共查询到20条相似文献,搜索用时 93 毫秒
1.
2005年,Koflov等对滑移爆轰加载下的楔形纯铁DT-2样品进行了研究,样品仅在斜面部分发生了局部层裂,材料中明显存在不同的几个区域:材料无破坏区域、层裂开始和发展区域、加载表面-高能炸药接触面、满足α-ε相变条件的加载表面邻近区域和初始状态为硼发生高应变率变形的材料区域。但是滑移爆轰加载波系作用非常复杂,无法准确给出各区域宏细观变形破坏所对应的加载应力状态。 相似文献
2.
3.
4.
5.
采用激光位移干涉测试技术测量了AD95 陶瓷在一维应变冲击压缩下的自由面或样品/窗口界面粒子速度剖面, 确定了层裂强度及其与加载应力的变化关系, 在此基础上讨论了冲击压缩损伤程度与加载应力的关系. 研究结果表明: AD95陶瓷发生冲击压缩损伤的阈值应力约为3.7 GPa, 小于其雨贡纽弹性极限(HEL, 约5.47 GPa); 小于阈值应力不发生冲击压缩损伤, 层裂强度随加载应力的增加逐渐增大; 大于阈值应力冲击压缩损伤快速发展, 层裂强度迅速降低; 在HEL附近层裂强度降低到零, 丧失了抗拉能力, 表明材料发生了严重的冲击压缩损伤. 相似文献
6.
7.
采用激光速度干涉仪(VISAR)、X射线衍射(XRD)和扫描电镜(SEM)联合测试技术,利用等厚对称加载和逆向加载实验,研究了Fe MnNi合金的冲击相变和层裂行为。结果发现:加载压力大于6.5 GPa时,Fe MnNi合金样品发生α→ε相变;中心稀疏波的卸载作用使内压力降至4~5 GPa时,Fe MnNi合金样品发生ε→α逆相变,并伴有卸载稀疏冲击波形成。分析Fe MnNi合金样品中塑性波、相变波、稀疏波和稀疏冲击波的传播作用过程,发现加载压力大于其相变应力时,等厚对称加载下Fe MnNi合金存在产生层裂行为的物理机制。 相似文献
8.
基于相似模型试验,采用显式非线性动力分析程序LS-DYNA3D研究了地下锚固洞室在拱顶和拱腰侧两处集中装药爆源同时爆炸作用下应力波传播规律、裂纹形成机理以及洞壁围岩位移分布特征。通过对比分析顶爆试验和计算模型的压应力时程曲线,发现模拟与试验结果吻合,且符合应力波的传播规律,表明数值模拟结果可靠。爆源爆炸后,应力波以圆形向周围岩体传播,两应力波相遇处压应力强度明显大于周围岩体;当应力波传到自由面时,会反射形成拉伸波,在地表下方和洞室上方发生“层裂”现象,在拱顶和拱腰侧爆源中间沿洞室径向有裂纹延伸,由于拉伸波的叠加,在爆源下方出现“八”字形的锥形裂纹面。锚杆能够起到加固岩体的作用,锚固洞室比毛洞裂纹分布少,毛洞迎爆侧裂纹主要为横向裂纹,而锚固洞室则为径向劈裂和横向裂纹。两爆源中点洞室径向处的洞壁围岩位移峰值最大,极易产生破坏。 相似文献
9.
层裂损伤是材料动态损伤破坏研究中最重要的问题之一,其损伤特性和机制随加载应变率不同表现出明显的阶段性规律。超高应变率条件下材料层裂损伤特性、规律和机制研究已成为极端条件下材料动态响应研究的重要内容,在工程应用和基础研究领域均有重要意义。采用飞秒激光驱动冲击加载技术开展了超高应变率条件下铝材料的层裂损伤实验研究,利用啁啾频域干涉超快诊断方法对铝材料的层裂损伤过程进行了诊断,分析并获得了在109 s-1应变率条件下铝材料的层裂强度约为7 GPa,结合前人的研究数据,解读了铝材料层裂强度随应变率的变化规律。 相似文献
10.
11.
