Moderate energy impact analysis combining phenomenological contact law with localised damage and integral equation method

A computational impact analysis methodology has been developed, based on modal analysis and a local contact force-deflection model. The contact law is based on Hertz contact theory while contact stresses are elastic, defines a modified contact theory to take account of local permanent indentation, and considers elastic recovery during unloading. The model was validated experimentally through impact testing of glass-carbon hybrid braided composite panels. Specimens were mounted in a support frame and the contact force was inferred from the deceleration of the impactor, measured by high-speed photography. A Finite Element analysis of the panel and support frame assembly was performed to compute the modal responses. The new contact model performed well in predicting the peak forces and impact durations for moderate energy impacts (15 J), where contact stresses locally exceed the linear elastic limit and damage may be deemed to have occurred. C-scan measurements revealed substantial damage for impact energies in the range of 30-50 J. For this regime the new model predictions might be improved by characterisation of the contact law hysteresis during the unloading phase, and a modification of the elastic vibration response in line with damage levels acquired during the impact. © 2011 Elsevier Ltd. All rights reserved.

Indentation of power law creep solids by self-similar indenters

For creep solids obeying the power law under tension proposed by Tabor, namely sigma = b(epsilon) over dot(m), it has been established through dimensional analysis that for self-similar indenters the load F versus indentation depth h can be expressed as F(t) = bh(2)(t)[(h) over dot(t)/h(t)](m)Pi(alpha) where the dimensionless factor Pi(alpha) depends on material parameters such as m and the indenter geometry. In this article, we show that by generalizing the Tabor power law to the general three dimensional case on the basis of isotropy, this factor can be calculated so that indentation test can be used to determine the material parameters b and m appearing in the original power law. Hence indentation test can replace tension test. This could be a distinct advantage for materials that come in the form of thin films, coatings or otherwise available only in small amounts. To facilitate application values of this constant are given in tabulated form for a range of material parameters. (C) 2010 Elsevier B.V. All rights reserved.

Verification of McCabe's Delta L Law for Growth of Lysozyme Crystals by Hanging Drop Method

Lysozyme is a naturally occurring enzyme in egg white and has high commercial importance due to its antimicrobial properties. The main objective of this work was to study the growth rate of lysozyme crystals isolated from egg for the first 72 hours and verify the results with McCabe’s constant crystal growth theory. Hanging drop crystallization method was used to form high purity lysozyme crystals from the embryonic stage. To this end, this work differs from an earlier work of Forsythe et al., who used seed crystals in the size range of 10 µm - 40 µm for face growth measurements at different pH values. The maximum crystal size recorded in the present work was 392.86 µm, which is within the typical size range of 50 µm - 500 µm for which constant crystal growth is expected to hold according to McCabe’s ?L law. Electron micrographs (SEM) revealed the structure and dimensions of the crystals while SDS-Page was used to measure the purity of the crystals. The SEM results showed that that lysozyme growth rate was linear and agreed with McCabe’s constant growth theory, producing a growth rate of 1.77 x 10-3 µm .s-1

Withdrawing from Atmosphere: An Ontology of Air partitioning and Affective Engineering

The main objective of this text is to warn against atmospherics. However comfortable it might appear, an atmosphere is politically suspicious because it numbs a body into an affective embrace of stability and permanence. It becomes doubly suspicious because a body desires to be part of the atmosphere. For this reason, I rethink both affect and atmosphere ontologically rather than phenomenologically. I argue that an atmosphere is engineered by subsuming individual affects to what I call, following Sloterdijk, an atmospheric glasshouse. I suggest that this happens in four steps: a distinction between inside and outside through partitioning; inclusion of the outside inside; illusion of synthesis; and dissimulation. In order to do this, I begin with air as the elemental paradox of ontological continuum and rupture. I carry on with the passage from air to atmosphere while retaining the discourse around continuum and rupture. Finally, I indicate a way of rupturing the atmospheric continuum through the ontological movement of withdrawal from the atmosphere. The ultimate goal of the article is to sketch a problematic of atmospherics that puts together without synthesising an elemental ontology of continuum and rupture.

