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The problem of this study is (1) to study the objectives and trends of general education, and (2) to study the needs of sheet metal industries in Dallas, Texas, in order to determine what the trends should be for a course of sheet metal work at N. R. Crozier Technical High School.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 162-168). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 162-168). Also available on the Internet.

Le vrillage est un mode de retour élastique particulier, qui se produit suite à la mise en forme par emboutissage de pièces allongées, à savoir dont une des dimensions est grande devant les deux autres. Le vrillage est caractérisé par la torsion de la pièce autour d’un axe parallèle à la plus grande dimension. D’un point de vue expérimental, le vrillage représente un véritable défi, du fait de la grande dimension, de l’ordre du mètre, des pièces industrielles et de la grande dispersion des valeurs caractéristiques de vrillage obtenues pour un même procédé et un même matériau. En conséquence, l’étude du vrillage en utilisant une échelle réduite sur l’ensemble des dimensions outils et pièce est retenue pour ce travail de thèse, avec un intérêt particulier pour l’influence de l’alignement tôle/outils sur l’intensité du vrillage.L’objectif général de ce travail de thèse est l’étude expérimentale et numérique du vrillage de pièces en forme de U, à partir de flans de longueur 100 mm et d’épaisseur 0,15 mm. Une première partie concerne la caractérisation et modélisation du comportement mécanique du matériau, un acier inoxydable. Des essais mécaniques de traction et cisaillement simple ont été réalisés, avec une mesure locale sans contact du champ de déformation. L’écrouissage ainsi que l’évolution de la pente à la décharge ont été caractérisés, et les paramètres d’un modèle élasto-plastique avec écrouissage mixte et dépendance du module d’Young avec la déformation plastique équivalente ont été identifiés à partir de ces essais.Afin de constituer une base expérimentale sur le vrillage, un dispositif spécifique a été conçu et usiné dans le cadre de cette thèse. Des essais d’emboutissage de flans rectangulaires, de dimensions 100 x 28 mm2, pour atteindre une forme de U de profondeur 7 mm, ont été réalisés. L’alignement de l’éprouvette avec le poinçon et la matrice a été particulièrement contrôlé et deux orientations ont été étudiées : l’éprouvette est soit alignée avec le poinçon, soit désalignée de 2° par rapport à son centre. La forme finale des éprouvettes a été mesurée avec un scanner laser. Le vrillage est caractérisé par le rapport de l’angle entre le fond de deux sections extrêmes sur leur distance respective. Un vrillage de 11°.m-1 a été mesuré pour les éprouvettes désalignées, tandis que pour les éprouvettes alignées, aucun vrillage significatif n’a été obtenu. L’étude des sections transversales de l’éprouvette montre une corrélation entre l’asymétrie du retour élastique causée par l’asymétrie de la géométrie de l’éprouvette, dans le cas désaligné, et le vrillage. Le glissement de l’éprouvette sous le poinçon au cours de l’essai affecte également le vrillage quelque soit l’orientation de l’éprouvette.Finalement, la simulation numérique de la mise en forme d’un flan en forme de U a été effectuée avec le code de calcul Abaqus®. Un solveur explicite est utilisé pour l’étape d’emboutissage et un solveur implicite pour le retour élastique. L’influence de la taille de maillage, ainsi que celle de la loi de comportement du matériau ont été étudiées. Les résultats de la simulation numérique sont alors confrontés aux résultats expérimentaux. / Twisting of metallic sheets is one particular mode of springback that occurs after drawing of elongated parts, i.e. with one dimension much larger than the two others. Twisting is usually characterized by the disorientation angle between the two end sections which turn around an axis parallel to the greatest dimension. From experimental point of view, twisting is very challenging because a lot of data were obtained on industrial-type parts, with one dimension of the order of the meter. These data are usually very dispersed and with the same process parameters, material and geometry, very different values for the twisting parameter can be obtained. As a consequence, the study of twisting phenomenon by using a reduced scale for all the dimensions of the tools and blank is retained in this work of. The influence of the blank alignment with the tools on the intensity of the twisting parameter was particular investigated.The objective of the thesis is the experimental and numerical study