空心弹侵彻混凝土过载特性的实验研究

通过应用弹载存储测试技术,进行了钢质空心弹在侵彻过程中弹体动态参量测试研究.测试了侵彻混凝土过程中空心弹的过载情况,真实反映了侵彻过程中复杂的断裂特征,获得了侵彻弹侵彻混凝土瞬态加速度-时间曲线以及频谱曲线.通过将实验测得的加速度时程曲线按其本身的特点划分成三个部分,每个部分代表空心弹与混凝土作用的不同阶段,分析了不同阶段空心弹与混凝土相互作用的特点,为理论模型的建立打下了基础.     

Penetration Analysis of Concrete Plate by 3D FE-SPH Adaptive Coupling Algorithm

Penetration process of concrete plate is simulated by 3D FE-SPH adaptive coupling algorithm, which is based on experimental research of projectile with 25mm diameter penetrates concrete target. In experiment, a high speed camera is used to record dynamic deformation process of concrete plate. Acceleration responses of concrete are obtained by acceleration sensor, which is pre-embedded in target plate. This experiment is also simulated by 3D FE-SPH adaptive coupling algorithm to verify the numerical model. Numerical model is approximated initially by FEM, and distorted elements are automatically converted into meshless particles to simulate damage, splash of concrete by SPH method, when equivalent plastic strain of elements reaches a specified value. Numerical results of damage process and acceleration response of concrete target are in good agreement with the experimental results. And the results show that crack propagation and lateral movement of concrete mainly occur after projectile passing through target. Furthermore, six different models with different geometry sizes are simulated by the coupling algorithm to study on the effects of boundary condition of concrete target.     

A combined experimental and numerical approach to study ballistic impact response of S2-glass fiber/toughened epoxy composite beams

A combined experimental and 3D dynamic nonlinear finite element (FE) approach was adopted to study damage in composite beams subject to ballistic impact using a high-speed gas gun. The time-histories of dynamic strains induced during impact were recorded using strain gages mounted on the front of the composite beam specimen. During ballistic impact tests, the impact velocity was also measured. The commercially available 3D dynamic nonlinear FE code, LS-DYNA, modified with a proposed user-defined nonlinear-orthotropic damage model, was then used to simulate the experimental results. In addition, LS-DYNA with the Chang–Chang linear-orthotropic damage model was also used for comparison. Good agreement between experimental and FE results was found from the comparisons of dynamic strain and damage patterns. Once the proposed nonlinear-orthotropic damage model was verified by experimental results, further FE simulations were conducted to predict the ballistic limit velocity (V₅₀) using either the number of damaged layer approach or a numerically established relation between the projectile impact velocity versus residual velocity or energy similar to the classical Lambert–Jonas equation for metals.     

Numerical Simulation of Brittle Damage in Concrete Specimens

A framework for damage mechanics of concrete is applied to simulate the nonlinear elastic deformation behavior of concrete using finite element method (FEM). A rather simple isotropic damage model containing essentially no adjustable parameters is shown to produce results in remarkably good agreement with sample experimental data: the damage law requires only the fracture energy to be defined completely. The model is achieved by introducing a damage surface that is similar to the yield function in the conventional theory of plasticity. A special form of damage surfaces is constructed to illustrate the application of the model. A new damage criterion, defined as an equivalent strain norm, is proposed, in order to take into consideration the asymmetric behavior of concrete. For verifying the FEM program including the model, deformations predicted by this model are compared with both the experimental ones for the concrete structural model and the ones calculated without application of the continuum damage mechanics.__________Translated from Problemy Prochnosti, No. 3, pp. 57 – 74, May – June, 2005.     

Deep penetration of a non-deformable projectile with different geometrical characteristics

A general non-dimensional formula based on the dynamic cavity-expansion model is proposed to predict penetration depth into several mediums subjected to a normal impact of a non-deformable projectile. The proposed formula depends on two dimensionless numbers and shows good agreement with penetration tests on metal, concrete and soil for a range of nose shapes and impact velocities. The validity of the formula requires that the penetration depth is larger than the projectile diameter and the projectile nose length while projectile remains rigid without noticeable deformation and damage.     

