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- Vänje, Annika, Professor, 1963-
(författare)
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Knäcka Koderna : Praxis kring kön, industriell organisation och ledarskap
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main purpose of this doctoral thesis is to describe, analyse and initiate processes of change from a gender point of view. In the present field study the focus is on gender-creating processes in and around formal and informal structures at an engineering company´s organisation. The central theme is the implication of gender in relation to industrial organisation and leadership.The aim of this thesis is i) to identify processes and praxis in the organisation that create both opportunities and obstacles for women who have made an untraditional choice of career as engineers and managers, ii) on the basis of this knowledge and together with practitioners in the organisation initiate processes of change that will increase the proportion of women managers.The doing-gender approach has been used as a theoretical tool in order to understand the processes surrounding technology, leadership and gender in the organisation. Doing gender allows us to initiate process-thinking about how gender is constructed in different social contexts, such as those in industrial organisations. From a doing-gender perspective the central question is what an individual does and not what he or she is. In other words, the focus is on actions.The methodological approach is action-oriented, using as its starting point an interactive research perspective. The interactive approach has a democratic basic outlook, it combines theoretical understanding with practical action.This doctoral thesis helps to elucidate the complexity of gender-creating structures, processes and practices in an industrial organisation. Its empirical method also shows how researchers and practitioners in the organisation can jointly launch processes of change on the basis of a gender-theoretical basis.The thesis presents a gender-theoretical model for change and analysis that is based on the so-called doing-gender approach. This model has been of importance both as an analytical tool and as a starting point for initiating processes of change. The model has four dimensions and they are dissimilar in character and are more or less demanding of time in bringing about changes. They each have an effect and affect each other in various constellations in the gender-creating processes in organisations.The viewpoints that the doing-gender approach communicates makes it possible to change existing attitudes and expectations concerning gender, since the construction of gender is a continually ongoing process that differs in different contexts.One contribution that this thesis makes is to illuminate the complexity of organisation and gender. It contributes to research by providing empirical examples of gender-creating praxis in an engineering company and by showing how we can work on processes of change from a gender perspective.
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| 2. |
- Gustafsson, Emil
(författare)
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Design and application of experimental methods for steel sheet shearing
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Shearing is the process where sheet metal is mechanically cut between two tools. Various shearing technologies are commonly used in the sheet metal industry, for example, in cut to length lines, slitting lines, end cropping etc. Shearing has speed and cost advantages over competing cutting methods like laser and plasma cutting, but involves large forces on the equipment and large strains in the sheet material. The constant development of sheet metals toward higher strength and formability leads to increased forces on the shearing equipment and tools.Shearing of new sheet materials imply new suitable shearing parameters. Investigations of the shearing parameters through live tests in the production are expensive and separate experiments are time consuming and requires specialized equipment. Studies involving a large number of parameters and coupled effects are therefore preferably performed by finite element based simulations. Accurate experimental data is still a prerequisite to validate such simulations. There is, however, a shortage of accurate experimental data to validate such simulations.In industrial shearing processes, measured forces are always larger than the actual forces acting on the sheet, due to friction losses. Shearing also generates a force that attempts to separate the two tools with changed shearing conditions through increased clearance between the tools as result. Tool clearance is also the most common shearing parameter to adjust, depending on material grade and sheet thickness, to moderate the required force and to control the final sheared edge geometry.In this work, an experimental procedure that provides a stable tool clearance together with accurate measurements of tool forces and tool displacements, was designed, built and evaluated. Important shearing parameters and demands on the experimental set-up were identified in a sensitivity analysis performed with finite element simulations under the assumption of plane strain. With respect to large tool clearance stability and accurate force measurements, a symmetric experiment with two simultaneous shears and internal balancing of forces attempting to separate the tools was constructed.Steel sheets of different strength levels were sheared using the above mentioned experimental set-up, with various tool clearances, sheet clamping and rake angles. Results showed that tool penetration before fracture decreased with increased material strength. When one side of the sheet was left unclamped and free to move, the required shearing force decreased but instead the force attempting to separate the two tools increased. Further, the maximum shearing force decreased and the rollover increased with increased tool clearance.Digital image correlation was applied to measure strains on the sheet surface. The obtained strain fields, together with a material model, were used to compute the stress state in the sheet. A comparison, up to crack initiation, of these experimental results with corresponding results from finite element simulations in three dimensions and at a plane strain approximation showed that effective strains on the surface are representative also for the bulk material.A simple model was successfully applied to calculate the tool forces in shearing with angled tools from forces measured with parallel tools. These results suggest that, with respect to tool forces, a plane strain approximation is valid also at angled tools, at least for small rake angles.In general terms, this study provide a stable symmetric experimental set-up with internal balancing of lateral forces, for accurate measurements of tool forces, tool displacements, and sheet deformations, to study the effects of important shearing parameters. The results give further insight to the strain and stress conditions at crack initiation during shearing, and can also be used to validate models of the shearing process.
