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

Welding of precipitation-hardenable nickel-based super alloys that contain large amounts of Al and Ti is challenging due to their high susceptibility to hot cracking. For metal additive manufacturing (AM) by powder bed fusion (PBF) or direct metal deposition (DMD), various welding process adjustments may prevent the formation of cracks. The aim of this study is the development and experimental characterization of a laser preheating process for DMD of Inconel 738LC. Metallographic cross-sections of multiple test specimens were analyzed to quantify the effect of initial substrate temperature, specimen geometry, deposition parameters, and scanning strategy on the resulting crack density. The results show that increased substrate temperature by laser preheating and reduced specimen size leads to crack-free deposited structures. Therefore, the proposed preheating process may be applied for part fabrication or repair by DMD to reduce or even completely prevent the risk of hot cracking.

/pdf/laser-preheating-for-hot-crack-reduction-in-direct-metal-2iw4piqb.pdf

Laser Preheating for Hot Crack Reduction in Direct Metal Deposition of Inconel 738LC

A technique for structuring the surface of a bulk metallic glass (BMG) via scanning with a beam of laser pulses in the pico- and femtosecond time regime is presented. Specimens were characterized by various techniques to analyze the effects of ultrashort laser pulses on the amorphous matrix. Broadly varying surface structures, with roughness parameters in the range of R a = 0:066 to 0:329 μm, measured using white light interferometry (WIM) and optical 3D microscopy, were produced. These techniques could be useful for fabricating biomedical implants from BMGs. As proof of principle, a patterned grid, designed for evaluating bone cell response to different surface structures, are produced.

/pdf/surface-structuring-of-zirconium-based-bulk-metallic-glasses-cp6zusrfps.pdf

Surface structuring of zirconium-based bulk metallic glasses using ultrashort laser pulses

The application of both pure and abrasive waterjets is well established in manufacturing and related processes like surface preparation. Particle free surface processing in order to avoid any particle residuals on the machined workpiece surfaces was addressed as core requirement by quality engineers who had to fight against induced failure of functionalized surfaces after surface preparation by e.g. sand blasting.

Measurement of the Effective Waterjet Diameter by Means of Force Signals

Bioinspired intelligent SLM cell

A novel conditioning routine of metallic bonded diamond grinding worms is reported. The competitive manufacturing time is realized by a combination of orthogonal and quasi-tangential laser processes. The introduced quasi-tangential process is only limited by the maximum available laser power of 100W at 10 ps and 800 kHz for roughing. Hence, a maximal ablation rate of 55mm3 min-1 is reported and the accumulated ablation rate for conditioning is 3mm3 min-1. Following, the manufacturing of grinding tools within a maximal geometric deviation of 40 μm is shown. The threaded tool is finished by a laser sharpening process exposing the bonded diamonds on the surface for increased cutting characteristics. Thermally induced phase transitions are assessed via Raman spectroscopy and reveal a negligible heat-affected zone.

Konrad Wegener

Papers

Laser Preheating for Hot Crack Reduction in Direct Metal Deposition of Inconel 738LC

Surface structuring of zirconium-based bulk metallic glasses using ultrashort laser pulses

Measurement of the Effective Waterjet Diameter by Means of Force Signals

Bioinspired intelligent SLM cell

Ultrashort pulsed high-power laser conditioning of super-abrasive grinding worms