Isaac Flitta

Unitec New Zealand, Design and Visual Arts, Faculty Member

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Papers by Isaac Flitta

Simulation of aluminium extrusion process

The aim of this thesis is to model the extrusion process conditions for some aluminium alloys usi... more The aim of this thesis is to model the extrusion process conditions for some aluminium alloys using Finite Element Modelling (FEM) program. All the simulations were performed with the implicit finite element code FORGE20 (2-D) and FORGE3® (3-D). In this work only the alloys AA2024, AA2014, Al-1 %Cu and AA6063 where experimental work is available were considered. The FORGE2® program was used to investigate and select an appropriate flow stress constitutive equation to describe the material behaviour to model the process conditions. The extrusion pressure and the temperature rise were predicted and the pressure-displacement trace and the events which take place in the deformed material during the extrusion process were also simulated. The effect of the initial billet temperature on friction, and the extent of the surface zone affected by surface friction and the consequence changes in material flow were investigated. The changes in the subgrain size during quasi-static deformation wer...

Integrating Mobile Web 2.0 within tertiary education

Based on three years of innovative pedagogical development and guided by a participatory action r... more Based on three years of innovative pedagogical development and guided by a participatory action research methodology, this paper outlines an approach to integrating mobile web 2.0 within a tertiary education course, based on a social constructivist pedagogy. The goal is to facilitate a student-centred, collaborative, flexible, context-bridging learning environment that empowers students as content producers and learning context generators, guided by lecturers who effectively model the use of the technology. We illustrate how the introduction of mobile web 2.0 has disrupted the underlying pedagogy of the course from a traditional Attelier model (face-to-face apprenticeship model), and has been successfully transformed into a context independent social constructivist model. Two mobile web 2.0 learning scenarios are outlined, including; a sustainable house design project (involving the collaboration of four departments in three faculties and three diverse groups of students), and the i...

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Using Smartphones and Mobile Web 2.0 to Create a Mobile Computing Platform for Tertiary Education

Today’s smartphones are mobile multimedia computers, in Nokia’s words: “It’s what computers have ... more Today’s smartphones are mobile multimedia computers, in Nokia’s words: “It’s what computers have become”. Smartphone manufacturers have seen the potential to partner with online social software (Web2.0) sites (e.g. Flickr, YouTube, Vox, Ovi etc…) to produce a mobile computing platform to capture and share our daily lives with friends and family, anywhere, anytime. These tools can be utilized within tertiary education to create context independent collaborative learning environments. Pedagogical design of learning experiences using mobile web2.0 allows a tutor to create rich learning environments for students beyond the classroom or lecture theatre. This paper illustrates this by analysing students responses to a third year Product Design project that transformed a traditionally paper-based learning journal into an interactive, collaborative, online eportfolio using mobile web2.0 technologies facilitating an explicit social constructivist pedagogy. Students were provided with a Nokia...

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A more sustainable hull form

Executive Summary The aim of the project was to find a planing powerboat hull form capable of bei... more Executive Summary The aim of the project was to find a planing powerboat hull form capable of being pushed through the water more easily than existing hull forms and yet which still maintains, or even improves on practical performance factors such as sea keeping ability, stability, and directional stability. The speed most suited to test our hull shape is in the speed range 25 knots and under, a practical range for the general power boating public. There is some education required to have the power boating public understand the economy advantage of not carrying more power/weight than necessary.

Material flow and prediction of extrusion pressure when extruding through bridge dies using FEM

Investigation of friction during the extrusion оf Al-alloys using FEM simulation

On the mechanics of friction during the extrusion process

Temperature Changes and their Effect on Deformation during Extrusion using FEM

The effect of the initial rolling temperature on the microstructure evolution during and after hot rolling of AA6082

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Investigation and Comparison of Heat Transfers Analysis Used in Commercial FEM for Metal Forming

Materials Science Forum, 2013

During an Aluminium extrusion process, the extrusion parameters, i.e. friction, heat transfer, et... more During an Aluminium extrusion process, the extrusion parameters, i.e. friction, heat transfer, etc. are significantly influence by the temperature gradients produced in the billet during transfer to the container and after upsetting the container. The heat transfer at the tool/billet interface governs the temperature profile throughout the billet and tools during extrusion and consequently has a critical influence on the results. Although FEM technique offers great potential, care must be taken when applying the analysis to the hot extrusion of rate sensitive alloys. The most useful approach of an FEM simulation would thus be to include both the tooling and the billet in the calculation as discretised meshes. Because of the occurrence of the conductive and convective heat transfer, the deformation during hot extrusion is not adiabatic and estimation of the temperature increase is alloy dependent. The aim of this paper is to investigate and to compare how commercial FEM codes assign ...

