EvaluationonweldingcoldcrackingofY-typenodeofoffshoreplatformjacket

Feng Chao1,2，Zhao Lei1,2，Xu Lianyong1,2，Han Yongdian1,2，Guo Huijuan1,2

(1.Tianjin University, Tianjin 300350, China; 2.Tianjin Key Laboratory of Advanced Joining Technology, Tianjin 300350, China).p1-6

AbstractDue to the inhomogeneity of offshore platform structure and the limitation of welding technology, the welded joints were prone to appear cold cracks.For the problem, based on SYSWELD, the weld of typical Y-joints of offshore platform jacket made of E36 high strength steel was modeled and the welding process was numerically simulated in the paper.According to the stress field, the restraint stress was obtained, so as to realize the quantitative evaluation of its cold cracking.The heat source model was applied through the thermal cycle obtained by the heat source check, and then the changes of axial, circumferential and radial restraint stresses along the intersection line at the weld root and the weld toe were analyzed and the restraint stress of dangerous points in each direction were compared with the critical restraint stress of the material.The results showed that the maximum restraint stress was 492 MPa, which was less than the critical restraint stress of E36 high strength steel.That was to say, there would be no delayed cracking at the root and toe of Y-joints.

Keywords:offshoreplatform,Y-joint,coldcracking,restraintstress

SpotweldingnuggetandresidualstressofSUS301Lthinplateswithunequalthickness

Li Yana, Jian Zhisong, Liu Jiahao, Zhang Shengfang

(Dalian Jiaotong University, Dalian 116028, Liaoning, China).p7-11, 16

AbstractAiming at the welding quality and strength of thin plates with unequal thickness in railway vehicle manufacturing, spot welding process of SUS301L thin plates with unequal thickness was simulated by special welding software in this paper.Based on the comparison between the simulation results and the experimental results, effects of welding current, electrode pressure and welding time on the equivalent stress after welding were studied.The feasibility of the simulation model was verified by nugget size comparison.The result showed that the distribution of high stress zone after welding expanded with the increase of current and time, the high stress area decreased after welding with the increase of electrode pressure.This research provided process reference for spot welding of SUS301L thin plates with unequal thickness and it was of great engineering significance in railway vehicle manufacturing.

Keywords:spotwelding,thinplateswithunequalthickness,SUS301L,nuggetsize,equivalentstress

EffectofgrindingmethodsonfatiguepropertiesofSMA490BWweatheringsteelcrossweldedjoints

Wang Lei1,2, Zeng Hongrun1,2, Liu Xiaopeng1,2, Hui Li1,2, Cong Jiahui1,2

(1.Shenyang Aerospace University, Key Laboratory of Fundamental Science for National Defence of Aeronautical Digital Manufacturing Process, Shenyang 110136, China;2.College of Mechinical and Electrical Engineering, Shenyang Aerospace University, Shenyang 110136, China).p12-16

AbstractThe SMA490BW weathering steel cross welded joints were ground in different ways.The effects of different grinding methods on fatigue properties of SMA490BW weathering steel cross welded joints were studied, and the fatigue fracture morphology was studied by SEM.ABAQUS finite element software was used to calculate the stress distribution and stress concentration coefficient of cross welded joints.The results showed that the fatigue limit of unground specimens was about 70.6 MPa, that of simple ground specimens was about 98.6 MPa, and that of transition arc ground specimens was about 104.4 MPa.The fatigue limit of simple ground specimens and transition arc ground specimens was 39.7% and 47.9% higher than that of unground specimens, respectively.The stress concentration coefficients of unground, simple ground and transition arc ground toe were 1.558, 1.402 and 1.297, respectively.The stress concentration coefficient of simple ground and transition arc ground was reduced by 10.0% and 16.8%, respectively.