强冲击载荷下混凝土动态本构关系

利用一级轻气炮对混凝土靶板进行冲击压缩试验,测量出不同冲击速度下的压力-时间信号曲线。采用拉氏分析方法对实验数据进行分析,得到了流场中各力学量沿时-空的分布规律,从而得到混凝土材料应力-应变试验曲线。在试验研究及拉氏分析的基础上,分析混凝土材料在强冲击载荷下的动态本构特性。最后,结合损伤率型演化和粘弹性理论,建立了混凝土材料的损伤型粘弹性本构方程。数值拟合表明理论预示与试验吻合良好。     

单自由面混凝土介质中的深孔爆破数值分析

深孔爆破在混凝土结构物的爆破拆除中是一种常用的方法。本文基于大型非线性动力分析软件LS-DYNA,采用著名的混凝土损伤Johnson-Holmquist-Concrete模型,针对单自由面条件下混凝土介质中深孔爆破的情形,开展了大量的数值模拟;对炮孔周围的介质损伤、有效应力场、压力场、速度场以及药室的“扩孔”效应进行了比较全面的分析研究,得出的结论在工程实践中具有一定的参考价值。     

单自由面混凝土介质中的深孔爆破数值分析

深孔爆破在混凝土结构物的爆破拆除中是一种常用的方法。本文基于大型非线性动力分析软件LS-DYNA,采用著名的混凝土损伤Johnson-Holmquist-Concrete模型,针对单自由面条件下混凝土介质中深孔爆破的情形,开展了大量的数值模拟;对炮孔周围的介质损伤、有效应力场、压力场、速度场以及药室的“扩孔”效应进行了比较全面的分析研究,得出的结论在工程实践中具有一定的参考价值。     

A micromechanical constitutive model for dynamic damage and fracture of ductile materials

This paper proposes a detailed theoretical analysis of the development of dynamic damage in plate impact experiments for the case of high-purity tantalum. Our micro-mechanical model of damage is based on physical mechanisms (void nucleation and growth). The model is aimed to be general enough to be applied to a variety of ductile materials subjected to high tensile pressure loading. In this respect, the work of Czarnota et al. (J Mech Phys Solids 56:1624–1650, 2008) has been extended by introducing the concept of nucleation law and by entering a nonlinear formulation of the elastic response based on the Mie-Grüneisen equation of state. This later aspect allows us to consider high impact velocities. All model parameters are directly assessed by experimental measurements to the exception of the nucleation law which is characterized by the way of an inverse identification method using three free-surface velocity profiles (at low, intermediate and high impact velocities). It is shown that the nucleation law can be consistently determined in the range of operating pressures. The nucleation law being identified, the development of internal damage happens to be a natural outcome of the modelling. The model is applied to predict damage development and free-surface velocity profiles for various test conditions. The variety and the quality of results support the physical basis (in particular micro-inertia effects) upon which the proposed model of dynamic damage is based.     

Impact-Based Nonlinear Acoustic Testing for Characterizing Distributed Damage in Concrete

Nonlinear acoustics-based nondestructive evaluation (NDE) techniques have shown great promise for identification of microstructure and microcracking in a wide spectrum of materials (e.g., metals, metallic alloys, composites, rocks, cementitious materials). This class of NDE techniques relies on measuring nonlinearity parameters by analyzing the acoustic response of materials that are dynamically perturbed at microstrain levels (strain \(\sim \)10\(^{-6}\)–10\(^{-5})\). Using a mechanical impact to induce microstrain is advantageous for concrete testing because it allows for testing of larger concrete specimens offering potential field transportability. In this paper, two impact-based nonlinear acoustic testing techniques are compared: impact-based nonlinear resonant acoustic spectroscopy (INRAS) and dynamic acousto-elastic testing (IDAET). INRAS gives a global measure of sample hysteretic nonlinearity while IDAET provides a local but comprehensive account of nonlinear elastic properties. We discuss single- versus multi-impact INRAS and propose a physics-based model to describe the data from single-impact INRAS. Then, we introduce IDAET and demonstrate how to extract both classical and non-classical nonlinear parameters from a limited set of test results. INRAS and IDAET are used to monitor the evolution of damage in two sets of concrete samples undergoing freeze-thaw (FT) cycles. Nonlinear parameters extracted from the two tests show good agreement; all exhibiting far more sensitivity to distributed FT damage than standard (i.e. linear) resonance frequency measurements. By presenting alternative ways to collect and analyze the impact-based nonlinear acoustic test data, this study will help in broadening their use and extending their applications to quantitative in-situ evaluation.     

