Report on the current state of the French DMLs

This is a survey of the existing digital collections of French mathematical literature, run by non-profit organizations. This includes research monographs, serials, proceedings, Ph. D. theses, collected works, books and personal websites

Advances in metal additive manufacturing: A review of common processes, industrial applications, and current challenges

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. In recent years, Additive Manufacturing (AM), also called 3D printing, has been expanding into several industrial sectors due to the technology providing opportunities in terms of improved functionality, productivity, and competitiveness. While metal AM technologies have almost unlimited potential, and the range of applications has increased in recent years, industries have faced challenges in the adoption of these technologies and coping with a turbulent market. Despite the extensive work that has been completed on the properties of metal AM materials, there is still a need of a robust understanding of processes, challenges, application‐specific needs, and considerations associated with these technologies. Therefore, the goal of this study is to present a comprehen-sive review of the most common metal AM technologies, an exploration of metal AM advancements, and industrial applications for the different AM technologies across various industry sectors. This study also outlines current limitations and challenges, which prevent industries to fully benefit from the metal AM opportunities, including production volume, standards compliance, post processing, product quality, maintenance, and materials range. Overall, this paper provides a survey as the benchmark for future industrial applications and research and development projects, in order to assist industries in selecting a suitable AM technology for their application

Non-destructive testing of the parts manufactured by Direct Metal Laser Sintering

Published ThesisInterest in Additive Manufacturing (AM) has grown considerably in the past decades and industry has gained great benefits from this type of technology. The main advantages are: geometrical freedom that allows the design of parts with complex shape, which are difficult or impossible to produce by conventional technology; shortened design-to-product time; customization and the possibility to use several materials in one process. Direct Metal Laser Sintering (DMLS) is one of the most promising AM technologies that utilizes metal powders. Due to the layer-by-layer nature of powder delivery used in DMLS, the drawbacks are: surface quality and accuracy, high residual stress in as-built parts and porosity – all of which depend on the powder material, process-parameters, scanning and building strategies. This can result in a substantial deterioration of the mechanical properties of the products and their performance characteristics. For this reason, it is very important to identify defective parts before enrolling into service. Non-destructive testing (NDT) is effective for detection of internal defects without causing damage. NDT also covers a wide group of methods of analysis used to evaluate the properties of a material. NDT techniques like visual, acoustic, ultrasonic, thermal, X-ray and 3Dcomputed tomography (CT) inspections are now widely used for various industrial applications. For the analysis of material properties and the detection of defects, each of these methods uses different physical principles that have their advantages and disadvantages. In this study, some of the NDT techniques are evaluated in terms of their applicability to the inspection of parts manufactured by DMLS technology: Visual, Ultrasonic, Computed Tomography and Acoustic Emission inspection. Artificial defects were used to determine the feasibility of each NDT method. DMLS samples were produced containing a range of artificial defects. These samples were than subjected to each method and the results compared. A comparison between the amount of defect information obtained is made. It was shown that the nature of the sample; shape, size, material and the type of defects present plays a vital role in the selection of testing methods. Ultrasonic-Total Focus Method indicated that some defects are present upon testing relatively big samples with simple geometry. X-ray Computed Tomography showed some limitations with regard to the possibilities and the amount of defect detail, the only drawback being the cost and time involved. Acoustic Emission showed to be a promising method for production parts although it requires an initial time investment; thereafter it is a simple and easy way of detecting defective samples

Investigation of the high strain rate behaviour and impact toughness of Ti6Al4V (ELI) parts built by the EOS M280 DMLS System with standard process parameters : as-built and stress relieved

Thesis (Master of Engineering in Mechanical Engineering) -- Central University of Technology, Free State, 2018The high strain rate behaviour and the impact toughness of Direct Metal Laser Sintering (DMLS) produced Ti6Al4V (ELI) parts were investigated. The as-built (AB) specimens were also taken through stress-relieving heat treatment and are hereinafter referred to as SR samples or specimens. The high strain rate deformation of the two forms of the alloy (AB and SR) was studied using the Split Hopkinson Pressure Bar (SHPB) test, in compression and tension. Two high strain rates of 400 s-1 and 700 s-1 in compression and 250 s-1 and 360 s-1 in tension were used in these tests. The test results were used to investigate the relative strain rate dependence of flow stresses and fracture strain. Microstructural analysis was carried out to study the dominant fracture mechanisms on the deformed surfaces of the compression and tensile test samples using optical and scanning electron microscopy. Measurements of Vickers microhardness for the test samples were taken before and after the compression and tensile tests. The results of the high rate tensile and compression tests showed significant strain rate sensitivity in both compression and tension. Moreover, the rate sensitivity was seen to be relatively higher in the SR samples than in the AB samples. Microstructural analysis of the tested specimens showed that adiabatic shear bands dominated the deformed surfaces in the compression test samples. Multiple cracks that were more pronounced on the surfaces of the tested specimens were seen to initiate randomly on the deformed surfaces of the tensile test samples. The Vickers microhardness of the tested samples were observed to be higher for loaded specimens than for the unloaded specimens. The impact properties of the AB and SR DMLS Ti6Al4V (ELI) specimens were studied using an instrumented Charpy impact tester. The transition curves for the absorbed energy and lateral expansion were obtained by performing the experiments in the temperature range 130 ºC to 250 ºC. The effect of the orientation of the v-notch on the standard test specimen with relation to the base plate of the DMLS machine was investigated. Furthermore, the effects of stress-relieving heat treatment on the notch toughness of DMLS Ti6Al4V (ELI) specimens was also studied. The analysis of the fracture surfaces resulting from the tests at various temperatures was done using a scanning electron microscope (SEM). The values of absorbed energy and the lateral expansion of the specimens that were determined from this series of tests indicated that specimens built with the v-notch facing the base plate of the DMLS machine had better impact toughness and notch ductility in comparison to those built with the v-notch facing away from the base plate over most of the temperature range of testing. Besides improving toughness, stress-relieving heat treatment gave rise to a shift of the ductile-to-brittle transition temperatures (DBTT) to lower values. The study further established that the DMLS Ti6Al4V (ELI) retains appreciable notch toughness even at sub-zero temperatures

