Análisis de la información de ensayos de impacto instrumentados sobre materiales poliméricos

El ensayo de impacto se ha vuelto especialmente útil en la industria de polímeros. El inconveniente que poseen este tipo de ensayos es que la fuerza registrada no es necesariamente igual a la fuerza que actúa sobre la probeta. En esta tesis se enfrenta el problema de encontrar la verdadera respuesta carga-desplazamiento obtenida en un ensayo de fractura en condiciones de alta velocidad de deformación. Está orientada al desarrollo de una metodología de análisis y procesamiento de datos experimentales, que permite recuperar la respuesta mecánica del material, aislando los efectos dinámicos propios del ensayo. El estudio se lleva a cabo sobre materiales poliméricos comerciales, con probetas entalladas en flexión en tres puntos, SE(B). A fin de comparar el efecto del instrumento de medición sobre los resultados obtenidos, se realizan ensayos en dos equipos diferentes de impacto. Los resultados de esta tesis muestran que la metodología de análisis desarrollada es apropiada para estimar una curva de flexión muy próxima a la verdadera en un ensayo de impacto.Fil: Pettarin, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Urban air pollution by odor sources: Short time prediction

3noA numerical approach is proposed to predict the short time dispersion of odors in the urban environment. The model is based on (i) a three dimensional computational domain describing the urban topography at fine spatial scale (1 m) and on (ii) highly time resolved (1 min frequency) meteorological data used as in flow conditions. The time dependent, three dimensional wind velocity field is reconstructed in the Eulerian framework using a fast response finite volume solver of Navier-Stokes equations. Odor dispersion is calculated using a Lagrangian approach. An application of the model to the historic city of Verona (Italy) is presented. Results confirm that this type of odor dispersion simulations can be used (i) to assess the impact of odor emissions in urban areas and (ii) to evaluate the potential mitigation produced by odor abatement systems.openopenPettarin, Nicola; Campolo, Marina; Soldati, AlfredoPettarin, Nicola; Campolo, Marina; Soldati, Alfred

Analisi e sviluppo di modelli per la valutazione della dispersione di odori in contesti antropizzati

Lo scopo della tesi \ue8 quello di: (i) testare modelli numerici per la valutazione, previsione e controllo del livello di inquinamento olfattivo in aree urbane complesse, (ii) sviluppare algoritmi per la localizzazione di sorgenti odorigene sulla base di misure sparse e discontinue rilevabili da un sensore mobil

Polypropylene Blends and Composite: Processing-Morphology-Performance Relationship of Injected Pieces

Polypropylene (PP) is a low-cost plastic commodity, which currently is in a transition zone between massive use and engineering applications due mainly to its limited mechanical properties, such as low tensile and impact resistance. That is the reason why PP is usually modified with additives and particles to improve its mechanical and thermal performance and thus meet the requirements demanded by engineering applications. Besides, PP composites are suitable materials to be processed by a simple, fast, automatic, and massive technique such as injection molding. This makes PP composites attractive for several applications. However, it is important to keep in mind that PP composites’ performance depends not only on their intrinsic properties but also on processing conditions. This chapter will summarize the relationship between processing and performance of several PP composite—micro, nano, and hybrid—injected parts with the aim of generating a bridge between technologic knowledge and scientist knowledge

Making an impact with nanocomposites

Nanoclays can improve the performance of injection-molded polypropylene components likely to be subjected to impact in servic

Optimal ligament lengths in impact fracture toughness estimation by the essential work of fracture method

This work presents a statistical analysis of the confidence in fracture parameters of polymers estimated through the essential work of fracture (EWF) methodology under impact conditions. Fracture toughness parameters—essential, we, and non-essential work of fracture, wp—are obtained from the experimental relationship between specific total work of fracture wf and ligament length of the tested samples l: we is obtained from the y-intercept and wp from the slope of wf versus l in cases where a linear fit is suitable. The distribution of ligament lengths within a fixed number of samples to be tested under impact loading conditions is determined in order to minimize the uncertainty of the estimated parameters when linear reduction of the data is assumed. The statistical approach applied to two different polymeric materials shows that the uniform ligament length distribution along the ligament range is not the optimal one. We propose an optimal distribution of ligament lengths to be tested that depends on the distribution of error standard deviations of the measured work of fracture along the l-axis

