Selection of Die Material and Its Impact on the Multi-Material Extrusion of Bimetallic AZ31B-Ti6Al4V Components for Aeronautical Applications.

This paper investigates the effect that the selection of the die material generates on the extrusion process of bimetallic cylindrical billets combining a magnesium alloy core (AZ31B) and a titanium alloy sleeve (Ti6Al4V) of interest in aeronautical applications. A robust finite element model is developed to analyze the variation in the extrusion force, damage distribution, and wear using different die materials. The results show that die material is a key factor to be taken into account in multi-material extrusion processes. The die material selection can cause variations in the extrusion force from 8% up to 15%, changing the effect of the extrusion parameters, for example, optimum die semi-angle. Damage distribution in the extrudate is also affected by die material, mainly in the core. Lastly, die wear is the most affected parameter due to the different hardness of the materials, as well as due to the variations in the normal pressure and sliding velocity, finding critical values in the friction coefficient for which the die cannot be used for more than one forming stage because of the heavy wear suffered. These results can potentially be used to improve the efficiency of this kind of extrusion process and the quality of the extruded part that, along with the use of lightweight materials, can contribute to sustainable production approaches.

Special Issue of the Manufacturing Engineering Society 2020 (SIMES-2020).

The Special Issue of the Manufacturing Engineering Society 2020 (SIMES-2020) has been launched as a joint issue of the journals "Materials" and "Applied Sciences". The 17 contributions published in this Special Issue of Materials present cutting-edge advances in the field of Manufacturing Engineering, focusing on additive manufacturing and 3D printing; advances and innovations in manufacturing processes; sustainable and green manufacturing; manufacturing of new materials; manufacturing systems: machines, equipment and tooling; robotics, mechatronics and manufacturing automation; metrology and quality in manufacturing; Industry 4.0; design, modeling and simulation in manufacturing engineering. Among them, this issue highlights that the topic "advances and innovations in manufacturing processes" has collected a large number of contributions, followed by additive manufacturing and 3D printing; sustainable and green manufacturing; metrology and quality in manufacturing.

Reliability Prediction of Acrylonitrile O-Ring for Nuclear Power Applications Based on Shore Hardness Measurements.

The degradation of polymeric components is of considerable interest to the nuclear industry and its regulatory bodies. The objective of this work was the development of a methodology to determine the useful life-based on the storage temperature-of acrylonitrile O-rings used as mechanical sealing elements to prevent leakages in nuclear equipment. To this aim, a reliability-based approach that allows prediction of the use-suitability of different storage scenarios (that involve different storage times and temperatures) considering the further required in-service performance, is presented. Thus, experimental measurements of Shore A hardness have been correlated with storage variables (temperature and storage time). The storage (and its associated hardening) was proved to have a direct effect on in-service durability, reducing this by up to 60.40%. Based on this model, the in-service performance was predicted; after the first three years of operation the increase in probability of failure (POF) was practically insignificant. Nevertheless, from this point on, and especially, from 5 years of operation, the POF increased from 10% to 20% at approximately 6 years (for new and stored). From the study, it was verified that for any of the analysis scenarios, the limit established criterion was above that of the storage time premise considered in usual nuclear industry practices. The novelty of this work is that from a non-destructive test, like a Shore A hardness measurement, the useful life and reliability of O-rings can be estimated and be, accordingly, a decision tool that allows for improvement in the management of maintenance of safety-related equipment. Finally, it was proved that the storage strategies of our nuclear power plants are successful, perfectly meeting the expectations of suitability and functionality of the components when they are installed after storage.

Prediction of Mechanical Properties by Artificial Neural Networks to Characterize the Plastic Behavior of Aluminum Alloys.

