SUMMARYNumerical analysis with the Boundary Element Method (BEM) has been used more and more in various engineering fields in recent years. In numerical techniques, however, there are some problems which have not been fully solved even now. The most essential one is the drop in the accuracy of results for internal points near the boundary of the structure, where the singularity of integrands in the boundary integral equation is too strong to be evaluated with the normal numerical method. For the boundary integral equation of stress, this problem became more serious, and the accuracy can be improved only partly, even though very refined boundary elements are used.In this paper, the boundary integral equation is newly formulated using a relative quantity of displacement. In this way, the singularity of boundary integrals is reduced by the order of l/r, and the accuracy of solution is improved significantly. Furthermore, in order to integrate it more accurately, two kinds of numerical integral methods are newly developed. By using these methods, both displacement and stress can be obtained with excellent accuracy at almost any point in the structure without any numerical difficulty, although the discretization may be comparatively coarse. The generality and practicability of the present formulation and integral methods are confirmed through some examples of three dimensional elastic problems.
Advanced material and processing technologies of polyimide applied to various substrates were investigated and studied for high density electronic devices. Precisely controlled temperature profiles in each processing step can realize required chemical structures of polyimide materials and the excellent polyimide films. Thick film patterning of photosensitive polyimide is extremely difficult because the exposed top layer is dissolved before the unexposed area is developed as the result of UV absorption and reaction at the bottom being less than that at the top layer. For removing the thin film residue on copper and/or copper containing alloys, a simple patterning process using a solution containing hydrazine has been developed. Newly developed techniques such as screen printing, shower developing, and microwave-assisted curing enable the realization of more precise patterning of photosensitive polyimide. As an excellent pattern of polyimide films was obtained, functional electronic devices such as hybrid IC's and contact type linear image sensors could be developed by applying these advanced technologies.Organic polymers have been used in the electronics industry because of their planarization ability, low process cost, etc. Notably polyimide (PI) materials have excellent characteristics such as a low dielectric constant, thermal stability, chemical inertness, and low metallic ion content. PI films can be precisely etched both by wet processes with organic amines and by dry processes with 02 plasma.Therefore, PI materials have been widely and increasingly used for various electronic devices. For IC/LSI, thin film magnetic heads, and thermal printing heads, PI materials have been used as a multilevel insulator and protective layer. For printed wiring boards, PI has been used as a substrate material, for example, for polyimide glass multilayer boards and flexible printed circuit boards. In liquid crystal display, PI has been used as an alignment layer and the binder of ink materials for color filters.Published studies have discussed the patterning processes and the application methods with nonphotosensitive PI materials (1-3). Although many techniques have been attempted, there have been only a few reports with photosensitive PI materials. By using photosensitive materials (4-5) such as Pyralin PD (E.I. du Pont de Nemours and Company, U. S. A.), PAL (Hitachi Chemicals, Japan), Photoneece (Toray Industries, Japan) (5), Probimide (Chiba-Geigy, U.S.A.), and Selectilux (Merck, Germany) which have recently been released on the market, the PI patterning process can be made shorter and more efficient than the conventional photoetching proeess. For multilayer packaging, a PI film thickness of l0 ~m or more is needed and is quite different from that which is used for fabrication of multilevel devices such as IC and LSI.The purpose of this paper is to present a comprehensive study of advanced and unique techniques of PI for electronic devices such as the hybrid IC and the contact type linear image sensor. This investigation i...
Low-cycle creep-fatigue tests of the dissimilar metal electron beam welded joint between A387 Gr. 22 steel and SUS 405 steel were carried out under the strain-controlled cycling over the welded joint at 873K. It was shown that the creep-fatigue life of the dissimilar metal welded joint was significantly shorter than those of the base metals. This resulted from the strain concentration on the SUS 405 side with lower deformation resistance. It was also found that the hardness distribution was one of the important measures which reflect the strain distribution. Furthermore, the predicting method of creep-fatigue life for dissimilar metal welded joints was proposed by applying the strain range partitioning approach. The predicted lives were in good agreement with the experimental results.
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