| The mechanical properties of explosion puffing products of fruit and vegetable are mainly determined by their pore structure,therefore,it is vital to study the relationship between its structure and mechanical properties,which is of great significance to carry out the quality control of fruit and vegetable press urepuffed products.As a result of fruit and vegetable explosion puffing products were porous mesh structure,and the large size,shape,structure and distribution of the hole.Only the partial results can be tested and it is difficult to form systematic.Theconclusion of the experience,the mechanical properties of fruit and vegetable explosion puffing products can be studied by single experiment method.Based on this,in this paper,the finite element numerical simulation,classical mechanical model prediction andexperimental verification of the combination of research methods.the establishment of fruit and vegetable pressure puffing pile structure of the geometric model,mechanical properties of mathematical model,the mechanical behavior of the brittle products in the static compression process was studied to obtain the change of the relative modulus and the mechanical deformation of the microcrystals under different relative densities.The main research contents and progress are as follows:(1)The closed-cell and open-cell model and multi-cellular model of spherical cavities,hexahedron cavities,rhombic dodecahedron cavities and tetrahedral tetrahedron cavities were established and established with the structural characteristics of the extruded crispy products.Mathematical model of static compressive mechanical properties of fragile products.(2)The numerical simulation of the mechanical properties of the cells with different cavities is carried out.The results show that the main deformation mechanism in the compression process of the closed-cell model is the bending deformation of the hole wall,and the open-cell model is the yield deformation at the interface of the hole and the hole.The maximum error between the relative modulus value and the theoretical value of the spherical cavity,hexagonal cavity,rhombic dodecahedron and tetrahedral tetrahedron hole were 0.1,0.04,0.041,0.01,respectively,in the relative density range of study.The relationship between the relative modulus and the relative density of the four models is E*/Es =0.720(?*/?s)2+0.023(?*/?s)+0.352;E*/Es = 1.382(?*/?s)2?0.286(?*/?s)-0.002;E*/Es= 0.641(?*/?s)2+0.468(?*/?s)-0.012;E*/Es=0.651(?*/?s)2 +0.312(?*/?s)+ 0.003.The fitting formulas of spherical cavities,rhombic dodecahedron cavities and tetrahedral tetrahedron cavities are relatively close to each other and are in agreement with Gibson-Ashby's empirical formula(formula as 3.5).The fitting formula between the brittleness compressive strength and the relative density of the three is consistent with the Gibson-Ashby empirical formula(formula as 3.7).The maximum errors of the relative modulus simulation values and Gibson-Ashby theoretical values for the four open cell models were 0.083,0.024,0.0324,0.0054.The relationship between the relative modulus and the relative density is E*/Es?1.025(?*/?s)1.554;E*/Es?0.324(?*/?s)1.011;E*/Es?2.103(?*/?s)2.070;E*/Es=0.484(?*/?s)1.523.Brittleness compressive strength and relative density,the spherical cavities model and the tetrahedral model fit the equation to be closer to the Gibson-Ashby theoretical value(formula as 3.4)empirical formula.Based on the relative modulus fitting formula,spherical porosity and four-tetrahedral pore opening model are in good agreement with Gibson-Ashby theoretical model.(3)Based on the results of the unit cell model,the spherical porosity,rhombic dodecahedral cavities and the tetrahedron pore closed cell multidimensional model with relative density of 0.375,0.05,0.06 were established,and the relative density was 0.1,0.05 and 0.01.Spherical cavities,rhombic dodecahedron cavities and fourteen tetrahedral cavities,the effects of cell multiplier on the relative modulus of the model were studied.In the simulation process,the cell bodies were selected as 2,3 and 4,respectively.The number of somatic cells was 9,35,91.The results showed that the relative modulus of each model was smaller with the increase of the number of model cells,and the relative modulus of the monomeric and diploid was more obvious.Therefore,the diploid model was selected to further study the mechanics of the multi-cell model performance.(4)The numerical simulation of the mechanical properties of spherical cavities,rhombic dodecahedron cavities and tetrahedral tetrahedron cavities was carried out.The results show that the deformation mechanism of the three kinds of open-and-closed-hole model is similar to that of the same-hole model.However,there is a connection between the wall surface of the hole and the hole and hole in the polyploid model,and the static compression haplotypes work together to show the mechanical properties.The relationship between the relative modulus and the relative density of the three diploid closed-cell models is E*/Es = 0.672(?*/?s)2 +0.082(?*/?s)+0.143;E*/Es=1.878(?*/?s)2+0.424(?*/?s)-0.015;E*/Es ?1.836(?*/?s)2+0.128(?*/?s)+0.012,which showed that the fitting formula of the rhombic dodecahedral cavities and the tetrahedron cavities is very close to the Gibson-Ashby empirical formula(formula as 3.5).The maximum error of the relative modulus simulation values and theoretical values of the three closed-hole diploids in the simulated results were 0.125,0.08 and 0.09,respectively.The fitting formula of the diamond-shaped dodecahedral cavities and the tetrahedral porosity model is very close to the formula of the brittle compressive strength and the relative density.It is consistent with the empirical formula of Gibson-Ashby(formula as 3.7).It can be seen that the diamond dihedral and tetrahedral diploid cavities are in good agreement with the theoretical model.The relationship between the relative modulus and the relative density of the three polyploid open model is E*/Es=2.7772(?*/?s,)2.101;E*/Es =3.617(?*/?s)2.310;E*/Es = 1.597(?*/?s)1.860.The fitting formula of brittleness compressive strength and relative density is ?*/?c=0.413(?*/?s)2.094;?*/?s=0.156 {?/?s)1.259;?*/?s=0.521(?*/?s)1.194.It can be seen that the relative modulus of the three models is similar to the fitting formula of the relative density,and the results are compared with the Gibson-Ashby theoretical empirical formula(formula as 3.2).The results showed that the diamond dihedral inclusions more consistent.The same result can be obtained by fitting the formula of brittleness compressive strength and relative density and the theoretical empirical formula(formula as 3.4).Therefore,it can be seen that the diploid model of rhombic dodecahedral porosity and tetrahedron pore opening theoretical model is more consistent.(5)Experimental Verific atio nThe stress and strain curves obtained from the simulation results and the experimental values of the diamonds and the tetrahedron cavities were compared.Both of which exhibit the elastic structure of the porous structure and the elastoplastic stage.The experimental results showed that the experimental area is significantly higher than the simulated value.The experimental results showed the basic characteristics of fragmentation of fruit and vegetable crisp in the platform area,while the simulated value platform area is relatively gentle and shows the basic characteristics of plasticity of porous structure.From the trend of the whole trend of stress and strain curve,the simulation value is similar to the experimental result,and the numerical value is not very different.Therefore,the simulation value can reflect the experimental results in a certain sense,and the rationality of the numerical simulation results is explained. |
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