Damage, Tension/Compression Asymmetry and Inferred Crack Growth in Fatigue title of Aluminum Alloys

The idea of a quantity D, which tracks the damage state of a material from 0 (virgin) to 1 (failed) is a well-established concept. In fatigue tests, where a given load cycle is repeated until failure, it is common to define damage D per cycle as the fraction of total life consumed per cycle, or 1/Nf. We begin by using Maximum Entropy method to develop a curve to model the life vs. load cycle relationship for a wrought aluminum alloy 2024-T351 in the low cycle fatigue range. The approach is novel in that the loading is described in terms in inelastic dissipation, rather than stress or strain. It is argued that inelastic dissipation provides a closer connection to the underlying physical damage processes. The resulting model is shown to fit the data set better than the Coffin-Manson equation, the Weibull distribution function, and other alternative functions. In wrought defect-free alloys such as 2024-T351, low cycle fatigue life is mainly determined by the number of cycles required for a persistent slip band (PSB) to form a propagating crack. Literature suggests that the process of crack formation in PSBs can be modeled as a Poisson process, for a constant amplitude test. This implies that once PSBs are established, typically in the first 10% of life, crack formation is equally likely on any cycle. Once the crack forms, the final 10% of life is occupied with crack growth. The premise that formation of cracks is a Poisson process provides a starting point for building a statistical model of the fatigue process. If the loading cycles are more severe, then the probability of crack initiation on each cycle is higher. It can be shown that the Coffin-Manson relationship and the Palmgren-Miner linear damage law can both be deduced from this model. Finally, it is shown that the scatter in lives at a given loading condition should follow the Erlang distribution, with a given positive shift. This is significant because the Erlang distribution has substantially the same left skewed shape as the Weibull and Log-normal distributions which are frequently used to model the scatter in fatigue lives. The second half of this work is concerned with the fatigue process of cast aluminum alloy AS7GU, which has many intrinsic defects from which fatigue cracks tend to initiate. Intermediate and high cycle fatigue life is dominated by crack growth rather than time for crack initiation. A different measure of D is developed, based on a non-linear stress-strain relationship and applicable to the elastic-dominated high cycle fatigue regime. It is based on a general constitutive law of an elastic material, which is shown to reduce to a quadratic stress strain relationship for a uniaxial test. Like the measure proposed in previous literature, this measure associates damage with the difference between the apparent stiffness of the specimen in tension vs. compression. However, unlike previously described measures, it connects the tension/compression asymmetry to a general nonlinear material model. The measure is applied to a sequence of axial fatigue tests and a rapid increase in the measured damage late in the life of the specimens is observed. Finally, the damage curves from the axial tests previously mentioned are interpreted in terms of a small crack growth law. The sizes of the cracks growing within the specimens during the tests are inferred from the measured D. A finite element model of the specimen was created to determine the relation between damage (as indicated by increase in compliance) and the size of a modeled crack. The finite element-determined relation is used to infer the size of the cracks in the specimens previously mentioned. A small crack growth law is fit to these inferred crack growth traces with good success

WHAT HAVE WE LEARNED FROM CATTLE/BEEF DISPUTES?

Agribusiness,

Solar Sails : Technology and demonstration status

Solar Sail propulsion has been validated in space (IKAROS, 2012) and soon several more solar-sail propelled spacecraft will be flown. Using sunlight for spacecraft propulsion is not a new idea. First proposed by Frederick Tsander and Konstantin Tsiolkovsky in the 1920's, NASA's Echo 1 balloon, launched in 1960, was the first spacecraft for which the effects of solar photon pressure were measured. Solar sails reflect sunlight to achieve thrust, thus eliminating the need for costly and often very-heavy fuel. Such "propellantless" propulsion will enable whole new classes of space science and exploration missions previously not considered possible due to the propulsive-intense maneouvers and operations required

Surface drag reduction and flow separation control in pelagic vertebrates, with implications for interpreting scale morphologies in fossil taxa

