A protocol for distributed simulation on a microcomputer network

The computer industry has evolved very rapidly from single-user computers to computer networks where users are able to share both local and remote files. Networks of microcomputers facilitate the integration of all information processing for distributed applications such as database processing and electronic mail. One management application of promising potential for computer networks is distributed simulation. Simulation analysis can be useful to essentially all problem-solving and decision-making on the job.

To implement a particular distributed application, computer communication between processors must be considered. Unlike expensive multiprocessor computers, networks of less-expensive microcomputers do not have pre-established communication paths between processors. This paper addresses how this obstacle may be overcome by using communication protocols based on the Open Systems Interconnection (OSI) reference model. Protocol services needed to support a distributed simulation environment will be identified, and their implementation through a prototype will then be investigated and evaluated.     

Rapid Simulation of Laser Processing of Discrete Particulate Materials

The objective of this paper is to develop a computational model and corresponding solution algorithm to enable rapid simulation of laser processing and subsequent targeted zonal heating of materials composed of packed, discrete, particles. Because of the complex microstructure, containing gaps and interfaces, this type of system is extremely difficult to simulate using continuum-based methods, such as the Finite Difference Time Domain Method or the Finite Element Method. The computationally-amenable model that is developed captures the primary physical events, such as reflection and absorption of optical energy, conversion into heat, thermal conduction through the microstructure and possible phase transformations. Specifically, the features of the computational model are (1) a discretization of a concentrated laser beam into rays, (2) a discrete element representation of the particulate material microstructure and (3) a discrete element transient heat transfer model that accounts for optical (laser) energy propagation (reflection and absorption), its conversion into heat, the subsequent conduction of heat and phase transformations involving possible melting and vaporization. A discrete ray-tracking algorithm is developed, along with an embedded, staggered, iterative solution scheme, which is needed to calculate the optical-to-thermal conversion, particle-to-particle conduction and phase-transformations, implicitly. Numerical examples are given, focusing on concentrated laser beams and the effects of surrounding material conductivity, which draws heat away from the laser contact zone, thus affecting the targeted material state.     

A Computational Model for Interfacial Damage Through Microstructural Cohesive Zone Relaxation

A model introducing cohesive zones around material interfaces to simulate interfacial damage in microheterogeneous materials is developed. The material behavior within the cohesive zones is unknown a-priori, and is weakened, or "relaxed", on the continuum level from an initially undamaged state, by a reduction of the spatially variable elasticity tensor's eigenvalues. This reduction is initiated if constraints placed on the microstress fields, for example critical levels of pressure or deviatoric stresses, are violated. Outside of the cohesive zones the material is unaltered. Numerical computations are performed, employing the finite element method, to illustrate the approach in three dimensional applications.     

Statistical Analysis of Power Consumption in Surface Grinding

A method of identifying the individual as well as the combined effects of the different independent factors on the power consumption in the grinding process is presented. Physical experimentation coupled with subsequent statistical analysis, the factorial experimentation technique, was applied to further the understanding of this process. Mathematical models were developed to estimate the level of the dependent factor, the power consumption. Optimum conditions that result in the lowest level of power consumption with the maximum rate of metal removed are evaluated and discussed.     

High-speed impact of electromagnetically sensitive fabric and induced projectile spin

This work deals with the dynamic contact of a rigid body with a deformable electromagnetically sensitive fabric structure, represented by a network model. Of particular interest are the electromagnetically induced forces generated on the fabric, which are proportional to the external electric field (E ^EXT ) and the velocity crossed with the external magnetic field (v × B ^EXT ). These forces transmit reactions to the rigid contacting object, which can induce rotational motion. Modeling and simulation of this effect can be useful in ballistic shielding applications, because the rotation of an incoming, ogival, projectile allows it to be more easily impeded. A modular formulation for the deformation of impacted fabric structures, represented by a network model, is developed in this paper, characterized by (1) stretching of interconnected yarn networks, described by simple constitutive relations, including yarn damage, (2) interaction with impacting objects, incorporating contact with friction and (3) electromagnetic sensitivity and actuation, demonstrating how the Lorentz force can be harnessed to break symmetric deformation patterns in order to induce spin onto an incoming object, whether that object is electromagnetically sensitive or not.     

