Modeling the viscoplastic behavior of Inconel 718 at 1200 F

A large number of tests, including tensile, creep, fatigue, and creep-fatigue were performed to characterize the mechanical properties of Inconel 718 (a nickel based superalloy) at 1200 F, the operating temperature for turbine blades. In addition, a few attempts were made to model the behavior of Inconel 718 at 1200 F using viscoplastic theories. The Chaboche theory of viscoplasticity can model a wide variety of mechanical behavior, including monotonic, sustained, and cyclic responses of homogeneous, initially-isotropic, strain hardening (or softening) materials. It is shown how the Chaboche theory can be used to model the viscoplastic behavior of Inconel 718 at 1200 F. First, an algorithm was developed to systematically determine the material parameters of the Chaboche theory from uniaxial tensile, creep, and cyclic data. The algorithm is general and can be used in conjunction with similar high temperature materials. A sensitivity study was then performed and an optimal set of Chaboche's parameters were obtained. This study has also indicated the role of each parameter in modeling the response to different loading conditions

Investment in Advanced Manufacturing Technology: A Study of Practice in Large UK Companies

This paper reports the results of a survey investigation into the investment decision making practices of large UK manufacturing companies, especially in relation to investments in advanced manufacturing technologies. A 24% response rate was received in a survey of the finance directors of 466 large UK manufacturing companies. Responses were classified into three groups ranging from non-users of AMT to sophisticated users and analysis revealed that more sophisticated users do emphasise certain intangible benefits in combination with measures relating to the traditional dimensions of return and risk

Evaluating investments in advanced manufacturing technology: A fuzzy set theory approach

In this paper, a model for the evaluation of investments in advanced manufacturing technology is developed. Many authors have called for an integration of financial and non-financial factors in such evaluations and this paper demonstrates that it is conceptually possible to do this using the mathematics of the analytic hierarchy process and fuzzy set theory. The development of the model has certain distinguishing features. First, it is based on a conceptual framework that combines the three dimensions of risk, financial return and non-financial factors. The empirical basis for this has been investigated and previously reported by the authors. Second, models previously developed and reported in the literature are shown to suffer from certain flaws relating to the use of linguistic scales, the ranking of fuzzy performance indicators and partiality in the treatment of investment decision variables. These issues are addressed through the development of simpler linguistic scales based on the analytic hierarchy, a revised procedure for ranking fuzzy numbers and an attempt to build a comprehensive model through the three dimensions described above. Triangular fuzzy numbers are used throughout in order to make the mathematics tractable and relatively easy to understand and to facilitate presentation of a worked example. However, so that the reader is not misled, attention is drawn to some of the complexities in fuzzy arithmetic, especially the important distinction between subtraction/division and deconvolution of fuzzy numbers

Modelling and characterization of cell collapse in aluminium foams during dynamic loading

Plate-impact experiments have been conducted to investigate the elastic–plastic behaviour of shock wave propagation and pore collapse mechanisms of closed-cell aluminium foams. FE modelling using a meso-scale approach has been carried out with the FE software ABAQUS/Explicit. A micro-computed tomography-based foam geometry has been developed and microstructural changes with time have been investigated to explore the effects of wave propagation. Special attention has been given to the pore collapse mechanism. The effect of velocity variations on deformation has been elucidated with three different impact conditions using the plate-impact method. Free surface velocity (ufs) was measured on the rear of the sample to understand the evolution of the compaction. At low impact velocities, the free-surface velocity increased gradually, whereas an abrupt rise of free-surface velocity was found at an impact velocity of 845 m/s with a copper flyer-plate which correlates with the appearance of shock. A good correlation was found between experimental results and FE predictions

Moving beyond access: Towards a quality-orientated substance abuse treatment system in South Africa

There is growing concern about the increased demand for and limited access to substance abuse treatment in South Africa. The government has responded by allocating more money to the delivery of substance abuse treatment, expanding the number of state-funded treatment slots, and training additional health and social workers to deliver these services, particularly in provinces where the prevalence of substance-related problems is high, such as the Western Cape. While these efforts should be commended and continued, steps to improve service availability have occurred without adequate consideration of the quality of services provided. This is not surprising, as there is little or no routine monitoring and evaluation of substance abuse services in the country. It is also disquieting, as access to treatment is necessary but not sufficient for positive treatment outcomes

TRITIMED; a multidisciplinary project to improve drought adaptation in durum wheat

none6noneHABASH D.; ARAUS J.L.; LATIRI K.; KADER A.A.; TUBEROSA R.; NACHIT M.HABASH D.; ARAUS J.L.; LATIRI K.; KADER A.A.; TUBEROSA R.; NACHIT M

Day-case surgery for total hip and knee replacement: how safe and effective is it?

