Terry Dickerson

Fatigue of friction stir welds in aluminium alloys that contain root flaws

Abstract Although the vast majority of friction stir welds will be free of flaws, it is not always possible to assume that they are. The properties of welds with flaws are needed to enhance confidence in the design and application of friction stir welded joints. The monotonic strength and fatigue behaviour of single-sided butt welds in 6–7 mm thick AA5083-O, AA5083-H321 and AA6082-T6, both without and with root flaws, was investigated. Examination of the root flaw faces showed that there was bonding between the flanks of the flaws but the bonding was of poor quality and incomplete. This meant that the strength and ductility of the flaws were lower than the surrounding material. However, the comparison of the mechanical test results suggests that root flaws up to a certain size are tolerable without a significant loss in performance when compared to nominally flaw-free welds. These data also suggest that even friction stir welds with root flaws exceed the design life for equivalent fusion welds set out in the draft Eurocode 9 and that a higher rating may be warranted. Limited test results produced for this work need to be supplemented with a wider range of tests.

Dissimilar friction stir welds in AA5083-AA6082. Part I: Process parameter effects on thermal history and weld properties

The aim of this study was to explore the so-called processing window, within which good-quality welds can be produced, for the friction stir welding of AA5083 to AA6082. To that end a systematic set of nine instrumented welds were made using rotation speeds of 280, 560, and 840 rpm and traverse speeds of 100, 200, and 300 mm/min with AA5083 on the advancing side and another nine with the materials reversed. For comparison a smaller series of AA5083-AA5083 and AA6082-AA6082 welds were also made. Thermocouple measurements, tool torque, extent of material mixing, and macrostructural observations all indicate that the temperature under the tool is more strongly dependent on the rotation than the traverse speed. It was found that in the current case, the power (energy/s) and heat input (energy/mm) do not correlate simply with the weld temperature. As a result, such metrics may not be suitable for characterizing the conditions under which welds are produced.

Prediction of Brittle Failure of Notched Graphite and Silicon Nitride Bars

High stress gradients occur at metal-to-ceramic joints due to the different thermal and mechanical properties of the materials. In some cases, the magnitude of the highly localized stresses lead to failure thus compromising the structural integrity of such joints. The study of notched ceramic bars with high stress gradients can assist with the prediction of failure of metal ceramic joints. Experiments and fracture mechanics analysis were performed on notched and un-notched POCO E.D.M 3 graphite and AS800 Silicon Nitride bars with different notch parameters. The twoparameter, multi-axial Weibull statistics method and a brittle fracture criterion based on the average stress over an area approach were used to predict the failure of the bars and the results obtained were compared with experimental results. The brittle failure criterion appears to give much better correlation with experimental results than the multi-axial Weibull statistics approach. The findings also appear to highlight the limitations of the Weibull’s statistics method in cases involving very high stress gradients.

Measurement and prediction of residual stresses in aluminium friction stir welds

Friction stir welding (FSW) is a solid-state process that offers the possibility of creating high quality joints between dissimilar aluminium alloys. However, to date little is known about the distribution of residual stresses within such joints. In this study, a combined modelling and experimental approach has been undertaken in an attempt to clarify this situation and develop a practical predictive tool. The model appears to have captured the asymmetry of the welding process but the peak residual strain is typically 30% higher than measured by synchrotron X-ray diffraction indicating that some optimisation is required.

Stakeholder challenges in purchasing medical devices for patient safety.

Objective This study identifies the stakeholders who have a role in medical device purchasing within the wider system of health-care delivery and reports on their particular challenges to promote patient safety during purchasing decisions. Methods Data was collected through observational work, participatory workshops, and semi-structured qualitative interviews, which were analyzed and coded. The study takes a systems-based and engineering design approach to the study. Five hospitals took part in this study, and the participants included maintenance, training, clinical end-users, finance, and risk departments. Results The main stakeholders for purchasing were identified to be staff from clinical engineering (Maintenance), device users (Clinical), device trainers (Training), and clinical governance for analyzing incidents involving devices (Risk). These stakeholders display varied characteristics in terms of interpretation of their own roles, competencies for selecting devices, awareness and use of resources for purchasing devices, and attitudes toward the purchasing process. The role of “clinical engineering” is seen by these stakeholders to be critical in mediating between training, technical, and financial stakeholders but not always recognized in practice. Conclusions The findings show that many device purchasing decisions are tackled in isolation, which is not optimal for decisions requiring knowledge that is currently distributed among different people within different departments. The challenges expressed relate to the wider system of care and equipment management, calling for a more systemic view of purchasing for medical devices.

A Case Study of Design Methods Applied to Researching Medical Device Purchasing Processes

Design and engineering concepts are increasingly welcomed by healthcare communities for developing products and environments. With the recognition of healthcare as a safetycritical industry, design processes can also be used to develop services, organisations, and management systems in healthcare. The case study reported on here forms part of a wider research study of medical device purchasing practice, and provides an example of applying systemic design methods to one healthcare context. Collaboration between the researchers and a hospital provided an opportunity to explore design approaches as part of the research process, in terms of data collection, analysis, synthesis, as well as in the implementation of new practices. The paper firstly gives justification for using design and systems approaches, and specifies the particular aspects of design approaches used, including a discussion on their applicability to the purchasing of medical devices. Design approaches used included diagramming methods, participatory design, and risk analyses techniques, which were used in conjunction with qualitative methods. A description of the techniques used with the collaborating hospital then follows, including some of the methodological challenges encountered. The case study shows a practical example of how design methods and tools can be used to research within a healthcare context, and is

Framework for Design Research in Health and Care Services

In England, services addressing the complex needs of people with learning disabilities by integrating health and social care are currently designed in an ad hoc fashion. A structured approach has the potential to address variable levels of service provision and quality as well as provide clarity about the purpose and boundaries of the services. A design process is a series of steps taken to develop a product or process from initial needs to final design specifications and implementation. Currently no structured design process for these complex health and care services exists. Based on a literature review and an extensive set of interviews and observations carried out in a learning disability service we suggest a research framework rooted in engineering design to develop an appropriate design process.

