There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Additive manufacturing of metallic components – Process, structure and properties

Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

Additive manufacturing of metals

The homogeneity of single crystals produced by additive manufacturing (AM) is much higher than that of single crystals produced by the standard investment casting process. Aim of this paper is to investigate the influence of this homogeneity on the formation kinetics of topologically closed packed (TCP) phases. CMSX-4 single crystals produced by selective electron beam melting and investment casting are homogenized and annealed at 870 °C and 1050 °C for up to 480 h. The formation kinetics of TCP phase formation is analyzed by electron microscopy.

Formation of topologically closed packed phases within CMSX-4 single crystals produced by additive manufacturing

In high-pressure die casting (HPDC) undercuts can only be fabricated by using complex high-maintenance sliders. Until now, this technology has not been used for large-scale and cost-sensitive serial applications. Sand cores from sand-and low-pressure die casting with organic and inorganic binder systems are not suitable for application in HPDC. Using lost cores made from sodium chloride may be a solution for HPDC. Due to the high dynamic forces during the casting process, core failure is still a problem, especially with high ingate velocities.

Core Viability Simulation for Salt Core Technology in High-Pressure Die Casting

Measuring procedures for surface evaluation of additively manufactured powder bed-based polymer and metal parts

Powder Bed Fusion with Laser Beam of Metals (PBF-LB/M) is one of the fastest growing technology branches. More and more metallic alloys are being qualified, but processing of aluminum wrought alloys without cracks and defects is still challenging. It has already been shown that small parts with low residual porosity can be produced. However, suffering from microscopic hot cracks, the fracture behavior has been rather brittle. In this paper different combinations of temperature gradients and solidification rates are used to achieve specific solidification conditions in order to influence the resulting microstructure, as well as internal stresses. By this approach it could be shown that EN AW-2024, an aluminum-copper wrought alloy, is processable via PBF-LB/M fully dense and crack-free with outstanding material properties, exceeding those reported for commonly manufactured EN AW-2024 after T4 heat treatment.

Grain Structure Evolution of Al-Cu Alloys in Powder Bed Fusion with Laser Beam for Excellent Mechanical Properties.

A complex fluid flow often involves passive scalars that are transported with the flow field but can be neglected regarding the fluid motion, such as concentration distributions, markers, or temperature fields. Using the Lattice Boltzmann (LB) method for fluid dynamic simulations, different approaches for coupling advection solvers to the fluid motion exist. The aim of this work is to give an overview of four different methods used for solving the advection equation. Two of these solvers are based on finite differences, namely the Lax–Wendroff method (Lax and Wendroff, 1960) and an extension from Succi et al. (1999) that artificially reduces numerical diffusion. The other two methods Onishi et al. (2005) and Osmanlic and Korner (2016) take advantage of the already available LB distribution functions, instead of depending on macroscopic quantities only. In the ansatz of Onishi et al. (2005) the local concentration flux is calculated from distribution functions directly, while in a similar approach used by Osmanlic and Korner (2016) an additional case distinction is made between incoming and outgoing flux. Besides investigating the order of accuracy and grid dependency, numerical diffusion is examined closely with the objective to simulate fluid flow that is solely determined by advection and contains no physical diffusion.

Carolin Körner

Papers

Formation of topologically closed packed phases within CMSX-4 single crystals produced by additive manufacturing

Core Viability Simulation for Salt Core Technology in High-Pressure Die Casting

Measuring procedures for surface evaluation of additively manufactured powder bed-based polymer and metal parts

Grain Structure Evolution of Al-Cu Alloys in Powder Bed Fusion with Laser Beam for Excellent Mechanical Properties.

Comparison of passive scalar transport models coupled with the Lattice Boltzmann method