Study On The Anisotropy Of Medium-thick Plate Metal Used For Fine Blanking

With the rapid growth of automotive industry, fine blanking, which can produce complex spare part with uneven thickness, has been widely used in medium-thick sheet plate metal production. Numerical simulation is an important morden method to solve forming process design and tool development in fine blanking. The accuracy of the material will affect the accuracy of numerical simulation. Medium-thick steel sheet used in fine blanking is generally made by rolling and following spheroidizing annealing. Due to deformation texture formed in the rolling process, the mechanical properties of the metal will exhibits anisotropy, which will still exist after spheroidizing annealing. Obtaining flow stress curve with smaller strain range and anisotropy parameters for thin sheet has developed systematic theory. However there is no systematic theory to study medium-thick sheet, which needs flow stress curve with larger strain range and overall anisotropic parameters.To the question described above, flow stress curves with larger strain range in major directions are used to illustrate the anisotropy of medium-thick steel sheet plate. On the one hand, traditional material property test methods(such as uniaxial tensile test and cylinder compression test) are used to get basic data in different orientations; On the other hand, inverse analysis is used to combine traditional material test and numerical simulation to push the boundaries of traditional methods to get flow stress curves with larger strain range and better accuracy.Sample points settings, flow stress model and optimization algorithm have been studied to deal with the problems, which include nonlinearity, uncertainty(existence, uniqueness and stability) and large computational cost, of cylinder compression inverse analysis. It is found 20 sample points have both higher accuracy and efficiency.Swift flow stress model, which has better parameter sensitivity, can be used well.Downhill Simplex have better performance among 10 optimization algorithms.Based on the mentioned research result, C45 and 42CrMo4, which are commonly used in fine blanking, are tested. Tensile test of C45 specimens with different thickness layer shows material property do not change by thickness layer. The flow stress curve comparison of tensile test, traditional compression test and inverse analysis, which includes specimens of different size, shows the accuracy of inverse analysis. Inverse analysis has been done to 42CrMo4 specimens of 6 orientations, which includes 3 major directions and 3 tangential directions. 6 flow stress curves of larger strain range and anisotropic parameters have been got accordingly EBSD has been done to study microstructure and texture of 42CrMo4, which match well with anisotropic result of flow stress curves.Finally, flow stress curves of larger strain range and anisotropic parameters of 42CrMo4 have been used in numerical simulation of fine blanking. The comparison of rim-hole experiment and simulation shows flow stess curve and anisotropy parameters obtained from inverse analysis are better than those got by tensile test.