刚性钝头弹体正贯穿中厚金属靶的挤凿块速度模型

从挤凿破坏机理出发,考虑了能量守恒定律和剪切冲塞模型,提出了适用于刚性钝头弹体(平头、半球形头、球形)正贯穿中厚金属靶的挤凿块速度模型。设计了穿甲实验,以直径8 mm钨球正冲击3 mm厚GH4169靶板,得到了球形弹体相应的挤凿块数据,结合文献中平头和半球形头弹体实验数据验证了挤凿块速度模型的适用性,模型计算结果与实验数据一致性良好。提出的挤凿块速度模型可用于计算挤凿块对靶后目标的毁伤能力。     

The effect of target strength on the perforation of steel plates using three different projectile nose shapes

The effect of target strength on the perforation of steel plates is studied. Three structural steels are considered: Weldox 460 E, Weldox 700 E and Weldox 900 E. The effects of strain hardening, strain rate hardening, temperature softening and stress triaxiality on material strength and ductility are determined for these steel alloys by conducting three types of tensile tests: quasi-static tests with smooth and notched specimens, quasi-static tests at elevated temperatures and dynamic tests over a wide range of strain rates. The test data are used to determine material constants for the three different steels in a slightly modified version of the Johnson–Cook constitutive equation and fracture criterion.Using these three steel alloys, perforation tests are carried out on 12 mm-thick plates with blunt-, conical- and ogival-nosed projectiles. A compressed gas gun was used to launch projectiles within the velocity range from 150 to 350 m/s. The initial and residual velocities of the projectile were measured, while the perforation process was captured using a digital high-speed camera system. Based on the test data the ballistic limit velocity was obtained for the three steels for the different nose shapes. The experimental results indicate that for perforation with blunt projectiles the ballistic limit velocity decreases for increasing strength, while the opposite trend is found in tests with conical and ogival projectiles. The tests on Weldox 700 E and Weldox 900 E targets with conical-nosed projectiles resulted in shattering of the projectile nose tip during penetration.Finally, numerical simulations of some of the experimental tests are carried out using the non-linear finite element code LS-DYNA. It is found that the numerical code is able to describe the physical mechanisms in the perforation events with good accuracy. However, the experimental trend of a decrease in ballistic limit with an increase in target strength for blunt projectiles is not obtained with the numerical models used in this study.     

Perforation of a thick plate by rigid projectiles

Perforation of a thick plate by rigid projectiles with various geometrical characteristics is studied in the present paper. The rigid projectile is subjected to the resistant force from the surrounding medium, which is formulated by the dynamic cavity expansion theory. Two perforation mechanisms, i.e., the hole enlargement for a sharp projectile nose and the plugging formation for a blunt projectile nose, are considered in the proposed analytical model. Simple and explicit formulae are obtained to predict the ballistic limit and residual velocity for the perforation of thick metallic plates, which agree with available experimental results with satisfactory accuracy.     

On the influence of constitutive relation in projectile impact of steel plates

In this paper the influence of constitutive relation has been studied in numerical simulations of the perforation of 12-mm thick Weldox 460 E steel plates impacted by blunt-nosed projectiles in the sub-ordinance velocity regime. A modified version of the well-known and much used constitutive relation proposed by Johnson-Cook and both the bcc- and hcp-version of the Zerilli-Armstrong constitutive relation were combined with the Johnson-Cook fracture criterion. These models were implemented as user-defined material models in the non-linear finite element code LS-DYNA. Identification procedures have been proposed, and the different models were calibrated and validated for the target material using available experimental data obtained from tensile tests where the effects of strain rate, temperature and stress triaxiality were taken into account. Perforation tests carried out in a compressed gas gun on 12-mm-thick circular Weldox 460 E steel plates were then used as base in a validation study of plate perforation using LS-DYNA and the proposed constitutive relations. The numerical study indicated that the physical mechanisms during perforation can be qualitatively well predicted by all constitutive relations, but quantitatively more severe differences appear. The reasons for this are discussed in some detail. It was concluded that for practical applications, the Johnson-Cook constitutive relation and fracture criterion seems to be a good choice for this particular problem and excellent agreement with the experimental results of projectile impact on steel plates were obtained under the conditions investigated.     

