Acta Armamentarii

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2020, 41(1): 0.

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Research on Simulation Method of Effective Damage Area of Equipment Based on Functional Damage

CHEN Cai， SHI Quan， YOU Zhifeng， WANG Yadong, GE Hongyu, ZHANG Fang

2020, 41(1): 1-12. doi:10.3969/j.issn.1000-1093.2020.01.001

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A method for using the effective damage area to set up the test site is proposed to collect the enough effective damage data in the equipment battle damage test. A solving model for effective damage area is established, and a concept of generalized damage area and task-based equipment functional damage probability is proposed. For the solution of generalized damage area, the physical damage modeling and simulation methods are studied, including fragment damage effectiveness model, equipment description model for fragment damage simulation, equipment fragment damage response model and equipment damage simulation process model. For the solution of equipment functional damage probability, the establishment method and steps of equipment damage simulation model are analyzed. A concept of equipment damage injection is proposed, and the implementation methods and steps of damage injection are analyzed. The simulated results show that the proposed method for solving the effective damage area of equipment is feasible and effective, and has great practical significance to optimize the design of battle damage test program and reduce the cost-effectiveness of test. Key

Research on Deformation Inhomogeneity along Wall Thickness Direction of Cold Radial Forged Barrel

XU Baochi， SHI Bikun， FAN Lixia， YANG Chen， FU Yunfeng, DONG Xuehua

2020, 41(1): 13-20. doi:10.3969/j.issn.1000-1093.2020.01.002

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In order to analyze the deformation inhomogeneity along wall thickness direction of cold radial forging barrel, the deformation field, mechanical properties and texture components in the wall thickness direction are studied by means of finite element software, mechanical tensile test and texture analysis. The results show that large shear stresses exist in the outer and middle layers of barrel during the forming process. The flow velocity of each layer in the wall thickness direction is inconsistent due to shear stress, thus causing the uneven deformation of barrel. The shear texture ({112} 111，{110} 001) is formed in the middle and outer layers of barrel due to uneven deformation, which results in obvious difference in axial strength performance of barrel wall thickness direction after forging. The strengths of outer and middle layers are lower, and the strength of inner surface layer is higher. In order to control the inhomogeneity along the wall thickness direction of barrel after forging, the influences of forging ratio, tail pressure, axial feed speed, hammer head forging frequency and hammer angle on the shear stress distribution in the middle layer of barrel are analyzed by using the control variable method. The analysis results show that a higher axial feed speed and a smaller hammer inlet angle can be selected to reduce the deformation inhomogeneity along wall thickness direction of formed barrel. Key

Strength Analysis of Rails and Panels of Cantilever Electromagnetic Railgun during Launching

HE Wei, WEI Yanjing

2020, 41(1): 21-31. doi:10.3969/j.issn.1000-1093.2020.01.003

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A cantilevered double-layer elastic beam model with the rails as upper beams and the panels as lower beams is established for further investigating the model theory of electromagnetic railgun. The analytical method is used to get the bending moment and stress of the model during launching. The numerical solution is compared with the analytical solution. The results show that the numerical solution is in good agreement with the analytical solution, and the analytical method is verified to be reliable. The maximum dynamic response of double-layer elastic beam occurs in the range of 0 to 0.5 m from starting position, and the responses of upper beams are bigger than those of lower beams. The research results can be used for the design and strength analysis of electromagnetic railgun. Key

Research on the Damage and Hot-spot Generation in Explosive Charges during Penetration into Single- or Multi-layer Target

