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Round robin using the depth of penetration test method on an armour grade alumina

Defence Technology（防务技术） 2019年第6期15卷 829-836页

作者： Erik P.Carton Bernt B.Johnsen Dennis-Bo Rahbek Hans Broos Almar Snippe TNO P.O.Box 45NL-2280 AA Rijswijkthe Netherlands Norwegian Defence Research Establishment(FFI) P.O.Box 25NO-2027 KjellerNorway

The depth of penetration(DOP)method is a well-known ballistic test method for characterisation and ranking of ceramic armour materials.The ceramic tile is bonded to a backing material of semi-infinite thickness,and the penetration depth of the projectile gives a measure of the performance of the ceramic.There is,however,an inherent variability in the results from this test method.In this work,the accuracy and the variability of the DOP method has been investigated in a round robin exercise.Six ballistic test centres took part in the exercise.A test protocol was developed,in which the threat type(projectile and impact conditions)and a procedure on how to prepare the targets were specified.The targets consisted of alumina tiles of two different thicknesses that were bonded to polycarbonate backing cubes.Two different 7.62 mm armour piercing projectiles were employed;one with a hard steel core and one with a tungsten carbide core.The projectiles and the other materials all came from single material batches in order to avoid batch-to-batch variations in material properties.These materials were distributed between the ballistic test centres.The test results of the different ballistic test facilities were collected and compared.There was not a lot of variation between the average DOP values obtained at each laboratory,but the variation in penetration depth between shots was high.The consequence of this variation may be less confidence in the test results,and a statistical method was used to evaluate the required number of tests that are sufficient to obtain an average result with high confidence.In most cases,the required number of tests is much higher than what is practically feasible.This work was conducted as part of the European Defence Agency-project CERAMBALL.

关键词： Ballistics depth of penetration Test method Armour Ceramic Statistics

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Effect of process parameters on depth of penetration and topography of AZ91 magnesium alloy in abrasive water jet cutting

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Journal of Magnesium and Alloys 2018年第4期6卷 366-374页

作者： C A Niranjan S Srinivas M Ramachandra Department of Mechanical Engineering BMS College of EngineeringBengaluru-India

In the present study,the influence of dynamic process parameters such as water pressure,traverse speed and abrasive mass flow rate on depth of penetration and surface topography in high strength AZ91 magnesium alloy were investigated using Abrasive Water Jet(AWJ)cutting technology.Process parameters were varied at 3 levels and influences of each parameter on penetration ability were identified using analysis of variance(ANOVA).Contribution of water pressure and traverse speed on jet penetration found higher compared to abrasive mass flow rate.Profile projector was used to measure depth of penetration.Microstructural features and topography of cut surfaces were examined using Scanning Electron Microscopy(SEM).Micro cutting and ploughing were observed on the top and bottom portion of the cut which were similar to that of modes of deformation in other ductile materials like aluminium and steel.Surface roughness of cut surfaces was measured using Taylor Hobson surface roughness tester.Surface roughness found higher at higher traverse speeds and lower at lower traverse speeds.This study also highlights the suitability of AWJ cutting technology for cutting magnesium and its alloys.

关键词： AZ91 magnesium alloy depth of penetration Profile projector Topography

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Mechanical properties and impact resistance of concrete composites with hybrid steel fibers

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Frontiers of Structural and Civil Engineering 2022年第5期16卷 615-623页

作者： FatihÖZALP Halit Dilşad YILMAZ Burcu AKCAY Department of Civil Engineering Faculty of Engineering and Natural SciencesIstanbul Medeniyet Universityİstanbul 34700Turkey ISTON Istanbul Concrete Elements Factoriesİstanbul 34325Turkey Faculty of Engineering Kocaeli UniversityKocaeli 41000Turkey

