Development and validation of a 3D computational tool to describe concrete behaviour at mesoscale. Application to the alkali-silica reaction

A finite element analysis of the large deformation of three-dimensional polycrystals is presented using pixel-based finite elements as well as finite elements conforming with grain boundaries. The macroscopic response is obtained through volume-averaging laws. A constitutive framework for elasto-viscoplastic response of single crystals is utilized along with a fully-implicit Lagrangian finite element algorithm for modeling microstructure evolution. The effect of grain size is included by considering a physically motivated measure of lattice incompatibility which provides an updated shearing resistance within grains. A domain decomposition approach is adopted for parallel computation to allow efficient large scale simulations. Conforming grids are adopted to simulate flexible and complex shapes of grains. The computed mechanical properties of polycrystals are shown to be consistent with experimental results for different grain sizes.     

Assessing and improving commonality and diversity within a product family

At a time when product differentiation is a major indicator of success in the global market, each company is looking to offer competitive and highly differentiated products. This differentiation issue is restricted by the design of platform-based products that share modules and/or components. It is not easy to differentiate products in a market that is often overwhelmed by numerous options. A platform-based approach can be risky because competition in the global market can become an internal competition among similar products within the family if there is not enough differentiation in the family. Thus, the goal for the product platform is to share elements for common functions and to differentiate each product in the family by satisfying different targeted needs. To assess commonality in the family, numerous indices have been proposed in the literature. Nevertheless, existing indices focus on commonality and reflect an increase in value when commonality increases but do not positively reflect an increase in the value as a result of diversity; hence, the commonality versus diversity index (CDI) is introduced in this paper to assess the commonality and diversity within a family of products or across families. The CDI has variable levels of depth analysis to help designers design or improve the product family. Two case studies using single-use cameras and power tool families highlight the usefulness of this new index.     

Design of optimal extrusion die for a range of different materials

THE coat‐hanger melt distributor is a device commonly used in the wire coating process. Its task is to distribute the melt around the conductor uniformly. It is quite common that materials and flow rates differ from what had been specified during the design procedure. This may lead to bad performance with materials of very different rheological properties from the design material. In this article, we present an optimal design approach to avoid this loss of performances. This approach involves coupling a three‐dimensional finite element simulation software with an optimization strategy based on a response surface method. The objective is to determine a coat‐hanger melt distributor geometry that ensures a homogeneous exit velocity distribution that will best accommodate for a different range of materials. A coat‐hanger melt distributor with a manifold of constant width is designed, and a set of flow distribution measurements is established for two different materials. The results of numerical simulation are then validated by comparison with experimental measurements. The effect of material change is also investigated. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

Layered particle-based polymer composites for coatings: Part II—Stone chip resistant automotive coatings

Especially in the course of modern automotive coatings comprising a reduced number of layers the resistance towards the stone chipping is becoming an issue. Layered double hydroxide (LDH)-based polymer composites are readily accessible materials and suitable to impart impact resistance to coatings, provided that an accurate understanding of the structure property relations both of the platelets and the composites is achieved.Incorporated into aqueous polymer dispersions the LDH particles are found in the resultant composites in the form of aggregated clusters, polymer intercalated stacks or exfoliated platelets depending on their size and the type of the intercalated anions.In addition LDH particles are found to be effective in the control of the coating layer architecture by affecting the spinodal phase separation of the incompatible polymers.Applied as a primer layer the LDH-based composites provided an excellent stone chip resistance to an automotive coating system.     

Validation of finite-element models using full-field experimental data: Levelling finite-element analysis data through a digital image correlation engine

Full-field data from digital image correlation (DIC) provide rich information for finite-element analysis (FEA) validation. However, there are several inherent inconsistencies between FEA and DIC data that must be rectified before meaningful, quantitative comparisons can be made, including strain formulations, coordinate systems, data locations, strain calculation algorithms, spatial resolutions and data filtering. In this paper, we investigate two full-field validation approaches: (1) the direct interpolation approach, which addresses the first three inconsistencies by interpolating the quantity of interest from one mesh to the other, and (2) the proposed DIC-levelling approach, which addresses all six inconsistencies simultaneously by processing the FEA data through a stereo-DIC simulator to ‘level' the FEA data to the DIC data in a regularisation sense. Synthetic ‘experimental' DIC data were generated based on a reference FEA of an exemplar test specimen. The direct interpolation approach was applied, and significant strain errors were computed, even though there was no model form error, because the filtering effect of the DIC engine was neglected. In contrast, the levelling approach provided accurate validation results, with no strain error when no model form error was present. Next, model form error was purposefully introduced via a mismatch of boundary conditions. With the direct interpolation approach, the mismatch in boundary conditions was completely obfuscated, while with the levelling approach, it was clearly observed. Finally, the ‘experimental' DIC data were purposefully misaligned slightly from the FEA data. Both validation techniques suffered from the misalignment, thus motivating continued efforts to develop a robust alignment process. In summary, direct interpolation is insufficient, and the proposed levelling approach is required to ensure that the FEA and the DIC data have the same spatial resolution and data filtering. Only after the FEA data have been ‘levelled' to the DIC data can meaningful, quantitative error maps be computed.     

Control of hydration and degradation properties of triblock copolymers polycaprolactone‐b‐polydimethylsiloxane‐b‐polycaprolactone

The objectives of this study are to observe the effects of the introduction of polydimethylsiloxane (PDMS) on the hydration and degradation of aliphatic polyesters in water, such as poly(ε‐caprolactone) (PCL). The mechanism of PCL degradation in water is well known, and PDMS is a nonbiodegradable and hydrophobic polymer. The ligation of these two polymers should allow the synthesis of new polymers with hybrid properties in terms of degradation and surface energy. The deterioration in water should be controlled by the ratio of each polymer. The triblock copolymers were synthesized through ring opening polymerization with stannous octanoate as the catalyst. A film of each copolymer was prepared and immersed in distilled water to study their aging. Kinetic results of hydration and degradation show that the addition of PDMS on PCL does not change the profiles of hydration and degradation. But the variation of the structure of the triblock (molecular weight or ratio of each block) allows to increase or decrease the rate of hydration, so as to control its degradation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40431.     

Combing and self-assembly phenomena in dry films of Taxol-stabilized microtubules

Microtubules are filamentous proteins that act as a substrate for the translocation of motor proteins. As such, they may be envisioned as a scaffold for the self-assembly of functional materials and devices. Physisorption, self-assembly and combing are here investigated as a potential prelude to microtubule-templated self-assembly. Dense films of self-assembled microtubules were successfully produced, as well as patterns of both dendritic and non-dendritic bundles of microtubules. They are presented in the present paper and the mechanism of their formation is discussed. Electronic Supplementary Material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Ring‐Opening of N‐tert‐Butanesulfinylethynylaziridines with Lithium Tris(dimethylphenylsilyl)zincate: Stereoselective Access to 4‐Amino‐1‐allenylsilanes

The ring‐opening of N‐tert‐butanesulfinylethynylaziridines with lithium tris(dimethylphenylsilyl)zincate is reported. The reaction is demonstrated to be both stereoselective and stereospecific and to proceed through an anti‐S_N2′ process. Further deprotection of the nitrogen atom under mild conditions allows access to 4‐amino‐1‐(dimethylphenylsilyl)allenes with high yields and levels of stereoselectivity.

     

Measurement of the optical parameters of the Virgo interferometer

The Virgo interferometer, aimed at detecting gravitational waves, is now in a commissioning phase. Measurements of its optical properties are needed for the understanding of the instrument. We present the techniques developed for the measurement of the optical parameters of Virgo. These parameters are compared with the Virgo specifications.