Keywords:SMA490BWweatheringsteel,fatigueproperties,crossweldedjoint,stressconcentrationfactor

NumericalsimulationofresidualstressincircumferentialweldofX80pipeline

Ge Hua1, Huang Haibin1, Jiang Yi1, Zhang Shuo1, Cao Yuguang2, Si Weishan2

(1.Pipe China Southwest Pipeline Company, Chengdu 610041, China; 2.China University of Petroleum, Qingdao 266580, Shandong, China).p17-23

AbstractABAQUS software was used to simulate the circumferential weld welding of X80 natural gas pipeline with a diameter of 1 016 mm in 1-layer-1-pass, 4-layers-4-passes and 6-layers-6-passes.When the wall thickness of the pipeline was fixed, the variation trend of axial and circumferential welding residual stress on the inner and outer surfaces of the pipeline was studied with the change of the number of welding layers.Then, the post welding heat treatment of the pipeline was simulated to investigate the variation law of residual stress after heat treatment.The results showed that when the number of welding layers increased, the welding residual stress in the high stress area of circumferential weld section decreased as a whole.The circumferential stress distribution law on the inner and outer surfaces was changing from tensile stress to compressive stress as a whole.Being different from 4-layers and 6-layers welding, the axial stress on the outer surface of 1-layer welding pipe was always compressive stress.After heat treatment, the peak value of axial stress on the outer surface could be significantly reduced by 51.5%.The peak value of circumferential stress on the inner surface could be significantly reduced by 65.1%.

Keywords:X80naturalgaspipeline,circumferentialweldwelding,weldingnumericalsimulation,postweldheattreatment

Effectofdouble-sideddepositionondeformationandstressofwirearcadditivemanufacturingwallparts

Zhou Xiangman, Qin Jingping, Tian Qihua, Du Yixian, Fu Junjian

(China Three Gorges University, Yichang 443002, Hubei, China).p24-28, 35

AbstractAiming at the problem of unidirectional heat accumulation caused by unidirectional stacking in conventional wire arc additive manufacturing(WAAM), a double-sided deposition strategy was proposed in this paper, namely the same material was alternately deposited on both sides of the substrate to balance the larger bending moment around the neutral axis of the formed part generated by the unidirectional heat input of the traditional single-sided deposition, so as to reduce the large deformation and residual stress of single-sided deposited parts.The above strategy was verified by thermal-mechanical coupling numerical simulation and corresponding experiments of single-sided and double-sided deposition of single-pass four-layer wall parts.The result showed that double-sided deposition could effectively reduce deformation of substrate and parts, improve the residual stress distribution of wall parts, which could verify the effectiveness of the proposed strategy.The conclusion in this paper could provide theoretical basis and reference for the parallel control of “shape and performance” in WAAM.

Keywords:wirearcadditivemanufacturing,wallparts,double-sideddepositionstrategy,deformation,stress

Researchstatusofsolidificationcracksinlaserweldingofhigh-strengthsteel

Han Pengbo, Huang Ruisheng, Li Xiaoyu, Yang Yicheng, Sun Jingtao

(Harbin Welding Institute Limited Company, Harbin 150028, China).p29-35

AbstractHot cracks, mainly solidification cracks, occurred when laser welding, laser wire filling and laser-arc hybrid welding were used in high strength steel welding.For the problem in the paper, the research status of solidification crack in high-strength steel by laser welding and laser-arc hybrid welding in recent years was comprehensively discussed, characteristics, formation mechanism and preventive measures of solidification cracks were introduced.According to the current research results, the solidification cracks in laser welding of high-strength steel were mainly longitudinal cracks in the weld.The formation of solidification cracks was mainly studied at home and abroad from four influence factors of chemical composition, molten pool geometry, welding parameters, and restraint intensity.The focus was on the influence of convex part and depth-to-width ratio of the molten pool on the formation of solidification crack.The convex part would cause solidification delay, generate large tensile stress, and promote the segregation of S and P impurity elements.Larger depth-to-width ratio would cause local stress concentration and then cause cracks.Changing the weld geometry by different techniques was an important direction to solve the solidification cracks in laser welding.

Keywords:high-strengthsteel,laserwelding,solidificationcracks,formationmechanism,preventivemeasures

Simulationofresidualstressdistributioninmultilayerandmultipassrepairweldingofthick-wallsteelcastings

Liu Bo1,2

(1.Jiangsu University, Zhenjiang 212013, Jiangsu, China; 2.Sinopec Tianranqi Company, Beijing 100029, China).p36-41

AbstractIn order to reduce the residual stress after repair welding of steam turbine cylinder in service, the residual stress distribution of defective thick-wall steel castings after multi-layer and multi pass repair welding was simulated by the birth and death element technology in ABAQUS.Under the condition of ensuring the accuracy, the segmented heat source model was adopted to study the thermal cycle curve of repair welding process and the distribution of welding residual stress in the three-dimensional model of thick-wall steel casting.The effects of different preheating temperature and different layer thickness on the residual stress distribution in the repair welding area were analyzed, and the more reasonable preheating temperature range and the corresponding welding repair method matching the layer thickness and the number of layers were obtained.

