Table of Content

31 December 1990, Volume 11 Issue 4

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Paper

X-Ray Detection of Phenomena in a Gun Barrel During the Firing Process

Zeng Simin、Huang Xinhua、Jin Zhiming、Jiao Huanan

1990, 11(4):  1-8.  doi:10.3969/j.issn.1000-1093.1990.04.001

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This paper presents a method for the X-ray detection of phenomena within a gun barrel，shows some photographs taken, revealing the combustion of propellant and motion of grains. The paper gives a comparison for the states of motion of the propellant beds with different ignition patterns (primer at bottom and central position) during tke firing cycle. It is seen that the burning propellant grains basically remain in the chamber. Propellant combustion within the barrel is analysed with the help of information provided by these photographs.

Application of Boundary Integral Equation Method in the Dynamic Fracture Strength Analysis of Parts for an Airborne Gun

Li Yuechuan、Zhaug Lihuan、Yang Yaochi

1990, 11(4):  9-15.  doi:10.3969/j.issn.1000-1093.1990.04.002

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In this paper，boundary integral equation method is used in the dynamic fracture strength analysis of a critical element in an airborne gun. In combination with experimental dynamic fracture data of the material used for that element，the critical range crack-length for stationary cracks of the element is obtained using the mixed-mode fracture criterion. Following this a suggestion is made to correct the crack-length limit for the renewal of the element.

On the Effects of Jets from the Fore-Located Nozzles on the Stability of a Rocket

Song Piji

1990, 11(4):  16-19.  doi:10.3969/j.issn.1000-1093.1990.04.003

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For a rocket provided with fore-located nozzles the system of forces acting on it during the burning stage is analyzed. It is demonstrated that， during supersonic flight there exists a localized area of high pressure on the body surface of the rocket near the fore-located nozzles, forming an overturning moment. This explains the probability of occurance of instability of the rocket in supersonic flight during the burning stage.

The Flight-Determination Method for the Drag Coefficients of Projectiles

Yang Zhiyuan、Qin Yingxiao

1990, 11(4):  20-27.  doi:10.3969/j.issn.1000-1093.1990.04.004

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Practical flight—determination methods for the drag coefficients of projectiles are systematically studied in this paper and its applications analyzed. The methods presently in use are studied first, from the formulas used to the further generalized cases. Connections between the various methods and their mathematical essentials are explicated and the existing problems and their errors，as well as the points to be noticed in designing their measurement schemes are enumerated. A new approach, the Spline Function Method，is then put forward. The method is capable of giving continuous and smooth curves, assuring a high precision.

Modelling and Prediction of the Combustion Process of DB Solid Propellants

Zhao Zhijian、 Zhao Baochang 、Lu Anfang

1990, 11(4):  28-38.  doi:10.3969/j.issn.1000-1093.1990.04.005

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A Study of the Motion State Models for Runaway Escapements

Deng Jiahao、Wang Baoxing

1990, 11(4):  39-45.  doi:10.3969/j.issn.1000-1093.1990.04.006

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The runaway escapements possessing flat coupled surface and arcuate top is studied. Rules governing the angular velocity ratio and moment ratio of the escapement is discussed first. A unified mathematical model on coupled motion is set up and the equivalant moment and moment of inertia of the gear train in front of the escapement wheel is then derived. Problems such as the critical point from coupled motion to free motion and the free rotary motion etc. are also analyzed, thus giving more elaborations to the mathematical model.

Fiducial Limits and Bayesian Limits of Binomial Environmental Factors

Zhou Yuanquan、Weng Zhaoxi

1990, 11(4):  46-52.  doi:10.3969/j.issn.1000-1093.1990.04.007

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In this paper， a definition of go-no-go type environmental factor is given. The exact Fiducial limits and Bayesian limits of binomial environmental factors are derived. Approximate limits giving desired precision and convenient for calculation are presented to meet practical engineering needs. These approaches are illustrated with numerical examples.

