| 高熵合金药型罩动态性能及结构优化研究 | |
| Alternative Title | Research on dynamic performance and structure optimization of high-entropy alloy shaped charge liner |
陈健
| |
| Thesis Advisor | 戴兰宏 |
| 2022-05-29 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Subtype | 硕士 |
| Degree Discipline | 固体力学 |
| Keyword | 高熵合金 药型罩 微结构演化 有限元模拟 机器学习 |
| Abstract | 聚能装药由于其强大的侵彻性能在国防和民用领域均有广泛应用，作为聚能装药结构的核心部件，药型罩则是聚能射流成型与侵彻性能的关键。研究显示药型罩材料一般应具有高密度、高声速和良好的塑性，传统的药型罩材料大多为纯金属或以单一金属元素为主元的传统合金。随着工业技术的发展，传统药型罩材料已经难以满足相关领域对于药型罩侵彻性能的需求，亟需开发新型的药型罩材料以提升其侵彻性能。与传统的单主元合金不同，新型的高熵合金以多种金属元素为主元的设计理念使得其能够突破传统合金的性能极限，设计出具有更强侵彻性能的高熵合金药型罩。因此，本文从实验、有限元模拟以及机器学习结合等方面在高熵合金作为药型罩材料应用方面开展了一系列研究。
首先，制备了新型 CoCrNi 中熵合金药型罩，并开展了破甲实验，并对实验结束后的 CoCrNi 残余射流组织进行了一系列详细的微结构表征，分析了CoCrNi药型罩在射流成型与侵彻过程的微结构演化行为。发现 CoCrNi 射流发生了明显的动态再结晶行为，再结晶细化的晶粒为射流的大塑性变形提供了变形基础。残余射流组织材料的微结构精细表征揭示 CoCrNi 射流组织的晶界处存在大量的富Cr 元素 BCC 结构的纳米析出相，这种析出相的存在严重阻碍了射流变形过程中的晶界滑移，促进了射流组织沿晶界方向开裂，从而降低了 CoCrNi 射流塑性变形伸长的能力和射流的侵彻性能。
随后，建立了 CoCrFeMnNi 高熵合金药型罩侵彻钢靶的有限元模型，分析了高熵合金药型罩的射流成型与侵彻特性，研究了药型罩结构对于高熵合金射流成型与侵彻行为的影响。结果表明 CoCrFeMnNi 高熵合金药型罩具有良好的射流成型能力，具有较高的射流头部速度与速度梯度。适当减小药型罩的壁厚能够提高射流的头部速度与侵彻性能，若药型罩壁过薄则会导致射流离散，反而降低其侵彻能力。药型罩锥角越大，射流越短粗，射流头部速度越小，侵彻性能越差。适当增大炸高能够使射流充分伸展，从而提高其侵彻性能，但过大的炸高将导致射 流离散，降低其侵彻能力。
最后，首次提出了 CoCrFeMnNi 高熵合金药型罩结构的性能评价指标：能量转化率，用于描述药型罩结构将炸药能量转化为射流动能并用于侵彻的能力，并通过有限元模拟验证了该评价指标的有效性。之后建立利用机器学习方法建立了 多层感知机（MLP）模型，用于预测药型罩结构的能量转化率，结果表明训练后 的 MLP 模型能够很好实现该功能。进一步利用该 MLP 模型在 49776 个不同的 药型罩结构中搜索出了能量转化率优于样本集的药型罩结构，实现了药型罩结构 的优化，并且极大地减少了有限元模拟所需的计算力与时间。 本文有关高熵合金在聚能药型罩方面的研究成果为后续高性能新型的多主 元合金药型罩材料开发及相关工程应用提供了重要的设计依据和指导价值。 |
| Other Abstract | Shaped charge is widely applicated both in national defense and civilian fields for its strong penetration ability. As the core component of shaped charge, shaped charge liner is the key to the formation and penetration performance of shaped jet. Research shows that the shaped charge liner material should generally have high density, sound velocity and good plasticity. The traditional shaped charge liners are mostly made of pure metals or traditional alloys with one principal element. With the development of industrial technology, traditional shaped charge liner materials are hard to meet the relevant industry requirements for the penetration performance. It is urgent to develop new shaped charge liner materials to improve the penetration performance. Different from the traditional alloys with one principal element, the design concept of the new high-entropy alloys with multi principal elements enables it to break through the limit of traditional alloys and design high-entropy alloy shaped charge liners with stronger penetration performance. Therefore, we carried out a series of research work on the application of high-entropy alloys as shaped charge liner materials through a combination of experimentation, finite element simulation and machine learning.
First, we prepared a new CoCrNi medium-entropy alloy shaped charge liner, and carried out penetration experiments. After that, we carried out a series of detailed microstructure characterizations of the recovered residual jet, and analyzed the microstructural evolution during the jet formation and penetration process. An obvious dynamic recrystallization phenomenon was observed in residual jet, which led to a severe grain size reduction. The refined grain structures are supposed to accommodate
the large strains in the severe plastic deformation of the shaped charge jet. Furthermore, the nanosized Cr-rich precipitates with BCC structures were observed to be widely distributed along grain boundaries. The Cr-rich precipitations were considered obstacles for grain boundary movement and promotion of crack initiation along the grain boundaries, which depleted the ductility of the CoCrNi shaped charge jet and its ability to penetrate.
Subsequently, we established a finite element model of the penetration of the CoCrFeMnNi high-entropy alloy (HEA) shaped charge liner, and analyzed the jet forming and penetration performance and the effect of the shaped charge liner structure. The results show that the CoCrFeMnNi high-entropy alloy shaped charge liner has good jet forming ability with a high tip velocity and velocity gradient. Appropriately reducing the thickness of the shaped charge liner can improve the tip velocity and penetration performance of the shaped charge jet. However, if the thickness of shaped charge liner is too thin, the shaped charge jet will be scattered and its penetration ability will bereduced. The larger the cone angle of the shaped charge liner, the shorter and thicker the jet, the smaller the tip velocity, and the worse the penetration performance. Properlyincreasing the stand-off distance can fully extend the jet and improve the penetrationability, but an excessively large stand-off distance will lead to the dispersion of the jet and reduce the penetration ability.
Finally, for the first time, we put forward the performance evaluation index of the CoCrFeMnNi high-entropy alloy shaped charge liner structure: the energy conversion rate, which is used to characterize the ability of the shaped charge liner structure to convert explosive energy into jet kinetic energy for penetration. The validity of the evaluation index is verified. After that, we established a multi-layer perceptron (MLP) model using machine learning methods to predict the energy conversion rate of the shaped charge liner structure. The results show that the trained MLP model can achieve this function well. We further used the MLP model to search for a shaped charge liner structure with a better energy conversion rate among 49,776 different shaped charge liner structures, which achieved the optimization of the shaped charge liner structure and greatly reduced the computing resource and simulation time. The research results of applying high-entropy alloys as shaped charge liners in this paper provide important design basis and guiding value for the subsequent development of multi-principal element alloy shaped charge liners and related engineering applications. |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://dspace.imech.ac.cn/handle/311007/89127 |
| Collection | 非线性力学国家重点实验室 |
| Recommended Citation GB/T 7714 | 陈健. 高熵合金药型罩动态性能及结构优化研究[D]. 北京. 中国科学院大学,2022. |
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| 硕士毕业论文最终版-陈健.pdf（4887KB） | 学位论文 | 开放获取 | CC BY-NC-SA | Application Full Text | ||
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