Mobile Web 2.0 Integration

International Journal of Handheld Computing Research, 2013

Web 2.0 tools provide a wide variety of collaboration and communication tools that can be appropr... more Web 2.0 tools provide a wide variety of collaboration and communication tools that can be appropriated within education to facilitate student-generated learning contexts and sharing student-generated content as key elements of social constructivist learning environments or Pedagogy 2.0. “Social software allows students to participate in distributed research communities that extend spatially beyond their classroom and school, temporally beyond a particular class session or term, and technologically beyond the tools and resources that the school makes available to the students.” (Mejias, 2006, p1). This paper illustrates this by describing and evaluating the impact of the introduction of web 2.0 and mlearning to facilitate student eportfolios within the context of a first year Bachelor of Design and Visual Arts course in New Zealand (Unitec). Core web 2.0 (social software) tools used in establishing students’ web 2.0 eportfolios included: Vox, Qik, Picasaweb, Prezi, Google Docs, and Y...

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Using Smartphones and Mobile Web 2.0 to Create a Mobile Computing Platform for Tertiary Education

Today's smartphones are mobile multimedia computers, in Nokia's words: "It's what computers have ... more Today's smartphones are mobile multimedia computers, in Nokia's words: "It's what computers have become". Smartphone manufacturers have seen the potential to partner with online social software (Web2.0) sites (e.g. Flickr, YouTube, Vox, Ovi etc…) to produce a mobile computing platform to capture and share our daily lives with friends and family, anywhere, anytime. These tools can be utilized within tertiary education to create context independent collaborative learning environments. Pedagogical design of learning experiences using mobile web2.0 allows a tutor to create rich learning environments for students beyond the classroom or lecture theatre. This paper illustrates this by analysing students responses to a third year Product Design project that transformed a traditionally paper-based learning journal into an interactive, collaborative, online eportfolio using mobile web2.0 technologies facilitating an explicit social constructivist pedagogy. Students were provided with a Nokia N95 smartphone, a bluetooth folding keyboard, and a 1GB 3G data account. They created an online eportfolio, and used the smartphones to capture and record learning events and ideas from a variety of contexts. The learning outcomes included the development of a far more media rich and critically reflective collaborative experience than was previously possible using traditional approaches.

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An Mlearning Journey: Critical Incidents in Transforming Pedagogy

ABSTRACT Blogs, wikis, Youtube, PODCasts, Social Networking (e.g MySpace, Facebook) and more rece... more ABSTRACT Blogs, wikis, Youtube, PODCasts, Social Networking (e.g MySpace, Facebook) and more recently Twitter have been the latest crazes to attract the attention of many of today’s internet savvy younger generation. This generation are becoming our tertiary students. The emergence of these web 2.0 (or Social Software) tools has provided a media rich, yet simple to use, end user empowering environments that resonate with social constructivist pedagogies. Utilising these tools within tertiary education is one way to engage today’s students. The appropriation of web 2.0 tools within social constructivist learning environments has been nick-named ‘Pedagogy 2.0’ (C. McLoughlin &amp; M. Lee, 2008; C. McLoughlin &amp; M. J. W. Lee, 2008). However, less than a billion people have access to computers, whereas around four billion people have access to mobile phones. Most web 2.0 tools are also designed to be mobile friendly, allowing reading and updating of web 2.0 content from mobile phones, and also featuring enhanced mobile affordances such as photo and video blogging (from cameraphones), and geotagging (from GPS equipped smartphones). Hence mobile web 2.0 provides a platform for wider access that is context independent, facilitating ‘authentic’ learning environments (A. Herrington &amp; Herrington, 2007, 2006; J. Herrington, Herrington, Mantei, Olney, &amp; Ferry, 2009) beyond the boundaries of the traditional tertiary classroom. Thus mobile learning (mlearning) presents vast potential for appropriation within tertiary education. This paper presents an academics journey into the use and appropriation of mlearning within their teaching practice. This journey is based upon a four year research project into the potential of mobile web 2.0 (Cochrane, Flitta, &amp; Bateman, 2009). Critical incidents along this journey are identified and examples given of how mobile web 2.0 has been integrated into a Bachelor of Product Design course as a result of this journey. Examples of mobile web 2.0 scenarios are given, along with student and lecturer feedback. Lessons learnt during this mlearning journey will provide valuable insight to other educators wishing to explore these emerging tools within social constructivist learning. References: Cochrane, T., Flitta, I., &amp; Bateman, R. (2009). Facilitating Social Constructivist Learning Environments for Product Design Students Using Social Software (Web2) and Wireless Mobile Devices. [Journal]. DESIGN Principles and Practices: An International Journal, 3(1), 15pp. Herrington, A., &amp; Herrington, J. (2007). Authentic mobile learning in higher education. Paper presented at the AARE 2007 International Educational Research Conference, Fremantle, Australia. Herrington, A., &amp; Herrington, J. (Eds.). (2006). Authentic learning environments in higher education. Hershy: Information Science Publishing. Herrington, J., Herrington, A., Mantei, J., Olney, I., &amp; Ferry, B. (Eds.). (2009). New Technologies, new pedagogies: Mobile learning in higher education. Wollongong: Faculty of Education, University of Wollongong. McLoughlin, C., &amp; Lee, M. (2008). Mapping the digital terrain: New media and social software as catalysts for pedagogical change. Paper presented at the ASCILITE Melbourne 2008, Deakin University, Melbourne. McLoughlin, C., &amp; Lee, M. J. W. (2008). Future Learning Landscapes: Transforming Pedagogy through Social Software. Innovate: Journal of Online Education, 4(5).