Withdrawing from atmosphere: An ontology of air partitioning and affective engineering

The main objective of this text is to warn against atmospherics. However comfortable it might appear, an atmosphere is politically suspicious because it numbs a body into an affective embrace of stability and permanence. It becomes doubly suspicious because a body desires to be part of the atmosphere. For this reason, I rethink both affect and atmosphere ontologically rather than phenomenologically. I argue that an atmosphere is engineered by subsuming individual affects to what I call, following Sloterdijk, an atmospheric glasshouse. I suggest that this happens in four steps: a distinction between inside and outside through partitioning; inclusion of the outside inside; illusion of synthesis; and dissimulation. In order to do this, I begin with air as the elemental paradox of ontological continuum and rupture. I carry on with the passage from air to atmosphere while retaining the discourse around continuum and rupture. Finally, I indicate a way of rupturing the atmospheric continuum through the ontological movement of withdrawal from the atmosphere. The ultimate goal of the article is to sketch a problematic of atmospherics that puts together without synthesising an elemental ontology of continuum and rupture.

Power law and entropy analysis of catastrophic phenomena

Catastrophic events, such as wars and terrorist attacks, tornadoes and hurricanes, earthquakes, tsunamis, floods and landslides, are always accompanied by a large number of casualties. The size distribution of these casualties has separately been shown to follow approximate power law (PL) distributions. In this paper, we analyze the statistical distributions of the number of victims of catastrophic phenomena, in particular, terrorism, and find double PL behavior. This means that the data sets are better approximated by two PLs instead of a single one. We plot the PL parameters, corresponding to several events, and observe an interesting pattern in the charts, where the lines that connect each pair of points defining the double PLs are almost parallel to each other. A complementary data analysis is performed by means of the computation of the entropy. The results reveal relationships hidden in the data that may trigger a future comprehensive explanation of this type of phenomena.

Modelling adhesive joints with cohesive zone models: effect of the cohesive law shape of the adhesive layer

Adhesively-bonded joints are extensively used in several fields of engineering. Cohesive Zone Models (CZM) have been used for the strength prediction of adhesive joints, as an add-in to Finite Element (FE) analyses that allows simulation of damage growth, by consideration of energetic principles. A useful feature of CZM is that different shapes can be developed for the cohesive laws, depending on the nature of the material or interface to be simulated, allowing an accurate strength prediction. This work studies the influence of the CZM shape (triangular, exponential or trapezoidal) used to model a thin adhesive layer in single-lap adhesive joints, for an estimation of its influence on the strength prediction under different material conditions. By performing this study, guidelines are provided on the possibility to use a CZM shape that may not be the most suited for a particular adhesive, but that may be more straightforward to use/implement and have less convergence problems (e.g. triangular shaped CZM), thus attaining the solution faster. The overall results showed that joints bonded with ductile adhesives are highly influenced by the CZM shape, and that the trapezoidal shape fits best the experimental data. Moreover, the smaller is the overlap length (LO), the greater is the influence of the CZM shape. On the other hand, the influence of the CZM shape can be neglected when using brittle adhesives, without compromising too much the accuracy of the strength predictions.

Construction management contracts: law and practice

The context of construction management (CM) reveals that this method of procurement is as much a management philosophy as a contract structure. It is important to consider legal and contractual issues in this context. The interplay between management and law is complex and often misunderstood. Before considering specific issues, the use of contractual remedies in business agreements is discussed. In addition, the extent to which standardising a form of contract detracts or contributes to the success of projects is also considered. The dearth of judicial decisions, and the lack of a standard form, render it difficult to be specific about legal issues. Therefore, the main discussion of legal issues is centred around a recently completed research project which involved eliciting the views of a cross-section of experienced construction management clients, consultants and trade contractors. These interviews are used as the basis for highlighting some of the most important legal points to consider when setting up CM projects. The interviews revealed that the advantage of CM is the proximity of the client to the trade contractors and the disadvantage is that it depends on a high degree of professionalism and experience; qualities which are unfortunately difficult to find in the UK construction industry.

