International Journal of Modeling, Simulation, and Scientific Computing

This paper studies a resource discovery scheme for a Grid system comprised of virtual organizations (VOs). The proposed scheme suggests that routers and resources comprise VOs within a Grid system, where a router controls locally a number of resources. The router also maintains the connections of each VO with other VOs in the system. Each VO acquires only partial/limited knowledge of the availability of resources controlled by other VOs in the system. When a request for a specific resource is created in a VO of the system, the goal is to discover an appropriate resource for its satisfaction, and subsequently to effectively direct this request. The proposed resource discovery scheme takes into consideration the fact that VOs only acquire a limited knowledge of the system and manages to extend this knowledge without affecting negatively the satisfaction of requests. During the satisfaction of requests, the proposed resource discovery scheme supports and enhances the VOs of the system in order to gain better knowledge of the Grid resource availability. As the creation and satisfaction of requests progress, the VOs manage to acquire an adequate knowledge of the Grid resources, enhancing the overall system's well-function. Finally, this paper presents the performance evaluation of the resource discovery scheme by providing a number of simulation tests in Grid systems of different sizes.

Realistic force modeling of bone drilling is critical to haptic simulation systems for precise surgical training such as pedicle screw fixation in spine surgery. Existing method of force modeling applied metal machining theory to bone drilling directly. However, the mechanical property of bony material is different from continuous metal. In this paper, we present a novel force modeling method of bone drilling based on empirical formula and drilling experiment to provide a force model with high fidelity. A simplified empirical model of drilling in bony material is derived from the empirical formula of metal drilling. To determine the parameters in our empirical model, we construct an experimental system and perform a group of drilling experiments on real bones. We implement our force model in a group of drilling simulations and compare the computational force with the original experimental data to testify its validity.

This paper is concerned with an integrated thermomechanical modeling and analysis of electronic packages. As the technology advances in terms of speed and density of circuit within a chip, the power dissipation increases exponentially. The packages are subjected to heating during fabrication, testing, and service. Due to the heterogeneous construction with wide mismatch of material properties, thermal stresses are induced which would result in mechanical failures such as cracking and delamination. It is essential to analyze the packages for thermal and stress fields and check their compliance with the design requirements. Earlier investigations were mostly based on approximate models such as plane-stress, plane-strain, and axisymmetric conditions. In reality, none of the packages satisfies the conditions associated with these models. In this work, 3D solid finite element with variable nodes, 8–21 nodes per element is employed. Software has been developed with the following features: sequentially coupled thermomechanical modeling, nonlinear transient solution capability, incompatible mode option when 8-node brick element is used, better estimation of nodal stresses by transformation from gauss point stresses, and quadratic criterion for delamination failure. A flipchip has been analyzed using the software developed for their thermal and stress fields. Numerical results indicate: the junction temperatures exceed the specification limits for higher heat dissipation, if appropriate cooling is not applied. The stresses in the die corner and at the solder balls are critical. Three-dimensional modeling is necessary for estimation of the same. Appropriate failure criterion was used in the failure prediction.

This study deals with preform maps for near net shape upsetting of aluminum billets. These maps have been developed using finite element analysis results considering 10 interfacial friction conditions and varying geometrical and processing parameters. Preform maps are experimentally verified using aluminum specimens. The proposed approach offers a powerful tool for near net shape upsetting.

Meshfree methods are effective tools for solving partial differential equations. The radial point interpolation method, a partial differential equation solver based on a meshfree approach, enables accurate imposition of displacement boundary conditions and has been successfully applied to elastostatic analysis of various kinds of three-dimensional solids. In this method, stiffness matrix construction accounts for the majority of CPU time required for the entire process, resulting in high computational costs, especially when higher-order numerical integration is applied for accurate matrix construction. An alternative method, modified radial point interpolation, was proposed to overcome this shortcoming and has accomplished fast computation of elastostatic solid analysis. The purpose of this study is to develop an algorithm for time-dependent simulation of three-dimensional elastic solids. We show that the modified radial point interpolation method also accelerates the construction of the mass matrix required for time-dependent analysis in addition to that of the stiffness matrix. In our approach, the problem domain is assumed to have an implicit function representation that can be constructed from a set of surface points measured using a three-dimensional scanning system. Several numerical tests for elastodynamic analysis of complex shape models are presented.

Delamination is one of the most common failure modes of laminated composite materials, and can be caused by manufacturing defects or impact loading. Under compression, a delaminated composite plate may buckle and tend to enlarge the delaminated area, which can lead to loss of global structural stability. This paper presents the elastic buckling and postbuckling analysis of an axially loaded beam-plate with an across-the-width delamination, located at a given depth below the upper surface of the plate. The analysis is done by considering a layered orthotropic plate containing through-width delamination, subjected to in-plane compression. The problem is analyzed by two approaches: (i) A simple analytical model for determining strain energy release rate is obtained using integral transform approach; (ii) A finite element representation of the problem is modeled and analyzed using MSC/NASTRAN and the buckling load is calculated.

The paper presents the dynamic behavior of a hollow rotor shaft with internal damping driven by a dissipative coupling. The coupling in the system is absolutely flexible in transverse and bending; however, it is assumed to be torsionally rigid. Bond graph is adopted for modeling as it facilitates the system modeling from the physical paradigm itself, and the model can be easily extended to incorporate modifications. Simulation results show interesting phenomenon of limiting behavior of rotor shaft with internal damping beyond the threshold speed of instability. It is further shown that the shaft entrainment frequency of the rotor shaft primarily depends on the ratio of external and internal damping.