CHENG Lirong， WANG Dewu， HE Yuanji

2020, 41(1): 32-39. doi:10.3969/j.issn.1000-1093.2020.01.004

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It is difficult to study the influencing mechanism of explosive charges stability during the penetration into targets in a complex impact environment. The microscale hot-spot generation models which include crack friction and pore collapse are used to simulate the dynamic response, damage evolution and hot-spot generation of explosive charges during the penetration into the single- and multi-layer targets. The different generating mechanisms of hot-spot are analyzed through simulation and compared with the experimental results. The simulated results show that it is easy to generate the hot-spot in the explosive charges during the penetration into multi-layer target compared with single-layer target, and the explosive charges can easily be damaged more seriously under repeatedly loading and trajectory deflection in the penetration into multi-layer target, which also generates the hot-spot due to crack friction and pore collapse. The areas of head and tail of the explosive charges should be especially protected, where the hot-spots are easily generated. The influence factors, such as penetration velocity, fracture toughness and initial porosity of explosive charges, are analyzed. The stability of explosive charges can be improved by reducing the stress amplitude, decreasing the oscillation times of explosive charges in a shell, increasing the strength of explosive material and reducing the initial defect of charge.Key

Uncertainty Quantification Analysis of Solid Rocket Motor Grain Ignition at Low Temperature Based on Improved PolynomialChaos Expansion

LI Yangtian， LI Haibin， WEI Guangmei， WENG Jiexin

2020, 41(1): 40-48. doi:10.3969/j.issn.1000-1093.2020.01.005

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In the process of computing the polynomial chaos expansion (PCE) coefficients based on projection method, an improper PCE order and Gauss point number may lead to overfitting and underfitting problems, which impacts the computing accuracy of PCE surrogate model seriously. An improved PCE method is presented to avoid overfitting and underfitting. In the improved PCE method, the adaptive PCE order P^* is determined, the adaptive uniform grid (N^*)^d is determined to compute the sensitivity indices of each input variable, and then an adaptive non-uniform grid is constructed based on obtained sensitivity indices to compute PCE coefficients. The proposed method is adopted to analyze an example of solid rocket motor ignition at low temperature, in which the effect of material parameter randomness on grain output response are studied and the probability distribution of output response is obtained. A more accurate result can be obtained by the proposed method, and the accuracy and efficiency of the proposed method are verified through comparing with traditional methods. Key

Preparation and Characterization of Nano 24681012-hexanitro-24681012-hexaazaisowurtzitane/135-triamino-246-trinitrobenzene Energetic Composites

LIU Yan， AN Chongwei， LUO Jin， WANG Jingyu

2020, 41(1): 49-55. doi:10.3969/j.issn.1000-1093.2020.01.006

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In order to reduce the sensitivity of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), CL-20/1,3,5-triamino-2,4,6-trinitrobenzene (TATB) energetic composites were prepared by using one-step ball milling method. The properties of raw materials and energetic composites were characterized by using scanning electron microscope, X-ray diffractometer, infrared spectrometer and diffrential scanning calorimetery.The impact sensitivity test was carried out. The results show that the as-prepared product is not a simple physical mixture of CL-20 and TATB, but a new crystalline phase is formed. In the SEM pattern, compared with the raw materials, the morphology of CL-20/TATB composite is regular spherical or ellipsoidal, and the particle size is in the range of 50-200 nm. In the XRD pattern, the main diffraction peak in the final product is obviously different from the main diffraction peaks in the raw CL-20 and the raw TATB. New XRD diffraction peaks arise, which indicates that a new crystal form appears in the final product. The diffraction peak become wider due to the decrease in particle size. In FT-IR pattern, the position of characteristic vibration peak of the functional group in the CL-20/TATB composite is shifted due to the hydrogen bond between CL-20 (—NO₂ or —CH) and TATB (—NO₂ or —NH₂). In the DSC curve, compared with raw CL-20 and raw TATB, the exothermic peak of the CL-20/TATB composite is advanced, which indicates that the thermal decomposition activity of CL-20/TATB composite is stronger than those of raw CL-20 and raw TATB. In the impact sensitivity test, the characteristic height of CL-20/TATB composite is 62 cm higher than that of CL-20 , indicating that the impact safety of CL-20/TATB is better than that of CL-20. Key

Selection of System Models for Continuous Self-calibration of Hybrid Inertial Navigation System Based on Observability Analysis

