分段结构的钨丝/锆基非晶复合材料弹芯穿甲实验研究

为了研究不同结构和材料弹芯的侵彻能力,采用80%体积分数的钨丝/锆基非晶复合材料(钨丝直径0.3 mm)弹芯,在1450~2100 m/s速度范围内,对不同结构方案的弹芯垂直侵彻均质靶板进行了实验研究。结果表明:(1)材料的性能和结构都可以影响弹丸的侵彻效率,突破了传统认识,为复合材料杆式穿甲弹设计提供了重要依据;(2)弹芯结构不同,其侵彻深度-着靶速度变化曲线也不同,对于两段和三段结构弹芯其侵彻曲线变化是凸的,其侵彻深度峰值分别出现在着靶速度1750~1800 m/s和1850 m/s附近,最大侵彻穿深均为x=1.7L;对于未分段弹芯,其侵彻深度-速度变化曲线呈渐近线变化,在速度大于1850 m/s时接近于流体动力学极限穿甲深度L·(ρ/2p/ρt)~(1/2),约为1.5L;(3)结合单向纤维复合材料的动态破坏特点、动态裂纹传播和弹芯高速撞击的侵蚀速度特性,给出了最优分段概念,分析了(2)中发现的问题的原因,为分段弹芯结构设计提供了参考。     

钨丝直径对锆基复合非晶材料穿甲性能的影响

针对4种不同直径钨丝/锆基非晶复合材料弹芯,在(1270±40)m/s撞击速度,开展了侵彻均质半无限装甲钢板实验研究,并与普通钨合金进行了对比。研究发现,在相同的制备工艺条件下,钨丝直径对该复合材料弹芯侵彻效果影响较大,主要表现:(1)在理想侵彻的条件下,钨丝直径对该种材料的侵彻性能影响较大,弹丸侵彻深度和钨丝直径关系曲线是凸的,Φ0.7 mm钨丝方案丸侵彻深度最大,最大侵彻深度为55 mm,相对于钨合金材料威力提高了25%,其根本原因是Φ0.7 mm钨丝方案在侵彻过程中呈现与铀合金类似的绝热剪切破坏特征,弹坑底部呈现90o的自锐角。(2)钨丝直径对弹芯在高速条件下的侵彻体头部破坏形式有着重要的影响,随着钨丝直径的增加,其头部的破坏模式随直径变化存在一个从变形+劈裂+弯曲+断裂的复合破坏模式到绝热剪切破坏演变过程,然后又从绝热剪切向复合模式破坏转变。     

大长径比钨丝/锆基非晶材料穿甲实验研究

针对80% Vf钨丝/Zr38Ti17Cu10.5Co12Be22.5非晶复合材料弹芯,在1300m/s~1700m/s撞击速度区间开展了侵彻30CrMnMo钢板实验研究,并与普通钨合金进行了对比。研究发现由这种材料制成的弹芯在高速侵彻时形成完全不同于钨合金和铀合金的侵彻特性,主要表现在：(1)在高速撞击条件下,钨丝/锆基非晶复合材料弹芯先后发生非晶气化、弹芯外侧钨丝屈曲和弯曲断裂、钨丝回流现象,使弹芯在侵彻过程中保持自锐,并且其侵彻能力高于普通93钨合金;(2)从弹、靶的破坏分析可知,这种复合材料在高速侵彻过程中形成自锐的同时,由于非晶气化,一方面会造成钨丝的动态屈曲与劈裂、弹芯刚度降低、侵彻分叉,会使侵彻过程中靶板抗力不对称,产生弹道弯曲等现象,相对减弱自锐性效果;另一方面,非晶气化导致回流的钨丝在弹坑侧壁产生沟槽划痕,气化形成的高压气体作用在弹坑划痕沟槽处易形成贯穿性裂纹,利于二次杀伤。     

着靶速度和钨丝直径对钨丝/锆基非晶复合材料弹芯侵彻性能的影响

为了研究高速撞击条件下含不同直径钨丝/锆基非晶复合材料弹芯的侵彻特性,使用含有4种不同直径钨丝的复合材料弹芯在1000~1600 m/s的速度区间进行穿甲实验。研究发现:钨丝/锆基非晶复合材料弹坑直径比钨合金小10%以上,"自锐"效果明显;理想侵彻时,存在一个阈值速度,钨丝/锆基非晶复合材料弹芯在低于该速度侵彻时,其侵彻过程中的破坏模式为类似于贫铀合金的绝热剪切破坏,而高于该阈值速度时,破坏模式变成钨丝的屈曲、回流,而且该阈值速度随着复合材料中钨丝直径的增加而增加;钨丝/锆基非晶复合材料弹芯中钨丝的直径会影响其侵彻过程中的稳定性,钨丝直径越大,该复合材料弹芯在侵彻过程中越容易出现劈裂等破坏,导致弹道偏转等。     

