Determining the Parameters of a Multilinear Material Model and Modeling the Plastic Deformation of Beam Structures of Machines

Abstract

The paper is devoted to the definition of the parameters of the multilinear model of elasto-plastic deformation of metals used in calculating the stress-strain state and predicting the destruction of mechanical-engineering structures. The proposed method for identifying the parameters of a multilinear metal model involves a transition from the conditional (engineering) values of stresses and deformations to the true values. A distinctive feature of the technique is the consideration of the stress-strain state in the neck of the sample and the recommendations for determining the intermediate parameters of the material model. For the purpose of approbation of the developed technique in the software complex ANSYS LS-DYNA, a computer simulation of flat tensile tests was carried out. In the calculation, the identified parameters of the model for steel 20 were used. The simulation error, calculated from the value of the relative elongation of the sample at the time of failure, was 1,8 %. The obtained parameters of the model were also used in modeling the three-point bending of beams of rectangular section 60×40×3 mm from steel 20. Comparison of the calculation results with experimental data showed a difference in the control values of bending forces up to 17 %. This difference is caused by hardening of the material at the corners of the cross-section of the beams. A method is proposed for taking this effect into account on the basis of recalculation of the inertial characteristics of the cross section. This made it possible to reduce the difference in the calculated results from the experimental up to 1,1 %.

Keywords

• computer simulation
• material model
• identification
• mechanical characteristics
• test
• finite element method
• ls-dyna