Direct force measurement in normal and oblique impact of plates by projectiles

An experimental investigation of the forces produced by the penetration and perforation of thin aluminum and steel plates by cylindro-conical and hemispherically-tipped projectiles at 0, 15, 30 and 45° angles of incidence has been performed. Additionally, force histories were recorded for normal impact on Lexan, nylon and ceramic targets by conically-tipped strikers. Similar tests on Kevlar were not successful owing to the generation of voltages by rubbing of fibers that completely overwhelmed the transducer signal. A piezoelectric crystal bonded to the tail of the 12.7 mm diameter, 30 g projectiles followed by an inertial mass and a trailing wire provided the instrumentation. The strikers were propelled by means of a pneumatic gun at velocities ranging from 45 to 170 ms⁻¹. Displacement data obtained from high-speed photography for selected runs allowed curve fits to an analytical function which were compared to the directly recorded force histories.The effects of changes in initial velocity, angle of obliquity and striker tip on the peak force have been analyzed. A simple model has been developed for the perforation of plates by hemispherically-tipped projectiles at oblique incidence, and comparisons have been made with the measured force histories. A model was also devised to predict the peak forces obtained for oblique impact by cylindro-conical projectiles. The peak forces obtained experimentally were found to be relatively independent of the initial projectile velocity for shots where perforation occured. For the tests at speeds below the ballistic limit, the maximum forces were approximately proportional to the initial velocity.     

Ballistic Limit of Single and Layered Aluminium Plates

Abstract: This paper presents an experimental and finite‐element investigation of ballistic limit of thin single and layered aluminium target plates. Blunt‐, ogive‐ and hemispherical‐nosed steel projectiles of 19 mm diameter were impacted on single and layered aluminium target plates of thicknesses 0.5, 0.71, 1.0, 1.5, 2.0, 2.5 and 3 mm with the help of a pressure gun to obtain the ballistic limit in each case. The ballistic limit of target plate was found to be considerably affected by the projectile nose shape. Thin monolithic target plates as well as layered in‐contact plates offered lowest ballistic resistance against the impact of ogive‐nosed projectiles. Thicker monolithic plates on the other hand, offered lowest resistance against the impact of blunt‐nosed projectiles. The ballistic resistance of the layered targets decreased with increase in the number of layers for constant overall target thickness. Axi‐symmetric numerical simulations were performed with ABAQUS/Explicit to compare the numerical predictions with experiments. 3D numerical simulations were also performed for single plate of 1.0 mm thickness and two layered plate of 0.5 mm thickness impacted by blunt‐, ogive‐ and hemispherical‐nosed projectiles. Good agreement was found between the numerical simulations and experiments. 3D numerical simulations accurately predicted the failure mode of target plates.     

Perforation equations for conical and ogival nose rigid projectiles into aluminum target plates

We developed closed-form perforation equations for rigid, conical and ogival nose projectiles that perforate aluminum target plates at normal impact. An existing cylindrical, cavity-expansion model that was experimentally verified with perforation data into 5083-H131 aluminum armor plates was used as the starting point for the development of the perforation equations. We identified a small parameter in those perforation equations, performed power-series expansions, and obtained closed-form, accurate perforation equations for the ballistic-limit and residual velocities. The closed-form, perforation equations are shown to be very accurate when compared with existing data for 6061-T651 and 5083-H131 aluminum target plates. Our perforation equations display clearly the dominant problem parameters.     