of the twisting of U-shaped part, obtained from stainless steel blanks with a length of 100 mm and thickness of 0.15 mm. The first part relates to the characterization and modeling of the material mechanical behavior. Conventional tests such as tension and simple shear were performed. The kinematic contribution to the hardening and the evolution of the loading-unloading slope with the plastic deformation were carried out. The parameters of an elastic-plastic model based on a mixed hardening and degradation of Young’s modulus with the equivalent plastic strain have been identified from these tests.In order to establish an experimental database for twisting, a dedicated device for drawing U-shaped elongated parts was designed and manufactured. Deep-drawing of rectangular blanks, of dimensions 100 x 28 mm2, to achieve a U-shape rail of 7 mm of depth was performed. Two different orientations of the part with respect to the tools were chosen: either aligned with the tools, or purposefully misaligned by 2°. The geometry of the part after springback was laser scanned. Twisting is characterized by the disorientation angle in-between the two end sections of the part over the distance. Several samples were drawn for each configuration, leading to the conclusion that almost no twisting occurs in the first case whereas a twisting parameter of 11°.m-1 corresponded to the second one. The analysis of the geometry of cross sections has shown a correlation between twisting and asymmetry of springback, like the opening of the U-shaped rail, caused by the asymmetry of the blank in the misaligned case. The sliding of the blank beneath the punch during the process also affects twisting whatever its orientation. Finally, finite element simulation of the drawing process, for the two configurations of the blank, within the explicit framework for drawing and implicit one for springback, were carried out using Abaqus® software. The influences of the mesh size as well as the material behavior law on the intensity of twisting parameter were studied. Numerical predictions were compared with experiments.

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Ng Yiu Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 110-114). / Abstracts in English and Chinese. / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Diagnosis concept based on thermal energy distribution --- p.6 / Chapter 1.1.1 --- A cup drawing example --- p.8 / Chapter 1.2 --- Need for 3D infrared thermal distribution measurement --- p.10 / Chapter 1.3 --- Outline of the Thesis --- p.11 / Chapter 2. --- Approach --- p.15 / Chapter 2.1 --- Similarity and extreme temperature analysis --- p.15 / Chapter 2.2 --- Thermodynamics for FEA in sheet metal stamping --- p.17 / Chapter 2.3 --- Acquisition of 3D thermal distribution --- p.20 / Chapter 3. --- Implementation of the Diagnosis System --- p.23 / Chapter 3.1 --- Thermograph acquisition --- p.23 / Chapter 3.2 --- Diagnosis system setup --- p.24 / Chapter 3.3 --- Perspective camera model --- p.25 / Chapter 3.4 --- System calibration --- p.27 / Chapter 3.4.1 --- LEDs calibration board --- p.27 / Chapter 3.4.2 --- Net-and-board calibration box --- p.29 / Chapter 3.5 --- Reconstruction algorithm --- p.33 / Chapter 3.6 --- Summary --- p.37 / Chapter 4. --- Consistency from Different Viewpoints --- p.38 / Chapter 4.1 --- Summary --- p.42 / Chapter 5. --- Visual Reconstruction of Objects --- p.44 / Chapter 5.1 --- Visual camera calibration --- p.45 / Chapter 5.2 --- Results --- p.49 / Chapter 5.2.1 --- "Cartoon model ""SiuSun""" --- p.49 / Chapter 5.2.2 --- Stamping disc --- p.51 / Chapter 5.3 --- Summary --- p.53 / Chapter 6. --- Thermal Distribution Reconstruction of Stamping Workpieces --- p.54 / Chapter 6.1 --- Infrared camera calibration --- p.54 / Chapter 6.2 --- Results --- p.57 / Chapter 6.2.1 --- Air conditioner cap --- p.57 / Chapter 6.2.2 --- Deep drawing cup --- p.59 / Chapter 6.2.3 --- Stamping cylinder from KS Factory --- p.61 / Chapter 6.3 --- Summary --- p.65 / Chapter 7. --- Infrared Camera on a Robotic Arm --- p.66 / Chapter 7.1 --- Robotic arm system setup --- p.67 / Chapter 7.2 --- System calibration --- p.68 / Chapter 7.3 --- Results --- p.77 / Chapter 7.3.1 --- Image sequence from horizontal viewpoints --- p.77 / Chapter 7.3.2 --- Image sequence from inclined viewpoints --- p.80 / Chapter 7.3.3 --- Image sequence from arbitrary viewpoints --- p.83 / Chapter 7.4 --- Comparison of the three different viewpoints --- p.85 / Chapter 7.5 --- Summary --- p.87 / Chapter 8. --- Compensation of Temperature Fade-out Problem --- p.88 / Chapter 8.1 --- Causes of temperature fade-out --- p.88 / Chapter 8.2 --- Solutions --- p.90 / Chapter 8.3 --- Summary --- p.91 / Chapter 9. --- Other Applications --- p.92 / Chapter 9.1 --- Automotive industry --- p.92 / Chapter 9.1.1 --- Background --- p.93 / Chapter 9.1.2 --- Experiment and result --- p.94 / Chapter 9.2 --- General heat transfer analysis --- p.97 / Chapter 9.3 --- Summary --- p.98 / Chapter 10. --- Conclusions --- p.99 / Chapter 10.1 --- Summary --- p.99 / Chapter 10.2 --- Future work --- p.104 / Chapter A. --- Transformation Matrices of the System --- p.106 / Bibliography --- p.110

