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

The Search for an Author: Shakespeare and the Framers

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Open Source Innovation, Patent Injunctions, and the Public Interest

This Article explores the difficulties that high technology markets pose for patent law and, in particular, for patent injunctions. It then outlines the ways in which “open source innovation” is unusually vulnerable to patent injunctions. It argues that courts can recognize this vulnerability, and respond to the particular competitive and innovative benefits of open source innovation, by flexibly applying the Supreme Court’s ruling in eBay v. MercExchange. Having dealt with the lamentable failure of the International Trade Commission to exercise a similar flexibility in its own patent jurisprudence, despite statutory and constitutional provisions that counsel otherwise, the Article concludes with some recommendations for reform

Intellectual Property Policy Online: A Young Person’s Guide

This is an edited version of a presentation to the Intellectual Property Online panel at the Harvard Conference on the Internet and Society, May 28-31, 1996. The panel was a reminder of both the importance of intellectual property and the dangers of legal insularity. Of approximately 400 panel attendees, 90% were not lawyers. Accordingly, the remarks that follow are an attempt to lay out the basics of intellectual property policy in a straighforward and non-technical manner. In other words, this is what non-lawyers should know (and what a number of government lawyers seem to have forgotten) about intellectual property policy on the Internet. The legal analysis which underlies this discussion is set out in the Appendix

The First Amendment and Cyberspace: The Clinton Years

Both in terms of speech regulation and in terms of providing raw material for the legal controversies that shape the law of the First Amendment, the legacy of Pres Clinton\u27s Administration is considerable, and nowhere more than in cyberspace. The most visible example of the Clinton Administration\u27s role in cyberspeech regulation are the Communications Decency Act, which was struck down by unanimous vote of the Supreme Court in 1997, and the Child Online Protection Act, which is now before the courts

Stress relaxation and elastic follow-up using a stress range-dependent constitutive model

Despite the availability of detailed nonlinear finite element analysis, some aspects of high temperature design can still be best addressed through more simplified methods. One such simplified method relates to the problem of elastic follow-up where typically in strain-controlled situations, elastic behaviour in one part of a structure can lead to large strain accumulation in another. Over the past thirty years it has been shown that in regions with significant elastic follow-up a plot of maximum stress against strain (a 'stress-strain trajectory') is virtually independent of the constitutive relation - a characteristic which can be used to estimate elastic follow-up for design purposes without detailed nonlinear finite element analysis. The majority of studies which have reported this independence on material behaviour have used simple constitutive models for creep strain, primarily based on power law creep or variations. Recently studies of the behaviour of high temperature structures with a stress range dependent constitutive law have begun to emerge. This paper examines the problem of elastic follow-up using such a constitutive law for a classic two-bar structure and for a more complex structure using finite element analysis. It is found that the independence of the stress-strain trajectory on constitutive equation is lost with a stress range dependent relation