Maintenance and Parts Fabrication by Reverse Engineering

With the collapse of the Eastern block, once Egypt’s major industry supplier for machinery and spare parts, and the lack of skilled manpower, the Egyptian industry is finding it difficult to maintain its machinery and industrial base and to compete with the much more sophisticated and coordinated industries abroad. The cutoff of supply of maintenance parts from the Eastern Block, prompt the use of modern reverse engineering (RE) methods in the capturing the geometrical configuration and fabrication of rare maintenance parts, in support of the Egyptian Industry. This paper demonstrates, as a proof of concept, the use of the technology of RE in the fabrication of parts. The success of the experiment initiated a much wider application to the technology, that of patterns making in support of the casting industry. This will provide an accurate and expeditious means to properly maintain industrial plants and produce compatible spare pails urgently needed.

Digital Watermarking for 3D Polygonal Model Based on Wavelet Transform

Recently, much interest is being taken in a method to protect the copyright of digital data and prevent illegal duplication of it. However, in the area of CAD/CAM and CG, there are no effective ways to protect the copyright of the 3D geometric models. As a first step to solve this problem, a new digital watermarking method for 3D polygonal models is introduced in this paper. Watermarking is one of the copyright protection methods where an invisible watermark is secretly embedded into the original data. The proposed watermarking method is based on the wavelet transform (WT) and multi-resolution representation (MRR) of the polygonal model. The watermark can be embedded in the large wavelet coefficient vectors at various resolution levels of the MRR. This makes the embedded watermark imperceptible and invariant to the affine transformation, and also makes the control of the geometric error caused by the watermarking reliable.

A Numerical Simulation of Gas Jet Diffusion Flames Enveloped by a Cascade of Venturis

“Venturi-cascading” technique has been developed in the Combustion Laboratory at the University of Oklahoma. The goal was to control the pollutant emissions of diffusion flames by modifying the air infusion rate into the flame. The modification was achieved by installing a cascade of venturis around the burning gas jet. The basic idea behind this technique is controlling the stoichiometry of the flame through changing the flow dynamics and rates of mixing in the combustion zone with a set of venturis surrounding the flame. A propane jet diffusion flame at burner-exit Reynolds number of 5100 was examined with a set of venturis of specific sizes and spacing arrangement. The thermal and composition fields of the baseline and venturi-cascaded flames were numerically simulated using CFD-ACE+, an advanced computational environment software package. The instantaneous chemistry model was used as the reaction model. The concentration of NO was determined through CFD-POST, a post processing utility program for CFD-ACE+. The numerical results showed that, in the near-burner, mid-flame and far-burner regions, the venturi-cascaded flame had lower temperature by an average of 13%, 19% and 17%, respectively, and lower CO2 concentration by 35%, 37%. and 32%, respectively, than the baseline flame. An opposite trend was noticed for O2 concentration; the cascaded flame has higher O2 concentration by 7%, 26% and 44%, in average values, in the near-burner, mid-flame and far-burner regions, respectively, than in the baseline case. The results also showed that, in the near-burner, mid-flame, and far-burner regions, the venturi-cascaded flame has lower NO concentrations by 89%, 70% and 70%, in average values, respectively, compared to the baseline case. The simulated results were compared with the experimental data. Good agreement was found in the near-burner region. However, the agreement was poor in the downstream regions. The numerical results substantiate the conclusion, which was drawn in the experimental part of this study, that venturi-cascading is a feasible method for controlling the pollutant emissions of a burning gas jet. In addition, the numerical results were useful to interpret the experimental measurements and understand the thermo-chemical processes involved. The results showed that the prompt-NO mechanism plays an important role besides the conventional thermal-NO mechanism.

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.