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| 3. |
- Tharani, Soraya
(författare)
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Immigration, security and the public debate on US language policy : A critical discourse analysis of language attitudes in the United States of America
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The narrative of the United States is of a "nation of immigrants" in which the language shift patterns of earlier ethnolinguistic groups have tended towards linguistic assimilation through English. In recent years, however, changes in the demographic landscape and language maintenance by non-English speaking immigrants, particularly Hispanics, have been perceived as threats and have led to calls for an official English language policy. This thesis aims to contribute to the study of language policy making from a societal security perspective as expressed in attitudes regarding language and identity originating in the daily interaction between language groups. The focus is on the role of language and American identity in relation to immigration. The study takes an interdisciplinary approach combining language policy studies, security theory, and critical discourse analysis. The material consists of articles collected from four newspapers, namely USA Today, The New York Times, Los Angeles Times, and San Francisco Chronicle between April 2006 and December 2007. Two discourse types are evident from the analysis namely Loyalty and Efficiency. The former is mainly marked by concerns of national identity and contains speech acts of security related to language shift, choice and English for unity. Immigrants are represented as dehumanised, and harmful. Immigration is given as sovereignty-related, racial, and as war. The discourse type of Efficiency is mainly instrumental and contains speech acts of security related to cost, provision of services, health and safety, and social mobility. Immigrants are further represented as a labour resource. These discourse types reflect how the construction of the linguistic 'we' is expected to be maintained. Loyalty is triggered by arguments that the collective identity is threatened and is itself used in reproducing the collective 'we' through hegemonic expressions of monolingualism in the public space and semi-public space. The denigration of immigrants is used as a tool for enhancing societal security through solidarity and as a possible justification for the denial of minority rights. Also, although language acquisition patterns still follow the historical trend of language shift, factors indicating cultural separateness such as the appearance of speech communities or the use of minority languages in the public space and semi-public space have led to manifestations of intolerance. Examples of discrimination and prejudice towards minority groups indicate that the perception of worth of a shared language differs from the actual worth of dominant language acquisition for integration purposes. The study further indicates that the efficient working of the free market by using minority languages to sell services or buy labour is perceived as conflicting with nation-building notions since it may create separately functioning sub-communities with a new cultural capital recognised as legitimate competence. The discourse types mainly represent securitising moves constructing existential threats. The perception of threat and ideas of national belonging are primarily based on a zero-sum notion favouring monolingualism. Further, the identity of the immigrant individual is seen as dynamic and adaptable to assimilationist measures whereas the identity of the state and its members are perceived as static. Also, the study shows that debates concerning language status are linked to extra-linguistic matters. To conclude, policy makers in the US need to consider the relationship between four factors, namely societal security based on collective identity, individual/human security, human rights, and a changing linguistic demography, for proposed language intervention measures to be successful.
