PC-Based Computer Modeling of Combustion Processes

Constant and significant progress in both computer hardware and numerical algorithms, in recent years, have made it possible to investigate complex phenomena in engineering systems using computer modeling and simulations. Advanced numerical simulations can be treated as an extension of traditional analytical-theoretical analyses. In such cases, some of the simplifying assumptions can usually be dropped and the nonlinear interactions between various processes can be captured. One of the most complex engineering processes encountered in industry is a combustion process utilized either for power/thrust generation or incineration. However, even nowadays, because of the high level of complexity of the general problem of a combustion process in practical systems, it is not currently possible to simulate directly all the length and time scales of interest. Simplifying assumptions still need to be made, but they can be less drastic than in analytical approaches. Therefore, another view of numerical simulations is as a tool to simulate idealized systems and conduct numerical experiments. Such numerical experiments can be complementary to laboratory experiments and can also provide more detailed, nonintrusive diagnostics. Therefore, simulations, along with theory and laboratory experiments, can provide a more complete picture and better understanding of a combustion process. As an example of computer modeling of industrial combustion systems, an enclosed spray flame was considered. Such a flame can frequently be encountered in power generation units, turbine engines, and incinerators. Both the physical and mathematical models were formulated based on data from earlier laboratory studies and results obtained for open air spray flames. The purpose of this study was to use those data as model input to predict the characteristics of a confined flame and provide a means of optimizing the system design with a PC computer.

Slurry Residue Removal in Post Chemical Mechanical Polishing

The megasonic cleaning process proved to be an essential process in cleaning silicon wafers after processes such as pre-oxidation, pre-CVD, pre-EPI, post-ASH and lately post-CMP. Current post-CMP cleans are contact cleaning techniques. These contact techniques have a low throughput and may cause wafer scratching. In addition, in contact cleaning, brush shedding which occurs under many operating conditions causes additional particulate contamination. There is a need for an effective post-CMP cleaning process. Megasonic cleaning provides the best alternative or compliment to brush clean.

Implementation of a Design Tool for Conceptual Design of Integrally Fastened Assemblies

The proper use of integral attachment features in mechanical assemblies has been more of an art than an engineering science. An organized set of design steps for generating conceptual integral attachment designs has recently been developed based on work begun by Bonenberger. These steps outline a formal design methodology for exploring the design space of possible alternative attachment concepts. This paper describes the development of a software tool that attempts to implement the integral attachment design methodology to assist a designer in developing attachment concepts. The tool is implemented using the Java programming language. A graphical interface is used to present the methodology as a series of options that approximate the design situation. This hides many of the details of the methodology in favor of ease of use. The end result is a set of suggestions for integral fasteners that are matched to the design situation. A discussion of how the hundreds of images are handled using Java is provided. A sample case study illustrates the approach of the program. The tool represents one of the few examples of a design tool aimed specifically at generating design concepts.

Systematic Derivation of a Standard Set of Declarative Constraints for Shape Definition in CAD

This paper describes the derivation of a consistent and comprehensive set of geometrical constraints for shape definition in Computer-Aided Design. These are needed to enable compatibility in parametric data exchange and to promote both standard capabilities and predictable solutions from constraint solving software kernels. The paper look at the mathematical basis for constraints present in the literature and elaborates about all types of constraints that can be described by the same mathematical basis. The approach considers all combinations of distance and angle constraints, on one point or all points of curves and surfaces, as well as transformations and mappings that are required in mechanical design.

A Process Planning Method for Improving the Build Performance in Stereolithography

A process planning method is presented in this paper to aid stereolithography users in the selection of appropriate values of build process variables in order to achieve specific goals and characteristics that are desirable in the end prototype. To accomplish this, user-defined input in the form of goal preferences and feature tolerances are used to control how the prototype will be built by way of process planning. The user inputs will be used to drive the creation of the process plan so that a prototype is produced, which reflects the intent of the operator. The process planning method is adapted from multi-objective optimization and utilizes empirical data, analytical models, and heuristics to quantitatively relate build process variables to goals of surface finish, accuracy, and build time. The objective is to render decision support by handling tradeoffs among conflicting goals quantitatively and give the user some degree of insight into what quality of prototype may ultimately be produced. The process planning method is demonstrated on a part with non-trivial geometric features.

