Monkman-Grant relation - analysis of first order kinetics of creep in AISI 304 stainless steel

The transient creep behaviour in AISI 304 Stainless Steel at 873 and 973 K for different test conditions obeyed first order kinetics and it was shown that the validity of Monkman-Grant relation (MGR) is a consequence of first order kinetics. The analysis is extended to tertiary creep regime and the results are found to obey first order kinetics for all test conditions. A new relationship between steady state and tertiary creep is proposed as epsilon over dot ((sic)(s))'.t(t)/epsilon(t) = constant (where t(t) and epsilon(t) are time spent in tertiary and the limiting tertiary creep strain respectively); alpha' is found to be unity for all test conditions implying the validity of first order kinetics. Further, this relation (for alpha' = 1) is found to be identical to modified Monkman - Grant relation (MMGR; m' = 1 where m' is the exponent for epsilon over dot (s) in MMGR) for the conditions satisfying f = 1/lambda and it is postulated that validity of MMGR is also a consequence of first order kinetics. When first order kinetics is applicable, a generalised relationship between steady state creep rate and rupture life is formulated and is valid for the results at all test conditions

Analysis of first order kinetics for tertiary creep in aisi 304 stainless steel

The results of constant load creep tests on AISI 304 stainless steel at 873 and 973 K for different test conditions were found to obey the first order kinetics for tertiary creep. Distinct master creep curves were obtained at 873 and 973 K with a separate set of constant values of K', epsilon(t), beta' and C-MG. A relationship between steady-state creep rate epsilon over dot(s) , time spent in tertiary creep t(t) and limiting tertiary creep strain epsilon(t) is formulated as epsilon over dot(s) . t(t)/epsilon(t) = constant and is found to be valid for all test conditions. Further, this relation is identical to the modified Monkman-Grant relation (MMGR) for the conditions satisfying f = 1/lambda; it is postulated that the validity of MMGR is a consequence of first order kinetics. Another important outcome of this study is a generalised relation of the form epsilon over dot(s) . t(r) = (epsilon(23).epsilon(f))(1/2); and this relation is compared with the relation proposed by Radhakrishnan, i.e. epsilon over dot(s) . t(r) = (epsilon(23)(2) .epsilon(f))(1/3). It is suggested that cavities act as vacancy sinks and accelerate dislocation climb controlled recovery process leading to tertiary creep. Copyright (C) 1996 Acta Metallurgica Inc

Strategic multimodal intervention in at-risk elderly Indians for prevention of dementia (SMRUTHI INDIA): a cohort multiple randomised controlled trial (cmRCT) protocol

Introduction Treating modifiable risk factors of dementia may prevent or delay dementia cases by up to 40%. The ‘Strategic Multimodal Intervention in at-risk Elderly Indians for Prevention of Dementia (SMRUTHI INDIA)’ study will be conducted to establish a trial-ready cohort of elderly Indians who are at high risk of developing dementia.Methods and analysis The main aim of the study is to create and study a cohort of individuals at high risk of dementia in rural India, where we can do multiple intervention trials. The study uses the ‘Cohort Multiple Randomised Controlled Trial’ (cmRCT) design, which combines a cohort study with in-built provisions to do multiple randomised controlled trials. A large rural cohort of size 10 000 (four zones of India, through established Indian Council of Medical Research - Model Rural Health Research Units) will be followed systematically with yearly neuropsychological evaluation for 5 years (the current funding supports first 3000 participants). The study also proposes to design a multimodal ‘care bundle’ for the prevention of dementia, which is culturally tailored and context-specific to the Indian population. This intervention will undergo testing for feasibility in the hospital setting at the central coordinating site through a pilot randomised controlled trial (6 months, 30 participants). In parallel, the care bundle will be culturally and linguistically adapted and pilot-tested in 20 participants in each zone. The final curated care bundle (first intervention that is planned) will then be tested for efficacy in phase 2 of the SMRUTHI INDIA cmRCT cohort.Ethics and dissemination The study has received ethical clearance at the central coordinating site and at each of the four clinical sites by the Institute Research Committee of each site. The outcomes of the study will be disseminated to various target audiences, including research participants, general public, scientific community and policy makers through national and international conferences and events, social media, various community engagement activities and publication in peer-reviewed journals.Trial registration number The study protocol is registered in the Clinical Trial Registry of India (CTRI/2024/01/061172)