速度和钨丝直径对钨丝/锆基非晶复合材料侵彻性能的影响

为了研究高速撞击条件下含不同直径钨丝/锆基非晶复合材料弹芯的侵彻特性,使用含有四种不同直径钨丝的复合材料弹芯在1000m/s~1600m/s的速度区间进行穿甲试验。研究发现：钨丝/锆基非晶复合材料弹坑直径比钨合金小10%以上,“自锐”效果明显;理想侵彻时,存在一个阀值速度,钨丝/锆基非晶复合材料在低于该速度侵彻时,其侵彻过程中的破坏模式为类似于贫铀合金的绝热剪切破坏,而高于该阈值速度时,破坏模式变成钨丝的屈曲、回流,而且该阀值速度随着复合材料中钨丝直径的增加而增加;钨丝/锆基非晶复合材料中钨丝的直径会影响着其侵彻过程中的稳定性,钨丝直径越大,该复合材料在侵彻过程中越容易出现劈裂等破坏,导致弹道偏转等。     

钨丝/锆基非晶复合材料长杆体弹芯穿甲实验研究

针对体积分数为80%的钨丝/Zr_(38)Ti_(17)Cu_(10.5)Co_(12)Be_(22.5)非晶复合材料长杆体弹芯,开展了在1300~1700 m/s撞击速度下侵彻30CrMnMo钢板的实验研究,并与普通钨合金弹芯进行了对比。研究发现,由这种材料制成的弹芯在高速侵彻时形成完全不同于钨合金和贫铀合金的侵彻特性,主要表现在:(1)在高速撞击条件下,钨丝/锆基非晶复合材料弹芯先后发生非晶气化、弹芯外侧钨丝屈曲和弯曲断裂、钨丝回流现象,使弹芯在侵彻过程中保持自锐,并且其侵彻能力高于普通93钨合金;(2)这种复合材料在高速侵彻过程中,由于非晶气化,一方面会造成钨丝的动态屈曲与劈裂、弹芯刚度降低、侵彻分叉,会使侵彻过程中靶板抗力不对称,产生弹道弯曲等现象,相对减弱自锐性效果;另一方面,非晶气化导致回流的钨丝在弹坑侧壁产生沟槽划痕,气化形成的高压气体作用在弹坑划痕沟槽处易形成贯穿性裂纹,利于二次杀伤。     

钨丝增强铜锌复合材料侵彻过程的数值模拟

基于Johnson-Cook模型和Gruneisen状态方程建立有限元分析模型,使用LS-DYNA软件对钨丝增强铜锌复合材料和钨镍铁合金侵彻钢靶过程开展数值模拟研究,分析2种材料在侵彻过程中各个阶段的变形,探讨钨丝本身的各向异性对侵彻性能的影响。结果表明,钨丝增强铜锌复合材料表现出明显的自锐化现象,与实验结果相符。复合材料在侵彻过程中应力主要集中在轴向的钨丝上,应力值达到2.5GPa,铜锌合金受力不足0.47GPa。该弹芯材料侵彻时的变形方式为：与靶板接触的钨丝发生弯曲,弯曲后的钨丝受力方向与轴向呈一定角度,强度和塑性明显降低。在剪切应力作用下,使材料变形区域发生破坏脱落,形成了尖锐的头部,从而表现出自锐化特征。     

钨合金杆式弹侵彻45~#钢变形失效行为的数值分析

高速撞击条件下,弹、靶材料的变形失效机制是穿甲侵彻机理研究的重要内容,利用ANSYS/LS-DYNA动力学程序对钨合金杆式弹侵彻45#钢板进行数值模拟。结果表明,撞击瞬间,强压缩冲击波沿弹芯和靶板的撞击接触面分别向弹芯和靶板内部传递,波后的等效应力超过材料的强度极限,因而发生剧烈塑性变形甚至破碎。侵彻过程中,钨合金弹芯前端3mm～4mm处热软化效应显著,应力强度发生塌陷,导致塑性变形流动而形成"蘑菇头"。45#钢的破坏方式主要是延性扩孔,对应弹、靶材料的塑性变形较均匀,整个侵彻不发生绝热剪切局部化行为。     

泡沫铝三明治结构粉末冶金法制备工艺及泡孔结构优化

粉末冶金法可实现泡沫铝三明治结构面板/芯层的冶金结合,并在制备近终型泡沫铝异型件上优势突出。基于国内研究现状,本文完善了粉末冶金法制备工艺,并优化了泡孔结构。研究发现,芯层采用AlMg4Si8铝合金成分组成,钢质面板经边缘焊接密封处理后,当芯层粉末松装密度为1.12 g/cm_³时,在1500 kN轧制压力、0.06 m/s轧制速度及55％轧制压下率下,对灌满芯层粉末的包覆面板进行450 °C热轧,获得了面板/芯层冶金结合、致密度高的发泡前驱体。另外,当发泡剂TiH₂被低熔点Sn包覆预处理后,在发泡初期分解出的H₂被液态Sn包裹,避免了在固态基体空隙间的扩散,减少了裂纹的产生,发泡前驱体在720 °C发泡300 s后可获得泡孔结构相对均匀、72.7%孔隙率的泡沫铝三明治结构。     

