高能激光武器毁伤机理多物理场建模

高能激光武器毁伤机理的研究是对其毁伤效果进行评估的基础。基于高能激光武器的毁伤机理,对激光热破坏、力学破坏以及辐射破坏的破坏原理及效果进行分析。考虑激光辐照下不同材料表面状态的变化建立稳态与非稳态两种模型,考虑切向气流的影响开展数值仿真。此外对激光辐照能量的利用效率进行了讨论,对比了不同材料对激光的防护效果。研究结果可为激光毁伤评估提供理论依据。     

激光辐照材料烧蚀特性的数值仿真

高功率激光辐照材料所造成的毁伤主要包括热破坏、力学破坏以及辐射破坏3个方面,直接表征烧蚀特性的参数是激光对材料造成的热力效应。根据机载激光武器系统ABL的性能指标与毁伤模式,构建ABL仿真系统设计框架与算法流程,建立相应的数学物理模型,采用离散化方法求解热传导方程,得到表征激光毁伤能力的关键参数。模拟了不同工况下材料的毁伤发生概率,并分析影响毁伤概率的因素。     

激光辐照材料烧蚀特性的数值仿真

高功率激光辐照材料所造成的毁伤主要包括热破坏、力学破坏以及辐射破坏3个方面,直接表征烧蚀特性的参数是激光对材料造成的热力效应。根据机载激光武器系统ABL的性能指标与毁伤模式,构建ABL仿真系统设计框架与算法流程,建立相应的数学物理模型,采用离散化方法求解热传导方程,得到表征激光毁伤能力的关键参数。模拟了不同工况下材料的毁伤发生概率,并分析影响毁伤概率的因素。     

智能化高能激光防护材料新进展

激光技术的不断进步,尤其是其在军事领域的实战化应用,使得针对高能激光的防护要求不断提高。本文首先介绍了高能激光武器在未来战争中的重要地位,总结分析了激光隐身和高能激光防护材料的研究进展,提出兼具激光隐身和防护功能的智能化激光隐身材料是未来激光防护材料的发展趋势和方向。之后,详细阐述了智能化激光防护材料的防护思路,并按防护机理梳理了现阶段具有智能化激光防护特征的材料体系和防护结构,分别分析了其优缺点及发展方向。目前智能化激光防护材料的研究尚在起步阶段,尚未能有一种已知材料体系可以满足激光隐身和高能激光防护兼容的需求,针对新材料的开发刻不容缓。因此,本文对智能化激光防护材料的发展趋势也进行了预测和探讨。     

水中爆炸作用机理及毁伤效应研究综述

为深入揭示水中爆炸的作用机理及毁伤效应特性,从不同炸药水中爆炸机理、水中爆炸冲击波传播、水中爆炸气泡脉动、水中爆炸结构破坏效应与动态响应、水中爆炸测试试验技术、水中爆炸数值模拟与毁伤评估等6个方面,综述了国内外对水中爆炸作用机理及毁伤效应的研究进展。提出急需解决的关键技术问题为:非理想炸药水中爆炸能量释放与传播、冲击波/气泡耦合作用对结构的毁伤、水中爆炸结构毁伤评估方法、水中爆炸多尺度模拟技术等。附参考文献86篇。     

碳纤维/环氧树脂复合材料层板连续激光烧蚀试验研究

进行不同热流密度及辐射时间下碳纤维/环氧叠层复合材料激光辐照试验,获得温度分布和烧蚀特性,并对激光烧蚀后试件扫描电镜测试分析,从微观角度进行分析,获得碳纤维壳体激光破坏模式;热失重测试分析,获得热分解规律,研究烧蚀特性和烧蚀机理,为热分析计算提供试验依据。     

辐照对橡胶老化作用的研究

在核能、航空航天、电离辐射等高能粒子辐照领域,辐照是引起橡胶性能降低的主要因素之一。介绍辐照对橡胶的损伤机理、不同射线粒子辐照对橡胶性能的影响,分析橡胶耐辐照性能的评估指标和几种常见橡胶的耐辐照性能,提出橡胶耐辐照性能的改进方法。辐照对橡胶的老化损伤主要是因为橡胶分子链吸收一定量的辐照能而断裂,生成大量自由基,进行不同程度的降解和交联反应,进而改变了橡胶的化学、机械及电气性能。不同辐射源对橡胶的老化作用差异较大,目前没有一种橡胶可完全满足各种工况环境的使用要求,在实际使用工况下应选择合理的性能指标来评估橡胶经辐照后的性能稳定性。除了选用耐辐照橡胶之外,还可以通过添加填料、抗辐射树脂或有机抗辐射剂等方式进一步改善橡胶制品的耐辐照性能,拓宽橡胶制品应用范围。     