In metal forming, the plastic behavior of metallic alloys is directly related to their formability, and it has been traditionally characterized by simplified models of the flow curves, especially in the analysis by finite element simulation and analytical methods. Tools based on artificial neural networks have shown high potential for predicting the behavior and properties of industrial components. Aluminum alloys are among the most broadly used materials in challenging industries such as aerospace, automotive, or food packaging. In this study, a computer-aided tool is developed to predict two of the most useful mechanical properties of metallic materials to characterize the plastic behavior, yield strength and ultimate tensile strength. These prognostics are based on the alloy chemical composition, tempers, and Brinell hardness. In this study, a material database is employed to train an artificial neural network that is able to make predictions with a confidence greater than 95%. It is also shown that this methodology achieves a performance similar to that of empirical equations developed expressly for a specific material, but it provides greater generality since it can approximate the properties of any aluminum alloy. The methodology is based on the usage of artificial neural networks supported by a big data collection about the properties of thousands of commercial materials. Thus, the input data go above 2000 entries. When the relevant information has been collected and organized, an artificial neural network is defined, and after the training, the artificial intelligence is able to make predictions about the material properties with an average confidence greater than 95%.

Special Issue of the Manufacturing Engineering Society 2019 (SIMES-2019).

The Special Issue of the Manufacturing Engineering Society 2019 (SIMES-2019) has been launched as a joint issue of the journals "Materials" and "Applied Sciences". The 29 contributions published in this Special Issue of Materials present cutting-edge advances in the field of manufacturing engineering focusing on additive manufacturing and 3D printing, advances and innovations in manufacturing processes, sustainable and green manufacturing, manufacturing of new materials, metrology and quality in manufacturing, industry 4.0, design, modeling, and simulation in manufacturing engineering and manufacturing engineering and society. Among them, these contributions highlight that the topic "additive manufacturing and 3D printing" has collected a large number of contributions in this journal because its huge potential has attracted the attention of numerous researchers over the last years.

Considerations on the Applicability of Test Methods for Mechanical Characterization of Materials Manufactured by FDM.

The lack of specific standards for characterization of materials manufactured by Fused Deposition Modelling (FDM) makes the assessment of the applicability of the test methods available and the analysis of their limitations necessary; depending on the definition of the most appropriate specimens on the kind of part we want to produce or the purpose of the data we want to obtain from the tests. In this work, the Spanish standard UNE 116005:2012 and international standard ASTM D638-14:2014 have been used to characterize mechanically FDM samples with solid infill considering two build orientations. Tests performed according to the specific standard for additive manufacturing UNE 116005:2012 present a much better repeatability than the ones according to the general test standard ASTM D638-14, which makes the standard UNE more appropriate for comparison of different materials. Orientation on-edge provides higher strength to the parts obtained by FDM, which is coherent with the arrangement of the filaments in each layer for each orientation. Comparison with non-solid specimens shows that the increase of strength due to the infill is not in the same proportion to the percentage of infill. The values of strain to break for the samples with solid infill presents a much higher deformation before fracture.

An Experimental and Numerical Analysis of the Compression of Bimetallic Cylinders.

This paper investigates the upsetting of bimetallic cylinders with an aluminum alloy center and a brass ring. The influence of the center-ring shape factor and type of assembly fit (interference and clearance), and the effect of friction on the compression force and ductile damage are comprehensively analyzed by means of a combined numerical-experimental approach. Results showed that the higher the shape factor, the lower the forces required, whereas the effect of friction is especially important for cylinders with the lowest shape factors. The type of assembly fit does not influence the compression force. The accumulated ductile damage in the compression of bimetallic cylinders is higher than in single-material cylinders, and the higher the shape factor, the lower the damage for the same amount of stroke. The highest values of damaged were found to occur at the middle plane, and typically in the ring. Results also showed that an interference fit was more favorable for preventing fracture of the ring than a clearance fit. Microstructural analysis by scanning electron microscopy revealed a good agreement with the finite element predicted distribution of ductile damage.

One-year rehospitalisations for congestive heart failure in Portuguese NHS hospitals: a multilevel approach on patterns of use and contributing factors.

