Structure and mechanical properties of asymmetrically rolled IF steel sheet

As-received hot-rolled 5.6 mm thick IF steel sheet was symmetrically/ asymmetrically cold rolled at room temperature down to 1.9 mm. The asymmetric rolling was carried out in monotonic (an idle roll is always on the same side of the sheet) and reversal (the sheet was turned 180° around the rolling direction between passes) modes. Microstructure, texture and mechanical properties were analysed. The observed differences in structure and mechanical properties were modest, and therefore further investigation of the effects of other kinds of asymmetry is suggested.

MAAGs: the next generation. A study of the development of medical audit advisory groups and the arrangements for supporting clinical audit in primary care

Background: MAAGs have, historically, been disparate organisations with a lack of central direction, albeit with the same goal: to develop and support the performance of audit in primary care. This goal has been (and is being) achieved in a number of ways all over the country. In the last two years, MAAGs have witnessed many changes in primary care and are adapting themselves to suit these new arrangements at a local level.

Aim: To formalise our knowledge of where MAAGs are going, how they are getting there and the support they are receiving.

Method: A postal questionnaire to the 104 MAAGs in England and Wales, addressing 6 main issues of relevance to the development of MAAGs and the support they are receiving.

Results: At least two MAAGs have dissolved, leaving a possible total of 102 still in existence. Of these, 76 (74.5%) responded to the survey. The composition of the MAAG committee has changed dramatically since the inception of MAAGs in 1990, and staffing levels appear to have risen substantially. MAAGs appear to be more adequately funded by their health authorities than has previously been reported and many are actively seeking additional sources of funding. There is still large variation in levels of MAAG funding. Furthermore, funding is unrelated to the number of GPs or practices served. Security for MAAG staff appears to have been addressed in many areas, with 84% of MAAGs having at least one member of staff on a permanent employment contract. Many MAAGs are developing rolling programmes in an attempt to eliminate the short-sighted approach to the development of clinical audit that has existed since MAAGs were first set up.

Conclusion: Many MAAGs (with the obvious exception of those that have been dissolved) appear to be thriving without central direction or initiative. It is now evident that we were a little hasty in our concerns for the future of MAAGs beyond April 1996. It would seem that many organisations have taken the situation which arose two years ago as an opportunity to grow and develop in ways that may not have been possible within the confines of the Health Circular.

Local laser heat treatment in dual-phase steels

This research deals with processes leading to local strengthening effects in hot-rolled dual-phase (DP) steels. For this purpose, a method was investigated to achieve local strengthening, namely, local laser heat treatment (LHT). DP sheet steels were globally and homogenously deformed with different degrees of prestrains by cold rolling and subsequently locally heat treated by laser. Following this treatment with selected parameters, the microstructure of the surface and cross section of the heat-treated area as well as the mechanical properties were evaluated by light optical microscopy (LOM), scanning electron microscopy (SEM), as well as transmission electron microscopy (TEM), hardness measurement, and tensile testing. It can be stated that with partial heat treatment, local high strengthening can be produced. At lower heat treating temperatures, this effect could be attributed to bake hardening (BH). Increasing the prestrain as well as temperature results in improving the local properties. With increased heat treating temperature, the initial microstructure near the surface is affected. Partial strengthening of DP steels by laser can open up new fields of application for locally using the strengthening effect to only influence relevant areas of interest, thus providing the potential for saving energy and designed the component's behavior.