The ballistic performance of metal plates subjected to impact by projectiles of different strength

In this paper, the ballistic performance of monolithic, double- and three-layered steel plates impacted by projectiles of different strength is experimentally investigated by a gas gun. The ballistic limit velocity for each configuration target is obtained and compared based on the investigation of the effect of the number of layers and the strength of projectiles on the ballistic resistance. The results showed that monolithic plates had higher ballistic limit velocities than multi-layered plates for projectiles of low strength regardless their nose shape, and also the ballistic limit velocities of plates decreased with the increase of the number of layers. Moreover, monolithic plates showed greater ballistic limit velocities than multi-layered plates for ogival-nosed projectiles of high strength, and also the ballistic limit velocities of plates decreased with the increase of the number of layers. However, monolithic plates had lower ballistic limit velocities than multi-layered plates for blunt-nosed projectiles of high strength, and also the ballistic limit velocities of plates increased with the increase of the number of layers. The differences in the ballistic limit velocities between various impact conditions can be related to the transitions of perforation mechanisms and failure models of plates and projectiles.     

Projectile penetration and perforation of high performance concrete: experimental results and macroscopic modelling

Experiments and simulations of penetration and perforation of high performance concrete targets by steel projectiles have been carried out. A Doppler radar monitored the projectile pre-impact velocity history and a high-speed camera captured the projectile residual velocity. A continuum mechanical approach and the finite-element method were used for the simulations. The targets were modelled with the K&C concrete model. For perforation the computational results show acceptable agreement with the experimental results, but not for penetration. The article is concluded with suggestions on how to better model concrete material for the current application.     

Perforation of AA5083-H116 aluminium plates with conical-nose steel projectiles – Calculations

The use of aluminium alloys in lightweight protective structures is increasing. Even so, the number of experimental and computational investigations that give detailed information on such problems is limited. In an earlier paper by some of the authors, perforation experiments were performed with 15–30 mm thick AA5083-H116 aluminium plates and 20 mm diameter, 98 mm long, HRC 53 conical-nose hardened steel projectiles. In all tests, initial and residual velocities of the projectile were measured and the ballistic limit velocity of each target plate was determined. In the present paper, an analytical perforation model based on the cylindrical cavity-expansion theory has been reformulated and used to calculate the ballistic perforation resistance of the aluminium plates. In addition, non-linear finite element simulations have been carried out. The target material was modeled with the Johnson–Cook constitutive relation using 2D axisymmetric elements with adaptive rezoning. To allow ductile hole growth, a pin-hole was introduced in the target. The analytical and numerical results have been compared to the experimental findings, and good agreement was in general obtained. A parametric study was also carried out to identify the importance of the different terms of the Johnson–Cook constitutive relation on the perforation resistance of the target. The results indicate that thermal softening cannot be neglected, so an alternative procedure for identification of the material constants in the power-law constitutive relation used in the cavity-expansion theory has been proposed.     

Numerical predictions of ballistic limits for concrete slabs using a modified version of the HJC concrete model

Some modifications to the Holmquist–Johnson–Cook (HJC) model (1993) for concrete under impact loading conditions are proposed. First, the pressure-shear behaviour is enhanced by including the influence of the third deviatoric stress invariant to take into account the substantial shear strength difference between the tensile and compressive meridians. Second, the modelling of strain-rate sensitivity is slightly changed so that the strain-rate enhancement factor goes to unity for zero strain rate. Third, three damage variables describing the tensile cracking, shear cracking and pore compaction mechanisms are introduced. A critical review of the constitutive model with alternative proposals for parameter identification is given. The model parameters are obtained for two concrete qualities, and perforation of concrete slabs is considered numerically and compared with experimental results from the literature. Ballistic limit assessments with deviations under 8% when compared to the experimental results are obtained, indicating that the modified version of the HJC concrete model represents a good compromise between simplicity and accuracy for large-scale computations of concrete plates impacted by projectiles.     

