Nonlinear and Rate-Dependent Hysteresis Electro Mechanical Responses of Ferro Electric Materials

This study presents nonlinear and time-dependent analyses of ferroelectric materials and structures. Phenomenological constitutive models are considered for simulating macroscopic responses of materials undergoing various histories of electromechanical inputs. When the electric field inputs are less than the coercive limit (minor loop simulations), there will be no polarization switching and a nonlinear time-dependent electro-mechanical constitutive model based on a single integral form is considered for the piezoelectric materials undergoing small deformation gradients and large electric field. The nonlinearity is accounted for by incorporating higher order terms of the electric field and the effect of loading history is incorporated through the time integrand. When the electric field inputs are above the coercive limit (major loop simulations), the electro-mechanical coupling constants are expressed as functions of a polarization state and it is assumed that in absence of the polarization, the material does not exhibit electro-mechanical coupling response. The polarization state consists of time-dependent reversible and irreversible parts, where the irreversible part is incorporated to account for polarization switching responses. This constitutive model is implemented at each material (Gaussian) point within continuum FEs. A quasi-linear viscoelastic (QLV) model is adopted in order to incorporate the time-dependent effect on the nonlinear electro-mechanical response of piezoelectric ceramics. The recursive integration technique is used to solve for the time-dependent constitutive model at each Gaussian point. Finite element method is then used for analyzing behaviors of several piezoelectric structures and structural components under various boundary conditions. Parametric studies are also conducted to examine the effect of loading rates and coupled electro-mechanical boundary conditions on the overall performance of smart structures. The developed FE model is also used for predicting the overall responses Active Fiber Composite (AFC). A unit cell of AFC, where different responses of the constituents (fiber, matrix, electrode finger, kapton layer) are incorporated, is considered and time dependent and nonlinear responses of AFC are determined. The overall responses of AFCs at different frequencies and electric field amplitude determined from the FE are compared with experiments. Reasonably good predictions are observed. Finally, FE analyses are performed to simulate shape changing in smart truss structures. An electro-active truss FE undergoing large deformations is formulated. Each truss member is modeled as an active element with nonlinear time-dependent electromechanical constitutive model. The desired shape is induced in the overall structure by applying electric field to each truss member. The truss FE model can handle both material and also geometric nonlinearities

PUBLIC ART, POLITICAL POWER AND PUBLIC SPACE (CASE STUDY: SCULPTURES OF TEHRAN)

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Les murs comme support politique. Les espaces publics à Téhéran

National audienceRésumé. Au cours des derniers siècles, la dialectique ainsi que la dualité moderne ont posé des difficultés en ce qui concerne le lien entre l'art et la vie quotidienne en Iran. La fresque est un outil important pour présenter l'art et la culture. La révolution islamique en 1979 a entraîné une modification et une désorganisation des structures sociale, culturelle et statistique des espaces publics et, par conséquent, une répartition différente des structures surtout stratégiques sur le plan politique par rapport à la période qui précède la révolutio

A City-Wide Art Gallery

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Memorialization of war between conflicts of interest before and after the Islamic Revolution: public art and public space in Iran

International audienceSince 1800s, numerous wars have impacted the cities of Iran. Regarding the urban artwork in Tehran, the capital of Iran, the following question comes to mind: What approach has the urban artwork adopted to represent the war and its related concepts? Adopting a documentary research approach and investigating the concept of war in different eras, this paper attempts to study the sculptures in urban spaces as documents. Based on the books and historical documents, a total of 192 sculptures, which were built from the Qajar dynasty to 2016 have been examined in this study. During the Qajar dynasty, the governments have used sculptures, especially the ones placed in city squares, to demonstrate their power. After the Constitutional Revolution, figures denoting concepts of justice and freedom became pervasive in the squares up until the end of the Pahlavi dynasty. After the Islamic Revolution, the Iran-Iraq war has been called Sacred Defense and the goal of creating statues has been changed to express revolutionary and ideological concepts. Figurative sculptures and busts have been made as a tribute to the martyrs of the Iran-Iraq war. KEYWORDS Sculpture | Urban art | War | Urban space | Tehra

Public Art: Place Making or Focus on Values (Case study: Vali-Asr Street, Tehran)

International audienceBaharestan art festival, which was held in Vali-Asr Street in Tehran in March and April 2016 on the pretext of starting the Iranian New Year (Nowruz), has widely attracted the attention of artists and other people. This article attempts to examine the role of this urban art festival and similar festivals in placemaking and the improvement of the quality of urban spaces considering the potential and capabilities of these areas in the city. According to the prepared questionnaire, some questions were asked of respondents randomly selected from citizens with different demographic information about their comments on different aspects of the artworks presented in the festival. The results of statistical analysis of the questionnaire showed how this festival and similar events act as effective agents in development of placemaking and creation of common scenes using urban arts. Results revealed three key findings. First, the artworks of the festival were able to bring New Year’s perceptions with Iranian value attributes to the respondents’ minds. Second, the artworks were intended to make the public space lively. Third, this project had potential to act as a medium to spread positive messages among the citizens. According to the results, this festival and similar urban art projects can further be considered as a new form of Iranian contemporary public art

Étude comparée de l’évolution de l’art moderne urbain à Téhéran et Paris jusqu’à 2000

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The Functionality of Art Galleries as Meeting Places in Tehran

International audience"Art gallery is a space for presentation of artworks. Today, ‘gallery tour’is a term, whichis not strangeamonggallery owners, artists, and middle-class youth of Tehran.The aim of this study isto investigate the functionalities of art galleries in Tehran as a space for meetings, hangouts, and artistic visiting. According to the prepared questionnaire, somequestionsasked participants in theopening of the exhibitionswhether art galleries can be considered assemi-public space, public space or a place for meetings. Statistical analysis showed howIranians use an art galleryas a place of meeting. Results revealedthatwomen visited galleries more frequently compared with men. Furthermore, people whose job is not in the field of art and those who live in traditional and ancient neighbourhoodsprefer to visit galleries on weekends. Artists also use the galleries as a space for random and job-related meetings. Younger people tend to visit the galleries just for artworks. Finally, almost all theinterviewees older than 30 years declared that they use space in galleries for hangouts." (source éditeur

Walls and Places: Political Murals in Iran

International audienceThis paper is rooted in the photography and observation of Graffiti that presents an overview of presence and absence of anonymous public writings in Tehran. It is based on over 150 digital photographic examples collected from Tehran, where the flourishing of artistic dissent is formed by widespread poverty and the recent political history followed by an economic collapse that radicalized youth of middle-class. According to Gehl‟s argument that art objects and places which form their causal milieu share social agency with the artists who produce them, the aim of this paper is to show how Graffiti confront institutional power by expanding semiotic street arts in the west areas of Tehran like Shahrak-e Gharb and Ekbatan Complex. The active role of open public spaces in the cultural and political performance of social changes is investigated in this study. Why murals are not part of the visual public discourse in Tehran, as they are in other divided societies? What is the Graffiti writers‟ role in the existence of murals? What political meanings are articulated in the interactions of Graffiti writers in specific areas of Tehran? How does whitewashing fit into a much larger civic discourse that includes individuals, groups and authorities? This paper tries to find acceptable answers to these questions. In particular, this paper aims to analyze the group-oriented visual discourse and discourse related to individuals. The Graffiti that studied in this paper have been selected from specific parallel areas located in the west of Tehran