Papers by Author: Yong Chi Li

Abstract: This paper presents an interpolation-based method for multidimensional extrapolation. A series of interpolation formulations are proposed to extrapolate functions normal to the interface between two regions. Theoretical proofs and relevant analysis are also presented. The method developed maintains the characteristics of implicit interface. The interface inside every cell is treated smoothly by assuming that curvature is equal everywhere. The method developed and numerical results are verified by comparing to the results by PDE method and theoretical results. Numerical tests demonstrate that the method developed is first-order accuracy and also more efficient in numerical implementation and more accurate than PDE method.

Abstract: The velocity history of free-surface particle for carbon phenolic composites (density is 1.4g/cm³) is obtained based on the loading technology of the light gas gun, the relationship between the striking velocity of flyer and the spall thickness as well as time is investigated. Besides, spall strength and thickness are obtained by analyzing the samples data and curves. The high pressure physical characteristics, such as type Hugoniot curve and Murnagham state equation for this material, are acquired by analyzing the velocity history of free-surface and spall characteristics. This study provides a methodology to quantify spall and physical characteristics for carbon phenolic composites under tensile wave loading.

Abstract: An advanced structure containing cavities was adopted in distribution layers. A series of large-scale similarity-simulation tests was conducted on the defense effect of the four structures under plane impact loads. Based on the tests results and theoretical analysis conclusions, numerical simulations were developed by LS-DYNA software. The results indicate that the numerical results agree well with the test data; the stress peak was distinctively decayed below the cavities, and the defense effect of circle-section cavity is more effective than square-section cavity while the defense effect was weakened when a thin steel plate was laid above the cavities. Compared with clipping performance of it under the explosion loads of mass ammunition, which of the structure with cavities under plane impact loads is better effective. This work provides an important basis for designing the scientifically safe distribution layers.

Abstract: Ferromagnetic base composite material is widely used in aerospace field, and its high pressure mechanical properties become the study hot spot in recently years. Aimed at an advanced ferromagnetic base composite material, its impact compression behaviors were investigated by means of Light Gas Gun (LGG). The shock wave velocity (D) and the particle velocity (u) behind the shock wave were measured and calculated by using Asymmetry Impact and Direct Measurement. Based on the experimental results and calculated results, a D-u type Hugoniot curve was obtained. The Grüneisen equation of state for the ferromagnetic base composite material and its coefficients were obtained on the basis of its Hugoniot curve.

Abstract: Ferromagnetic base composite materials were applied widely in aircraft and space vehicles engineering. Aimed to an advanced ferromagnetic base composite material, a series of experiments for thermal physical properties of this material were conducted, and the corresponding performance curves were obtained through statistic analyzing. The experimental results showed good consistency. And then the thermal physical parameters such as thermal expansion coefficient, engineering specific heat and sublimation heat were solved and calculated. This investigation provides an important foundation for the further research on the heat resistance and thermodynamic performance of this material.

Abstract: The MTS810 and SHPB are used to experimentally study the quasi-static and dynamic mechanical properties of three-dimensional E-glass fiber-reinforced composite. Stress-strain curves along the plane and thickness direction are obtained under varying strain rates, ranging from 10-3 to 103s-1. Experimental results show that strain rate has a significant effect on the material response. It is found that the compressive strength and the modulus increase with increasing strain rate, the failure strain, however, decreases slightly. But, the effect of strain rate in-plane and through thickness directions is different. A higher strain rate sensitive modulus and failure is found in the thickness direction, while a higher strain rate sensitive failure strength is found in the in-plane direction.

Abstract: A damage evolution law for porous phenolic composites is developed by using phenomenological point, which along with the improved Johnson-Cook model is then implemented into a finite difference code for one-dimensional strain wave problem. The velocity history of free-face particle is recorded and correlated with the simulated result to evaluate the damage parameters. Good agreement shows that the proposed damage evolution law and spall rule are feasible. Besides, the relationships between the striking velocity of flyer and the spall thickness as well as spall time are investigated. This study provides a methodology to quantify the damage evolution of phenolic composites under impact loading.