Effect of Plastic Strain on Anisotropic Behaviour of AISI202

Aims: In the present study an attempt has been made to determine the effect of plastic strain on the anisotropic parameters of AISI202 series.
Study Design: The parameter commonly used to characterize the anisotropy of sheet metal is the plastic strain ratio i.e. the ratio of true width-strain to thickness-strain. Accurate determination of plastic strain ratio is difficult as it is influenced by percentage elongation given to the specimen during uniaxial tension test. Moreover, AISI202 shows approximately 60% of uniform strain during tension test and no necking is observed at all, which adds to the problem in accurate determination of anisotropic parameter.
Place and Duration of Study: Samples were tested at Plasticity and Metal Forming Laboratory, Department of Mechanical Engineering, Delhi Technological University (DTU), New Delhi, between January 2014 and April 2014.
Methodology: Tensile specimens were laser cut from 0.8mm thick sheet in the direction of 0°, 45° and 90° with respect to rolling direction. To determine the effect of percentage elongation, the specimens were tested in tension by giving 15%, 20%, 30% and 35% of plastic strain much before fracture occurs.
Results: Experimental results showed that as the plastic strain increased from 15% to a maximum of 35% during tension test, the average plastic strain ratio increased from 0.988 to 1.122 respectively, and the same trend is seen in the values of planar anisotropy which varies between a minimum of 0.025 and maximum of 0.149. The equivalent plastic strain during deep drawing can be as high as 40%; therefore anisotropic behavior at 35% of plastic strain is more accurate and significant to be used in simulations.
Conclusion: The experimental studies showed increase in plastic strain ratio on increase in the percentage elongation.