内爆压缩加载下抗氢钢圆管剪切断裂研究

 介绍了对HR-2抗氢钢圆管在内爆压缩加载过程中的剪切断裂现象的初步研究结果。利用脉冲X光动态照相观测到抗氢钢圆管在压缩过程中发生了断裂；在回收破片中存在大量典型的剪切断口，对剪切断口进行了初步宏观分析。金相细观分析观察到HR-2抗氢钢中晶粒形状沿径向的变化规律；同时观察到了裂纹尖端的绝热剪切带及带内的微孔洞。     

一维应变压缩下TC4钛合金绝热剪切研究

 利用内径为57 mm的压缩气炮，在撞击速度为0.2~1.2 km/s（相应的靶中压力为3~15 GPa）范围内进行对称碰撞实验，以研究TC4（Ti-Al6-V4）钛合金在一维应变冲击压缩条件下的绝热剪切现象。对回收得到的受冲击样品，在扫描电镜（SEM）下进行细观金相分析。结果指出，一维应变冲击压缩条件下，TC4钛合金中绝热剪切带产生的对称碰撞速度阈值为500 m/s（相当于样品中的压力为5.87 GPa）；主剪切带与冲击方向约为45°角，带上有圆形和椭圆形两种孔洞且随碰撞速度的增大而增多和长大，这是典型的韧性损伤特征。随碰撞速度增大，产生与主剪切带成15°角的支剪切带。这些与理论预言相符。X射线能谱分析结果指出，剪切带内材料发生了(α+β)→β相的转变，是典型的相变带。剪切带的温度估算与实验提供的信息吻合。     

AF1410钢的层裂断裂特性研究

 利用一级轻气炮作为加载手段，对AF1410钢的层裂特性进行了研究，获得了AF1410钢的Hugoniot关系、塑性应变率、层裂强度以及层裂片厚度等动态力学参数。对回收的AF1410钢样品进行了断口分析和金相分析，从宏、微观角度分析了AF1410钢在不同应变率下的断裂特性。     

强激光对预应力结构件破坏的细观分析

 利用扫描电镜对预应力简单结构件强激光破坏实验的部分试件残片进行了表面、断口和金相观察，分析了强激光对LY12(CZ)铝合金材料性能的影响，初步分析了热力联合加载下材料失效的原因和基本特征，为进一步分析激光破坏机理提供了细观损伤的依据。     

短脉冲载荷下金属材料的层裂破坏

 本文用点炮加载聚酯薄膜飞片撞击金属靶材料，飞片速度0.714~2.24 km/s，脉冲宽度40~80 ns，击靶压力为2.280~11.952 GPa。在回收的铝、铜和钢靶样品上观察到层裂现象。通过金相分析发现它们的破坏方式与在一般较长脉冲加载下的破坏方式相似，铝和铜以延性方式破坏；钢则以脆性方式破坏。一维和二维数值模拟结果表明通常的几种层裂判据在这个应力、应变和应变率范围内也基本上适用。     

Hf-基非晶合金的力学性能研究

 利用MTS810实验机和分离式霍普金森压杆（SHPB）,对Hf_44.5Cu₂₇Ni_13.5Ti₅Al₁₀块体非晶合金进行了准静态和动态压缩实验,应变速率范围为10^-4~10³ s^-1,给出了不同应变速率下非晶合金的应力-应变曲线,并对其压缩断口形貌进行了扫描电镜观察。结果表明：在准静态压缩条件下,Hf_44.5Cu₂₇Ni_13.5Ti₅Al₁₀非晶合金不具有应变速率敏感性,在由放射区和扇形区组成的断口形貌上观察到纳米级韧窝和60 nm左右的周期性条纹结构;在动态压缩条件下,随着应变速率的增加,动态屈服强度明显减小,合金具有应变速率敏感性,同时断裂表面为夹杂着脉络条纹的絮状结构。进一步观察发现,动态压缩断口上存在3种特征断裂形貌：树枝状条纹、典型脉络花纹和合金熔体。     

