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

Selective laser sintering (SLS) is a manufacturing technology whereby parts are built through layerwise application and selective consolidation of a polymer powder by a laser. With this additive manufacturing technology, polymer parts can be built with nearly no limits to complexity and nearly without geometrical constraints. Recently, a handful of polypropylene (PP) materials has been added to the rather limited portfolio of laser sintering powders. In conventional extrusion, the use of nucleating agents to increase clarity and impact resistance of PP is widespread. The current investigation focusses on the use of a nucleating agent in the SLS process to improve the mechanical properties of PP parts. Using a nucleating agent is not without challenges. It must be assured that addition of the agent does not change the thermal properties of the polymer in such a way, that the requirements of the SLS process cannot be met. On the other hand, it must be assured that the nucleating agent becomes effective, eve...

Nucleation and Impact Modification of Polypropylene Laser Sintered Parts

Face-gear drive: Assessment of load sharing, transmission characteristics and root stress based on a quasi-static analysis

This paper presents a parametric Model Order Reduction (MOR) method for weakly coupled thermo-mechanical Finite Element (FE) models of machine tools and other similar mechatronic systems. This work proposes a reduction method, Krylov Modal Subspace (KMS), and a theoretical bound of the reduction error. The developed method addresses the parametric dependency of the convective boundary conditions using the concept of system bilinearization. Additionally, this paper investigates the coupling between the reduced-order thermal system and the mechanical response. A numerical example shows that the reduced-order model captures the response of the original system in the frequency range of interest.

Model order reduction of thermo-mechanical models with parametric convective boundary conditions: focus on machine tool

Analysis of the highest temperature in the machining processes, namely the flash temperature, helps to understand the physics of the process, to improve cutting tool geometry, and to achieve high performance machining. In the present work, the interaction between cutting grain and workpiece material in grinding process is analyzed. Single diamonds are considered for machining, which operates in comparison to other measurements in the range of grinding speed. The highest temperature in the grain-material interaction and cutting forces are measured. In order to measure the flash temperature, an innovative method to measure and analyze the temperature through the diamond grain in the cutting zone by a two-color pyrometer is proposed. Furthermore, cutting forces are measured simultaneously. In order to measure the temperature in the cutting zone, an accurate connection between diamond and pyrometer fiber is required. Thus, the diamond tool holders are manufactured by electrical discharge machining (EDM) milling in deionized water. A 0.5-mm-diameter hole is drilled in each holder to connect the diamond precisely to the pyrometer fiber. Machining processes are performed with 30 {\mu}m depth of cut, cutting length of 20 mm, and cutting speed of 65 m/s on Ti6Al4V. The cutting tool is fixed, and the shape of the rotating workpiece is optimized. The diamond holder with the specific shape is designed and manufactured. Quasi-static, dynamic, modal, and harmonic response analyses are performed in order to reduce vibrations and chattering. The measured flash temperature is 1380 °C and cutting normal, tangential, and axial forces are measured.

Konrad Wegener

Papers

Nucleation and Impact Modification of Polypropylene Laser Sintered Parts

Face-gear drive: Assessment of load sharing, transmission characteristics and root stress based on a quasi-static analysis

Model order reduction of thermo-mechanical models with parametric convective boundary conditions: focus on machine tool

Flash Temperature and Force Measurements in Single Diamond Scratch Tests

A Kinematic Process Model and Investigation of Surface Roughness for High Efficiency Dry Grinding