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Experimental and numerical investigation on alternatives to sandy gravel

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Defence Technology（防务技术） 2024年第1期31卷 130-141页

作者： V.Denefeld H.Aurich fraunhofer institute for high-speed dynamics Ernst-Mach-Institut(EMI)Ernst-Zermelo-Str.479104FreiburgGermany fraunhofer institute for high-speed dynamics Ernst-Mach-Institut(EMI)Am Christianswuhr 279400KandernGermany

The NATO agreement STANAG 4569 defines the protection levels for the occupants of logistic and light armored *** Allied Engineering Publication,AEP-55,Volume 2 document outlines the test conditions for underbelly improvised explosive device(IEDs),which must be buried in water-saturated sandy *** use of sandy gravel has some drawbacks,for instance reproducibility,time consumption,and *** paper focuses on the investigation of four alternatives to sandy gravel,which could produce similar specific and cumulative impulses:a concrete pot filled with water,a concrete pot filled with quartz sand,a steel pot without filling and a concrete pot filled with glass spheres(diameter 200μm—300μm)and different water *** impulses are measured with a ring technology developed at the fraunhofer EMI.A numerical soil model based on the work of Marrs,2014 and Fi serov a,2006 and considering the soil moisture was used to simulate the experiments with glass spheres at different water contents,showing much better agreement with the experiments than the classical Laine&Sandvik model,even for high saturation *** results can be used to create new test conditions at original scale that are more cost-effective,more reproducible and simpler to manage in comparison to the current tests carried out with STANAG sandy gravel.

关键词： Improvised explosive device(IED) Specific impulse Momentum transfer Sandy gravel Glass spheres Numerical model Soil moisture

Damage visualization and deformation measurement in glass laminates during projectile penetration

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Defence Technology（防务技术） 2014年第2期10卷 226-238页

作者： Elmar STRASSBURGER Steffen BAUER Gregor POPKO fraunhofer institute for high-speed dynamics Ernst-Mach-Institute(EMI)Am Christianswuhr 2

Transparent armor consists of glass-polymer laminates in most *** formation and propagation of damage in the different glass layers has a strong influence on the ballistic resistance of such *** order to clarify(he course of events during projectile penetration,an experimental technique was developed,which allows visualizing the onset and propagation of damage in each single layer of the laminate.A telecentric objective lens was used together with a microsecond video camera that allows recording 100 frames at a maximum rate of 1 MHz in a backlit photography *** this technique,the damage evolution could be visualized in glass laminates consisting of four glass layers with lateral dimensions 500 mm x 500 *** evolution was recorded during penetration of 7.62 mm AP projectiles with tungsten carbide core and a total mass of 1 1.1 g in the impact velocity range from 800 to 880 m/*** order to measure the deformation of single glass plates within the laminates,a piece of reflecting tape was attached to the corresponding glass plate,and photonic Doppler velocimetry(PDV) was *** the photonic Doppler *** infrared laser is used to illuminate an object to be measured and the Doppler-shifted light is superimposed to a reference light beam at the *** simultaneous visualization and PDV measurement of the glass deformation allow determining the deformation at the time of the onset of *** analysis of the experimental data was supported by numerical simulations,using the AUTODYN commercial hydro-code.

关键词：变形测量玻璃层可视化弹丸穿透多普勒测速仪层板伤害

Extension of Flow Behaviour and Damage Models for Cast Iron Alloys with Strain Rate Effect

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Chinese Journal of Mechanical Engineering 2024年第3期37卷 297-310页

作者： Chuang Liu Dongzhi Sun Xianfeng Zhang Florence Andrieux Tobias Gersterc School of Mechanical Engineering Nanjing University of Science and TechnologyNanjing 210094China fraunhofer institute for Mechanics of Materials(IWM) 79108 FreiburgGermany fraunhofer institute for high speed dynamics Ernst-Mach-Institute(EMI)79104 FreiburgGermany

