Search

In some space missions, the highest priority of the structural design is given to the geometry of the surface which has to be packaged and then deployed in space. Large space antennas and large solar cell arrays are such examples. It is interesting to note that basic geometric forms play a major role in conceiving novel concepts of these space structures. In this presentation, the author introduces two concepts of deployable space structures that are symbolized with groups of triangles and quadrangles, respectively.

この報告は,ゼータ補強板の研究の近況を報告するにある.まずゼータ補強板の剛性とそのメカニズムを説明し,これによりゼータ補強板の形状最適化の方向を示す.またこれによって設計をおこなったモデルの試案を示す.また一般に,この種の新しい構造モデルの自動化製作のために設備した数値制御モデル製作装置について説明する., The purpose of this paper is to report the recent developments of the study of the zeta-stiffened panel. First, the mechanism of stiffening by a doublly corrugated plate is explained in some details and then, the guiding principle of optimizing the zeta-stiffened panel. The automation of fabricating the structural model of compicated configuration, such as this panel, by use of the NC machine is also discussed in the paper., 資料番号: SA0125858000

資料番号: SA8000730000

The stress analysis of the PCCP shell, which is a kind of concave polyhedral shells, is presented. Both the numerical method (FEM) and the experimental method are used in the analysis. Resultantly, the elastic behaviour and stress distributions of the PCCP shell subjected to either axial compression or hydrostatic pressure are made clear. The higher buckling pressures of PCCP shells in comparison with that of the circular cylinder are obtained experimentally. Besides, it was found that the particular stress distribution observed in PCCP shells in axial compression gave a basis for Miura's hypothesis to explain the collapsing mechanism of general cylindrical shells., 資料番号: SA2401185000

Note: This is the preprint of the paper which will be presented at the 18th AEROSPACE MECHANISM SYMPOSIUM, May 2-4, 1984, Goddard Space Flight Center, NASA, 資料番号: SA8000643000

In the PART I of this paper, a new concept for the one-dimensional deployable truss structure is presented. The deployed configuration of the structure consists of the repetition of an octahedral truss module longitudinally, and thus it is exactly the so-called "geodesic beam" structure. The principal mechanical feature of the truss is that the lateral members comprising the lateral triangular truss are telescoping beams. Contracting of the lateral members results in the deployment of the truss structure. The geometric transformation of this truss of variable geometry is presented. It is shown that both simultaneous and sequential modes of transformation are possible. The validity of the transformation applied to the deployment is verified through design of a conceptual model. In the PART II of the paper, a preview is presented as for the applications of the concept to a curvilinear truss and a space manipulator arm., 資料番号: SA0034982000

The purpose of this paper is to present a new concept of packaging and deployment of large membranes in space. The problem of biaxially folding of a plane is transferred to the elastic problem of a biaxially compressed infinite plate. After solving the problem, the plate thickness is reduced infinitesimally small, and thus the result represents the isometric transfer of an infinite plane subject to biaxial shortening. As a result, the concave polyhedral surface is discovered, which is composed of a repetition of a fundamental region, which is further composed of four congruent parallelograms. It is shown that the packaging and deployment by this surface geometry satisfies various requirements as to operations in space., 資料番号: SA0035000000

The flutter phenomenon of a balloon membrane placed in a flow is examined on the basis of linearized theory. The stability criterion or the flutter velocity is determined explicitly as a simple function of the velocity of transverse waves traveling in the membrane and the velocity of pseudo-capillary-waves traveling in the common surface between the air and the vacuum. The formulation parallels that of Kelvin for the generation of water waves by wind, but effects of the mass of membrane and the internal gas require some modifications similar to such method for the self-excited motion of thin panels in compressible flow as J. W. Miles'. It is found that the flutter may probably be one of the reasons for balloon fracture when it takes a flight mission experiencing high velocity at very high altitude., 資料番号: SA4135040000

グラファイトは固体ロケットモータのノズルとして使用されるが,その耐熱特性の改善のためにシリコーンオイルをグラファイトの試験片に真空槽で含浸させ,酸素-アセチレンバーナで試験片に吹付け,裏面温度を測定しその効果を検討したものである.浸透されたシリコーンオイルは加熱によってアブレーション効果でグラファイトの浸蝕と,内部への熱伝達を弱める.シリコーンオイルの含浸量は10～15%程度のわずかな量に対しても,試験片の温度上昇は含浸させないものに比較して約50～60%くらい低く,その効果が非常に大きい., Graphite is commonly used for the nozzle of rocket motors. To improve the heat-resisting characteristic of graphite, silicone oil is penetrayed into the graphite specimen in a vacuum vessel. As a basic test hot gas was blown by the torch burner on the face of the specimen and the temperature change on the back was measured. The heat-resisting characteristic of graphite is mainly due to its ablation effect. When silicone oil is penetrated graphite, the ablation effect increases remarkably, though the increase of weight is slight., 資料番号: SA4135103000

Thermal buckling of the plate simply supported by the web is analysed when the system is subjected to an arbitrary symmetrical temperature distribution over the plate surface. The buckling criterion is established and, furthermore, a simple formula for buckling criterion is obtained with reasonable accuracy for engineering purposes. Special attention is paid in exactly satisfying the boundary conditions, and the solution thus obtained is compared with those of Hayashi, Klosner and Forray, who have treated it approximately. It is found that their solutions for buckling criterion are appreciably larger than the value in the present analysis and, either decrease in the stiffness of webs or increase in the non-uniformity of temperature can result in a much larger descrepancy wiht more accurate value., 資料番号: SA2404833000

This paper presents an experimental evidence that the discontinuity of buckle pattern tessellation exists in the elastic postbuckling configuration of cylindrical shells of variable curvature. This raises the question on the validity of some assumptions generally prevail in analytical studies about the problem., 資料番号: SA2400797000