WANG Qi, WANG Lixin, LIANG Shuhui, QIN Weiwei, SHEN Qiang

2020, 41(1): 56-67. doi:10.3969/j.issn.1000-1093.2020.01.007

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Focusing on the selection of system models for continuous self-calibration of hybrid inertial navigation system, the observability and applicable conditions of different system models are analyzed based on the observability of inertial instrument installation errors. Three kinds of system models are established by using different kinetic equations and observation equations. The observability of system models is analyzed by analyzing the relationship among system measurements and inertial instrument installation errors based on the definition of observability. Two kinds of system models are observable: one is to use misalignment angle equation as the kinetic equations, and accelerometer output equation as a observation equation, and the other is to use inertial platform frame angle equation as the kinetic equations, and accelerometer output and inertial platform frame angle equation as the measurement equations. Three kinds of system models are simulated and experimented to verify the analysis results. Key

Research on Field Calibration Method for MEMS Accelerometer Based on Support Ellipsoid Fitting

ZHOU Quan, YAO Minli, SHEN Xiaowei

2020, 41(1): 68-74. doi:10.3969/j.issn.1000-1093.2020.01.008

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In order to solve the problem that the zero drift error, scale factor error and cross-coupling error of accelerometer in the micro-electro mechanical system change with time, a calibration method based on the support degree ellipsoid fitting is proposed. The proposed method can be used easily, quickly and efficiently to calibrate the accelerometer outdoor. Based on the traditional ellipsoid fitting method, this method combines the support method with the ellipsoid method. An ellipsoid constraint model and the support matrix are established for calibrating the errors of the micro-electro-mechanical system (MEMS) accelerometer. Finally，the output of MEMS accelerometer is compensated by using an error compensation equation. It is proved by experiments that the proposed method can be used for calibrating without precision calibration equipment, and its calibration accuracy is twice of the traditional ellipsoid fitting method. Key

Experimental Study of Afterburning Enhancement Effect for Blast Load in Confined Compartment Space

KONG Xiangshao, KUANG Zheng, ZHENG Cheng, WU Weiguo

2020, 41(1): 75-85. doi:10.3969/j.issn.1000-1093.2020.01.009

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In order to investigate the afterburning enhancement effect of detonation products for the blast load in a confined space, the explosion experiments of 5 different masses of TNT were performed in the confined spaces filled with air and helium. The data about shockwave-time history, quasi-static pressure, temperature of mixed gas in a confined space, and both the dynamic response and final deformation of steel plates were recorded by using the pressure and temperature sensors and the three-dimensional digital image correlation (DIC) method. The experimental results were analyzed and compared. The results show that the afterburning of detonation products of TNT has a dramatic influence on the confined blast load and the structural responses. The quasi-static pressures and temperature peaks of the five different masses of TNT explosions in helium environment are reduced by 38.81%-46.85% and 57.53%-76.35%, respectively, and the final deformation of tested specimens are decreased by 19.1%-48.9% compared with those of TNT explosions in air environment. It is suggested that the afterburning enhancement effect of detonation products for the confined blast load should be taken into account in predicting the dynamic responses of structures. Key

Parameter Estimation of Linear Frequency Modulation Signal Based on Interpolated Short-time Fractional Fourier Transformand Variable Weight Least Square Fitting

CAO Weihao， YAO Zhixiang， XIA Wenjie， YAN Su

2020, 41(1): 86-94. doi:10.3969/j.issn.1000-1093.2020.01.010

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A Rife interpolation short-time fractional Fourier transform (STFRFT) -variable weight least square fitting (VWSF) algorithm is proposed for solving the problem of low parameter estimation accuracy of linear frequency modulation (LFM) signal under low signal-to-noise ratio (SNR). STFRFT is used to improve the aggregation of LFM signals, and the estimation accuracy of instantaneous frequency of signal is improved by VWSF, thus estimating the instantaneous frequency, initial frequency and modulation frequency of LFM signal. The Cramer-Rao lower bound (CRLB) of the signal parameters estimation is derived, and the factors affecting the estimated parameter CRLB and the variation of CRLB with it are analyzed. The simulated results show that the Rife interpolation STFRFT-VWSF algorithm has better estimation accuracy of LFM signal parameters, the parameter estimation and CRLB theoretical analysis are rational, and the feasibility of the algorithm is proven through sea test. Key