平面冲击波高速撞击下Zr41Ti14Cu12.5Ni10Be22.5大块非晶合金的损伤与断裂

 利用二级轻气炮研究了在平面冲击波高速撞击下，Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5大块非晶合金的损伤与断裂行为。实验结果表明：在高速冲击压缩下，大块非晶合金断裂面的角度小于通常压缩情况的角度，这是由高速撞击下材料极高的应变速率决定的；极高的应变速率变形和局域绝热剪切加热造成局部熔化；在温度和压力的共同作用下，非晶合金发生晶化现象。     

温升率对预载LY12试件热破坏影响的实验研究

 使用Gleeble 1500热力模拟实验系统研究了不同预载水平下的LY12铝合金试件在以不同温升率快速加热过程中的响应与破坏，实验结果不仅表明高温可使处于低应力水平下的试件发生破坏，而且表明在相同预载水平下，温升率越高则试件发生屈服和断裂时的温度就越高。对试件断口附近的金相组织的分析表明:高温升率下材料微观组织结构的热失配造成的材料微观组织的缺陷对试件的破坏过程具有控制作用。     

冲击荷载下植物纤维增强高聚物 复合材料的力学性能

植物纤维代替人造纤维作为填充体的增强高聚物复合材料可用于汽车、航空航天等工业。选用一定含量的植物纤维及其他填充材料增强高聚物复合材料,在万能材料试验机和分离式霍普金森杆实验装置上进行不同应变率下准静态和动态冲击拉伸及压缩实验。结果显示,在植物纤维中加入少量的纳米黏土颗粒和长玻璃纤维能够较大地提高复合材料的力学性能。使用扫描电子显微镜对不同应变率拉伸下的回收试件断口进行微观分析,揭示了植物纤维增强高聚物复合材料在不同应变率下的断裂特性。     

冲击波物理与爆轰物理学科研究进展

1金属的高压本构研究 利用激光速度干涉技术测量了受冲击LY12铝从冲击压缩状态卸载时，铝样品与LiF窗口界面的粒子：速度剖面，获得了铝从冲击压缩状态卸载时沿着卸载路径的声速。由此计算了剪切模量，从冲击压缩状态卸载时的卸载路径，以及弹塑性本构的知识。     

A non-viscous-featured fractograph in metallic glasses

A fractograph of non-viscous feature but pure shear-offsets was found in three-point bending samples of a ductile Pd–Cu–Si metallic glass. A sustainable shear band multiplication with large plasticity during notch propagation was observed. Such non-viscous-featured fractograph was formed by a crack propagation manner of continual multiple shear bands formation in front of the crack-tip, instead of the conventional rapid fracture along shear bands. With a 2D model of crack propagation by multiple shear bands, we showed that such fracture process was achieved by a faster stress relaxation than shear-softening effect in the sample. This study confirmed that the viscous fracture along shear bands could be not a necessary process in ductile metallic glasses fracture, and could provide new ways to understand the plasticity in the shear-softened metallic glasses.     

强流脉冲电子束辐照诱发纯钼表面的损伤效应及结构缺陷

利用强流脉冲电子束（HCPEB）装置对纯钼表面进行辐照处理,并利用X射线衍射仪,扫描电子显微镜（SEM）、透射电子显微镜（TEM）详细分析了辐照表面的微观结构和损伤效应. 1次HCPEB辐照后,纯钼表层积聚了极大的残余应力,多次辐照后表面未融化区域出现大量绝热剪切带,且局部区域发生开裂. 微观结构分析显示,辐照后材料表面形成发散状的位错组态和大量空位簇缺陷;绝热剪切带内部是尺寸为1 μm 左右等轴状的再结晶晶粒. 剪切带造成的材料表面局部软化以及间隙原子偏聚于晶界是材料发生开裂的主要原因. 另外,表面熔化区域可形成尺寸为20 nm左右的纳米晶. 关键词： 强流脉冲电子束 纯钼 绝热剪切带 空位簇缺陷     