Perforation of AA5083-H116 aluminium plates with conical-nose steel projectiles—experimental study

The interest regarding use of aluminium alloys in lightweight protective structures is today increasing. Even so, the number of experimental and computational investigations giving detailed information on such problems is still rather limited. In this paper, perforation experiments have been performed on AA5083-H116 aluminium plates with thicknesses varying between 15 and 30 mm impacted by 20 mm diameter, 98 mm long, HRC 53 conical-nose hardened steel projectiles. In all tests, initial and residual velocities of the projectile were measured and a digital high-speed camera system was used to photograph the penetration and perforation process. Based on these measurements, impact versus residual velocity curves of the target plates were constructed and the ballistic limit velocity of each target was obtained. An analytical perforation model from the open literature is then used to predict the ballistic limit velocity, and excellent agreement with the experimental data is found. The experimental results are finally compared to similar experiments on steel and concrete targets, and the capacity of the different materials is evaluated in relation to total weight.     

Impact Force Identification of CFRP Structures Using Experimental Transfer Matrices

This paper presents a method for identifying the location and force history of an impact force acting on CFRP structures such as laminated plates and stiffened panels. The identification method is an experimental one without using any analytical model of the structure. Here, experimental transfer matrices, which relate the impact force to the corresponding responses of PZT sensors, are used to identify the impact force. The transfer matrices are preliminarily constructed from the measured data obtained by impact tests with an impulse hammer. To identify the impact location, the arrival times of the flexural waves to the PZT sensors are used, and an analog band-pass filter is used to obtain waves with a specified frequency. The wave velocity is determined experimentally from impact test results. The present method is verified experimentally by performing impact force identification of CFRP laminated plates and CFRP stiffened panels. The results reveal that the location and force history of the impact force can be identified accurately and rapidly using the present method.     

基于人工神经网络的多处损伤加筋板剩余强度预测

用BP神经网络算法对多处损伤加筋板的剩余强度数据进行训练学习,将预测值和3种经典分析方法的计算值与实验值进行对比,结果表明,ANN法预测值与实验值吻合得最好,LMC修正法和WSU3修正法次之,Swift塑性区连通法最差。最后用所建立的BP网络对不同主裂纹半长和韧带长度的剩余强度进行了预测,结果发现,在其他参数不变的情况下,不管是双筋条还是三筋条加筋板,剩余强度总是随主裂纹半长的增加而成线性降低,随韧带长度的增加而成线性增加,但双筋条加筋板比三筋条加筋板对主裂纹半长和韧带长度的变化更加敏感。     

水下爆炸载荷作用下加筋板变形及开裂试验研究

为了解加筋板结构在水下爆炸载荷作用下的变形模式,以及为数值仿真计算提供材料的开裂判据,通过试验研究,给出了加筋板的两种不同塑性变形模式.通过测量试验后加筋板裂纹的减薄率,利用体积等效原理确定了Q235钢在加筋板边界拉伸撕裂破坏模式中的开裂极限应变值,为结构在爆炸冲击作用下破损的数值仿真奠定了基础.     

卵形弹丸撞击下 FRP层合板的侵彻和穿透

研究了卵形弹丸撞击下FRP层合板的侵彻和穿透性能, 在局部化破坏模式假定的基础上改进了Wen提出的能量简化分析模型。改进模型仍假设弹体在侵彻过程中表面所受靶体的平均压力由靶体材料弹塑性变形所引起的静态阻力和速度效应引起的动阻力两部分组成, 认为侵彻过程中靶体对弹的阻力不再是一个常数, 而是与侵彻速度相关的函数。同时针对不同厚度靶板的破坏模式, 建立了几种不同的侵彻和穿透模型。通过弹头长度与靶板厚度的比较, 将侵彻过程分为部分侵彻和完全侵彻; 穿透过程分为薄板穿透和中厚板穿透。并且根据不同的破坏方式给出了求解卵形弹丸的侵彻深度、 残余速度和极限速度的预测公式。模型预测与实验数据进行了比较, 发现侵彻深度和弹道极限速度的理论预测值与实验数据吻合得很好。      

Buckling analysis of corrugated plates using a mesh-free Galerkin method based on the first-order shear deformation theory

