Cause Analysis and Result Prediction of Thermal Dispersion for Typical Small Caliber Rifles

doi:10.12382/bgxb.2022.0776

Abstract

Abstract:

Thermal dispersion is an abnormal phenomenon of bullet dispersion after continuous firing of a small-caliber automatic rifle. It has an important influence on the shooting accuracy and combat effectiveness of the hot gun, but the formation mechanism of thermal disperison is not completely clear. Through the comparison experiment of hot and cold guns, it is found that, in the hot gun state, the barrel transfers heat to the copper bullet jacket, then the temperature of the jacket increases to soften the material, and the interaction between the bullet and the barrel greatly increases the deflection angle of bullet velocity and the swing angle of bullet axis, which is the main reason of thermal dispersion. A thermal dispersion analysis and calculation strategy for a typical small-caliber automatic rifle is proposed based on the thermal dispersion mechanism obtained from the experiment. Hot gun state barrel temperature field and stress field analysis model, bullet-barrel interaction thermos-mechanical coupling calculation model and random exterior ballistic and bullet dispersion calculation model are established by using the method of segmental modeling and parameter transfer, which realizes the quantitative analysis and calculation of the firing dispersion in hot gun state. The calculated results are basically consistent with the experimental results. The research in this paper provides an effective calculation method for the quantitative analysis of thermal dispersion problem of small-caliber automatic rifles.

Key words: automatic rifle, firing accuracy, thermal dispersion, calculation model, bullet-barrel interaction

CLC Number:

TJ012

DAI Cheng, CAO Yanfeng, HE Long, XU Cheng. Cause Analysis and Result Prediction of Thermal Dispersion for Typical Small Caliber Rifles[J]. Acta Armamentarii, 2024, 45(3): 885-892.

Figures/Tables 14

Fig.1 A small-caliber automatic rifle (upper) and high-speed camera(below)

Fig.2 Comparison of 100m bullet dispersion experimental results with cold and hot guns

Fig.3 Temperature variation of barrel surface at 240mm from bore bottom with bullet number

Table 1 Variation of yield strength of bullet jacket material at different temperatures[15]

枪管及弹头	温度/℃
枪管及弹头	20	200	300	400	500	600
枪管材料/MPa	1195	1070	1045	985	865	580
弹头壳铜H90/MPa	117	112	105	100	85	72

Fig.4 Motion postures of bullet in cold and hot gun states

Fig.5 Calculation method for analysis of thermal dispersion

Fig.6 Finite element model of barrel

Fig.7 Temperature variation of inner wall of barrel at 240mm from bore bottom during continuously firing

Fig.8 Finite element model of bullet-barrel interaction

Fig.9 Coupled calculation process of interior ballistics and finite element model[18]

Fig.10 Meplat swing trajectory in the chamber in hot gun state

Table 2 Initial parameters and deviations of bullet at muzzle after 150 hot gun shooting when the bullet has limit deviation

均值、极差范围与均方差	初速/ (m·s^-1)	Y轴方向出膛速度偏角/(°)	X轴方向出膛速度偏角/(°)	Y轴方向弹轴摆角/(°)	X轴方向弹轴摆角/(°)	Y轴方向章动角速度η/(rad·s^-1)	X轴方向章动角速度 ξ/(rad·s^-1)
均值	912.0	0.0384	0.052	-0.0084	0.0081	11.0	-56.7
极差范围	34.0	0.2	0.2	5.34	5.34	25.0	25.0
均方差	12.6	0.074	0.074	2.01	2.01	9.27	9.27

Fig.11 Input interface of bulet dispersion in hot gun state

Fig.12 Bullet dispersion of hot gun

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