Neural Network-based Information Fusion Technique for Distributed Passive Sensor

LI Hongrui

2020, 41(1): 95-101. doi:10.3969/j.issn.1000-1093.2020.01.011

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The information correlation (IC) of mult-sensor and the target estimation (TE) of single sensor are difficult in distributed passive sensor (DPS) information fusion (IF). For example, the information from different sensors cannot be registered in time and space, and the false targets cannot be eliminated due to the interdependence and mutual restriction of TE. Therefore a hybrid ordered delaminated information fusion structure (HODIFS) is introduced to avoid the multiple combinations of multi-sensor information. A united optimization model (UOM) based on 2-sensor IC and TE is established, which uses an optimization Hopfield neural network (HNN) algorithm and avoids the complex combination computation of correlation. Simulated results indicate that the HODIFS with UOM based on HNN is effective in the DPSIF, in which HNN is easily realized and the performance of DPSIF can be improved. Key

Research on the Physical Layer Security Technologies of Two-way Cooperative Relay Networks

PAN Lei, LI Zan, LI Xiangyang, ZHANG Fenggan

2020, 41(1): 102-107. doi:10.3969/j.issn.1000-1093.2020.01.012

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In the information battlefield, more and more attention is attached to the application of the military mobile communication system in the field of military communication. In order to improve the secrecy performance of military mobile communication system, the physical layer security transmission of two-way cooperative relay systems is investigated. A joint relay selection and power allocation scheme based on the standard particle swarm optimization is proposed to maximize the system secrecy rate against the eavesdropper. The proposed scheme is compared with equal power allocation with optimal relay selection scheme, optimal power allocation with random relay selection scheme and equal power allocation with random relay selection scheme through simulation. The simulated results show that the proposed scheme outperforms the other schemes. It can be used to improve the system secrecy rate, effectively resist the eavesdroppers, and significantly improve the system secrecy performance. Key

Evaluation Method for Effectiveness of GNSS Spoofer

WANG Yue, HAO Jinming, LIU Weiping

2020, 41(1): 108-118. doi:10.3969/j.issn.1000-1093.2020.01.013

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The performance of GNSS spoofer, as one of the important tools of "navigation warfare", is directly related to the survival probability of the protected target. To provide an effectiveness evaluation with high confidence, the specific detection methods and calculation models of various indicators are established on the basis of a reasonable effictiveness evaluation indicator system and an evaluation test platform, and a basic method is proposed for equipment effectiveness evaluation. A theoretical evaluation threshold is set by using fuzzy comprehensive evaluation model, semi-qualitative and semi-quantitative grading method and weighted product synthesis algorithm. Based on the all-digital, half size hardware-in-the-loop simulation and full physical field tests, the effects of the main performance indicators on spoofing effectiveness are analyzed. The results show that the spoofing effectiveness can be improved by shortening the time of signal acquisition and increasing the power of spoofing signal and so on. Key

The Recovery of Underwater Target's Free Field Acoustic Radiation Characteristics and Identification of Far-field AcousticRadiation Hotspot

LIN Wei, XIA Maolong, LIU Zhenghao, LI Sheng, MENG Chunxia

2020, 41(1): 119-126. doi:10.3969/j.issn.1000-1093.2020.01.014

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Acquiring the acoustic characteristics of target in water is very important for the identification and analysis of a target. A field separation technique combined sound field recovery technology based on boundary element method with surface contribution method is proposed to achieve the free field conditions for testing the sound characteristics of target in water and eliminate the interference of the energy flow at the surface of structure to the identification of hotspot in the far-field acoustic radiation. The proposed method can be used to obtain the free field acoustic characteristics of the underwater target in the non-free and near field environment and identify hotspot in far field in water. The simulated results show that there are no significant differences among the sound pressure and sound power obtained by the sound field recovery technology and those in the free field. The surface contribution method is used to filter out the energy flow circulating on the surface of vibrating structure, so far-field acoustic radiation hotspot can be identified in near field. The proposed method breaks through the limitations of test environment, significantly reduces the testing costs and has certain engineering application value. Key

