Identification Of The Material Constitutive Model Coefficients Based On Digital Imaging Correlation

Surface integrity is an important evaluation method for the quality of machining.The intermediate physical quantities such as stress,strain,and temperature in the metal machining directly affect surface integrity.Therefore,the constitutive equation describing the variation law of these physical quantities plays an important role in the research.In the past,methods for identifying constitutive equations coefficients,including standard material testing,the method based on simulation models or simulation methods,have various limitations.Based on in-situ high-resolution imaging and digital image correlation technology(DIC),as well as an analytical model for orthogonal cutting,this paper proposes a new hybrid analytical-experimental method to identify the coefficients of the material plastic constitutive model.This method is particularly suitable for identifying constitutive model coefficients at higher strain and strain rates than in conventional mechanical testing.The following results have been achieved:1.An experimental platform was set up to cut the specially pretreated nickel-aluminumbronze alloy sample using a carbide tool.Scatter plot is captured by a double-shutter camera to represent cutting process,as well as force signals measured by a dynamometer.2.Based on DIC method,velocity fields are computed from the scatter plot.The streamlines are obtained from the velocity field,and the strain rate fields are obtained from the gradient information.The strain rate is integrated along the streamline to obtain the stress field.The strain rate distribution and strain distribution in the primary shear zone and the tertiary shear zone are analyzed,which is in accordance with the cutting theory.3.The average temperature on the shear band is estimated from the strain and strain rate,and the stress distribution is obtained by the Johnson-Cook constitutive model with the preset constitutive parameters.Shear forces derived from stress integrations are matched to the measured ones,then the constitutive model coefficients can be determined by solving a sequential optimization problem.4.Strain distribution,strain rate distribution,temperature and force obtained by finite element simulations using the identified material constitutive model coefficients as input are well matched,are well matched with the ones from experiments.These comparisons verify the reliability of the method.