A mesoscale approach to simulate residual deformations in complex laser welding processes

Laser welding can be characterized by very small radii of beam, in the order of tenths of a millimeter, and very short high power inputs (more kW in few ms), and thus, it can be certainly classified as a microscale process with a high level of physical complexity. This is clearly incompatible, due to the high computational costs, with the analysis of macroscale processes related to large geometries and non-uniform welding patterns. In order to overcome this issue, a simplified finite element method (FEM)–based thermo-elastoplastic model is presented to simulate heat transfer and residual deformations due to thermal expansion and material plasticity. The idea is to substitute the microscale analysis with a mesoscale approach that renounces to describe in detail all the physical phenomena occurring in the heated zone and focuses attention on the correct prediction of the keyhole depth and weld pool size, that are the most important para meters to describe the mechanical characteristics of the welded joint. The concept of passive element, based on the numerical adjustment of the material properties in order to take into account the orthotropic behavior during the key hole formation, is introduced. In particular, the new approach has been tested on the pulsed laser welding process of two overlapping DC04 steel plates with thickness of 0.5 mm (so-called sandwich) and validated through experimental tests involving different input parameters, such as power, pulse duration and frequency, speed, and geometrical pattern

Multifidelity Recursive Cokriging for Dynamic Systems' Response Modification

In order to perform the accurate tuning of a machine and improve its performance to the requested tasks, the knowledge of the reciprocal influence among the system\u2019s parameters is of paramount importance to achieve the sought result with minimum effort and time. Numerical simulations are an invaluable tool to carry out the system optimization, but modeling limitations restrict the capabilities of this approach. On the other side, real tests and measurements are lengthy, expensive, and not always feasible. This is the reason why a mixed approach is presented in this work. The combination, through recursive cokriging, of low-fidelity, yet extensive, numerical model results, together with a limited number of highly accurate experimental measurements, allows to understand the dynamics of the machine in an extended and accurate way. The results of a controllable experiment are presented and the advantages and drawbacks of the proposed approach are also discussed

Uncertainty Quantification of Turbulence Model Applied to a Cavitating Hydrofoil

This paper presents the Global Sensitivity Analysis of the coefficients of the standard k-ε turbulence model used in RANS (Reynolds Averaged Navier-Stokes) simulations aimed to predict the flow around a bi-dimensional hydrofoil operating at non-cavitating and cavitating flow regimes. The sensitivity analysis is treated by the Sobol Decomposition, where the Sobol Indices are computed through the Polynomial Chaos Expansion of the 2-nd order with a Point-Collocation Non-Intrusive approach. From the current results, it seems that the considered cavitating flow regime is less sensitive to the variability of the input parameters, at least for the prediction of lift and drag

Protein trafficking through the endosomal system prepares intracellular parasites for a home invasion

Toxoplasma (toxoplasmosis) and Plasmodium (malaria) use unique secretory organelles for migration, cell invasion, manipulation of host cell functions, and cell egress. In particular, the apical secretory micronemes and rhoptries of apicomplexan parasites are essential for successful host infection. New findings reveal that the contents of these organelles, which are transported through the endoplasmic reticulum (ER) and Golgi, also require the parasite endosome-like system to access their respective organelles. In this review, we discuss recent findings that demonstrate that these parasites reduced their endosomal system and modified classical regulators of this pathway for the biogenesis of apical organelles

Distributed Lagrange Multiplier Functions for Fictitious Domain Method with Spectral/hp Element Discretization

A fictitious domain approach for the solution of second-order linear differential problems is proposed; spectral/hp elements have been used for the discretization of the domain. The peculiarity of our approach is that the Lagrange multipliers are particular distributed functions, instead of classical \u3b4 Dirac (impulsive)multipliers. In this paper we present the formulation and the application of this approach to 1D and 2D Poisson problems and 2D Stokes flow (biharmonic equation)

Estudo retrospectivo de cães e gatos portadores de corpos estranhos gastrointestinais : análise de 44 casos (2013 a 2018)

