超高速钨动能杆正撞击混凝土靶成坑规律研究

发布时间：2018-04-17 10:29

本文选题：超高速 + 混凝土本构模型　；参考：《湘潭大学》2017年硕士论文

【摘要】：在2~4 km/s速度范围内,具备一定长径比的实心金属杆(动能杆)依靠自身具有的巨大动能,以直接撞击目标的方式,在撞击过程中形成强度高、持时长、指向性强的冲击波,从而贯穿或摧毁目标并最终形成数倍弹径口径的弹坑。表面的弹坑和深层的弹洞是超高速钨动能杆正撞击混凝土的主要两种毁伤模式。但是目前对2~4 km/s速度范围内的两种毁伤模式研究较少,而成坑特性决定着辐射出来的波的基本参数,反映能量分配的份额,是揭示介质压实破碎特性、地冲击特性和毁伤机理的关键因素。因此,探究超高速动能杆撞击混凝土成坑规律是首当其冲的关键科学问题。而现有的混凝土本构均不能较好地同时模拟这两种现象。因此,针对超高速钨动能杆正撞击混凝土在数值模拟上的问题,本文完成了如下几个方面的工作:(1)在现有混凝土本构模型基础上,引入塑性功损耗定义损伤,模拟混凝土在加载过程中的软化阶段,并考虑了压缩损伤对拉伸损伤的强化效果;引入塑性体积应变,解决了等向拉伸损伤问题;考虑到不同的受力情况和动态响应下屈服面的变化,引入罗德角和应变率强化因子对其进行修正。(2)通过Fortran语言编写子程序将修正混凝土本构模型嵌入LS-DYNA有限元程序进行二次开发。采用单个单元测试了本构模型的力学性能,主要包括混凝土在外载为单轴、双轴和三轴拉压的力学行为。结果表明,本文的修正混凝土本构模型可以比较好地刻画混凝土的屈服,损伤和应变率行为。(3)利用修正混凝土动态本构模型对超高速钨动能杆正撞击混凝土的过程进行了数值模拟,很好地重现了超高速正撞击混凝土靶板后的缺陷形貌,其中包括:表面径向裂纹、环向裂纹、弹坑和层裂。分析了一系列撞击速度下,靶板弹坑直径、侵彻深度和动能杆余长随撞击速度的变化关系,模拟结果与实验吻合较好,验证了模型的合理性。通过模拟在不同撞击速度下,不同质量和不同长径比动能杆撞击混凝土靶板过程,得到成坑规律为:当采用相同动能杆撞击时,侵深随着撞击速度先增后减,弹坑直径随撞击速度的增加而增加;当采用相同横截面、不同质量的情况下,弹坑直径存在一个最大值平台,侵深却一直增加;当质量一定,横截面变化情况下,弹坑直径存在一个最大值,侵深却一直增加。研究结果可为超高速钨动能杆正撞击混凝土靶板过程的特性分析提供理论基础,为超高速动能杆设计提供参考。
[Abstract]:In the range of 2 ~ 4 km/s velocity, the solid metal rod (kinetic energy rod) with a certain aspect ratio depends on its own huge kinetic energy. In the way of directly impacting the target, the shock wave with high intensity, long duration and strong directivity is formed during the impact process.Thus penetrating or destroying the target and eventually forming multiple caliber craters.Surface craters and deep bullet holes are the two main damage modes in which the hypervelocity tungsten kinetic energy rod is striking the concrete.However, there are few studies on the two damage modes in the range of 2 ~ 4 km/s velocity, and the characteristics of the pits determine the basic parameters of the radiated waves, which reflect the share of the energy distribution and reveal the compaction and fracture characteristics of the medium.The key factors of ground impact characteristics and damage mechanism.Therefore, it is the most important scientific problem to explore the law of crater formation when hypervelocity kinetic energy rod hits concrete.However, the existing concrete constitutive models can not simulate these two phenomena well at the same time.Therefore, in order to solve the problem of direct impact of ultra-high speed tungsten kinetic energy rods on concrete, the following work has been done in this paper: 1) on the basis of existing constitutive models of concrete, plastic loss is introduced to define damage.The softening stage of concrete under loading is simulated, and the strengthening effect of compression damage on tensile damage is considered, and the problem of isotropic tensile damage is solved by introducing plastic volume strain.Taking into account the variation of the yield surface under different forces and dynamic responses,The modified concrete constitutive model is modified by introducing Luo De angle and strain rate strengthening factor. (2) the modified concrete constitutive model is embedded in the LS-DYNA finite element program for secondary development by Fortran language.The mechanical properties of the constitutive model including uniaxial biaxial and triaxial tensile and compression behaviors of concrete under external loading were tested by a single unit.The results show that the modified concrete constitutive model can describe the yield of concrete well.The damage and strain rate behavior of concrete is simulated by using the modified dynamic constitutive model of concrete.These include: surface radial cracks, toroidal cracks, craters and spallation.The relationship between the crater diameter, penetration depth and residual length of kinetic energy rod under a series of impact velocities is analyzed. The simulation results are in good agreement with the experimental results, and the rationality of the model is verified.By simulating the impact process of kinetic energy rod with different mass and ratio of length to diameter against concrete target at different impact velocities, the law of crater formation is obtained: when the same kinetic energy rod is used, the penetration depth increases first and then decreases with the impact velocity.The diameter of crater increases with the increase of impact velocity. Under the same cross section and different mass, the diameter of crater exists a maximum platform, but the depth of the crater increases. When the mass is constant, the cross-section changes.There is a maximum diameter of the crater, but the depth of the crater increases.The results can provide a theoretical basis for the analysis of the characteristics of the hypervelocity tungsten kinetic energy rod directly impacting the concrete target, and provide a reference for the design of the ultra-high velocity kinetic energy rod.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TJ01;TU528.01

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