Advanced Approaches Applied to Materials Development and Design Predictions

This thematic issue on advanced simulation tools applied to materials development and design predictions gathers selected extended papers related to power generation systems, presented at the XIX International Colloquium on Mechanical Fatigue of Metals (ICMFM XIX), organized at University of Porto, Portugal, in 2018. In this issue, the limits of the current generation of materials are explored, which are continuously being reached according to the frontier of hostile environments, whether in the aerospace, nuclear, or petrochemistry industry, or in the design of gas turbines where efficiency of energy production and transformation demands increased temperatures and pressures. Thus, advanced methods and applications for theoretical, numerical, and experimental contributions that address these issues on failure mechanism modeling and simulation of materials are covered. As the Guest Editors, we would like to thank all the authors who submitted papers to this Special Issue. All the papers published were peer-reviewed by experts in the field whose comments helped to improve the quality of the edition. We also would like to thank the Editorial Board of Materials for their assistance in managing this Special Issue

Influencing parameters on the fracture resistance of aluminum alloys.

Massachusetts Institute of Technology, Dept. of Civil Engineering. Thesis. 1971. M.S.MICROFICHE COPY ALSO AVAILABLE IN BARKER ENGINEERING LIBRARY.Includes bibliographical references.M.S

Étude des effets des paramètres de fabrication additive et de post-traitement thermique sur la microstructure et les performances mécaniques des aciers inoxydables : investigation, modélisation et optimisation des performances des aciers inoxydables en fonction des paramètres du procédé de fusion sélective par laser et des paramètres de post-traitement thermique

RÉSUMÉ : Les aciers inoxydables sont parmi les alliages les plus appréciés pour la fabrication additive vu leurs propriétés attrayantes et leur large gamme d'applications. En raison de l'histoire thermique compliquée et de taux de refroidissement élevé, la fusion sélective au laser (SLM) a introduit une microstructure hors équilibre, qui contrôle le comportement mécanique. De plus, un choix inapproprié des paramètres de fabrication conduit à la formation de défauts et affecte la qualité de la pièce finale. Cette étude vise à fournir une compréhension approfondie de la corrélation entre le processus, la microstructure et les propriétés de l'acier inoxydable fabriqué par SLM afin de mieux contrôler et optimiser ces propriétés. La première partie de ce mémoire présente une revue de littérature de la microstructure, du comportement mécanique, de la résistance à la fatigue, ainsi que de la résistance à la corrosion des aciers inoxydables fabriqués par SLM. Cette revue met en évidence la capacité du procédé SLM à produire des composants en acier inoxydable de haute performance et souligne les perspectives et les limites dans ce domaine. Le but de la deuxième partie est d'élucider l'influence des paramètres de procédé sur la densité, la rugosité de surface et les propriétés mécaniques de l'acier inoxydable 316L fabriqué par SLM. Une méthodologie systématique basée sur la méthode de Taguchi, l'analyse de variance et la méthode de surface de réponse a été utilisée pour déterminer les facteurs significatifs et développer des modèles prédictifs pour les variables de réponse en fonction de ces facteurs. La troisième partie utilise une approche similaire pour étudier l'influence des paramètres de post-traitement thermique sur la microstructure et la microdureté des aciers inoxydables 15-5 PH. Les résultats de ce projet de recherche peuvent être utilisés comme outils de conception pour prédire et optimiser avec précision les performances des aciers inoxydables fabriqués par SLM. -- Mot(s) clé(s) en français : Fabrication additive, Fusion sélective au laser, Acier inoxydable, Taguchi, ANOVA. -- ABSTRACT : Stainless steels are among the most popular alloys for additive manufacturing owing to their attractive properties and their wide range of applications. Because of the complicated thermal history and high cooling rate, Selective Laser Melting (SLM) introduced a unique out-of-equilibrium microstructure, which controls the mechanical behavior. Moreover, inappropriate choice of processing parameters leads to defect formation and affects final part quality. This study aims to provide a deep understanding of the correlation between process, microstructure, and properties of SLM processed stainless steel in order to better control and optimize these properties. The first part of this thesis presents a review of the microstructure, mechanical and fatigue behavior, as well as corrosion resistance of stainless steels manufactured using SLM. This review highlights the capability of the SLM process to produce high-performance stainless steel components and sheds light on the perspectives and limitations in this field. The purpose of the second part is to elucidate the influence of process parameters on density, surface roughness, and mechanical properties of SLM-processed 316L stainless steel. A systematic methodology based on Taguchi design, Analysis of Variance, and Response Surface Method has been employed to determine the significant factors and develop predictive models for response variables with respect to these factors. The third part uses a similar approach to investigate the influence of post-heat treatment parameters on the microstructure and microhardness of 15-5 PH stainless steels. The findings of this research can be used as design tools to accurately predict and optimize the performance of SLM-processed stainless steels. -- Mot(s) clé(s) en anglais : Additive Manufacturing, Selective Laser Melting, Stainless steel, Taguchi, ANOVA

