Analysis On Laser Spot Weld Bonding Process And Joint Strength Of Steel DP590

Laser spot weld-bonded is a new material joining process,which combines laser spot welding with a layer of structural adhesive in a single joint.It has excellent dynamic and static bearing capacity,especially sealing properties.In this paper,1.5 mm thick DP590 steel is choosed as material for welding by high power fiber laser equipment.The connection technology,mechanical properties,and fatigue strength of the joints were researched.Laser spot welding and laser spot weld-bonded were performed.The orthogonal experiment method was adopted to study the influence on joint strength of different welding parameters.The optimum parameter combination,welding power:1800 W,welding time:200 ms,defocusing amount:+3 mm,was obtained in laser spot welding test.The optimum parameter combination,welding power:1400 W,welding time:1000 ms,defocusing amount:+3 mm,was obtained in laser spot weld-bonded test.The simulation model of laser spot weld-bonded joint was built by AUTODYN to investigate the dynamic impact effect of gasified adhesive on welding pool.The results prove that the viscosity decreases with the viscoelastic decay constant increase.The maximum pressure on the inspecting spot showed a tendency to increase in pressure curves of gauges.The surface of joints have different conditions,such as perforation,nodulation,and smooth.The simulation results agree well with the accident sestruction features and the simulation method was thus verified.Evidently,the simulation can describe the evolution process under different condition.By range analysis and ANOVA analysis,the effect on peak load,peak displacement and energy absorption value of different welding parameters is investigated.The results showed that welding time has the greatest effect on mechanical properties,next comes welding power followed by defocusing amount in laser spot welding test.In laser spot weld-bonded test,welding power has the greatest effect on mechanical properties,next comes welding time followed by defocusing amount in laser spot welding test.By using fatigue test machine,fatigue properties of laser spot welding joints,laser spot weld-bonded joints,and adhesive joints,is done with 10 Hz and load ratio of 0.1.The results shown that the fatigue strength of different joints are orderly:laser spot weld-bonded joints,laser spot welding joints,adhesive joints.The SEM analysis was applied to analyze the tensile fracture of the laser spot welding joints and laser spot weld-bonded joints.Toughness fracture appears on tensile fracture of laser spot welding joints.There are brittle failure and toughness fracture on tensile fracture of laser spot weld-bonded joints.Especially,fatigue fracture are both brittle failure.The quality of joints of laser spot welding joints and laser spot weld-bonded joints was investigated using scanning acoustic microscopy.C-scan images were obtained to characterize the weld evolution characteristics of welds formed under different welding parameters,and A-scan signals of feature regions were collected and analysed.The A-scan signals in different feature regions were distinct from each other,and three regions in the laser spot welding joints were distinguished on the basis of the A-scan signals and the C-scan images:the weld nugget zone,the heat-affected zone and the fusion zone.Four regions in laser spot weld-bonded joints were distinguished:the weld nugget zone,the heat-affected zone,gasification zone and adhesive zone.Based on the variation characteristics of gray value of joints,the nugget diameter of welding joints are measured.The variation range of laser spot welding joints is from 0.66 mm to 2.73 mm.The variation range of laser spot weld-bonded joints is from 1.23 mm to2.51 mm.