International Journal of Computational Engineering Science

The effect of angular speed loss between the driver and driven pulleys for a flat belt transmission system is derived and analyzed by a rigorous three-dimensional finite element frictional contact analysis procedure established in this work. For modeling the flexible property of the flat belt, three-dimensional bar and eight-node brick elements are employed together to simulate the tension member and rubber layer, respectively. To accurately describe the bending effect of the rubber layer at the end zones of the contact area, the displacement approximation of the eight-node brick element is modified with the incremental Wilson displacement modes. In addition, to estimate the angular speed loss, appropriate frictional contact and loading conditions are provided to account for the physical contact phenomena between the belt and pulleys. The sliding region of the contact surfaces can thus be identified. The comparisons between the computed angular speed loss and referenced analytical/experimental results are made. Finally, the effects of dynamic friction coefficient, traction coefficient and material properties of the flat belt on the angular speed loss are studied as well.

High precision membranes are used in many current space applications. This paper presents a fully nonlinear membrane theory with forward and inverse analyses of high precision membrane structures. The fully nonlinear membrane theory is derived from Jaumann strains and stresses, exact coordinate transformations, the concept of local relative displacements, and orthogonal virtual rotations. In this theory, energy and Newtonian formulations are fully correlated, and every structural term can be interpreted in terms of vectors. Fully nonlinear ordinary differential equations (ODEs) governing the large static deformations of known axisymmetric membranes under known axisymmetric loading (i.e., forward problems) are presented as first-order ODEs, and a method for obtaining numerically exact solutions using the multiple shooting procedure is shown. A method for obtaining the undeformed geometry of any axisymmetric membrane with a known inflated geometry and a known internal pressure (i.e., inverse problems) is also derived. Numerical results from forward analysis are verified using results in the literature, and results from inverse analysis are verified using known exact solutions and solutions from the forward analysis. Results show that the membrane theory and the proposed numerical methods for solving nonlinear forward and inverse membrane problems are accurate.

This paper presents a new algorithm for the mobile robot path planning problem. The algorithm presented here applies an initialization heuristics and new operators to solve this problem and discusses how the operators are tuned to perform better. The algorithm adapts itself by tuning its operator probabilities according to the characteristics of the path generated so far. The fitness of the path is not only based on the length of the path but also determined on the basis of the smoothness of the path. The algorithm is tested for different environments with arbitrarily-shaped obstacles and dynamic environments. When dynamic obstacles are identified the algorithm finds the new path from the point of intervention and the original path is retained till that position. The algorithm is tested for five different environments.

A numerical study is performed to investigate unsteady thermal-fluid flow transport phenomenon in cavities under reduced gravity. Consideration is given to the influence of Marangoni convection and aspect ratio on the thermal and velocity fields in a two-dimensional cell. Here, it consists of two opposing vertical side walls heated at constant, at different temperature with the horizontal lower wall insulated and the upper face treated as nondeformable adiabatic free surface. The fluid temperature gradient in the cavity in the absence of Marangoni force under the reduced gravity is substantially decreased near the hot and cold vertical walls and the dominant heat transfer mechanism switches from convection into conduction, as time progresses. On the contrary, the corresponding flow pattern and isotherms are similar to that under normal gravity condition, resulting in a slight deterioration of the heat transfer performance, if Marangoni force drives the flow in the cavity. This Marangoni effect in cavities is affected by aspect ratio. Therefore the unsteady natural convection in the system considered is affected by the Marangoni force level and cavity size.

In this work, we study the distributed memory architecture, the parallelization of Hansen's algorithm which is an interval Branch-and-Bound algorithm for solving the continuous global optimization problem with inequality constraints. Since this algorithm is dynamic and irregular, we propose, in particular, some parallel algorithms dealing with balancing the load with respect to the quantity and the quality of boxes. Our proposed techniques are based on the criterion of the "best-first strategy" and also on the cyclic redistribution of the boxes. The numerical simulations are performed using the PROFIL/BIAS libraries^1,2 for computation and "MPI/C++" environment for communication.

The problem of estimating the bending stress distribution in the neighborhood of a crack located on a single line in an isotropic elastic plate of constant thickness is examined. The plate containing cracks is infinite and its boundary is subjected to bending moment or twisting moment. Using classical plate theory and integral transform techniques, the general formulae for the bending moment, twisting moment and bending stress distribution in an elastic plate acted upon by moment forces and containing cracks located on a single line are derived. The solution is obtained in detail, for the case in which there is a single crack in an infinite plate and the bending stress intensity factor is determined in a closed form and the results are compared with those obtained from finite element analysis. Close agreements between the analytical solution, numerical solution and reference solution were found in all cases.

A new finite difference method for the Helmholtz equation is presented. The method involves replacing the standard "weights" in the central difference quotients (Secs. 2.1, 2.2, and 2.3) by weights that are optimal in a sense that will be explained in the sections just mentioned. The calculation of the optimal weights involves some complicated and error-prone manipulations of integral formulas that is best done using computer-aided symbolic computation (SC). In addition, we discuss the important problem of interpolation involving meshes that have been refined in certain subregions. Analytic formulae are derived using SC for these interpolation schemes. Our results are discussed in Sec. 5. Some hints about the computer methods we used to accomplish these results are given in the Appendix. More information is available and access to that information is referenced.

While we do not want to make SC the focus of this work, we also do not want to underestimate its value. Armed with robust and efficient SC libraries, a researcher can comfortably and conveniently experiment with ideas that he or she might not examine otherwise.