National Aeronautics and Space Administration (NASA)/American Society for Engineering Education (ASEE) Summer Faculty Fellowship Program, 1992, volume 1

The 1992 Johnson Space Center (JSC) National Aeronautics and Space Administration (NASA)/American Society for Engineering Education (ASEE) Summer Faculty Fellowship Program was conducted by the University of Houston and JSC. The program at JSC, as well as the programs at other NASA Centers, was funded by the Office of University Affairs, Washington, DC. The objectives of the program, which began nationally in 1964 and at JSC in 1965, are (1) to further the professional knowledge of qualified engineering and science faculty members; (2) to stimulate an exchange of ideas between participants and NASA; (3) to enrich and refresh the research and teaching activities of participants' institutions; and (4) to contribute to the research objective of the NASA Centers. This document is a compilation of the final reports 1 through 12

Technology 2001: The Second National Technology Transfer Conference and Exposition, volume 1

Papers from the technical sessions of the Technology 2001 Conference and Exposition are presented. The technical sessions featured discussions of advanced manufacturing, artificial intelligence, biotechnology, computer graphics and simulation, communications, data and information management, electronics, electro-optics, environmental technology, life sciences, materials science, medical advances, robotics, software engineering, and test and measurement

Ultrasonic welding of thermoplastics

Ultrasonic welding (UW) is not only a well-known industrial process but it has also been an active research area. Materials ranging from metals to non-metals e.g. polymers and from virgin materials to non-virgin materials e.g. composites are easily welded using this welding technique. Some research has already been carried out but more thorough analysis is needed on ultrasonic welding of thermoplastics. Two thermoplastics selected for this research are commercially known as Acrylo-nitrile-Butadiene Styrene (ABS) and Polypropylene (PP). ABS belongs to amorphous type of thermoplastic, whereas PP is semi-crystalline thermoplastic. Owing to this dissimilarity in their molecular structure, ultrasonic welding of these two plastics has already been considered to be different. Energy director (ED) is usually protruded on anyone of the samples to be welded. Ultrasonic energy is uniformly driven in the presence of energy director at a localized area between the samples. In this research, triangular (TRI) and semi-circular (SEMI) energy directors (ED) were protruded on the surface of specimen by designing and manufacturing injection molds. Tensile testing in shear was performed for measuring lap shear strength of joints after being welded ultrasonically at constant strain rate of 3.24 mm/minute. Maximum LSS (lap shear strength) of 17 MPa and 6 MPa were found for ABS with TRI ED and PP with SEMI ED respectively. In other words, these LSSs (lap shear strengths) were 34% and 14.63% of base material strength for ABS and PP respectively. In this work, a statistical analysis (General Linear Model) was also used to deduce meaningful information from experimentation for both materials. For different factor settings, percent change in LSS was also calculated. Maximum percent change in LSS was found for weld time e.g. 2682 and 76.67 from low to high level was computed for ABS and PP respectively. Similarly, 55 & 47.2 for amplitude and 41 & 6 for static force were calculated with ABS & PP respectively. Percent change in LSS of 409 and 47 was also evaluated from SEMI to TRI and TRI to SEMI EDs for ABS and PP respectively. All the factors appeared to be significant to affect the LSS but weld time was found to be the most significant to achieve the higher bond strength. After doing the GLM (General Linear Model) analysis, some interesting results were also highlighted. Experimental techniques were used to investigate the main reasons for these findings. Difference in softening temperatures, viscosities, temperature spreads, ED collapses, heat affected zones (HAZ) and fractured surfaces for both materials were used to determine the reasons for interesting effects. For example, low static force was required for ABS in gaining higher LSS due to its lower softening temperature and viscosity drop at weld zone. Thus this work presented new and deeper understanding of the ultrasonic welding of thermoplastics. Various hypotheses were also made after having gone through the literature. Experimental tools were also used to test these hypotheses. These technical tools included differential scanning calorimeter (DSC), melt flow index (MFI) tests, finite element analysis (FEA), high speed video camera (HSVC) and microscopy (optical and scanning electron). These tools helped approve or disapprove the hypotheses. Viscoelastic heating was considered to be crucial mechanism in joining thermoplastics ultrasonically. Viscoelastic heating was depending mainly upon loss modulus, applied frequency and strain amplitude. Weld strength further depended upon the temperature development at weld interface. Apart from above description, simulation based on FEA was also validated for its accuracy and precision. A good match was found between experimental and simulated results

