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Hot tearing is a common and severe defect encountered in alloy castings and perhaps the pivotal issue defining an alloy's castability. Once it occurs, the casting has to be repaired or scraped, resulting in significant loss. Over the years many theories and models have been proposed and accordingly many tests have been developed. Unfortunately many of the tests that have been proposed are qualitative in nature; meanwhile, many of the prediction models are not satisfactory as they lack quantitative information, data and knowledge base. The need exists for a reliable and robust quantitative test to evaluate/characterize hot tearing in cast alloys. This work focused on developing an advanced test method and using it to study hot tearing in cast aluminum alloys. The objectives were to: 1) develop a reliable experimental methodology/setup to quantitatively measure and characterize hot tearing; and 2) quantify the mechanistic contributions of the process variables and investigate their effects on hot tearing tendency. The team at MPI in USA and CANMET-MTL in Canada has collaborated and developed such a testing setup. It consists mainly of a constrained rod mold and the load/displacement and temperature measuring system, which gives quantitative, simultaneous measurements of the real-time contraction force/displacement and temperature during solidification of casting. The data provide information about hot tearing formation and solidification characteristics, from which their quantitative relations are derived. Quantitative information such as tensile coherency, incipient crack refilling, crack initiation and propagation can be obtained. The method proves to be repeatable and reliable and has been used for studying the effects of various parameters (mold temperature, pouring temperature and grain refinement) on hot tearing of different cast aluminum alloys. In scientific sense this method can be used to study and reveal the nature of the hot tearing, for industry practice it provides a tool for production control. Moreover, the quantitative data and fundamental knowledge gained in this thesis can be used for validating and improving the existing hot tearing models.

Master of Science / Department of Mechanical and Nuclear Engineering / Kevin Lease / Over the past several years the crack tip opening angle (CTOA) has been identified as one of the key fracture parameters to characterize low constraint stable tearing and instability in structural metallic alloys. This document presents the results of experimental stable tearing characterizations. Characterization methods include optical microscopy and marker band measurements of crack front tunneling. Specific attention is given to the measurement methods used, and also the correlation between CTOA and Delta-5. The effect of tunneling and comparisons with computational results are discussed, and the effect of material and measurement method on CTOA is observed and a clear relationship is seen. Preliminary work on future studies into internal features and behavior is also presented.

This research is to develop an auto optical inspection system for surface mount device light emitting diodes. The principal purpose is to inspect SMD LED for 2D defects which are mixed-material and resin-tearing and for3D defect which is tombstone. In terms with mixed-material inspection, using the count of gradient operator to recognize LED chip. The false alarm rate is 4.29% and misdetection rate is 7.19%. It successfully detects defects with accuracy up to 94.24%. The average computation time is 12.97 ms. In terms of resin-tearing inspection, the research uses the gray scale correlation for SMD LED image registration. The false alarm rate is 5.15% and misdetection rate is 11.34%. The accuracy is up to 91.75%. The average computation time is 10.95 ms. 3D defect continues to use 2D view finder. The advantage of this structure is simple and cost-saving. The investigation which is inspected by the 3D system, comparing with real situation, the average measurement deviation is 4.51%. The average computation time is 8.05 ms. This propose of this system is not only to inspect 2D quickly, precisely and steady, but also to inspect 3D flaws which is hard to detect, and make the wole detective system more artificially-intelligent.

This document proposes modifications to an established cloth simulation algorithm to allow for stretch deformation and tearing of simulated cloth in computer-generated imagery. Previous research is presented, followed by the development of a cloth simulation system with the addition of tearing behavior. Several results are given that show off individual features and behaviors that this thesis models.

