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Machining operations are widely used to produce parts with different shapes and complicated profiles. As a machining operation, broaching is commonly used for the machining of a broad range of complex internal and external profiles either circular or non-circular such as holes, keyways, guide ways, and slots on turbine discs having fir-tree shape. Broaching is performed by pushing or pulling a tapered tool through the workpiece to remove the unwanted material and produce the required profile. Broaching is also acknowledged because of its high productivity and attainable surface quality in comparison to the other machining processes. The objective of this thesis is to simulate the broaching operation and use the results to present a methodology for optimum design of the broaching tools. In the course of the presented thesis, a new B-spline based geometric model is developed for broaching cutting edges followed by model validation using 3D ACIS modeller. To study the mechanics of cutting and generated cutting forces during broaching operation, an energy based force model is presented which can predict the cutting forces based on the power spent in the cutting system. An experimental investigation is conducted in order to confirm the estimated forces. The integrity of the broached surface is also investigated by focusing on surface roughness, subsurface microhardness, and subsurface microstructure as three major parameters of surface integrity. An optimization procedure for broaching tools design is presented in this thesis. A mathematical representation of broaching tooth geometry is also presented which is used to simulate the tooth as a cantilevered beam subjected to a distributed load. The beam is solved considering the given design constraints to achieve optimum geometric parameters for maximum durability and performance. / UOIT

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Blend recognition and suppression from a tessellated model is important in applications such as model simplification in analysis and collaborative design where tessellated models are being used. This could also be used to pre-process the model before attempting to recognize form features in it. A procedure is described for recognizing and subsequently suppressing blends (fillets/rounds) in a tessellated model of a part. Earlier efforts on recognizing secondary features such as blends have used the boundary representation (B-Rep) of the part as input. Blend recognition and suppression from a tessellated model has not been addressed to the best of our knowledge. There has been work reported on the related problem of segmentation of tessellated surfaces. Segmentation refers to the decomposition of the object into regions where the underlying surfaces having similar characteristics. The segmented surface may be of any of surface like plane surface. There are two broad approaches to segmentation - vertex-based and edge-based. The vertex-based method clusters triangles consisting of connected vertices having the same attribute. One drawback of this method is that the boundaries of the clustered regions are not clearly defined due to difference in the labels of contiguous vertices. The edge-based method is based upon the dihedral angle at each edge in the tessellated model. The main drawback of this method is that edges in the boundary of the segmented patches are disconnected. This will result in an incomplete bounding loop when used for recognizing features. Smooth transitions at the boundary of features cannot be trapped with this approach. These techniques cannot be therefore used for recognizing blends. There have been efforts to recognize and suppress blends in a B-Rep model. Suppressing blend features in a B-Rep model is easier (compared to suppression from tessellated model) because smooth edges provide a clue to presence of blends. In the case of a tessellated model, the bounding loop of blends will not consist of smooth edges and no explicit signature is available for blends. In B-Rep model, information about the radius of blend is also available while this is not directly available in a tessellated model. Constant radius blends meet the requirements of most blending features encountered in mechanical part design. The surfaces forming a constant radius blend may be classified as cylindrical, spherical and toroidal surfaces. Spherical blend is formed by a blending operation at a vertex at which either three concave linear edges or three convex linear edges are incident. Blending operation on a linear edge forms cylindrical blend. Toroidal blend is formed by a blending operation on a circular edge. This circular edge may be closed (end vertices are identical) or open. Toroidal blend is also formed at a vertex at which at least one convex and one concave edge is incident. So toroidal blend can be classified into closed toroidal blend, open toroidal blend and vertex toroidal blend. In recognition process, for every triangle, cylindrical, spherical and toroidal surface parameters are calculated. In the second step, triangles having same surface parameters are clustered. The cluster of triangles are then classified as a blend or a form feature. Finally, toroidal blends are classified as one of the three types of toroidal blend. Procedures for the suppression of edge cylindrical blend and edge toroidal blend are described. At the present time, vertex blends are not suppressed individually. Rather in the process of suppressing edge blends, vertex blends are also suppressed. The parent surfaces that were blended are identified using the bounding loops of the blends. Triangles in the blend are then deleted and the parent surfaces are extended to suppress the feature. The key issues in suppression are - identification of all the surfaces at the blend, identification of the entities that were blended (edges and vertices) and updating the tessellated model. Results of constant radius blend recognition and suppression, on benchmark parts from NIST design repository are presented. This is followed by a discussion on the correctness of the recognition procedures. The thesis concludes by summarizing the contributions and identifies the following are as recognition of variable radius blends, blends on non-linear surfaces, suppression of all small volumetric feature as areas for further research.

