Table of Content

31 March 1987, Volume 8 Issue 1

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Paper

On the Positive-Negative Sequence Modification Method of Automatic Partitioning Blocks in Elasto-Plastic Finite Element Analysis

Chang Liangming、Wang Xucheng

1987, 8(1):  1-7.  doi:10.3969/j.issn.1000-1093.1987.01.001

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In this paper is proposed an algorithm suitable for elasto-plastic finite element analysis the positive-negative sequence modification method of automatic partitioning blocks. In general cases，this algorithm avoids the necessity of reformation and factorization of coefficients in elastic region of the stiffness matrix completely，and is not restricted by the immediate access storage of the computer，based on automatic partitioning blocks. It may also ba efficiently applied to the local re-analyses of structures such as in contact problems， optimum design etc. In the paper are described the principle involved, chief steps in implementation and the program flow charts of this algorithm.

Similitude Method in the Interior Ballistics of Ejectors

Yuan Zengfeng

1987, 8(1):  8-18.  doi:10.3969/j.issn.1000-1093.1987.01.002

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Similitude method is tentatively applied for ejectors with gas or gas vapor mixture as the power source (including ejectors belonging to the parallel or series recoillesstype, self-ejecting type and gas/vapor mixture). Criteria of similitude for high-and low-pressure chambers are derived. Taking N pieces of tubular propellant as an example，the conditions to be followed for model testing are derived. Models designed following these conditions be used to predict interior ballistics characteristics of the ejecting system prototype. The P1—t,P2 — t，υ一t characteristics of the model coincide well with those from actual tests on the prototype.

On the Mechanism of Thermal Decomposition of N，Nˊ-Dinitrom-e thylenediamine

Jiang Delin、Liu Ziru、Wu Chengyun

1987, 8(1):  19-29.  doi:10.3969/j.issn.1000-1093.1987.01.003

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The thermal decomposition of N，Nˊ-dinitromethylenediamine is studied experimentally. The phase relationships between HOMO and LUMO in possible concerted processes are studied with the frontier orbital theory. The process of B-membered cyclic concerted fragmentation is calculated with the CNDO/Ⅱ method. The results of theoretical calculation are in agreement with the experimental results. These results show that the mechanism of the decomposition is basically the concerted process of the 6-membered cyclic fragmentation,

Some Remarks on the Interim Layer in Coherent Fiber Elements

Qin Bingkun、Sun Yunan

1987, 8(1):  30-36.  doi:10.3969/j.issn.1000-1093.1987.01.004

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The index profile of the interim layer between the core and the cladding in coherent fiber elements made up of multi-component glass is derived, taking the viewpoint of ion exckange. It is suggested that tlie interim layer influences the quality of the coherent fiber element and it is considered that the depth of this layer depends mainly on the core diameter， the cladding thickness, the difference in consistency of exchangeable ions between the core and the cladding，the coefficient of diffusion and the time of ion exchange. Besides，when this layer is comparatively thin， the fiber NA decreases, while the crosstalk effect incresses slightly. Also，if the graded fiber is to be made by ion exchange between the core and the cladding，the cladding thickness must remain larger than the core radius， and the index difference between the core and the cladding as well as the diffuse coefficient must be held sufficiently high.

Investigation of the Structure of Austenite in High Manganese Steel

Su Ronghao

1987, 8(1):  37-44.  doi:10.3969/j.issn.1000-1093.1987.01.005

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The structural characteristics of iron, manganese and carnon atoms are analysed and the atomic percentages of both manganese and carbon con- tent of an. austenitic manganese steel calculated. It seems that atomic groups of Fe2Mn2C characterized by C-sp3 hybrid orbitals are orderly distributed in the austenitic lattice, Electron diffraction study of thin specimens shows that these atomic groups are distributed along the<110) and〈lll〉 directions. It is very likely that there exists two types of arrangements， one being densely packed and the other loosely. Two structural models are proposed and the saturation values of carbon and manganese calculated. It is believed that the strength of high manganese steel could be substantially increased by appropriate increase of carbon and manganese contents in the steel.

On the Calculation of Stress Intensity Factors Using the Finite Element Method

Zhao Xueren

1987, 8(1):  45-49.  doi:10.3969/j.issn.1000-1093.1987.01.006

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An approach based on the superposition of normal finite element on singular terms for the calculation of stress intensity factors is proposed and the work done by prof.Chien Wei-Chang & others is extended in this paper .This approach can be used to calculate the stress intensity factors for mode I and mode Ⅱ as well as for the mixed mode.

Extension of Roberson-Wittenburgˊs Equations to Impact Problems of Multi-Rigidbody Systems with Nonholonomic Constraints

Yuan Shijie

1987, 8(1):  50-57.  doi:10.3969/j.issn.1000-1093.1987.01.007

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R . E. Roberson and J. Wittenburg have studied the motions of multi-ri一 gidbody system haying tree structure with holonomic constraints and closed chain structure with linear nonholonomic constraints. They have developed the differential equations of general form for motions of such systems .However,they have not taken intoaccount nonlinear and nonholonomic constraints. As for impact problems, they have only studied multi-rigidbody systems with holonomic constraints,but have not showed any concern for the case with nonholonomic constraint, This paper intends to generalize Roberson-witten-burgˊs differential equations for continuous motion to mu- Itiri-qidbody systems with nonlinear nonholonomic constraints, and their conclusions with regard to holonomic multi-rigidbody systems in the study of impact problems to multi-rigidbody systems with nonholonomic constraints.

Research Notes

The Third Order Aberrations of an off-Axis Spherical Substrate Holographic Lens in Plane to Plane imaging And with an External Entrance Pupil

Sheng Erzhen、Duan Zhenguang、 Yu Zhengchen

1987, 8(1):  58-63.  doi:10.3969/j.issn.1000-1093.1987.01.008

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In this paper，the third order aberration formulas of a spherical substrate holographic lens, in plane to plane imaging and with an external pupil are derived. Conditions for eliminating the various kinds of aberrations in off-axis imaging position are analysed and discussed.

Relation Dynamic Calibration for Pressure Transducers

Xiao Feng

1987, 8(1):  64-68.  doi:10.3969/j.issn.1000-1093.1987.01.009

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The paper proposes a new method for the dynamic calibration of pre- ssure transducer sby means of a reference transducer, the transfer function method making use of two pressure measurement holes in a gun. Based on theoretical analyses and test results, it is seen that the method is feasible and practical in actual situations .It has obvious advantan- ges for pressure measurements of guns.