Cast iron alloys with low production cost and quite good mechanical properties are widely used in the automotive *** study the mechanical behavior of a typical ductile cast iron(GJS-450)with nodular graphite,uni-axial quasi-static and dynamic tensile tests at strain rates of 10^(-4),1,10,100,and 250 s^(-1)were carried *** order to investigate the influence of stress state on the deformation and fracture parameters,specimens with various geometries were used in the *** strain curves and fracture strains of the GJS-450 alloy in the strain rate range of 10^(-4)to 250 s^(-1)were obtained.A strain rate-dependent plastic flow model was proposed to describe the mechanical behavior in the corresponding strain-rate *** available damage model was extended to take the strain rate into account and calibrated based on the analysis of local fracture *** with the proposed plastic flow model and the damage model were conducted to observe the deformation and fracture *** results show that the strain rate has obviously nonlinear effects on the yield stress and fracture strain of GJS-450 *** predictions with the proposed plastic flow and damage models at various strain rates agree well with the experimental results,which illustrates that the rate-dependent plastic flow and damage models can be used to describe the mechanical behavior of cast iron alloys at elevated strain *** proposed plastic flow and damage models can be used to describe the deformation and fracture analysis of materials with similar properties.

关键词： Dynamic behavior of materials Strain rate dependency Damage model Voce model Cast iron

Experimental study about the influence of adhesive stiffness to the bonding strengths of adhesives for ceramic/metal targets

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Defence Technology（防务技术） 2016年第2期12卷 188-200页

作者： W.SEIFERT E.STRASSBURGER S.GREFEN S.SCHAARE fraunhofer-institute for high-speed dynamics Ernst-Mach-Institute(EMI)Am Christianswuhr 279400 KandernGermany Rheinmetall Ballistic Protection GmbH Neuer Weg 2447803 KrefeldGermany

The aim of the investigations presented here was to understand how the stiffness of the adhesive affects the failure of ceramic tiles adhered to metallic backings. The working hypothesis was that varying the adhesive stiffness could have the same effect on the ballistic performance as a variation of the adhesive *** different projectile/target combinations were utilized for ballistic tests in order to generate extremely different loading conditions. With targets consisting of 6 mm aluminum oxide ceramic and 6 mm aluminum backing, complete penetration occurred in each test with 7.62 mm tungsten carbide core AP ammunition at an impact velocity of 940 m/s. In contrast, with ceramic tiles of 20 mm thickness on 13 mm steel backing,no penetration of the ceramic occurred at the impact of a 7.62 mm ball round at 840 m/*** different types of adhesive(high-strength till high-flexible) were tested in both configurations. The elongation of the adhesive layer, the deformation of the metallic backing and the failure of the ceramics were observed by means of a high-speed camera during the projectile/target *** results of the ballistic tests showed that a higher fracture strain caused a larger deformation of the backing compared to adhesives, which exhibit a high tensile strength and low fracture *** experimental results indicate that the damage behavior of the ceramic/metal composites depends on the absolute elongation of the adhesive layer. This can be controlled either by the thickness or the stiffness of the bonding layer.

关键词：氧化物陶瓷粘结层金属靶刚度强度影响实验陶瓷/金属复合材料粘接

Speciation in nanosecond laser ablation of zinc in water

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Science China(Physics,Mechanics & Astronomy) 2022年第7期65卷 90-98页

作者： Stefan Reich Yannis Klügl Anna Ziefuss RenéStreubel Jorg Gottlicher Anton Plech institute for Photon Science and Synchrotron Radiation Karlsruhe Institute of TechnologyKarlsruhe D-76021Germany Department of Technical ChemistryⅠand Center for Nanointegration Duisburg-Essen University of Duisburg-EssenEssen D-45141Germany fraunhofer institute for high-speed dynamics Ernst-Mach-Institute(EMI)Freiburg 79104Germany