Construction contracts: law and management (3rd edition)

This book is aimed primarily at students for whom the study of building or civil engineering contracts forms part of a construction-based course. We have had in mind the syllabus requirements for first degrees in Building, Civil Engineering, Architecture, Quantity Surveying and Building Surveying, as well as those of postgraduate courses in Construction Management and Project Management. We have also assumed that such students will already have been introduced to the general principles of English law, especially those relating to contract and tort. As a result, while aspects of those subjects that are of particular relevance to construction are dealt with here, the reader must look elsewhere for the general legal background. In producing this third edition, we have again been greatly assisted by the many helpful comments made by reviewers and users of its predecessor. Nonetheless, our basic aim is identical to that which underpinned the first edition: to provide an explanation of the fundamental principles of construction contract law, rather than a clause-by-clause analysis of any particular standard-form contract. As a result, while we draw most frequently upon JCT 98 for our illustrations of particular points, this merely reflects the pre-eminent position occupied by that particular form of contract in the UK construction industry. We conclude by repeating our previous warning as to the dangers inherent in a little learning. Neither this book, nor the courses for which it is intended, seek to produce construction lawyers. The objective is rather to enable those who are not lawyers to resolve simple construction disputes before they become litigious, and to recognize when matters require professional legal advice. It should be the aim of every construction student to understand the legal framework sufficiently that they can instruct and brief specialist lawyers, and this book is designed to help them towards that understanding.

A rate and state friction law for saline ice

Sea ice friction models are necessary to predict the nature of interactions between sea ice floes. These interactions are of interest on a range of scales, for example, to predict loads on engineering structures in icy waters or to understand the basin-scale motion of sea ice. Many models use Amonton's friction law due to its simplicity. More advanced models allow for hydrodynamic lubrication and refreezing of asperities; however, modeling these processes leads to greatly increased complexity. In this paper we propose, by analogy with rock physics, that a rate- and state-dependent friction law allows us to incorporate memory (and thus the effects of lubrication and bonding) into ice friction models without a great increase in complexity. We support this proposal with experimental data on both the laboratory (∼0.1 m) and ice tank (∼1 m) scale. These experiments show that the effects of static contact under normal load can be incorporated into a friction model. We find the parameters for a first-order rate and state model to be A = 0.310, B = 0.382, and μ0 = 0.872. Such a model then allows us to make predictions about the nature of memory effects in moving ice-ice contacts.

Improving outcomes-based engineering education in Australia

Graduate attributes are now a ubiquitous feature of higher education in Australia and internationally, and have been part of engineering education for more than a decade. The idea of graduate attributes is an apparently simple concept, focusing on educational outcomes, rather than inputs and process. While there is evidence of some benefits in engineering education arising from the introduction of outcomes-based accreditation, there is also evidence of many short-comings of the graduate attributes approach. There would be significant value in Engineers Australia providing additional discipline-specific guidance on attribute development. There would be significant value in Engineers Australia simplifying and consolidating the current multi-document accreditation system. A genuinely outcomes-based accreditation system would be based (only) on the demonstrated individual student attainment of appropriate graduate attributes, which might be delivered/gained by a range of means, including distance education. To fully meet the letter and spirit of the law for accreditation, programs will need to adopt some method of certification of individual student attainment of graduate attributes - one such method would be the use of student portfolios.

Exploring the influences on requirements engineering during global software development

Through an interpretive study of global virtual teams, this research has explored the influences on the requirements engineering processes during global software development. Complex layers of explicit and implicit elements in the project environment, including systems methodology, project steering, management commitment and cultural differences, were found to influence these processes.