Peter Tiernan

Enhancing the learning experience of undergraduate technology students with LabVIEW TM software

Many universities and colleges, throughout the world, that deliver undergraduate programmes in science and engineering are currently incorporating virtual instruments as teaching, measurement and analysis tools for student learning. The aim of this study is to enhance the learning experience of undergraduate engineering students and stimulate their research interests by incorporating hands-on, hardware linked programming. The framework for the current research consisted of, initially, observing and recording the interest students showed in a graphical-based computer language for programming control and data acquisitions. Secondly, in the software laboratory sessions, the students were introduced to the concept of research activity and the use of computer software in such activity. LabVIEW(TM), an easy-to-use, interactive, graphical programming language that can be used to build virtual instruments was used in the current study. This software allows creation of sophisticated programs and applications in a shorter amount of time without needing an in-depth knowledge of computers or indeed programming languages. The methodology consisted of an introductory learning period for the LabVIEW(TM) programming language, followed by hands-on programming with a specific set of laboratory exercises aimed at solving typical industrial automation type problems. Finally the results of a detailed student questionnaire and created programs were analysed to establish the learning experiences. It was established that student experiences in designing and developing LabVIEW(TM) programs with associated hardware has hugely stimulated their interest and enthusiasm in the subject of industrial automation. Students acquired knowledge by direct experience, explored phenomena, visualized expected outcomes and experimented with possible solutions. Critically, the LabVIEW programming laboratory sessions undertaken during the course of this research has stimulate students interest in pursing further research at post-graduate level.

Biocidal effect and durability of nano-TiO2 coated textiles to combat hospital acquired infections

While antimicrobial textiles have received considerable interest and attention from both the scientific community and general consumers, there have been very few studies investigating the durability of such antimicrobial activities. In this study, we describe the modification of the surface of textiles that were modified with commercially available titanium dioxide (TiO2) powder (P25 Aeroxide®, Degussa™) using a sonochemical technique. The antibacterial activity of TiO2 can improve textile quality and effectively reduce the rate of infections acquired in hospitals. Medical garments produced from such fabrics may improve the patients recovery and revolutionize the textile market. This modification imparts biocidal properties to these textiles, which were then optimized to acquire properties of the textile. Samples were washed for 30 cycles at three different temperatures (40 °C, 60 °C and 90 °C) to test the durability of the bonding of the nanoparticles to textiles and the effectiveness was examined with respect to their antimicrobial activity against hospital pathogens: Escherichia coli, MRSA and Candida albicans. Samples surfaces were examined by a Scanning Electron Microscope equipped with Energy Dispersive X-ray Spectroscopy (SEM/EDS) for surface imaging. Atomic Absorption Spectrometry (AAS) was used as a technique to quantify the Ti present on the fabric. The best durability of TiO2 on textiles was best retained after washing at 40 °C. From an environmental point of view, the release of nanomaterial from textiles was acceptable against currently available benchmarks. We have investigated the adhesion of nanoparticles (NPs) to the textile surface. Medical garments, bed linens and upholstery produced from such fabrics may improve hospital hygiene against antibiotic resistant superbugs and help reduce hospital acquired infections.

Microstructural Modeling of P91 Martensitic Steel Under Uniaxial Loading Conditions

The changing face of power generation and the increasingly severe conditions experienced by power plant materials require an improved understanding of the deformation and failure response of power plant materials. Important insights can be obtained through computational studies, where the material microstructure is explicitly modeled. In such models, the physical mechanisms of deformation and damage can be represented at the microscale, providing a more accurate prediction of material performance. In this paper, two approaches are examined to represent the microstructure of a martensitic power plant steel (P91). In one approach, the model is based on a “measured microstructure” with electron backscatter diffraction (EBSD) employed to obtain the orientation of the martensitic grain structure of the steel. The alternative approach is to use a “numerically simulated” model where the microstructure is generated using the Voronoi tessellation method. In both cases, the microstructural model is incorporated within a representative volume element (RVE) in a finite-element analysis. The material constitutive response is represented by a nonlinear, rate dependent, finite strain crystal plasticity model, with the microstructural orientation specified at each finite-element integration point by the microstructural model. The predictions from the two approaches are compared. The stress distributions are observed to be very similar, though some differences are seen in the strain variation within the RVE. [DOI: 10.1115/1.4026028]

Experimental study on dieless drawing of Nickel-Titanium alloy.

The effect of a dieless drawing process on commercial grade Nickel-Titanium rods, of 5 mm diameter, was investigated by varying the established critical process parameters of temperature, cooling rate, drawing velocity, and heating/cooling velocity. The rods were successfully dieless drawn with a maximum steady state reduction in cross-sectional area of 54%. The thermal and mechanical loading profiles of the rod during processing, and the resulting changes in microstructure and hardness, have been investigated. Uniform levels of stress and strain resulted in uniform reduction of the rod cross-sectional area. The grain structure was highly deformed in the drawing direction and increased porosity was observed as a result of the process. The longitudinal section hardness of the rod was significantly reduced as a result of the dieless drawing process. Any failures that arose were due to discontinuities within the material microstructure caused by a high necking rate, shorter exposure time to the process temperature and low heating and cooling rates. A uniform oxidation layer was observed on the surface of the processed rods as a result of processing in atmospheric conditions. This oxidation layer has the potential to aid in the lubrication of subsequent cold working operations of the dieless drawn rods. Coupling the thermomechanical effects of the dieless drawing process with a cold drawing processing step has the potential to produce a NiTi wire in fewer passes, and therefore at a reduced cost.

