A Peridynamic Model for Analyzing Fracture Behavior of Functionally Graded Materials Used as an Interlayer

Functionally graded materials(FGMs)can be used els an interlayer.The interlayer connects two homogeneous materials and slows mutations in material properties,owing to the variability of parameters and microstructure.In this numerical simulation,a bond-based peridynamic(PD)model was used to perform dynamic fracture analysis of a continuous beam and a sandwiched structure with an FGM interlayer.Some simulation results of two convergence studies,which include grid refinement(m-convergence)and the reducing radius of PD horizon(^-convergence),were discussed.Under a four-point bending load,the propagation behaviors of single pre-crack in the continuous beam with the FGM interlayer at different locations are simulated to compare with the experimental results.For the sandwiched structure,the problems of a single crack and double cracks were considered.The numerical results show that the crack can deflect toward areas where the energy release rate is low.Additionally,the crack on the weak side for symmetric cracks only has fracture behavior,and if the double cracks are asymmetrical,all these cracks have fracture behaviors and propagation of the initial crack in the stiff region has a higher sensitivity than in the compliant region.

Misalignment Tolerance in One-side and Symmetric Loading Hopkinson Pressure Bar Experiments

The split-Hopkinson pressure bar(SHPB)is a widely used experimental technique for studying the mechanical properties of materials at high strain rates.There are two kinds of loading methods applied in the SHPB technique,namely one-side loading and symmetric loading.However,the experimental accuracy of the two loading methods is affected by the interface contact.The present study focused on the inadequate contact caused by the misalignment of the pressure bars.The commercial software ABAQUS was used for simulations.The result shows that the inadequate contact caused by the alignment of the bars has a non-negligible effect on the calculated results.Compared with the one-side loading Hopkinson pressure bar,the symmetric loading Hopkinson pressure bar has a more relaxed requirement for the alignment of the bars.The conclusion arrived at in this paper can help researchers to make a reasonable choice between one-side and symmetric loading Hopkinson pressure bars according to actual requirements.