A framework to model thermomechanical coupled of fracture and martensite transformation in austenitic microstructures

A fully thermomechanical coupled phase-field (PF) model is presented to investigate the mechanism of austenite-to-martensite phase transformation (MPT) and crack initiation as well as its propagation in pure austenitic microstructures. The latent heat release and absorption involved in the MPT are explicitly taken into account by coupling the PF model with transient latent heat transfer. In order to consider temperature dependency in the PF model for MPT, a temperature-dependent Landau polynomial function, whose parameters are identified using molecular dynamics (MD) simulations, is proposed. Furthermore, the fracture surface energy is approximated based on the second-order PF model and then, the temporal evolution of the damage variable is given by the variational derivative of the total potential free energy of the system with respect to the damage variable. The achieved numerical results demonstrate that the model can be employed to predict the fracture mechanism of austenitic microstructures under a thermomechanical field in a multiphysics environment. The results reveal that the temperature has a tremendous impact on the growth rate of both martensitic variants and consequently on the crack growth path. The key contributions of this work are to shed light on the impact of thermal boundary conditions on the coupled process of MPT, crack initiation and growth

Assessing quality of life of kidney donors in Tehran in 2012-2013

Background and aim: Kidney transplantation is the best treatment for patients with end stage renaldisease. Living donor kidney transplantation is increasingly performed in Iran. Since the quality oflife of live kidney donors has been subjected to little investigation, the present study was conductedto investigate the quality of life of live kidney donors in Tehran in 2012-2013.Materials and methods: This is a descriptive study conducted on 45 donors living in Tehran in 2012-2013. Sample selection was started by recruiting convenient samples following by snow ballsampling. Data were collected by a questionnaire consisting of as a three sections: demographicinformation, SF-36 quality of life questionnaire and researcher made questionnaire .The data wereanalyzed by SPSS 19 .Results: Mean age of the donors was 34/4 year. 62/2 % of the donors were men. The quality of lifeof 66/7 % of donors in physical, 60 % in mental and 48/9 % in social domain were classified asmoderate (score:34-66). The mean score of quality of life of donors was 59. 59.58 % of theparticipants donated their kidney for financial reasons and there was no significant correlationbetween the quality of life scores and reason for donation. 31 % of the donors regretted thedonation.68/8% of donors do not encourage donation and recommend it to others and the averagescore of these donors is less than the donors who recommend donation(p <0/001)Conclusion: The quality of life of kidney donors in this study was moderate. It is worthwhile tofollow up the donors and to assess physical and mental problem of donors after donation in order toreduce subjective outcomes and regret in donors. There is a need for financial support of kidneydonors.Key words: Quality of life , Kidney donation, Live dono