Papers by Author: Zhuo Zhuang

Abstract: In this article we presented a method of Fluid-Solid coupled simulation via FLUNET and ABAQUS in problems such as Aero/Hydro-Elasticity problems. UDF (user define function) script file in the Fluent software was utilized as the ‘Connecting File’ between FLUENT and ABAQUS for Aero-Elastic computations. Firstly, the fluid field was computed by Navier-Stokes Equation and the structure movement was directly integrated by the dynamics Equation, respectively. Then, the ‘Connecting File’ exchanged the computed data through the fluid and structure’s interface. The next analysis step continued. Analysis of the computed results showed that this coupling method designed for aero-elastic system was feasible and can be also used for other Fluid-Structure Coupling problems.

Abstract: Molecular Dynamics (MD) simulations of indentation and scratch over crystal nickel (100) were carried out to investigate the microstructure evolution at nanoscale. The dislocation nucleation and propagation during process were observed preferably between close-packed planes. Dislocation loops are formed under both indentation and scratch process, and indentation and friction energy were transferred to the substrate in the form of phonon of disordered atoms, then part of the energy dissipated and rest is remain in the form of permanent plastic deformation.

Abstract: With the development of material science, especially as MEMS/NEMS are playing a more and more important role in modern engineering, some mechanical behaviors of materials, e.g., fracture, shear instability, need to be investigated from multidisciplinary perspective. The molecular dynamics (MD) simulations are performed on single-crystal copper block under simple shear to investigate the size and strain rate effects on the mechanical responses of face-centered cubic (fcc) metals. It is shown that the yield stress decreases with the specimen size and increases with the strain rate. Based on the theory of dislocation nucleation, a modified power law is proposed to predict the scaling behavior of fcc metals. In the MD simulations with different strain rates, a critical strain rate exists for each single-crystal copper block of given size, below which the yield stress is nearly insensitive to the strain rate. A hyper-surface is therefore formulated to describe the combined size and strain rate effects on the plastic yield stress of fcc metals.

Abstract: The school of aerospace of Tsinghua University has started a project to develop new kind of stratospheric balloons for earth observation. These balloons will be designed to stand in the same position during a few days at 20 kilometers of altitude. To reach this goal, the first step is to select adapted materials for the balloon envelope. The materials for stratospheric balloons application should have specific properties adapted to the environment such as mechanical, thermo-optical, and permeability properties. Thus, we have asked a material manufacture company to develop and manufacture a material adapted to our application. In this paper, we will present the first results concerning the mechanical properties of the material. Experimental facilities have been developed to test the mechanical behavior of the materials at room and low temperature. The future development of the project will be to identify behavior law adapted to our material that fits with the experimental results.

Abstract: As one kind of the most important cells in human body, myocardial cell becomes the focus of attention, not only the biologist but also the researchers of mechanics. A new viscoelastic constitutive model of the living myocardial cell is developed based on the micropipette suction experiment in which the surface of the cell is aspirated into a small glass tube while tracking the leading edge of its surface. Some numerical simulations are presented by finite element to model the whole process of micropipette suction of the myocardial cell. Meanwhile, a model cell with both mechanical behavior and physiological function is being developed, to prove the viscoelastic constitutive model and to predict more results of myocardial cell under different physiology conditions.

Abstract: A crack propagation perpendicular to gradient in a large scale functionally gradient materials, which has (1) a linear variation of Young’s modulus with a constant mass density and Poisson’s ratio, and (2) a exponential variation of Young’s modulus with a constant mass density and Poisson’s ratio, is modelled by finite element methods. Based on the experimental result of large scale functionally gradient materials, the dynamic propagation process of the FGMs is modelled and the dynamic parameters, like the energy release rate and crack tip opening angle, are calculated through a generation phase.

Abstract: The hyperelastic constitutive model of cardiac muscle is developed based on the animal surgical operation and mechanical experiments from the heart of the dogs, and the relaxation phenomena is also studied based on the Hill three elements model which is viscoelastic. Some numerical simulations are presented by finite element for the cardiac pacing/defibrillation lead interaction with muscles of the heart.

Abstract: The response analysis of reinforced concrete (RC) structures subjected to strong earthquake motions require realistic conceptual models. The special models, such as Clough and Takeda, which describe the non-linear section characteristic of reinforced concrete beam and column. In the earthquake motions, the deforming is sensitive to the response of structures intensively. The traditional lumped plastic model inevitably induces inaccuracy. Hence, meshing the members or distributing stiffness along the whole member is employed to simulate the seismic response of the structures. In this paper, Takeda elastic-plastic beam element model has been developed, which is based on general FEM code ABAQUS in order to simulate the response of RC. The influence is discussed due to the different lengths of plastic zone and element sizes.

Abstract: Preventing pipeline from rapid crack propagation is a critical issue to avoid casualties and disasters. In this paper, by combining the energy balance theory with FEM simulation and arrest criteria, the numerical analysis is developed to solve the problem of crack dynamic propagation in gas pipeline. This simulation, in combination with the full-scale blast tests, provides a broad prediction of the dynamic fracture process. The crack tip opening angle (CTOA) criterion is consummated through the comparison between CTOA in FEM calculation and the critical value of (CTOA)C obtained by the experiment. The result of the simulation for the crack speed and location is consistent with data by Alliance and Japanese full-scale blast tests.

Abstract: A numerical algorithm using equal-order linear finite element and fractional two-step method is presented in this paper, which is used for analysis of incompressible viscous fluid flow with free surface problems. In order to avoid severe mesh distortions, ALE method is used for dealing with the free surface sloshing. For numerical integration, the fractional step method is employed, which is useful because the same linear interpolation functions for both velocity and pressure could be carried out in the finite element formulation. The present algorithm has been applied to some examples and proved to be accurate and more efficient.