Keywords:thick-wallsteelcastings,repairwelding,residualstress

Numericalsimulationonlaserhybridweldingdeformationofsidewallsoftrainbodybasedoninherentstrainmethod

Song Kunlin1, Zhan Xuhe1, Xu Liang2, Yang Haifeng2, Cui Hui2

(1.National Innovation center of High Speed Train, Qingdao 266109, Shandong, China; 2.Harbin Welding Guochuang(Qingdao)Welding Engineering Innovation Center Co., Ltd., Qingdao 266109, Shandong, China).p42-47, 52

AbstractBased on inherent strain method, 3D Gaussian + double ellipsoid heat source model was used to predict laser hybrid welding deformation of 8 m side wall components of a high-speed train under different welding sequence and constraint modes.The results showed that deformation in the thickness direction of side walls was greatly affected by welding sequence, and it could be reduced by about 13% after optimizing the welding sequence.The welding constraints had obvious influence on the arc profile and arc chord width of the side wall components, but had little influence on the overall length.Compared with unconstrained condition, the maximum deformation in the thickness direction was reduced to 25%, and the maximum deformation in the width direction was reduced to 10%.The comparison between simulation results and test results showed that the heat source model selection of the side wall component under its process conditions was effective and reasonable, and the numerical simulation of the measurement points was in good agreement with the actual tests, with the absolute error less than 1 mm.

Keywords:inherentstrainmethod,laserhybridwelding,sidewallsoftrainbody,weldingdeformation

Spatiallocationvisualizationofbulkdefectsforbuttjointweldment

Shi Duanhu1, Wu Sanhai1,2, Li Changyun2, Sha Jing1, Sun Yuan1, Yang Feng1

(1.Xuzhou University of Technology, Xuzhou 221111, Jiangsu, China; 2.Henan Polytechnic University, Jiaozuo 454000, Henan, China).p48-52

AbstractMathematical model of defects depth and deviation for butt joint weldment was established, and the spatial position of defects was determined.Mathematical model of weld profile was provided, and perfect presentation of weld profile was achieved.Defects visualization interface of butt joint weldment was designed, and the butt joint weldment model was established, after the bulk defects of automatic extraction for butt joint weldment were import, the spatial position of bulk defects of butt joint weldment was reappeared.Adjustment of weldment parameters, visualization angle and transparency were introduced, and the three views of visualization model were shown, which could provide better basis for defects repair, welding procedure setting, defects spatial distribution feature research and structure integrity evaluation of butt joint weldment.

Keywords:buttjoint,defectslocating,mathematicalmodel,bulkdefects,defectsvisualization

On-lineintelligentrecognitionoftypicalweldingdefectsdrovebymulti-sourceinformation

Deng Gang1, Ma Zhi2, Chen Weiguang3, Liu Yu2, Chen Huabin3

(1.CRRC Changchun Railway Vehicles Co., Ltd., Changchun 130062, China; 2.CRRC Industrial Academy Co., Ltd., Beijing 100160, China; 3.Shanghai Jiao Tong University, Shanghai 200240, China).p53-59

AbstractIn order to avoid defects such as burn-through, incomplete fusion, wire blocking and slag inclusion appearing in welding process of bogie, the information acquisition system of bogie robot MAG welding process was constructed, which could collect real-time weld pool image, arc sound and voltage information.Key features closely related to quality were extracted and knowledge modeling and fusion analysis were carried out based on XGBoost model.Finally, the ability of information perception and quality analysis similar to welding masters were realized, and the comprehensive accuracy could reach more than 90%, thus improving the quality reliability and intelligent manufacturing level of bogie welding operation.

Keywords:intelligentwelding,defectrecognition,informationfusion,bogiewelding