Kinematic and stochastic surface topography of machined tial6v4-parts by means of ball nose end milling

Ball nose end mills are usually applied during 5-axes machining of high functional parts especially in the aerospace industry. The systematical study of the relationship between process forces and kinematics, surface topography and subsurface properties is fundamental to ensure a high surface integrity. This paper deals with the topography of machined surfaces of TiAl6V4 parts by means of ball nose end milling. The machined surface has been analyzed and the kinematic topography, influenced by the process parameters and the geometry of the cutting tool, has been computed. By subtracting the surface measurements from the computed topography, the stochastic topography of the machined surface, e.g. roughness and cracks, can be determined. Furthermore, an approach is given for predicting the stochastic topography based on the process forces during machining of TiAl6V4. © 2011 Published by Elsevier Ltd.DFG/CRC/87

Prediction of the Principal Stress Direction for 5-axis Ball End Milling

While regenerating damaged components, e.g. compressor blades, the removal of excess weld material called re-contouring often determines the surface integrity including the residual stress state. A load-specific residual stress state is beneficial for lifetime. This leads to the necessity to predict the resulting residual stress state after machining. The paper describes two models, which predict the principal stress direction as a residual stress characteristic for 5-axis ball nose end milling of Ti-6Al-4 V. One model uses process force components, the other is based on the microtopography of the workpiece, which is influenced by the kinematics of the process.DFG/Collaborative Research Centre/87

Approaches for improving cutting processes and machine too in re-contouring

Re-contouring in the repair process of aircraft engine blades and vanes is a crucial task. Highest demands are made on the geometrical accuracy as well as on the machined surface of the part. Complexity rises even more due to the unique part characteristic originating from the operation and repair history. This requires well-designed processes and machine tool technologies. In this paper, approaches for coping with these challenges and improving the re-contouring process are described and discussed. This includes an advanced process simulation with its capabilities to accurately depict different material areas and predict process forces. Beyond, experimental investigations on workpiece-tooldeflection are presented. Finally, a machine tool prototype with a novel electromagnetic guiding system is introduced and the benefits of this technology in the field of repair are outlined.DFG/CRC/87

Prediction of the 3D surface topography after ball end milling and its influence on aerodynamics

The surface topography of milled workpieces often defines their performance. One example is blades in turbine engines, where the topography defines the flow losses. This type of complex goods is often machined by ball end mills, either for manufacture or repair. The literature offers various model types to predict the surface topography in order to design a machining process without prior experiment. The most accurate models use the real kinematics of the process and blend the tool with the workpiece. But this type of surface prediction ignores the differences between the reality and the simulation due to vibrations, tool chipping etc. This paper presents a combined approach using the kinematic topography from the machining simulation and adds a stochastic topography based on empirical data. It could be shown, that the usage of the stochastic topography greatly affects the flow losses and thus cannot be ignored.DFG/CRC/87

Doppler radar detection of vortex hazard indicators

Wake vortex experiments were conducted at White Sands Missile Range, NM using the AN/MPS-39 Multiple Object Tracking Radar (MOTR). The purpose of these experiments was twofold. The first objective was to verify that radar returns from wake vortex are observed for some time after the passage of an aircraft. The second objective was to verify that other vortex hazard indicators such as ambient wind speed and direction could also be detected. The present study addresses the Doppler characteristics of wake vortex and clear air returns based upon measurements employing MOTR, a very sensitive C-Band phased array radar. In this regard, the experiment was conducted so that the spectral characteristics could be determined on a dwell to-dwell basis. Results are presented from measurements of the backscattered power (equivalent structure constant), radial velocity and spectral width when the aircraft flies transverse and axial to the radar beam. The statistics of the backscattered power and spectral width for each case are given. In addition, the scan strategy, experimental test procedure and radar parameters are presented

(un)Doing standards in education with actor-network theory

Recent critiques have drawn important attention to the depoliticized consensus and empty promises embedded in network discourses of educational policy. While acceding this critique, this discussion argues that some forms of network analysis – specifically those adopting actor-network theory (ANT) approaches - actually offer useful theoretical resources for policy studies. Drawing from ANT-inspired studies of policy processes associated with educational standards, the article shows the ambivalences and contradictions as well as the possibilities that can be illuminated by ANT analysis of standards as networks. The discussion outlines the diverse network conceptions, considerations and sensibilities afforded by ANT approaches. Then it shows four phenomena that have been highlighted by ANT studies of educational standards: ordering (and rupturing) practice through ‘immutable mobiles’, local universality, tensions among networks of prescription and networks of negotiation, and different co-existing ontological forms of the same standards. The conclusion suggests starting points, drawing from these ANT-inspired network analyses, for examining policy processes associated with educational standards

Education and service : how theories can help in understanding tensions

Acknowledgements: our thanks to Ayelet Kuper for a helpfuldiscussion about the possible application of discourseanalysis to service–training tensionsPeer reviewedPostprin

What have we been thinking of? A critical overview of 40 years of student learning research in higher education

This paper is a response to the request from the organisers of the HECU4 conference to consider the following three questions in relation to the recent history of research into student learning in higher education: What do we know?, What do we need to know?, and What might we do about it? A survey of article titles reporting on research into student learning was carried out in three key higher education journals, and the results of this were then considered in the context of other, related research perspectives. The paper will first report on the results of this review, and then discuss these results in the context of theoretical moves in psychology and sociology over the same period of time. The trends identified in the higher education journals will then be compared to research into student learning in higher education which is published in two other disciplinary areas: Adult Education and Sociolinguistics. After raising some questions that arise from these comparisons, the final section of the paper will outline some suggestions about ways in which higher education researchers might begin to ‘think differently’ about learning and research in this field

Investigating pupils’ interactions around digital texts: a spatial perspective on the ‘classroom-ness’ of digital literacy practices in schools

This paper complements debates around use of new technologies and literacy in education by proposing a focus on “classroom-ness.” It highlights the significance of incidental, everyday and ephemeral practices associated with classroom technology-use. Using examples from a study of primary pupils’ interactions around digital texts, it argues that we must acknowledge the distinctiveness of technology-use in classroom contexts but also see the spaces associated with those contexts as continually constructed, relational and heterogeneous. This helps us look beyond binary distinctions – between in/out of school and global/local practices, on/off-screen and on/offline activity, material/virtual contexts and official/unofficial discourses – to recognise the complex and nuanced ways that children make meaning around new technologies. It is proposed that this theoretical lens – in recognising the complexity of classroom-ness – can help us better understand the barriers and opportunities associated with effective integration of new technologies in educational contexts

Vocational knowledge in motion: rethinking vocational knowledge through vocational teachers' professional development

The paper presents empirical data to consider some of the current debates concerning the nature of vocational knowledge taught in Further Education colleges to students following craft, vocational and occupational courses. The concept of ‘knowledge in motion’ and workplace learning theories are employed as a conceptual framework to examine the continuing professional development (CPD) activities of vocational teachers. This is used to shed light on the ways in which teachers use CPD as a means of accessing and transporting vocational knowledge from occupations to classrooms. Empirical data were gathered through questionnaire, in-depth interviews and participant observation. The findings are presented around five themes: (1) the range of CPD engaged with by vocational teachers; (2) the limitations of propositional, explicit knowledge; (3) engaging with and capturing tacit knowledge; (4) managing the temporality of vocational knowledge; and (5) networking within and to the occupation. Findings suggests that vocational knowledge is distributed and networked and this conceptualisation makes visible some of the ways teachers are able, through CPD activity, to transport vocational knowledge from occupations to classrooms