Design Of Magnetic Welding Residual Stress Measurement Instrument

In a variety of large structures (such as a large spherical tanks, boilers, pressure vessels, pressurepiping, lifting machinery, recreational facilities, etc.) manufacturing process, after hot and coldprocessing (such as cold-rolled, cold cutting, casting, welding,...), there general have the existence ofresidual stress, it affects structural strength, fracture toughness, especially the corrosion resistance ofthe material and has great influence on fatigue life. In many damage accidents, many caused by of theesidual stress. Therefore accurate, rapid measurement of residual stress has a very important and greatsignificance.Magnetostriction in the magnetic measurement method proven to be convenient, nospecial surface treatment,and many other advantages, which has become a one of the most usedmethod used in pressure vessel.This paper discusses the testing mechanism of the magnetostrictive method.Compare theperformance of the measuring probe, then shows by using nine foot probe, the biggest advantage isthat there not need to rotate when do measurements,so can reduce errors and improve the accuracy ofthe measurement.By comparison of magnetic materials, determine pure iron as the probematerial.Through electromagnetic simulation, optimizing the design of the probe parameters, such asincentive turns, saturation properties, lift-off. By designing the peripheral circuits, which includeexcitation circuit, differential circuit and phase circuit, voltage signal collected can be processed.Withprobe to measure the angle of principal stress difference and principal stress direction, throughexperimental methods, stress sensitivity coefficient calibrated.And then with Shear stress differencemethod, indirectly to the obtaining of average stress of the measuring points. Input the voltagemeasured to processing software writened, the measured point and its surrounding stress distributionobtained, achieve visualization display.Finally,produce weld specimen, the two-legged probe and nine-foot probe measurement resultswere compared, indicating the test feasibility of the nine-foot..Adjust the frequency, measured theplate stress distribution along depth.Measure the curvature specimen, and compare the experimentalresults with the X-ray results.By specimen testing and comparison test, nine-foot magneticmeasurement proved to be feasible and verify the simulation results. Further research work has beenrecommemded.