Study On Mechanical Properties Of Typical Refrigerator Materials And Resistance To Drop Shock

Polymer foam material is widely used as packaging buffer material in home appliance industry because of its good characteristics of buffering,energy absorption and vibration reduction.The expandable polystyrene(EPS)and expandable polyurethane(EPU)foam materials are the representatives with mature production technology and low cost,which have become the preferred materials for researchers to design and develop packaging structures.In fact,the research on the protection ability of buffer packaging structure to products is to study the structural dynamic response of packaging under dangerous load environment,especially the characteristic response of packaging under drop impact load.Taking the falling impact of the refrigerator as an example,this paper takes the foam packaging materials and typical materials used in the structure of the refrigerator as the research object,and discusses the mechanical properties of the materials by means of experiment,theory and calculation.Finally,the finite element model of the refrigerator package is established and the numerical calculation provides a reference for the design of packaging engineering structureThe effects of foam density and loading rate on the dynamic compression characteristics of EPS and EPU foam were investigated by using universal material testing machine and drop hammer impact test device.Based on the experimental data,considering the density correlation,the empirical formula for obtaining the dynamic constitutive relation of materials under constant strain rate is fitted,which overcomes the problem that it is difficult to obtain the constitutive relation of materials under constant medium strain rate by drop hammer test method,and establishes the compression dynamic constitutive model of EPS and EPU under medium and low strain rate.Based on the four material models of MAT57 and MAT163 in ls-dyna,and Low Density Foam and Crushable Foam in ABAQUS,the analysis models of EPS and EPU Foam are established respectively.By simulating the falling hammer impact process and comparing the test results,it is found that MAT 163 and Crushable Foam have higher accuracy in predicting the impact response and energy absorption characteristics of EPS foam material,while Low density Foam could better predict the EPU foam material.The reliability of the dynamic constitutive model is verifiedThe tensile mechanical properties of plastic materials(HIPS,ABS,GPPS,PP)and metal materials(DX5 ID,SPCC)used in refrigerator structure under medium and low strain rate are studied by means of universal material testing machine and hydraulic high speed drawing machine.The effects of temperature and loading rate on mechanical properties of materials are discussed.The effective data of mechanical behavior related to strain rate and temperature is obtained,and the rate effect and plasticity parameters are introduced into the constitutive equation for the drop calculation of refrigerator structureAt last,the drop impact of refrigerator package is simulated.The results show that the foam packaging can significantly reduce the impact force on the structure of the refrigerator,extend the impact time,and enhance the buffering and damping effect.Bottom drop is more harmful to the structure of refrigerator than edge drop and angle drop.The stress distribution of the structure is positively correlated with the impact force.With the increase of the density of the foam packing material used,the impact force on the structure is greater When high density foam is used,plastic deformation occurs locally.In view of the structural design defects,this paper improves the stress concentration through local optimization,reduces the inertial effect of the structure,and improves the anti-dropping impact ability of the refrigerator.