Добірка наукової літератури з теми "Constitutive relations for joint modeling in dams"

Purpose – The purpose of this paper is to propose a computational approach in order to help establish the effect of various self-piercing rivet (SPR) process and material parameters on the quality and the mechanical performance of the resulting SPR joints. Design/methodology/approach – Toward that end, a sequence of three distinct computational analyses is developed. These analyses include: (a) finite-element modeling and simulations of the SPR process; (b) determination of the mechanical properties of the resulting SPR joints through the use of three-dimensional, continuum finite-element-based numerical simulations of various mechanical tests performed on the SPR joints; and (c) determination, parameterization and validation of the constitutive relations for the simplified SPR connectors, using the results obtained in (b) and the available experimental results. The availability of such connectors is mandatory in large-scale computational analyses of whole-vehicle crash or even in simulations of vehicle component manufacturing, e.g. car-body electro-coat paint-baking process. In such simulations, explicit three-dimensional representation of all SPR joints is associated with a prohibitive computational cost. Findings – It is found that the approach developed in the present work can be used, within an engineering optimization procedure, to adjust the SPR process and material parameters (design variables) in order to obtain a desired combination of the SPR-joint mechanical properties (objective function). Originality/value – To the authors’ knowledge, the present work is the first public-domain report of the comprehensive modeling and simulations including: self-piercing process; virtual mechanical testing of the SPR joints; and derivation of the constitutive relations for the SPR connector elements.

A numerical decomposition technique, which has resulted from a linking between joint-geometry modeling and generation schemes, and a distinct element code (UDEC), is used to study the effect of joint-geometry parameters of finite-size joints on the deformability properties of jointed rock at the two-dimensional (2D) level. The influence of joint-geometry parameters such as joint density, ratio of joint size to block size, and joint orientation on the deformability of jointed rock is shown. Relations are established between deformability properties of jointed rock and fracture-tensor parameters. An incrementally linear elastic, anisotropic constitutive model is developed to represent the prefailure mechanical behaviour of jointed rock at the 2D level. This constitutive model has captured the anisotropic, scale-dependent behaviour of jointed rock. In this model, the effect of the joint-geometry network in the rock mass is incorporated in terms of fracture-tensor components. Some insight is given related to estimation of representative elementary volumes for deformability properties of jointed rock. Key words : rock masses, deformability, distinct element method, fracture tensor, anisotropy, scale effects.

In this work, a computational approach is proposed in order to help establish the effect of various flow-drilling screw process and material parameters on the quality and the mechanical performance of the resulting flow-drilling screw joints. Toward that end, a sequence of three distinct computational analyses is developed. These analyses include the following: (a) finite element modeling and simulations of the flow-drilling screw process; (b) determination of the mechanical properties of the resulting flow-drilling screw joints through the use of three-dimensional, continuum finite element–based numerical simulations of various mechanical tests performed on the flow-drilling screw joints and (c) determination, parameterization and validation of the constitutive relations for the simplified flow-drilling screw connectors, using the results obtained in (b) and the available experimental results. The availability of such connectors is mandatory in large-scale computational analyses of whole-vehicle crash or even in simulations of vehicle component manufacturing, for example, car-body electro-coat paint-baking process. In such simulations, explicit three-dimensional representation of all flow-drilling screw joints is associated with a prohibitive computational cost. The approach developed in this work can be used, within an engineering-optimization procedure, to adjust the flow-drilling screw process and material parameters (design variables) in order to obtain a desired combination of the flow-drilling screw joint mechanical properties (objective function).

В статье обсуждаются проблемы постановка краевых задач при моделировании процессов аддитивного производства 3D материала, при учете наличия в нем дополнительных выделенных направлений (выкладки волокон в тканых материалах, арматуры в бетонных конструкциях, биоволокон в мышечной ткани и т.д.). Выводится общая форма тензорного соотношения на поверхности наращивания, при учете дополнительного выделенного направления. Определяется необходимая система независимых аргументов определяющей тензорной функции на поверхности наращивания в рассматриваемом случае. Определяется полный набор совместных рациональных инвариантов тензора напряжений и характерных директоров. Дается инвариантно-полная формулировка определяющих соотношений на поверхности наращивания. Предложены постановки краевых задач, моделирующих процессы синтеза тканых 3D материалов. Полученные дифференциальные ограничения конкретизируются для ортогональных систем координат, учитывающих геометрию процесса наращивания. The article discusses the problem of boundary value problems in models of the additive production processes of a 3D material, taking into account the presence of additional selected directions in it (laying out fibers in woven materials, reinforcement in concrete structures, biofibers in muscle tissue, etc.). The general form of the tensor relation on the growing surface is shown, taking into account the additional selected direction. The necessary system of independent arguments of the constitutive tensor function on the growing surface in the considered case is determined. A complete set of joint rational invariants of the stress tensor and characteristic directors is determined. An invariant-complete formulation of the constitutive relations on the growing surface is given. The formulation of boundary value problems that simulate the processes of synthesis of woven 3D materials are proposed. The resulting differential constraints are specified for orthogonal coordinate systems taking account of the geometry of the growing process.

This paper presents a nonlinear finite element analysis of non-seismically detailed RC beam column connections under reversed cyclic load. The test of half-scale nonductile reinforced concrete beam-column joints was conducted. The tested specimens represented those of the actual mid-rise reinforced concrete frame buildings designed according to the non-seismic provisions of the ACI building code. The test results show that specimens representing small and medium column tributary area failed in brittle joint shear while specimen representing large column tributary area failed by ductile flexure though no ductile reinforcement details were provided. The nonlinear finite element analysis was applied to simulate the behavior of the specimens. The finite element analysis employs the smeared crack approach for modeling beam, column and joint, and employs the discrete crack approach for modeling the interface between beam and joint face. The nonlinear constitutive models of reinforced concrete elements consist of coupled tension-compression model to model normal force orthogonal and parallel to the crack and shear transfer model to capture the shear sliding mechanism. The FEM shows good comparison with test results in terms of load-displacement relations, hysteretic loops, cracking process and the failure mode of the tested specimens. The finite element analysis clarifies that the joint shear failure was caused by the collapse of principal diagonal concrete strut.