Adaptive cruise control look-ahead system for energy management of vehicles

Cruise control in motor vehicles enhances safe and efficient driving by maintaining a constant speed at a preset level. Adaptive Cruise Control (ACC) is the latest development in cruise control. It controls engine throttle position and braking to maintain a safe distance behind a vehicle in front by responding to the speed of this vehicle, thus providing a safer and more relaxing driving environment. ACC can be further developed by including the look-ahead method of predicting environmental factors such as wind speed and road slope. The conventional analytical control methods for adaptive cruise control can generate good results; however they are difficult to design and computationally expensive. In order to achieve a robust, less computationally expensive, and at the same time more natural human-like speed control, intelligent control techniques can be used. This paper presents an Adaptive Neuro-Fuzzy Inference System (ANFIS) based on ACC systems that reduces the energy consumption of the vehicle and improves its efficiency. The Adaptive Cruise Control Look-Ahead (ACC-LA) system works as follows: It calculates the energy consumption of the vehicle under combined dynamic loads like wind drag, slope, kinetic energy and rolling friction using road data, and it includes a look-ahead strategy to predict the future road slope. The cruise control system adaptively controls the vehicle speed based on the preset speed and the predicted future slope information. By using the ANFIS method, the ACC-LA is made adaptive under different road conditions (slope angle and wind direction and speed). The vehicle was tested using the adaptive cruise control look-ahead energy management system, the results compared with the vehicle running the same test but without the adaptive cruise control look-ahead energy management system. The evaluation outcome indicates that the vehicle speed was efficiently controlled through the look-ahead methodology based upon the driving cycle, and that the average fuel consumption was reduced by 3%.

Compressive properties of hot-rolled Mg-Zr-Ca alloys for biomedical applications

This paper investigated the microstructures and compressive properties of hot-rolled Mg-Zr-Ca alloys for biomedical applications. The microstructures of the Mg-Zr-Ca alloys were examined by X-ray diffraction analysis and optical microscopy, and the compressive properties were determined from compressive tests. The experimental results indicate that the hot-rolled Mg-Zr-Ca alloys with 1% Ca are composed of one single α phase and those alloys with 2% Ca consist of both Mg2Ca and α phase. The hot-rolled Mg-Zr-Ca alloys exhibit typical elongated microstructures with obvious fibrous stripe, and have much higher compressive strength and lower compressive modulus than pure Mg. All the studied alloys have much higher compressive yield strength than the human bone (90~140 MPa) and comparable modulus with the human bone, suggesting that they have a great potential to be good candidates for biomedical applications.

Effect of grain size on corrosion of high purity aluminium

A complete understanding of how grain refinement, grain size, and processing affect the corrosion resistance of different alloys has not yet been fully developed. Determining a definitive 'grain size-corrosion resistance' relationship, if one exists, is inherently complex as the processing needed to achieve grain refinement also imparts other changes to the microstructure (such as texture, internal stress, and impurity segregation). This work evaluates how variation in grain size and processing impact the corrosion resistance of high purity aluminium. Aluminium samples with a range of grain sizes, from ∼100 μm to ∼2000 μm, were produced using different processing routes, including cold rolling, cryo rolling, equal channel angular pressing, and surface mechanical attrition treatment. Evaluation of all the samples studied revealed a tendency for corrosion rate to decrease as grain size decreases. This suggests that a Hall-Petch type relationship may exist for corrosion rate and grain size. This phenomenon, discussed in the context of grain refinement and processing, reveals several interesting and fundamental relationships.

Effect of thermo-mechanical processing on precipitate formation in next generation HSLA steel

Development of advanced high strength steels (AHSS) using a conventional rolling setup is one of the biggest challenges to steel industry. It has been found that fine precipitation in a soft matrix, formed after hot rolling, can markedly improve the mechanical properties. In this work, three dimensional atom probe tomography (3D-APT) has been used to study the formation of precipitates in thermomechanically simulated steel. 3D-APT data reveals co-existence of numerous nano clusters with precipitates. Also, quantitative analysis of the nano clusters and precipitates shows clusters are as small as mm in size. Precipitates are found to be disc shaped with the composition of equilibrium precipitates (TiMo)C. Thus, 3D-APT is seen as an ideal technique to complement TEM to understand the nanoscale features in thermomechanically processed steel for further improvements in the mechanical properties of AHSS.

Infrequent item mining in multiple data streams

The problem of extracting infrequent patterns from streams and building associations between these patterns is becoming increasingly relevant today as many events of interest such as attacks in network data or unusual stories in news data occur rarely. The complexity of the problem is compounded when a system is required to deal with data from multiple streams. To address these problems, we present a framework that combines the time based association mining with a pyramidal structure that allows a rolling analysis of the stream and maintains a synopsis of the data without requiring increasing memory resources. We apply the algorithms and show the usefulness of the techniques. © 2007 Crown Copyright.

