Fatigue Failure Modes in Self-Piercing Riveted Aluminium Alloy Joints

Self-piercing riveting, as an alternative joining method to spot-welding, has attracted considerable interest from the automotive industry and has been widely used in aluminium intensive vehicles. One of the important factors that need to be considered is the effect of cyclic loading in service, leading to possible fatigue failure. The previous work reported in the public domain on the behaviour of self-piercing rivets has mainly focused on static tests. The work which is reported in this paper is concerned with the fatigue behaviour of single-rivet joints, joining two 2mm 5754 aluminium alloy sheets. The investigation also examined the effect of interfacial conditions on the fatigue behaviour. A number of fatigue failure mechanisms were observed based on rivet fracture, sheet fracture and combinations of these. The investigation has shown that they were dependent on the applied load and the sheet surface condition. Three-parameter Weibull analysis, using Reliasoft Weibull ++5.0 software, was conducted to analyse the experimental results. The analysis enabled the prediction of early-type failure (infant mortality failure) and wear-out failure patterns depending on the condition of the self-piercing riveted joints and the alloy sheet surface.

Computational Characterization of Passive Fluid Mixing in Microfluidics

In this work we computationally characterize fluid mixing in a number of passive microfluidic mixers. Generally, in order to systematically study and characterize mixing in realistic fluid systems we (1) compute the fluid flow in the systems by solving the stationary three-dimensional Navier-Stokes equations or Stokes equations with a finite element method, and (2) compute various measures indicating the degree of mixing based on concepts from dynamical systems theory, i.e., the sensitive dependence on initial conditions and mixing variance.

A Task Based Approach to Mechatronic Systems Education

This paper describes an elective course in mechatronic systems engineering that is project based and team-oriented with hands-on learning. Working in small teams, students add electronic components to a mobile robot base and write the programs required to make the robot perform a series of tasks. Although the application of mobile robots as an educational tool in a mechatronics course is becoming the norm at many universities, the task based organization of the Queen’s mechatronics course is believed to have a number of novel features. The paper will review the pedagogy of the course, including aspects of the student workload, the interplay between teams, and the task based approach to marking and organization of the laboratories.

Requirements Capture for Inclusive Design Resources and Tools

In the past twenty years, a number of resources and tools to support inclusive design have been developed. However, the impact of these resources and tools on industry is not evident — few industrialists have been using them in practice. Investigations into industry have identified unmet needs, for example, the lack of appropriate user data relating to inclusive design. The fundamental problem is that few resources and tools have been developed based on rigorous requirements capture. In fact, many of them were developed only because the developers think the information could be useful. It is essential to prepare a detailed requirements list when clarifying the task at the product planning stage. This is also true for developing resources and tools for inclusive design. Requirements capture plays an important role in identifying real needs from users and developing appropriate methods of support for them. This paper starts with a survey of available resources and tools for inclusive design, and a discussion on their merits and deficiencies in respect to industry application. A number of methods are employed for the requirements capture for an inclusive design toolkit, which leads to a consistent result. An outline of the toolkit is also presented.

Improvement Geometrical Precision in Sheet Incremental Forming Processes

Incremental forming is nowadays increasing its presence in industry as a new but interesting process, especially for production of small batches or unique components. Anyway, relevant efforts have to be spent in order to reduce the typical incremental forming processes drawbacks that risk to belittle the high advantages in terms of costs and simplicity. In fact, the process duration, usually equal to several minutes even if the operations are carried out on high speed numerical controlled units, and a certain tendency to produce no precise parts, can reduce industrial interest about incremental forming. A possible strategy to reduce the latter item is the design of modified trajectories able to take into account both the springback effects and the stiffness reduction due to the particular clamping equipment. In this paper the above introduced strategy is pursued integrating an on-line measuring system, based on a digital inspector, and a CNC open program. The actual geometry is acquired in some remarkable points and a compensation routine modifies the coordinates of the future punch path. The modification policy has been developed by using an effective FE code. An experimental verification shows the good potentiality of the suggested methodology.

Requirements for Remote Maintenance for Medical Wearable Devices

Telematics applications in the healthcare service are usually, abstractly equated with the telemedicine. In both cases, what this means is deploying the current information and communication technologies to arrive at a significant improvement of information flow between all facilities and persons engaged in the health maintenance, delivery and regeneration. By means of telemedicine, an effective, less expensive and more pleasant treatment in favour of the patient can be achieved.

Weld Contour Measurement of Fillet Weld by Reverse Engineering Technique

The external geometry of the fillet weld plays an important role in the strength of the weld. Two factors that influence the external geometry of the fillet weld are weld size and profile. The fillet weld must be made to the weld size and profile as specified in the welding code. Unacceptable profile not only is a defect of the weld but also produces stress risers that reduce the fatigue strength. Insufficient weld that reduces the cross sectional area of weld throat may cause premature failure. Visual inspection and weld gages are two most widely used simple tools to provide a rapid assessment of the external geometry of the fillet weld. In this study, the reverse engineering technique, which a laser scanning system integrates with CAD software, is used to provide a more accurate measurement of the weld contour. The weld samples were made of low-carbon steel plates with T-joint using CO2 welding. The weld volume, weld size and convexity were determined from CAD model to evaluate the weld quality. The reverse engineering technique provides a more accurate and efficient method to inspect the external geometry of fillet weld.

