A method to simulate multilayer welding process: Node dynamic relaxation method A method to simulate multilayer welding process: Node dynamic relaxation method

A method to simulate multilayer welding process: Node dynamic relaxation method

  • 期刊名字:中国焊接
  • 文件大小:759kb
  • 论文作者:Gao Jiashuang,Yang Jianguo,Fan
  • 作者单位:State Key Labortory of Advanced Welding Production Technology,Zhejiang Qianjiang Motorcycle Co.
  • 更新时间:2020-11-11
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论文简介

42CHINA WELDING Vol. 18 No. 3 September 2009A method to simulate multilayer welding process:Node dynamic relaxation methodGao Jiashuang, Yang Jianguo, Fang Hongyuan, Hu Junfeng and Wang Tao高嘉爽,杨建国,方洪渊,胡军峰,王涛*Abstract A new method clled node dynamic relaxation is proposed to simulate mutilayer welding. A too dimensional planestrain model for mulilayer wvelding is simulated and the results show that mesh distortion can be decreased, and it is alsofound that the node dynamic relaxation is a kind of method to calculate welding deformnation accurately by comparingexperiment results with simulation results.Key words finite element analysis , multilayer welding, node dynamie relaxation0 Introductionfor multilayer welding is the main issue(2-s).Welding technology is widely used in materials pro-Fig. 1 shows the welding process. With welding heatcessing engineering. Welding deformnation and residualsource moving along welding direction, Zone A was divid-stress are key factors that markedly afect mechanicaled into three different zones called respectively weldedproperties and fatigue behaviors of welded joints, s0 it iszone, weld pool zone and non-weld zone. Further, thosevery important to forecast welding distortion and residualelements of welded zone and weld pool zone should be ac-stress effectively before actual welding operation.tivated since they have been“added" to the model, theMultilayer welding is widely used to thick plate, so itelements of non-weld zone are still “ dead" because flleris thought that mathematical modeling is important. Usual-material have not yet been“ added" , although there stillly, there are two methods to support the definition of fil-exist elements in non-weld zone.ing elements for welding finite element analysis, one is de-active element method, and the other is quiet element/Weldmentmethod"I.| Non-weldThis paper proposed an effective and convenientzonmethod called node dynamic relaxation method to simulateWeldpoolmultilayer welding, which can obtain accurate simulationresults.WeldedzoneZone A1 Node dynamic relaxation method220.1.1 FEA for multilayer welding processObviously, it is necessary to calculate temperature,Fig.1 Schematic diagram of welding processstress and deformation fields of multilayer welding usingThe relation between nodal force {f*} and nodal dis-FEA, however, it is difcult to simulate flling processwhich looks like be deposited layer by layer, now whichplacement {S; } can be obtained by sifness matrix [K"]method can be used to simulate liquid metal flling processmultinlving a siffness cofficient λ. as fllows, where λ, is中国煤化工* Gao Jiashuang, Yang Jianguo, Fang Hongyuan and Wang Tao, StateMHc N M H Gng Paucto Tchnbog,,Harbin Istite of Technology, Harbin, 150001. Hu Junfeng, Zhejiang Qianjang Motoreycle Co. , LTD, Wenling, 310002. GaoJiashuang, Corresponding author, E- mail: gajiashuang2005@ yahoo. com. cnA method to simulate multilayer welding process: Node dynamic relaxation method43used to judge the element whether it is active or deactive.Fig.3 shows elastic links of the weld fller nodes whenmultilayer welding is simulated.f"} =λ[K]{S}(1)Spring linksIn fact, FE ( finite element) program does not re-move“ dead" elements, but “ kill" them by muliplyingtheir sifness (or conductivity, or other analogous quanti-ty) with a severe reduction factor λ, Element loads asso-ciated with deactive elements are zeroed out of the loadvector, however, they still appear in element-load lists.Similarly, mass, damping, specific heat, and otherWeld fller nodessuch properties are set to zero. The mass and energy ofdeactive elements are not included in the summations overFig. 