Manufacturing processes inevitably induce a state of residual stress into materials and products. These residual stresses pose a large potential problem, in terms of dimensional stability and reduced fatigue life. Ideally, residual stresses should be reducible to low levels. There are three methods in general usage for the relaxation of these stresses, - Annealing, Shakedown and Vibratory Stress Relief (VSR). A previous study had suggested that vibration during and/or after welding may usefully modify residual stresses due to welding. This has been termed Vibratory Weld Conditioning (VWC). A comparative study of the methods is presented in section 1.4. The use of VSR, though widespread, has been adopted on a case-by-case basis, due to the lack of understanding of the processes at work. The purpose of this work was to investigate and validate the VSR/VWC method as a proposed alternative to the processes mentioned above. In order to do this a series of tests were devised in which the specimens were welded as a mechanism of stress induction. The residual stresses were measured before and after welding and vibration by means of a scanning X-ray diffractometer. In Chapter 1, the study of Residual Stress (source, formation etc), Welding Metallurgy and a comparison of VSR/VWC with other treatment methods are presented. In Chapter 2, a detailed review of literature is presented, where the accessible literature on VSR/VWC to date are included. In Chapter 3, the theoretical background of Modal Analysis, the Measurement of Dynamic Induced Stress and Measurement of Residual Stressesis discussed. In Chapter 4, the FE analysis of different structures is presented. In the FE analysis, different properties of the structures were determined using the FE model to aid the VSR/VWC study. The experimental investigations are presented in Chapter 5, which is divided into the following parts: Modal Analysis (experimental), Calibration of the X-ray measurements, VSR/VWC treatments, Cryogenic treatment, Fatigue Test and Metallurgical Investigation of VSR/VWC treated specimens. At the outset of the experimental work, the calibration of the X-ray diffractometer was carried out. After calibration of the X-ray and the X-ray Elastic Constant the error band of the diffractometer was significantly reduced. The practical modal analysis of the "8" frame was carried out to determine the modal characteristics of the frame to aid the VSR investigation of the frame. The VSR/VWC treatments are divided into "during welding" and "post weld" treatments and are presented in 10 different experiments. First, the "during welding" treatments were carried out. Investigation was started with application of tensile and compressive static stress to the specimens during welding and cooling. It was observed that the tensile induced stress decreased, and compressive induced stress increased the residual stresses. Rigid body motion (RBM) vibration showed no effect on the residual stresses. The cantilever beam test of the flexural vibration test showed some important characteristics, where the longitudinal residual stresses were found to decrease with application of small-induced stress. An increase in applied stress or time of vibration did not cause any more reduction. The transverse residual stresses increased with application of small-induced stresses. With increase in the applied stress the residual stresses decreased. High frequency vibration in both RBM and flexural vibration was found to be ineffective in reducing the residual stresses. The flexural vibration of the Four-Roller Supported beam showed a very confusing result, where no particular trend of the residual stresses was found. The combined mode of vibration (longitudinal and flexural) treatment showed no effect on residual stresses. The "post weld" treatment of the specimens showed a significant reduction in the residual stresses, where the reduction in the residual stresses were found to be a function of applied stress, while the vibration time effect was found to be negligible. A complex shape of reduction in the residual stresses were found along the width of the specimens, which made it impossible to develop any plastic flow model for the reduction in the residual stresses. Torsional test revealed a very important property of the residual stresses, where the residual stresses were found to decrease by a significant amount with application of very small induced stress. High induced stress only redistributed the residual stresses. Cryogenic treatment caused no reduction in the residual stresses. Contrarily the same specimen showed a significant reduction after VSR treatment. The fatigue test showed an increased fatigue life of the VSR treated specimens, while the thermally treated specimens showed a decreased fatigue life. The vibrated specimens showed highly oriented ferrite crystals in directions with Miller [111] to the stress axis. The hardness of the VSR treated specimens was found to increase significantly in comparison to the unvibrated specimens.

