Papers by Keyword: Computational Mechanics

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Authors: Sebastian Stanislawek, Andrzej Morka, Tadeusz Niezgoda
Abstract: The paper presents a numerical study of a double layer composite panels impacted by a AP (Armor Piercing) 51WC projectile. The standard panel is built with aluminum and Al2O3 ceramic continuum layers while the studied model consists of the same aluminum plate but the front one is built with a set of hexagonal ceramic bars. The bar width and the impact position influence on the ballistic resistance are analyzed and compared with the reference solution. The problem has been solved with the usage of the modeling and simulation methods as well as finite elements method implemented in LS-DYNA software. Space discretization for each option was built by three dimension elements guarantying satisfying accuracy of the calculations. For material behavior simulation specific models including the influence of the strain rate and temperature changes were considered. Projectile Tungsten Curbide and aluminum plate material were described by Johnson-Cook model and ceramic target by Johnson-Holmquist model. In the studied panels the area surrounding back edges was supported by a rigid wall. The obtained results show interesting properties of the examined structures considering their ballistic resistance. All tests has given clear results about ballistic protection panel response under WC projectile impact. Panels consisting of sets of hexagonal ceramic bars are slightly easier to penetrate, reference model is stronger by 19% for smaller bars and by only 7% for bigger rods. Despite this fact, the ceramic layer is much less susceptible to overall destruction what makes it more applicable for the armor usage. Furthermore, little influence of the projectile impact point and consequently a part of the bar which is first destroyed is proved.
Authors: Hong Chang Qu, Bei Yi Zhang, Feng Zhang
Abstract: Based on the natural element method (NEM), which is a kind of meshless method, a two-dimensional numerical simulation method is developed and applied to the analysis of overall elastic moduli and fracture of solids. The calculated results are compared with the experimental solutions for overall elastic moduli, fracture and stress-strain curves for two, three and four graded concrete with FEM solutions in plane. The numerical results show the presented method is easy to implement and very accurate, especially for solving the problems of crack propagation.
Authors: Yue Ping Qin, Quan Sun, Xiao Bin Yang, Guo Yu Zhang
Abstract: In order to compare precisions of different finite volume schemes for plane stress problems, this paper discussed three typical finite volume schemes(FVM2, FVM3 and FVM4) through theoretical deduction and example verification, and introduced a new scheme(FVM1). Force equilibrium equations were obtained, which derived from the principle of the finite volume method (FVM). Using triangular units and in view of internal cells and boundary elements, this paper put forward these four finite schemes linear equations similar to the finite element method(FEM) stiffness equations but with different coefficients. The analyses and numerical example results show that FVM1 is the optimal finite volume scheme, and suggest that in practical civil, architectural and hydraulic engineering calculations, schemes should be selected carefully and FVM1 is a good option.
Authors: Tomotsugu Shimokawa, Toshiyasu Kinari, Sukenori Shintaku
Abstract: The relationship between grain subdivision mechanisms of a crystalline metal and the strain gradient under severe plastic deformation is studied by using molecular dynamics simulations in quasi two dimensions. Two problems are simulated for single crystal models: (a) uniaxial tensile and compressive deformation and (b) localized shear deformation. In the case of uniaxial deformation, a large number of dislocation pairs with opposite Burgers vectors are generated under deformation, but most dislocations are vanished due to pair annihilation under relaxation. Therefore, no dislocation boundary can be formed. On the other hand, in case of localized shear deformation with large strain gradient, dislocation boundaries are formed between undeformed and deformed regions. These dislocations can be regarded as geometrically necessary dislocations. Consequently, the importance of the strain gradient to make grain boundaries under plastic deformation can be confirmed by atomic simulations.
Authors: I.A. Jones, A.A. Becker, A.T. Glover, P. Wang, S.D. Benford, Michael Vloeberghs, C.M. Greenhalgh
Abstract: Boundary element (BE) analysis is well known as a tool for assessing the stiffness and strength of engineering components, but, along with finite element (FE) techniques, it is also finding new applications as a means of simulating the behaviour of deformable objects within virtual reality simulations since it exploits precisely the same kind of surface-only definition used for visual rendering of three-dimensional solid objects. This paper briefly reviews existing applications of BE and FE within virtual reality, and describes recent work on the BE-based simulation of aspects of surgical operations on the brain, making use of commercial hand-held force-feedback interfaces (haptic devices) to measure the positions of the virtual surgical tools and provide tactile feedback to the user. The paper presents an overview of the project then concentrates on recent developments, including the incorporation of simulated tumours in the virtual brain.
Authors: S. Schmauder, U. Weber, E. Soppa
Authors: Yoshihiro Tomita, Shinya Nakata, Masato Naito, Kisaragi Yashiro
Abstract: To clarify the essential deformation characteristics of silica-filled rubber, we construct the finite element homogenization models of silica-filled rubber with newly proposed nonaffine molecular chain network model of rubber. These models can reflect the generation of complicated inter-fillers connecting phases where the characteristics of rubber are intricately changed depending on the volume fraction of silica coupling agent and relative size of particles and their location. The results obtained clarified the essential physical enhancement mechanisms of deformation resistance and hysteresis loss for rubber filled with silica with different distribution patterns under diffrent rate of deformation. The volume fraction of coupling agent essentially affects the deformation behavior of silica filled rubber which suggests the high controlability of the material characteristics of silica filled rubber as compared with carbon black filled rubber.
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