OBJECTIVES: Identification of rehospitalisations for heart failure and contributing factors flags health policy intervention opportunities designed to deliver care at a most effective and efficient level. Recognising that heart failure is a condition for which timely and appropriate outpatient care can potentially prevent the use of inpatient services, we aimed to determine to what extent comorbidities and material deprivation were predictive of 1 year heart failure specific rehospitalisation. SETTING: All Portuguese mainland National Health Service (NHS) hospitals. PARTICIPANTS: A total of 68 565 hospitalisations for heart failure principal cause of admission, from 2011 to 2015, associated to 45 882 distinct patients aged 18 years old or over. OUTCOME MEASURES: We defined 1 year specific heart failure rehospitalisation and time to rehospitalisation as outcome measures. RESULTS: Heart failure principal diagnosis admissions accounted for 1.6% of total hospital NHS budget, and over 40% of this burden is associated to patients rehospitalised at least once in the 365-day follow-up period. 22.1% of the patients hospitalised for a principal diagnosis of heart failure were rehospitalised for the same cause at least once within 365 days after previous discharge. Nearly 55% of rehospitalised patients were readmitted within 3 months. Results suggest a mediation effect between material deprivation and the chance of 1 year rehospitalisation through the effect that material deprivation has on the prevalence of comorbidities. Heart failure combined with chronic kidney disease or chronic obstructive pulmonary disease increases by 2.8 and 2.2 times, respectively, the chance of the patient becoming a frequent user of inpatient services for heart failure principal cause of admission. CONCLUSIONS: One-fifth of patients admitted for heart failure are rehospitalised due to heart failure exacerbation. While the role of material deprivation remained unclear, comorbidities considered increased the chance of 1 year heart failure specific rehospitalisation, in particular, chronic kidney disease and chronic obstructive pulmonary disease.

Special Issue of the Manufacturing Engineering Society (MES).

Research in the field of materials is very broad, ranging from studies on the structure and properties at the atomic or molecular level to the most complex or sophisticated applications that can be done with them, as well as studies about other aspects related to their processing, use or management. The Special Issue of the Manufacturing Engineering Society (MES), published in the Section "Manufacturing Processes and Systems" of the journal Materials, focuses, mainly, on the applications and key processing aspects of materials, collecting a set of 48 original papers focused on the field of manufacturing engineering and materials processing.

Analysis of Favorable Process Conditions for the Manufacturing of Thin-Wall Pieces of Mild Steel Obtained by Wire and Arc Additive Manufacturing (WAAM).

One of the challenges in additive manufacturing (AM) of metallic materials is to obtain workpieces free of defects with excellent physical, mechanical, and metallurgical properties. In wire and arc additive manufacturing (WAAM) the influences of process conditions on thermal history, microstructure and resultant mechanical and surface properties of parts must be analyzed. In this work, 3D metallic parts of mild steel wire (American Welding Society-AWS ER70S-6) are built with a WAAM process by depositing layers of material on a substrate of a S235 JR steel sheet of 3 mm thickness under different process conditions, using as welding process the gas metal arc welding (GMAW) with cold metal transfer (CMT) technology, combined with a positioning system such as a computer numerical controlled (CNC) milling machine. Considering the hardness profiles, the estimated ultimate tensile strengths (UTS) derived from the hardness measurements and the microstructure findings, it can be concluded that the most favorable process conditions are the ones provided by CMT, with homogeneous hardness profiles, good mechanical strengths in accordance to conditions defined by standard, and without formation of a decohesionated external layer; CMT Continuous is the optimal option as the mechanical properties are better than single CMT.

The Influence of Manufacturing Parameters on the Mechanical Behaviour of PLA and ABS Pieces Manufactured by FDM: A Comparative Analysis.

This paper presents a comparative study of the tensile mechanical behaviour of pieces produced using the Fused Deposition Modelling (FDM) additive manufacturing technique with respect to the two types of thermoplastic material most widely used in this technique: polylactide (PLA) and acrylonitrile butadiene styrene (ABS). The aim of this study is to compare the effect of layer height, infill density, and layer orientation on the mechanical performance of PLA and ABS test specimens. The variables under study here are tensile yield stress, tensile strength, nominal strain at break, and modulus of elasticity. The results obtained with ABS show a lower variability than those obtained with PLA. In general, the infill percentage is the manufacturing parameter of greatest influence on the results, although the effect is more noticeable in PLA than in ABS. The test specimens manufactured using PLA perform more rigidly and they are found to have greater tensile strength than ABS. The bond between layers in PLA turns out to be extremely strong and is, therefore, highly suitable for use in additive technologies. The methodology proposed is a reference of interest in studies involving the determination of mechanical properties of polymer materials manufactured using these technologies.

Determination of Actual Friction Factors in Metal Forming under Heavy Loaded Regimes Combining Experimental and Numerical Analysis.