In situ experimental methods have been applied to resolve mass flow and chemical speciation in the pulsed laser ablation of zinc in water. The chemical speciation has been resolved by time-resolved μ-X-ray absorption spectroscopy and mapped onto the macroscopic mass flow during material ejection from the metallic target and bubble dynamics of evaporated water. Large particles and agglomerates have been detected via dark-field X-ray imaging with a Shack-Hartmann sensor. The characteristic of the dynamics is that the vapor bubble is nearly homogeneously filled with ablated material. This persists during bubble collapse,which means that the ablated particles are captured and retracted towards the target. Limited mass escape is indicated by the X-ray absorption signal. Importantly, the near-edge structure at the Zn-K;transition delivers information on the chemical state of the ejected material. It clearly confirms that oxidation is not present within the bubble phase and the following sub-millisecond time scale. The oxidation proceeds on Zn nanoparticles in suspension on a second to minute course. Within the first microseconds,a Zn atom phase is detected that resembles Zn vapor. The addition of either reductive NaBH;or oxidative HAuCl;to the water phase influences the quantity of the atom contribution moderately, but does not influence the initial atom phase. Such behavior must be understood in terms of the nanosecond pulse excitation. After ejected material and a plasma is formed within the pulse duration of 7 ns the laser is able to further heat the ejecta and transform it partly into vapor. Correspondingly, the coupling of energy into the ablation zone as followed by plasma intensity and bubble size follows a threshold behavior as a function of laser fluence, marking the onset of laser-plasma heating. The reaction conditions inside the bubble are probably reductive due to the concomitant formation of excess hydrogen.

关键词： laser ablation in liquids elemental speciation X-ray absorption spectroscopy oxidation zinc oxide nanoparticles

Closed-loop flow control of an ultra-compact serpentine inlet based on nondimensional model

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Chinese Journal of Aeronautics 2020年第10期33卷 2555-2562页

作者： Xingya DA Jianchao FAN high speed Aerodynamics institute China Aerodynamics Research and Development CenterMianyang 621000China

Ultra-compact serpentine inlet faces serve inlet-engine compatibility issues due to flow *** ensure inlet-engine compatibility over a wide range of Mach number,novel active flow control techniques with the ability of being opened or adjusted as needed draw many attentions in recent *** this paper,a feedback control system was developed based on the method of microjet *** proposed system includes a pressure adjusting valve to adjust the control effort,a dynamic pressure sensor to sense the inlet distortion intensity,a signal processing instrument to calculate the Root-Mean-Squared(RMS)pressure,and a controller to implement feedback *** achieve high quality closed-loop controls at dynamic conditions,a novel nondimensional feedback method was *** advantage of this nondimensional method was validated at both off-design and arbitrarily changing Mach number *** a sectional PI control law,the RMS control error reduced more than 56%at arbitrary changing *** in this paper also showed that the dynamics of this nondimensional system can be simplified as a stable second-order overdamped system.

关键词： Closed-loop flow control Flow distortion Nondimensional feedback PI control Serpentine inlet

The stability analysis of rolling motion of hypersonic vehicles and its validations

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Science China(Physics,Mechanics & Astronomy) 2014年第12期57卷 2194-2204页

作者： YE YouDa ZHAO ZhongLiang TIAN Hao ZHANG XianFeng State Key Laboratory of Aerodynamics China Aerodynamic Research and Development Center National Laboratory for Computational Fluid dynamics high speed institute of China Aerodynamic Research and Development Center

The stability of the rolling motion of near space hypersonic vehicles with rudder control is studied using method of qualitative analysis of nonlinear differential equations, and the stability criteria of the deflected rolling motions are improved. The out- comes can serve as the basis for further study regarding the influence of pitching and lateral motion on the stability of rolling motion. To validate the theoretical results, numerical simulations were do^e for the rolling motion of two hypersonic vehicles with typical configurations. Also, wind tunnel experiments for four aircraft models with typical configurations have been done. The results show that： 1） there exist two dynamic patterns of the rolling motion under statically stable condition. The first one is point attractor, for which the motion of aircraft returns to the original state. The second is periodic attractor, for which the aircraft rolls periodically. 2） Under statically unstable condition, there exist three dynamic patterns of rolling motion, namely, the point attractor, periodic attractor around deflected state of rolling motion, and double periodic attractors or chaotic attrac- tors.