This paper presents an approximate analysis of torsional rigidity and of torsional vibration of aerodynamically heated wings having a small amount or pretwist. The combined effects of pretwist and thermal stress on the torsional rigidity are made clear and are shown to be considerably large even if the amount of pretwist is small. As for the free vibration of pretwisted wing, the suthor shows that, regardless of whether the thermal stress is present of not, the vibration can be characterized by the following differential equation 〓+c_1χ+c_2χ^2+c_3χ^3=0,whose solution can be expressed by the Weierstrass's elliptic function. The third term of the left hand side of the equation shows the asymmetricity of vibration for such pretwisted wings., 資料番号: SA2404836000

A proposition of a new shell form, which is cylindrical in a macroscopic sense and is concave polyhedral in a microscopic sense, is the purpose of this paper. It is shown that the inextensional post-buckling configurations of general cylindrical shells subjected to axial loading have peculiar geometrical characteristics, and that these configurations compose a general group of surfaces which may be designated as the pseudocylindrical concave polyhedral surface. Then the fixed idea that these surfaces are essentially failed forms is abandoned and is replaced by the idea that these are the basic forms of a new shell which could function superbly as the structure under some loading conditions. It is shown that the new shell, which may be called for convenience, the pseudocylindrical concave polyhedral shell and the PCCP shell for its abbreviation, has many useful characteristics as follows; inclusion of an arbitrary curvature distribution, developability of its midsurface, intrinsically high circumferential bending rigidity, and simplicity of elementary faces. The application of PCCP shells to large span shell structures, reservoirs, expansion joints, and others is suggested., 資料番号: SA2400708000

固体表面が急激に加熱される場合,その初期において熱は表面から限られた深さしか拡散せず,いわゆる熱層が形成される.これは粘性流体における境界層と類似の概念で,T. R. Goodmanによって提案され,さらに運動量積分と類似の熱平衡積分と結びつけて熱伝導の近似解析に用いられる.本論文はまず熱層概念の理論的根拠を二つの面から示す.一つは境界層とのアナロジー,一つは粒子のBrown運動の確率過程で,共に数学的にFourierの方程式と等価なものである.次に熱層近似の方法の一般的操作を提示し,厚板,円筒,遮熱被膜等の解を得る.次に熱弾性問題の領域における熱層近似の方法の応用性を検討した結果その有用性が認められるので,熱応力,熱衝撃,熱変形及び急速加熱による振動等の問題が解析される.この方法の容易さ,そして解の明白で物理的直観に沿っている点は,熱伝導,熱弾性問題における広い応用性を暗示するものである., When the surface of a solid is exposed to a heat input, an increase in internal energy must, in the early stages, be restricted within a short distance δ(τ) from the surface. A quantity δ(τ) is defined to be the thermal layer, which is analogous to the boundary layer in a viscous flow. The concept, proposed by T. R. Goodman, is conveniently used for the approximate analysis of heat conduction problems in connection with his Heat-Balance Integral analogous to the Momentum Integral. This paper presents the theoretical foundation for the concept of the thermal layer, first by its analogy to the boundary layer, and secondly by describing the heat conduction process as the stochastic process of the Brownian motion of the particles, the process is mathematically equivalent to the Fourier's law of heat conduction. Then the general method of thermal layer approximation is presented, and is used for the analysis of heat conduction problems of a slab, a cylinder and a insulation coating. These solution is then used for the analysis of thermo-elastic problems such as thermal stresses, thermal shock, thermally induced vibration and deflection problems. Easiness of the analysis together with an explicit character of the solution suggest the wide applicability of the method in these field., 資料番号: SA4135032000

軸対称底面を有する物体の着水時の衝撃荷重についての解析ならびに実験結果を報告する.解析の特徴は着水後に発生する最大加速度をclosed formの形で得たことであり,着水後の加速度特性も簡単に計算することができる.実験は球状ならびに円錐状底面を有する試験体を使って行なった.この実験は解析に対応しての系統的なものであり,実験値と解析結果とはよく一致した., Analytical and experimental studies have been made to determine the impact accelerations of axially symmetric bodies during landing on water surface. The formulas for the maximum impact accelerations are derived and the history of the acceleration can be calculated easily by the present analytical results. Spherical and conical models were used for the present experiments. The water impact accelerations of these models were measured by accelerometers. The agreements between the experimental and the theoretical results are satisfactory., 資料番号: SA0125367000

A new form of sandwich core of high strength created by a topological transformation of a single plane is proposed herein. The resultant core is to be manufactured from a single sheet through a plastic forming. The purpose of this proposition is to present a sandwich core which has following principal characteristics; simplicity of form, applicability to both flat and curved sandwiches, possibility of circulating fluid between facings, the easiness of manufacture, the adaptability to large as well as small scale core, and the isotropy or controllable orthotropy of shear modulus. This core, designated as zeta-core by this author, is a sophisticated shell structure whose mid-surface is characterized by a doubly corrugated surface combining a couple of facings. An elementary analysis proves that the directional mean of shear modulus of zeta-core can compete with that of honeycomb core of identical apparent density, and that it is possible to design zeta-core of any orthotropy including, of course, isotropy in shear modulus. As for the realization aspect, no essential difficulty was encountered in trial manufacture of zeta-core from aluminum, plastics, and G.R.P. sheet materials. Furthermore, it can be predicted that the cost of production of zeta-core is relatively low in comparison with honeycomb core. It seems probable that the introduction of zeta-core of high shear modulus which can be made of various engineering materials will open up fresh possibilities for structural sandwich construction., 資料番号: SA2400861000