Purpose – The purpose of this paper is to propose a computational approach to establish the effect of various flow drilling screw (FS) process and material parameters on the quality and the mechanical performance of the resulting FS joints. Design/methodology/approach – Toward that end, a sequence of three distinct computational analyses is developed. These analyses include: (a) finite-element modeling and simulations of the FS process; (b) determination of the mechanical properties of the resulting FS joints through the use of three-dimensional, continuum finite-element-based numerical simulations of various mechanical tests performed on the FS joints; and (c) determination, parameterization and validation of the constitutive relations for the simplified FS connectors, using the results obtained in (b) and the available experimental results. The availability of such connectors is mandatory in large-scale computational analyses of whole-vehicle crash or even in simulations of vehicle component manufacturing, e.g. car-body electro-coat paint-baking process. In such simulations, explicit three-dimensional representation of all FS joints is associated with a prohibitive computational cost. Findings – Virtual testing of the shell components fastened using the joint connectors validated the ability of these line elements to realistically account for the strength, ductility and toughness of the three-dimensional FS joints. Originality/value – The approach developed in the present work can be used, within an engineering-optimization procedure, to adjust the FS process and material parameters (design variables) in order to obtain a desired combination of the FS-joint mechanical properties (objective function).

В статье обсуждаются формулировки определяющих дифференциальных ограничений на поверхности наращивания на случай моделирования процессов формирования 3D материала, характеризующегося дополнительными характерными директорами (направлениями выкладки волокон в тканых материалах, арматуры в бетонных конструкциях). Выведена общая форма тензорного соотношения на поверхности наращивания, при учете дополнительных выделенных направлений. Определить набор совместных рациональных инвариантов тензора напряжений и характерных директоров. Дана инвариантно-полная формулировка определяющих соотношений на поверхности наращивания. Полученные результаты могут быть использованы для постановки и решения краевых задач, моделирующих процессы синтеза тканых 3D материалов. The article discusses the formulation of the defining differential constraints on the buildup surface in the case of modeling the processes of forming a 3D material characterized by additional characteristic directors (directions of laying fibers in woven materials, reinforcement in concrete structures). The general form of the tensor relation on the growing surface is derived, taking into account the additional selected directions. Determine the set of joint rational invariants of the stress tensor and characteristic directors. An invariant-complete formulation of the constitutive relations on the surface of the build-up is given. The results obtained can be used to formulate and solve boundary value problems that simulate the processes of synthesis of woven 3D materials.

Abstract A general contact model for a lap joint interface based on non-Gaussian surfaces was proposed. The effect of surface topography parameters on microslip behavior in a lap joint interface was studied. Pearson system was applied to produce non-Gaussian surfaces. Combining the topographical-dependent Zhao–Maietta–Chang (ZMC) model with the physical-related Iwan model, the nonlinear constitutive relationship of a lap interface was constructed by using Masing hypothesis. Meanwhile, the probability density function of asperity heights of an infinitely smooth surface was mathematically proved to be a delta function, verifying that the calculated value of friction in the model conforms to the physical law. Gauss-Legendre quadrature was conducted to calculate contact relations of different Pearson distribution surfaces. Furthermore, numerical results of microslip loops under oscillating tangential forces were compared with the published experiments, indicating the present model considering non-Gaussian surfaces could agree well with the experiments.