The aim of this study is to develop concrete composites that are resistant to armor-piercing projectiles for defense structures.Different reinforcement configurations have been tested,such as short steel fibers,long steel fibers,and steel mesh reinforcement.Three different concrete mix designs were prepared as“Ultra High Performance(UHPFRC),High Performance(HPFRC)and Conventional(CFRC)Fiber Reinforced Concrete”.The content of hybrid steel fibers was approximately 5%in the UHPFRC and HPFRC mixtures,while the steel fiber content was approximately 2.5%in the CFRC mixture.In addition,a plain state of each mixture was produced.Mechanical properties of concrete were determined in experimental studies.In addition to the fracture energy and impact strength,two important indicators of ballistic performance of concrete are examined,which are the penetration depth and damage area.The results of the study show that the depth of penetration in UHPFRC was around 35%less than that in HPFRC.It was determined that the mixtures of UHPFRC and HPFRC containing 5%by volume of hybrid steel fibers showed superior performance(smaller crater diameter and the less projectile penetration depth)against armor-piercing projectiles in ballistic tests and could be used in defense structures.

关键词： projectile impact depth of penetration fracture energy crater diameter UHPFRC

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High-Velocity Projectile Impact Behaviour of Friction Stir Welded AA7075 Thick Plates

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Defence Technology（防务技术） 2023年第11期29卷 153-163页

作者： R.Praveen S.R.Koteswara Rao G.Selvakumar R.Damodaram Department of Robotics and Automation Karpaga Vinayaga College of Engineering and TechnologyChengalpattu603308TamilNaduIndia Department of Mechanical Engineering Sri Sivasubramaniya Nadar College of EngineeringChennai603110TamilNaduIndia

In this study, high velocity impact behaviour of friction stir welded AA7075-T651 25 mm thick plates were investigated using a 7.62 mm × 51 mm lead core and 7.62 mm × 39 mm steel core projectiles. Prior to ballistic trails, mechanical and metallurgical properties of friction stir welded AA 7075-T651 25 mm thick plates were studied. Microstructural and hardness studies revealed that friction stir welds constituted three distinct regions namely Weld Nugget(WN), Thermo-Mechanically Affected Zone(TMAZ) and Heat Affected Zone(HAZ). Base Material(BM) and all three weld regions were ballistically tested as per military standard NIJ.0108.01 using lead and steel core bullets at maximum permissible velocities of 830 ± 20 and 700 ± 30 m/s, respectively. It has been found that base material(AA7075-T651)and all three weld regions of 25 mm thick plates were able to resist perforation by both types of projectiles used. However depth of penetration has been found to increase from BM to WN, HAZ and TMAZ for both types of projectiles. In all cases steel core projectiles caused higher depth of penetration compared to those caused by lead core projectiles. TMAZs of the friction stir welds were found to be the weakest zone. The fracture that occurred in the base material was spall fragmentation indicating brittle failure, whereas all zones of friction stir welded AA7075-T651 targets with a front petalling, indicating ductile failure. The post-ballistic tested samples showed no significant change in the microstructure of the BM and WN. On the other hand, TMAZ and HAZ showed severe grain deformation in the direction of projectile penetration, and the formation of adiabatic shear bands(ASB). This work showed that 25 mm thick friction stir welded AA7075-T651 joints responded well to ballistic impact loads, making them a good choice for light combat vehicles.

关键词： Aluminum alloy Thick plate Friction stir welding Ballistic performance depth of penetration

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Failure investigation on high velocity impact deformation of boron carbide(B_(4)C) reinforced fiber metal laminates of titanium/glass fiber reinforced polymer

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Defence Technology（防务技术） 2022年第6期18卷 963-975页

作者： S.Suresh Kumar P.A.Shankar K.Lalith Kumar Department of Mechanical Engineering Sri Sivasubramaniya Nadar College of EngineeringKalavakkamChennai603110India