3 Elastic links of weld fller nodesthe model. Element strain is also set to zero as soon as theelement is“klled".1.3 FEA resultsA two dimensional plane strain model for multilayer1.2 Principle of node dynamic relaxation methodwelding is built in order to analyze the calculation accura-A new method called node dynamic relaxation methodcy and efficiency of node dynamic relaxation method ,is developed to simulate weld process which involves a setwhich contains 1 086 elements and 1 317 nodes, process-of virtual elastic system, and it can coordinate mesh dis-ing time is 7 000 s, the width of two-dimension plane istortion between fller elements. It can be interpreted as300 mm and thickness is 20 mm. Fig. 4 shows the final ge-Fig. 2: There are two same triangle elements , two springsometry shape by node dynamic relaxation method. Smallare added between node m and l, j and l respectively,mesh distrtions occurred, so it is proved that node dy-node m and j moves with node i under the two springsnamic relaxation is a kind of effective method to decreaseforce as the triangle I still “died" . Thus“dead" elementmesh distortion between active and deactive element.looks like move with active element, and it is useful for a-voiding mesh distotion by coordinating distortion betweendeactive and active elements. For multilayer welding, themethod can effectively decrease serious mesh distortion.◆yFig.4 Final geormetry shape by node dynamicu0.▲relaxation metbodn”Further , weldment surface stress field is also studied,as shown in Fig 5. The amplitude of stress curve near weldseam, whether transverse stress ( Fig.5a) or longitudinalnode dynamic relaxa-tion r:YH中国煤化工iaion cuve by node .dynamcNMHGbethesamesquietelement method.Fig.2 Two triangles with two elastic links44CHINA WELDING Vol. 18 No, 3 September 2009一o- Quiet element method80- a - Quiet element method1 2000- Node dynamic relaxation method700-。- Node dynamic relaxation method1000-0- Deactive elegnent method--Deactive element method60050080040030020010000t-100-150 -100 -50 0 50 100 150Distance from weld centerine 1 mmDistance from weld centerline 1 mm(a) Transverse stress(b) Longitudinal stressFig.5 Comparison of weldment surface stress in multilayerwelding with three methods2 Experiments300 mm and thickness is 16 mm (Fig. 6) and material isThe accuracy of node dynamic relaxation method islow-carbon steel Q235, it contains 6 layers and 12 passes.verified by experiment. Mulilayer weldment is welded inWelding parameters are show in Table 1.the form of butt joint, whose length is 420 mm, width is420(a) Cross-section view(b) Top viewFig.6 Weldment photoTable 1 Welding parametersWelding currentWelding speedWire feed rateCas flow rate/A/mm●min/mm●min'/L. min-'Backing weld2601800015Filling beadWelding deformation is studied by using experiment well中国煤化工that welding deforma-method and node dynamic relaxation method. It is seentionMHCNM H Gie eaxtin mehod.that the experiment value and the simulation value agreeA method to simulate multilayer welding process : Node dynaamic relaxation method45-- Node dynamic relaxation method(2) Experiment is done in order to venify the accu-0● Experiment methodracy of node dynamic relaxation method, and the resultshows that welded joint shape is similar to actual one.-0.1Furthermore , weldment surface deformation is discussed-0.2by experiment method and node dynamic relaxation meth-od, respectively, it shows that the experiment value agrees-0.3with the simulation value well.-0.4References-160-120-80-40 0 40 80 120 160[1] Lindgren L E, Runnemalm H. Simulation of multipass weld-ing of a thick plate. International Journal for Numerical Meth-Distance from weld centerline 1 mmods in Engineering, 19, 44: 1 301 -1316.[2] Rybicki EF, Schmueser D W, StonesifleRB, et al. FiniteFig.7 Displacement along weld widthelement model for residual stresses and deflections in girth-butt welded pipes. Journal of Pressure Vessel Technology ,3 Conclusions1978, 100(3): 256 - 262.(1) Node dynamic relaxation method for mulilayerRybicki E F, Stonesifer R B. Computation of residual sresseswelding simulation was proposed which solves a problemdue to multipass welds in piping systems. Joumal of Pressurefor coordinating distorion between the node displacementVessel Technology, 1979, 101(2): 149 -154.of deactive element and active element. A multilayer weld-[4] Rybicki E F, Stonesifer R B. Analysis procedure for predic-ing example is studied by this method and it is found thating weld repair residual stresses in thick-walled vessels.the deformation between the deactive element and the ac-Jourmal of Pressure Vessel Technology, 1980, 102(3): 323tive element is coordinated , mesh distortion is decreased,-331.Troive L, Nastrom M, Jonsson M. Experimental and numer~thus it is proved that the node dynamic relaxation methodical study of mulipass welding process of pipe -lange joint.can obtain accuracy simulation results of multilayer weld-Journal of Pressure Vessel Technology, 1998, 120(3): 244ing.-251.中国煤化工MYHCNMHG

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