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Papers by Zhi-Qiang Feng

International Journal of Solids and Structures, Aug 1, 2010

Advances in Civil Engineering, 2018

The bipotential theory allows us to describe nonassociated material laws. In this paper, we propo... more The bipotential theory allows us to describe nonassociated material laws. In this paper, we propose its application to the Drucker–Prager model. With a new description of the implicit flow rules, we propose dual constitutive cones as well as five forms of the bipotential function: the elastic stage in rate form, the plastic stage in rate form, the elastic stage in incremental form, the plastic stage in incremental form, and the elastoplastic stage in incremental form. By combining these with the finite element method, a numerical strategy that deals with the nonassociated Drucker–Prager model is obtained. Two examples are simulated to verify the accuracy, the stability, and the practicability of the algorithm in civil engineering.

This paper presents numerical simulations of 3D contact problems with orthotropic friction law an... more This paper presents numerical simulations of 3D contact problems with orthotropic friction law and nonassociated sliding rule. The solution algorithm is based on the bi-potential method applied to a non linear and non differentiable system of equations. Cyclic load are especially emphasized because the wear rate is strongly coupled to the friction dissipation. This first study seems to indicate a significant influence of the anisotropy of the friction on the wear. Mots-clefs : frottement orthotrope ; loi non associee ; usure 1 Un modele de frottement anisotrope avec loi de glissement non associee

L’integration d’une analyse ergonomique dans le processus de conception d’un produit est fondamen... more L’integration d’une analyse ergonomique dans le processus de conception d’un produit est fondamentale pour fournir des informations en termes d’usage, de confort et de securite. Un mannequin numerique comme MANERCOS peut aujourd’hui etre utilise dans ce contexte mais il ne represente que partiellement l’aspect biomecanique de l’activite humaine. Nous proposons donc de developper cet aspect en liaison avec MANERCOS en modelisant par elements finis le corps humain grâce au code de calcul FER.

Nonlinear Dynamics

This study aims to extend the application of the bi-potential method to solve the dynamics proble... more This study aims to extend the application of the bi-potential method to solve the dynamics problems of rigid bodies involving friction and multiple impacts. The key issue is the determination of the impact impulsion. The impact bi-potential function and the formula for calculating the bi-potential coefficient of rigid bodies are presented. The effects of the friction and normal restitutive coefficients on the results are analyzed. Extension from discrete granular systems to multibody systems is realized. Further, the internal software FER/Mech is used for realizing dynamic simulation of the entity object, and the comparison with the experimental video verifies the correctness of the proposed method. Results show that the achieved improvements of this study are more accurate. In the discrete granular systems, the numerical solutions of the proposed method are in good agreement with those of another numerical method. But in the multibody systems, the numerical solutions obtained by the proposed method are more stable. It is noteworthy that the bi-potential method not only does not increase the degree of freedom of the system, but also makes the programming simple and numerically robust, thus reducing the computing cost.

International Journal of Solids and Structures

International Journal of Solids and Structures, 2010

International Journal for Simulation and Multidisciplinary Design Optimization, 2008

Contact Mechanics, 1995

In many metal forming processes and other industrial applications such as joint problems, two or ... more In many metal forming processes and other industrial applications such as joint problems, two or more bodies come into contact with friction and they may undergo large deformation. In such processes nonlinearities arise in geometry, constitutive relation as well as variable contact and friction conditions. Since these nonlinearities make it hard to solve such problems, in particular the contact nonlinearities are non-smooth, a reliable and efficient solution algorithm is necessary. In the literature, large deformation contact problems with friction have almost exclusively been treated by penalty methods (Hallquist, 1983; ANSYS, 1993). Much information points to the fact that the penalty methods have some drawbacks concerning numerical stability and precision, in particular for friction simulation. By means of a theory called ISM (Implicit Standard Materials), De Saxce and Feng (1991) propose an augmented Lagrangian formulation in which, the unilateral contact and the friction are coupled. The frictional contact problem is treated by solving a reduced system. The aim of the present paper is to constitute a brief outline and an extension of previous research in large deformation context and to present some computational examples of nonlinear analysis of contact problems.