Showing papers by "Naotake Mohri published in 1992"
TL;DR: In this article, a premixture of elemental powders of titanium and aluminum was supplied as a spray material for the direct fabrication of titanium aluminide matrixin situ composites by means of reactive low-pressure plasma spraying with a nitrogen and hydrogen mixed plasma gas.
Abstract: A premixture of elemental powders of titanium and aluminum was supplied as a spray material for the direct fabrication of titanium aluminide matrixin situ composites by means of reactive low-pressure plasma spraying with a nitrogen and hydrogen mixed plasma gas. The aluminum content varied from 10 to 63 wt.% in the premixtures. The matrix of sprayed layers consisted of three kinds of titanium aluminides—Ti3A1, TiAl, and TiAl3—which begin to form on a low-carbon steel substrate immediately after deposition. The formation of nitrides, which act as a reinforcement, occurs both during the flight of liquid droplets and on the substrate. The nitrogen content is approximately 4 to 5 wt.% in the sprayed intermetallic matrix composites, regardless of the aluminum content of the premixtures. The kinds of titanium aluminides andin situ nitrides developed depend on the aluminum content of the premixtures. The homogeneity of the distribution of aluminum and titanium in sprayed intermetallic matrix composites has been improved by vacuum annealing. The predominant TiAl phase that formed in the sprayed intermetallic matrix composites with a Ti-36 wt.% AI premixture increases in quantity through annealing. Although some minor nitrides disappear through annealing, the principal reinforcement, Ti2AlN, does not decompose, but increases in quantity. The hardness of sprayed intermetallic matrix composites varies with aluminum content of the premixtures, but is always greater than that of sprayed titanium aluminides containing no nitrides. Annealing does not reduce the hardness of sprayed intermetallic matrix composites. Sprayed and annealed intermetallic matrix composites with a Ti-36 wt.% Al premixture maintain their hardness of approximately 500 HV up to 800 K. Hence, reactive low-pressure plasma spraying offers a promising fabrication method for titanium aluminide matrixin situ composites, which are expected to excel in wear resistance applications at elevated temperatures.
22 citations
TL;DR: In this article, the authors discuss the effects of different types of equipment on the performance of a 5.5GHz frequency band and show that φ0.1～0.5mm is the strongest band.
Abstract: 積層型PZTを組み合わせることにより, 電極を直接駆動することの可能な新しいメカニズムの細穴用放電加工装置を試作した.本試作機により, 以下の性能を確認した.(1) 加工装置主軸の慣性質量軽減により, 電極の応答が市販の細穴用放電加工機に比べて数十倍向上した.(2) 貫通穴加工では, 通常穴抜け際で加工が不安定になり加工速度が減少するが, 本試作機によるステップ周波数5kHzの加工ではその現象がほとんど見られない.(3) 電極駆動方式をステップ, アナログ複合によるハイブリッド方式とした場合は, ステップ定方式と比較して加工速度が速く穴抜け際の加工時間が短縮される.(4) 本装置は, φ0.1～0.5mmの電極に対し, 実用上十分な加工速度が得られる.
10 citations
TL;DR: In this article, a simple but practical law of removal rate related with thermal properties of work piece is found, where the removal rate is almost determined by the product of thermal conductivity and melting temperature.
Abstract: There have been many studies on the mechanism of electrical discharge machining. However, the general principle of the machining has not been found yet because of its complex machining phenomena. This study aims to find a simple but practical law of removal rate related with thermal properties of work piece. The removal rate is almost determined by the product of thermal conductivity and melting temperature. And the effect of carbon layer which covers copper electrode on the wear of the electrode is discussed through the experiments with several kinds of materials of work pieces. The materials of work pieces are classified into two groups according to the wear rate of copper electrode.
6 citations
TL;DR: In this article, a new process for finish machining on free-form surfaces is proposed, which consists of generating CL data, milling an electrode and a work by a machining center, removing cusps of the electrode and the work by electrical discharge machining (EDM) and finish EDM for the work.
Abstract: In this paper, a new process for finish machining on free-form surfaces is proposed. This process consists of generating CL data, milling an electrode and a work by a machining center, removing cusps of the electrode and the work by electrical discharge machining (EDM) and finish EDM for the work. In the cusp removing process, EDM with planetary motion under high wear conditions is carried out. Powder suspended working fluid is used in finish EDM in order to break through the roughness limit. Since the planetary motion in EDM process decreases geometrical accuracy, the electrode shape is manufactured to compensate its planetary motion. A geometrical tracing method generates tool paths for the work and the electrode without any cutter interference. A shape with mirror-like free-form surfaces has been realized through a series of automatic processes without sacrifice of geometrical accuracy and without any manual works.
2 citations
24 Jun 1992
TL;DR: Applying the method to finish electrical discharge machining (EDM) with planetary motion in powder suspended fluid, accurate mirror-like surfaces of a product or a die have been obtained without manual cusp removal works.
Abstract: This paper proposes a new method for tool path generation The method calculates tool paths efficiently and accurately by geometrically tracing or integrating a differential equation for intersection between offset surfaces of a product and constraining planes of a tool It can avoid cutter interference with a product for a surface part having a smaller curvature radius than a cutter radius as well as a concave part for several surfaces and a convex edge The tool path keeps an outer part of the object by finding an inflection curve which divides convex and concave surface parts Applying the method to finish electrical discharge machining (EDM) with planetary motion in powder suspended fluid, accurate mirror-like surfaces of a product or a die have been obtained without manual cusp removal works
1 citations