Story spreads out through time the behaviors or bodies – the shapes – a self has been or will be, each replacing the one before. Hence a story has before and after, gain and loss. It goes somewhere…Moreover, shape or body is crucial, not incidental, to story. It carries story; it makes story visible; in a sense it is story. Shape (or visible body) is in space what story is in time. (Bynum, quoted in Garland Thomson, 113-114) Drawing on Goffman’s classic work on stigma, research documenting the existence of discrimination and bias against individuals classified as obese goes back five decades. Since Cahnman published “The Stigma of Obesity” in 1968, other researchers have well documented systematic and growing discrimination against fat people (cf. Puhl and Brownell; Puhl and Heuer; Puhl and Heuer; Fikkan and Rothblum). While weight-based stereotyping has a long history (Chang and Christakis; McPhail; Schwartz), contemporary forms of anti-fat stigma and discrimination must be understood within a social and economic context of neoliberal healthism. By neoliberal healthism (see Crawford; Crawford; Metzel and Kirkland), I refer to the set of discourses that suggest that humans are rational, self-determining actors who independently make their own best choices and are thus responsible for their life chances and health outcomes. In such a context, good health becomes associated with proper selfhood, and there are material and social consequences for those who either unwell or perceived to be unwell. While the greatest impacts of size-based discrimination are structural in nature, the interpersonal impacts are also significant. Because obesity is commonly represented (at least partially) as a matter of behavioral choices in public health, medicine, and media, to “remain fat” is to invite commentary from others that one is lacking in personal responsibility. Guthman suggests that this lack of empathy “also stems from the growing perception that obesity presents a social cost, made all the more tenable when the perception of health responsibility has been reversed from a welfare model” (1126). Because weight loss is commonly held to be a reasonable and feasible goal and yet is nearly impossible to maintain in practice (Kassierer and Angell; Mann et al.; Puhl and Heuer), fat people are “in effect, asked to do the impossible and then socially punished for failing” (Greenhalgh, 474). In this article, I explore how weight-based stigma shaped the decisions of bariatric patients to undergo weight loss surgery. In doing so, I underline the work that emotion does in circulating anti-fat stigma and in creating categories of subjects along lines of health and responsibility. As well, I highlight how fat bodies are lived and negotiated in space and place. I then explore ways in which participants take up notions of time, specifically in regard to risk, in discussing what brought them to the decision to have bariatric surgery. I conclude by arguing that it is a dynamic interaction between the material, social, emotional, discursive, and the temporal that produces not only fat embodiment, but fat subjectivity “failed”, and serves as an impetus for seeking bariatric surgery. Methods This article is based on 30 semi-structured interviews with American bariatric patients. At the time of the interview, individuals were between six months and 12 years out from surgery. After obtaining Intuitional Review Board approval, recruitment occurred through a snowball sample. All interviews were audio-taped with permission and verbatim interview transcripts were analyzed by means of a thematic analysis using Dedoose (www.dedoose.com). All names given in this article are pseudonyms. This work is part of a larger project that includes two additional interviews with bariatric surgeons as well as participant-observation research. Findings Navigating Anti-Fat Stigma In discussing what it was like to be fat, all but one of the individuals I interviewed discussed experiencing substantive size-based stigma and discrimination. Whether through overt comments, indirect remarks, dirty looks, open gawking, or being ignored and unrecognized, participants felt hurt, angry, and shamed by friends, family, coworkers, medical providers, and strangers on the street because of the size of their bodies. Several recalled being bullied and even physically assaulted by peers as children. Many described the experience of being fat or very fat as one of simultaneous hypervisibility and invisibility. One young woman, Kaia, said: “I absolutely was not treated like a person … . I was just like this object to people. Just this big, you know, thing. That’s how people treated me.” Nearly all of my participants described being told repeatedly by others, including medical professionals, that their inability to lose weight was effectively a failure of the will. They found these comments to be particularly hurtful because, in fact, they had spent years, even decades, trying to lose weight only to gain the weight back plus more. Some providers and family members seemed to take up the idea that shame could be a motivating force in weight loss. However, as research by Lewis et al.; Puhl and Huerer; and Schafer and Ferraro has demonstrated, the effect this had was the opposite of what was intended. Specifically, a number of the individuals I spoke with delayed care and avoided health-facilitating behaviors, like exercising, because of the discrimination they had experienced. Instead, they turned to health-harming practices, like crash dieting. Moreover, the internalization of shame and blame served to lower a sense of self-worth for many participants. And despite having a strong sense that something outside of personal behavior explained their escalating body weights, they deeply internalized messages about responsibility and self-control. Danielle, for instance, remarked: “Why could the one thing I want the most be so impossible for me to maintain?” It is important to highlight the work that emotion does in circulating such experiences of anti-fat stigma and discrimination. As Fraser et al have argued in their discussion on fat and emotion, the social, the emotional, and the corporeal cannot be separated. Drawing on Ahmed, they argue that strong emotions are neither interior psychological states that work between individuals nor societal states that impact individuals. Rather, emotions are constitutive of subjects and collectivities, (Ahmed; Fraser et al.). Negative emotions in particular, such as hate and fear, produce categories of people, by defining them as a common threat and, in the process, they also create categories of people who are deemed legitimate and those who are not. Thus following Fraser et al, it is possible to see that anti-fat hatred did more than just negatively impact the individuals I spoke with. Rather, it worked to produce, differentiate, and drive home categories of people along lines of health, weight, risk, responsibility, and worth. In this next section, I examine the ways in which anti-fat discrimination works at the interface of not only the discursive and the emotive, but the material as well. Big Bodies, Small Spaces When they discussed their previous lives as very fat people, all of the participants made reference to a social and built environment mismatch, or in Garland Thomson’s terms, a “misfit”. A misfit occurs “when the environment does not sustain the shape and function of the body that enters it” (594). Whereas the built environment offers a fit for the majority of bodies, Garland Thomson continues, it also creates misfits for minority forms of embodiment. While Garland Thomson’s analysis is particular to disability, I argue that it extends to fat embodiment as well. In discussing what it was like to navigate the world as fat, participants described both the physical and emotional pain entailed in living in bodies that did not fit and frequently discussed the ways in which leaving the house was always a potential, anxiety-filled problem. Whereas all of the participants I interviewed discussed such misfitting, it was notable that participants in the Greater New York City area (70% of the sample) spoke about this topic at length. Specifically, they made frequent and explicit mentions of the particular interface between their fat bodies and the Metropolitan Transit Authority (MTA), and the tightly packed spaces of the city itself. Greater New York City area participants frequently spoke of the shame and physical discomfort in having to stand on public transportation for fear that they would be openly disparaged for “taking up too much room.” Some mentioned that transit seats were made of molded plastic, indicating by design the amount of space a body should occupy. Because they knew they would require more space than what was allotted, these participants only took seats after calculating how crowded the subway or train car was and how crowded it would likely become. Notably, the decision to not take a seat was one that was made at a cost for some of the larger individuals who experienced joint pain. Many participants stated that the densely populated nature of New York City made navigating daily life very challenging. In Talia’s words, “More people, more obstacles, less space.” Participants described always having to be on guard, looking for the next obstacle. As Candice put it: “I would walk in some place and say, ‘Will I be able to fit? Will I be able to manoeuvre around these people and not bump into them?’ I was always self-conscious.” Although participants often found creative solutions to navigating the hostile environment of both the MTA and the city at large, they also identified an increasing sense of isolation that resulted from the physical discomfort and embarrassment of not fitting in. For instance, Talia rarely joined her partner and their friends on outings to movies or the theater because the seats were too tight. Similarly, Decenia would make excuses to her husband in order to avoid social situations outside of the home: “I’d say to my husband, ‘I don’t feel well, you go.’ But you know what? It was because I was afraid not to fit, you know?” The anticipatory scrutinizing described by these participants, and the anxieties it produced, echoes Kirkland’s contention that fat individuals use the technique of ‘scanning’ in order to navigate and manage hostile social and built environments. Scanning, she states, involves both literally rapidly looking over situations and places to determine accessibility, as well as a learned assessment and observation technique that allows fat people to anticipate how they will be received in new situations and new places. For my participants, worries about not fitting were more than just internal calculation. Rather, others made all too clear that fat bodies are not welcome. Nina recalled nasty looks she received from other subway riders when she attempted to sit down. Decenia described an experience on a crowded commuter train in which the woman next to her openly expressed annoyance and disgust that their thighs were touching. Talia recalled being aggressively handed a weight loss brochure by a fellow passenger. When asked to contrast their experiences living in New York City with having travelled or lived elsewhere, participants almost universally described the New York as a more difficult place to live for fat people. However, the experiences of three of the Latinas that I interviewed troubled this narrative. Katrina felt that the harassment she received in her country of origin, the Dominican Republic, was far worse than what she now experienced in the New York Metropolitan Area. Although Decenia detailed painful experiences of anti-fat stigma in New York City, she nevertheless described her life as relatively “easy” compared to what it was like in her home country of Brazil. And Denisa contrasted her neighbourhood of East Harlem with other parts of Manhattan: “In Harlem it's different. Everybody is really fat or plump – so you feel a bit more comfortable. Not everybody, but there's a mix. Downtown – there's no mix.” Collectively, their stories serve as a reminder (see Franko et al.; Grabe and Hyde) to be suspicious of over determined accounts that “Latino culture” is (or people of colour communities in general are), more accepting of larger bodies and more resistant to weight-based stigma and discrimination. Their comments also reflect arguments made by Colls, Grosz, and Garland Thomson, who have all pointed to the contingent nature between space and bodies. Colls argue that sizing is both a material and an emotional process – what size we take ourselves to be shifts in different physical and emotional contexts. Grosz suggests that there is a “mutually constitutive relationship between bodies and cities” – one that, I would add, is raced, classed, and gendered. Garland Thomson has described the relationship between bodies and space/place as “a dynamic encounter between world and flesh.” These encounters, she states, are always contingent and situated: “When the spatial and temporal context shifts, so does the fit, and with it meanings and consequences” (592). In this sense, fat is materialized differently in different contexts and in different scales – nation, state, city, neighbourhood – and the materialization of fatness is always entangled with raced, classed, and gendered social and political-economic relations. Nevertheless, it is possible to draw some structural commonalities between divergent parts of the Greater New York City Metropolitan Area. Specifically, a dense population, cramped physical spaces, inaccessible transportation and transportation funding cuts, social norms of fast paced life, and elite, raced, classed, and gendered norms of status and beauty work to materialize fatness in such a way that a ‘misfit’ is often the result for fat people who live and/or work in this area. And importantly, misfitting, as Garland Thomson argues, has consequences: it literally “casts out” when the “shape and function of … bodies comes into conflict with the shape and stuff of the built world” (594). This casting out produces some bodies as irrelevant to social and economic life, resulting in segregation and isolation. To misfit, she argues, is to be denied full citizenship. Responsibilising the Present Garland Thomson, discussing Bynum’s statement that “shape carries story”, argues the following: “the idea that shape carries story suggests … that material bodies are not only in the