Some consequences of stress range dependent constitutive models in creep

Studies of the behaviour of structural components at high temperature subject to creep have a long history and their behavioural characteristics, certainly for constant and cyclic load, well established. However, the majority of these studies have been based on relatively simple constitutive models in particular time‐ or strain‐hardening for primary creep with a basic power‐law model for secondary creep. These basic models can be enhanced to include tertiary creep with the introduction of well known damage models of the Kachanov‐Rabotnov type. Over the past decade the modelling of advanced high temperature materials has improved considerably and, coupled with advances in computational modelling of real‐world components, has allowed a much more realistic and detailed representation of structural behaviour at high temperature subject to precise thermo‐mechanical load histories. Nevertheless, most design rules for high temperature have been developed based on an understanding of creep behaviour with the simple constitutive models, which remain the most widely used even in design and assessment approaches using detailed nonlinear finite element analysis. To be useful for design purposes, modern advanced material models need to be able to make reference to conventional understanding of the behavioural characteristics of structures subject to creep. Yet this can often be problematic, not due to imprecision in the advanced models, but rather deficiencies in the simple models. Recent studies (by the author and others) of the behaviour of structures using simple creep models, but ones which are stress range dependent (that is, the form of the constitutive model, even for secondary creep, changes as the stress increases from low through moderate to high stress) have shown that under some types of loading creep behaviour of structures in significantly altered, while for others familiar design concepts can remain valid. Simple stress range dependent constitutive models have been around for well over 60 years but have been rarely used: the power‐law has been favoured since it is simple to use and has some desirable features which have led to robust simplified methods for creep design. The aim of this paper is to examine further the consequences of using a stress range dependent constitutive model in structural design and analysis. Several simple structural components under different loading conditions will be examined and the results compared to current design practice

Television sport in the age of screens and content

The death of television has been long predicated in the digital age, yet it remains a powerful mediator of live sports. This article focuses on football and examines the implications for the sport of the move to an age of screens and content. These may be large screens in public places or in our homes or those at work or smaller screens carried in the palm of our hands, but what we use them for, how content gets onto those screens, and the implications for sports and sports fans remain compelling questions in the digital age. The article argues that through reflecting on major media sport events such as the FIFA World Cup, we see patterns of continuity in the role played by television as well as evidence of change

The Search for an Author: Shakespeare and the Framers

QC 20141201</p

Putting it to the test

THE BPS Steering Committee on Test Standards (SCTS) has already developed and introduced standards for testing in occupational settings - the Level A and Level B Certificates of Competence in Occupational Testing - to encourage responsible test use by psychologists and nonpsychologists alike. Next month, at the Society's Annual Conference in London, the SCTS will launch the Level A Certificate of Competence in Educational Testing. It is envisaged that the Certificate will help to raise standards of test use and promote a wider knowledge of psychology among test users in education

The behavior of structures based on the characteristic strain model of creep

There has been much work over the past two decades to aid the design and assessment engineer in the selection of a suitable material model of creep for high temperature applications. The model needs to be simple to implement as well as being able to describe material response over long times. Familiar creep models, as implemented in the majority of nonlinear finite element analysis systems, are still widely used although not always accurate in modeling creep behavior at the end of the secondary phase. The Characteristic Strain Model (CSM) has been shown to be able to effectively model creep behavior at long times; it is simple to implement and requires a minimum of creep data. This paper examines the ability of the CSM to model the recognized behavior of the steady state creep of simple structures under multi-axial stress

A Comparison of Children’s Fitness in the Northwest and Southwest of England

The data from this paper was gathered from a larger cross-sectional study examining children’s physical activity participation in the Northwest and the Southwest of England. The purpose of this study was to carry out a battery of health and fitness tests with children in both areas to examine possible differences in various aspects of fitness or health by area. Heart rate recovery, flexibility, body fat, hand grip strength, upper body strength, explosive strength and agility were all measured using youth fitness tests endorsed by EUROFIT and YMCA with 59 boys and 57 girls across both areas. There were no statistically significant differences in both groups of children in hand grip strength, flexibility and agility. Statistically significant differences were noted between both groups of children in explosive strength, upper body strength and measured body fat percentage. Overall the study showed mixed results that may indicate area of residence influences aspects of fitness or activity. Further study is recommended to assess whether physical activity could play a role in the associated fitness characteristics