result,it is unable to avoid sudden ac-cident caused by fatigue damage after repair.
11、Early hidden trouble of pipeline can be found timely by the effec-tive stress method,so it plays an important role in the reduction of oil and gas pipeline maintenance of human and financial resources 3 4.At present,there are many stress concentration area detecting methods,such as the blind-hole me
12、thod,ultra-sonic method,X-ray diffraction,electronic shearing speckle interferometry,metal magnetic memory method,etc.The blind-hole method is adopted in the measured component drilling a certain diameter and depth of the blind hole using borehole stress release point,to make the tested parts produc
13、ed the corresponding displacement and deformation,and to obtain the residual measured components of measurement points of stress by measuring the strain or displacement.Although the measuring sensitivity is higher,there are not only many interference factors,but also it is a lossy detection method,s
14、o it is limited in the practical application 5 6.Ultrasonic method is based on acoustic elasticity theory,using the ultrasonic sound travels in material internal stress caused by the birefringence effect of stress measurement.This method has larger detection depth and applicable materials are more,b
15、ut if the sound velocity variation compensation is improper,measurements are in big error.Besides,ul-trasonic method has a high requirement for the coupling of the probe and the workpiece surface shape,which is restricted in practical applications 7 8.X-ray diffraction method is widely used and the
16、principle is to meas-ure the lattice distortion caused by residual stress,then figures out the residual stresses in the measured point according to elastic mechanics theory.The method can be adapted to all kinds of materials and different shapes,sizes of workpiece,but there is a strict requirement to the surface of the measured object that the measurement of internal stress must be delaminated,which for large workpiece is difficult and the detection of equipment structure is more complex,therefo