spaces of the world but that they are entwined with temporality as well” (596). In this section, I discuss how participants described their decisions to get weight loss surgery by making references to the need take responsibility for health now, in the present, in order to avoid further and future morbidity and mortality. Following Adams et al., I look at how the fat body is lived in a state of constant anticipation – “thinking and living toward the future” (246). All of the participants I spoke with described long histories of weight cycling. While many managed to lose weight, none were able to maintain this weight loss in the long term – a reality consistent with the medical fact that dieting does not produce durable results (Kassirer and Angell; Mann et al.; Puhl and Heuer). They experienced this inability as not only distressing, but terrifying, as they repeatedly regained the lost weight plus more. When participants discussed their decisions to have surgery, they highlighted concerns about weight related comorbidities and mobility limitations in their explanations. Consistent then with Boero, Lopez, and Wadden et al., the participants I spoke with did not seek out surgery in hopes of finding a permanent way to become thin, but rather a permanent way to become healthy and normal. Concerns about what is considered to be normative health, more than simply concerns about what is held to be an appropriate appearance, motivated their decisions. Significantly, for these participants the decision to have bariatric surgery was based on concerns about future morbidity (and mortality) at least as much, if not more so, than on concerns about a current state of ill health and impairment. Some individuals I spoke with were unquestionably suffering from multiple chronic and even life threatening illnesses and feared they would prematurely die from these conditions. Other participants, however, made the decision to have bariatric surgery despite the fact that they had no comorbidities whatsoever. Motivating their decisions was the fear that they would eventually develop them. Importantly, medial providers explicitly and repeatedly told all of these participants that lest they take drastic and immediate action, they would die. For example: Faith’s reproductive endocrinologist said: “you’re going to have diabetes by the time you’re 30; you’re going to have a stroke by the time you’re 40. And I can only hope that you can recover enough from your stroke that you’ll be able to take care of your family.” Several female participants were warned that without losing weight, they would either never become pregnant or they would die in childbirth. By contrast, participants stated that their bariatric surgeons were the first providers they had encountered to both assert that obesity was a medical condition outside of their control and to offer them a solution. Within an atmosphere in which obesity is held to be largely or entirely the result of behavioural choices, the bariatric profession thus positions itself as unique by offering both understanding and what it claims to be a durable treatment. Importantly, it would be a mistake to conclude that some bariatric patients needed surgery while others choose it for the wrong reasons. Regardless of their states of health at the time they made the decision to have surgery, the concerns that drove these patients to seek out these procedures were experienced as very real. Whether or not these concerns would have materialized as actual health conditions is unknown. Furthermore, bariatric patients should not be seen as having been duped or suffering from ‘false consciousness.’ Rather, they operate within a particular set of social, cultural, and political-economic conditions that suggest that good citizenship requires risk avoidance and personal health management. As these individuals experienced, there are material and social consequences for ‘failing’ to obtain normative conceptualizations of health. This set of conditions helps to produce a bariatric patient population that includes both those who were contending with serious health concerns and those who feared they would develop them. All bariatric patients operate within this set of conditions (as do medical providers) and make decisions regarding health (current, future, or both) by using the resources available to them. In her work on the temporalities of dieting, Coleman argues that rather than seeing dieting as a linear and progressive event, we might think of it instead a process that brings the future into the present as potential. Adams et al suggest concerns about potential futures, particularly in regard to health, are a defining characteristic of our time. They state: “The present is governed, at almost every scale, as if the future is what matters most. Anticipatory modes enable the production of possible futures that are lived and felt as inevitable in the present, rendering hope and fear as important political vectors” (249). The ability to act in the present based on potential future risks, they argue, has become a moral imperative and a marker of proper of citizenship. Importantly, however, our work to secure the ‘best possible future’ is never fully assured, as risks are constantly changing. The future is thus always uncertain. Acting responsibly in the present therefore requires “alertness and vigilance as normative affective states” (254). Importantly, these anticipations are not diagnostic, but productive. As Adams et al state, “the future arrives already formed in the present, as if the emergency has already happened…a ‘sense’ of the simultaneous uncertainty and inevitability of the future, usually manifest in entanglements of fear and hope” (250). It is in this light, then, that we might see the decision to have bariatric surgery. For these participants, their future weight-related morbidity and mortality had already arrived in the present and thus they felt they needed to act responsibly now, by undergoing what they had been told was the only durable medical intervention for obesity. The emotions of hope, fear, anxiety and I would suggest, hatred, were key in making these decisions. Conclusion Medical, public health, and media discourses frame obesity as an epidemic that threatens to bring untold financial disaster and escalating rates of morbidity and mortality upon the nation state and the world at large. As Fraser et al argue, strong emotions (such hatred, fear, anxiety, and hope), are at the centre of these discourses; they construct, circulate, and proliferate them. Moreover, they create categories of people who are deemed legitimate and categories of others who are not. In this context, the participants I spoke with were caught between a desire to have fatness understood as a medical condition needing intervention; the anti-fat attitudes of others, including providers, which held that obesity was a failure of the will and nothing more; their own internalization of these messages of personal responsibility for proper behavioural choices, and, the biologically intractable nature of fatness wherein dieting not only fails to reduce weight in the vast majority of cases but results, in the long term, in increased weight gain (Kassirer and Angell; Mann et al.; Puhl and Heuer). Widespread anxiety and embarrassment over and fear and hatred of fatness was something that the individuals I interviewed experienced directly and which signalled to them that they were less than human. Their desire for weight loss, therefore was partially a desire to become ‘normal.’ In Butler’s term, it was the desire for a ‘liveable life. ’A liveable life, for these participants, included a desire for a seamless fit with the built environment. The individuals I spoke with were never more ashamed of their fatness than when they experienced a ‘misfit’, in Garland Thomson’s terms, between their bodies and the material world. Moreover, feelings of shame over this disjuncture worked in tandem with a deeply felt, pressing sense that something must be done in the present to secure a better health future. The belief that bariatric surgery might finally provide a durable answer to obesity served as a strong motivating factor in their decisions to undergo bariatric surgery. By taking drastic action to lose weight, participants hoped to contest stigmatizing beliefs that their fat bodies reflected pathological interiors. Moreover, they sought to demonstrate responsibility and thus secure proper subjectivities and citizenship. In this sense, concerns, anxieties, and fears about health cannot be disentangled from the experience of anti-fat stigma and discrimination. Again, anti-fat bias, for these participants, was more than discursive: it operated through the circulation of emotion and was experienced in a very material sense. The decision to have weight loss surgery can thus be seen as occurring at the interface of emotion, flesh, space, place, and time, and in ways that are fundamentally shaped by the broader social context of neoliberal healthism. AcknowledgmentI am grateful to the anonymous reviewers of this article for their helpful feedback on earlier version. References Adams, Vincanne, Michelle Murphy, and Adele E. Clarke. “Anticipation: Technoscience, Life, Affect, Temporality.” Subjectivity 28.1 (2009): 246-265. Ahmed, Sara. “Affective Economies.” Social Text 22.2 (2004): 117-139 Boero, Natalie. Killer Fat: Media, Medicine, and Morals in the American "Obesity Epidemic". New Brunswick: Rutgers University Press, 2012. Butler, Judith. Undoing Gender. New York: Routledge, 2004. Bynum, Caroline Walker. 1999. Jefferson Lecture in the Humanities. National Endowment for the Humanities. Washington, DC, 1999. Cahnman, Werner J. “The Stigma of Obesity.” The Sociological Quarterly 9.3 (1968): 283-299. Chang, Virginia W., and Nicholas A. Christakis. “Medical Modeling of Obesity: A Transition from Action to Experience in a 20th Century American Medical Textbook.” Sociology of Health & Illness 24.2 (2002): 151-177. Coleman, Rebecca. “Dieting Temporalities: Interaction, Agency and the Measure of Online Weight Watching.” Time & Society 19.2 (2010): 265-285. Colls, Rachel. “‘Looking Alright, Feeling Alright:’ Emotions, Sizing, and the Geographies of Women’s Experience of Clothing Consumption.” Social & Cultural Geography 5.4 (2004): 583-596. Crawford, Robert. “You Are Dangerous to Your Health: The Ideology and Politics of Victim Blaming.” International Journal of Health Services 7.4 (1977): 663-680. ———. “Health as a Meaningful Social Practice.: Health 10.4 (2006): 401-20. Dedoose. Computer Software. n.d. Franko, Debra L., Emilie J. Coen, James P. Roehrig, Rachel Rodgers, Amy Jenkins, Meghan E. Lovering, Stephanie Dela Cruz. “Considering J. Lo and Ugly Betty: A Qualitative Examination of Risk Factors and Prevention Targets for Body Dissatisfaction, Eating Disorders, and Obesity in Young Latina Women.” Body Image 9.3 (2012), 381-387. Fikken, Janna J., and Esther D. Rothblum. “Is Fat a Feminist Issue? Exploring the Gendered Nature of Weight Bias.” Sex Roles 66.9-10 (2012): 575-592. Fraser, Suzanne, JaneMaree Maher, and Jan Wright. “Between Bodies and Collectivities: Articulating the Action of Emotion in Obesity Epidemic Discourse.” Social Theory & Health 8.2 (2010): 192-209. Garland Thomson, Rosemarie. “Misfits: A Feminist Materialist Disability Concept.” Hypatia 26.3 (2011): 591-609. Goffman, Erving. Stigma: Notes on the Management of Spoiled Identity. New York: Simon & Schuster, 1963. Grabe, Shelly, and Janet S. Hyde. “Ethnicity and Body Dissatisfaction among Women in the United States: A Meta-Analysis.” Psychological Bulletin 132.2 (2006): 622. Greenhalgh, Susan. “Weighty Subjects: The Biopolitics of the U.S. War on Fat.” American Ethnologist 39.3 (2012): 471-487. Grosz, Elizabeth A. “Bodies-Cities.” Feminist Theory and the Body: A Reader, eds. Janet Price and Margrit Shildrick. New York: Routledge, 1999. 381-387. Guthman, Julie. “Teaching the Politics of Obesity: Insights into Neoliberal Embodiment and Contemporary Biopolitics.” Antipode 41.5 (2009): 1110-1133. Kassirer, Jerome P., and M. Marcia Angell. “Losing Weight: An Ill-Fated New Year's Resolution.” The New England Journal of Medicine 338.1 (1998): 52. Kirkland, Anna. “Think of the Hippopotamus: Rights Consciousness in the Fat Acceptance Movement.” Law & Society Review 42.2 (2008): 397-432. Lewis, Sophie, Samantha L. Thomas, R. Warwick Blood, David Castle, Jim Hyde, and Paul A. Komesaroff. “How Do Obese Individuals Perceive and Respond to the Different Types of Obesity Stigma That They Encounter in Their Daily Lives? A Qualitative Study.” Social Science & Medicine 73.9 (2011): 1349-56. López, Julia Navas. “Socio-Anthropological Analysis of Bariatric Surgery Patients: A Preliminary Study.” Social Medicine 4.4 (2009): 209-217. McPhail, Deborah. “What to Do with the ‘Tubby Hubby?: ‘Obesity,’ the Crisis of Masculinity, and the Nuclear Family in Early Cold War Canada. Antipode 41.5 (2009): 1021-1050. Mann, Traci, A. Janet Tomiyama, Erika Westling, Ann-Marie Lew, Barbara Samuels, and Jason Chatman. “Medicare’s Search for Effective Obesity Treatments.” American Psychologist 62.3 (2007): 220-233. Metzl, Jonathan. “Introduction: Why ‘Against Health?’” Against Health: How Health Became the New Morality, eds. Jonathan Metzl and Anna Kirkland. New York: NYU Press, 2010. 1-14. Puhl, Rebecca M. “Obesity Stigma: Important Considerations for Public Health.” American Journal of Public Health 100.6 (2010): 1019-1028.———, and Kelly D. Brownell. “Psychosocial Origins of Obesity Stigma: Toward Changing a Powerful and Pervasive Bias.” Obesity Reviews 4.4 (2003): 213-227. ——— and Chelsea A. Heuer. “The Stigma of Obesity: A Review and Update.” Obesity 17.5 (2009): 941-964. Schafer, Markus H., and Kenneth F. Ferraro. “The Stigma of Obesity: Does Perceived Weight Discrimination Affect Identity and Physical Health?” Social Psychology Quarterly 74.1 (2011): 76-97. Schwartz, H. Never Satisfied: A Cultural History of Diets, Fantasies, and Fat. New York: Anchor Books, 1986. Wadden, Thomas A., David B. Sarwer, Anthony N. Fabricatore, LaShanda R. Jones, Rebecca Stack, and Noel Williams. “Psychosocial and Behavioral Status of Patients Undergoing Bariatric Surgery: What to Expect before and after Surgery.” The Medical Clinics of North America 91.3 (2007): 451-69. Wilson, Bianca. “Fat, the First Lady, and Fighting the Politics of Health Science.” Lecture. The Graduate Center of the City University of New York. 14 Feb. 2011.