Living in water imposes severe constraints on the evolution of the vertebrate body. As a result of these constraints, numerous extant and extinct aquatic vertebrate groups evolved convergent osteological and soft-tissue adaptations. However, one important suite of adaptations is still poorly understood: dermal cover morphologies and how they influence surface fluid dynamics. This is especially true for fossil aquatic vertebrates where the soft tissue of the dermis is rarely preserved. Recent studies have suggested that the keeled scales of mosasaurids (pelagic lizards that lived during the Late Cretaceous) aided in surface frictional drag reduction in a manner analogous to the riblets on shark placoid scales. However, here we demonstrate that mosasaurid scales were over an order of magnitude too large to have this effect. More likely they increased the frictional drag of the body and may have played a role in controlling flow separation by acting as surface roughness that turbulated the boundary layer. Such a role could have reduced pressure drag and enhanced manoeuvrability. We caution those studying fossil aquatic vertebrates from positing the presence of surface drag reducing morphologies, because as we show herein, to be effective such features need to have a spacing of approximately 0.1?mm or less

High-Ampacity Power Cables of Tightly-Packed and Aligned Carbon Nanotubes

We characterize the current-carrying capacity (CCC), or ampacity, of highly-conductive, light, and strong carbon nanotube (CNT) fibers by measuring their failure current density (FCD) and continuous current rating (CCR) values. We show, both experimentally and theoretically, that the CCC of these fibers is determined by the balance between current-induced Joule heating and heat exchange with the surroundings. The measured FCD values of the fibers range from 10$^7$ to 10$^9$ A/m$^2$ and are generally higher than the previously reported values for aligned buckypapers, carbon fibers, and CNT fibers. To our knowledge, this is the first time the CCR for a CNT fiber has been reported. We demonstrate that the specific CCC (i.e., normalized by the linear mass density) of our CNT fibers are higher than those of copper.Comment: 14 pages, 8 figure

"It always comes down to money" : recent changes in service provision to disabled children, young people and their families in Scotland

This study follows on previous research published by Scotland’s Commissioner for Children and Young People which examined the use of eligibility criteria and assessment tools in services to disabled children and young people in Scottish local authorities (Lancaster 2012). The Stage One research also aimed to identify whether changing assessment procedures were affecting support to these young people. Based on local authority responses, the study found little evidence of tightening eligibility criteria, reduced levels of support or cutbacks in services. In 2013, the Commissioner’s Office funded further research to gather the views of voluntary sector providers and disabled children, young people and their families. The main aim of this study is to examine changes in the availability and accessibility of publicly funded services for these families over the past two years. This research covers local authority services, voluntary sector service providers, health services and professions allied to medicine. It includes children and young people aged 1-20 with a wide range of impairments including mental distress. The research is broadly based on a social model of disability while also taking account of the day-to-day implications of impairment and the significance of personal experience. The research used five different methods: • An on-line survey of voluntary sector providers: 53 valid responses were returned • 10 focus groups with parents, recruited through nine voluntary organisations and one local authority across Scotland. 56 parents/ carers took part • Five focus groups with young disabled people (aged 12- 20), recruited through voluntary organisations mostly in central Scotland. Eighteen took part • A one to one session with a young person (aged 17) who does not use speech • Three case studies, conducted by telephone interview, with parents and a service provider. The study received ethical approval from the University of Strathclyde Ethics Committee. Careful attention was paid to ethical issues throughout. Three limitations can be identified in this research. The young people’s groups did not include participants with as wide a range of abilities as we had anticipated; the parents in the focus groups and case studies were largely self-selecting and, for the most part, the views of service providers are not represented. However, local authorities’ views were presented in the Stage One research. Fifty-three voluntary service organisations, providing publicly funded services to families with disabled children, responded to the survey. Their range of characteristics indicates that they represent a reasonable cross-section of voluntary sector providers in this field. Seventy-nine per cent offered support, advice and information to parents and many also provided short breaks, leisure activities, education support or support for self-advocacy. Almost all (87%) of respondents had experienced a cut in funding or a change in allocation procedures by public funders which reduced their ability to support families. In some cases, this had led to reduced provision or the closure of some projects. About a third spent less on staff training compared to two years ago, while 19% were employing less qualified or experienced staff. Nine respondents had increased charges for their services. Only 27% of respondents said they had not experienced a cut in funding. Service providers were ambivalent about the impact of changes on their services. While 72% of respondents said that disabled children and their families get as good a service from their organisation now as they did two years ago, responses to other questions in the survey suggest that 81% of them think that there has been some deterioration in their provision. More specifically, compared to two years ago, 48% were limiting the number of people using their services, 47% were unable to offer the same level of support to new service users while 45% could not provide the same level of one-to-one support to users generally. About a third of voluntary service providers reported families had to wait longer for their services while a quarter had seen users withdrawn from their services by local authorities in favour of other forms of support. Nevertheless, many voluntary service providers are having difficulty coping with the level of demand for their services as their own budgets are frozen or reduced. They see the erosion of local authority services by funding cuts creating more demand for the voluntary sector. Voluntary providers are finding ways to maintain their services by reconfiguring services, dropping ‘niceties’ such as providing lunches at carers’ meetings, taking a ‘best value’ approach and seeking out new funding sources. But there is concern that maintaining a good quality service does not solve the problem of waiting lists and excluded families. Some respondents see the current cutbacks by local authorities as undermining developments in policy and practice made in recent years. The right to assessment of need may be being undermined in some local authorities. Although only two respondents mentioned self-directed support (SDS) as a current source of their funding, a number of comments indicated an expectation that SDS will be used as a further means to cut budgets. There is evidence of growing unmet need which is not recorded. Service providers are concerned about families being excluded from any funding or support. 32% of respondents have already experienced changes in local authority eligibility criteria affecting access to their services while 23% were aware of changes planned for next year. Many reported that support was now only funded for the most complex cases, when children were at risk or families in crisis. Service providers fear that cuts in public funding for services, coupled with the recent changes to welfare benefits, will increase the stress and isolation experienced by families and disabled children and the consequent risk of marital and family breakdown. Fifty-six parents/family carers took part in 10 focus group held across Scotland. Between them, these 47 women and nine men were looking after 61 disabled children and young people aged between 2 and 20. Parents in every group reported withdrawals of, and reductions in, the support they receive from a range of services - local authority social work and education departments, FE colleges, voluntary organisations, health services and professions allied to medicine - over the last two years. Many families did not have a social worker, some had never had one. Several had experienced their social worker being withdrawn during the last two years. It seems parents were generally not consulted about this and most were unhappy about it. A few had tried unsuccessfully to get a social worker and been told they did not need one or could not have one due to cutbacks or staff shortages. With some notable exceptions, most parents who did have a social worker received a low level of support, often having to ‘chase’ him/her. There was widespread satisfaction with the quality of short breaks services, with various schemes and units being praised. Parents generally wanted longer and/ or more frequent breaks. In some cases allocated hours had been