Multi-Scale Analysis of Fretting Fatigue in Heterogeneous Materials Using Computational Homogenization

This paper deals with modeling of the phenomenon of fretting fatigue in heterogeneous materials using the multi-scale computational homogenization technique and finite element analysis (FEA). The heterogeneous material for the specimens consists of a single hole model (25% void/cell, 16% void/cell and 10% void/cell) and a four-hole model (25% void/cell). Using a representative volume element (RVE), we try to produce the equivalent homogenized properties and work on a homogeneous specimen for the study of fretting fatigue. Next, the fretting fatigue contact problem is performed for 3 new cases of models that consist of a homogeneous and a heterogeneous part (single hole cell) in the contact area. The aim is to analyze the normal and shear stresses of these models and compare them with the results of the corresponding heterogeneous models based on the Direct Numerical Simulation (DNS) method. Finally, by comparing the computational time and % deviations, we draw conclusions about the reliability and effectiveness of the proposed method.     

A geometrically nonlinear size-dependent hypothesis for porous functionally graded micro-plate

The static bending behavior of porous functionally graded (PFG) micro-plate under the geometrically nonlinear analysis is studied in this article. A small-scale nonlinear solution is established using the Von-Kármán hypothesis and the modified couple stress theory (MCST). To obtain the deflection of the plate, the Reddy higher-order plate theory coupled with isogeometric analysis (IGA) is utilized. The distribution of porosities is assumed to be even and uneven across the plate’s thickness and the effective material properties of porous functionally graded micro-plate are calculated using the refined rule-of-mixture hypothesis. The influence of power index, porosity parameter and material length scale parameter on the nonlinear behaviors of static bending of porous FGM micro-plates are also investigated using several numerical examples.

     

Variations in the site and size of third ventriculocisternostomy

Seventy-eight cases of late-onset, non-communicating hydrocephalus were operated upon by third ventriculocisternostomy. The distortion in the anatomy of the dilated third ventricular floor dictated the selection of the target area. The optimal site for the perforation was the translucent, bluish and thinned out part of the floor. This was variable and in 76.9% not in the midline with more than one fenestra done in 35.9%. the size of the ventriculocisternostomy needed not be around 5 mm. Smaller sized openings in a taut floor (60.3%) served the same purpose as bigger ones in a redundant area (39.7%). The success of the procedure could be predicted from the profuse downward flow of cerebrospinal fluid through the perforation, "Whirl Sign". An acceptable assurance of our results was confirmed both clinically and radiologically. The outcome in our series had four grades, namely cured in 78.2%, ameliorated, but still needed diversion, in 16.7%, status quo in 2.5%, and complicated in 2.5%.     

Improvement of Flat Surfaces Quality of Aluminum Alloy 6061-O By a Proposed Trajectory of Ball Burnishing Tool

Burnishing is a profitable process of surface finishing due to its ability to be automated, which makes burnishing method more desirable than other finishing methods. To obtain high surface finish, non-stop operation is required for CNC machine and we can attain that by choosing a suitable trajectory of the finishing tool. In other words, burnishing paths should be multidirectional rather than monotonic, in order to cover uniformly the surface. Indeed, the burnishing force is also a key parameter of the burnishing process because it determines the degree of plastic deformation, and that makes determining the optimum burnishing force an essential step of the burnishing process a success. Therefore, we consider the strategy of ball burnishing path and the burnishing force as variable parameters in this study. In this paper, we propose a new strategy of burnishing tool path with trochoid cycles that achieves a multidirectional burnishing of the surface according to various patterns. Taking into consideration the optimum burnishing force, to improve flat surface finish of AL6061-O samples by reducing the surface roughness parameter (Rz). Experiments carried out on 3-axis milling machine show that the proposed trochoidal path is more effective than the conventional one.