This paper deals with elastic buckling analysis of stiffened and un-stiffened corrugated plates via a mesh-free Galerkin method based on the first-order shear deformation theory (FSDT). The corrugated plates are approximated by orthotropic plates of uniform thickness that have different elastic properties along the two perpendicular directions of the plates. The key to the approximation is that the equivalaent elastic properties of the orthotropic plates are derived by applying constant curvature conditions to the corrugated sheet. The stiffened corrugated plates are analyzed as stiffened orthotropic plates. The stiffeners are modelled as beams. The stiffness matrix of the stiffened corrugated plate is obtained by superimposing the strain energy of the equivalent orthotropic plate and the beams after implementing the displacement compatibility conditions between the plate and the beams. The mesh free characteristic of the proposed method guarantee that the stiffeners can be placed anywhere on the plate, and that remeshing is avoided when the stiffener positions change. A few selected examples are studied to demonstrate the accuracy and convergence of the proposed method. The results obtained for these examples, when possible, are compared with the ANSYS solutions or other available solutions in literature. Good agreement is evident for all cases. Some new results for both trapezoidally and sinusoidally corrugated plates are then reported.     

Impact loading of plates and shells by free-flying projectiles: A review

This paper reviews recent research into the penetration and perforation of plates and cylinders by free-flying projectiles travelling at sub-ordnance velocities. It is shown that over the last few years there has been a significant amount of experimental research into a wide range of projectile-target configurations. Although most of this research has been concerned with the normal impact of monolithic metallic plates by non-deformable projectiles, valuable work has also been carried out on non-normal impact, impact by deformable projectiles, impact of non-homogeneous metallic and non-metallic targets (including laminated targets) and impact of pipes and tubes.Recent analytical developments that enable the important characteristics of the penetration and perforation process to be modelled are reviewed. These include models that predict local deformations and failure, global deformations or both. It is shown that for some impact situations fairly simple analytical models are capable of predicting target response reasonably accurately, but for others, particularly when both local and global mechanisms contribute significantly to overall target response, more complicated models are required. The development of numerical codes that predict target response to projectile impact is briefly reviewed and the capabilities and limitations of current codes are discussed. The review also includes a section on the impact of soils and reinforced concrete structures.     

Effect of projectile nose shape,impact velocity and target thickness on the deformation behavior of layered plates

The present study is based on the experimental and numerical investigations of deformation behavior of layered aluminum plates of different thicknesses under the impact of flat, ogive and hemispherical nosed steel projectiles. Thin-layered plates arranged in various combinations were normally impacted at different velocities with the help of a pneumatic gun. Ballistic limit velocity and the residual velocity of the projectiles for each layered combination were obtained experimentally as well as from the finite element code, and these were compared with those of the single plates of equivalent thicknesses. For two layers, the residual velocity was comparable to that of the single plate, however, when the number of layers was increased the velocity drop was found to be higher in the case of the single plate. Ogive nosed projectile was found to be the most efficient penetrator of the layered target. Hemispherical nosed projectile required maximum energy for perforation. Deformation profiles of the target plates in the layered combinations were measured, and it was found that hemispherical nosed projectile caused highest plastic deformation of target plates. Numerical simulation of the problem was carried out using finite element code ABAQUS. Explicit solution technique of the code was used to analyze the perforation phenomenon. Results of the finite element analysis were compared with experiments and a good agreement between the two was found.     

Effect of projectile hardness on deformation and fracture behavior in the Taylor impact test

The ballistic perforation performance of a kinetic energy projectile would be much more influenced by the projectile’s deformation during the impact process. A projectile may suffer from large deformation and even fracture as more and more advanced materials are used as resistant components. A comparison investigation was presented in this study concerning the deformation and fracture behavior of kinetic energy projectiles manufactured from 38CrSi steel of two different hardness values. Flat-nosed projectiles were fired in a two-stage compressed gun test facility against hard steel plates within the velocity range of 200–600 m/s. The impact process was monitored by a high-speed camera. Experimental results showed that, for the soft projectiles there are three deformation and fracture modes, i.e., mushrooming, shear cracking and petalling, and that for the hard projectiles there are also three modes, mushrooming, shearing cracking and fragmentation.