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Les modes de déchirement sont connus pour détériorer le confinement et limiter les performances dans les machines de fusion. Plusieurs études sur les modes de déchirements ont été menées, en incluant un degré croissant de complexité dans le modèle physique afin de mieux comprendre les observations expérimentales. Une de ces extensions est l'introduction d'une description du plasma comme un fluide à deux espèces, ions et électrons, dont les dynamiques sont fortement différentes. Un autre mécanisme physique connu pour être important est la courbure du champ magnétique non perturbé. Dans cette thèse, nous étudions les questions de la stabilité linéaire et de l'évolution non linéaire des îlots magnétiques, en présence de la courbure des lignes de champ et de la rotation diamagnétique, avec le code MHD non linéaire XTOR-2F, qui inclut le transport anisotrope de chaleur et les effets géométriques. Cette analyse est appliquée à une décharge entièrement non-inductive de Tore Supra. Ce mode d'opération est crucial pour démontrer la possibilité d'un fonctionnement continu sur un réacteur de type tokamak. Dans cette thèse, la possibilité d'une stabilisation complète des modes de déchirement par la rotation diamagnétique, en présence de la courbure toroidale des lignes de champ magnétique, est démontrée. Dans le domaine linéairement stable, le mode est métastable: le niveau de saturation dépend de la taille de l'îlot initial. Dans le domaine non linéaire, la saturation de l'îlot est fortement réduite par la rotation diamagnétique et par le nombre de Lundquist. La question de l'extrapolation des résultats obtenus vers la future generation de machines de fusion est également abordée / Tearing modes are known to deteriorate the confinement and limit plasma performance in fusion devices. Various studies of this mode have been performed lately including an increasing level of complexity in the physical description which is required for understanding of experimental observations. One of such extensions is the introduction of diamagnetic rotation into the system. Another physical mechanisms known to be important for tearing mode dynamics is the curvature of unperturbed magnetic field lines and neoclassical physics. In this thesis we investigate the issues of linear stability of the tearing modes in a presence of both curvature and diamagnetic rotation using the non linear full-MHD toroidal code XTOR-2F, which includes anisotropic heat transport, diamagnetic and geometrical effects. This analysis is applied to one of the fully non-inductive discharges on Tore-Supra. Such experiments are crucially important to demonstrate reactor scale steady state operation for the tokamak. In this thesis, the possibility of full linear stabilization of the tearing modes by diamagnetic rotation in the presence of toroidal curvature is shown. In the linearly stable domain, the mode is metastable: saturation level depends on the seed island size. In the non linear regime, the saturation of n=1, m=2 mode is found to be strongly reduced by diamagnetic rotation and by Lundquist number. The question of extrapolation of the obtained results towards future generation of fusion devices is also addressed. In particular, for ITER size machines, the toroidal curvature is expected to be more important due to higher performance factor β.

Ductile plastic hinge zones in beams of reinforced concrete frames are known to incur extensive damage and elongate. This ‘beam elongation’ can inflict serious damage to adjacent floor diaphragms, raising concerns of life safety. In light of this, the slotted reinforced concrete beam was investigated as a promising non-tearing floor substitute for conventional design. It consists of a conventional reinforced concrete beam, modified with a narrow vertical slot adjacent to the column face, running approximately three-quarters of the beam depth. Seismic rotations occur about the remaining concrete “top-hinge”, such that deformations are concentrated in the bottom bars of the beam, away from the floor slab, and beam elongation is minimised. The inclusion of the slot raised several design issues which needed to be addressed. These were the shear transfer across the top-hinge, buckling of bottom longitudinal reinforcement, low cycle fatigue, bond anchorage of reinforcement in interior joints, interior joint design, detailing with floor units and beam torsion resulting from eccentric floor gravity loads. These issues were conceptually investigated in this project. It was found that most issues could be resolved by providing additional reinforcement and/or specifying alternative detailing. As part of the experimental investigation, quasi-static cyclic tests were performed on in-plane beam-column joint subassemblies. Specimens tested included exterior and interior joint subassemblies with slotted-beams and a conventional exterior joint as a benchmark. This was followed by a test on a slotted-beam interior joint subassembly with precast floor units and imposed gravity load. Experimental tests revealed significant reductions in damage to both the beam and floor when compared to conventional beams. Issues of bar buckling, bond-slip and altered joint behaviour were also highlighted, but were resolved in the final test. A simple analytical procedure to predict the moment-rotation response of slotted-beams was developed and verified with experimental results. This was used to perform sensitivity studies to determine appropriate limits for the concrete top-hinge depth, top-to-bottom reinforcement ratio and depth of diagonal shear reinforcement. For the numerical investigation, a multi-spring model was developed to represent the flexural response of slotted-beams. This was verified with experimental tests and implemented into a five-storey, three-bay frame for earthquake time history analyses. To provide a benchmark, a conventional frame was also setup using the plastic hinge element developed by Peng (2009). Time history analyses showed that the slotted-beam frame response was very similar to the response of a conventional frame. Due to greater hysteretic damping, there was a slight reduction in the average interstorey drift and lateral displacement envelopes. The slotted-beam frame also exhibited 40% smaller residual drifts than the conventional frame. The research carried out in this thesis showed slotted reinforced concrete beams to be an effective non-tearing floor solution, which could provide a simple and practical substitute for conventional reinforced concrete design.