Prediction of Substructure Influencing Static Recrystalisation Using FEM Analysis

ABSTRACT Static recrystallisation has a significant influence on many of the properties of the ex... more ABSTRACT Static recrystallisation has a significant influence on many of the properties of the extrudate and since the final microstructure controls the properties of extrudate, it is essential to predict these variations occurring during the processing of the material. This paper outlines the method used to predict such as properties using a physical model based on dislocation density. FEM analysis is used to predict the development of the structure during the extrusion process. The evolution of the substructure influencing static recrystalisation is studied. The metallurgical behaviour of axi-symmetric extrusion and that of shape extrusion are compared and results are presented.

Effect of pressure and temperature variations on FEM prediction of deformation during extrusion

Materials Science and Technology - MATER SCI TECHNOL, 2005

The extrusion process is complex, involving interaction between the process variables and the mat... more The extrusion process is complex, involving interaction between the process variables and the material's high temperature properties and is typically conducted at relatively high temperatures because the lower flow stress of the material permits larger section reductions to be achieved. This lowers the power requirements and processing times. Temperature is, perhaps, the most important parameter in extrusion. The flow stress is reduced if the temperature is increased and deformation is, therefore, easier, but at the same time, the maximum extrusion speed is reduced because localised temperatures must be well below any incipient melting temperature. The present investigation focuses on the evolution of the temperature in the billet from upsetting and until the end of the extrusion cycle is reached. The extrusion pressure and the temperature rise are predicted and the pressure-displacement trace and the events which take place in the deformed material during the extrusion process are also simulated. The simulation is compared with data obtained from an experimental extrusion press. All simulations are performed with the implicit finite element code FORGE2. A comparison with experiments is made to validate the predicted temperatures readings from FORGE2 to ensure that the numerical discretisation provides a true simulation of the process. It was found that the extrusion parameters (friction, heat transfer, etc.) are significantly influenced by the temperature gradients produced in the billet during transfer to the container, and after upsetting in the container. These parameters are thus clearly extremely sensitive input data when attempting to simulate the extrusion process.

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Comparison of experimental and Finite Element Modelling of the extrusion of AA6082 on both tools and extrudate as a function of process parameters

by Christof Sommitsch, S. Mitsche, and Isaac Flitta

International Journal of Material Forming, 2008

This paper deals with an integral finite element model (FEM) for the extrusion of AA6082. The tem... more This paper deals with an integral finite element model (FEM) for the extrusion of AA6082. The temperature history of extrudate and tools as well as the microstructure evolution of the aluminium alloy is calculated. An experimental extrusion plant with instrumented container and die was constructed to perform tests in order to validate the FEM model at different process conditions. The comparison with experiments was made to assess the relative importance of some extrusion parameters in the extrusion process and to ensure that the numerical discretisation yields a realistic simulation of the process. The influence of different process parameters on the microstructure is also given.

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FEM analysis to predict development of structure during extrusion and subsequent solution soak cycle

Materials which form the surface and subcutaneous layers of an extrudate experience large deforma... more Materials which form the surface and subcutaneous layers of an extrudate experience large
deformations when they traverse the die land, which, added to the inhomogeneous caused by the
dead metal zone, leads to considerable modifications to the deformation parameters when
compared with the remainder of the extrusion. The distribution of structure is therefore greatly
inhomogeneous. Reference to both empirical and physical models of the recrystallisation process
indicates that nucleation and growth will differ at these locations in those alloys that are usually
solution treated and aged subsequent to the deformation process. Since static recrystallisation
(SRX) has a significant influence on many of the properties of the extrudate, it is therefore
essential to provide the methodology to predict these variations. In the present work, a physical
model based on dislocation density, subgrain size and misorientation is modified and integrated
into the commercial FEM codes, FORGE2 and FORGE3 to study the changes of the
microstructure. Axisymmetrical and shape extrusion are presented as examples. The evolution
of the substructure influencing SRX is studied. The metallurgical behaviours of axisymmetric
extrusion and that of shape extrusion are compared. The predicted results show an agreement
with the experimental measurement. The distribution of equivalent strain, temperature
compensated strain rate and temperatures is also presented to aid in interpretation.
Importantly the properties of hard alloys improve with the increase in the temperature of the
extrusion. This phenomenon is discussed and theoretically justified.

$Table 2 Simulation runs The authors will now investigate the use of the physical definitions by the use of a two-dimensional simulation (i.e. rod extrusion) in order to confirm that the model may be validated to predict the form of the microstructure. The results presented will be the sub- grain size, the recrystallised grain size and the volume fraction recrystallised. Texture could be assessed but this is of somewhat secondary importance at least in this application. At the present time the authors are unable to predict the location of pockets of subgrains which will initially have to be approached by statistical methods. The problems involved with the temperature dependence of C/MgGp may be overcome by recognising that provid- ing a value of Mgp at temperature T; may be assumed then the value at any other temperature 7> is MopEXP{[AH(T2—T;)|/[(G)T2T;]}. However the acti- vation energy for grain boundary migration has not where T termed the shear strength, m is the friction coefficient; in effect a percentage of that which would$

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Material flow during the extrusion of simple and complex cross-sections using FEM

Materials science and technology, Jan 1, 2005

This paper deals with the extrusion of rod and shape sections and uses a 3D finite element model ... more This paper deals with the extrusion of rod and shape sections and uses a 3D finite element model analysis (FEM) to predict the effect of die geometry on maximum extrusion load. A description of material flow in the container is considered in more detail for rod and shape sections in order to fully comprehend the transient conditions occurring during the process cycle. A comparison with experiments is made to assess the relative importance of some extrusion parameters in the extrusion process and to ensure that the numerical discretisation yields a realistic simulation of the process. The usefulness and the limitation of FEM are discussed when modelling complex shapes. Results are presented for velocity contours and shear stress distribution during the extrusion process. It is shown that for most of the shapes investigated, the material making up the extrudate cross-sections originates from differing regions of virgin material within the billet. The outside surface of the extrudate originates from the material moving along the dead metal zone (DMZ) and the core of the extrudate from the central deformation zone. The FE program appears to predict all the major characteristics of the flow observed macroscopically.

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FEM analysis to predict development of structure during extrusion and subsequent solution soak cycle

Materials science and …, Jan 1, 2007

Materials which form the surface and subcutaneous layers of an extrudate experience large deforma... more Materials which form the surface and subcutaneous layers of an extrudate experience large deformations when they traverse the die land, which, added to the inhomogeneous caused by the dead metal zone, leads to considerable modifications to the deformation parameters when compared with the remainder of the extrusion. The distribution of structure is therefore greatly inhomogeneous. Reference to both empirical and physical models of the recrystallisation process indicates that nucleation and growth will differ at these locations in those alloys that are usually solution treated and aged subsequent to the deformation process. Since static recrystallisation (SRX) has a significant influence on many of the properties of the extrudate, it is therefore essential to provide the methodology to predict these variations. In the present work, a physical model based on dislocation density, subgrain size and misorientation is modified and integrated into the commercial FEM codes, FORGE2 and FORGE3 to study the changes of the microstructure. Axisymmetrical and shape extrusion are presented as examples. The evolution of the substructure influencing SRX is studied. The metallurgical behaviours of axisymmetric extrusion and that of shape extrusion are compared. The predicted results show an agreement with the experimental measurement. The distribution of equivalent strain, temperature compensated strain rate and temperatures is also presented to aid in interpretation. Importantly the properties of hard alloys improve with the increase in the temperature of the extrusion. This phenomenon is discussed and theoretically justified.

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Nature of friction in the extrusion process and its effect on material flow

Materials Science and Technology, Jan 1, 2003

This investigation focuses on simulation of the extrusion process and in particular the effect of... more This investigation focuses on simulation of the extrusion process and in particular the effect of the initial billet temperature on friction and its consequences on material ow. The simulation is compared with data obtained from an experimental extrusion press. All the simulations are performed with the implicit nite element codes FORGE2 and FORGE3. The effect of the initial billet temperature on the deformation zone pattern and its consequent effect on friction using both numerical simulation and experimental work are presented. A comparison with experiments is made to assess the relative importance of some extrusion parameters in the extrusion process and to ensure that the numerical discretisation provided a true simulation of the process. A speci c functional relationship to directly measure interfacial friction under conditions approaching those encountered in the quasi-static deformation process is described. The results revealed that the friction factor increases with increase in initial billet temperature and varies from 0 . 65 at 300°C to a 0 . 91 at 450°C after reaching the peak pressure. The dead metal zone is observed to vary in form and has a greater volume at high temperatures. The increase in friction results in an increase of initial extrusion load. The nite element program appears to predict all the major characteristics of the ow observed macroscopically.

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