An investigation into establishing a generalised approach for defining similarity metrics between 3D shapes for case-based reasoning (CBR)

This thesis investigates the feasibility of establishing a generalised approach for defining similarity metrics between 3D shapes for the casting design problem in Case-Based Reasoning (CBR). This research investigates a new approach for improving the quality of casting design advice achieved from a CBR system using casting design knowledge associated with past cases. The new approach uses enhanced similarity metrics to those used in previous research in this area to achieve improvements in the advice given. The new similarity metrics proposed here are based on the decomposition of casting shape cases into a set of components. The research into metrics defines and uses the Component Type Similarity Metric (CTM) and Maximum Common Subgraph (MCS) metric between graph representations of the case shapes and are focused on the definition of partial similarity between the components of the same type that take into account the geometrical features and proportions of each single shape component. Additionally, the investigation extends the scope of the research to 3D shapes by defining and evaluating a new metric for the overall similarity between 3D shapes. Additionally, this research investigates a methodology for the integration of the CBR cycle and automation of the feature extraction from target and source case shapes. The ShapeCBR system has been developed to demonstrate the feasibility of integrating the CBR approach for retrieving and reusing casting design advice. The ShapeCBR system automates the decomposition process, the classification process and the shape matching process and is used to evaluate the new similarity metrics proposed in this research and the extension of the approach to 3D shapes. Evaluation of the new similarity metrics show that the efficiency of the system is enhanced using the new similarity metrics and that the new approach provides useful casting design information for 3D casting shapes. Additionally, ShapeCBR shows that it is possible to automate the decomposition and classification of components that allow a case shape to be represented in graph form and thus provide the basis for automating the overall CBR cycle. The thesis concludes with new research questions that emerge from this research and an agenda for further work to be pursued in further research in the area

Computer-aided process planning (CAPP) SORICH

The last two decades have witnessed the increasing role of the computer in the process planning function. This has been further enhanced by the advent of the knowledge based expert system, and its impact on Computer Aided Process Planning (CAPP). CAPP has emerged as a strategic link between design and manufacture. This thesis discusses the various methods used in the process planning function. Group Technology (GT) plays a pivotal role in establishing CAPP. The utilization of Artificial Intelligence techniques in CAPP is listed. This study also presents an Interactive Software adaptive to product/part configuration variables

Selected Examples for Space Manufacturing Processes/ Facilities and Experiments

The unique effect of the orbital zero- and low-g environment upon the behavior of liquids offers the potential of new material processing techniques not feasible under terrestrial conditions. A number of promising processes and the related product capabilities are discussed in detail. On the basis of an evaluation of process effectiveness and facility requirements, an example for a potential three-phase space experiment program is presented

The materials processing research base of the Materials Processing Center

The goals and activities of the center are discussed. The center activities encompass all engineering materials including metals, ceramics, polymers, electronic materials, composites, superconductors, and thin films. Processes include crystallization, solidification, nucleation, and polymer synthesis

Nonterrestrial utilization of materials: Automated space manufacturing facility

Four areas related to the nonterrestrial use of materials are included: (1) material resources needed for feedstock in an orbital manufacturing facility, (2) required initial components of a nonterrestrial manufacturing facility, (3) growth and productive capability of such a facility, and (4) automation and robotics requirements of the facility

A Review On Alpha Case Formation And Modeling Of Mass Transfer During Investment Casting Of Titanium Alloys

Titanium alloys have excellent corrosion resistance, high temperature strength, low density, and biocompatibility. Therefore, they are increasingly used for aerospace, biomedical, and chemical applications. Investment casting is a well-established process for manufacturing near-net-shape intricate parts for such applications. However, mass transfer arising from metal-mold reactions is still a major problem that drastically impairs the surface and properties of the castings. Although there have been astounding developments over the past 20 years, they remain scattered in various research papers and conference proceedings. This review summarizes the current status of the field, gaps in the scientific understanding, and the research needs for the expansion of efficient casting of titanium alloys. The uniqueness of this paper includes a comprehensive analysis of the interfacial reactions and mass transfer problems. Additionally, momentum and heat transfer are presented where applicable, to offer a holistic understanding of the transport phenomena involved in investment casting. Solutions based on modeling and experimental validation are discussed, highlighting ceramic oxide refractories like zirconia, yttria, calcia, alumina, and novel refractories namely, calcium zirconate and barium zirconate. It was found that while mold material selection is vital, alloy composition should also be carefully considered in mitigating metal-mold reactions and mass transfer

Characterization of Porous Media and Refractory Materials

Because of its unique advantages on energy savings and casting complex shaper, Lost Foam Casting (LFC) has been widely used as a replacement to the conventional techniques (sand and investment castings). In order to continuously improve the quality of the Lost Foam Casting process for reducing scrap rate and increasing energy savings, the US Department of Energy through its National Industrial Competitiveness through Energy, Environment, and Economics (NICEEE) program sponsored the present study to develop new characterization techniques for enhancing the understanding of the fundamental properties of the refractory materials used in The Lost Foam Casting process. In this study, new techniques are proposed to characterize the refractory materials’ properties such as particle size, particle shape, rheological behavior, transport properties, microstructure, thickness, as well as packing properties. The rheological properties of the refractory coating slurries are characterized by a series of laboratory experiments using a rotational rheometer including the creep and recovery test, the thixotropic loop test, and oscillatory tests. A number of commercial particle sizing instruments based on different theoretical backgrounds are investigated for evaluating a suitable technique for reliable characterization of slurries used in this research. A quantitative approach to characterize particle shape is also investigated for particles in the refractory coating slurry. This study also proposes a new apparatus to evaluate the transport properties and microstructure of the refractory coatings. The proposed interpretation method of measured gas flow data considers the “slippage” and inertia effects that occur in measuring gas permeability of porous materials. The microstructure information obtained from the proposed technique is found to be well correlated with the transport properties of the porous coating materials. A procedure using a three-dimensional computational fluid dynamics code (FLOW3D) is developed to simulate experimental gas flow data for solving complex boundary value problems. This paper also presents a novel coating thickness measurement system for the dry refractory LFC coatings. By comparing a number of commercially available refractory coatings, it is found that the coating thickness on the expandable polystyrene foam patterns is not uniform and depends on the coating type, topography of the foam surface, and coating properties such as surface tension, thixotropic loop area, mean particle size diameter, and viscosity. In this study, the effects of dilution and dispersion on the coating properties such as transport properties and microstructures are also investigated. Results show that the dilution and dispersion have opposing influences on the pore size and transport properties. The pore characterization technique developed in this study is used to determine the effects of drying (oven versus air dry) on the pore size and transport properties. In addition, this study also includes another part of the permeability system, the un-bonded granular materials used in the Lost Foam Casting process. Three types of particle sizing techniques (sieve analysis, Laser Light Scattering and Imaging Analysis) are used to characterize the particle size and shape information of two types of un-bonded granular materials (sand and mullite). A three-dimensional (3-D) computer program is developed to simulate the packing behavior of granular materials at a loose state using a “drop and roll” method. This study provides a systematic characterization of the LFC refractory coating slurries, dried refractory coating, and the granular media. This study also demonstrates the application of proposed characterization techniques for coating quality control using statistical process control charts. In addition, numerical models are also developed to predict the coating performance such as its coating thickness and transport properties. The results from this study are likely to have a significant impact on improving the Lost Foam Casting process. The characterization tools developed in this study are being currently used in a large Lost Foam Casting foundry for improving the process at production scale