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

The demand of energy efficient machine tools has increased recently due to the awareness for energy efficient production in precision manufacturing. A portion of the energy supplied to machine tools is transferred to thermal losses which influence also the thermal behavior of the precision related machine tools components. Machine cooling and process cooling can prevent thermal machine tool errors. However this further requires considerable amounts of energy. Hence there is a demand to monitor the electric, thermal, fluidic and mechanical energy flows in the machine tool in order to optimize the machining process and by this increasing its energy efficiency. This study intents to propose a method which has the capability of real-time monitoring of the entire energetic flows in a CNC machine tool including motors, pumps and cooling fluid. The structure of this approach is based on categorizing the machine into subsystems and measurements of the consumers (pump, motors, …) power, temperature at the inlet and outlet of the pumps and current as well as the speed of the motors. The visualization is carried out by a 2D Sankey diagram, which makes it easy to understand the energetic flows in the machine tool. The methodology is verified by the rule of energy conversion which confirms the capability of this method on real-time energy monitoring of a machine tool.

A methodology for online visualization of the energy flow in a machine tool

Geometry Optimization of Polycrystalline Diamond Tools for the Milling of Sintered ZrO2

Model Based Prediction Approach for Internal Machine Tool Heat Sources on the Level of Subsystems

Thermo-mechanical finite element (FE) models predict the thermal behavior of machine tools and the associated mechanical deviations. However, one disadvantage is their high computational expense, linked to the evaluation of the large systems of differential equations. Therefore, projection-based model order reduction (MOR) methods are required in order to create efficient surrogate models. This paper presents a parametric MOR method for weakly coupled thermo-mechanical 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. The reduced-order model reproduces the thermal response of the original FE model in the frequency range of interest for any value of the parameters describing the convective boundary conditions. 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.

/pdf/model-order-reduction-of-thermo-mechanical-models-with-1w71qsmz4j.pdf

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

All objects, apart from black-bodies, reflect a part of the incident radiation. The reflected fraction of incident radiation is termed as „reflectivity‟. The reflectivity of surfaces is often a function of the wavelength, the material, the quality of the surface, and the incident angle of the radiation. In order to evaluate the specular reflectivity of a surface at small incident angles, a method, based on thermal radiation measurement by a thermo-camera, was developed. A quasi black-body, a so-called „Hohlraumstrahler‟, was realized and used as thermal radiation source. The temperature of the source was continuously monitored by temperature probes at 3 different locations inside the source, while the radiation flux of the source was measured by a thermo-camera. During a calibration process, the temperature data from the probes and the radiation flux measured by the thermo-camera were simultaneously recorded and evaluated. In a next step, the radiation from the source was reflected by the samples and measured by the thermo-camera along with the temperature data from the probes. Using the calibration data, the reflected radiation flux could be calculated. The surface profiles of the samples were also measured by a stylus instrument. The calculated reflectivities were evaluated together with the surface roughness of the samples. The results showed good coincidence with the theoretical model of Bennett and Porteus [1].

/pdf/evaluation-of-reflectivity-of-metal-parts-by-a-thermo-camera-4gomll3s9k.pdf

Konrad Wegener

Papers

A methodology for online visualization of the energy flow in a machine tool

Geometry Optimization of Polycrystalline Diamond Tools for the Milling of Sintered ZrO2

Model Based Prediction Approach for Internal Machine Tool Heat Sources on the Level of Subsystems

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

Evaluation of reflectivity of metal parts by a thermo-camera