Indiana University-Purdue University Indianapolis (IUPUI) / In a multifidelity structural design process, depending on the required analysis, different levels of structural models are needed. Within the aerospace design, analysis and optimization community, there is an increasing demand for automatic generation of parametric feature tree (build recipe) attributed multidisciplinary models. Currently, this is mainly done by creating separate models for different disciplines such as mid-surface model for aeroelasticity, outer-mold line for aerodynamics and CFD, and built-up element model for structural analysis. Since all of these models are built independently, any changes in design parameters require updates on all the models which is inefficient, time-consuming and prone to deficiencies. In this research, Engineering Sketch Pad (ESP) is used to create attribution and maintain consistency between structural models with different fidelity levels. It provides the user with the ability to interact with a configuration by building and/or modifying the design parameters and feature tree that define the configuration. ESP is based an open-source constructive solid modeler, named OpenCSM, which is built upon the OpenCASCADE geometry kernel and the EGADS geometry generation system. The use of OpenCSM as part of the AFRL’s CAPS project on Computational Aircraft Prototype Syntheses for automatic commercial and fighter jet models is demonstrated. The rapid generation of parametric aircraft structural models proposed and developed in this work will benefit the aerospace industry with coming up with efficient, fast and robust multidisciplinary design standardization of aircraft structures. Metallic aircraft wings are usually not optimized to their fullest potential due to shortage of development time. With roughly \$1000 worth of potential fuel savings per pound of weight reduction over the operational life of an aircraft, airlines are trying to minimize the weight of aircraft structures. A stiffness based strategy is used to map the nodal data of the lower-order fidelity structural models onto the higher-order ones. A simple multi-fidelity analysis process for a parametric wing is used to demonstrate the advantage of the approach. The loads on the wing are applied from a stick model as is done in the industry. C program is created to connect the parametric design software ESP, analysis software Nastran, load file and design configuration file in CSV format. This problem gets compounded when it comes to optimization of composite wings. In this study, a multi-level optimization strategy to optimize the weight of a composite transport aircraft wing is proposed. The part is assumed to initially have some arbitrary number of composite super plies. Super plies are a concept consisting of a set of plies all arranged in the same direction. The thickness and orientation angles of the super plies are optimized. Then, each ply undergoes topometry optimization to obtain the areas of each super ply taking the least load so that it could be cut and removed. Each of the super plies are then optimized for the thickness and orientation angles of the sub plies. The work presented on this paper is part of a project done for Air Force Research Laboratory (AFRL) connecting the parametric geometry modeler (ESP) with the finite element solver (Nastran).

No / Both prominent feature points and geodesic distance are key factors for mesh segmentation. With these two factors, this paper proposes a graph cut based mesh segmentation method. The mesh is first preprocessed by Laplacian smoothing. According to the Gaussian curvature, candidate feature points are then selected by a predefined threshold. With DBSCAN (Density-Based Spatial Clustering of Application with Noise), the selected candidate points are separated into some clusters, and the points with the maximum curvature in every cluster are regarded as the final feature points. We label these feature points, and regard the faces in the mesh as nodes for graph cut. Our energy function is constructed by utilizing the ratio between the geodesic distance and the Euclidean distance of vertex pairs of the mesh. The final segmentation result is obtained by minimizing the energy function using graph cut. The proposed algorithm is pose-invariant and can robustly segment the mesh into different parts in line with the selected feature points.

I detta arbete har ett koncept utvecklats för en flödesmätningsmetod med en intern sensorkropp samt bibehållen flödeshastighet. Denna mätmetod består av en sensorkropp i ett flödeshus där mätningen av flödet utförs med hjälp av pitotrörsberäkningar. Två olika lösningar presenteras i detta arbete, där skillnaderna grundar sig i utformningen av sensorkroppen. Sensorkroppens tvärsnitt är liknande för båda lösningarna. Den ena lösningen är rotationssymmetrisk i centrum av röret medan den andra går från vägg till vägg centrerat i röret. För att åstadkomma bibehållen flödeshastighet så utfördes beräkningar för att modellera flödeshuset, så att flödets tvärsnittsarea motsvarade arean i röret utan sensorkropp. I dessa beräkningar ingick även att kompensera för ökade solida ytor, då dessa ytor skapar gränsskikt där flödets hastighet sänks. Jämförelser mellan arbetets genererade koncept och uppdragsgivarens nuvarande produkter utfördes. Jämförelsen resulterade i flera områden där arbetets koncept skulle kunna komplettera redan befintliga produkter. / In this project a concept for flow measurement has been developed, where there is an internal sensor body as well as a constant flow speed. This measurement method consists of a sensor body in a flow housing where the flow measurement is done using conventional pitot tube calculations. Two different solutions are presented in this work, the differences between the two solutions are based on the design of the sensor body. The cross-section of the sensor body is similar for both solutions, but one solution is rotationally symmetrical while the other goes from wall to wall. Both sensor bodies are centered in the tube. To accomplish continuous flow speed, calculations were made to model the flow housing, so the cross-sectional area of the flow corresponded to the area of the tube without the sensor body. In these calculations a compensation factor for increased solid surface area were included, as this area creates a boundary layer that lowers the flow speed and changes based on the design of the sensor body. Comparisons between the concept in this project and the commissioner's current products were made. This comparison resulted in several areas where this projects concept could complement existing products.