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为了探讨岩石在爆炸载荷下的力学特性和破坏机理,采用耦合填塞装药、耦合无填塞装药和不耦合填塞结构模拟了爆炸应力波和爆生气体的不同加载强度,在石灰岩中进行模拟爆破试验,对爆炸应变波及其参数、以及爆破后岩石内部的声波速度进行了测试.基于模拟爆破试验结果,对石灰岩的力学特性和爆破损伤程度进行了分析,得到了岩石在不同爆破条件下的爆破损伤和破坏规律. 相似文献
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为了研究AD95陶瓷在冲击加载下的动态力学性能与损伤机理,采用仿真软件AUTODYN模拟了一维应力与一维应变状态下材料不同失效与破碎模式,获得了完整的损伤历程.结果表明,在一维应力波作用下,材料内部损伤以及裂纹扩展始于圆柱试样端部的应力集中,在陶瓷整体被瞬间压垮前,试样仍具有承载能力.平面冲击波作用时,试样在低于Hugoniot弹性极限下出现了两个相向传播的破坏面.由于应力波的相互作用以及材料本身抗拉强度不足,试样内同时产生了明显的层裂现象. 相似文献
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混凝土在饱水状态下冻融循环产生的破坏作用称为冻融破坏。水在混凝土毛细}L中结冰造成冻胀开裂使混凝土弹性模量、抗压强度、抗拉强度等力学性能严重下降,危害结构物的安全。一般混凝土的冻融破坏,在其表面都可以看到裂缝和剥落。本文从混凝土的相关变化以及冻融破坏产生的原因出发,分析了影响混凝土抗冻性能的种种因素,以及改善混凝土抗冻性的措施。 相似文献
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考虑材料非线性和应变率相关性等因素的影响,运用LS_DYNA非线性有限元软件对RC梁横向低速冲击试验进行了数值模拟,从动态损伤扩展、冲击能量转化等方面研究了RC梁的冲击响应过程和破坏机理。结果表明:RC梁的冲击响应过程可分为局部响应、整体响应和回弹变形三个阶段;RC梁的损伤主要发生在局部响应阶段,梁体变形主要发生在整体响应阶段;局部响应阶段的冲击力完全由梁体惯性力平衡,整体响应阶段的变形模式和截面弯矩分布与刚塑性模型基本相同;受拉钢筋变形耗能是RC梁最主要的冲击耗能机制。 相似文献
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在常规态型近场动力学理论框架下提出一种考虑孔隙作用的亚均质饱和混凝土模型。该模型体现了混凝土的细观结构非均质性,在“键”层次上将混凝土细观尺度的各相成分与宏观尺度的断裂行为联系起来,同时不增加计算量。进一步通过物质点间“键”的缺失来表征内部孔隙的存在,并分析孔隙率对混凝土力学性能的影响。最后基于两相球模型得到饱和混凝土的有效体积模量与剪切模量,建立饱和混凝土模型。基于提出的模型对饱和混凝土中的波传播问题及动态冲击破坏问题进行数值模拟,所得结果与相应试验结果吻合较好,验证了该模型和方法对研究饱和混凝土动态冲击问题的适用性。 相似文献
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本文对基桩动测中使用炮击激震对桩土系统的作用过程进行非线性动力学有限元模拟,由此通过对不同参数桩土系统在不同冲击载荷下的应力场和桩体破坏程度对炮击冲击力进行优化。 相似文献
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脉动冲击载荷对45钢磨损影响规律的试验研究 总被引:2,自引:0,他引:2
选用45钢进行了脉动冲击磨损及滑劝磨损试验,对脉动冲击磨损机理进行了初步探讨。指出,脉动冲击载荷下的磨损规律及磨损机理不同于一般的滑动磨损,脉动冲击磨损量受到硬度和载荷的交叉影响,其磨损机理主要有切屑犁沟、脆性剥落、韧性剥离及疲劳,而这几种磨损机理的存在与硬度、载荷密切相关。 相似文献
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为研究煤岩的动态破坏规律,利用Φ50 mm分离式霍普金森压杆(split Hopkinson pressure bar, SHPB)装置,开展了煤岩冲击破坏试验。基于零厚度的内聚力单元建立了煤岩有限离散元方法(finite discrete element method, FDEM),标定了模型参数;最后在LS-DYNA软件平台上模拟了SHPB冲击试验,讨论了FDEM模型在模拟动态破坏时的适用性,并对煤岩的破坏过程进行分析。研究表明:(1)煤岩动态抗压强度与应变率满足经验关系,当应变率为98.05 s-1、119.22 s-1和135.85 s-1时其动态强度因子(dynamic strength factor, DIF)分别为1.92、2.08和2.23;(2)冲击作用下煤岩的弹性变形阶段较短,塑性变形能力较强,动态弹性模量的应变率相关性不显著;(3) FDEM模型通过零厚度内聚力单元的失效能够模拟岩石类材料的脆性破坏,当网格尺寸合理时,由于惯性效应的存在,通过准静态试验标定的模型参数,也适用于冲击破坏的模拟;(4)冲... 相似文献
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Abstract: This research deals with the sensitivity of several types of performance‐designed high‐strength concrete to the loading rate. Variations in the composition of the concrete produce the desired performance, for instance having null shrinkage or being able to be pumped at elevated heights without segregation, but they also produce variations in the fracture properties that are reported in this paper. We performed tests at five loading rates spanning six orders of magnitude in the displacement rate, from 1.74 × 10?5 mm s?1 to 17.4 mm s?1. Load‐displacement curves show that their peak is higher as the displacement rate increases, whereas the corresponding displacement is almost constant. Fracture energy also increases, but only for loading rates higher than 0.01 mm s?1. We use a formula based on a cohesive law with a viscous term [Anales de Mecánica de la Fractura 25 (2008) 793–797] to study the results. The correlation of the formula to the experimental results is good and it allows us to obtain the theoretical value for the fracture energy under strictly static conditions. In addition, both the fracture energy and the characteristic length of the concretes used in the study diminish as the compressive strength of their aggregates increases. 相似文献