加速器电子束辐照技术在污水处理中的应用

对电子束辐照技术的机理、辐照加速器装置及电子束辐照技术在污水处理中的研究应用现状进行了总结介绍,并对加速器电子束辐照技术的优缺点进行了分析。高能电子束的可控性能好,反应速率快,技术相对成熟,应用范围广,且不产生二次污染,特别是对一般技术难以降解处理的有毒物质,具有较好的技术和经济可行性。最后对加速器电子束辐照技术的大规模应用前景和研究重点进行了展望。     

激光切割陶瓷加工过程的数值模拟研究

激光与材料的相互作用一直是备受人们关注的问题。从工业上的激光热处理技术,到军事上的激光破坏机理研究,均与之密切相关,它在激光加工应用等领域中的诱人前景,激励着这方面的研究工作不断前进。笔者利用有限元理论,对不同模式激光加热Al_2O_3陶瓷的热传导过程及热应力分布进行了数值模拟,得到了Al_2O_3陶瓷的温度场和热应力场分布。根据热传导方程和热应力方程,建立了不同模式的激光辐照下中瞬态温度场和热应力场的物理模型。模拟计算了Al_2O_3陶瓷在不同模式激光照射下的温度场。数值模拟结果表明:吸收的激光能量主要分布在光斑半径以内,因此随着加热时间增加形成的径向温度梯度也越大;陶瓷内部沿轴向不同深度各点的温度随时间增长曲线在加热初始阶段均为S型。笔者的研究结果可为激光切割陶瓷加工过程的数值模拟研究提供参考。     

碳酸钙分散效果对LLDPE/CaCO_3复合材料流变行为的影响

填料分散效果对填充共混物的流变行为产生直接的影响。主要研究碳酸钙(CaCO3)颗粒在线性低密度聚乙烯(LLDPE)中的分散形态对材料稳态流变性能和动态流变性能的影响,通过选择合适的流变模型对稳态黏度曲线进行拟合,结合对热性能的研究对填料分散相形态对流变特性的关系和作用机理进行阐述,目的是通过流变方程中相关参数的变化来描述填料在聚合物基体中不同的分散效果,为建立基于流变测试的填料分散性的评估模型提供理论依据。     

Key technologies for laser-assisted precision grinding of 3D C/C-SiC composites

Due to their exceptional and distinctive qualities, 3D C/C-SiC composites are widely utilized in producing high-end equipment and the aerospace national defense industries. However, the hard and pseudo plastic nature of the material and its anisotropies make it challenging to process. To improve the processing quality of 3D C/C-SiC composites, laser-assisted precision grinding technology is introduced in this paper, which innovatively controls the depth of the thermally induced damage layer by adjusting the laser process parameters to reduce the hard brittleness of the material, and then the surface is created by precision grinding with a grinding wheel on this basis. Experiments on laser-induced damage, laser-assisted grinding, and diamond scratching were carried out to investigate the effect of laser parameters on material damage and the effect of laser-assisted grinding processes, with an emphasis on revealing the mechanism of material removal. The results show that laser irradiation causes complex reactions such as sublimation, decomposition, and oxidation of 3D C/C-SiC composites, resulting in SiO2 and Si and recondensed SiC, causing surface/subsurface damage. A maximum reduction in normal grinding force, tangential grinding force, specific grinding energy, and surface roughness of 35.6%, 43.6%, 43.58%, and 24.22%, respectively, compared to conventional grinding processes with laser-assisted grinding. After laser irradiation, the degree of brittle fracture in the precision grinding of workpieces is significantly reduced due to the degradation of matrix and fiber damage caused by laser irradiation, which reduces the hard and pseudo plastic properties of the material. The removal mechanism shows a trend of ductile domain removal in the grinding of thermally damaged layers, which reduces the grinding force and improves the surface quality.     