Class of 2010 Abstract / OBJECTIVES: To determine the perceived level of stress pharmacy students experience related to academics and the methods they use to relieve that stress. METHODS: This was a descriptive cross-­‐sectional study. Questionnaires were administered to first, second, and third year University of Arizona College of Pharmacy students during regularly scheduled class time. Data on perceived level of stress, sources of stress, and methods of relieving stress were collected and analyzed. Data on average hours worked per week, marital status, number of children, age, gender, and number of professional organizations involved in were also collected. RESULTS: The stress survey was completed by a total of 182 students at the College of Pharmacy. The overall stress score was highest in the second year students, although the total score was relatively low (total score 18.7; p=0.04). The four items that resulted in the highest stress scores were exams and/or grades (stress score ≥ 2.1), amount of class material (stress score ≥ 1.8), financial responsibilities (stress score ≥ 1.8) and lack of free time (stress score ≥ 1.6). Stressful situations that the students felt the most during the semester were thinking about the things that they had to accomplish (score ≥ 3.2) and having to control the way they spend their time (score ≥ 2.6). Common stress relievers were spending time with family, friends and pets ( ≥ 27%), watching television or movies ( ≥ 22%) and exercising ( ≥ 17%). Of those students who exercised, >44% felt it helped relieve stress very much. CONCLUSIONS: Little difference in levels of stress was observed between the classes. Based on the results, pharmacy students at the University of Arizona do not appear to be excessively stressed. Spending time with family/friends/pets, watching TV/DVDs, and exercising were the most common ways of relieving stress.

Approved for public release; distribution is unlimited / The US Navy is currently developing a new family of high-strength , low-alloy steels which derive a significant portion of their strength from copper precipitation. These highly weldable steels require little or no preheat. resulting in substantial cost savings. The first of these steels. HSLA-80, has been certified for ship construction, but recent studies have indicated some susceptibility to stress relief cracking in weldments. HSLA-100, a modification of HSLA-80, is now being considered for several higher-strength naval structures. Stress-relief cracking has not been studied previously in this steel and is the subject of investigation in this work. The steel weldments were loaded below their yield strength, heated to temperatures of 550°-650° C, and permitted to stress relieve for one hour. At all temperatures, the steel exhibited susceptibility to stress relief cracking in certain stress ranges. Optical and scanning electron microscopy exhibited intergranular cracking which always traversed the coarse-grained region of the heat-affected zone. Auger and transmission electron microscopy indicated high concentrations of alloying elements at the grain boundaries. Stress-relief cracking was associated with the diffusion of alloying elements to the prior austenite grain boundaries. / http://archive.org/details/stressreliefcrac00mcnu / Captain, Canadian Forces

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The trend to high I/O density, performance and miniaturization at low cost is driving the industry towards shrinking interposer design rules, requiring a new set of packaging technologies. Low-CTE packages from silicon, glass and low-CTE organic substrates enable high interconnection density, high reliability and integration of system components. However, the large CTE mismatch between the package and the board presents reliability challenges for the board-level interconnections. Novel stress-relief structures that can meet reliability requirements along with electrical performance while meeting the cost constraints are needed to address these challenges. This thesis focuses on a comprehensive methodology starting with modeling, design, fabrication and characterization to validate such stress-relief structures. This study specifically explores SMT-compatible stress-relief microwire arrays in thin polymer carriers as a unique and low-cost solution for reliable board-level interconnections between large low-CTE packages and printed wiring boards. The microwire arrays are pre-fabricated in ultra-thin carriers using low-cost manufacturing processes such as laser vias and copper electroplating, which are then assembled in between the interposer and printed wiring board (PWB) as stress-relief interlayers. The microwire array results in dramatic reduction in solder stresses and strains, even with larger interposer sizes (20 mm × 20 mm), at finer pitch (400 microns), without the need for underfill. The parallel wire arrays result in low resistance and inductance, and therefore do not degrade the electrical performance. The scalability of the structures and the unique processes, from micro to nanowires, provides extendibility to finer pitch and larger package sizes. Finite element method (FEM) was used to study the reliability of the interconnections to provide guidelines for the test vehicle design. The models were built in 2.5D geometries to study the reliability of 400 µm-pitch interconnections with a 100 µm thick, 20 mm × 20 mm silicon package that was SMT-assembled onto an organic printed wiring board. The performance of the microwire array interconnection is compared to that of ball grid array (BGA) interconnections, in warpage, equivalent plastic strain and projected fatigue life. A unique set of materials and processes was used to demonstrate the low-cost fabrication of microwire arrays. Copper microwires with 12 µm diameter and 50 µm height were fabricated on both sides of a 50 µm thick, thermoplastic polymer carrier using dryfilm based photolithography and bottom-up electrolytic plating. The copper microwire interconnections were assembled between silicon interposer and FR-4 PWB through SMT-compatible process. Thermal mechanical reliability of the interconnections was characterized by thermal cycling test from -40°C to 125°C. The initial fatigue failure in the interconnections was identified at 700 cycles in the solder on the silicon package side, which is consistent with the modeling results. This study therefore demonstrated a highly-reliable and SMT-compatible solution for board-level interconnections between large low-CTE packages and printed wiring board.

