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Effective depth-of-penetration range due to hardness variation for different lots of nominally identical target material

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Defence Technology（防务技术） 2016年第2期12卷 171-176页

作者： Patrick FRUEH Andreas HEINE Karl Ernst WEBER Matthias WICKERT fraunhofer emi Eckerstrasse 479104 FreiburgGermany

The effect of small variations of target hardness on the depth of penetration for nominally identical target material has not been addressed systematically in publications yet and is often neglected. An investigation of this issue for laboratory-scale long rod projectiles penetrating into semi-infinite rolled-homogeneous-armor steel targets was conducted. The tungsten-heavy-alloy penetrators were of length 90 mm and diameter6 mm. Five lots of armor steel with a nominal hardness range of 280–330 BHN provided material for the targets. The pursued approach consisted of hardness testing of the targets, in total 17 ballistic experiments at velocities in between 1250 m/s and 1780 m/s and data analysis.A linear regression analysis of penetration vs. hardness shows that a target hardness increase within the given range of 280–330 BHN may result in a reduction of penetration depth of about 5.8 mm at constant velocity. This is equal to a change of-12% at an impact velocity of 1250 m/s. A multiple linear regression analysis included also the influence of yaw angle and impact velocity. It shows that small yaw angles and slight variations of impact velocities provide a smaller variation of the semi-infinite penetration depths than a variation of target hardness within a typical specification span of 50 BHN. For such a span a change in penetration of approximately-4.8 mm due to hardness variation is found, whereas 1°of yaw angle or-10 m/s of velocity variation gives a change of about-1.0 mm respectively-0.9 mm. For the given example, the overwhelming part of the variation is to be attributed to hardness effects – 4.8 mm out of 5.8 mm(83%). For nominally identical target material the target hardness thus influences the ballistic test results more severely than the typical scatter in impact conditions.

关键词：硬度变化渗透深度靶材料一元线性回归分析多元线性回归分析地段穿透深度冲击速度

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Note on:“Ballistic model for the prediction of penetration depth and residual velocity in adobe:A new interpretation of the ballistic resistance of earthen masonry”

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Defence Technology（防务技术） 2024年第1期31卷 607-609页

作者： Andreas Heine Matthias Wickert fraunhofer emi Ernst-Zermelo-Str.479104FreiburgGermany

A recently published modeling approach for the penetration into adobe and previous approaches implicitly criticized are reviewed and *** article contains a note on the paper titled“Ballistic model for the prediction of penetration depth and residual velocity in adobe:A new interpretation of the ballistic resistance of earthen masonry”(DOI:https://***/10.1016/***.2018.07.017).Reply to the Note from Li Piani et al is linked to this article.

关键词： adobe prediction earth

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Measurement of the spatial specific impulse distribution due to buried high explosive charge detonation

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Defence Technology（防务技术） 2017年第3期13卷 219-227页

作者： V. Denefeld N. Heider A. Holzwarth fraunhofer Institute for High-Speed Dynamics Ernst-Mach-Institut EMI Ernst-Mach-Institut

Buried high explosive(HE) charges represent a high threat to military vehicles. The detonation of these charges can lead to significant momentum transfer onto vehicles and their occupants. A detailed understanding of the physical processes involved in the loading of vehicle structures is necessary for an optimization of effective countermeasures and protection systems. A quantitative description of the local momentum distribution on the vehicle underbody due to the detonation process is of special importance. In the following, a new test setup is presented that allows the experimental determination of the specific impulse distribution. It is based on a ring arrangement where the elements are nested into each other and the velocity of each ring is correlated with the local specific impulse at its *** momentum transfer to a vehicle depends on a number of influencing factors such as: charge mass,embedding material(e.g. sand, gravel, clay), density, water content, saturation, depth of burial, ground clearance and vehicle shape. The presented technology is applied to quantify the influence of the embedding material(alluvial sand, quartz sand), the burial depth and the water content on the local specific impulse distribution. The obtained data can be used as initial condition for the numerical simulation of occupant safety assessment and as input for empirical modeling of momentum transfer on structures.

关键词：装药爆炸比冲军用车辆测量空间炸药车辆结构包埋材料

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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

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Dependence of impact regime boundaries on the initial temperatures of projectiles and targets

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Defence Technology（防务技术） 2024年第1期31卷 49-57页

作者： Stefano Signetti Andreas Heine fraunhofer-Institut für Kurzzeitdynamik Ernst-Mach-InstitutEMIErnst-Zermelo-Str.479104 Freiburg im BreisgauGermany

Towards higher impact velocities,ballistic events are increasingly determined by the material *** effects might range from moderate thermal softening to full phase *** particular,it is of great interest to quantify the conditions for incipient or full melting of metals during impact interactions,which result in a transition from still strength-affected to hydrodynamic material *** this work,we investigate to which extent the respective melting thresholds are also dependent on the initial,and generally elevated,temperatures of projectiles and targets before *** is studied through the application of a model developed recently by the authors to characterize the transition regime between high-velocity and hypervelocity impact,for which the melting thresholds of materials were used as the defining *** obtained results are expected to be of general interest for ballistic application cases where projectiles or targets are *** conditions might result,for example,from aerodynamic forces acting onto a projectile during atmospheric flight,explosive shapedcharge-jet formation or armor exposure to environmental *** performed analyses also broaden the scientific understanding of the relevance of temperature in penetration events,generally known since the 1960s,but often not considered thoroughly in impact studies.

关键词： Ballistic impact Thermal effects Metallic targets Energy partitioning Homologous temperature

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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

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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

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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

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Manufacturing size effect on the structural and mechanical properties of additively manufactured Ti-6Al-4V microbeams

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Journal of Materials Science & Technology 2023年第18期149卷 18-30页

作者： Kaiyang Yin Bo Cao Juraj Todt Florian Gutmann Hasan Furkan Tunçay Antonina Roth Frank Fischer Nadira Grübel Aron Pfaff Georg C.Ganzenmüller Jozef Keckes Stefan Hiermaier Christoph Eberl Department of Microsystems Engineering University of FreiburgFreiburgGermany Cluster of Excellence livMatS@FIT-Freiburg Center for Interactive Materials and Bioinspired Technologies University of FreiburgFreiburgGermany Chair of Materials Physics Montanuniversität LeobenLeobenAustria INATECH University of FreiburgFreiburgGermany fraunhofer Ernst-Mach Institut EMIFreiburgGermany fraunhofer IWM FreiburgGermany

The size effect of Ti-6Al-4V submillimeter structures manufactured by selective laser melting,which is critical for metallic mechanical metamaterials of unique mechanical properties,for example,nega-tive Poisson’s ratio and ultrahigh modulus,which show promise in biomedical,environmental,energy-related applications,has not been systematically *** here are the quantification of the porosities by X-ray microtomography scans,texture analysis,and mechanical characterization of the addi-tively manufactured Ti-6Al-4V *** found linearly decreasing porosities,increasing mechan-ical properties,and increasing texture in the microbeam with increasing diameter from 250 to 500μ*** variation of microstructure in microbeams of different diameters and along the sample height,result-ing from the printing parameters and the thermal conditions,leads to the discrepancy between the be-havior observed in experiments and finite element *** results provide the structure-property-processing correlation to improve the manufacturing and prediction of the mechanical behavior of metal-lic mechanical metamaterials.

关键词： Selected laser melting Porosity Texture Epitaxial growth Finite element modeling Metallic mechanical metamaterials

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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

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