Experimental and numerical analysis of the deformation in mild steel wire during dieless drawing

Abstract Dieless wire drawing is the process of causing a reduction in a wire diameter without the use of conventional wire drawing dies. The wire, axially loaded with a force, is heated to an elevated temperature to initiate plastic deformation. The mechanics of this novel drawing process and a theoretical analysis of the deformation are discussed in this paper. The results of an experimental drawing programme carried out with mild steel wire at temperatures between 400 and 900°C are also presented. Mathematical models were developed and used to describe and predict the process deformation and both the stress and temperature distribution profile along the workpiece. A machine was designed and manufactured to facilitate an experimental programme of dieless drawing. The machine permitted continuous drawing of wire, while the reduction ratio, drawing load and temperature were automatically controlled using a personal computer. A finite element (FE) model of the wire was developed, and the results obtained from the FE analysis show good agreement with those obtained from both the experimental work and the mathematical modelling. Results obtained confirm that a complicated interdependence of the process parameters exists during the dieless drawing process.

Deformation Characteristics of a High Chromium, Power Plant Steel at Elevated Temperatures

The changing face of power generation requires an improved understanding of the deformation and failure response of materials that are employed in power plants. Important insights can be obtained through microstructurally motivated modelling studies. With the drive for increased efficiency, there is a corresponding drive towards increasing operating temperatures in conventional power plant. With these increasing temperatures, and with the increased flexibility required of modern power plant working in a mixed energy economy, more robust material testing and modelling tools are required to accurately predict the response of power plant steels. This works deals with the development of a material model for a martensitic steel, P91, relevant to the range of temperatures typically seen in a modern power plant. High temperature (20, 400, 500, 600°C) tensile testing at various strain rates was carried out the steel. Tests were taken to failure and the stress strain response recorded. Electron backscatter diffraction (EBSD) is employed to determine the complex microstructure of the P91 material. This information is incorporated within a representative volume element (RVE) and a nonlinear, rate dependent, finite strain crystal plasticity model used to represent the deformation of the material. The material model was calibrated to each temperature and strain rate to give a robust physically based model that has been fully validated through experimental data.Copyright

The Role of Plasticity in the Transverse Lattice Strain Evolution of a Martensitic Steel

In this work, in-situ neutron diffraction measurements are performed for a martensitic steel in conjunction with crystal plasticity analysis. The results indicate that heterogeneous plastic contraction on transverse {200} grains is responsible for the observed nonlinear lattice strain evolution. The effect of slip properties on plastic contraction is computationally identified.

The Dieless Drawing of High Carbon Steel

This paper describes the elevated temperature testing of high and low carbon steels in the temperature range 500°-750°C and at strain rates of 3.3 x 10 -4 s -1 and 3.3 x 10 -3 s -1 . The purpose of the testing was to simulate testing conditions during dieless drawing such as the forces involved at elevated temperatures and the effects they have on the mechanical properties of the material such as tensile strength and engineering strain. The dieless drawing machine under construction consists of stepper motor driven ball-screws applying an axial load to the specimen and moving a band heater and cooling system along the specimen axis. Control of the process velocities and temperature allows diametrical control of the bar/wire to be achieved. The specimen on the dieless machine will be fixed at one end and axially loaded when a target temperature is reached, and when the yield strength is reached a local deformation is initiated. After a deformation increment the heating zone is moved toward the undeformed end of the bar/wire, while the cooling system decreases the temperature behind the heating zone and retards plastic flow at this position. Incremental movement of the heating/cooling zone means steady state conditions are achievable.

Probing Martensitic Transition in Nitinol Wire: A Comparison of X‐ray Diffraction and Other Techniques

Martensitic to austenite transformation in Nitinol wire can be measured by a number of techniques such as XRD (X‐Ray Diffraction), DSC (Differential Scanning Calorimetry), BFR (Bend and Free Recovery) and Vickers indentation recovery. A comparison of results from these varied characterisation techniques is reported here to obtain a greater understanding of the thermal‐elastic‐structural changes associated with martensitic transformation. The transformation temperatures measured by DSC were found to correspond well with the structural and mechanical information obtained from XRD, BFR and Vickers indent recovery methods. Indent recovery is a relatively new and accurate method of monitoring stress induced martensitic transformations in NiTi and is one of only a few methods of stress inducing martensitic transformation in large scale samples. It is especially useful for NiTi in the as‐cast billet form, where tensile testing is impossible. BFR is uniquely popular in the NiTi wire manufacturing sector and is recognised as the most accurate method of measuring the transformation temperature. Here the material is stressed to a representative in‐service stress level during the test. No other test uses the shape memory effect for measuring the transformation temperature of NiTi. The results show that the DSC thermogram and XRD diffractogram have a peak overlap which is a common occurrence in NiTi that has been extensively processed. The XRD method further explains the observations in the DSC thermogram and in combination they confirm the transformation temperature.

Looped ends versus open ends braided stent: A comparison of the mechanical behaviour using analytical and numerical methods

The present study has two major purposes: firstly, to investigate whether the analytical model proposed by Jedwab and Clerc for assessing the mechanical behaviour of an open ends metallic braided stent is applicable to the looped ends stent design and secondly, to compare the response of the two stent designs subjected to radial compression. We use finite element analysis to evaluate the performance of the two braided stents emulating well established designs: WALLSTENT and WallFlex. We validate the WALLSTENT model analytically. We perform a radial crimping simulation and evaluate the radial forces and stresses induced. This study confirms the validity of using the analytical model in the biomechanical analysis of the WALLSTENT design. However, in case of the WallFlex design, a major difference in the results can be observed in the levels of radial forces and wire peak stresses, justifying the decision of using a different alloy in the fabrication of the WallFlex design.