Multiple impact penetration of semi-infinite concrete

An experimental study was performed to gather multiple impact, projectile penetration data into concrete. A vertical firing range was developed that consisted of a 30-06 rifle barrel mounted vertically above a steel containment chamber. 0.41 m cubes of an Air Force G mix concrete were suspended in wet sand and positioned in the steel chamber. The concrete targets were subjected to repeated constant velocity impacts from 6.4 mm diameter steel projectiles with an ogive nose shape and a length to diameter ratio of 10. A laser sight was adapted to the rifle to ensure alignment, and a break screen system measured the projectile velocity. After each impact, the projectile penetration and crater formation parameters were recorded. The penetration and crater formation data were consistent with single impact penetration data from previous studies conducted at Sandia National Laboratories. In addition, an analytic/empirical study was conducted to develop a model that predicted the penetration depth of multiple impacts into concrete targets. Using the multiple impact penetration and crater formation data, a single impact penetration model, developed by Forrestal at Sandia National Laboratories, was extended to account for the degradation of the target strength with each subsequent impact. The degradation of the target was determined empirically and included in the model as a strength-modifying factor. The model requires geometry parameters of the ogive nose projectile, projectile velocity, the number of impacts, and target compressive strength to calculate the overall penetration depth of the projectile.     

脆性材料水泥砂浆多轴应力下的动态响应分析

在实际的结构应用中,混凝土类材料一般处于复杂工作应力状态,且可能承受动态荷载的作用。据此,本文采用Instron3421液压伺服试验机和具有主动围压加压装置的SHPB研究了混凝土材料-砂浆宽应变率范围多轴应力下的动态力学行为;基于Johnson-Cook强度模型框架,确定了等效强度模型的率相关参数及其他材料常数;提出了适用于描述主动围压下砂浆受冲击荷载的损伤演化规律,并确定了损伤演化常数,实验数据与理论值吻合较好     

汽车座椅聚合物泡沫座垫非线性弹性-阻尼特性建模研究

该文探讨了汽车座椅聚合物泡沫座垫的非线性弹性-阻尼特性的一种建模方法及过程。首先进行了泡沫座垫的动态力学特性实验测试,根据座垫的非线性动态特性特征选择了模型的表达式,再通过大量实验数据对其进行了参数辨识,建立了座垫的一种非线性弹性-阻尼特性数学模型,表达了座垫的动态载荷与变形位移、速度的关系。另一方面,进行了实际人体在座垫上的正常坐姿体压分布测试,参考体压分布状态进行了座垫的离散化,建立了泡沫座垫的垂向非线性弹性-阻尼特性的离散化模型,可更好地模拟座椅-乘员系统的人体角振动响应特性。最后进行了所建立的聚合物泡沫座垫动态特性模型在座椅-乘员系统多体动力学响应模拟分析中的应用验证。     

Depth of penetration of high-speed penetrator with including the effect of mass abrasion

Mass abrasion is observed on the nose of projectile when a projectile strikes concrete target at high velocity. To evaluate the influence of the mass abrasion on the depth of penetration (DOP) limit, the relationship between the nose factor of the residual projectile after abrasion and the initial impact velocity is suggested according to the experimental data. Based on the dynamic cavity expansion theory, with considering the effects of varying nose factor and mass of projectile, a modified model is proposed to calculate the depth of penetration of kinetic energy penetrator. The model predicts that a theoretical maximum DOP exists due to the mass abrasion of the projectile. The model is checked by the different experimental data.     

