Built-up edge mechanisms in the machining of duplex stainless steels

 The thesis work was aimed at resolving long established issues with difficult-to-machine materials. The main thesis contribution, is the academic community now has a better understanding of how the issue of built-up edge is occurring when machining duplex stainless steel alloys, which will aid in the machining sector.

Developments in machining of stacked materials made of CFRP and titanium/aluminum alloys

The aim of this article is to investigate the drilling of carbon fiber-reinforced plastic (CFRP) composite/metal stack-ups to have a details picture of the developments in this complex area. The forces and torque, chip shape, surface finish and geometry, and tool material and tool wear for drilling composite/metal stack-ups have been analyzed in details in addition to drilling mechanism of CFRP. The relation between input and output parameters was discussed and the trend of input parameters for damage free and tight tolerance holes has been investigated based on the literature. The main findings are (i) heat, built-up edge and chips generated from drilling of metallic layers damages CFRP surface, (ii) order of material layers affects the drilling outcomes significantly, (iii) coatings and step-shape on the cutting tool improves the tool performance, (iv) tool materials should be selected based on the material of metallic layer, (v) chipping, adhesion, abrasion and attrition are main tool wear mechanisms during machining of CFRP/metal stacks and (vi) application of coolant improves the machinability.

Chip formation mechanism and machinability of wrought duplex stainless steel alloys

This paper investigates the chip formation mechanism and machinability of two-phase materials, such as, wrought duplex stainless steel alloys SAF 2205 and SAF 2507. SEM and optical microscopic details of the frozen cutting zone and chips revealed that the harder austenite phase dissipates in the advancement of the cutting tool, being effectively squeezed out of the softer ferrite phase. Microhardness profiles reveal correlation in hardness from the workpiece material transitioning to the chip. The tool wear (TiAIN + TiN coated solid carbide twist drill) and machining forces were investigated. Tool wear, was dominantly due to the adhesion process which developed from built-up edge formation, is highly detrimental to the flank face. Flute damage was also observed as a major issue in the drilling of duplex alloys leading to premature tool failure. Duplex 2507 shows higher sensitivity to cutting speed during machining and strain hardening at higher velocity and less machinability due to presence of higher percentage of Ni, Mo and Cr.

Weldability and machinability of duplex stainless steel

This chapter investigates two important processing methods, such as welding and machine of duplex stainless steel. The welding process welding generally degrades the properties of these materials by redistributing the phases during melting and solidification. On the other hand, the redistribution during machining mainly take place combined effect of stress, strain rate and temperature. Mechanism of machining process and several welding methods has been analysed in details. It was found that outcomes of welding processes depend on the welding methods. Most of the cases an appropriate annealing process can be used to restore the expected properties of the weld joints though the parameters of annealing process are different in different welding methods. Nonmetallic inclusions and the low carbon content of duplex stainless steel reduce the machinability of duplex stainless steel. SEM and optical microscopic details of the frozen cutting zone and chips revealed that the harder austenite phase dissipates in the advancement of the cutting tool, being effectively squeezed out of the softer ferrite phase. Abrasion and adhesion were the most common wear modes developed on the flank and rake faces. Adhesion wear being the most prevalent on the flank face, appeared to be initiated by built-up edge formation.

Investigation on the behavior of austenite and ferrite phases at stagnation region in the turning of duplex stainless steel alloys

This paper investigates the deformation mechanisms and plastic behavior of austenite and ferrite phases in duplex stainless steel alloys 2205 and 2507 under chip formation from a machine turning operation. SEM images and EBSD phase mapping of frozen chip root samples detected a build-up of ferrite bands in the stagnation region, and between 65 and 85 pct, more ferrite was identified in the stagnation region compared to austenite. SEM images detected micro-cracks developing in the ferrite phase, indicating ferritic build-up in the stagnation region as a potential triggering mechanism to the formation of built-up edge, as transgranular micro-cracks found in the stagnation region are similar to micro-cracks initiating built-up edge formation. Higher plasticity of austenite due to softening under high strain is seen responsible for the ferrite build-up. Flow lines indicate that austenite is plastically deforming at a greater rate into the chip, while ferrite shows to partition most of the strain during deformation. The loss of annealing twins and activation of multiple slip planes triggered at high strain may explain the highly plastic behavior shown by austenite.

