Constitutive Model Of Rigid Polyurethane Foam Based On Data Mining

In car-pedestrian accidents,filling materials such as rigid polyurethane foam are widely used in vehicle safety devices in order to protect passengers inside vehicle and pedestrians hit.Rigid polyurethane foam is a porous structure material.It has the advantages of low density,high strength,easy shaping and good energy absorption ability.It can protect the impacted area by dispersing and absorbing impact force.Constitutive models established by traditional methods have many limitations.By combining tensor factorization and genetic algorithm,a data mining based method is proposed.The main contents includes:(1)In order to establish the constitutive model,establish high order tensor based on test data firstly.Tensor factorization is adopted to reduce the dimension of high order tensor.Use polynomial regression to fit the low-dimensional factor vectors calculated by tensor factorization and the the constitutive model is established.(2)In order to calculate the key parameters of constitutive model,a mixed integer optimization function is designed.The rank of tensor factorization and the polynomial regression fitting order of each dimension are taken as optimization parameters.The quadratic loss based on predicted data and test data is taken as the loss function.The penalty function based on regularization principle is taken as the penalty term to restrain over-fitting.Other parameters in the constitutive model can be calculated from key parameters.Based on priori knowledge and test data,constrained boundary conditions of each optimization parameter are determined.Using genetic algorithm to solve the mixed integer optimization problem.Other parameters can be calculated based on optimization results.Constitutive model is established.(3)Adopt the method above to establish constitutive model of rigid polyurethane foam under axial compression.According to the standard test method prescribed by ASTM,an experimental program was designed.Axial compression of rigid polyurethane foam specimens of 3 different densities was carried out under 3 different loading rates,and 9 sets of test data curves were obtained.Preprocess the test data and establish high order tensor.Use the method above to establish constitutive model of rigid polyurethane foam under axial compression.Validate the validity of the model.