Multi-objective Optimization Method Of Laser Welding Process Parameters For Dual-phase Steel Towards Low Carbon Manufacturing And Its Application

Using high energy density laser beam as the heat source for welding,laser welding is a kind of welding processing method with high flexibility,high quality,and high energy density,and has been widely applied in automobiles,aerospace,energy,and other fields.However,there are still some problems in laser welding technology,such as low energy conversion efficiency,low material absorption rate,high carbon emission,high initial investment of equipment,high maintenance cost,et al.,while laser welding technology developing to today.Lots of studies only aim at the laser welding process itself to improve the welding quality,which lacks the consideration of its environmental impacts and economic benefits.The environmental impacts and economic benefits of laser welding systems are not well understood,thus the low carbon application and energy saving optimization of laser welding system are seriously affected.Therefore,it is urgent to realize the collaborative optimization towards the environmental impact,economic efficiency,and welding quality.For this purpose,a multi-objective process parameter optimization model of laser welding system is proposed in this paper through comprehensively considering the environmental impact,economic benefit,and welding quality of laser welding system and it is optimized by combining theoretical research,experiment,and algorithm.The main work is as follows:Firstly,the evaluation model framework of carbon emission,welding cost,and welding quality of laser welding system was proposed by comprehensively considering the environmental impact,economic benefit,and welding quality.The carbon emission evaluation model was established,based on the thermodynamics,statistical,and mechanism of the welding process.The welding cost evaluation model was established considering the equipment depreciation,equipment maintenance,artificial cost,resource consumption,et al.The welding quality was synthetically characterized by weld surface roughness and weld depth-width ratio,and the welding quality evaluation model was established based on surface response method.Then,regarding the laser power,welding speed,and defocusing distance as variables,and carbon emission,cost,and quality as optimization objectives,a multiobjective process parameter optimization model of laser welding was established.Next,the non-dominated sorting genetic algorithm-II(NSGA-II)is proposed to solve the model,which can obtain the optimal range of welding parameters and shrink the process window.The decision-maker can choose the best process parameters according to the actual situation.Finally,based on the Box-Behnken experimental design method,laser welding experiments of DP980 dual-phase steel were carried out to verify the accuracy of the carbon emission model and establish the fitting relationship models of weld surface roughness and weld depth-width ratio with process parameters.Also,the effects of laser power,welding speed,and defocusing distance on each evaluation model were analyzed.Then,the multi-objective optimization was carried out based on the NSGA-II algorithm to obtain the optimal process parameter combination.