In order to ensure the desirable performance of the machine, dynamic analysis of the machine is necessary. The analysis is conducted by the mean of computer simulation in consideration of applying a large impulsive force. This study validates the machine stability and accuracy. / In order to verify the new mechanics model, numerical and experimental studies are conducted using the new incremental punching system. The final shape and thickness distributions of parts are compared to verify the mechanics model. It is found that the model prediction fits the experiment result well. Forming parameters are also investigated. / In this research, a new incremental forming system based on incremental punching is designed and built. The system consists of a 3-axes CNC platform, a high speed hydraulic cylinder with a hemispherical forming tool, and a PC-based CNC control system. The hydraulic system provides the forming force to deform the sheet metal with constant stokes, while the CNC system positions the part. When forming a part, the forming tool punches the sheet metal along the given contour of the part punch by punch; when one layer of the part is completed, the forming tool moves down to the next layer; and the process is finished till all layers are completed. The CNC control system works with standard NC code, and hence, is easy to use. / ISMF uses a small generic tool to apply a sequence of operations along the given path to deform the sheet incrementally. These small deformations accumulate to form the final shape of the part. As a result, different parts can be made by the same setup. Despite of some 30 years of research and development, however, ISMF technology is still premature for industrial applications due to the following reasons: The accuracy of the part is limited; the surface roughness is poor; and the productivity is low. This motivates the presented research. / One of the keys to successful application of sheet metal forming is to be able to predict the deformation and the strain/stress of the part incurred during the forming process. Because of the complexity of the ISMF process, it is not possible to derive an analytical method. The alternative is to use Finite Element Analysis (FEA). However, based on our experience, it takes about one week to solve a simple case. A mechanics model is therefore developed. It consists of two steps. The first step is to computer the final shape: the initial geometric surface is obtained using the punch positions; then using the minimum energy principle, the virtual forces drive the nodes of geometric surface to their lowest energy positions, which gives the final shape of the forming part. The second step is to predict the strain and stress distributions. This is done using the inverse Finite Element Modeling (FEM). An in-house computer software is developed using MATLABRTM. / Stamping is one of the most commonly used manufacturing processes. Everyday, millions of parts are formed by this process. The conventional stamping is to form a part in one or several operations with a press machine and a set/sets of dies. It is very efficient but is not cost effective for small batch production parts and prototypes as the dies are expensive and time consuming to make. Recently, with the increasing demands for low-volume and customer-made products, a die-less forming method, Incremental Sheet Metal Forming (ISMF), has become one of the leading R&D topics in the industry. / To evaluate the capability of the presented ISMF process, the formability is studied by the means of theory and experiment. A modified M-K model is proposed for predicting the forming limit of the formed part which is undergoing a very complicated strain path. The maximum forming angle is also investigated by experiments. / Luo, Yuanxin. / Adviser: Ruxu Du. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 121-133). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Member: Rhett Mayor; Committee Member: Shreyes Melkote; Committee Member: Steven Danyluk. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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