Tribological conditions can change drastically during heavy loaded regimes as experienced in metal forming; this is especially critical when lubrication can only be applied at the early stage of the process because the homogeneous lubricant layer can break along the die-workpiece interface. In these cases, adopting a constant friction factor for the lubricant-surface pair may not be a valid assumption. This paper presents a procedure based on the use of dual friction factor maps to determine friction factors employed in heavy loaded regimes. A finite element (FE) simulation is used to obtain the friction factor map for the alloy UNS A96082. Experiments were conducted using four lubricants (aluminum anti-size, MoS2 grease, silicone oil, and copper paste) to determine the actual friction curves. The experimental procedure is based on the application of lubricant only at the beginning of the first stage of ring compression, and not at intermediate stages as is usual in typical ring compression tests (RCTs). The results show that for small reductions (rh < 20%), the conventional RCT can be applied because the tribological conditions remain similar. For large reductions (rh > 20%), it is recommended to obtain an average value of the friction factor for every lubricant-surface pair in the range of deformation considered.

Práctica clínica cotidiana frente a la evidencia científica en el manejo fisioterapéutico del dolor lumbar crónico inespecífico / Daily Clinical Practice of Scientific Evidence in the Physiotherapeutic Management of Chronic Nonspecific Low Back Pain / Prática clínica cotidiana versus a evidência científica no manejo fisioterapêutico da dor lombar crónica inespecífica

Introducción: El 80% de los adultos experimenta dolor lumbar por lo menos una vez en su vida. El dolor lumbar es la tercera causa de consulta en urgencias, la cuarta en medicina general, la segunda de pensión por invalidez y la primera de reubicación laboral. Objetivo: Comparar los criterios que orientan la toma de decisiones de un grupo de fisioterapeutas en Bogotá, Colombia para el manejo del dolor lumbar crónico inespecífico con los criterios de manejo contenidos en la guía COST B13 (European Guidelines for the Management of Chronic Non-Specific Low Back Pain, 2004). Materiales y método: Se trató de un estudio descriptivo, en el cual se seleccionó la guía de práctica clínica COST B13 para el manejo de dolor lumbar crónico inespecífico mediante la herramienta AGREE y se aplicó una encuesta a 50 fisioterapeutas por medio de un muestreo por conveniencia con el fin de comparar las prácticas clínicas que se realizan frente a las recomendaciones dadas en la guía. Resultados: El 56% de los encuestados contaba con algún tipo de entrenamiento para el manejo del dolor lumbar crónico inespecífico (DLCI). El 94% de los pacientes con DLCI atendidos oscilan en edades de 40 a 59 años, con predominio del sexo femenino. El 80% de los fisioterapeutas encuestados manifestó que la ayuda diagnóstica con la que cuentan para el manejo de los pacientes es la imagen radiológica. El 80% de los fisioterapeutas evalúa la variable de dolor lumbar experimentado por el paciente y el 54% la postura. Otros aspectos fueron reportados en menor porcentaje como test neurales, rangos de movimiento y pruebas de flexibilidad muscular. En el tratamiento del DLCI, los fisioterapeutas reportan hacer uso de los estiramientos en el 80% de los casos, la termoterapia superficial, en el 70% y el fortalecimiento muscular isométrico, en el 70%, todos con resultados favorables. Conclusión: Existen diferencias entre la práctica clínica y los lineamientos contenidos en las recomendaciones dadas por la guía COST B13 para DLCI, principalmente en los procesos de evaluación clínica, ya que suelen estar centrados en la observación y no siempre en la medición rigurosa, lo que dificulta la posibilidad de establecer indicadores de proceso y desenlace en el diagnóstico y tratamiento de los pacientes con DLCI.

