Regular Variation Of Neutral Layer Offset Of Thick Plate Nickel-base Alloy During JCO Forming

Nickel-based alloys have the advantages of high temperature corrosion resistance,strong plasticity and hot and cold forming,so nickel-based alloy thick-walled tubes have a wide range of applications in the transportation of natural gas and oil.In the past twenty years,manufacturing industry has developed greatly,and the domestic demand for nickel-based alloy sheets has been increasing.In the thick-walled tube forming process technology,the main use is UO forming and JCO forming,for UO forming process has the advantages of high yield,high production efficiency,but only for a single specification mass production;and JCO forming process has the advantages of low investment,applicable to a variety of specifications for mass production,etc.,because in the JCO forming process,the multi-pass bending process will affect the quality of billet forming,ignoring the neutral Therefore,this paper studies the change law of neutral layer offset in JCO forming process of thick plate,and derives the formula of neutral layer offset applicable to thick-walled pipe forming to improve the appearance quality of thick-walled pipe after JCO forming.JCO forming is progressive multi-step bending forming,which is a multi-step and continuous bending forming process,divided into symmetric and asymmetric press bending.Firstly,based on the elasto-plasticity theory and the bending mechanism of medium-thick plate,the neutral layer offset formula is established from the thickness-oriented strength theory.Secondly,symmetric and asymmetric press bending models were established using ABAQUS finite elements,and the variation law of neutral layer deflection at different plate thicknesses was analyzed at the same press down amount according to the simulation results;at the same thickness,the variation law of neutral layer deflection at different press down amounts of the plate was analyzed.Finally,symmetric and asymmetric three-point bending experiments were conducted to collect experimental data and obtain the variation of neutral layer deflection for different thicknesses and bending amounts.It is compared with the variation law obtained by numerical simulation and theoretical calculation,which facilitates the subsequent correction of the theoretical neutral layer offset calculation formula.To provide the theoretical basis and practical basis for the JCO forming process of nickel-based alloy thick plates.