Wearable Computers and Augmented Reality in an Industrial Application

In the modern industrial scenario, the technological assets of new working methods and machinery in factory plants grow rapidly. Nevertheless, a reverse situation occurs in terms of availability of trained personnel within the subject area. Moreover, even the most experienced technician is faced with a continual need to update his/her skills. In respect to the training activities, more realism and a greater effectiveness could be achieved if the trainee could learn a new technology directly in the real working place. In this paper, considerations are presented for the use of an innovative hardware and Augmented Reality as platform components for the learning material to this training scenario. Both components are described with emphasis on their suitability to the target activity. The proposed platform encompasses a body-worn and wireless-networked computer, and software with specific features to assist the computer user in his/her task by enriching the content of the application environment. The software component, which addresses the application goals and required adaptations to the platform, is presented.

Using Genetic Algorithms to Set Target Values for Engineering Characteristics in the House of Quality

As part of a strategy for obtaining preliminary design specifications from the House of Quality, genetic algorithms were used to generate and optimize preliminary design specifications for an automotive case study. This paper describes the House of Quality for the automotive case study. In addition, the genetic algorithm chosen, the genetic coding, the methods used for mutation and reproduction, and the fitness and penalty functions are descrobed. Methods for determining convergence are examined. Finally, test results show that the genetic algorithm produces reasonable preliminary design specifications.

Towards Combining Digitization Techniques in the Generation of Reverse Engineering Data Sets

Reverse engineering (RE), may be defined as the process of generating computer aided design models (CAD) from existing or prototype parts. The process has been used for many years in industry. It has markedly increased in implementation in the past few years, primarily due to the introduction of rapid part digitization technologies. Current industrial applications include CAD model construction from artisan geometry, such as in automotive body styling, the generation of custom fits to human surfaces, and quality control. This paper summarizes the principles of operation behind many commercially available part digitization technologies, and discusses techniques involved in part digitization using a coordinate measuring machine (CMM) and laser scanner. An overall error characterization of the laser scanning digitization process is presented for a particular scanner. This is followed by a discussion of the merits and considerations involved in generating combined data sets with characteristics indicative of the design intent of specific part features. Issues in facilitating the assembly, or registration, of the different types of data into a single point set are discussed.

Digital Library Support for Engineering Design and Manufacturing

This paper describes our initial efforts to deploy a digital library to support engineering design and manufacturing. This experimental testbed, The Engineering Design Repository, is an effort to collect and archive public domain engineering data for use by researchers and engineering professionals. CAD knowledge-bases are vital to engineers, who search through vast amounts of corporate legacy data and navigate online catalogs to retrieve precisely the right components for assembly into new products. This research attempts to begin addressing the critical need for improved computational methods for reasoning about complex geometric and engineering information. In particular, we focus on archival and reuse of design and manufacturing data for mechatronic systems. This paper presents a description of the research problem and an overview of the initial architecture of testbed.

JAVA™-Based Design Calculator for Integral Snap-Fits

Many different types of snap-fits have been developed to replace conventional fasteners, and research efforts have been made to characterize their performance. It is often tedious to look for design equations for unique types of snap-fits to calculate the insertion and retention forces. If found, these equations tend to be long, complex, and difficult to use. For this reason, a snap-fit calculator has been created to help in designing integral attachment features. Studies of seven most commonly used snap-fits (annular snap, bayonet-and-finger, cantilever hook, cantilever-hole, compressive hook, L-shaped hook, and U-shaped, hook) were used to provide the equations implemented in this snap-fit calculator, more fasteners than any other snap-fit calculator available. This tool aids in designing snap-fits to meet specific loading requirements by allowing the designer to size the feature to obtain desired estimates for maximum insertion and retention forces. The software for this design tool was written in JAVA™ language that is independent of operating system platforms and can be distributed at a company site-wide over an intranet or worldwide over the Internet. This makes it easily accessible to a user, and universal upgrades can be achieved by simply updating the software at the server location. Designers will find this tool to be useful in the design process and the most convenient way to estimate the performance of snap-fits. This paper describes the development and operation of the IFP snap-fit calculator including several case studies comparing the calculated results to experimental data.