A numerical analysis of 3D localization failure by a void-sheet mechanism

Ductile failure is analysed for materials containing two size-scales of spherical particles from which voids nucleate. The larger inclusions are taken to have low strength, whereas the smaller particles require large strains to nucleate micro-voids in the matrix material between the larger voids. The nucleation and growth of voids to coalescence is represented in terms of a porous ductile material model, describing either isotropic hardening or kinematic hardening behaviour. Failure modes involving plastic flow localization and void-sheet fracture are analysed for different distributions of the larger inclusions and for different stress states. The numerical quasi-static solutions are obtained by a full transient analysis of the equations of motion, in which the loading is applied so slowly that the quasi-static solution is well approximated.     

Legal reasoning with subjective logic

Judges and jurors must make decisions in an environment of ignoranceand uncertainty for example by hearing statements of possibly unreliable ordishonest witnesses, assessing possibly doubtful or irrelevantevidence, and enduring attempts by the opponents to manipulate thejudge's and the jurors' perceptions and feelings. Three importantaspects of decision making in this environment are the quantificationof sufficient proof, the weighing of pieces of evidence, and therelevancy of evidence. This paper proposes a mathematical frameworkfor dealing with the two first aspects, namely the quantification ofproof and weighing of evidence. Our approach is based on subjectivelogic, which is an extension of standard logic and probability theory,in which the notion of probability is extended by including degrees ofuncertainty. Subjective Logic is a framework for modelling humanreasoning and we show how it can be applied to legalreasoning.     

Effect of residual stresses on interface crack growth by void expansion mechanism

Crack growth along an interface between two adjacent elastic–plastic materials in a layered solid is analysed, using special interface elements to represent the fracture process ahead of the crack-tip. These interface elements account for ductile failure by the nucleation and growth of voids to coalescence. In these elements the stress components normal to the interface and the shear stresses are given by equilibrium with the surrounding material, and the stress component tangential to the interface is determined by the requirement of compatibility with the surrounding material in the tangential direction. It is assumed that the layers are sufficiently thick, so that the plastic regions around the crack-tip are much smaller than the thickness of the nearest layers. The analyses focus on the effect of initial residual stresses in the layered material, or on T-stress components induced during loading. The results show that the value of the T-stress component in the softer material adjacent to the interface crack plays the dominant role, such that a negative value of this stress component gives a significant increase of the interface fracture toughness.     

Interpreting Housing Allowance: The Norwegian Case

Housing allowances are part of both the housing policy and the general welfare policy. In order to understand fully how the housing allowances affect welfare and well-being, one needs to use multiple approaches. We propose to complement traditional analyses of marginal effects and short-run incentives with long-run perspectives taken from the new social investment literature and elements of self-esteem and fairness taken from the literature on universalism. A neo-liberal approach where analysts limit themselves to studies of marginal effects and short-run incentives both in the housing and in the labour market runs the risk of neglecting important aspects of the effects of housing allowances. Therefore, this may lead to retrenchment. The approach we propose is illustrated through a closer analysis of important elements of the housing allowance system in Norway as it is today, and the development of the system over time.     

A primer on the building economics of climate change

Climate change will entail new conditions for the construction industry. Knowledge about the implications of climate change on the built environment will be of the utmost importance to the industry in years to come. A building is a ‘long lasting’ durable asset that is changed over time due to exogenously imposed strains and by actions. The built environment has an expected lifetime varying from 60 to more than 100 years. Hence, the building economics of climate change should be treated within a dynamic analytical framework that explicitly allows for changes in the information sets over time. The building stock of the future consists of the building stock of today and of new construction. In the future, parts of the present building stock will be adapted to changes in the environment, while some parts will be kept as they are. Analysis of how building stock is affected by future climate change should handle this diversity. This can be done through the use of a putty-clay model. Uncertainty of what kind of climate regimes will prevail in the future enhances the profitability of actions that increase future flexibility. Hence, the real option approach to building economics is utilized.     