The Adiabatic Shear in Metals

Chen Weizhong、 Xu Zuyao

1990, 11(4):  53-59.  doi:10.3969/j.issn.1000-1093.1990.04.008

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The temperature distribution under shear with a Kigh strain rate and the cooling rate of the shear bands of Al，Cu and 0.06C steel have been calculated using a computer. The results show that the temperature of shear band increases with the increase of the average strain rate (Y0). When Y0 is in the range 8 X 105 to 106s-1the structure of the adiabatic shear band in a 0.06C steel is martensitic but it becomes metallic glass if Y0> = lO6s-1. As to Al and Cu, the structure of the adiabatic shear bands can also be one of metallic glass if V0 is greater than 1. 8 X 106 and 5. 5 X 107 s-1 respectively .It explains that Cu tends to be the most reluctant to form an adiabatic shear band， while 0.06C steel forms the band most readily among the three metals.

Suppression of Built-up-Edge in the Machining of Al-Si Alloy Applying Ultrasonic Vibration Cutting

Wang Lijiang、Sun Fengchi

1990, 11(4):  60-67.  doi:10.3969/j.issn.1000-1093.1990.04.009

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In this paper, it is proposed that formation of tlie- built- up—edge during the machining of cast Al~Si alloys can be suppressed by ultrasonic vibration cutting. Its effectiveness has been shown experimentally when in turning at middle or low speeds. On cutting with a lubricant the area without built-up-edge formation can be widened. Shape and size of the built-up-edge is studied through SEM analysis and various types of the built—up—edge are brought to light clearly. It is also found that the cutting speed coefficient Kv is an important parameter in effecting the heigkt of built-up-edge. Relevant mathematical model is established.

Comprehensive Reviews

Present Status and Prospects of Defense Applications of the Rare Earths

Jiang Fan、 Li Maoshan

1990, 11(4):  68-73.  doi:10.3969/j.issn.1000-1093.1990.04.010

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The paper gives in some detail the present status of military applications of the rare earths, both domestically and abroad， in such fields as metallic materials for weaponry, glass and ceramics for military use，and special purpose ammunitions. It attaches due impor- tance to a discussion on their prospective military applications in superconducting ceramics made of rare earths.

Experimental Techniques and Analysis

An Experimental Investigation of the Aerodynamic Properties of Rod- Nosed Projectiles——Aerodynamic Properties of the Projectile Body

Yue Benxiang

1990, 11(4):  74-82.  doi:10.3969/j.issn.1000-1093.1990.04.011

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In order to stress on the analysis of aerodynamic properties of the projectile body, the geometric contour of the rod-nose is first fixed. The projectile body under consideration is either an inverted truncated cone with a cylindrical portion or a cylindrical one. The experimental Mach number range from 1.53 to 4.0. The paper gives variations in the forebody drag，the normal force and the pressure center in accordance with the Mach numbers and the geometric parameters. It is shown from experimental data and flow field analysis, that the centrifugal force, which the airstream itself produces when flowing o— rer the blunt surface edge of the body，together with the vortex flow field on the body surface，lead to the fact that the body aerodynamic properties of rod-nosed projectile differ appreciably from those of the streamline-nosed projectiles.

Measurement of the Burning Properties of Solid Propellants Using Laser Servo-Controlled Strand Window Bomb

Yi Yunfeng、 Sang Bingcheng

1990, 11(4):  83-87.  doi:10.3969/j.issn.1000-1093.1990.04.012

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A method to measure the burning rate of solid propellant using laser servo-controlled strand window bomb is giyen. Burning rate coefficients and pressure indices of solid propellants are obtained by means of the least square method. The method to measure the burning rate coefficient and pressure index of a solid propellant with only one strand is discussed and analyzed，and the measured and processed results are given.

Research Notes

A Method of Automatic Scoring in Attacking Ground Targets by Aircraft Cannons

Li Wenying

1990, 11(4):  88-92.  doi:10.3969/j.issn.1000-1093.1990.04.013

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This paper introduces a method to position-fix: point of impact when shooting ground targets from aircraft cannons and a way to realize automatic scoring. The pick-up arrangement, mathematical model of impact-point positioning，medium for the transmission of. earthquake waves, and the general system block-diagram etc. are described. The chief contents as given in this paper hare been given experimental verification and achieved satisfactory results.