Formability prediction of tailor-welded blanks in hydraulic bulging using flow curves from biaxial tensile tests

Abstract

In this work, the formability of laser-welded tailored blanks of low carbon steel of two different thickness combinations in hydraulic bulging has been studied by numerical simulation. For material modeling, flow curves of the parent sheets were obtained in biaxial stress condition by conducting hydraulic bulge tests. These curves were used to extrapolate the uniaxial tensile curves up to large strains using the work equivalence principle. The limiting dome height in conventional forming and hydraulic bulging of tailor-welded blanks has been predicted in finite element simulations using the flow curves obtained directly from the hydraulic bulge tests and the extrapolated uniaxial tensile curves. Hydraulic bulging and conventional forming experiments on tailor-welded blanks have also been conducted to validate the predicted results. It has been found out that the predicted limiting dome height of the tailor-welded blanks in conventional forming and hydraulic bulging using extrapolated uniaxial tensile curves is closer to the experimental values when compared to the results obtained by using stress–strain curves obtained from hydraulic bulge tests. It has also been found that using an extrapolated uniaxial tensile curve it is also possible to predict strain distribution and percentage thinning more accurately. It has been observed that with an increase in thickness ratio, the peak pressure increased but the predicted values of peak pressure using flow curves obtained directly from hydraulic bulge tests are closer to the experimental values.