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| 6. |
- Domkin, Konstantin
(författare)
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Constitutive models based on dislocation density : formulation and implementation into finite element codes
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Correct description of the material behaviour is an extra challenge in simulation of the materials processing and manufacturing processes such as metal forming. Material models must account for varying strain, strain rate and temperature, and changing microstructure. This study is devoted to the physically based models of metal plasticity - dislocation density models, their numerical implementation and parameter identification. The basic concepts of dislocation density modelling are introduced including the effects of static and dynamic recovery, influence of strain path and modelling of the back-stress. Possible mechanisms controlling athermal and thermally activated processes involving dislocations, vacancies and solute atoms are also discussed. Mobile and immobile dislocation densities, vacancy concentrations and other variables are treated as internal state variables. The dislocation models are incorporated in a classical continuum plasticity or viscoplasticity framework by means of the evolution equations for these internal variables which effectively control the hardening behaviour. Implementation of these models into finite element codes is straightforward and numerically efficient. Dislocation models are implemented in user material subroutines and used in simulations of sheet metal forming and extrusion. The models are also implemented in a custom toolbox for parameter optimisation in Matlab. A special extended version of a return-map stress update algorithm and its consistent tangent are derived to accommodate the complex coupling effects in a material model, in which all thermo-elastic and hardening properties may depend on the plastic strain. Numerical difficulties of parameter optimisation such as non-uniqueness of the solution, high sensitivity to the starting guess-value and to the choice of the error function appear to be a common problem with advanced material models. Simultaneous curve-fitting of multiple experimental curves of different mechanical testing types is advised to achieve more robust optimisation results. Parameters of dislocation density models usually have clear physical interpretation, and it is possible to obtain values of some of them from sources other than mechanical testing. The accuracy of physically based models is totally dependent on finding the adequate equations to describe the physical processes dominating the material behaviour during deformation. These equations may be more or less accurate than standard engineering models or data interpolation approaches. However, the use of physically significant parameters related to the microstructure properties such as grain size etc gives a natural way to couple them to the models for microstructure evolution, which is important in simulations of manufacturing processes.
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| 7. |
- Hansson, Sofia
(författare)
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Modeling of the Stainless Steel Tube Extrusion Process
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Seamless tubes of stainless steel can be extruded using glass as a lubricant in the Ugine-Sejournet process. The process is performed at high temperature and is associated with large deformations and high strain rates. The use of finite element modeling (FEM) in the analysis and design of extrusion and other metal forming processes is constantly increasing. Computer models that with adequate accuracy can describe the material behavior during extrusion can be very useful for product and process development. The process development in industrial extrusion today is, to a great extent, based on trial and error. This often involves full size experiments which are expensive, time consuming and interfere with the production. It would be of great value if these experiments could be performed in a computer. In this work, FE models of the stainless steel tube extrusion process were developed and used. Simulations were carried out for different tube dimensions and three different materials: two austenitic stainless steels and one duplex (austenitic/ferritic) stainless steel. The models were validated by comparing the predicted values of extrusion force with measurements from production presses. A large number of input parameters are used in a FE analysis of extrusion. This includes boundary conditions, initial conditions and parameters that describe the mechanical and thermal properties of the material. The accuracy of the extrusion simulation depends, to a large extent, on the accuracy of these parameters. Experimental work, both in the form of material testing and production trials, was performed in order to give an accurate description of the input parameters in these extrusion models. A sensitivity analysis was performed for one of the models and the results showed that the initial billet temperature is the parameter that has the strongest impact on the extrusion force. In order to study the temperature evolution in the billet during manufacturing, the entire process chain at extrusion of stainless steel tubes was simulated using FEM. This process flow model includes sub-models of induction heating, expansion and extrusion. The work includes the use of a dislocation density-based material model for the AISI type 316L stainless steel. It is expected that this physically based model can be extrapolated to a wider range of strains, strain rates and temperatures than an empirical model, provided that the correct physical processes are described by the model and that no new phenomena occur. This is of interest for steel extrusion simulations since this process is carried out at higher strains and strain rates than what are normally used in mechanical laboratory tests. The developed models have given important contributions to the understanding of different phenomena that occur during extrusion of stainless steel tubes, and can be used to analyze how different process parameters affect the extrusion process.
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