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Crack propagation in polymethylmethacrylate has been investigated experimentally under shock loading conditions generated by a pulse magnetic field. Using microstructural investigations, dynamic fracture surfaces of polymethylmethacrylate were analyzed and compared depending on the distance from the notch tip. A diagram of various fracture types depending on the pulse loading duration has been constructed. 相似文献
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水中冲击波对水中的构筑物具有很大破坏作用,研究水击波的特性对水中兵器、舰船等方面具有很大的军事意义,对于民用水下工程爆破的安全使用和推广也具有指导意义。采用ANSYS/LS—DYNA有限元软件建立简化的水下台阶爆破数学模型,探索和分析其在不同方向上的传播衰减特性。结果显示:水中冲击波的衰减规律具有方向性,在垂直水底方向水中冲击波压力衰减最快,其次是平行于坡顶线方向,最小抵抗线方向的水中冲击波压力衰减是最慢的。 相似文献
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A novel testing procedure for mixed mode crack propagation in concrete is presented: four point bend of notched beams under
the action of two independent force actuators. In contrast to classical procedures, this method allows nonproportional loading
and crack trajectory modifications by changing the action of one actuator. Different experimental crack trajectories, under
mixed mode and nonproportional loading, are presented together with the corresponding curves of load-CMOD and load-displacement.
The tests were performed for three homotetic specimen sizes and two mixed mode loading conditions. The results are useful
for checking the accuracy of mixed mode fracture analytical and numerical models. The models should predict the crack trajectory
and a complete group of experimental records of load and displacements on several control points in the specimen.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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We study the stress-strain state formed in a plate containing a stationary crack of finite length subjected to pulsed loading, develop a model of quasibrittle fracture caused by loads of this type, and deduce analytic expressions for the stress-strain state near the tip of the stationary crack in the plate. The proposed model admits rigorous physical justification and enables one to describe the development of brittle and quasibrittle fracture processes in materials with cracklike defects under dynamic and static loads within the framework of the same approach. The results of numerical simulation are in good qualitative agreement with the experimentally established regularities of the behavior of the critical parameters of fracture processes. 相似文献
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Atroshenko S. A. Krivosheev S. I. Petrov Yu. A. Utkin A. A. Fedorovskii G. D. 《Strength of Materials》2002,34(3):273-276
An experimental study of static and dynamic fracture properties of a spheroplastic that has a matrix of polyester resin containing a filler of glass microspheres was conducted. Crack propagation was investigated under loading conditions generated by a pulse magnetic field. Microstructure features of dynamic fracture were analyzed. 相似文献