Impacts of wear and geometry response of the cutting tool on machinability of super austenitic stainless steel

This paper presents a study of tool wear and geometry response whenmachinability tests were applied under milling operations onthe Super Austenitic Stainless Steel alloy AL-6XN. Eight milling trials were executed under two cutting speeds, two feed rates, andtwo depths of cuts. Cutting edge profile measurements were performed to reveal response of cutting edge geometry to the cuttingparameters and wear. A scanning electron microscope (SEM) was used to inspect the cutting edges. Results showed the presenceof various types of wear such as adhesion wear and abrasion wear on the tool rake and flank faces. Adhesion wear represents theformation of the built-up edge, crater wear, and chipping, whereas abrasion wear represents flank wear.Thecommonly formed wearwas crater wear. Therefore, the optimum tool life among the executed cutting trails was identified according to minimum lengthand depth of the crater wear.The profile measurements showed the formation of new geometries for the worn cutting edges due toadhesion and abrasion wear and the cutting parameters.The formation of the built-up edge was observed on the rake face of thecutting tool. The microstructure of the built-up edge was investigated using SEM. The built-up edge was found to have the austeniteshear lamellar structure which is identical to the formed shear lamellae of the produced chip.

The making of modern scientific personae: the scientist as a moral person? Emil Du Bois-Reymond and his friends

This article examines the notion of the 'scientist as a moral person' in the light of the early stages of the commodification of science and the transformation of research into a big enterprise, operating on the principle of the division of labour. These processes were set in train at the end of the 19th century. The article focuses on the concomitant changes in the public persona and the habitus of scientific entrepreneurs. I begin by showing the significance of the professional networks that were built up and maintained to further a group's research ideas and the careers of its members, thus demonstrating one condition on which depended their practice of science and their ability to earn a living. This leads to a characterization of the changing styles of work, thought and life, and to a consideration of public perceptions and of the ways in which a new self-image of scholarship and science was fashioned. A critical discussion of the public role of these mandarin scientists follows in order to highlight the strains created by the commodification of science at a time of international tensions and conflicts, when shared beliefs in scholarly cosmopolitanism were subverted by appeals to science and scholarship to work in the service of one's own nation as its 'courtiers'. Various considerations of peculiar analogies between national styles of research and the style of social organization are then noted. In the final section, the article queries the long-term impact of these developments on the ideal of the scientist as a 'moral person'. Taking a cue from Max Weber and pursuing reflections by Zygmunt Bauman on 'science moralized', I argue that the emergence of a type of 'specialists without spirit' was an unintended but fatal consequence of the changes in research practices promoted by scientific entrepreneurs such as Du Bois-Reymond. I conclude that the temptation to sever the ties to a general ethos of civil virtues lay in the rationalization, specialization and potential de-humanization of the objectifying scientific outlook once advocated for its efficiency.

Time to make a difference: using action research to foster student engagement

This paper reports on a project, funded by the Victorian Department of Education and Training (Australia), undertaken to explore the capacity for teachers to develop innovative teaching and learning strategies aimed at improving the educational experiences of students in the middle years. Central to this charter was the need for local schools to form Clusters, share ideas and develop strategies designed to improve student engagement and connection. In forming the Buxton (pseudonym) Cluster, four schools came together to declare their shared interest in improving student connection through the teaching and learning of mathematics. The 22 teachers involved in the project shared a broad concern that the traditional pedagogies built up around the maths discipline were contributing to the wider level of student disconnection observed in the middle years. In thinking about change, the group were attracted to constructivist approaches to pedagogy in which learning opportunities and tasks are varied sufficiently to appeal to the various learning styles and aptitudes of learners. Favouring an action research framework teachers involved in the project embarked on the implementation of pedagogic reforms aimed at improving levels of student engagement.

Inorganic-organic hybrids of the p,p'-diphenylmethylenediphosphinate ligand with bivalent metals: a new 2D-layered phenylphosphinate zinc(II) complex

By reaction of Zn(CH₃COO)₂ with p,p′-diphenylmethylenediphosphinic acid in water a new inorganic–organic polymeric hybrid of formula [Zn(CH₂(P(Ph)O₂)₂)] has been synthesized and completely characterized. The X-ray analysis established that the structure consists of 2D-layered polymeric array, the 2D-sheets being built up through strong covalent linkages between the zinc metal and the oxygen donors of the phenylphosphinate ligand. The 2D-layers, which are featuring a mesh-net fashion, present voids of various dimensionality, up to 24-membered rings. The organic parts of the hybrid ligand, namely the phenyl rings, are shielding the inorganic skeleton of the layers, preventing the propagation of the polymer in the third dimension. No water molecules are present in the lattice, both of coordination and crystallization. Crystal data are: monoclinic, P2₁Ic, a=11.840(2), b=9.646(9), c=12.516(5) Å, β=95.03(2), V=1423.9(15) ų, Z=4. The solid material has been characterized by ³¹P MAS NMR spectroscopy and thermogravimetric analysis.