Les équipes d’ingénierie ont souvent recours aux simulations numériques par éléments finis pour étudier et analyser le comportement des ouvrages hydrauliques de grande dimension. Pour les ouvrages en béton, les modèles doivent être en mesure de prendre en compte le comportement non-linéaire des discontinuités aux diverses zones d’interfaces localisées en fondation, dans le corps du barrage ou à l’interface entre la structure et la fondation. Il faut non seulement être capable de représenter le comportement mécanique non-linéaire de ces interfaces (rupture, glissement, contact), mais également de prendre en compte l’écoulement hydraulique à travers ces ouvertures.Dans le cadre de cette thèse, nous nous focalisons d’abord sur la question du comportement des interfaces, que nous abordons à travers le modèle des zones cohésives (CZM). Ce dernier, introduit dans divers codes de calcul par éléments finis (avec éléments finis de joint), est une approche pertinente pour décrire la physique des problèmes de fissuration et de frottement au niveau de discontinuités géométriques. Bien que le CZM a été initialement introduit pour prendre en compte que le phénomène de rupture, nous montrons dans cette thèse que son utilisation peut être étendue aux problèmes de glissement en s'appuyant sur le formalisme élasto-plastique éventuellement couplé à l'endommagement. En outre, des lois de comportement hydromécaniques non-linéaires peuvent être introduites pour modéliser la notion d’ouverture de fissure et le couplage avec les lois d’écoulement fluide. Au niveau mécanique, nous travaillons dans le cadre des matériaux standard généralisés (SGM), qui fournit une classe de modèles qui satisfont d’une manière automatique des principes de la thermodynamique tout en possédant des bonnes propriétés mathématiques utiles pour la modélisation numérique robuste. Nous adaptons le formalisme SGM volumique à la description des zones d'interface. Dans cette première partie de la thèse, nous présentons nos développements faites dans l'hypothèse de SGM adaptée aux CZM, capable de reproduire les phénomènes physiques observés expérimentalement : rupture, frottement, adhésion.En pratique, les non-linéarités du comportement des zones d’interface sont dominées par la présence de contact, ce qui engendre des difficultés numériques importantes pour la convergence des calculs par élément fini. Le développement de méthodes numériques efficaces pour le problème de contact est donc une étape clé pour atteindre l’objectif de simulateurs numériques industriels robustes. Récemment, l’utilisation de techniques d’imposition faible des conditions de contact à la Nitsche a été proposée comme moyen pour réduire la complexité numérique. Cette technique présente plusieurs avantages, dont les plus importants pour nos travaux sont: 1) possibilité de gérer une vaste gamme de conditions (glissement avec ou sans frottement, non interpénétration, etc); 2) la technique se prête à une analyse d'erreur a posteriori rigoureuse. Ce schéma basé sur les conditions d’interface faibles représente le point de départ pour l’estimation d’erreur a posteriori par reconstruction équilibrée de la contrainte. Cette analyse est utilisée pour estimer les différentes composantes d’erreur (p.e., spatiale, non-linéaire), et pour mettre en place un algorithme de résolution adaptatif, ainsi que des critères d’arrêt pour les solveurs itératifs et le réglage automatique d’éventuels paramètres numériques.L'objectif principal de la thèse est donc de rendre robuste la simulation numérique par éléments finis des ouvrages présentant des discontinuités géométriques. On aborde cette question sous angle double : d’un côté on revisite les méthodes existantes de représentation de fissuration en travaillant sur la loi de comportement mécanique pour les joints ; de l’autre on introduit une nouvelle méthode a posteriori pour traiter le problème de contact et propose son adaptation pour les modèles d’interfaces génériques
Engineering teams often use finite element numerical simulations for the design, study and analysis of the behavior of large hydraulic structures. For concrete structures, models of increasing complexity must be able to take into account the nonlinear behavior of discontinuities at the various interfaces located in the foundation, in the body of the dam or at the interface between structure and foundation. Besides representing the nonlinear mechanical behavior of these interfaces (rupture, sliding, contact), one should also be able to take into account the hydraulic flow through these openings.In this thesis, we first focus on the topic of interface behavior modeling, which we address through the Cohesive Zone Model (CZM). This model was introduced in various finite element codes (with the joint elements), and it is a relevant approach to describe the physics of cracking and friction problems at the geometrical discontinuities level. Although initially the CZM was introduced to take into account the phenomenon of rupture, we show in this thesis that it can be extended to sliding problems by possibly relying on the elasto-plastic formalism coupled to the damage. In addition, nonlinear hydro-mechanical constitutive relations can be introduced to model the notion of crack opening and the coupling with the laws of fluid flow. At the mechanical level, we work in the Standard Generalized Materials (SGM) framework, which provides a class of models automatically satisfying some thermodynamical principles, while having good mathematical and numerical properties that are useful for robust numerical modeling. We adapt the formalism of volumetric SGM to the interface zones description. In this first part of the thesis, we present our developpements under the hypothesis of SGM adapted to CZM, capable of reproducing the physical phenomena observed experimentally: rupture, friction, adhesion.In practice, nonlinearities of behavior of interface zones are dominated by the presence of contact, which generates significant numerical difficulties for the convergence of finite element computations. The development of efficient numerical methods for the contact problem is thus a key stage for achieving the goal of robust industrial numerical simulators. Recently, the weak enforcement of contact conditions à la Nitsche has been proposed as a mean to reduce numerical complexity. This technique displays several advantages, among which the most important for our work are: 1) it can handle a wide range of conditions (slip with or without friction, no interpenetration, etc.); 2) it lends itself for a rigorous a posteriori error analysis. This scheme based on the weak contact conditions represents in this work the starting point for the a posteriori error estimation via equilibrated stress reconstruction. This analysis is then used to estimate the different error components (e.g., spatial, nonlinear), and to develop an adaptive resolution algorithm, as well as stopping criteria for iterative solvers and the automatic tuning of possible numerical parameters.The main goal of this thesis is thus to make the finite element numerical simulation of structures with geometrical discontinuities robust. We address this question from two angles: on one side, we revisit the existing methods for the crack representation working on the mechanical constitutive relation for joints; on the other, we introduce a new a posteriori method for the contact problem and we propose its adaptation for the generic interface models

