3414

3234

كارشناسي ارشد

﴿ طراحي كاربردي ﴾

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيك

1385

ده، 149، [II] ص. : مصور، نمودار

ص. ع: به فارسي و انگليسي

محمدرضا فروزان

احمد كرمانپور

محمود سليمي، سعيد ضيائي راد

مهندسي مكانيك

ID3234

به فارسي و انگليسي: قابل رويت در نسخه ديجيتال

Abstract Nowadays using large diameter seam welded pipes to transfer oil and gas between citiesor countries is greatly increased Because of the high speed and efficiency of submerged arcwelding SAW this method is widely used in production of these pipes Prediction of theresidual stresses is of the most important problems in the pipe manufacturing Because thehigh tensile residual stresses due to welding process on the corrosive environment could leadto stress corrosion cracking SCC For solving this problem in industry some methods areproposed to decrease the tensile residual stresses or even change them to the compressivestresses Hydrotest and quenching processes are of the most effective and usual post weldingmethods to protect SCC The main goal of this dissertation is to simulate welding hydrotest and quenchingprocesses of the direct seam pipes by using finite element method in order to estimate residualstresses after any of processes Two quenching process is mentioned and compared the first isthe Hoesch method and the second is the last pass heat sink welding LPHSW method Wholethe processes are simulated on ANSYS commercial software developing related ANSYScodes macros The processes are simulated using 2D and 3D models Because of complexityof the problem 3D simulations are very time consuming and so these models are not as usefulas 2D models for practical application In this research a new method is proposed in order toreduce computational requirements of the problem both for 2D and 3D models The idea is todefine some equivalent thermo physical properties for some parts of the pipe body andomitting rest of the elements far from the HAZ In this regard the equivalent elements shouldbe defined using orthotropic material Metallurgical phases determined by simulations agreewith results of the metallographic photos of the samples cut from the real pipe The appliedmethod is also verified by comparing the numerical results by the experimental results foundin the literature Results show very high residual stresses after SAW process From thesimulation of the post welding processes it could be concluded that the hydrotest process willdecrease tensile residual stresses even quenching using Hoesch method will change them tocompressive stress but LPHSW has not noticeable effect on the residual stresses

محمدرضا فروزان

احمد كرمانپور

محمود سليمي، سعيد ضيائي راد