Microstructural response of nanocrystalline Al to cyclic loading

The data is derived from an investigation into the microstructural changes of nanostructure Al (produced by cryo-rolling) in response to cyclic loading using electron microscopy and EBSD. The aim is to develop a better understanding of the deformation mechanisms in ultrafine grained/nanostructure metals under cyclic loading conditions.

Effect of Zn concentration and grain size on prismatic slip in Mg-Zn binary alloys

Mg-Zn binary alloys with concentrations between 0 and 2.8wt% Zn have been prepared and processed via hot rolling and annealing to produce specimens with a strong basal texture and a range of grain sizes. These have been deformed in tension, a condition in which the deformation is dominated by prismatic slip. This data has been used to assess the Hall-Petch parameter as a function of Zn concentration for deformation dominated by prismatic slip. Pure magnesium showed non-linear Hall-Petch behaviour at large grain sizes, and this is compared to the values for prismatic slip measured on single crystals. The differences between critical resolved shear stress measurements made through single crystal, polycrystal and mathematical modelling techniques are also discussed.

Microstructures, mechanical properties and in vitro corrosion behaviour of biodegradable Mg-Zr-Ca alloys

The microstructures, mechanical properties, corrosion behaviour and biocompatibility of the Mg-Zr-Ca alloys have been investigated for potential use in orthopaedic applications. The microstructures of the alloys were examined using X-ray diffraction analysis, optical microscopy and scanning electron microscopy. The mechanical properties of Mg-Zr-Ca alloys were determined from compressive tests. The corrosion behaviour has been investigated using an immersion test and electrochemical measurement. The biocompatibility was evaluated by cell growth factor using osteoblast-like SaOS2 cell. The experimental results indicate that the hot-rolled Mg-Zr-Ca alloys exhibit much finer microstructures than the as-cast Mg-Zr-Ca alloys which show coarse microstructures. The compressive strength of the hot-rolled alloys is much higher than that of the as-cast alloys and the human bone, which would offer appropriate mechanical properties for orthopaedic applications. The corrosion resistance of the alloys can be enhanced significantly by hot-rolling process. Hot-rolled Mg-0.5Zr-1Ca alloy (wt %) exhibits the lowest corrosion rate among all alloys studied in this paper. The hot-rolled Mg-0.5Zr-1Ca and Mg-1Zr-1Ca alloys exhibit better biocompatibility than other studied alloys and possess advanced mechanical properties, corrosion resistance and biocompatibility, suggesting that they have a great potential to be good candidates for orthopaedic applications. © 2012 Springer Science+Business Media New York.

Effect of roller leveling on the bending behaviour of aged steel strip

The common grades of steel used in roll forming are: hot rolled carbon steel, high strength low alloy and recovery annealed cold rolled sheet. These steels are prone to ageing and are often skin passed and/or roller leveled to eliminate ageing as it can lead to problems in forming. In roll forming, shape defects such as bow, twist and camber are considered to be related to very small plastic strains in the longitudinal direction and hence knowledge of the material properties in the elastic plastic transition range is necessary if the process is to be modelled accurately. Previous studies with aluminium have indicated that skin pass rolling can lead to residual stresses in the strip. In this work, the study was extended to aged carbon steel and to the effect of roller leveling on both aged material and strip that had been given a light cold rolling to simulate a skin pass treatment. The results suggest that roller leveling reduced the magnitude of residual stresses resulting from skin pass rolling.

The significant differences observed between tensile and bending test results, at and near, the elastic plastic transition reinforces the need to consider bending properties when assessing the effect of prior processing on strip for roll forming.

Roll forming cryo-rolled nano-structured aluminium sheet

Commercial purity aluminium plate was reduced by rolling under nitrogen in 30 passes from an initial material thickness of 10 mm to a final thickness of 2 mm (80% reduction). Analysis of the microstructure showed that the material produced in this way had an ul-trafine grained microstructure. The sheet was roll formed at room temperature to a V-section using commercial roll forming equipment. Two sets of experiments were per-formed; one with a 15 mm radius in the base of the V and the other with a 5 mm radius. The performance in terms of final shape and springback is compared with the same part shape formed by V-die bending. The mechanical properties of the sheet were determined using the tensile test. It has been found that even if the total tensile elongation is close to zero and bending of the material is very limited, ultra-fine grained and low ductile sheet metals can be roll formed to simple section shapes.