We have long known that tangential contact forces and the friction coefficient at a sliding contact arises not due to some “law” but as a result of contact geometric and material properties in combination with physical processes that are not always accessible to direct experimental verification. While tribologists have occasionally sought alternatives to the coefficient of friction as the primary means to quantify tangential forces at sliding contacts, its convenience, simplicity, long history and lack of viable alternatives assure that it will be remain in use for some time to come. Sometimes the coefficient can remain constant with normal load over orders or magnitude. One can be led to believe that the coefficient is a property of the interface or there is a “law” at work. At other times, the coefficient, usually measured, is said to vary with time, sliding distance or some other variable with no explanation as to why the variation occurs. In the present paper we discuss aspects of friction behavior and modeling, focusing on mechanics and the nature of the friction coefficient. The point of departure is a case where the adhesion theory of friction can be used to understand the mechanics of friction. One can then consider a number of situations and concepts that arise as variations of this case including average versus instantaneous friction; cases when Amontons-Coulomb relations do or don’t apply; static versus dynamic friction; scale effects at rough surfaces; limits of applicability of the friction coefficient; friction measurements, thermal and velocity effects; and local versus global friction and constitutive relations.

Indented wires have been increasingly employed by concrete crosstie manufacturers to improve the bond between prestressing steel reinforcements and concrete, as bond can affect several critical performance measures, including transfer length, splitting propensity and flexural moment capacity of concrete ties. While extensive experimental testing has been conducted at Kansas State University (KSU) to obtain bond characteristics of about a dozen commonly used prestressing wires, this paper develops macro-scale or phenomenological finite element bond models for three typical wires with spiral or chevron indent patterns. The steel wire-concrete interface is homogenized and represented with a thin layer of cohesive elements sandwiched between steel and concrete elements. The cohesive elements are assigned traction-displacement constitutive or bond relations that are defined in terms of normal and shear stresses versus interfacial dilatation and slip within the elasto-plastic framework. A yield function expressed in quadratic form of shear stress and linear form of normal stress is adopted. The yield function takes into account the adhesive mechanism and hardens in the post-adhesive stage. The plastic flow rule is defined such that the plastic dilatation evolves with the plastic slip. The mathematical forms of the yield and plastic flow functions are the same for all three wire types, but the bond parameters are specific for each wire. The adhesive, hardening and dilatational bond parameters are determined for each wire type based on untensioned pullout tests and pretensioned prism tests conducted at KSU. Simulation results using these bond models are further verified with surface strain data measured on actual concrete crossties made with the three respective prestressing wires at a tie manufacturing plant.

