Research On Theory And Technology Of Short-flow Direct Hot Roll Bending Of Rectangular Tube

Steel structure buildings gradually replaced the dominant position of concrete constructions,accompanied by the rapid development of our country's economy,which has become the mainstream trend of the development of the construction industry in my country and even the world.Rectangular pipes account for the largest proportion of steel structure buildings.The current main forming process for producing rectangular tube is roll forming,which is divided into two forms: direct square and round first.Although the production of rectangular tubes is relatively mature.However,it is difficult to produce rectangular pipes with large wall thickness,large specifications and high strength by cold roll forming in China at this stage.There are a lot of problems in the production process,such as large deformation resistance and poor plasticity and the like.Defects appeared in the product such as stress concentration at the corner,large springback,and serious corner thinning.Q345 B board has the characteristics of high strength,high toughness,corrosion resistance,excellent weldability and formability and the like,which is the most typical metallic material metal for steel structure.In view of the above situation,this article take Q345 B board as research objects,put forward the application of hot roll forming process for direct square forming of steel plate after rolling with residual temperature,and prepare a rectangular tube with high strength,large size and large wall thickness.This article intends to commence the study in the following four aspects:(1)Build temperature-dependent,strain-dependent and strain rate-dependent constitutive model and temperature-dependent changeable elastic modulus model.Provide the necessary theoretical basis for hot roll bending simulation.According to the required temperature,perform thermal compression experiments to obtain experimental data,establish constitutive model.Temperature-dependent changeable elastic modulus model,measure the elastic modulus at different temperatures according to the resonance method,get the change trend through fitting.(2)The select of the related parameter of rectangular tube forming unit and the flower molding design,according to the relevant parameters of the cold bending process,make adjustments to meet the requirements of required size rectangular tube for the simulation.(3)Perform a finite element simulation using ABAQUS simulation software,contrastive analysis of cold roll bending and hot roll bending based on the results.Conduct a comparative analysis of cold roll bending and hot roll bending,establish three models,cold bending,hot bending,hot bending real bending model,according to the content of(1)and(2),build a finite element model,analyze equivalent strain,stress,forming force,strain,springback amount,corner thickness reduction and the like based on the simulation results.(4)Contrastive analysis of numerical simulation results and hot bend test,analyze the parameter of springback amount,corner thickness reduction and the like,verify the finite element model correctness.Through the combination of simulation and experimental verification,the hot roll forming process of square rectangular tube in steel structure building is studied,which verifies that hot roll forming has advantages over cold roll forming,and provides a theoretical basis for subsequent hot roll forming research.