Yield, impact and fracture performance of injected metallic looking polypropylene parts

Innovation, cost and weight reduction are some factors for the replacement of metals by plastics. Plastics continue to offer attractive solutions for design engineers. The metallic effect obtained by incorporation of metal particles in polymers by injection moulding has the advantage of eliminating postprocessing techniques reducing production cost and time. Nevertheless, undesired defects in the final appearance of parts are common. These defects occur due to inhomogeneous orientation and anisotropy of the metal particles. Very few studies are reporting the influence of metallic particles on the morphology development of PP parts. Therefore, this study is focused on the production of parts made of PP/metallic pigments (aluminium) by injection moulding in order to understand the influence of metallic particles on the aesthetic, morphological and mechanical properties of the parts

Tight Bounds on Information Dissemination in Sparse Mobile Networks

Motivated by the growing interest in mobile systems, we study the dynamics of information dissemination between agents moving independently on a plane. Formally, we consider $k$ mobile agents performing independent random walks on an $n$-node grid. At time $0$, each agent is located at a random node of the grid and one agent has a rumor. The spread of the rumor is governed by a dynamic communication graph process ${G_t(r) | t \geq 0}$, where two agents are connected by an edge in $G_t(r)$ iff their distance at time $t$ is within their transmission radius $r$. Modeling the physical reality that the speed of radio transmission is much faster than the motion of the agents, we assume that the rumor can travel throughout a connected component of $G_t$ before the graph is altered by the motion. We study the broadcast time $T_B$ of the system, which is the time it takes for all agents to know the rumor. We focus on the sparse case (below the percolation point $r_c \approx \sqrt{n/k}$) where, with high probability, no connected component in $G_t$ has more than a logarithmic number of agents and the broadcast time is dominated by the time it takes for many independent random walks to meet each other. Quite surprisingly, we show that for a system below the percolation point the broadcast time does not depend on the relation between the mobility speed and the transmission radius. In fact, we prove that $T_B = \tilde{O}(n / \sqrt{k})$ for any $0 \leq r < r_c$, even when the transmission range is significantly larger than the mobility range in one step, giving a tight characterization up to logarithmic factors. Our result complements a recent result of Peres et al. (SODA 2011) who showed that above the percolation point the broadcast time is polylogarithmic in $k$.Comment: 19 pages; we rewrote Lemma 4, fixing a claim which was not fully justified in the first version of the draf

Poly(acrylic acid) surface grafted polypropylene films: Near surface and bulk mechanical response

Radical photo-grafting polymerization constitutes a promising technique for introducing functional groups onto surfaces of polypropylene films. According to their final use, surface grafting should be done without affecting overall mechanical properties. In this work the tensile drawing, fracture and biaxial impact response of biaxially oriented polypropylene commercial films grafted with poly(acrylic acid) (PAA) were investigated in terms of film orientation and surface modification. The variations of surface roughness, elastic modulus, hardness and resistance to permanent deformation induced by the chemical treatment were assessed by depth sensing indentation. As a consequence of chemical modification the optical, transport and wettability properties of the films were successfully varied. The introduced chains generated a PAA-grafted layer, which is stiffer and harder than the neat polypropylene surface. Regardless of the surface changes, it was proven that this kind of grafting procedure does not detriment bulk mechanical properties of the PP film.Fil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Costamagna, Vanina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; ArgentinaFil: Pettarin, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Strumia, Miriam Cristina. Universidad Nacional de Córdoba. Facultad de Cs.agropecuarias. Departamento de Fundamentación Biológica. Cátedra de Química Organica; ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin