Microstructure and mechanical properties of thermomechanically processed TRIP steel

The strengthening mechanism responsible for the unique combination of ultimate tensile strength and elongation in a multiphase Fe-0.2C-1.5Mn-1.2Si-0.3Mo-0.6Al-0.02Nb (wt%) steel was studied. The microstructures with different volume fractions of polygonal ferrite, bainite and retained austenite were simulated by controlled thermomechanical processing. The interrupted tensile test was used to study the bainitic ferrite, retained austenite and polygonal ferrite behaviour as a function of plastic strain. X-ray analysis was used to characterise the volume fraction and carbon content of retained austenite. Transmission electron microscopy was utilised to analyse the effect of bainitic ferrite morphology on the strain induced transformation of retained austenite and retained austenite twinning as a function of strain in the bulk material. The study has shown that the austenite twinning mechanism is more preferable than the transformation induced plasticity (TRIP) mechanism during the early stages of deformation for a microstructure containing 15% polygonal ferrite, while the transformation induced plasticity effect is the main mechanism when there is 50% of polygonal ferrite in the microstructure. The bainitic ferrite morphology affects the deformation mode of retained austenite during straining. The polygonal ferrite behaviour during straining depends on dislocation substructure formed due to the deformation and the additional mobile dislocations caused by the TRIP effect. Operation of TRIP or twinning mechanisms depends not only on the chemical and mechanical stability of retained austenite, but also on the interaction of the phases during straining.

Effect of pre-straining and bake hardening on the microstructure and mechanical properties of CMnSi trip steels

The effects of pre-straining and bake hardening on the mechanical behaviour and microstructural changes were studied in two CMnSi TRansformation-Induced Plasticity (TRIP) steels with different microstructures after intercritical annealing. The TRIP steels before and after pre-straining and bake hardening were characterised by X-ray diffraction, optical microscopy, transmission electron microscopy, three dimensional atom probe and tensile tests. Both steels exhibited discontinuous yielding behaviour and a significant strength increase with some reduction in ductility after pre-straining and bake hardening treatment. The following main microstructural changes are responsible for the observed mechanical behaviours: a decrease in the volume fraction of retained austenite, an increase in the dislocation density and the formation of cell substructure in the polygonal ferrite, higher localized dislocation density in the polygonal ferrite regions adjacent to martensite or retained austenite, and the precipitation of fine iron carbides in bainite and martensite. The mechanism for the observed yield point phenomenon in both steels after treatment was analysed.

FEA comparison of high and low pressure tube hydroforming of TRIP steel

The increasing application of hydroforming for the production of automotive lightweight components is mainly due to the attainable advantages regarding part properties and improving technology of the forming equipment. However, the high pressure requirements during hydroforming decreases the costs benefit and make the part expensive. Another requirement of automotive industries is weight reduction and better crash performance. Thereby steel industries developed advanced high strength steels which have high strength, good formability and better crash performance. Even though the thickness of the sheet to form the component is reduced, the pressure requirement to form the part during expansion is still high during high pressure hydroforming. This paper details the comparison between high and low pressure tube hydroforming for the square cross-section geometry. It is determined that the internal pressure and die closing force required for low pressure tube hydroforming process is much less than that of high pressure tube hydroforming process. The stress and thickness distribution of the part during tube crushing were critically analysed. Further, the stress distribution and forming mode were studied in this paper. Also friction effect on both processes was discussed.

Microstructure and mechanical properties of thermomechanically processed TRansformation Induced Plasticity (TRIP) steels

One of the main aims of steel research for the automotive industry is to develop materials with the optimum combination of relevant properties, cost and productivity. The introduction of new TRansformation Induced Plasticity steels has been driven by the requirements to increase the ductility without compromising the strength. The main phenomenon responsible for the unique mechanical properties in these steels has been proposed to be the formation of multiphase structure, which can contribute to an increase in elongation during straining. The thesis studied the effect of the different alloying additions on the structure-property relationship in the TRIP steels.

Assessing the legitimacy of humanitarian intervention : purpose, authority and means

This study looked at military deployments that seek to promote human rights, including operations in Somalia, Rwanda and Kosovo. While a legitimate humanitarian purpose and international authority for these missions can be demonstrated, finding the appropriate means of action - or how to best conduct the operation - remains very difficult, ensuring similar future missions will remain controversial.

Springback behaviour of TRIP steels in sheet metal forming

Examines the methods for numerical modelling of the springback effect in TRansformation Induced Plasticity (TRIP) steels under conditions of various bending processes. It represents a largely unexplored part of the TRIP steel literature and therefore makes a valuable contribution toward a practical approach to predicting springback in TRIP steels.