金属熔体近壁面流动剪切模型及其对金属凝固影响的理论研究

本文建立了金属熔体近壁面流动剪切模型, 并分析了流动剪切对金属凝固的影响. 针对A356合金计算结果表明:层流流动的熔体内部剪应力随垂直斜板表面距离的增大而减小, 随着流动长度的增加先急剧下降之后趋于稳定; 紊流流动的熔体所受的剪应力随着垂直倾斜板表面距离的增大先急剧下降之后趋于稳定, 随着流动长度的增加而不断增大; 斜板倾角越大, 斜板上相同位置的熔体层受到的剪应力越大; 熔体垂直斜板表面距离越小, 柱状晶所承受的弯曲应力越大; 斜角越大, 斜板上相同位置的柱状晶的弯曲应力越大; 随着熔体在倾斜板表面流动长度的增加, 在层流阶段, 倾斜板表面柱状晶根部所受的弯曲应力先急剧下降之后趋于平稳, 而在紊流阶段, 弯曲应力是缓慢增加的; 理论分析表明柱状晶在熔体近壁面流动过程受到的最大弯曲应力低于αup -Al晶粒的屈服强度, 所以斜板上熔体流动产生的弯曲力不能将柱状晶折断, 只能将晶粒冲刷游离到熔体中使晶粒增殖, 与实验结果相符合. 所以本模型可以很好地解释熔体近壁面流动过程中的剪切本构关系以及剪应力对凝固组织的影响.     

The mechanisms of plastic strain accommodation during the high strain rate collapse of corrugated Ni–Al laminate cylinders

The Thick-Walled Cylinder method was used on corrugated Ni–Al reactive laminates to examine how their mesostructures accommodate large strain, high strain rate plastic deformation and to examine the potential for intermetallic reaction initiation due to mechanical stimuli. Three main mesoscale mechanisms of large plastic strain accommodation were observed in addition to the bulk distributed uniform plastic flow: (a) the extrusion of wedge-shaped regions into the interior of the cylinder along planes of easy slip provided by angled layers, (b) the development of trans-layer shear bands in the layers with orientation close to radial and (c) the cooperative buckling of neighbouring layers perpendicular to the radius. These mesoscale mechanisms acted to block the development of periodic patterns of multiple, uniformly distributed, shear bands that have been observed in all previously examined solid homogeneous materials and granular materials. The high-strain plastic flow within the shear bands resulted in the dramatic elongation and fragmentation of Ni and Al layers. The quenched reaction between Al and Ni was observed inside these trans-layer shear bands and in a number of the interfacial extruded wedge-shaped regions. The reaction initiated in these spots did not ignite the bulk of the material, demonstrating that these mesostructured Ni-Al laminates are able to withstand high-strain, high-strain rate deformation without reaction. Numerical simulations of the explosively collapsed samples were performed using the digitized geometry of corrugated laminates and predictions of the final, deformed mesostructures agree with the observed deformation patterns.     

TC4钛合金及40Cr钢破片中绝热剪切带的TEM分析

 对含有约热剪切带（ASB）的TC4钛合金及40Cr钢破片作了扫描电镜（SEM）和透射电镜（TEM）分析。结果表明，TC4钛合40Cr钢中的ASB是由平均直径不到0.3 μm的微晶组成，微晶列有一定择优取向，电子衍射花样表现为不连续的环状。ASB内位错密度均很低，其邻近基体区含有高密度位错，ASB内没有察到相变发生。     

Ultrasound velocimetry in a shear-thickening wormlike micellar solution: Evidence for the coexistence of radial and vorticity shear bands