This paper describes work in-progress that applies the finite element (FE) method in predicting the responses of individual railroad crossties to rail seat pressure loading in a ballasted track. Both wood and prestressed concrete crossties are examined. The concrete tie is modeled as a heterogeneous medium with prestressing wires or strands embedded in a concrete matrix. The constitutive relations employed in the models are: elasticity followed by damaged plasticity for the concrete material, linear elastic bond-slip relations with potential initiation and evolution of damage to the bond for the steel-concrete interfaces, orthotropic elasticity followed by failure dictated by orthotropic stress criteria for the wood ties, extended Drucker-Prager plasticity for the granular and frictional ballast material, and elastic half space for the subgrade. The corresponding material parameters are obtained from the open literature. Under a simplified pressure load uniformly distributed over the rail seat area, the FE method predicts tensile cracking at the tie base below the rail seats of a concrete tie and compressive failure in the rail seats of a wood tie. The rail seat force-displacement relations are obtained from the simulations. The resultant rail seat forces at which tie failures occur are compared for concrete and wood ties. The FE method appears to be a promising tool for studying the railroad tie behavior under rail seat loading conditions in a ballasted track. Experimental data will be sought to calibrate the material parameters and verify the modeling approach. Additional track components, particularly rails, rail pads and fasteners, will be incorporated in future modeling efforts. This detailed modeling approach may help to shed light on the rail seat deterioration failure mechanisms observed in some concrete ties.

The microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal aging and/or thermal cycling environments. Traditional finite element based predictions for solder joint reliability during thermal cycling accelerated life testing are based on solder constitutive equations (e.g. Anand viscoplastic model) and failure models (e.g. energy dissipation per cycle model) that do not evolve with material aging. Thus, there will be significant errors in the calculations with lead free SAC alloys that illustrate dramatic aging phenomena. In this research, we have developed a new reliability prediction procedure that utilizes constitutive relations and failure criteria that incorporate aging effects, and then validated the new approach through correlation with thermal cycling accelerated life testing experimental data. As a part of this work, a revised set off Anand viscoplastic stress-strain relations for solder have been developed that included material parameters that evolve with the thermal history of the solder material. The effects of aging on the nine Anand model parameters have been determined as a function of aging temperature and aging time, and the revised Anand constitutive equations with evolving material parameters have been implemented in commercial finite element codes. In addition, new aging aware failure criteria have been developed based on fatigue data for lead free solder uniaxial specimens that were aged at elevated temperature for various durations prior to mechanical cycling. Using the measured fatigue data, mathematical expressions have been developed for the evolution of the solder fatigue failure criterion constants with aging, both for Coffin-Manson (strain-based) and Morrow-Darveaux (dissipated energy based) type fatigue criteria. Similar to the findings for mechanical/constitutive behavior, our results show that the failure data and associated fatigue models for solder joints are affected significantly by isothermal aging prior to cycling. After development of the tools needed to include aging effects in solder joint reliability models, we have then applied these approaches to predict reliability of PBGA components attached to FR-4 printed circuit boards that were subjected to thermal cycling. Finite element modeling was performed to predict the stress-strain histories during thermal cycling of both non-aged and aged PBGA assemblies, where the aging at constant temperature occurred before the assemblies were subjected to thermal cycling. The results from the finite element calculations were then combined with the aging aware fatigue models to estimate the reliability (cycles to failure) for the aged and non-aged assemblies. As expected, the predictions show significant degradations in the solder joint life for assemblies that had been pre-aged before thermal cycling. To validate our new reliability models, an extensive test matrix of thermal cycling reliability testing has been performed using a test vehicle incorporating several sizes of fine pitch PBGA daisy chain components. Before thermal cycling began, the assembled test boards were divided up into test groups that were subjected to several sets of aging conditions (preconditioning) including different aging temperatures (T = 25, 55, 85 and 125 C) and different aging times (no aging, and 6 and 12 months). After aging, the assemblies were subjected to thermal cycling (−40 to +125 C) until failure occurred. As with the finite element predictions, the Weibull data failure plots have demonstrated that the thermal cycling reliabilities of pre-aged assemblies were significantly less than those of non-aged assemblies. Good correlation was obtained between our new reliability modeling procedure that includes aging and the measured solder joint reliability data.

Lead-free (Pb-free) solder has seen increasing use in interconnect systems for electronic packages due to legislative and marketing pressures. The NEMI selected eutectic Sn3.9Ag0.6Cu alloy (or a close variation near eutectic Sn3.5Ag1.0Cu used in this study) is a leading Pb-free substitute for the Sn/Pb solder candidate. The reliability of this Pb-free solder alloy under accelerated thermal cycling and thermal shock testing as a function of testing parameters such as dwell time and ramp rate is critical in qualifying the performance of these Pb-free alternatives with the traditionally used Sn37Pb solder This paper presents the reliability of Pb-free solder joints in wafer level chip scale packages (WLCSPs), which are extensions of flip-chip packaging technology to standard surface mount technology, with external dimensions equal to that of the silicon device [1]. The reliability of these packages under both liquid-to-liquid thermal shock (LLTS) testing and accelerated air-to-air thermal cycling (AATC) conditions, as a function of dwell times and ramp rates is evaluated using extensive experimental testing in combination with finite element analysis. Besides, two asymmetric cycles in which the cold and hot dwell times differ at two temperature extremes were studied. Along with the Pb-free solder, some test vehicles were built using eutectic Sn-Pb solder and evaluated for comparison purposes. Experimental results show that an increase in ramp rate does not adversely affect the solder joint reliability in the case of Pb-free solder. The reliability of lead-free WLCSPs was highly dependent upon the dwell time at the temperature extremes, with this dependency being considerably greater for the lead-free allow than for Sn/Pb at 0°C and 100°C. Accelerated test results show that increasing the dwell time from 280 to 900 seconds reduced the N63.2 of the Sn/Pb samples by 12% and the Pb-free samples by 65%. Reliability during asymmetric cycles resulted in a trend that is similar in two cases studied. A predictive equation was developed to evaluate the characteristic life of the package with respect to the dwell time. Non-linear, finite element (FE) modeling was conducted using temperature dependent creep constitutive relations for the Pb-free solder to understand the experimental trends observed. The FE results predicted the same trend of the package reliability as observed experimentally, with respect to the changing dwell and ramp times. The finite element predictions demonstrated reasonable correlation with the experimental observations.