Parameter Identification of High-speed USV Maneuvering Response Model Based on Maximum Likelihood Algorithm

CHU Shixin， MAO Yunsheng， DONG Zaopeng， YANG Xin

2020, 41(1): 127-134. doi:10.3969/j.issn.1000-1093.2020.01.015

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The maneuverability prediction accuracy of high-speed unmanned surface vessel（USV）depends on the accuracy of parameter acquisition in its motion model. The high precision model parameters are difficultly obtained by commonly using the extended Kalman filter（EKF）method. The maximum likelihood（ML）method is used to identify the second-order nonlinear response model parameters of unmanned maneuvering motion. 20° zigzag simulation experiment is carried out to collect the data of heading angle and rudder angle with the parameters of an USV response model. A ML identification method is designed based on identification principle and the forward difference method, and the model parameters are obtained by identification. Further research finds that part of parameters identified by ML method are inaccurate because of parameter drift. The analysis shows that the reason of parameter drift is to neglect the influence of the rudder angle change rate for processing the zigzag experimental data by the difference method. An improved identification research based on ML method with sine simulation experimental data was carried out, in which the rudder angle change rate can be directly derived from the rudder angle. The simulation experiments of USV maneuverability motion based on the results identified by ML and EKF method were carried out. The experimental results show that the result identified by ML method is more accurate than that identified by EKF method, and the parameter drift can be solved effectively by identifying with sine simulation experimental data to improve the identification accuracy of ML method. Key

Research and Optimization of Turbocharging Matching for Two-stroke Aero Engine

ZHANG Shuo， ZHAO Zhenfeng， DONG Xuefei， YE Ying

2020, 41(1): 135-142. doi:10.3969/j.issn.1000-1093.2020.01.016

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The turbocharging matching is researched for the problem of power reduction of two-stroke aero engines at high-altitudes. An one-dimensional simulation model of a natural aspirated two-stroke aero engine was established and experimentally verified. Based on the verified model, a turbocharger is matched, and a turbocharged engine model is established. The structure optimizing and control strategies of bypass valve in exhaust system are proposed to broaden the working range of turbocharger through the calculation and analysis of turbocharging matching at variable altitudes. A two-stroke turbocharged aero engine with 76% power recovery at 7 000 m altitude was designed, which can meet the demand of an unmanned aerial vehicle’s mission profile. Key

An Experimental Investigation on the Strain Rate-dependent Tensile Strength of Plain Concretes

FU Yingqian， YU Xinlu， DONG Xinlong， ZHOU Fenghua， NING Jianguo， LI Ping

2020, 41(1): 143-151. doi:10.3969/j.issn.1000-1093.2020.01.017

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Concrete-like materials have a clear strain-rate strengthening effect on tension strength. All specimens, including Brazilian discs and bars, were prepared and cured under the same laboratory conditions. The dynamic Brazilian split tests and the spalling tests were conducted by employing the Hopkinsion pressure bar as a loading platform. The failure processes of specimens in the tests were observed by using ultra-high speed camera and digital image correlation (DIC) method. In quasistatic or dynamic Brazilian split test,the disk specimen is assured to be splitted at the center of the disk. In spalling test, DIC analysis is applied to determine the exact timing and location of spall fracture, specifically in the case of multiple spallations. The dynamic tensile strengths of plain concrete discs and bars were obtained through these tests. The strain rate strengthening rules of split and spall tensile strengths are analyzed. The research results show that, for the dynamic split test, the central breaking only happens at relative low strain rate, and the critical strain rate is about 10 s^-1; the tensile strength and strain rates of multi-spalling can be achieved accurately by using a DIC-based analytical method; dynamic strain rate streng-thening rule of tensile strength are got by linearly fitting the experimental data, the increasing slope of tensile strength in spalling test is larger than that in dynamic Brazilian split test, and the dynamic increase factor of concrete can reach to above 5. The test results, based on the accurate measurements of tensile strength, can be used as a reference for the design and reconsideration of civil and military engineering.Key

Design and Fabrication of Micro-end Mills for Minimally Invasive Milling of Bone Tissue