Introduction: 80% of adults experience back pain at least once in their life.Back pain is the third leading cause of consultation in the emergency room, the fourth in general practice, the second of disability pension and the first job relocation. Objective: To compare criteria that guide decision making of a group of physiotherapists in Bogota, Colombia, for managing chronic nonspecific low back pain management criteria contained in the guide COST B13 (European Guidelines for the Management of Chronic Non-Specific Low Back Pain, 2004). Material and methods: This was a descriptive study, for which the clinical practice guideline COST B13 for the management of chronic nonspecific low back pain through the AGREE tool is selected. A survey was applied to 50 physiotherapists through a convenience sample to compare the clinical practices performed with the recommendations given guidance. Results: 56% of respondents had some type of training for the management of chronic nonspecific low back pain (cnlbp). 94% of attended patients with cnlbp ranged ages from 40 to 59, with female predominance. 80% of respondents stated that physiotherapists' diagnostic help with counting for the management of patients is the radiological image. 80 % of physiotherapists evaluate the variable of experienced lumbar pain based on what the patient says and 54% based on the posture. Other aspects reported rated lower percentages. In the treatment of cnlbp, physiotherapists reported the use of stretching in 80% of cases; superficial thermotherapy in 70% and isometric muscle strength in 70% of cases, all with favorable results. Conclusion: There are differences between the physiotherapists' clinical practice of and the guidelines contained in the recommendations of the in the cnlbp cost B13 guide. Mainly in the processes of physiotherapeutic assessment, as they are often focused on observation and not always in the rigorous measurement, which makes it difficult to establish process indicators and results in the diagnosis and treatment of patients with cnlbp.

Introdução: o 80% dos adultos experimenta dor lombar pelo menos uma vez em sua vida; a dor lombar é a terceira causa de consulta em emergências, a quarta em medicina geral, a segunda de pensão por invalidez e a primeira de deslocalização laboral. Objetivo: Comparar os critérios que orientam a tomada de decisões de um grupo de fisioterapeutas em Bogotá, Colômbia, para o manejo da dor lombar crónica inespecífico com os critérios de manejo conteúdos na guia COST B13 (European Guidelines for the Management of Chronic Non-Specific Low Back Pain, 2004). Materiais e métodos: tratou-se de um estudo descritivo, no qual se selecionou a guia de prática clínica COSTB 13 para o manejo de dor lombar crónico inespecífico através da ferramenta AGREE e se aplicou uma enquete a 50 fisioterapeutas através de uma amostragem por conveniência com o fim de comparar as práticas clínicas que se realizam frente às recomendações dadas na guia. Resultados: o 56% dos questionados contavam com algum tipo de treinamento para o manejo da dor lombar crónico inespecífico (DLCI). O 94% dos pacientes com DLCI atendidos oscilam em idades de 40 a 59 anos, com predomínio do sexo feminino. O 80% dos fisioterapeutas avalia a variável de dor lombar experimentado pelo paciente e o 54% a postura. Outros aspectos foram reportados em menor porcentagem como teste neurais, rasgos de movimentos, e provas de flexibilidade muscular. No tratamento da DLCI, os fisioterapeutas reportam fazer uso dos estiramentos no 80% dos casos, a termoterapia superficial no 70% e o fortalecimento muscular isométrico no 70%, todos com resultados favoráveis. Conclusões: Existem diferenças entre a prática clínica e os lineamentos conteúdos nas recomendações dadas pela guia COST B12 para DLCI principalmente nos processos de avaliação clínica devido a que costumam estar centrados na observação e não sempre na medição rigorosa o que dificulta a possibilidade de estabelecer indicadores de processo e desenlace no diagnóstico e tratamento dos pacientes com DLCI.

Application of an instrumental and computational approach for improving the vibration behavior of structural panels using a lightweight multilayer composite.

This work presents a hybrid (experimental-computational) application for improving the vibration behavior of structural components using a lightweight multilayer composite. The vibration behavior of a flat steel plate has been improved by the gluing of a lightweight composite formed by a core of polyurethane foam and two paper mats placed on its faces. This composite enables the natural frequencies to be increased and the modal density of the plate to be reduced, moving about the natural frequencies of the plate out of excitation range, thereby improving the vibration behavior of the plate. A specific experimental model for measuring the Operating Deflection Shape (ODS) has been developed, which enables an evaluation of the goodness of the natural frequencies obtained with the computational model simulated by the finite element method (FEM). The model of composite + flat steel plate determined by FEM was used to conduct parametric study, and the most influential factors for 1st, 2nd and 3rd mode were identified using a multifactor analysis of variance (Multifactor-ANOVA). The presented results can be easily particularized for other cases, as it may be used in cycles of continuous improvement as well as in the product development at the material, piece, and complete-system levels.