Obstruções causadas por corpos estranhos no trato gastrointestinal são comumente encontradas na rotina de atendimento clínico veterinário de pequenos animais. Os objetivos deste trabalho são apresentar um estudo retrospectivo dos pacientes com ingestão de corpos estranhos encaminhados para o Serviço de Endoscopia e Gastroenterologia da Universidade Federal do Rio Grande do Sul. Foram analisados o perfil dos pacientes, os locais mais comuns de obstrução, os tipos de objetos mais encontrados, os métodos diagnósticos mais solicitados e o tipo de tratamento mais utilizado. Foram incluídos 44 pacientes de janeiro de 2013 a novembro de 2018, sendo a espécie canina a mais cometida, com 77,3 % dos casos (n = 34). Já os felinos corresponderam a 22,7% (n = 10). A representação de acordo com o sexo foi bastante homogênea (52,9% e 60% machos) para cães e gatos, a mediana das idades 4,00 (cães) e 3,00 (gatos) e o peso médio dos cães foi de 14,0 10,6 kg e dos gatos de 3,4 1,0 kg. A endoscopia foi o método diagnóstico mais solicitado e também o método de tratamento mais utilizado apresentando altas taxas de sucesso e baixas taxas de complicações. Concluímos que ambas espécies foram mais acometida por corpos estranhos não lineares. A localização mais frequente foi no estômago. O envolvimento de cães com peso superior a dez quilogramas e adultos em torno de quatro anos de idade pode sugerir doenças digestórias subjacentes; assim, a biópsia gastrointestinal pode ser uma importante ferramenta no manejo de cães e gatos portadores de corpos estranhos.Gastrointestinal foreign bodies are commonly encountered in routine clinical veterinary care of pets. The objectives of this study are to present a retrospective investigation of patients with foreign body ingestion referred to the Endoscopy and Gastroenterology Service of the Federal University of Rio Grande do Sul. Patients’ profile, the most common sites of obstruction, the types of objects found, the most requested diagnostic methods, and the type of treatment most used, were analyzed. A total of 44 patients were included from January 2013 to November 2018, with the canine species being affected in 77.3% of cases (n = 34) and the feline species in 22.7% (n = 10). According to sex, representation was quite homogeneous for dogs (52.9% males) and cats (60% males), the median age was 4.00 (dogs) and 3.00 years (cats), the mean weight of dogs was 14.0 10.6 kg and cats was 3.4 1.0 kg. Endoscopy was the most requested diagnostic method and also the most frequently used treatment method, presenting high rates of success and low complication rates. We conclude that both species were more affected by non linear foreign bodies and the most frequent location was the stomach. The involvement of dogs weighing more than ten kilograms and adult animal around the age of four years may suggest underlying digestive diseases, and gastrointestinal biopsy may be an important tool in the management of dogs and cats with foreign bodies

El proceso de suburbanización del cordón oeste metropolitano de Rosario. Ideas de ciudad.

Las aglomeraciones urbanas actuales han integrado espacial y funcionalmente a las ciudades próximas, mediante un proceso de transformación territorial caracterizado por la expansión urbana dispersa. La suburbanización resulta hoy uno de los principales patrones de desarrollo de las grandes ciudades. El caso de estudio se presenta como una estribación metropolitana de la ciudad de Rosario, que configura al Cordón Oeste Metropolitano, y ha experimentado un proceso de suburbanización vinculado con las expansiones urbanas de la ciudad central, que comenzó a principios de los años 60 y se intensificó en los años 90. Este cordón ofrece un área de esparcimiento, recreación y descanso debido a sus condiciones naturales y a su gran forestación. Su proceso se concretó mediante sucesivas operaciones inmobiliarias, ventas de loteos de fin de semana o viviendas permanentes y la incorporación de nuevas urbanizaciones de tipo cerrado, en donde se presentan características propias del modelo de ciudad jardín

El proceso de suburbanización del cordón oeste metropolitano de Rosario. Ideas de ciudad.

Las aglomeraciones urbanas actuales han integrado espacial y funcionalmente a las ciudades próximas, mediante un proceso de transformación territorial caracterizado por la expansión urbana dispersa. La suburbanización resulta hoy uno de los principales patrones de desarrollo de las grandes ciudades. El caso de estudio se presenta como una estribación metropolitana de la ciudad de Rosario, que configura al Cordón Oeste Metropolitano, y ha experimentado un proceso de suburbanización vinculado con las expansiones urbanas de la ciudad central, que comenzó a principios de los años 60 y se intensificó en los años 90. Este cordón ofrece un área de esparcimiento, recreación y descanso debido a sus condiciones naturales y a su gran forestación. Su proceso se concretó mediante sucesivas operaciones inmobiliarias, ventas de loteos de fin de semana o viviendas permanentes y la incorporación de nuevas urbanizaciones de tipo cerrado, en donde se presentan características propias del modelo de ciudad jardín

Design Optimization Based on Multi-fidelity Metamodels

This paper illustrates how multi-fidelity metamodels can be efficiently applied to save time and costs in parametric design optimization, which normally requires simulating numerically a large number of designs. Datasets of high fidelity (HF) and middle-low fidelity (LF) simulations, obtained for instance from computational models solved by grid discretizations of different accuracy, can be used together to feed the surrogate model, improving the accuracy of the response function prediction and reducing the overall computational cost at the same time. The methodologies proposed in this paper include adaptive Design of Experiments algorithms to define the optimal dataset of design simulations, and efficient multi-fidelity surrogate methods for scalar fields (Cokriging) and vector fields (Reduced Order Models). All the methods are tested and applied to CFD test cases

Integration of multi-fidelity methods in parametrized non-intrusive reduced order models for industrial applications

Exploring the behavior of complex industrial problems might become burdensome, especially in high-dimensional design spaces. Reduced Order Models (ROMs) aim to minimize the computational effort needed to study different design choices by exploiting already available data. In this work, we propose a methodology where the full-order solution is replaced with a Proper Orthogonal Decomposition based ROM, enhanced by a multi-fidelity surrogate model. Multi-fidelity approaches allow to exploit heterogeneous information sources, and consequently reduce the cost of creating the training data needed to build the ROM. To explore the multi-fidelity ROM capabilities, we present and discuss results and challenges for an automotive aerodynamic application, based on a geometric morphing of the DrivAer test case with multi-fidelity fluid-dynamics simulations