GAO Peng, LIANG Zhiqiang, WANG Xibin, LI Shidi, ZHOU Tianfeng

2020, 41(1): 152-160. doi:10.3969/j.issn.1000-1093.2020.01.018

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For the special requirement of ultra-small micro-end mill for minimally invasive milling of bone tissue, the structural optimization design of special-shaped micro end mills is studied. Three kinds of micro-end mills (helical-shaped, △-shaped and □-shaped) with diameter of 50 μm were designed and manufactured, and their milling performances were also investigated. The geometric structures of micro-end mills with different shapes are analyzed, and the static analysis of the mills is conducted to study the effect of geometric structure of micro-end mill on its stiffness and strength. The precision milling method and milling quality of three kinds of micro-end mills are investigated. The bone tissue minimally invasive milling experiments using ultra-small micro end mills were carried out, and the morphologies of milled bone tissues were observed. The milling quality of bone tissue workpiece was analyzed. In the process of bone tissue micro milling, the helical-shaped micro-end mill is prematurely fractured, △- and □-shaped micro-end mills can cut for long time. For the △-shaped micro-end mill, the machined grooves have small burr width and edge collapse, and higher surface quality. The △-shaped micro-end mill is more suitable for minimally invasive milling of bone tissue. Key

A New Testability Modeling Method Based on Hierarchical Generalized Stochastic Petri Nets

ZHAI Yuyao, SHI Xianjun, QIN Yufeng, L Jiapeng

2020, 41(1): 161-170. doi:10.3969/j.issn.1000-1093.2020.01.019

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Since the current equipment system adopts the hierarchical and modular design, the maintenance level and testability modeling complexity are greatly improved. A testability modeling method based on hierarchical generalized stochastic Petri nets (HGSPN) is proposed. The problems existing in the mainstream modeling method and the reasons for selecting the GSPN modeling are analyzed by comparing the mainstream modeling method with the generalized stochastic Petri net (GSPN) modeling method. The equipment is hierarchically divided, and a HGSPN model is established. The multiple failure modes exist in the system and its components. A complete coding scheme is proposed to distinguish these failure modes. The accessibility algorithm is used to obtain the hierarchical dependency matrix, and the testability evaluation mathematical model is used to obtain the testability level. The testability information of each level is aggregated to obtain the testability level of the complete equipment. Taking a missile engine system as an example, the testability indicators are evaluated, and 100% fault detection rate and 66.7% isolation rate are obtained. The effectivenesses of the proposed modeling method and corresponding algorithm are verified.Key

Bayesian Network Method for Reliability Analysis of Complex Uncertainty Systems

WANG Haipeng, DUAN Fuhai

2020, 41(1): 171-182. doi:10.3969/j.issn.1000-1093.2020.01.020

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The uncertainty in reliability analysis of complex multi-state system may be due to the complexity of system structures, the limited test samples, and the insufficient reliability data. A new reliability analysis method for complex uncertainty system based on non-deterministic membership functions and interval characteristic quantities is proposed by introducing the fuzzy mathematics and grey system theory into the Bayesian network model. The influences of human subjective factors on the selection of membership function can be effectively avoided and the failure states of components and systems can be defined accurately by using the variable membership function to describe the failure states of component and system. The uncertain failure logic relationship between component and system can be effectively expressed by substituting the exact value in the conditional probability table with the interval grey number. A parameter planning model of the system reliability characteristic quantity is constructed, and the system reliability characteristic quantity is expressed in the form of an interval. The proposed method is applied in the reliability analysis of the satellite propulsion system. The results show that the method can be used to analyze the system reliability and component importance under fuzzy uncertain conditions, and the calculation amount is controllable. It is an effective reliability analysis method for complex uncertainty systems. Key

Research on the Leak Mechanism and Experiment of Double Seam Structure of Metal Packaging Container

