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

Additive manufacturing of metallic components – Process, structure and properties

A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

This chapter discusses leading problems linked to energy that the world is now confronting and to propose some ideas concerning possible solutions. Oil deserves special attention among all energy sources. Since the beginning of 1981, it has merely been continuing and enhancing the downward movement in consumption and prices caused by excessive rises, especially for light crudes such as those from Africa, and the slowing down of worldwide economic growth. Densely-populated oil-producing countries need to produce to live, to pay for their food and their equipment. If the economic growth of the industrialized countries were to be 4%, even if investment in the rational use of energy were pushed to the limit and the development of nonpetroleum energy sources were also pursued actively, it would be extremely difficult to prevent a sharp rise in prices. It is evident that it is absolutely necessary to pursue actively the development of coal, natural gas, and nuclear power if a physical shortage of energy is not to block economic growth.

World energy outlook

Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting....

Polymers for 3D Printing and Customized Additive Manufacturing

Process Impact of Elliptic Smoothness and Powder Shape Factors on Additive Manufacturing with Laser Sintering

Konditionieren von Schleifscheiben mit Licht und Strom

Powder bed fusion of metals (PBF-LB/M) is the most commonly used additive manufacturing process for the layerwise production of metal parts. Although the technology has developed rapidly in recent years, manufactured parts still lack consistent quality primarily owing to process-inherent variability, and the lack of effective sensing technologies enabling the ability to control the process during part production. Thus, there are high costs caused by rigorous post-process part inspection steps required to provide compliant part certificates. In contrast to typically deployed in-situ sensing technologies, eddy current testing (ECT) is a standardized nondestructive testing (NDT) technique able to provide compliant part certificates during post-process inspection according to existing standards. This study investigates the potential of ECT as an in-situ process monitoring technology for PBF-LB/M. Parts made from AlSi10Mg were manufactured on a PBF-LB/M machine using different process parameters yielding different relative densities ranging from 99%– 99.7%. During the build cycle, the parts were measured layer-by-layer with an ECT system mounted on the machine recoater. Signal analysis methods were developed which effectively separate and calibrate the electrical conductivity component (relative electrical conductivity) and the distance component (lift-off) of the ECT signals. The relative electrical conductivity was then compared to X-ray micro-computed tomography ( μ CT) measurement data demonstrating that layer-to-layer differences in relative density of about 0.1% can be successfully detected via ECT. In addition, the lift-off was used to monitor the thickness of the consolidated layers and the layer-to-layer part height. The results show that ECT is an effective technology for in-situ monitoring of the relative part density paving the way for deploying ECT for in-situ NDT of PBF-LB/M-manufactured parts. 

In-situ monitoring of powder bed fusion of metals using eddy current testing

Im Zuge der „Industrie 4.0"-Initiative sollen digitale und reale Welten ein cyberphysisches Produkt (oder auch eine cyberphysische Produktion) bilden, in das ebenfalls der Mensch integriert werden soll. Insbesondere bei der Integration des Menschen in eine virtuelle Welt bestehen aber noch erhebliche Probleme im Hinblick auf die Mensch-Maschine-Schnittstelle, die derzeit einen Einsatz in einem produktiven Umfeld verhindern. Dieser Beitrag zeigt die bestehenden Probleme auf sowie neue Ansätze in der Forschung, die Interaktion des Menschen mit der digitalen Welt natürlicher zu gestalten.

Die Mensch-Maschine-Schnittstelle als Schlüsselelement für VR/AR-Anwendungen

A modular computational framework is presented for the identification of friction parameters in metal machining applications. Numerical simulation of such processes using mesh-based techniques (usually) necessitates the cumbersome re-meshing procedures and is hard to parallelize. Therefore, the present framework synthesizes the advantages of mesh-free methods with GPU parallel computing, offering an efficient tool for the optimization procedures in thermo-mechanical modeling of cutting problems. The proposed approach employs an inverse method to determine the unknown coefficients of a temperature-dependent friction model in high-speed metal cutting. Good agreement between our numerical results and experimental data is found, providing both quantitative and qualitative assessments.

/pdf/parameter-identification-of-a-friction-model-in-metal-u17f8ia24w.pdf

Konrad Wegener

Papers

Process Impact of Elliptic Smoothness and Powder Shape Factors on Additive Manufacturing with Laser Sintering

Konditionieren von Schleifscheiben mit Licht und Strom

In-situ monitoring of powder bed fusion of metals using eddy current testing

Die Mensch-Maschine-Schnittstelle als Schlüsselelement für VR/AR-Anwendungen

Parameter Identification of a Friction Model in Metal Cutting Simulations with GPU-Accelerated Meshfree Methods