withdrawn, reduced or failed to materialise. There was evidence of short breaks increasingly being used as a form of crisis intervention rather than a preventative service. Previous research has shown that disabled children and young people, like most young people, value opportunities to take part in social and recreational activities and make friends. A huge shortage of suitable social clubs and opportunities for young people was reported, the summer holidays being a particularly challenging time. Parents reported closure of holiday play schemes and a reduced number of hours for the young person to attend social clubs. There were concerns about staff not being trained to work with disabled children. In three areas, charges had been introduced for some social or play activities. Many positive comments were made about the schools the children and young people attended. However, parents also described reductions in the level of support and, in some cases, the quality of education available in some schools. In their view, reduced staffing levels were resulting in inadequate physical care, decreased learning support, less one-toone support including for some children assessed as needing it and a reluctance in some schools to develop Co-ordinated Support Plans. A minority of parents expressed concerns about the health and safety of their children. Three young people had been out of school for six or seven months without satisfactory alternative arrangements in place for their education. These situations were the culmination of complex and protracted difficulties but parents believed that insufficient training and experience among staff was a significant contributory factor. Parents reported reduced availability of occupational therapy, physiotherapy and speech and language therapy. Whereas therapists used to make routine ‘maintenance’ visits to children at school or at home, now they only came out in response to a specific problem or need. There were long waiting lists for appointments and for aids and equipment. Staff shortages were reported in CAMHS, a wheelchair and seating service and among nurses on children’s hospitals. A small number of parents reported an increase in services, sometimes due to an increase in their child’s challenging behaviour or following intervention by politicians they had contacted after experiencing long delays. Only a handful of parents had signed up for direct payments or (in three pilot areas) selfdirected support. While enjoying the flexibility and choice these brought, acting as an employer was felt to be demanding and ‘scary.’ The wider introduction of SDS, from April 2014, was widely seen as a money-saving exercise. Many services had long waiting lists, with some families also facing delays in securing an assessment of their child’s or their own needs. Parents attributed the bulk of changes they were experiencing to financial cutbacks. Increased demand and higher numbers of children being diagnosed on the autistic spectrum were additional factors. There was little evidence of parents being consulted about reductions in service provision and, when they were, parents generally felt their views had not been taken on board. Changes were often made without re-assessment or review of the child’s or family’s needs or, if re-assessments did take place, parents were not aware of it, although they and their children should be actively involved. Often parents were informed about changes by letter or telephone. While some professionals were singled out for high praise, many parents thought that staff, especially within local authorities, did not understand or listen to them. Most groups reported examples of insensitive comments or actions by professionals. Changes in service provision were often highly stressful for parents, sometimes causing or increasing anxiety, depression and relationship difficulties between partners. For children and young people, reductions in service provision variously led to disappointment, isolation, disrupted routines and, in a few cases, loss of skills. In some cases, stress caused by changes in support also affected siblings and grandparents. Although not directly asked about this, many parents raised the issue of poor information provision, adding that they generally found out about services from other parents and their own sleuthing efforts. Some had a view that, due to scarce resources, authorities withheld information or even gave out disinformation. There was great anxiety about the future, both in terms of further financial cutbacks and ‘welfare reform’ and the perceived ‘void’ of support and opportunities for young people when they leave school. Five focus groups were held with a total of 18 young people plus a one-to-one interview with a participant who used little speech. The age range was 12-20. Fifteen males and four females took part: the reason for the gender disparity is not fully explained by the higher ratio of disabled males to females. The participants were recruited through voluntary sector organisations including three catering for young people with learning disabilities. The young people’s views about services differed in tone and focus from parents’ accounts. Parents were generally responsible for arranging and liaising with services: young people had little direct involvement of that kind. They discussed their use of services within the wider context of their everyday lives. Most had experience of using a service whose input had come to an end. Some did not know the reason; others related it to their increasing age, changing needs or interests or other personal circumstances. A few reported that a service (such as speech and language therapy or physiotherapy) had been withdrawn which they felt they still needed. One young person identified financial constraints, shortage of social workers and greater priority being given to work with children as the reasons she had lost her social worker. In several cases, professionals had suggested finding a befriender for the young person but this had not materialised, apparently because alternative supports were identified or no befriender was currently available. The participants attended and enjoyed a wide range of social and recreational activities and had more to say about these than other services. There was some evidence that young people were offered more choices within these services than other forms of provision. At the same time, there were a couple of examples of individuals feeling less included. One young woman was not involved in swimming sessions with the social club she attended while another person was unable to meet up with friends outside school and service settings. The young people identified various services they used and staff they knew, generally expressing satisfaction with both. At the same time, there was often a sense of the young people being ‘provided’ with support, for example, through referral from other services. While they were involved in everyday choices about activities and entertainment, they seemed to have little say in more significant decisions about which services they used, why they used them or how they used them. With some exceptions, family members, particularly mothers, were identified