A Case Study in Healthcare Quality Management: A Practical Methodology for Auditing Total Patient X-Ray Dose During a Diagnostic Procedure

The healthcare industry is adopting many of the best practices familiar to the manufacturing sector. For example the need for ISO 9000 registration is now seen as an important business driver, indeed, BSI offers specific advice for Healthcare organisations seeking to gain ISO 9001:2000 approval. Accompanying the integration of quality systems into the healthcare business is the need to find practical measures of quality that may be used as part of an overall process to deliver improved performance. The manufacturing industry has a rich array of techniques such as JIT (Just In Time), 6 Sigma, SPC (Statistical Process Control), TQM (Total Quality Management) which may all now be found cited in conjunction with the healthcare industry. This paper focuses on the legislatively driven need to locally audit and minimise the diagnostic X-ray dose received by patients during a Barium Enema procedure. This procedure was selected as it has been shown by other authors to have a reasonably narrow spread of total patient dose levels and therefore might be relatively easy to draw statistically significant inferences for management purposes. The Ionising Radiation (Medical Exposure) Regulations 2000 (IRMER) and Health Service Circular on Clinical Governance (HSC1999/065) state that Clinical Audit should be performed to identify and monitor the issues leading to quality improvement and best practice. This is a statement of requirement, which delegates the responsibility of implementation to the local level. The IRMER Regulation also require the setting of local Diagnostic Reference Levels (DRLs). These are levels of radiation dose for individual examinations which under normal circumstances should not be exceeded. Producing a meaningful audit and DRLs in small departments raises many issues: data availability and capture may be time consuming especially if records are kept on paper-based systems; analysis of the data may present a steep learning curve in statistical techniques; a high degree of statistical confidence in the results is required along with sensitivity in their presentation and dissemination to ensure that they become part of a process of continuous improvement (rather than part of a blame culture). This paper presents a practical approach to delivering a meaningful audit of locally collected data using readily available software tools (Excel Spreadsheet), in conjunction with a relatively simple numerical statistical analysis technique called ‘bootstrapping’. Bootstrapping enabled us to set the local DRL for this procedure with an estimate of statistical confidence. An analysis was performed on the data to determine factors contributing to total patient dose.

On the Control of Dynamically Unstable Systems Using a Self Organizing Black Box Controller

Many systems are difficult to control by conventional means because of the complexity of the very fabric of their being. Some systems perform very well under some conditions and then burst into wild, maybe even chaotic, oscillations for no apparent reason. Such systems exist in bioreactors, electro-plating and other application domains. In these cases a model may not exist that can be trusted to accurately replicate the dynamics of the real-world system. BOXES is a well known methodology that learns to perform control maneuvers for dynamic systems with only cursory a priori knowledge of the mathematics of the system model. A limiting factor in the BOXES algorithm has always been the assignment of appropriate boundaries to subdivide each state variable into regions. In addition to suggesting a method of alleviating this weakness, the paper shows that the accumulated statistical data in near neighboring states may be a powerful agent in accelerating learning, and may eventually provide a possible evolution to self-organization.

Design and Analysis of Hemispherical Electrostatic Micro Deformable Focusing Mirror

For uniform deformation, based on bulk microfabrication with isotropic etching, two types of hemispherical electrostatic micro deformable focusing mirror are designed. One of the focusing mirrors is center-anchored, and the other is circular clamped. Using theory of shells, theoretical solution of deformation under uniform electrostatic force is derived. For more detail analysis of the electrostatic and elastic forces coupling problem, finite element is used to analyze the deformation of the mirror structure. Applying electrostatic force, the profile of micro focusing mirror will be not the spherical and change to become a curve like parabolic surface. Using least square method, the curve is fitted as a parabolic curve and the focal lengths of the focusing micro mirror are obtained. The result shows the focal length without applying electrostatic force can be determined by different micro mirror radius and isotropic etching depth. When the electrostatic forces are applied, the deformation and the focal length change differently between the two types of focusing mirror. For circular clamped micro mirror, the deformation is larger near circular clamped region and uniform in the center regime. Therefore, the relation of focal length and applying voltage is a concave curve with minimum values. That is, the focusing length decreasing as the applying voltage increasing and reaches a limit values. When the applying voltage continues increasing after reaching the minimum value, the focal length increases fast. It also shows the thicker structure layer needs larger applied voltage. But the focal length changes in larger stroke. The pull-in voltage is about 100 volt when the structure layer are both 2 μm. However, the pull-in voltage increases nonlinearly as gap increasing. When the gap increases to 4 μm, the pull-in voltage is about 300 volt. The result shows center-anchored micro mirror has better performance. The deformation is more uniform and the focal length increases nonlinearly as applied voltage increasing. It is found the stroke of focal length is larger and the applied voltage is less. The results shows even when the gap and structure layer is 4 and 2 μm, the pull-in voltage is about 62 volts. However, the stoke changes from 990 to about 1320 μm when applying voltage is from 0 to 60 volts. Therefore, with low applied voltage and large focal length stoke, the center-anchored micro mirror has good performance.