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For certain continuum problems, it is desirable and beneficial to combine two different methods together in order to exploit their advantages while evading their disadvantages. In this paper, a bridging transition algorithm is developed for the combination of the meshfree method (MM) with the finite element method (FEM). In this coupled method, the MM is used in the sub-domain where the MM is required to obtain high accuracy, and the FEM is employed in other sub-domains where FEM is required to improve the computational efficiency. The MM domain and the FEM domain are connected by a transition (bridging) region. A modified variational formulation and the Lagrange multiplier method are used to ensure the compatibility of displacements and their gradients. To improve the computational efficiency and reduce the meshing cost in the transition region, regularly distributed transition particles, which are independent of either the meshfree nodes or the FE nodes, can be inserted into the transition region. The newly developed coupled method is applied to the stress analysis of 2D solids and structures in order to investigate its’ performance and study parameters. Numerical results show that the present coupled method is convergent, accurate and stable. The coupled method has a promising potential for practical applications, because it can take advantages of both the MM and FEM when overcome their shortcomings. [ABSTRACT FROM AUTHOR]

A new method named as Statistical Average Algorithm is developed for solving the structural dynamic compound inverse problem, which means to identify structural parameters with unknown input or to inverse input time history with unknown structural parameters. By taking the mechanical characteristic of the ground motion as an additional condition, an iterative algorithm based on the least-squares technique is developed so that the input process and structural parameters can be correctly determined using only output measurements. The procedure of the proposed method is discussed in detail, and a mathematical proof is presented as well in the appendix. A practical input situation such as earthquake, ambient vibration is considered in the numerical examples to verify the accuracy, reliability and robustness of the proposed algorithm. Considering the background of the practical application, both of the noise-free and noise-included output responses are considered in the numerical examples. In all cases, the proposed method identifies the structural parameters and reconstructs the input process rationally. [ABSTRACT FROM AUTHOR]

Deformation behavior of soft-matrix two-phase alloys has been computed using a continuum mechanics model based on an Isostrain condition, while the stress is distributed by the rule of mixtures. A genetic algorithm (GA) was used to optimize the mechanical modeling parameters such as the resistance and the formability of each phase. The stress–strain curves have been calculated as a function of volume fraction and mechanical properties of phases. The calculated and experimental stress–strain curves are compared and good agreement is found. The resistances increases with the rise of the hard phase volume fraction; this is more important with the presence of the hard phase than with the soft one. A linear law of variation of the phase resistance allows to interpolate and extrapolate the model, a good agreement is found with the evolution of the mechanical behavior. [ABSTRACT FROM AUTHOR]

A parallel implementation for the finite volume method (FVM) for three-dimensional (3D) viscoelastic flows is developed on a distributed computing environment through Parallel Virtual Machine (PVM). The numerical procedure is based on the SIMPLEST algorithm using a staggered FVM discretization in Cartesian coordinates. The final discretized algebraic equations are solved with the TDMA method. The parallelisation of the program is implemented by a domain decomposition strategy, with a master/slave style programming paradigm, and a message passing through PVM. A load balancing strategy is proposed to reduce the communications between processors. The three-dimensional viscoelastic flow in a rectangular duct is computed with this program. The modified Phan-Thien–Tanner (MPTT) constitutive model is employed for the equation system closure. Computing results are validated on the secondary flow problem due to non-zero second normal stress difference N2. Three sets of meshes are used, and the effect of domain decomposition strategies on the performance is discussed. It is found that parallel efficiency is strongly dependent on the grid size and the number of processors for a given block number. The convergence rate as well as the total efficiency of domain decomposition depends upon the flow problem and the boundary conditions. The parallel efficiency increases with increasing problem size for given block number. Comparing to two-dimensional flow problems, 3D parallelized algorithm has a lower efficiency owing to largely overlapped block interfaces, but the parallel algorithm is indeed a powerful means for large scale flow simulations. [ABSTRACT FROM AUTHOR]

A three-dimensional dynamic program for the anaysis of large deformations in contact-penetration problems is developed using the finite element Lagrangian method with explicit time integration. By incorporating a tetrahedral element, which allows a single-point integration without a special hourglass control scheme, this program can be more effective to the present problem. The position code algorithm is used to search contact surface. Eroding surfaces are also considered. The defense node algorithm was slightly modified for the calculation of contact forces. A study of obliquity effects on metallic plate perforation and ricochet processes in thin plates impacted by a sphere was conducted. It is well simulated that on separation of two parts of the sphere, the portion still within the crater tends to perforate, while the portion in contact with the plate surface ricochets. This deformation pattern is observed in experiments, especially at high obliquities. A long rod that impacts an oblique steel plate at high impact velocity was also simulated in order to study the dynamics of the rod caused by the three dimensional asymmetric contact. The agreement between simulated and experimental results is quite good. Fracture phenomena occuring at high obliquity deserves further investigations. [ABSTRACT FROM AUTHOR]