Martensitic Thin Wires under Restrained Recovery: Theoretical and Experimental Aspects

A one-dimensional model for the evolution of microstructure in single crystal shape memory wires has been recently proposed in (Rizzoni (2011)). The model is based on the constrained theory of martensite introduced by (Ball et al. (1995); De Simone and James (2002)) and on the assumption that stable equilibrium configurations are deformations lying at the energy wells on most parts of the wire. In this paper we compare the response simulated for restrained recovery conditions (Rizzoni (2011)) with experimental data obtained in restrained recovery tests performed on NiTi wires. As an application, we consider a truss made of shape memory wires and rigid elements, and we calculate its deformation after thermal activation of the shape recovery

a preliminary investigation of strength models for degenerate graphite clusters in grey cast iron

Abstract Defects morphology primarily affects the mechanical properties of grey cast iron. In large castings, porosity and clusters of degenerate graphite are heterogeneously dispersed into the ferrous matrix and serve as initiation sites for fatigue and fracture processes. Strength and toughness of nodular cast iron compare to many grades of steel but experiments show that nodular cast iron also exhibits some specific effects, different from those typical of steels and due to cast iron microstructural inhomogeneity. In the present communication, we report on a preliminary investigation aimed at correlating the effect of the graphite microstructure to the mechanical properties of the material via a simplified geometrical description of the defects

Numerical Validation of Multiphysic Imperfect Interfaces Models

none4We investigate some mathematical and numerical methods based on asymptotic expansions for the modeling of bonding interfaces in the presence of linear coupled multiphysic phenomena. After reviewing new recently proposed imperfect contact conditions (Serpilli et al., 2019), we present some numerical examples designed to show the efficiency of the proposed methodology. The examples are framed within two different multiphysic theories, piezoelectricity and thermo-mechanical coupling. The numerical investigations are based on a finite element approach generalizing to multiphysic problems the procedure developed in Dumont et al. (2018).openDumont S.; Serpilli M.; Rizzoni R.; Lebon F.C.Dumont, S.; Serpilli, M.; Rizzoni, R.; Lebon, F. C

Repositório de acesso livre para agroecologia e agricultura orgânica do Brasil.

Resumo: Considerando que a literatura técnico-científica em Agroecologia e Agricultura Orgânica no Brasil é abundante, está dispersa e de difícil acesso, esse trabalho teve como objetivo criar e gerenciar um banco de dados da literatura no Brasil. Nesse sentido, há consenso na comunidade de especialistas e pesquisadores que estudam a informação, que a alternativa mais adequada e adotada em todo o mundo são os repositórios digitais de acesso aberto. Além de contemplarem os processos necessários para o gerenciamento da informação técnico-científica, os repositórios digitais de acesso aberto contribuem diretamente para a melhoria dos processos de comunicação na Ciência. Assim, o repositório escolhido para armazenar a literatura brasileira em Agroecologia e Agricultura Orgânica foi o Organic Eprints

TWSME of a NiTi strip in free bending conditions: experimental and theoretical approach

This paper deals with the two-way shape memory effect (TWSME) induced on a strip of a nearequiatomic NiTi alloy by means of the shape memory cycling training method. This procedure is based on the deformation in martensite state to reach the desired cold shape followed by cycling the temperature from above Af to below Mf. To this end, the sample was thermally treated to memorise a bent shape, thermomechanical trained as described and thermally cycled in unloaded conditions in order to study the stability of the induced TWSME. Heating to Af was reached by a hot air stream flow whereas cooling to Mf was achieved through natural convection. The evolution of the curvature with the increasing number of cycles was evaluated. The thermomechanical behaviour of the strip undergoing uniform bending was simulated using a one-dimensional phenomenological model based on stress and the temperature as external control variables. Both martensite and austenite volume fractions were chosen as internal parameters and kinetic laws were used in order to describe their evolution during phase transformations. The experimental findings are compared with the model simulation and a numerical prediction based on the approach proposed in [25]

TWSME of a NiTi strip in free bending conditions: experimental and theoretical approach

This paper deals with the two-way shape memory effect (TWSME) induced on a strip of a nearequiatomic NiTi alloy by means of the shape memory cycling training method. This procedure is based on the deformation in martensite state to reach the desired cold shape followed by cycling the temperature from above Af to below Mf. To this end, the sample was thermally treated to memorise a bent shape, thermomechanical trained as described and thermally cycled in unloaded conditions in order to study the stability of the induced TWSME. Heating to Af was reached by a hot air stream flow whereas cooling to Mf was achieved through natural convection. The evolution of the curvature with the increasing number of cycles was evaluated. The thermomechanical behaviour of the strip undergoing uniform bending was simulated using a one-dimensional phenomenological model based on stress and the temperature as external control variables. Both martensite and austenite volume fractions were chosen as internal parameters and kinetic laws were used in order to describe their evolution during phase transformations. The experimental findings are compared with the model simulation and a numerical prediction based on the approach proposed in [25]

