The Force And Energy Prediction Model And Deformation Law Research Of BFe10-1-1 Cupronickel Pipe Diameter Expansion

BFe10-1-1 copper pipes are widely used in marine engineering because of their excellent corrosion resistance.For example,the development of large warships and ships requires a large number of large-caliber copper-nickel alloy pipes.In general,large-caliber copper-nickel alloy tubes are obtained by expanding technology,but BFe10-1-1 copper tubes have high nickel content and poor plastic processing performance,which leads to poor stability of production quality of large-caliber copper tubes.Therefore,the study of the deformation law and the influence of key parameters on the expansion of copper-nickel alloy pipes has a guiding significance for the development and optimization of the expansion process of copper-nickel alloy pipes.The prediction model of expanding force is established more reasonably by combining theoretical analysis,numerical and simulation,and the deformation law of BFe10-1-1 pipe during expanding process is revealed,The theoretical and simulation prediction results are verified by experiments.research contents are as follows:1)The stress state of the tube during pressing and stretching is analyzed.The rigid-plastic hardening curve model is adopted by the principal stress method.The force prediction models of flaring(Fp)and tension expanding(Fd)are established respectively.Research shows:The extrusion force and drawing force increase with the increase of expansion ratio,wall thickness,radius and friction coefficient.The main factors affecting the extrusion force and drawing force are the expansion coefficient.When the die angle is small,the model can predict the expansion force better.The error between the predicted model and the experiment was less than 11.1%.2)Based on ABAQUS,the finite element model of indentation and stretching expanding is established,and the influence of key parameters(expansion coefficient,friction coefficient,die angle,wall thickness and inner diameter)on the physical field of deformation in the process of expanding is explored.The simulation results show that:The distributions of radial stress and circumferential stress along the axial direction are basically the same in the case of indentation and stretching enlargement.The main difference is the distribution of axial stress.According to the distribution of radial stress,the grooves with annular depression are easily formed at the first contact position between the inner wall of the die core and the conical surface of the die core.The enlargement force decreases first and then increases with the increase of die angle,and increases linearly with the increase of enlargement coefficient,friction coefficient,wall thickness and pipe diameter,among which the enlargement coefficient has the greatest influence.During the process of flaring,the thickness of the tube wall increases near the core,and then decreases continuously until the core is separated.During the process of expansion,the wall thickness of the tube keeps decreasing from the inner wall close to the die core until it is separated from the die core.The error between the finite element simulation and the experiment was less than 2.1%.The simulation results matched well with the test results in pipe size and pipe shape.3)In the range of parameters studied(K0=1.2?1.6;?=12 °?36 °),the main flaring defect is the local fold,and the instability of the pipe depends mainly on the expansion ratio.When the expansion ratio is less than 1.6,the bigger the die angle is,the shorter the length of the pipe after expansion,and the bigger the actual expansion ratio is.When the expansion ratio is greater than 1.6,folds begin to appear,and the larger the die angle,the more the number of folds.When the cross-section is eccentric or irregular,the equivalent stress and strain at all parts of the cross-section are larger than those of the regular round cross-section,and the value of equivalent stress and strain and the thinning rate of wall thickness gradually increase from the wall thickness to the wall thickness,which is the largest at the wall thickness.This leads to the increase of eccentricity and the increase of geometric size defects after expansion.