Multimodal protocols for pain control, blood loss management and thromboprophylaxis have been shown to benefit patients by being more effective and as safe (fewer iatrogenic complications) as conventional protocols. Proper patient selection and education, multimodal protocols and a well-defined clinical pathway are all key for successful day-case arthroplasty. By potentially being more effective, cheaper than and as safe as inpatient arthroplasty, day-case arthroplasty might be beneficial for patients and healthcare systems

Socioeconomic Disparities Do Not Affect Outcomes in Acute Limb Ischemia

Objective: The association between socioeconomic status (SES) and outcome after acute limb ischemia (ALI) is largely unknown. We aimed to determine whether SES is associated with worse presentations and outcomes for patients with ALI. Methods: We performed a retrospective review of a prospectively collected database containing all patients who had presented with ALI between April 2016 and October 2020 to a tertiary care center. SES was quantified using individual variables (median household income, level of education, employment) and a composite endpoint, the neighborhood deprivation index (NDI). The NDI is a standardized and reproducible index that uses census tract data, with a higher number indicating lower SES status. The NDI summarizes eight domains of socioeconomic deprivation. ALI severity was categorized using the Rutherford classification. The associations between SES and the severity of ALI at presentation and between SES and the outcomes were analyzed using bivariate analysis of variance, an independent t test, and multivariate logistic regression, as appropriate. Results: During the study period, 278 patients were treated for ALI, of whom 211 had complete SES data available. Their mean age was 64 years; 55% were men and 57% were white. The Rutherford classification of disease severity was grade 1, 2a, 2b, and 3 for 6%, 54%, 32%, and 8%, respectively. Patients with a low SES status using the NDI were more likely to have a history of peripheral arterial disease and chronic kidney disease at presentation (Table). The etiology (thrombotic vs embolic) was not associated with SES. No significant differences were seen between SES and the severity of ALI at presentation ( P = .96) or the treatment modality ( P = .80). We found no association between SES and either 30-day or 1-year limb loss or mortality (Table). Lower SES (higher NDI) was associated with increased 30-day readmissions ( P = .021). This association persisted on multivariate analysis ( P = .023). Conclusions: SES was not associated with the severity of ALI at presentation. Although SES was associated with the presence of peripheral arterial disease and chronic kidney disease at presentation and higher readmission rates for patients with ALI, SES was not a predictor of short-term or 1-year limb loss or mortality. In the present study, ALI presentation and treatment outcome were independent of SES

The theoretical mortality risk of an asymptomatic patient with a negative SARS-CoV-2 test developing COVID-19 following elective orthopaedic surgery

Aims: The risk to patients and healthcare workers of resuming elective orthopaedic surgery following the peak of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has been difficult to quantify. This has prompted governing bodies to adopt a cautious approach that may be impractical and financially unsustainable. The lack of evidence has made it impossible for surgeons to give patients an informed perspective of the consequences of elective surgery in the presence of SARS-CoV-2. This study aims to determine, for United Kingdom population, the probability of a patient being admitted with an undetected SARS-CoV-2 infection and their resulting risk of death; taking into consideration the current disease prevalence, reverse transcription-polymerase chain reaction (RT-PCR) testing and preassessment pathway. Methods: The probability of SARS-CoV-2 infection with a false-negative test was calculated using a lower-end RT-PCR sensitivity of 71%, specificity of 95% and the UK disease prevalence of 0.24% reported in May 2020. Subsequently, a case fatality rate of 20.5% was applied as a worst-case scenario. Results: The probability of SARS-CoV-2 infection with a false-negative preoperative test was 0.07% (around 1 in 1,400). The risk of a patient with an undetected infection being admitted for surgery and subsequently dying from COVID-19 is estimated at roughly 1 in 7,000. However, if an estimate of the current global infection fatality rate (1.04%) is applied, the risk of death would be around 1 in 140,000, at most. This calculation does not take into account the risk of nosocomial infection. Conversely, it does not factor in that patients will also be clinically assessed and asked to self-isolate prior to surgery. Conclusion: Our estimation suggests that the risk of patients being inadvertently admitted with an undetected SARS-CoV-2 infection for elective orthopaedic surgery is relatively low. Accordingly, the risk of death following elective orthopaedic surgery is low, even when applying the worst case fatality rate