The present study examined the experience of self-cutting, what stops adolescent girls from engaging in self-cutting, and what message adolescent girls who are self-cutting would want to send to other girls taking part in this behavior. Using an existential-phenomenological method of interviewing, adolescent girls were asked a serious of questions in order to gain insight into their thoughts, feelings, and beliefs about the experience of self-cutting. Each interview was tape recorded, transcribed, and thematized. The participants in this study were labeled co-researchers due to the significant role that they had in the completion of this study. The co-researchers consisted of six adolescent girls aged 15 to 18 years old. They all attended high schools within a large urban school district in Florida. Through a reduction of the data obtained during the interviews, five superordinate themes were discovered for the first research question, which examined the experience of self-cutting. The themes depicted the following experience. Before engaging in self-cutting, each co-researcher had "A Lot of Feelings" stemming from "A Big Event" that they needed to "Release." They chose cutting because "Nothing [else] Ever Worked" and the act of cutting made them "Numb" and feel "No Pain." Themes developed from the second research question, which examined what stops adolescent girls from self-cutting, included "Thinking About the People Who Care" or when "Thinking About the Consequences" of cutting. If they could send a message to other girls who are cutting, the co-researchers in this study would say "Don't Do It." The co-researchers were able to articulate other coping strategies to serve the same function as cutting but sometimes refused to implement them. Results of this study support the findings of previous research.

Made available in DSpace on 2014-06-11T19:27:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-08-12Bitstream added on 2014-06-13T19:34:58Z : No. of bitstreams: 1 santos_ch_me_guara.pdf: 2207083 bytes, checksum: 6c810376924fcd84cb5a78acf9dd1896 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A estampagem de chapas metálicas é importante e se destaca entre os processos de conformação, pois, é possível de se obter vários produtos com alta produtividade e baixo custo. No entanto, como todo processo de conformação pode haver alguns inconvenientes, como as tensões residuais, que são geradas devido ao aumento da resistência mecânica do material resultante da deformação plástica a frio ou devido à geometria complexa da peça, com regiões de tração e compressão. Algumas medidas são realizadas dentro da área fabril para minimizar o problema e assim as peças irem para a etapa seguinte de conformação. Uma delas é a realização de tratamento térmico de alívio das tensões residuais de forma manual. O problema é que esse processo não garante nenhum controle da microestrutura e também não há garantia que as tensões foram aliviadas e como consequência peças são sucateadas na etapa seguinte de conformação, acarretando um aumento maior dos custos de fabricação. Neste trabalho foi realizado um estudo do alívio das tensões residuais através de vibrações mecânicas abaixo da frequência de ressonância em uma peça estampada a frio. O objetivo deste trabalho é avaliar os efeitos das vibrações mecânicas abaixo da frequência de ressonância no alívio das tensões residuais, de tal forma que possa ser uma opção ao tratamento térmico. Os resultados mostram que ouve redução nas tensões residuais, porém novos estudos devem ser realizados para garantir a eficácia deste processo / The stamping of sheet metal is important and stands out among the forming processes, therefore it is possible to obtain various products with high productivity and low cost, however, the whole process of conformation can bring some drawbacks, such as residual stresses, that are generated due the rigidity of the material against cold plastic deformation or due the geometry complex of the piece, with areas on tension and compression. Some processes are carried out within the factory area to minimize the problem and so the pieces go to the next step of forming, for instance perform heat treatment relief residual stresses. The problem is that this process does not guarantee any control of the microstructure and also there is not guarantee that the tensions were reduced and failure pieces in the next step of conformation, resulting in a greater increase in manufacturing costs. In this paper has been studied relief residual stress by mechanical vibrations, with carry out of treatment relief from vibrations below the resonant frequency in component cold drawned. The objective of this study is to evaluate the effects of mechanical vibration below the resonant frequency to relieve residual stresses, so that might be an option to heat treatment. The results show a reduction in residual stress; however, we have to compare them with other treatments for which they can ensure the effectiveness of mechanical vibrations