as a key source of support in the everyday and an interface or mediator with services. Mothers were often described as the main decisionmakers when it came to using services and the young people expressed confidence in the decisions taken. Other participants reported that professionals made decisions about the support they should have: they did not mention being consulted. One view was that, while professionals seek young people’s views about topics which they (the professionals) considered important, they do not ask young people what matters to them. Loss of certain supports was an issue for some older participants no longer eligible for children’s services. Some also expressed wider concerns about the move to adult life, including insufficient careers advice, support to prepare for job interviews and difficulties learning to drive. One young person felt she was being discriminated against at college while another believed that young disabled people face discrimination in the labour market. Three case studies were carried out focusing on two boys and a girl aged 7, 10 and 15 respectively. The three young people all had complex needs including challenging behaviours. Their mothers each took part in a telephone interview and were invited to nominate a service provider whom we could also interview. This led to one voluntary service provider taking part. The parents gave detailed accounts of mostly unwelcome changes made to their service provision over the preceding two years. Although all had their own experiences, some common themes emerged. All had experienced withdrawal, reduction or breakdown of services in the last two years, in one case with no alternative being offered, in others, with what parents saw as inadequate or inappropriate alternatives offered. In two cases, the substitute services proposed did not match assessed need. One family had been offered three alternative services; one never materialised and the other two were not available. Two parents stated there had been no review or re-assessment of need prior to the loss of service or subsequently. All three had been involved in protracted negotiations (between one and two years) with the local authority to secure better support. While some professionals were seen as trying to be helpful, others were not. Each parent had a sense of ‘changing goalposts’ in the local authority, two believing they had been deliberately misinformed on some matters. In all three cases, there was a lack of transparency in the way decisions to change or reduce services were made. Two had reached Stage 31 in the complaints procedure. The absence of adequate support, coupled with the young people’s challenging behaviour, placed huge stress on families, including siblings. The voluntary service provider interviewed, whose input to the family had not changed, acknowledged the increased stress to the family and empathised with their frustration. Equally, she understood the limited resources available to the local authority and questioned its ability to provide personalised support to young people with complex needs. While some findings from this study coincide with local authorities’ accounts in the Stage One research, significant differences have also emerged. There is evidence of reductions in local authority budgets and services for disabled children, tightening eligibility criteria, support being removed without review or reassessment, and a lack of consultation with disabled children and young people. There is a real danger that children and young people’s entitlements under international conventions and UK and Scots law are being and will continue to be eroded, alongside the undermining of established good policy and practice. Reduced levels and quality of support and widespread deterioration in various aspects of service provision have led to less choice, long waiting lists and increased unmet need, with a shift away from preventative work to crisis intervention. There has been a small increase in charging for services, both in terms of increased rates and introduction of new charges. The uptake of direct payments and SDS by these parents, on behalf of their children, was low. There were mixed feelings about their benefits. The wider implementation of SDS from April 2014 was widely viewed as a money saving exercise. There was a widespread view that disabled children, young people and their families were being ‘discriminated against by services’ and ‘treated like second class citizens’. Next steps - proposed actions for public bodies Local authorities, health boards and voluntary organisations must ensure they are observing disabled children’s legislative rights and entitlements. Specifically: • Under the Children (Scotland) Act 1995, local authorities must consult with children and young people, using accessible formats, and take their views into account when making decisions. Parents also have a right to be consulted. • Under the same Act, local authorities must formally assess a child’s needs when a parent asks them to do so. • If a child is assessed as needing certain named services, such as aids and equipment, practical help in the home, travel or recreational facilities, and is eligible for them, then under the Chronically Sick and Disabled Persons (Scotland) Act 1972, the local authority must provide them. • Local authorities should be aware that it is not good practice, and a previous judicial review2 shows it can be unlawful, to reduce or withdraw services from disabled children or young people without proper re-assessment or review of their needs. • Under the Children (Scotland) Act 1995, public bodies should publish information about available services: it would be helpful if practitioners actively disseminated such information, explaining how it applies to individual children. Accessible materials should be also available for children and young people In relation to specific issues: • Local authorities and health boards should ensure that budgets and staffing levels for disabled children’s services are sufficient to meet assessed need as well as the increasing number of service users and complexity of some cases. • Waiting lists should be actively managed and regularly monitored, with families being kept informed of progress and offered advice and information as appropriate. • Local authorities should inform disabled young people and their families about the benefits and the underlying principles of SDS and ensure practical assistance with the organisation and administration of direct payments is available. In relation to specific services: • There is a need for far more social and recreational opportunities for disabled children and young people, including those with life-limiting conditions. Local area co-ordinators, who have a capacity building remit, could support mainstream organisations to include disabled children and young people. • Professions allied to medicine (specifically, occupational theory, physiotherapy and speech and language therapy) should be more readily available to those disabled children and young people who would benefit from treatment on an on-going basis. • Local authorities should have arrangements in place for emergency care of disabled children and young people w