高临界电流密度、低损耗Cu5Ni基NbTi线材制备技术研究

重离子装置中的加速器磁体均服役在±2.25T/s的高速脉冲条件下,因此要求该种磁体所用的超导线材具有较高的临界电流和较低的损耗。针对项目需求,本文设计及制备了两种新型结构的NbTi/Cu5Ni超导线材,芯数分别为12960芯和10800芯、铜比2.0、芯丝直径均小于5 μm。系统研究了两种新型结构超导线的芯丝截面形貌、芯丝表面形貌、磁滞损耗及不同时效热处理下的临界电流密度和n值。通过优化工艺后获得了Jc(5 T、4.2 K)为2902 A/mm_²,Qh(4.2 K,± 3T)为34.2 mJ/cm_³ 的千米级NbTi/Cu5Ni超导长线,并可实现批量化生产,为重离子装置的研制提供材料基础。     

The Effect of Penetrator Geometry on the Dynamic Response of Woven Graphite/Epoxy Composites

The primary focus on this paper is to study the high energy penetration/perforation damage propagation of composite plates using the perforation split Hopkinson pressure bar. The objectives include: investigation of propagation of penetration and surface crack damage in the vicinity perforation threshold velocity; investigation of energy absorption and strain intensity profiling; and quantitative analysis of the interactive effects of penetrator geometry and sample thickness on the perforation damage of woven graphite-epoxy composite plates. The results show that strain rate increased with damage energy threshold levels and decreased with sample thickness from below to above the perforation limit velocity on the average. There was a significant difference between penetrator geometries on a specimen strain rate, and penetrator size other than shape was a more important factor. As the size of the penetrator increased, the perforation energy thresholds increased accordingly. Thus, for the same energy level, the larger penetrator delivered more energy to the target. The mode of perforation failure was localized with obliquely shaped cracks for the woven specimens. It was conceivable that the cracks first initiate at the point of intersections of the weave and move in both directions. These results would provide some instructions in building, designing, and evaluating protective structures that undergo any penetration type of impact.     

The role of microstructure in the mechanism of high velocity erosion of Cr3C2-NiCr thermal spray coatings: Part 1 — As-sprayed coatings

Carbide based thermal spray coatings are routinely applied to mitigate erosion under industrial conditions. However, the mechanism of erosion response under aggressive high velocity impact conditions remains unclear. In this work Cr₃C₂-25%NiCr thermal spray coatings were eroded at an impact velocity of 150 m/s by 20-25 µm alumina grit. Coatings were deposited by High Velocity Air Fuel (HVAF) and High Velocity Oxygen Fuel (HVOF) thermal spray techniques to generate a range of coating quality spanning that applied industrially. In Part 1 of this two-part series, the mechanism of erosion as a function of coating composition and microstructure variation is discussed. The HVOF coating underwent significant in-flight dissolution of the carbide phase. The erosion response of the supersaturated NiCr matrix was characterised by brittle cracking and fracture. The HVAF coating retained a high carbide content with minimal phase dissolution. However, the rapid solidification of the matrix material made the coating prone to brittle interphase cracking during impact. On a larger scale, splat based erosion mechanisms played a significant role, especially in the HVOF coating. The mechanisms of impact response of these coatings were dependent upon the depth of erodent penetration and could not, therefore, be extrapolated from erosion testing at lower velocities.     

C_f/SiC复合材料与钛合金Ag-Cu-Ti-C_f复合钎焊

采用Ag-Cu-Ti-Cf(Cf:碳纤维)复合钎料作中间层,在适当的工艺参数下真空钎焊Cf/SiC复合材料与钛合金,利用SEM,EDS和XRD分析接头微观组织结构,利用剪切试验检测接头力学性能.结果表明,钎焊时复合钎料中的钛与Cf/SiC复合材料反应,在Cf/SiC复合材料与连接层界面形成Ti3SiC2,Ti5Si3和少量TiC化合物的混合反应层.复合钎料中的铜与钛合金中的钛发生互扩散,在连接层与钛合金界面形成不同成分的Cu-Ti化合物过渡层.钎焊后,形成碳纤维强化的致密复合连接层.碳纤维的加入缓解了接头的残余热应力,Cf/SiC/Ag-Cu-Ti-Cf/TC4接头抗剪强度明显高于Cf/SiC/Ag-Cu-Ti/TC4接头.     

