查看更多>>摘要：In this study,the penetration resistance of a polyurethane elastomer(PUE)/honeycomb aluminum composite structure was investigated.A finite element analysis model was constructed to predict the residual velocity of the projectile after penetrating the PUE/honeycomb aluminum composite structure,and the accuracy of the model was verified through experiments.Both the residual velocity of the projectile and the failure appearance of the target plate were accurately predicted by the model.In addition,the Cowper-Symonds model was used to describe the material properties of the PUE layer,effectively simulating the damage appearance of the PUE layer after penetration.Subsequently,based on the validated model,three different configura-tions of the PUE/honeycomb aluminum composite structure were designed on the basis of the original honeycomb aluminum composite structure with a polyurethane elastomer coating,maintaining constant mass of the composite structure,and the ballistic performance was predicted using the finite element model.The anti-penetration performance of the PUE/honeycomb aluminum composite structure was analyzed by examining the velocity changes of the projectile,the energy changes of each component,and the crushing of the honeycomb core layer.Finally,the influence of different projectile shapes on the ultimate ballistic performance of the structure was studied,and the reasons for the influence of warhead shape on the appearance of target plate failure were analyzed.
查看更多>>摘要：This paper proposes a novel numerical solution approach for the kinematic shakedown analysis of strain-hardening thin plates using the C1 nodal natural element method(C1 nodal NEM).Based on Koiter's theorem and the von Mises and two-surface yield criteria,a nonlinear mathematical programming formulation is constructed for the kinematic shakedown analysis of strain-hardening thin plates,and the C1 nodal NEM is adopted for discretization.Additionally,Konig's theory is used to deal with time integration by treating the generalized plastic strain increment at each load vertex.A direct iterative method is developed to linearize and solve this formulation by modifying the relevant objective function and equality constraints at each iteration.Kinematic shakedown load factors are directly calculated in a monotonically converging manner.Numerical examples validate the accuracy and convergence of the developed method and illustrate the influences of limited and unlimited strain-hardening models on the kinematic shakedown load factors of thin square and circular plates.
查看更多>>摘要：The first principal stress plays a key role in ductile fracture processes.Investigation of the distribution and evolution of the first principal stress at the crack tip is essential for exploring elastoplastic fracture behaviors.A semi-analytical model was developed in this study to determine the maximal first principal stress at the mode Ⅰ crack tip with 3D constraints for materials following the Ramberg-Osgood law.The model,based on energy density equivalence and dimensional analysis,was validated through finite element analysis(FEA)of various materials and geometric dimensions of specimens with mode Ⅰ cracks,under over 100 different types of working conditions.The dimensionless curves of maximal first principal stress versus load,as predicted by the model,agreed well with the FEA results,demonstrating the accuracy and applicability of the model.This research can provide a basis for future theoretical predictions of crack initiation and propagation.
查看更多>>摘要：Polymers with particle inclusions have wide applications,and the mechanical properties of polymer composites affect their reliability in service.The strength of these composites is dependent on factors such as particle fraction,size,distribution,and interface interaction between the two phases,in addition to the properties of the polymers and particles.The size effect of particles and interface damage play an important role and thus draw considerable attention.In this paper,the size-and interface-dependent strength of polypropylene(PP)with nano/micro silica(SiO2)particles of different fractions is studied through a combination of tensile experiments on a series of samples and corresponding three-dimensional(3D)finite element modeling.The results indicate that PP with 2％SiO2 nanoparticles of 50 nm exhibits relatively higher tensile strength,shedding light on the microstructure mechanism where smaller particle sizes lead to better interface bonding.Furthermore,the particle size and interface coupling effect is analyzed based on the size-dependent elastic modulus model and the interface-cohesive model.The simulation demonstrates the local interface damage evolution around a particle of the composites in tension.These findings are beneficial for designing polymer composites with nanoparticle inclusions.
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