This paper reports the research results on the continuum theory of damage which goes back to the works of Kachanov, Gurson, and Rabotnov. In these models, internal variables that generally have different mathematical structure are explicitly introduced to constitutive relations. The internal variables describe a non-oriented (using scalar damage parameters) or oriented (using different-order tensors) damage distribution in the material. Then, a fracture criterion is introduced based on mechanical or thermodynamic considerations. Models of this type are still most frequently used in the structural analysis of strength of some materials (e.g., composites). Since damage nucleation and growth are closely related to strain localization, consideration is given to formulations and methods for analyzing the stability of inelastic deformation processes. Much attention is given to the effect of the finite element mesh on simulation results, to solution algorithms for such problems, and to the possibilities of using non-local constitutive models. The studies that use gradient models are also included, because damage formation is associated with sharp spatial variations of kinematic and/or dynamic characteristics which must be described by non-classical constitutive relations (gradient, non-local, micromorphic continuum). 相似文献
12.
In this paper, we will present a unified formulation of discontinuous Galerkin method (DGM) for Maxwell's equations in linear dispersive and lossy materials of Debye type and in the artificial perfectly matched layer (PML) regions. An auxiliary differential equation (ADE) method is used to handle the frequency-dependent constitutive relations with the help of auxiliary polarization currents in the computational and PML regions. The numerical flux for the dispersive lossy Maxwell's equations with the auxiliary polarization current variables is derived. Various numerical results are provided to validate the proposed formulation. 相似文献
13.
Critical impact velocity (CIV) of oxygen-free high-conductivity (OFHC) copper is experimentally measured with a novel facility in a gas gun system. The results are compared with the theoretical predictions using the typical constitutive relations, and the measured CIV value is much lower than the predictions. The difference of physical mechanisms in experiment and in theoretical calculation is discussed. It is suggested that the reduction of CIV in experiment would be related with the damage evolution in tensile copper that needs to be considered in the computation model. 相似文献
14.
15.
建立了水下障碍物的爆炸毁伤效应的物理模型和计算模型。建立了守恒方程组、混凝土的动态弹塑性本构关系和破坏准则,并确定了其在大应变、高应变率及高压条件下的的屈服准则。基于多物质流体的Euler算法,用面向对象的C++语言自行编制了NM-MMIC通用多物质二维流体弹塑性程序,对不同炸点位置、不同炸药量对轨条砦爆炸破坏过程进行数值模拟,并采用自行开发的后处理软件VISC2D实现了可视化,定量地反应了障碍物迎爆面所承受的压力变化过程,确定了轨条砦毁伤的最佳药量,并对毁伤程度进行了评价,得到了爆炸破障的毁伤规律。研究结果对设计和评价反水中障碍物的弹药具有一定的参考价值。 相似文献
16.
Vladislav BukshtynovOleg Volkov Bartosz Protas 《Physica D: Nonlinear Phenomena》2011,240(16):1228-1244
In this investigation we develop and validate a computational method for reconstructing constitutive relations based on measurement data, applicable to problems arising in nonequilibrium thermodynamics and continuum mechanics. This parameter estimation problem is solved as PDE-constrained optimization using a gradient-based technique in the optimize-then-discretize framework. The principal challenge is that the control variable (i.e., the relation characterizing the constitutive property) is not a function of the independent variables in the problem, but of the state (dependent) variable. The proposed method allows one to reconstruct a smooth constitutive relation defined over a broad range of the dependent variable. It relies on three main ingredients: a computationally friendly expression for the cost functional gradient, Sobolev gradients used in lieu of discontinuous L2 gradients, and a systematic technique for shifting the identifiability region. The performance of this approach is illustrated by the reconstruction of the temperature dependence of the thermal conductivity in a one-dimensional model problem. 相似文献
17.
18.
19.
探究岩石的受力特点及破坏特性是研究岩石地下工程安全性的关键,诸多学者都期望能在岩石本构模型的研究上取得突破性进展。在此背景下,提出了一种能够描述循环加-卸载条件下岩石的本构模型。首先,假设岩石的微元强度服从八面体剪应力理论并且微元破坏服从Weibull概率公式,将岩石本构中的损伤变量以及岩石微元强度表达式里包含的损伤因子进行本构变换,得到关于应力、应变等其他表现加-卸载下岩石损伤本构模型的参数,表示出岩石微元强度和损伤变量,再将得到的岩石微元强度和损伤变量代入所提出的岩石本构模型中,并进行等式变换得到一个函数表达式。通过将其与实验数据进行拟合对比分析,得出修正后的拟合参数,将其代入函数式中,得到损伤本构模型的修正式。最后将拟合参数进行必要的敏感性分析,得出各拟合参数的实际物理意义。 相似文献
20.