B4C-Al基复合材料对空间碎片超高速撞击的防护应用研究

为了提高航天器在应对空间碎片超高速撞击时的防护能力,采用无压预烧和真空渗铝工艺制备了B4C-Al基复合材料,并制作了B4C-Al缓冲屏的Whipple式空间碎片防护构型,利用超高速弹道靶在3~6.5 km/s的撞击速度范围内对B4C-Al缓冲屏和典型铝合金缓冲屏开展超高速撞击试验。通过比较不同撞击速度下的缓冲屏穿孔特征、后墙损伤特征、碎片云结构等,结合SEM微观损伤形貌和EDS元素分布模式分析,重点阐述了不同缓冲屏材料特性对超高速撞击碎片云形成以及后墙撞击损伤之间的作用关系。研究表明,B4C-Al缓冲屏可以更为有效地破碎超高速撞击弹丸甚至使弹丸碎片熔化,同时基体中的金属增韧相又能保证缓冲屏整体结构不发生破坏。碎片云颗粒细化以及碎片云前端动能集中效应的缓解是B4C-Al缓冲屏获得更佳防护性能的直接原因,研究结果为B4C-Al基复合材料对空间碎片超高速撞击的防护应用提供了一定的理论和技术支撑。     

Primary investigation of corrosion resistance of Ni-P/TiO2 composite film on sintered NdFeB permanent magnet

In this paper, an electroless nickel plating and sol-gel combined technique used to prepare the Ni-P/TiO₂ composite film on sintered NdFeB permanent magnet is described and the composite film was characterized by X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM), and energy dispersive X-ray spectrometer (EDX). The corrosion resistance of Ni-P/TiO₂ film was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The self-corrosion current density (i_corr) of Ni-P/TiO₂ composite film is 2.38μA/cm² in 0.5mol/L H₂SO₄ solution about 33% of that of Ni-P coating and 0.22μA/cm² in 0.5mol/L NaCl solution about 14% of that of Ni-P coating, respectively. In 0.5mol/L H₂SO₄ and 0.5mol/L NaCl solutions, the polarization resistance (Rp) of the composite film is 12.5kΩ cm² and 120kΩ cm², about 1.6 and 2 times that of Ni-P coating, respectively. The results indicate that Ni-P/TiO₂ composite film has a better corrosion resistance than Ni-P coating.     

Investigations on synthesis of HfB2 and development of a new composite with TiSi2

This paper presents the results of investigation carried out on synthesis and densification of monolithic HfB₂ and the effect of TiSi₂ as sinter additive. Pure phase HfB₂ was prepared by boron carbide reduction of HfO₂ and hot pressed to full density with the addition of TiSi₂. Isothermal oxidation study of this composite was carried out at 850 °C up to 64 h. Formation of HfB₂ was seen at 1200 °C but pure HfB₂ was formed at a much higher temperature of 1875 °C in vacuum. Hot pressing of HfB₂ at 1850 °C and 35 MPa pressure gave a compact of 80% TD. Addition of TiSi₂ helped in achieving a much higher density at a lower temperature of 1600 °C and a pressure of 20 MPa. A fully dense composite of HfB₂ and TiSi₂ was obtained with 15% TiSi₂. Hardness and fracture toughness of this composite were 27.4 ± 1.9 GPa and 6.6 ± 0.2 MPa m^1/2, respectively. Considerable deflection was observed in the crack propagation in composites. Oxidation studies indicated the formation of HfO₂, SiO₂, TiO₂ and HfSiO₄ with some glassy phase and the composite with 15% TiSi₂ was seen to be completely covered with a protective glassy layer.     

BN/Al2O3 复合粉末及其聚合物基复合材料的制备与导热性能

采用固-液相共混法制备了多种BN/Al₂O₃复合粉末,通过冻融法和表面修饰法对BN进行了改性处理,改变表面修饰剂类型和摩尔比得到了前驱体和烧结态BN/Al₂O₃复合粉末,并利用机械混合法制备了聚合物基BN/Al₂O₃复合材料,并测试分析了其导热性能。结果表明,经冻融处理的BN分散性和界面相容性明显优于未经冻融处理的BN。多巴胺对BN的改性效果优于聚乙二醇。采用多巴胺作为表面修饰剂且BN与Al(NO₃)₃的摩尔比为1:1时,能够得到纳米Al₂O₃均匀包覆的微米BN粉末,即BN/Al₂O₃微纳复合粉末,其聚合物基复合材料的导热系数可达0.62 W·m^-1·K^-1,是纯聚合物导热系数的3倍,是采用纯微米BN粉末制备的聚合物基复合材料导热系数的1.5倍。在BN表面附着的Al₂O₃可以形成层状热传导通道,能够有效提高聚合物基BN/Al₂O₃复合材料的热导率。