Thermal Demagnetization Characteristics of Nd-Fe-B Used in Eddy Current Recoil Mechanism of Artillery

doi:10.12382/bgxb.2023.0616

Abstract

Abstract:

Permanent magnet eddy current recoil brake is an innovative design in the field of efficient control of recoil resistance of artillery. In the application scenario of artillery with high energy consumption density and relatively closed working environment, there is a serious temperature rise in the eddy current recoil brake. High temperature will lead to the decrease in the magnetic properties of Nd-Fe-B materials and then affect the recoil characteristics. At present, the thermal demagnetization process of Nd-Fe-B is not clear and lacks theoretical expression. In order to grasp the thermal demagnetization characteristics of Nd-Fe-B, the demagnetization process of NdFeB at different temperatures is quantitatively analyzed from the perspective of microscopic magnetic moment heating motionbased on the micromagnetic simulation method, and the demagnetization curve of macroscopic Nd-Fe-B is obtained. In order to use the demagnetization curve for better guiding the engineering design, the J-A model is used to describe the demagnetization behavior of Nd-Fe-B, and the experimental verification is carried out. The magneto-thermal coupling numerical calculation of demagnetization and resistance degradation of Nd-Fe-B is carried out based on the traditional residual magnetic flux density model and the J-A model. By comparing with the experimental results of the prototype, it is found that the J-A model is more accurate in describing the magnetic properties of Nd-Fe-B. The working performance of recoil brake under different working temperatures and chamber pressures is calculated, and the demagnetization characteristics of Nd-Fe-B and the damping characteristics of recoil brake under the temperature field are analyzed. The results show that the maximum demagnetization of Nd-Fe-B is 0.351T under the worst working conditions, and the maximum recoil displacement of recoil brake is 1108mm, which provides a theoretical reference for the design of eddy current recoil brake.

Key words: gun eddy current recoilbrake, Nd-Fe-B, micromagnetic theory, demagnetization characteristic

CLC Number:

TJ301

SUN Zhengping, YANG Guolai, LI Lei, WANG Liqun. Thermal Demagnetization Characteristics of Nd-Fe-B Used in Eddy Current Recoil Mechanism of Artillery[J]. Acta Armamentarii, 2024, 45(8): 2712-2727.

Figures/Tables 28

Fig.1 Micromagnetic numerical simulation of Nd-Fe-B single crystal demagnetization process

Table 1 Magnetic parameters of Nd-Fe-B

晶相	M_s/(A·m^-1)	K₁/(J·m^-3)	A_e/(J·m^-1)	α
主相	1.28×10⁶	4.2×10⁶	1.047×10^-11	0.010
界相	1.28×10³	4.2×10⁴	1.047×10^-12	0.002

Fig.2 Finite element micromagnetic polycrystal model of Nd-Fe-B

Fig.3 Cloud diagram of magnetic moment distribution during demagnetization

Fig.4 Micro-magnetic simulation input and result

Fig.5 Microscopic mechanism of the effect of temperature field on the demagnetization process of Nd-Fe-B

Fig.6 Demagnetizing field of different crystal grain surfaces

Fig.7 Phenomenon caused by magnetic domain movement in demagnetization process

Fig.8 Experimental equipment and test flow

Fig.9 Demagnetization curves obtained from micromagnetic numerical simulation, J-A hysteresis model and experimental measurement

Table 2 Parameter values of J-A model at different temperatures

温度/ ℃	饱和磁化强度/ (kA·m^-1)	畴间耦合参数/ (kA·m^-1)	形状参数	钉扎损耗/ (kA·m^-1)	可逆磁化率	拟合精度/ %
20	1300	102	0.840	1310	0.0002	93.1
40	1280	104	0.735	1105	0.0002	92.4
60	1250	111	0.631	848	0.0002	82.5
80	1240	97	0.549	655	0.0002	82.1
100	1220	99	0.453	480	0.0002	79.2

Fig.10 Dynamic modeling of eddy current recoilbrake

Table 3 Material parameters of alumina, DT4 and air

材料	电导率/(S·m^-1)	相对介电常数	密度/(kg·m^-3)	恒压热容/(J·kg^-1·℃^-1)	导热率/(W·m^-1·℃^-1)
Al₂O₃ (内筒材料)	2.7×10⁷	1	3900	900	238
DT4 (外筒材料)	2.0×10⁷	1	7860	460	46
空气	1	1	1.293	1004	0.0244

Fig.11 Numerical calculation flow of eddy Currentrecoil brake

Table 4 Nd-Fe-B basic material parameters

电导率/(S·m^-1)	相对介电常数	密度/(kg·m^-3)	恒压热容/(J·kg^-1·℃^-1)	导热率/(W·m^-1·℃^-1)
6.25×10⁵	1	7400	400	8.95

Table 5 Magnetic parameters of Nd-Fe-B under J-A hysteresis model

M_s/(kA·m^-1)	α_ja/(kA·m^-1)	a	k/(kA·m^-1)	c	初始磁化强度/(kA·m^-1)
-T+1318	-0.00483T+0.93	-10.45T+1503	102	0.0002	-1.066T+1172

Table 6 Magnetic parameters of Nd-Fe-B under the residual flux density model

剩磁/T	真空磁导率/(H·m^-1)	相对磁导率
-0.00134T+1.4727	4π×10⁷	e⁰^.⁰¹⁰⁸^T

Fig.12 Experimental design of electromagnetic buffer device

Fig.13 Impact load and reentry force curves

Fig.14 Comparison of electromagnetic braking forces in the impact experiment of prototype, and the numerical simulations of residual magnetic flux density model and J-A hysteresis model

Fig.15 Comparison of recoil displacements in the impact test of prototype, and the numerical simulations of residual magnetic flux density model and J-Ahysteresis model

Table 7 Maximum recoil displacementmm

工况	原理样机实验结果	剩余磁通模型	J-A模型
1	550	594(44)	536(-14)
2	761	864(103)	773(12)
3	867	962(95)	863(-4)

Fig.16 Fitting and comparison of experimental and micro-magnetic simulation B-H curves of two models

Fig.17 Numerically simulated results of heat accumulation effect inside the brake

Fig.18 Variation of average magnetic flux density of Nd-Fe-B array under various emission loads

Fig.19 Variation of damping force and recoil displacement under various launch loads

Fig.20 Changes of demagnetization and recoil displacement with temperature

Table 8 Maximum demagnetization and maximum recoil displacement under different working conditions

工况	温度	最大去磁量/T	最大后坐位移/mm
	20	0.044	536
1	40	0.082	549
	60	0.155	570
	80	0.257	628
	20	0.052	773
2	40	0.094	796
	60	0.176	848
	80	0.317	919
	20	0.056	863
3	40	0.095	912
	60	0.179	986
	80	0.351	1108

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