The Use and Characterization of Aluminum Based Metallic Paints in Early Twentieth Century Paintings

This paper presents the results of research into the composition and use of metallic aluminum paints in three paintings by Australian artists from the first half of the twentieth century as well as a contemporary can of aluminum stove paint. A brief history of the development of aluminum paint and its uses is presented. The material characteristics of aluminum powders and binders used with them are described, as well as the effects variations of components have on resulting paint films. Analyses found leafing aluminum flakes and nitrocellulose binder on two paintings and identified coumarone as the binder for the stove pain

From bulk to structural failure: fracture of hyperelastic materials

This thesis investigates the fracture of nearly incompressible hyperelastic media. It covers the different characteristics of bulk material failure under dilatational or distortional loads and develops a unified description of the corresponding failure surface. It proposes a coupled strain and energy failure criterion for the assessment of notch-induced crack nucleation and presents a weak interface model that allows for efficient stress, strain and failure analyses of hyperelastic adhesive lap joints. Theoretical concepts for the measurement of fracture properties of nonlinear elastic materials are provided. The methodology is developed using two exemplary hyperelastic silicones, DOWSIL 993 Structural Glazing Sealant and DOWSIL Transparent Structural Silicone Adhesive, and is validated using large sets of experiments of different loading conditions

Micro-Electro Discharge Machining: Principles, Recent Advancements and Applications

Micro electrical discharge machining (micro-EDM) is a thermo-electric and contactless process most suited for micro-manufacturing and high-precision machining, especially when difficult-to-cut materials, such as super alloys, composites, and electro conductive ceramics, are processed. Many industrial domains exploit this technology to fabricate highly demanding components, such as high-aspect-ratio micro holes for fuel injectors, high-precision molds, and biomedical parts.Moreover, the continuous trend towards miniaturization and high precision functional components boosted the development of control strategies and optimization methodologies specifically suited to address the challenges in micro- and nano-scale fabrication.This Special Issue showcases 12 research papers and a review article focusing on novel methodological developments on several aspects of micro electrical discharge machining: machinability studies of hard materials (TiNi shape memory alloys, Si3N4–TiN ceramic composite, ZrB2-based ceramics reinforced with SiC fibers and whiskers, tungsten-cemented carbide, Ti-6Al-4V alloy, duplex stainless steel, and cubic boron nitride), process optimization adopting different dielectrics or electrodes, characterization of mechanical performance of processed surface, process analysis, and optimization via discharge pulse-type discrimination, hybrid processes, fabrication of molds for inflatable soft microactuators, and implementation of low-cost desktop micro-EDM system