关键词： rolling motion stability criterion numerical simulation wind tunnel experiment

Flash X-ray cinematography analysis of dwell and penetration of smallcaliber projectiles with three types of SiC ceramics

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Defence Technology（防务技术） 2016年第3期12卷 277-283页

作者： Elmar STRASSBURGER Steffen BAUER Steffen WEBER Heiner GEDON fraunhofer institute for high-speed dynamics Ernst-Mach-Institute(EMI)Am Christianswuhr 279400 KandernGermany DLR–German Aerospace Center Institute of Structures and DesignPfaffenwaldring 38-4070569 StuttgartGermany WIWeB–Bundeswehr Research institute for Materials Fuels and LubricantsInstitutsweg 185435 ErdingGermany

In order to improve the performance of ceramic composite armor it is essential to know the mechanisms during each phase of the projectile–target interaction and their influence on the penetration *** the view on the crater zone and the tip of a projectile penetrating a ceramic is rapidly getting obscured by damaged material,a flash X-ray technique has to be applied in order to visualize projectile *** this purpose,usually several flash X-ray tubes are arranged around the target and the radiographs are recorded on *** EMI a flash X-ray imaging method has been developed,which provides up to eight flash radiographs in one experiment.A multi-anode 450 k V flash X-ray tube is utilized with this *** radiation transmitted through the target is then detected on a fluorescent *** fluorescent screen converts the radiograph into an image in the visible wavelength range,which is photographed by means of a high-speed *** technique has been applied to visualize and analyze the penetration of 7.62 mm AP projectiles into three different types of Si C *** commercial Si C grades and MICASIC(Metal Infiltrated Carbon derived Si C),a C-Si Si C ceramic developed by DLR,have been *** influences,not only of the ceramic but also the backing material,on dwell time and projectile erosion have been *** curves have been determined and their relevance to the ballistic resistance is discussed.

关键词： Ballistic resistance Dwell Flash X-ray cinematography SiC ceramics

Recent Progress on Aeroelasticity of high-Performance Morphing UAVs

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Computer Modeling in Engineering & Sciences 2022年第10期133卷 1-29页

作者： Binbin Lv Jun Zha Kaichun Zeng Hongtao Guo Li Yu Peng Zhang institute of high speed Aerodynamics China Aerodynamics Research and Development CenterMianyang621000China

The high-performance morphing aircraft has become a research focus all over the *** morphing aircraft,unlike regular unmanned aerial vehicles(UAVs),has more complicated aerodynamic characteristics,making itmore difficultto conduct its design,model analysis,and *** paper reviews the recent process and the current status of aeroelastic issues,numerical simulations,and wind tunnel test of morphing *** evaluation of aerodynamic characteristics,mechanism,and relevant unsteady dynamic aerodynamicmodeling throughout the morphing process are the primary technological bottlenecks formorphing *** unstable aerodynamic forces have a significant impact on the aircraft handling characteristics,control law design,and flight *** the past,the structural analysis of morphing aircrafts,flight dynamics modeling,computational mesh morphing technology,and aerodynamic calculation were performed in promoting the development of next generation UAVs,with nonlinear dynamic challenges includingtransonic aeroelastic problems and high angle of attack aeroelastic *** present,many facets of these difficulties,together with the accompanying numerical simulation studies,remain *** addition,wind tunnel experiments face significant challenges in the dynamic morphing ***,dynamic unsteady aerodynamic characteristics in the continuous morphing process still need to be verified by more related experiments.

关键词： Morphing aircraft aeroelasticity numerical simulation wind tunnel test