A dynamical interpretation of flutter instability in a continuous medium

Flutter instability in an infinite medium is a form of material instability corresponding to the occurrence of complex conjugate squares of the acceleration wave velocities. Although its occurrence is known to be possible in elastoplastic materials with nonassociative flow law and to correspond to some dynamically growing disturbance, its mechanical meaning has to date still eluded a precise interpretation. This is provided here by constructing the infinite-body, time-harmonic Green's function for the loading branch of an elastoplastic material in flutter conditions. Used as a perturbation, it reveals that flutter corresponds to a spatially blowing-up disturbance, exhibiting well-defined directional properties, determined by the wave directions for which the eigenvalues become complex conjugate. Flutter is shown to be connected to the formation of localized deformations, a dynamical phenomenon sharing geometrical similarities with the well-known mechanism of shear banding occurring under quasi-static loading. Flutter may occur much earlier than shear banding in a process of continued plastic deformation.Comment: 32 pages, 12 figure

Implicit yield function formulation for granular and rock-like materials

The constitutive modelling of granular, porous and quasi-brittle materials is based on yield (or damage) functions, which may exhibit features (for instance, lack of convexity, or branches where the values go to infinity, or false elastic domains) preventing the use of efficient return-mapping integration schemes. This problem is solved by proposing a general construction strategy to define an implicitly defined convex yield function starting from any convex yield surface. Based on this implicit definition of the yield function, a return-mapping integration scheme is implemented and tested for elastic-plastic (or -damaging) rate equations. The scheme is general and, although it introduces a numerical cost when compared to situations where the scheme is not needed, is demonstrated to perform correctly and accurately.Comment: 19 page

Computational modelling and experimental characterisation of heterogeneous materials

Heterogeneous materials can exhibit behaviour under load that cannot be described by classical continuum elasticity. Beams in bending can show a relative stiffening as the beam depth tends to zero, a size effect. Size effects are recognised in higher order continuum elastic theories such as micropolar elasticity. The drawback of higher order theories is the requirement of addition constitutive relations and associated properties that are often difficult to establish experimentally. Furthermore the finite element method, of great benefit in classical elasticity, has shown limitations when applied to micropolar elasticity. The determination of additional constitutive properties and the computational modelling of micropolar elasticity will be discussed in the context of a model heterogeneous material loaded in simple 3 point bending. The model material was created by drilling holes in aluminium bar in a regular pattern, with the hole axis normal to the plane of bending. The bending tests show that a size effect is present. These results are compared against modelling the detailed beam geometries in the finite element package ANSYS, which again shows the size effect. These two bending test are used to extract the additional micropolar elastic material properties. A comparison is then made against analytical solutions,numerical solutions using a micropolar beam finite element and a micropolar plane stress control volume method.It will be shown that the need for extensive experimental testing to determine the additional constitutive properties may not be necessary with the appropriate use of numerical methods

Enlisting accounting history in the contest between competing visions of accounting systems: Tommaso Zerbi and the origin of double-entry bookkeeping

Biographical research has attracted a significant level of interest from the accounting history community. Nevertheless, most of these studies are focused on documenting the life and work of renowned accounting scholars and practitioners. The present study seeks to investigate the work of an author who is yet to attract the attention of the international community, Tommaso Zerbi, in close connection with the social and academic context in which his work was developed. The study emphasises the political and militant role that accounting history may play in academic communities by showing how accounting history research is not necessarily a value-free endeavour in the generation of new knowledge but can be enlisted in ensuring the success of a specific understanding of accounting systems in the context of academic struggles. Although mainly aiming at contributing to a national debate, the originality and value of Zerbi’s work ended up offering a significant contribution to the international debate on the origin of double-entry bookkeeping

Institutional pluralism, accounting and the State. The Opera del Duomo in Pisa as a hybrid organisation (XI-XVI centuries)

This study considers the Opera del Duomo in Pisa, the organisation tasked with building the world-renowned complex located in the Square of Miracles, from its inception to the formation of the Grand Duchy of Tuscany in the 16th century. It draws upon Besharov and Smith’s understanding of hybridity to document the factors driving the transition from a form of hybridity characterised by a high level of conflict between the logics of the State, the Church and the Commune of Pisa to a form in which the State logic dominated over the others and conflict was overcome. The paper unveils how the regulatory power of the State generates changes in the interactions among logics over time, with particular attention to the role of accounting and accountability practices. It shows how historical studies help to untangle situations in which logics coexist in extreme conflict and identify new ways to engage with them

Environmental accounting and state power in the grand duchy of Tuscany (1537-1621)

Purpose. The study investigates the use of early forms of environmental accounting in the implementation of environmental strategies in the Grand Duchy of Tuscany between the 16th and 17th centuries. Design/methodology/approach. The study adopts the Foucauldian concept of raison d’État to shed light on the ways in which environmental accounting practices were used by Tuscan Grand Dukes to form a detailed knowledge of the territory to be governed and act accordingly. Findings. Financial and non-financial information relating to environmental issues enabled the Grand Dukes to ‘visualise’ the territory to be managed as an enclosed disciplinary space whereby the conduct of people living therein could be decisively influenced. Accounting practices as a tool for the implementation of environmental strategies did not merely aim to protect the environment but were a means to reinforce the power of the State. Research implications. The paper can inform future works that investigate the ways in which environmental policies and accounting are used to pursue far-reaching governmental goals. It encourages scholars to examine further the origins of environmental accounting and its early forms. Social implications. The study documents how environmental strategies and the related use of accounting can have a significant influence on how individuals are allowed to conduct themselves. It also shows that environmental accounting practices can be an important tool in a State’s machinery of power. Originality/value. The study offers a novel perspective on the use of environmental accounting information as a tool in the exercise of State power. It explores explicitly the interrelations between accounting, sustainability and power. It also adds new evidence to historical research that has engaged with early forms of environmental accounting

Accounting for colonial domination in Liberal and Fascist Italy, 1912-1941

This paper addresses the role played by accounting in the government of the Italian colonies of Africa during the Liberal and Fascist periods. Drawing upon the work of Foucault, Scott and Said and their understandings of governmentality and colonialism, and using a wide range of primary sources, the paper contributes to the accounting history literature by showing how calculative practices in the form of colonial budgets and the census of the population helped the Italian government to control activities in its colonies. The paper shows how accounting practices evolved under different political regimes in the achievement of different programmes of government. It also offers evidence of the way in which accounting can be mobilised to enable penetrating interventions in the life of indigenous populations

Discretionary sanctions and rewards in the repeated inspection game

We experimentally investigate a repeated “inspection game” where, in the stage game, an employee can either work or shirk and an employer simultaneously chooses to inspect or not inspect. The unique equilibrium of the stage game is in mixed strategies with positive probabilities of shirking/inspecting while combined payoffs are maximized when the employee works and the employer does not inspect. We examine the effects of allowing the employer discretion to sanction or reward the employee after observing stage game payoffs. When employers have limited discretion, and can only apply sanctions and/or rewards following an inspection, we find that both instruments are equally effective in reducing shirking and increasing joint earnings. When employers have discretion to reward and/or sanction independently of whether they inspect we find that rewards are more effective than sanctions. In treatments where employers can combine sanctions and rewards employers rely mainly on rewards and outcomes closely resemble those of treatments where only rewards are possible