Digital Mathematics Libraries: The Good, the Bad, the Ugly

The idea of a World digital mathematics library (DML) has been around since the turn of the 21th century. We feel that it is time to make it a reality, starting in a modest way from successful bricks that have already been built, but with an ambitious goal in mind. After a brief historical overview of publishing mathematics, an estimate of the size and a characterisation of the bulk of documents to be included in the DML, we turn to proposing a model for a Reference Digital Mathematics Library--a network of institutions where the digital documents would be physically archived. This pattern based rather on the bottom-up strategy seems to be more practicable and consistent with the digital nature of the DML. After describing the model we summarise what can and should be done in order to accomplish the vision. The current state of some of the local libraries that could contribute to the global views are described with more details

Report of the Inter-American Tropical Tuna Commission for the year 2008

ENGLISH: The Inter-American Tropical Tuna Commission (IATTC) operates under the authority and direction of a convention originally entered into by Costa Rica and the United States. The convention, which came into force in 1950, is open to adherence by other governments whose nationals fish for tropical tunas and tuna-like species in the eastern Pacific Ocean (EPO). Under this provision Panama adhered in 1953, Ecuador in 1961, Mexico in 1964, Canada in 1968, Japan in 1970, France and Nicaragua in 1973, Vanuatu in 1990, Venezuela in 1992, El Salvador in 1997, Guatemala in 2000, Peru in 2002, Spain in 2003, the Republic of Korea in 2005, and Colombia in 2007. Canada withdrew from the IATTC in 1984. The IATTC's responsibilities are met with two programs, the Tuna-Billfish Program and the Tuna- Dolphin Program. SPANISH: La Comisión Interamericana del Atún Tropical (CIAT) funciona bajo la autoridad y dirección de una convención suscrita originalmente por Costa Rica y los Estados Unidos de América. La Convención, vigente desde 1950, está abierta a la afiliación de cualquier país cuyos ciudadanos pesquen atunes tropicales y especies afines en el Océano Pacífico oriental (OPO). Bajo esta estipulación, la República de Panamá se afilió en 1953, Ecuador en 1961, México en 1964, Canadá en 1968, Japón en 1970, Francia y Nicaragua en 1973, Vanuatu en 1990, Venezuela en 1992, El Salvador en 1997, Guatemala en 2000, Perú en 2002, España en 2003, la República de Corea en 2005, y Colombia en 2007. Canadá se retiró de la CIAT en 1984. La CIAT cumple su mandato mediante dos programas, el Programa Atún-Picudo y el Programa Atún-Delfín

DIRECT METAL LASER SINTERING OF TI-6AL-4V ALLOY: PROCESS-PROPERTY-GEOMETRY EMPIRICAL MODELING AND OPTIMIZATION

DIRECT METAL LASER SINTERING OF TI-6AL-4V ALLOY: PROCESS-PROPERTY-GEOMETRY EMPIRICAL MODELING AND OPTIMIZATIO

LLUSD Articulator - Volume 30, Number 2

Contents: 6 | Dean\u27s Circle member assemble at ESRI11 | PNAM celebrates tenth anniversary15 | From street life to restoration18 | Applications for 3D printing in dentistry25 | LLUSD research publications31 | Riverside\u27s fifth Long Night35 | Profiling Lee Ingersollhttps://scholarsrepository.llu.edu/articulator/1017/thumbnail.jp

3D printing and international security: risks and challenges of an emerging technology

"3D printing - or additive manufacturing - is a challenging dual-use technology: One and the same device can print toys or guns. The author explains the basics of the technology, describes its current applications, and provides an overview of its global diffusion. He shows the potential of this emerging technology and analyzes its possible risks with respect to the pro­lif­eration of small arms, major weapon systems, and even weapons of mass destruction. He investigates how 3D printing might pose serious challenges to national and international security. The author discusses first proposals of risk mitigation through safeguards, export controls, cyber security, awareness raising, and industry self-regulation." (author's abstract