Surface damage and threshold determination of Ge–As–Se glasses in femtosecond pulsed laser micromachining

Ge–As–Se chalcogenide glasses were prepared and the surface damage characteristics under femtosecond laser irradiation were experimentally investigated. Femtosecond laser beams with different power intensities, focusing depths, pulse repetition rates, and pulse numbers were employed to determine the damage thresholds of the samples. The surface morphologies and feature sizes of the damage craters were studied with regard to laser energy density to evaluate the damage circumstances of the glasses. The generation of the surface damage was also recorded by using different numbers of pulses. Results showed that the damage area increased monotonically with the laser power at low energy density and tended to saturation when reaching a critical value. According to the linear circumstances of laser energy density on the damage crater area, the average damage thresholds of the Ge–As–Se glasses with different repetition rates and pulse numbers were obtained. Results showed that the damage threshold decreased with the increase in pulse repetition rate and number of pulse.     

Surface modification of sintered magnesium oxide (MgO) with chromium oxide (Cr2O3) by pulsed laser irradiation in air and liquids

Surface modification of ceramic materials by laser irradiation is widely used as a non-contact, fast and thermally activated process to generate micro and nanostructures. The effects of liquids while surface modification by laser irradiation of ceramic materials under liquid environment are least explored so far. This study reports the effects of pulsed laser irradiation in air and liquids on the microstructure and morphologies of ceramic materials. Chromium oxide (Cr₂O₃) was mixed in different concentrations (3, 5 and 7% in weight) into magnesium oxide (MgO) matrix and was sintered at 1650 °C. The structure and morphology of the sintered ceramic pellets were characterized using X-ray diffraction and scanning electron microscopy. Presence of the spinel magnesium chromium oxide (MgCr₂O₄) was identified in these samples. For surface modification of these samples, laser irradiation is carried out in air and liquids (methanol, isopropyl alcohol and acetone) using 2 ns pulsed lasers (532 nm) of different pulse repetition rates and energies. The microstructure and morphologies of the samples after irradiation was analyzed and their crystalline structure and composition were maintained after laser irradiation. It was observed that the surface morphologies of the ceramic pellets were modified by laser irradiation as a combined effect of the medium (air/liquids), energy fluence and the concentration of the Cr₂O₃ in MgO. Our results show that pulsed laser irradiation especially in liquids is an effective technique for modifying surface morphology of ceramic materials.     

Study on ablation behavior and mechanism of C/SiC composite irradiated by a laser with various parameters

C/SiC composite has been widely used as a high-temperature material for engineering components due to its excellent thermal properties. Facing the rapid development and threat of high-energy laser, study on the ablation resistance under laser irradiation is strongly required. In this work, a continuous high-energy laser was applied to explore the laser ablation behavior and mechanism of C/SiC composite. From the results, C/SiC composite shows different morphologies when irradiated at various laser power densities for 500 and 700 W/cm². We divided the ablation area into three regions; the central, transition, and edge regions, where the formation of SiO₂, SiO, and the breakage of carbon fiber were observed. The generated highly reflective SiO₂ layer reduces the absorption of laser energy, which is beneficial to lower the back-surface temperature and reduce the damage of composite. In addition, we put forward the ablation physical models and ablation mechanisms irradiated at different power densities. The work provides a basis for the laser ablation resistance of C/SiC composites under different conditions.     

Optical and thermal insulation properties of silica aerogel under a 7 kW·cm-2 power laser irradiation

Laser technology has made great progress over the past decades. However, corresponding defense systems have lagged slightly behind. Therefore, there is significant room for research with respect to the principles and bases of existing laser protective materials. In this paper, a kind of silica aerogel material is prepared with the acid-base sol-gel process. Considering the influence of thermal conductivity and the porosity of the aerogel materials on the laser irradiation results, the best laser resistance times of the materials were obtained. The concept of the maximum energy transfer radius is proposed to build a preliminary laser irradiation model for porous materials. It indicates that under the irradiation of a continuous wave laser with a power of 7 kW·cm^?2, the silica aerogel materials with the thickness of 3, 6, and 9 mm can withstand the laser for maximum times of 26, 61, and 100 s, respectively. After 7 s of irradiation, the surface temperature of 3 mm from the laser incident point is 226.9 °C. Aerogels, especially silica aerogels, should be considered as future laser protection materials. The extremely low thermal conductivity and the strong scattered ability for laser of these materials will provide a good defensive effect against large-energy laser weapons.     