High velocity ballistic impact deformation behaviour of Titanium/GFRP Fiber Metal Laminates(FML)has been explored.Both single and multiple projectiles impact conditions were considered.Ti/GFRP FML targets were fabricated with addition of 5%and 10%weight percentage of boron carbide(B_(4)C)particles.Mechanical properties of Ti/GFRP FML targets were determined as per ASTM standards.High velocity ballistic experiments were conducted using Armour Piercing Projectile(APP)of diameter 7.62 mm and velocity ranging between 350 and 450 m/s.depth of penetration of the projectile into the target was measured.The deformation behaviour of Ti/GFRP targets with and without the presence of ceramic powder(B_(4)C)was investigated.“Ductile hole growth”failure mode was observed for pure GFRP target when subjected to single projectile impact whereas“plugging”failure mode was noted for Ti/GFRP targets.The presence of B_(4)C(5%by weight)particles has significantly improved the ballistic resistance of the Ti/GFRP FML target by offering frictional resistance to the projectile penetration.Further addition(10%by weight)of B_(4)C has reduced the ballistic performance due to agglomeration.None of the targets showed‘brittle cracking’or‘fragmentation’failures.When compared to the published results of Aluminium(Al 1100/GFRP and Al 6061/GFRP)FMLs,Ti/GFRP FML showed lesser DoP which increases its potential application to aerospace industry.

关键词： Ti/GFRP FML Ballistic impact Armour piercing projectile Boron carbide depth of penetration Plugging

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Finite Spherical Cavity Expansion Method for Layering Effect

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Acta Mechanica Solida Sinica 2016年第6期29卷 642-654页

作者： Xiangzhen Kong Qin Fang Hao Wu Yadong Zhang State Key Laboratory for Disaster Prevention & Mitigation of Explosion & Impact PLA University of Science & Technology

A decay function for the layering effect during the projectile penetrating into layered targets is constructed, which is obtained via the theoretical solution of a dynamically expanding layered spherical cavity with finite radius in the layered targets that are assumed to be incom- pressible Mohr-Coulomb materials. By multiplying the decay function with the semi-empirical forcing functions that account for all the constitutive behavior of the targets, the forcing functions for the layered targets are obtained. Then, the forcing functions are used to represent the targets and are applied on the projectile surface as the pressure boundary condition where the projectile is modeled by an explicit transient dynamic finite element code. This methodology is implemented into ABAQUS explicit solver via the user subroutine VDLOAD, which eliminates the need for discretizing the targets and the need for the complex contact algorithm. In order to verify the proposed layering effect model, depth-of-penetration experiments of the 37 mm hard core pro-jectile penetrating into three sets of fiber concrete and soil layered targets are conducted. The predicted depths of penetration show good agreement with the experimental data. Furthermore, the influence of layering effect on projectile trajectory during earth penetration is investigated. It is found that the layering effect should be taken into account if the final position and trajectory of the projectile are the main concern.

关键词： finite spherical cavity expansion layering effect depth of penetration projectiletrajectory

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Semi-theoretical analyses of the concrete plate perforated by a rigid projectile

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Acta Mechanica Sinica 2012年第6期28卷 1630-1643页

作者： Hao Wu Qin Fang Ya-Dong Zhang Zi-Ming Gong Institute of Structural Mechanics China Academy of Engineering Physics College of Defense Engineering PLA University of Science and Technology

Based on the three-stage perforation model, a semi-theoretical analysis is conducted for the ballistic per- formances of a rigid kinetic projectile impacting on concrete plates. By introducing the projectile resistance coefficients, dimensionless formulae are proposed for depth of penetra- tion （DOP）, perforation limit thickness, ballistic limit veloc- ity, residual velocity and perforation ratio, with the projec- tile nosed geometries and projectile-target interfacial fric- tion taken into account. Based on the proposed formula for DOP and lots of penetration tests data of normal and high strength concrete targets, a new expression is obtained for target strength parameter. By comparisons between the re- sults of the proposed formulae and existing empirical formu- lae and large amount of projectile penetration or perforation tests data for monolithic and segmented concrete targets, the validations of the proposed formulae are verified. It is found that the projectile-target interfacial friction can be neglected in the predictions of characteristic ballistic parameters. The dimensionless DOP for low-to-mid speed impacts of non-flat nosed projectiles increases almost linearly with the impact factor by a coefficient of 2/（nS）. The anti-perforation ability of the multilayered concrete plates is dependent on both the target plate thickness and the projectile impact velocity. The variation range of the perforation ratio is 1-3.5 for concrete targets.

关键词： Projectile Concrete depth of penetration Perforation limit thickness Ballistic limit velocity Resid-ual velocity

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