The Role of Inclusive Design in Improving People’s Access to Treatment for Back Pain

Inclusive Design is usually applied to consumer products and services; here we investigate if it can be applied to healthcare delivery services. Methods: A case study approach was used by applying Inclusive Design methods to a telephone ‘Physio-Direct’ service for patients with back pain. Online surveys and interviews with healthcare professionals were used to gather insight into the delivery of back pain care and to construct a task analysis of the patient care journey. The task analysis was used to estimate the service demand made on patients’ capabilities. Finally, an exclusion calculator was used to estimate the proportion of a population excluded from the service. Results: The surveys (n = 30) and interviews (n = 4) showed that communication difficulties, patients’ reduced capability, service misconceptions and difficulties in obtaining information were the main barriers, which prevented patients from accessing the service. Some tasks placed a high demand on the patients’ capabilities. These included telephone assessment, waiting for a telephone response, memorising the verbal advice, understanding the posted exercise leaflets and doing the exercises. It was estimated that at least 15% of the British population are excluded from the ‘Physio-Direct’ service. Conclusion: Inclusive Design methods were applied to the ‘Physio-Direct’ service and demand on its users identified ways in which the service could be improved. This suggests that Inclusive Design may be a useful tool in improving healthcare service delivery.

Understanding influences on the uptake of pulmonary rehabilitation in the East of England: an Inclusive Design/mixed-methods study protocol

Introduction 1.2 million people in the UK have chronic obstructive pulmonary disease (COPD) that causes breathlessness, difficulty with daily activities, infections and hospitalisation. Pulmonary rehabilitation (PR), a programme of supervised exercise and education, is recommended for patients with COPD. However, only 1 in 10 of those who need it receive PR. Also, the UK National COPD Audit Programme concluded that the COPD treatment might not be accessible to people with disabilities. This paper applies an Inclusive Design approach to community-based PR service provisions. It aims to inform improvements to the PR service by identifying barriers to the uptake of PR in the COPD care journey in relation to patients’ capabilities that can affect their access to PR. Methods and analysis The protocol includes four steps. Step 1 will involve interviews with healthcare professionals and patients to gather insight into their experiences and produce a hierarchical task analysis of the COPD care journeys. Step 2 will estimate the service exclusion: the demand of every task on patients’ capabilities will be rated by predefined scales, and the proportion of the population excluded from the service will be estimated by an exclusion calculator. Step 3 will identify the challenges of the PR service; a framework analysis will guide the data analysis of the interviews and care journey. Step 4 will propose recommendations to help patients manage their COPD care informed by the challenges identified in step 3 and refine recommendations through interviews and focus groups. Ethics and dissemination The Cambridge Central Research Ethics Committee gave the study protocol a positive ethical opinion (17/EE/0136). Study results will be disseminated through peer-reviewed journals, conferences and the British Lung Foundation networks. They will also be fed into a Research for Patient Benefit project on increasing the referral and uptake of PR.

Interventions to increase referral to and uptake of Pulmonary Rehabilitation programmes for people with Chronic Obstructive Pulmonary Disease (COPD): A systematic review

Introduction and objectives Pulmonary Rehabilitation (PR) reduces the number and duration of hospital admissions, readmissions and improves health-related quality of life, e.g. breathlessness and fatigue, in patients with COPD. Despite evidence, guidelines and quality standards, PR is significantly underutilised with under-referral (15% of normative need) and limited uptake ( We aimed to address the research question: How effective are interventions to improve referral to and uptake of exercise-based pulmonary rehabilitation programmes in patients with COPD when compared to standard care or no intervention? Methods Systematic review following recognised methods, including all published observational, interventional, qualitative and quantitative studies of interventions specifically intended to increase levels of referral and/or uptake of pulmonary rehabilitation in patients with COPD. Exclusion criteria: individual case studies, conference abstracts and opinion pieces. No date or language restrictions. Search terms included: ‘pulmonary rehabilitation’ AND ‘referral’ OR ‘uptake’ applied to MEDLINE, EMBASE, CINAHL, PsychINFO, ASSIA, BNI, Web of Science and Cochrane Library from inception to June 2016 supplemented by review of reference lists and citation search. Titles, abstracts and full papers were reviewed independently, quality appraised (using Cochrane Collaboration’s tool for RCTs and ROBINS-I, AMSTAR) and entered into summary tables. The protocol was registered (PROSPERO) and reported according to PRISMA guidelines. Results We screened 3217 references, from which 7 papers including 6345 patients and 22 clinicians met inclusion criteria. Most studies (n = 5) were UK based. Designs, interventions and scope of studies were diverse with interventions often part of multifaceted evidence based management of COPD. Examples included computer based prompts at practice nurse review, patient information, financial incentives. Most studies (n = 5) reported improvements in referral or uptake of PR (range 0% – 25% increase), however most had methodological limitations with risk of bias. Due to heterogeneity, studies were not considered combinable and meta-analysis was inappropriate. Conclusions There is limited evidence for the efficacy of interventions to increase referral and uptake of PR. Existing studies are diverse and further testing using robust methods in various populations and settings is required to optimise access to PR.