The effects of excimer laser irradiation at 248 nm on the surface mass loss and thermal properties of PS,ABS, PA6, and PC polymers

Excimer laser irradiation provides a new and important method for polymer surface treatment. In this work, the weight loss of engineering polymers PC, ABS, PS, and nylon 6 were investigated following irradiation by KrF excimer laser. The experimental results revealed that the polymeric weight loss is nonlinearly related to the laser energy and laser frequency for most of the materials tested. The effects of laser irradiation on the thermal properties (T_g or T_m) of the polymers were investigated using DSC. It was found that the T_g and T_m of these materials decreased as a result of laser treatment, indicating the degradation effect of the laser irradiation procedure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1024–1037, 2006     

Assessment of ablation damage on quartz ceramics through experiment and 3D modelling considering a dynamic heat source

The effects of irradiation time (IT), laser power (LP), and spot diameter (SD) on the damage caused to quartz ceramics under continuous-wave laser irradiation were investigated through an orthogonal experiment. The experimental results show that the LP has the dominant effect on the depth of an ablation pit, while the SD has the greatest impact on the diameter of the ablation centre. The diameter and depth of the ablation pit were both positively correlated to the irradiation energy. The bubbles and molten silica transition layer affected the laser beam's reflection and transmission properties, leading to the incident laser beam scattering into the entire ablation pit and forming an elliptical ablation pit. Furthermore, a 3D finite element (FE) model considering a dynamic heat source was developed to simulate the laser damage process. The shape and dimension of the ablation pit predicted by the FE model were consistent with those obtained through the experiment, demonstrating the effectiveness and rationality of the model. The FE analysis results show that the different ablation rates in the radial and depth directions significantly influence the morphology of the ablation pits. The temperature gradient in the transition region increases while the thickness of the transition region decreases as the LP increases. This indicates that a large LP will lead to greater thermal stress in this area and result in more microcracks.     

Ablation behavior of C/SiC with YSZ and ZrB2 coatings under high-energy laser irradiation

Carbon fiber-reinforced silicon carbide (C/SiC) composites are important candidates for laser protection materials. In this study, ablation mechanism of C/SiC coated with ZrO₂/Mo and ZrB₂–SiC/ZrO₂/Mo under laser irradiation was studied. ZrB₂–SiC multiphase ceramic and ZrO₂ ceramic were successfully coated on C/SiC composite by atmospheric plasma spraying technology with Mo as transition layer. Phase evolution and morphology of composite were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Moreover, ablation behavior of the composite was investigated by laser confocal microscopy. Results showed that ablation mechanism of C/SiC composite was controlled by phase transformation, thermal reaction, and thermal diffusion, with solid–liquid transition of ZrB₂ and ZrO₂ being dominant factor. Endothermic reaction and good thermal diffusivity of coatings were also important factors affecting ablation performance. Reflectivity effect of ZrO₂ coating was limited under high-energy laser irradiation. Compared with ZrO₂/Mo single-phase-monolayer coating, designed ZrB₂–SiC/ZrO₂/Mo coating showed better ablation performance, and breakdown time of C/SiC increased from 10 to 40 s. The depletion of liquid phase in molten pool was identified as an important factor responsible for rapid failure of C/SiC. The coating failed when the entire liquid phase was consumed within molten pool, followed by rapid damage of C/SiC substrate. Results of this study can provide theoretical guidance and research ideas for design and application of laser protective materials.     

质子辐照对MQ硅树脂增强加成型硅橡胶力学性能的影响

采用空间综合辐照模拟设备研究了100keV和150keV能量的质子辐照对MQ硅树脂增强加成型硅橡胶力学性能的影响。结果表明,辐照后材料表面产生老化裂纹,随辐照能量、粒子注量的增加,裂纹的数量增多,裂纹增大;质子辐照对硅橡胶的力学性能影响较大,邵尔A硬度、拉伸强度和扯断伸长率随辐照粒子注量的增大先增加而后下降;小粒子注量的辐照对硅橡胶的损伤较小,以交联为主,而大粒子注量的辐照则以降解为主;高辐照能量对硅橡胶的损伤更为严重。