YANG Dan, YIN Fenglong, LIANG Xiaodong, LIAO Hongbo, LI Erkang

2020, 41(1): 183-188. doi:10.3969/j.issn.1000-1093.2020.01.021

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A viscous-flow leakage model is established for double seam structure to investigate and solve the gas sealing problem of metal packaging containers. The effects of geometric dimension and leakage medium properties on the gas leak rate of double seam structure are quantitatively studied. The results show that the gas leakage caused by the permeation of sealant is unavoidable, and the permeation leak rate is smaller than the total gas leak rate. When the adhesive width of sealant and the diameter of packaging container are fixed, the total gas leak rate of double seam structure is affected by the passage width between the sealant and the metal material. In addition, the leak rate of the passage is related to the third power of the passage width. The total gas leak rate of double seam structure is larger than 9.0×10^-9 Pa·m³/s under good sealing condition. The predicted section size of the leakage passage is consistent with the experimental results. This study can provide theoretical basis for the sealing and leakage control of metal packaging containers. Key

Research on Flow Characteristics of Gear Pump Considering Cavitation Effect

ZHOU Junjie, YUAN Shihua, JING Chongbo

2020, 41(1): 189-195. doi:10.3969/j.issn.1000-1093.2020.01.022

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The flow quality of gear pump has an important influence on the performances of hydraulic control system and lubrication system in the vehicles. The flow characteristics of gear pump in the cavitation state are studied. The gas content is calculated from the initial state and the real-time pressure, neglecting the faintly dissolved effect of air in the oil. A fluid cavitation model is established, in which the effect of gas content on oil density, effective bulk modulus and viscosity is considered. The fluid cavitation model is coupled with a gear pump dynamics model and simulated in AMESim environment. The effects of the suction pressure, rotation speed and load pressure on the flow pulsation of gear pump are analyzed. The results show that the pressure pulsation and volumetric efficiency obtained by the simulation model are consistent with the experimental data. The decrease in the suction pressure leads to the increase in the flow pulsation of gear pump and the decrease in the volumetric efficiency. The increase in the rotation speed increases the cavitation tendency. The increase in load pressure has little effect on the flow pulsation of gear pump. Key

Snake-like Trajectory Design and Simulation of Submarine-launched Wire-guided Torpedo

WANG Shunjie， XU Zhaopeng, ZHU Weiliang， YE Xuefan

2020, 41(1): 196-201. doi:10.3969/j.issn.1000-1093.2020.01.023

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During torpedo attacking, it is against target acquisition probability under the condition that the target angle is very small and only target bearing information can be obtained. The snake-like trajectory searching concept is elaborated, and the two opportunities of using the snake-like trajectory to search a target are proposed. A snake-like trajectory searching control model is established. It was validated through simulation that the snake-like trajectory searching of wire-guided+wake homing torpedo is effective for increasing the wake acquisition probability at a very small target angle and with only target bearing information. In order to solve wake entry shipboard uncertainty problem, a method of attacking a target by wake+acoustic homing is proposed, which can ensure the probability of torpedo hiting the target. The simulated results show that the snake-like trajectory searching of wire-guided+acoustic homing torpedo is effective for enlarging the torpedo searching range without target bearing information, and the target acquisition probability is high than that through direct searching. Key

Experimental Optimization of Processing Parameters of Stranded Wires Helical Springs Based on DoE Method

YI Lili, YANG Wenhang, WANG Shilong

2020, 41(1): 202-208. doi:10.3969/j.issn.1000-1093.2020.01.024

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The research on the coupling mechanism of the processing parameters of stranded wires helical springs (SWHS) for the product quality has been incomplete, which leads to the low yield of SWHS and the difficulties in large-scale promotion. An experimental method for optimizing the processing parameters of SWHS is proposed. The dichotomy method is utilized to obtain cable pitch, which is proved to meet the stiffness performance requirement of SWHS. The optimization experiments of three processing parameters, including mandrel diameter, spring pitch and wire tension, are designed based on DoE method. An optimal SWHS processing parameter group is obtained by means of the mean analysis of signal-to-noise ratio. The practical processing of reset SWHS for drill pipe proves that DoE method is feasible. The research results show that the DoE method can be used to reduce the acquisition time of processing parameters of SWHS, and save a lot of costs for the research on SWHS processing technology. Key

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