Survival on Renal Replacement Therapy: Data from the EDTA Registry

Extensive survival data are presented from the EDTA Registry's files for patients who started renal replacement therapy in 1970-1974 compared to 1980-1984. The contribution of the different treatment modalities (haemodialysis, continuous peritoneal dialysis, and transplantation) to the survival of patients according to geographical region is also shown. Survival on renal replacement therapy, irrespective of treatment modality and of primary renal disease, was best in the 10-14-year-old patients, with 58% at 10 years and 52% at 15 years, and decreased with rising age to 28% at 10 years and 16% at 15 years in patients aged 45-54 when they commenced therapy in 1970-1974. When comparing the 0-4-year-old with the 10-14-year-old cohort of the paediatric patients, 5-year survival rates for patients starting renal replacement therapy in the early eighties declined from 85% to 70% with decreasing age. Treatment policy, as reflected by the proportion of patients on different modes of therapy, varied markedly between European regions but affected survival to a small extent only. The large population with diabetic nephropathy incurred annual mortality rates 2-3 times greater than those observed in patients with ‘standard' primary renal diseases. Haemodialysis and continuous peritoneal dialysis, although not comparable because of important differences in selection policy, yielded similar survival rates. Patient and graft survival rates have improved markedly when comparing patients starting renal replacement therapy in the early seventies with the eighties; particularly for cadaveric transplantation. Patient survival after second grafting was similar to that after first grafting, with 83% at 5 years after second cadaveric grafting in the 15-44-year-old cohort, vs 85% after first cadaver transplantation in 1980-1984. Second cadaveric graft survival was superior to average first-graft survival for those recipients whose first graft had been functioning for more than 1 year. However, second-graft survival in rapid rejectors of a first graft as well as third cadaveric graft survival were curtailed by the large number of early losses, with only 52% of third grafts functioning at 1 year. For living related donor transplantation, parents were mostly used in children whilst identical siblings predominated in adults older than 45. In the early eighties, patient survival was 92% at 5 years for recipients younger than 15, 87% for the 15-45 year old cohort and 72% for those aged 45 or older. From the overall survival rates on renal replacement therapy obtained at 5 years in the early eighties, it appears safe to predict that at least 65% of young adults and 25% of patients aged 55-64 will be surviving at 10 years after starting therap

Demography of Dialysis and Transplantation in Europe, 1984: Report from the European Dialysis and Transplant Association Registry

The demography of treatment of children by renal replacement therapy in Europe is presented based on returns of individual patient questionnaires to the EDTA Registry up until the close of 1984. Patient questionnaires for 1984 were completed by all centres which defined themselves as special paediatric units. A total of 4983 patients have been reported to the Registry up until 31 December 1984 as having commenced renal replacement therapy under the age of 15. Of these, 1570 were known to be alive on a defined form of treatment at the end of 1984 and still under the age of 15. The numbers of these patients kept alive by different forms of treatment in individual countries are presented. The stock of patients aged under 15 at the end of 1984 exceeded 30 per million child population in Belgium, France, Iceland and Luxembourg. The highest age specific acceptance rates for children onto renal replacement therapy during 1984 were noted in those aged between 10 and 14 at first treatment. Age specific acceptance rates for children varied greatly between individual countries, and 18 countries reported no new patients under the age of 5 during 1984. Transplant activity in paediatric patients during 1984 has been analysed and results on regrafting presented. Proportional distribution of primary renal diseases amongst children commencing therapy in 1984 is shown according to age at start of treatment. Haemolytic uraemic syndrome was reported as the cause of end-stage renal failure in 12.0% of children commencing treatment under the age of 5, and 12.3% of children between 5 and 9. Finally, information on cause of death in paediatric patients dying during 1984 is presented, and shows cardiovascular disease was the leading cause of mortalit

EDTA Registry Centre Survey, 1985: Report from the European Dialysis and Transplant Association Registry*

This paper summarises the information given on the 1985 EDTA Registry centre questionnaire which was returned by 82% of 1959 known dialysis and transplant units in 33 European countries. Trends in the use of different forms of renal replacement therapy are discussed, and attention drawn to the discrepancy between the EDTA centre and individual patient questionnaires as a source of demographic information on dialysis and transplantation. The results of special questions on dialyser re-use, dialysis equipment, AIDS, and hepatitis are presented, and information obtained from the special paediatric section of the centre questionnaire is also give