Papers by Author: Yi Bo Xiong

Abstract: The explicit dynamic code LS-DYNA3D is used to simulate limited-thickness concrete slabs penetrated and perforated by steel projectiles with velocities from 381 m/s to 1058 m/s. The concrete slab is modeled with Smooth Particle Hydrodynamics (SPH) elements near the trajectory while Finite Element Method (FEM) elements in the others of the target, which is called FE-SPH method. The elastic-plastic model and Johnson-Holmquist concrete model are used to describe the mechanical behaviors of the projectiles and target slabs, respectively. The residual velocities computed by both FEM and FE-SPH method agree well with those of experimental results. For brittle concrete, the penetration and perforation phenomenon modeled by FE-SPH are in closer agreement with the experimental results than those modeled by FEM. Simulation of penetration and perforation by FEM require artificial element erosion set, which would lead to distortion of modeled results.

Abstract: In order to calculate the combined deformations of an Euler-Bernoulli cantilever beam subjected to bending moment, twisting moment, transverse load and axial load, particle flow code in 3 dimensions (PFC3D) is used with parallel bonds model. The computed deformations, including transverse deflections, rotations about axis, maximum normal and shear stresses, were compared with the analytical beam-theory solution in terms of axial tension, axial compression and none axial load, respectively. Between computed results and analytical beam-theory solution, the error bands are greater than 99.7% at the beam tip, while the error of the transverse deflection of the whole beam is less than 0.6%. So, the PFC3D is able to precisely simulate the combined deformation of cantilever beam, and this work has special reference to engineering calculations and designs when PFC is applied to model the mechanical behaviors of continuum materials.

Abstract: In order to systematically study on dynamic mechanics character of granite, impact compression experiments and impact flattened Brazilian disc specimens of granite have been investigated with modified split Hopkinson pressure bar (SHPB) experimental facility, curve about stress versus strain and other parameter at strain rates of 23.9/s～108.4/s were obtained from impact compression. The dynamic tensile strength and critical tensile failure strain at strain rates of 2.3/s～25.6/s were obtained from impact flattened Brazilian. The experimental result show that dynamic compression strength , elastic modulus and failure strain，dynamic tensile strength significantly increase comparing to quasi-static experiment, and the above mechanics parameter include dynamic strength etc will increase with strain rate increasing, granite have the character of impact harding and ductility enhancement. The failure degree of failure will increase with increasing strain rate under impact compression; the failure configurations of the specimens present an center splitting mode under impact flattened Brazilian experiments. Whether impact compression or impact splitting under strain rate including this paper ’s experiments, the relationship between the DIFC or DIFT and the logarithm of strain rate is linear.

Abstract: In order to systematically study dynamic mechanics character of reactive powder concrete (RPC), impact compression experiments and impact flattened Brazilian disc specimens of RPC have been investigated with modified split Hopkinson pressure bar (SHPB) experimental facility using brass pulse shaper, curves about stress versus strain and other parameters at strain rates of 20.3/s~137.0/s were obtained from impact compression. The dynamic tensile strength and tensile failure strain at strain rates of 3.4/s~26.2/s were obtained from impact flattened Brazilian. For comparison, the quasi-static compress and split tension of RPC were obtained with an MTS 810 materials test system and CSS-88500 electron universal material testing machine.The experimental result show that dynamic compression strength , elastic modulus and failure strain,dynamic tensile strength and failure strain significantly increase comparing to quasi-static experiment, RPC have the character of impact harding and ductility enhancement. RPC exhibit excellent failure patterns at high strain rate. Whether impact compression or impact splitting under strain rate including this paper ’s experiments, the relationship between the DIFC or DIFT and the logarithm of strain rateis linear.

Abstract: Based on an extensive experimental program under uniaxial and triaxial compression, this paper studies the mechanical behavior of two types of concrete with the same raw materials and the same curing conditions of the construction site. Stress-strain relations and strengths are obtained under triaxial compression with confining pressures from 10MPa to 120MPa. Material constants of different types of failure criterion are determined by the statistical method with the data from this study and public literature, including linear Mohr-Coulomb model, parabolic Willam-Warnke failure criterion and power functional Johnson-Holmquist model. The results indicate that the modulus of both types of concrete decrease as an exponential decay law with the increase of confining pressures in triaxial compression.