Made available in DSpace on 2014-06-11T19:28:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-08Bitstream added on 2014-06-13T20:58:36Z : No. of bitstreams: 1 silva_bm_me_guara.pdf: 2145639 bytes, checksum: 25fd5bf45355d72a1491c88dce260ad5 (MD5) / Universidade Estadual Paulista (UNESP) / A construção de uma turbina hidráulica consiste, em linhas gerais, de montagem por solda dos vários componentes da estrutura. As tensões residuais em junta soldada são de natureza complexa envolvendo fenômenos mecânicos e metalúrgicos. Vias de regra, essas tensões são aliviadas e, no caso particular de caixa espiral de turbina hidráulica, geralmente são feitos por processo mecânico (pressão hidrostática), não havendo inspeção para controlar o alívio total ou parcial das tensões. Nesta pesquisa foram analisadas as tensões existentes nas soldas de uma caixa espiral, que é à parte da turbina fabricada de chapas de aço carbono calandradas e soldadas, onde o alívio destas tensões residuais procedeu-se pelo processo mecânico. Foram feitas inspeções por medidas de tensões residuais através do método de difração de raios-X. Os resultados mostraram um comportamento não uniforme da distribuição de tensões, e em algumas soldas, houve reversão dos estados de tensões. Portanto, o alívio de tensões produzido pelo ensaio mecânico proposto (pressão hidrostática) mostrou que é possível alterar o estado de tensão das soldas para que sejam aliviadas a níveis admissíveis. / The construction of a hydraulic turbine consists, in general lines, of assembly for it welds of the several components of the structure. The residual stresses in the welded joints are of complex nature involving mechanical and metallurgists phenomena. Rule roads, those stresses are relived and, in the case peculiar of hydraulic turbine, they are generally done by mechanical process (hydrostatic pressure), not having inspection to control of total or partial relief of the stresses. In this research were analyses the residual stresses in the welds joints of spiral case, that is to the part of the manufactured turbine of carbon steel plates, cut, calendared and welded, and the stresses relief was proceeded by the mechanical process. They were made inspections by measures of residual stresses by X-ray diffraction method. The results showed a behavior non-uniform of the stresses distributions, and in some welds, there were a reversion of the stresses states. Therefore, the relief of stresses produced by the proposed mechanical test (hydrostatic pressure) it showed that is possible to alter the stresses state of the welds so that they are relieved at acceptable levels.

abstract: The wide-scale use of green technologies such as electric vehicles has been slowed due to insufficient means of storing enough portable energy. Therefore it is critical that efficient storage mediums be developed in order to transform abundant renewable energy into an on-demand source of power. Lithium (Li) ion batteries are seeing a stream of improvements as they are introduced into many consumer electronics, electric vehicles and aircraft, and medical devices. Li-ion batteries are well suited for portable applications because of their high energy-to-weight ratios, high energy densities, and reasonable life cycles. Current research into Li-ion batteries is focused on enhancing its energy density, and by changing the electrode materials, greater energy capacities can be realized. Silicon (Si) is a very attractive option because it has the highest known theoretical charge capacity. Current Si anodes, however, suffer from early capacity fading caused by pulverization from the stresses induced by large volumetric changes that occur during charging and discharging. An innovative system aimed at resolving this issue is being developed. This system incorporates a thin Si film bonded to an elastomeric substrate which is intended to provide the desired stress relief. Non-linear finite element simulations have shown that a significant amount of deformation can be accommodated until a critical threshold of Li concentration is reached; beyond which buckling is induced and a wavy structure appears. When compared to a similar system using rigid substrates where no buckling occurs, the stress is reduced by an order of magnitude, significantly prolonging the life of the Si anode. Thus the stress can be released at high Li-ion diffusion induced strains by buckling the Si thin film. Several aspects of this anode system have been analyzed including studying the effects of charge rate and thin film plasticity, and the results are compared with preliminary empirical measurements to show great promise. This study serves as the basis for a radical resolution to one of the few remaining barriers left in the development of high performing Si based electrodes for Li-ion batteries. / Dissertation/Thesis / Appendix H - Movies (zipped) / M.S. Mechanical Engineering 2011