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Nanopattern replication of complex structures by plastic injection is a challenge that requires simulations to define the right processing parameters. Previous work managed to simulate replication for single cavities in 2D and 3D, showing high performance requirements of CPU to simulate periodic trenches in 2D. This paper presents two ways to approach the simulation of replication of complex 3D hydrophobic surfaces. The first approach is based on previous CFD Ansys Fluent and compared to FE based CFD Polyflow software for the analysis of laminar flows typical in polymer processing and glass forming as well as other applications. The results showed that Polyflow was able to reduce computing time from 72 h to only 5 min as desired in the project. Furthermore, simulations carried out with Polyflow showed that higher injection and mold temperature lead to better replication of hydrophobicity in agreement with the experiments. Polyflow simulations are proved to be a good tool to define process parameters such as temperature and cycle times for nanopattern replication.

Nanostructured gratings fabricated on silicon chips have been successfully transferred to polypropylene plastic parts by means of injection molding. Different sets of experiments were carried out along with a repeatability analysis in order to study the effect in the replication of process parameters such as maximum injection pressure, injection time, charge and polymer temperature, geometric factors such as width and separation between lines of the gratings and flow direction as well as demolding conditions. Among all factors, the one with a larger effect is the separation between consecutive trenches, which was studied in detail through Computational Fluid Dynamics simulations. In addition, a previously not reported sinking effect in the nanostructured area and a shrinking of the pattern period were characterized and simulated. Keywords: Plastic injection molding, Nanostructured surfaces, Computational fluid dynamics, Heat transfer

The purpose of this work is to manufacture micro and nanotextured surfaces on plastic injection moulds with the aim of replicating them and obtaining plastic parts with optical applications. Different patterns are manufactured with nanosecond and femtosecond lasers in order to obtain three different optical applications: (i) homogeneous light diffusion (ii) 1D light directionality and (iii) 2D light directionality. Induction heating is used in the injections in order to improve the textures degree of replication. The steel mould and the plastic parts are analyzed with a confocal/focus variation microscope and with a surface roughness tester. A mock-up and a luminance camera are used to evaluate the homogeneity and luminance of the homogeneous light diffusion application in comparison with the current industrial solutions.

A new method to calculate damping properties of rigid materials to be used in Finite Elements calculations is presented. Its relevance relies in its simplicity regarding the amount of materials data, mathematical treatment and experimental equipment needed. Its application allows more realistic calculation of mechanical parts and structures under dynamic loading. In most of those calculations very unreal assumptions are done when simulating with Finite Elements software to assure stability of the solution. The main reason for that situation is the lack of information of damping properties of materials in databases and the complexity of the reported methodology to calculate or measure them. Another reason is the common development time for new products in industry encouraging engineers to quickly evaluate mechanical performance of the product. Recommendations to select initial parameters are presented. Critical parameters to achieve good mathematical fits of the experimental data are identified. Theoretical treatment, fitting algorithm and experimental procedure are described and proved. Several materials: plastics and ferrous and nonferrous metals are studied to demonstrate the validity of the proposed method. Finally, the method is proved in a complex hyperstatic three-dimensional structure under dynamic loading; including working under resonance conditions. Results obtained prove the validity of the method and its application to real world situations.

This paper reviews how biomedical engineers, in collaboration with physicians, biologists, chemists, physicists, and mathematicians, have developed models to explain how the impact of vascular interventions on blood flow predicts subsequent vascular repair. These models have become increasingly sophisticated and precise, propelling us toward optimization of cardiovascular therapeutics in general and personalizing treatments for patients with cardiovascular disease., Spain. Ministerio de Ciencia e Innovacion (Plan Nacional BFU2009-09804), National Institutes of Health (U.S.) (Grant NIH/NIGMS RO1/GM049039), Spain. Generalitat de Catalunya (FI-DGR 2011), Barcelona Chamber of Commerce, Fundacao Empreses IQS, POSIMAT

Fastener holes in aircraft components are routinely cold expanded to improve fatigue life, although the precise level of improvement is difficult to quantify. This paper describes an attempt to predict the growth rate of a fatigue corner crack emanating from the bore of a cold expanded hole. The prediction is made using a three-dimensional finite element model of a cold expanded hole combined with a Paris law fit to fatigue data derived from tests for corner cracks emanating from a plain hole. Residual stresses in the finite element model are calculated from a simulation of the cold expansion process. Finite element predictions of fatigue crack growth rate are compared with experimental measurements giving adequate agreement.

The cold expansion of fastener holes in aircraft components is a standard technique to improve fatigue life. There is concern that the beneficial residual stresses arising from cold expansion may relax due to creep. This paper describes experimental measurement and finite element prediction of cold expansion residual stresses and their redistribution after creep, with and without additional mechanical load. Experimental measurements of near-surface stresses used an X-ray diffraction technique while average through-the-thickness stresses were measured using a new method based on Sachs’ boring. This new method allowed non-axisymmetric residual stresses to be measured, as was the case when creep relaxation occurred with mechanical load. Axisymmetric and three dimensional finite element analyses were used to predict the stress distribution through the thickness of the component showing good agreement with measurement. Creep relaxation of residual stress does indeed occur, but some benefit of the cold expansion remains, particularly when creep relaxation is combined with the application of mechanical load.

Sachs’ boring is an established technique for the measurement of axisymmetric residual stresses in cylindrical components. There are however important cases where non-axisymmetric residual stresses need to be found. In this paper a new procedure is developed to measure non-axisymmetric residual stresses. The essential feature of the new procedure is the use of a Fourier series to represent the residual stresses. The correctness of the new procedure is demonstrated using a finite element simulation where a set of non-axisymmetric residual stresses are determined. Excellent agreement is found between the predicted residual stresses and those derived using a finite element simulation of the new procedure.

The Sachs boring technique is used widely to determine residual stresses in axisymmetric components. Several studies have attempted to use this standard method to determine residual stresses where the measured strains are non-axisymmetric. In this paper a new procedure to measure non-axisymmetric residual stresses is presented. The new method is based on a Fourier analyses of the measured strains. The analysis determines radial, tangential and shear tangential stresses as a function of angle and radial distance. The solutions provided can be applied to plane stress and plane strain conditions. The accuracy of the new method is validated using a FE simulation to generate a non-axisymmetric residual stress distribution. FE simulation of material removal and strain readings is also conducted. Finally the residual stresses are calculated using both Sachs conventional axisymmetric analysis and the new Fourier analysis. The new method determines accurately the non-axisymmetric residual stress distributions, while the conventional method provides only an average distribution.