MRP-production planning in agile manufacturing

Over the years many researchers have been investigating the area of MRP production planning and still is an area of high interest today. This paper look at production planning where there is unpredictable demands due to the type of product and market a company produces for. Production planning becomes difficult when demand fluctuates unpredictably, and hence a historical sales forecast is used as the initial data for production planning. The sales from previous years, especially in a seasonal market, don't necessarily correlate well to the current and future sales for the next year. A planner working in such environment would have himself frustrating to create a feasible production plan that not only needs to meet customer's demands but also to built up the 'correct' amount of stock for that peak sell season. To overcome some of these problems, This work describes a production planning methodology that can be implemented robustly and quickly. This paper has studied two multi-item lot-sizing problems. We detailed the development of the planning problem mathematically and highlight some solutions to initial problems investigated.

Barriers to learners' successful completion of VET flexible delivery programs

In the early 1990s, Australian policymakers began explicitly promoting increased use of flexible delivery in vocational education and training (VET). Some researchers argued that many students lack the learning skills required to deal with the unique demands of flexible delivery. Concerns were also raised about the VET sector's capacity to help students develop needed cognitive and metacognitive skills. A review of the literature revealed wide agreement that students' success in flexible delivery and open and distance education in Australia and elsewhere is generally determined by a complex interplay of factors, including the following: readiness for self-directed learning; ability to balance the time demands of study with other commitments such as family and work; level of literacy; ability to understand and deal with assessment requirements; level of motivation; and previous educational experiences. Two case studies based on the actual experiences of two of six students interviewed about their experiences in flexible VET delivery were reviewed. Both students decided to withdraw from their VET course because of several interconnected factors that built up over time. Both cases illustrated that some problems that can be addressed quickly in face-to-face learning environments are much more difficult to resolve when students are off campus.

The procedural validity of retrospective case note diagnosis

Objective: Deriving diagnoses from retrospective case note examination is a common practice in psychiatric research. The Operational Criteria (OPCRIT) diagnostic checklist is essentially a checklist built up of operational criteria defined by a comprehensive glossary and is designed to assign reliable diagnoses from case notes. However, the validity of such a procedure compared with procedures involving prospective assessment has never been tested. We examined the procedural validity of the OPCRIT diagnostic system in relation to four other diagnostic procedures mostly employing prospectively gathered information.

Method: Three experienced psychopathology raters rated the case notes and clinical abstracts, using the OPCRIT method of diagnostic assignment, of 50 subjects who had participated in an early procedural validity study as an adjunct to the DSM-IV Field Trial for psychotic disorders. The setting was the Early Psychosis Prevention and Intervention Centre (EPPIC), which focuses on first episode psychosis.

Results: The pairwise concordance with the other procedures for DSM-III-R diagnoses assigned by OPCRIT using ratings derived from either the clinical abstracts or the case notes was found to be only poor to moderate when compared with the pairwise concordance of the four other procedures. The per cent agreement between OPCRIT clinical abstracts diagnoses and the other procedures ranged from 49% to 60% with kappa values between 0.30 and 0.45, and for OPCRIT case note diagnoses and the other procedures the per cent agreement range was between 44% and 57% and the kappa values were between 0.35 and 0.49.

Conclusions: The procedural validity of diagnoses assigned via the application of checklists of operational criteria to case notes and clinical abstracts alone is unacceptably poor. Such sources need to be buttressed by other data, particularly direct patient interview and informant material.

Trainers and transformation : facilitating the 'dark side' of vocational learning

'Transformative learning' is a term used by Mezirow (1991) and his followers to designate a specifically 'adult' kind of learning that involves shifts in how learners view the world and themselves. New research into learning in VET suggests that in some subject areas transformative learning may play more than an incidental role. Among the implications of this finding is that the trainer's practice may be more important in VET than it has been the custom to acknowledge. When transformative learning systematically contributes to VET, the trainer becomes a co-constructor of competence rather than a transmitter of skills and knowledge.

This paper reports on this new research and reflects on the role of the trainer in the process of VET-oriented transformative learning. Results indicate that some trainers of youth workers develop a practice that responds to the contours and dangers of transformative learning without necessarily being aware of the body of knowledge that has built up around this type of learning. The paper suggests that in some VET sectors, trainers and RTO's could enhance their work by taking stock of transformative learning research and theory.