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.     

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%.     

Modeling and simulation of material removal with particulate flows

In this work a multibody collision model, ame-nable to large-scale computation, is developed to simulate material removal with particulate flows. This model is developed by computing momentum exchange to account for different force interactions: (1) particle–particle interaction, (2) particle–fluid interaction, and (3) particle–surface interaction. For the particle-fluid interaction, a velocity field for the fluid is assumed to be known, and the drag force on the particles is computed from this field. In the particle–surface interaction, the Boussinesq solution for a point load on an elastic half-space is used along with the von-Mises yield criterion to determine the amount of material removed. Employing this model, inverse problems are then constructed where combinations of the abrasive particle size, the particle size distribution, the flow velocity, etc., are sought to maximize the efficiency of the process. A genetic algorithm is used to treat this inverse problem, and numerical examples are given to illustrate the overall approach.     

Modeling and Simulation of Laser Processing of Particulate-Functionalized Materials

The objective of this paper is to focus on one of the “building blocks” of additive manufacturing technologies, namely selective laser-processing of particle-functionalized materials. Following a series of work in Zohdi (Int J Numer Methods Eng 53:1511–1532, 2002; Philos Trans R Soc Math Phys Eng Sci 361(1806):1021–1043, 2003; Comput Methods Appl Mech Eng 193(6–8):679–699, 2004; Comput Methods Appl Mech Eng 196:3927–3950, 2007; Int J Numer Methods Eng 76:1250–1279, 2008; Comput Methods Appl Mech Eng 199:79–101, 2010; Arch Comput Methods Eng 1–17. doi: 10.1007/s11831-013-9092-6, 2013; Comput Mech Eng Sci 98(3):261–277, 2014; Comput Mech 54:171–191, 2014; J Manuf Sci Eng ASME doi: 10.1115/1.4029327, 2015; CIRP J Manuf Sci Technol 10:77–83, 2015; Comput Mech 56:613–630, 2015; Introduction to computational micromechanics. Springer, Berlin, 2008; Introduction to the modeling and simulation of particulate flows. SIAM (Society for Industrial and Applied Mathematics), Philadelphia, 2007; Electromagnetic properties of multiphase dielectrics: a primer on modeling, theory and computation. Springer, Berlin, 2012), a laser-penetration model, in conjunction with a Finite Difference Time Domain Method using an immersed microstructure method, is developed. Because optical, thermal and mechanical multifield coupling is present, a recursive, staggered, temporally-adaptive scheme is developed to resolve the internal microstructural fields. The time step adaptation allows the numerical scheme to iteratively resolve the changing physical fields by refining the time-steps during phases of the process when the system is undergoing large changes on a relatively small time-scale and can also enlarge the time-steps when the processes are relatively slow. The spatial discretization grids are uniform and dense enough to capture fine-scale changes in the fields. The microstructure is embedded into the spatial discretization and the regular grid allows one to generate a matrix-free iterative formulation which is amenable to rapid computation, with minimal memory requirements, making it ideal for laptop computation. Numerical examples are provided to illustrate the modeling and simulation approach, which by design, is straightforward to computationally implement, in order to be easily utilized by researchers in the field. More advanced conduction models, based on thermal-relaxation, which are a key feature of fast-pulsing laser technologies, are also discussed.