A fuzzy model of the penetration resistance of concrete targets

The penetration resistance of a concrete target varies greatly with the strike velocity of the projectile from low and intermediate impact velocities to high impact velocities. A fuzzy model of the penetration resistance of a concrete target is proposed to describe this characteristic. A complete analysis is conducted of the penetration process during which a rigid projectile penetrates a semi-infinite concrete target based on the proposed fuzzy model. Good agreement is observed between the experimental and predicted results based on the proposed fuzzy model.     

编织复合材料机身隔框的冲击动力学特性

为提高飞行器的适坠性能,对二维三轴编织复合材料机身隔框的冲击动力学特性进行研究。基于连续介质损伤力学建立了机身隔框在冲击载荷作用下的有限元模型。该模型根据不可逆热力学理论并结合Weibull分布建立损伤扩张准则,采用Hashin失效准则确定损伤阈值函数。在迭代过程中,剪应力与正应力相互耦合,且分别考虑材料在纵向和横向的损伤破坏。在此基础上研究了材料参数变化对机身隔框冲击动力学性能的影响,并对各种情况下的瞬态动力学特征和能量吸收特性进行对比分析。数值结果表明该有限元模型能够准确求解编织复合材料机身隔框的非线性瞬态动力学问题,载荷峰值和吸收的能量分别与试验结果相差1.5%和4.7%,且纵向的弹性模量和压缩强度等材料参数对机身隔框的冲击动力学响应影响较大。     

A wave propagation model for the high velocity impact response of a composite sandwich panel

A solution methodology to predict the residual velocity of a hemispherical-nose cylindrical projectile impacting a composite sandwich panel at high velocity is presented. The term high velocity impact is used to describe impact scenarios where the projectile perforates the panel and exits with a residual velocity. The solution is derived from a wave propagation model involving deformation and failure of facesheets, through-thickness propagation of shock waves in the core, and through-thickness core shear failure. Equations of motion for the projectile and effective masses of the facesheets and core as the shock waves travel through sandwich panel are derived using Lagrangian mechanics. The analytical approach is mechanistic involving no detail account of progressive damage due to delamination and debonding but changes in the load-bearing resistance of the sandwich panel due to failure and complete loss of resistance from the facesheets and core during projectile penetration. The predicted transient deflection and velocity of the projectile and sandwich panel compared fairly well with results from finite element analysis. Analytical predictions of the projectile residual velocities were also found to be in good agreement with experimental data.     

岩石Holmquist-Johnson-Cook模型参数的确定方法

Holmquist-Johnson-Cook(HJC)本构模型在混凝土冲击爆炸数值模拟中应用广泛, 该文将其推广到岩石类材料中, 为合理确定岩石材料的HJC本构模型参数, 从塑性屈服面理论出发, 得到了特征化黏性强度系数与帽盖模型参数的关系。基于三轴围压实验、Hugoniot实验和Hopkinson压杆实验数据, 分别得到了Salem石灰岩极限面参数、压力参数和率效应参数的取值。基于上述模型参数利用有限元程序LS-DYNA对Salem石灰岩的弹体侵彻实验进行了数值模拟, 侵彻深度的计算结果与实验数据对比表明了本文所提出的HJC本构模型参数确定方法的合理性和有效性。以相对侵彻深度为目标函数, 对Salem石灰岩HJC模型所涉及的19个参数的敏感性进行了分析, 并对一般岩石材料的HJC模型参数的确定给出了建议方法, 并通过模拟高强花岗岩和Sidewinder凝灰岩弹体侵彻实验, 进一步验证了该文提出方法的合理性。     

单层紧密排列刚玉球砼抗弹丸冲击特性分析

本文利用ANSYS／LS－DYNA有限元软件，首先对弹丸在混凝土中的侵彻过程进行了数值模拟分析，并将计算结果与经验公式给出的结果进行了对比，两者吻合较好，表明模拟计算中材料参数的选取是合理的，计算方法是正确的。在此基础上，对弹丸在单层紧密排列刚玉球混凝土中的冲击侵彻情况进行了数值计算，结果表明，刚玉球混凝土能够有效地使弹丸偏转，减小弹丸侵彻深度，降低弹丸的冲击破坏效应，与已有的试验现象和试验结果相近。