We carried out pointwise local velocity measurements on 40 mM cetylpyridinium chloride-sodium salicylate (CPyCl-NaSal) wormlike micellar solution using high-frequency ultrasound velocimetry in a Couette shear cell. The studied wormlike solution exhibits Newtonian, shear-thinning and shear-thickening rheological behavior in a stress-controlled environment. Previous rheology, flow visualization and small-angle light/neutron scattering experiments in the shear-thickening regime of this system showed the presence of stress-driven alternating transparent and turbid rings or vorticity bands along the axis of the Couette geometry. Through local velocity measurements we observe a homogeneous flow inside the 1mm gap of the Couette cell in the shear-thinning (stress-plateau) region. Only when the solution is sheared beyond the critical shear stress (shear-thickening regime) in a stress-controlled experiment, we observe inhomogeneous flow characterized by radial or velocity gradient shear bands with a highly sheared band near the rotor and a weakly sheared band near the stator of the Couette geometry. Furthermore, fast measurements performed in the shear-thickening regime to capture the temporal evolution of local velocities indicate coexistence of both radial and vorticity shear bands. However the same measurements carried out in shear rate controlled mode of the rheometer do not show such rheological complexity.     

Microscopical study of the formation of adiabatic shear bands in 4340 steel during dynamic loading

In this study, optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and electron probe microanalyser were used to analyse the changes in microstructure of AISI 4340 steel specimens caused by impact at high strain rates and large strains. The structures of the steel prior to dynamic deformation and after dynamic deformation were examined to understand on a microscale level, the mechanism of formation of adiabatic shear bands (ASBs). The study also includes the structural changes that occur during post-deformation annealing processes which may relate to understanding of the mechanism of formation of ASBs. Prior to deformation, the tempered steel specimens consisted of lenticular laths of α-ferrite with precipitated platelet and spherical M₃C carbides. After impact, the structure inside the shear band was characterized by refined and recrystallized grains immersed in dense dislocation structures. In addition, residual carbide particles were observed inside the shear bands due to deformation induced carbide dissolution. Regions away from the shear bands developed ‘knitted’ dislocation walls, evolving gradually into sub-boundaries and highly misoriented grain boundaries at increasing strains, leading to grain refinement of the ferrite. After impact, annealing the shear bands at 350?°C resulted in an increase in hardness regardless of the heat treatment before impact, amount of deformation and the time of annealing. This is because of the occurrence of extensive reprecipitation of dissolved carbides that existed in the steel structure prior to deformation. It is concluded that dynamic recovery/recrystallization, development of dislocation structures and carbide dissolution all contribute simultaneously to the formation of ASBs in quench-hardened steels.     

Localization of plastic strain under shock-wave loading of titanium alloy with a crack

The effect of shock-wave loading with an amplitude of 4 GPa and a duration of 10 μs on the localization of plastic flow and the dynamic fracture of VT-1 cast titanium alloy containing a disk-shaped crack is considered. It is found that the crack size decreases in the direction of shock wave propagation, the dislocation density grows and adiabatic shear bands appear near the crack, and secondary cracks originate in the areas of localized flow near the crack edges. The strain, strain rate, dislocation density, rate of dislocation generation, and dislocation velocity near and away from the healing crack are estimated.     

激波沿H2／空气界面绕圆、方柱强化混合的数值研究

用迎风TVD格式求解二维、层流全N－S方程,对激波沿H2和空气界面绕圆、方柱流动及其诱导的剪切混合进行了数值模拟,得到了流场的压力和组分密度分布,计算结果表明：激波在H2传播得快,剪切层中出现吸涡和调节激波,卷吸涡与柱体撞击后,反射出一道激波,H2沿柱体表面向下游扩散,H2／空气接触面与柱体分离后,形状畸变并产生新的卷吸涡。H2分布表明：在办面上加圆柱或方柱,可有效地强化燃料混合,方柱的增强效果更明显此,在圆柱表面,H2、空气中激波均发生由RR向MR的转变,两Mach杆在下游相互透射,对于方柱,H2中激波中激波沿下表面传播几乎不受影响,空气中激波沿上表面发生Mach反射,其Mach杆和H2中绕射激波相互透射,柱体左侧最终形成一脱体激波,流场存在激波、卷吸涡、接触面向的相互作用,但波系结构相似。