Variant selection during the c-to-ab phase transformation in hot-rolled bainitic TRIP-aided steels

The variant selection phenomenon during the austenite to bainite phase transformation in hot-rolled TRIP-aided steels was quantitatively characterized at the level of individual austenite grains. The reconstruction of the electron backscatter diffraction maps provided evidence that bainite grows by packets of laths sharing a common {1 1 1}_y plane in the austenite. The affect of hot deformation is to reduce the number of packets that form. It is suggested that slip activity is important in understanding this effect.

Public policy and USM : an approach to fit a renewed sense of public purpose

Malaysian Higher educational reform is an important and central aspect of the broader Malaysian public policy focus on excellence, development and national growth. This proposed paper intends to discuss analyze and critique the APEX program for Malaysian Universities. In particular the paper will investigate and discuss the way Universiti Sains Malaysia has interpreted and developed its strategic goals in light of its award of APEX status. Specifically I intend to discuss the strengths and limitations of the Universiti Sains Malaysia agenda, and contextualize it within a broader discussion about the directions of Malaysian Higher Education, in conditions of globalization, network society, and the knowledge economy. The challenges faced by the reform agenda at USM are significant and it is important that any understanding of the USM agenda be informed by deep reflection on the underlying philosophical aims and justifications for its direction. In this way my paper will attempt to show how the USM project is both an important part of Malaysian national development and a critical response to contemporary globalization, while at the same time an innovative and challenging intervention into public policy debate in Higher Education. The values and objectives of USM in regards to its strategic reorientation have implications far beyond the Higher Education sector and these implications will also be discussed.

Addressing the basics : academics' views of the purpose of higher education

A number of changes have occurred in the higher education sector under the auspices of quality and quality improvement. Much of this change has resulted in a compliance-driven environment (more measures, more meetings, more form-filling and less time for the core activities of teaching and research). It is an environment that seeks to assure all and sundry of the quality of academic programs. Anecdotally, many academics are not convinced that the current systems do, indeed, assure quality. The reasons for this may be many and varied. One suggestion is that differences in perceptions about the purpose of higher education inevitably lead to differences in the definition of quality itself and consequently, differences in systems designed to assure that quality. Understanding what academics think about the purpose of higher education may provide some clues about how they consider quality should be defined.

In this research, the focus is on the views of academic accountants in Australia, defined as: academics whose main discipline area is accounting and who are involved in accounting education at an Australian university. The findings of this research show that the respondent group do, in fact, view the purpose of higher education currently promoted in their schools/departments differently from the purpose that they consider ought to be promoted. Such fundamental differences have the potential to influence the motivation and effectiveness of staff undertaking core activities in Australian universities. In addition, articulating the views of this important stakeholder group also has the potential to ensure that their views are considered in the discussions around purpose, quality and performance measures in higher education – all of which impact on the working lives of academic accountants in Australian universities.

The God of old : the role of the Lukan parables in the purpose of Luke's Gospel

Thesis comprises a study of the parables unique to the Third Gospel, aiming in particular to establish a link between Luke's choice of these parables and his overall purpose in writing.

Getting the real-time precise round-trip time for stepping stone detection

Stepping stone attacks are often used by network intruders to hide their identities. The Round Trip Times (RTT) between the send packets and corresponding echo packets for the connection chains of stepping stones are critical for detecting such attacks. In this paper, we propose a novel real-time RTT getting algorithm for stepping stones which is based on the estimation of the current RTT value. Our experiments show that it is far more precise than the previous real-time RTT getting algorithms. We also present the probability analysis which shows that our algorithm has a high matching rate and a high accurate rate.

Numerical simulations on warm forming of stainless steel with trip-effect

In steels with TRIP-effect, a phase transformation from the retained-austenite to martensite occurs during forming, and it significantly affects hardening behaviours. Such an effect is sensitive to the amount of strain as well as the temperature variation. For materials with a strong TRIP-effect, new forming techniques are needed to develop that can lead to lighter and stronger components in automotive industry. This paper presents a coupled thermo-mechanical finite element modelling and simulation of a warm deep drawing of austenitic stainless steel (including a TRIP-effect) using LS-DYNA and temperature effect on forming process of such materials is investigated.

The purpose of the PhD : theorising the skills acquired by students

In the past decade there has been a marked push for the development of employability skills to be part of the PhD process. This push is generally by stakeholders from above and outside the PhD process, i.e. government and industry, who view skills as a summative product of the PhD. In contrast, our study interviewed stakeholders inside the PhD process – twenty final‐year, full‐time Australian PhD students – to provide a bottom‐up perspective into the skills question. Using grounded theory procedures we theorise the skills students develop during the PhD as a formative developmental process of acquiring intellectual virtues. Drawing on Aristotelian theory, we propose that theorising the PhD as a process of acquiring intellectual virtues offers a more robust and conceptually richer framework for understanding students’ development during the PhD than the instrumental focus on skills evident in contemporary debates.