On the Path to Homeownership: Money,Family Composition and Low-income Households

In Norway, as in many other countries, homeownership is encouraged politically, and a majority of the households become homeowners at some stage in their life cycle. Many households move house when circumstances change, and it is often at this point that they also make their tenure choice. This paper employs a bivariate probit framework to model the transition rate from renting into homeownership. Using a sample of initial renters, subsequent tenure choice is analysed jointly with the stay-move decision. A particularly important question in this context is whether low-income households face differential constraints on entering owner occupation that could be addressed by policy change. The empirical model includes financial characteristics, household characteristics and changes in household characteristics as explanatory variables. Changes in household composition are particularly important in explaining variations in both tenure choice and mobility. Hence, the common practice of estimating housing market behaviour using a panel of intact households potentially obfuscates important determinants of that behaviour. The paper proceeds by using the equivalent of a Chow test to show that a hypothesis of equal coefficients in samples of low- and high-income households is firmly rejected. Thus low-income households do behave differently. Short-term variations in income appear to have little effect on people's capacity to enter owner occupation. However, low-income households are more dependent on past savings for successful entry. This suggests a rather different policy approach if owner occupation is to be expanded.     

Effect of plastic anisotropy on crack growth resistance under mode 1 loading

Crack growth in a solid with plastic anisotropy is modeled by representing the fracture process in terms of a traction-separation law specified on the crack plane, and crack growth resistance curves are calculated numerically. A phenomenological elastic-viscoplastic material model is applied, using one of two different anisotropic yield criteria to account for the plastic anisotropy. The analyses are carried out for conditions of small scale yielding, with mode I loading conditions far from the crack-tip. Different initial orientations of the principal axes relative to the crack plane are considered and it is found that the steady-state fracture toughness is quite sensitive to the type of anisotropy and to the angle of inclination of the principal axes relative to the crack plane.     

Cracking due to Localized Hot Shock

Results are presented for the cracking to be expected when a sudden temperature increase is applied over a localized region on a surface of a brittle solid. A localized temperature increase is applied to the surface of a body whose interior is initially at uniform temperature. A three-part analysis is conducted: (i) for the evolving temperature distribution, (ii) for the evolving thermal stresses induced by the nonuniform temperature field, and (iii) for stress intensity factors of cracks oriented either parallel to or perpendicular to the surface and initiated at times when the stresses are critical. Plane-strain and axisymmetric versions of the problems are considered. For the plane-strain problem, the complete trajectory of the crack is determined under the assumption that its tip advances maintaining a pure mode I field at all times. Conditions for excluding cracking due to localized hot shock are given.     

Overload effects in fatigue crack growth by crack-tip blunting

A basic mechanisms for fatigue crack growth in ductile metals is that depending on crack-tip blunting under tensile loads and re-sharpening of the crack-tip during unloading. In the present paper, the effect of an overload in one of the cycles is studied based on this mechanism. In a standard numerical analysis accounting for finite strain, it is not possible to follow the blunting/re-sharpening process during many cycles, as severe mesh distortion at the crack-tip results from the huge geometry changes developing during the cyclic plastic straining. Here, based on an elastic-perfectly plastic material model, crack growth computations are continued up to 700 full cycles by using remeshing at several stages of the plastic deformation. Crack growth results for purely cyclic loading are compared with predictions for cases where an overload is applied, and it is shown how crack growth slows down after the overload. Different load amplitudes, and an overload at different cycle numbers are considered.     

Enabling personalisation of remote elderly assistance

One of the goals of Ambient Assisted Living (AAL) solutions is to extend the time that elderly people can live independently in their preferred environments by using ICT technologies for personal healthcare. However, in order to be optimal, remote monitoring services and health-related interventions should be strongly personalised to specific individuals’ requirements, preferences, abilities and motivations, which can vary among the elderly, and even dynamically evolve over time for the same person depending on changing user needs and context-dependent conditions. In this paper we present an End User Development (EUD) tool for the personalisation of context-dependent assistance by non-technical users in the AAL domain. In particular, we have considered applications for remotely monitoring and assisting elderly people at home through sending multimedia messages and reminders, as well as changing the state of various domestic appliances (e.g. lamps, heating system, TV) and devices available in the context surrounding the user. The design and development of the tailoring environment has been carried out in an iterative manner, informed by the feedback that was gathered through empirical evaluations done with older adults and caregivers.