高强度装甲钢中绝热剪切破坏研究

为了研究高强度装甲钢的穿甲破坏机理，采用１２．７ｍｍ弹道枪垂直射击１５ｍｍ厚的Ｍｎ－Ｃｒ－Ｎｉ－Ｍｏ－Ｂ高强度装甲钢板，弹丸速度在３５０～５００ｍ／ｓ内变化，分析了绝热剪切带的产生及其对冲塞穿甲的作用。试验结果表明，当弹靶参数一定时，高强度钢板中易发生绝热剪切导致的冲塞穿甲，由微观组织和硬度测试证明绝热剪切带是一种转变带。转变带内的裂纹和沿转变带扩展的裂纹对装甲的钢的破坏影响极大。     

硬度对装甲钢板抗弹性能的影响

借助用53式7．62mm WO-109C穿甲燃烧弹垂直撞击10mm厚、硬度为HRC44－56的Cr-Ni-Mo装甲钢板的穿甲试验研究了高硬度及超高硬度状态下硬度对装甲钢板抗弹性能的影响。观察分析弹坑形貌发现,装甲钢板材料力学性能的改变导致了穿甲机理的变化。一方面,硬度升高,增加弹丸开坑所消耗的能量,提高弹丸消耗的塑性扩孔功,且当硬度超过一定值时,弹丸可能发生破碎,从而有利于抗弹性能的提高。另一方面,硬度升高,导致绝热剪切临界失稳应变降低,易诱发冲塞破坏,而且塑性与韧性降低,可能导致背面盘状崩落破坏,从而使抗弹性能下降。在本试验弹靶体系下,上述两方面相反作用的结果导致装甲钢板背面强度极限基本上不随硬度变化而改变。     

弹丸高速冲击条件下高强度钢板抗弹性能

为了研究弹丸高速冲击条件下不同洁净度的40CrNi2Mo钢板的抗弹性能,利用12.7 mm穿甲燃烧弹对抗拉强度分别为800和1 200 MPa级的钢板进行抗弹性能测试。通过观察不同强度钢板出现的损伤形貌,评定背面强度极限,分析了穿甲机制。结果表明:抗拉强度为800 MPa级的钢板在弹丸冲击过程中以塑性扩孔方式侵彻,抗弹性能随着强度升高而提高,与洁净度关系不大。抗拉强度为1 200 MPa级的钢板,弹丸冲击过程中因钢板较低的绝热剪切临界失稳应变而出现绝热剪切;由于塑韧性较低,低洁净度钢板阻止绝热剪切引发裂纹扩展的能力较弱,因此形成与绝热剪切相关的裂纹,导致抗弹性能降低;高洁净度钢板抗弹性能相对较高,因背面出现剪切裂纹而失效,此裂纹与绝热剪切无关。     

弹丸高速冲击条件下高强度钢板抗弹性能

摘要：为了研究弹丸高速冲击条件下不同洁净度的40CrNi2Mo钢板的抗弹性能，利用12.7mm穿甲燃烧弹对抗拉强度分别为800和1200MPa级的钢板进行抗弹性能测试。通过观察不同强度钢板出现的损伤形貌，评定背面强度极限，分析了穿甲机制。结果表明：抗拉强度为800MPa级的钢板在弹丸冲击过程中以塑性扩孔方式侵彻，抗弹性能随着强度升高而提高，与洁净度关系不大。抗拉强度为1200MPa级的钢板，弹丸冲击过程中因钢板较低的绝热剪切临界失稳应变而出现绝热剪切；由于塑韧性较低，低洁净度钢板阻止绝热剪切引发裂纹扩展的能力较弱，因此形成与绝热剪切相关的裂纹，导致抗弹性能降低；高洁净度钢板抗弹性能相对较高，因背面出现剪切裂纹而失效，此裂纹与绝热剪切无关。     

连续钨丝增强锆基块体金属玻璃变形过程中剪切带演化

研究体积分数为60%的连续钨丝/Zr41.2Ti13.8Cu12.5Ni10Be22.5块体金属玻璃复合材料准静态压缩变形过程中剪切带的演化过程。发现在弹性变形段不形成剪切带,剪切带是在塑性变形过程中产生并发展的,且剪切带的数量随着变形量的增加而增大,间距随着变形量的增加而减小;当间距减小到一定值时产生剪切裂纹并不断扩展,最终导致断裂破坏。     

Ti-22Al-15Nb合金的力学性能及破坏机理研究

研究了名义成分为Ti-22Al-15Nb的Ti-Al系合金的微观组织和力学性能,以及在准静态和动态加载条件下的变形行为,并对其破坏机理进行了分析。微观组织研究表明,Ti-22Al-15Nb合金铸态组织为等轴晶,晶内主要由α2-Ti3Al相和B2-Ti2AlNb相组成,具有随机取向的片状α2相均匀分布在B2基相上。力学性能研究表明,合金在动态加载条件下表现出较优异的性能,其屈服强度为1 100 MPa,抗压强度为1 750 MPa,且在动态加载下具有更好的塑性。破坏机理分析表明,在准静态加载条件下,合金试样发生剪切破坏,微裂纹首先在α2相及α2相与B2相的相界处萌生,在最大剪应力方向上扩展形成主裂纹,最终导致合金试样破坏;在动态加载条件下,合金的破坏方式为绝热剪切破坏,即在与加载轴呈45°角的方向上形成绝热剪切带,随着应变的增大,裂纹在剪切带中萌生并扩展,最终破坏合金试样。     

变形量对旋转锻造钨合金组织及绝热剪切敏感性影响

对烧结态93W-4.9Ni-2.1Fe合金进行不同变形量旋转锻造,研究变形量对钨合金微观组织及绝热剪切敏感性的影响。微观组织观察结果表明,旋转锻造形变后钨颗粒沿变形方向被拉长为椭球形,随变形量由3.45%增加至42.11%,钨颗粒变形程度加剧,长径比由1.32增加至2.41;位于钨颗粒间的粘结相则沿变形方向逐渐拉长为细长的条状组织。对不同变形量的旋转锻造钨合金,沿棒料径向取样进行动态压缩试验后发现:当变形量增加至15.84%(钨颗粒长径比1.47)时,旋转锻造钨合金塑性变形方式发生改变,合金中开始出现绝热剪切现象;此后,随旋转锻造变形量(钨颗粒长径比)的增加,旋转锻造钨合金中绝热剪切带宽度减小,合金绝热剪切敏感性增大。随旋转锻造变形量(钨颗粒长径比)的增大,合金应变硬化能力减小,同时动态加载时绝热温升数值增大,软化效应增强,这是旋转锻造钨合金绝热剪切敏感性随变形量(钨颗粒长径比)增加而增大的主要原因。     

细晶钨合金的绝热剪切敏感性

采用粉末冶金法制备平均晶粒度<5μm细晶90W-Ni-Fe含金.利用HOPKINSON压杆装置,分别在0.9 MPa和1.4 MPa的冲击气压条件下对该合金进行一维应力冲击实验,并对冲击后的样品进行金相组织观测,考察其在一维应力冲击条件下的绝热剪切性能,分析细晶钨合金的绝热剪切敏感性.研究表明:晶粒细化有助于绝热剪切带的扩展,可以提高钨合金绝热剪切敏感性,使得烧结态细晶钨合金在一维冲击应力加载条件下就可以产生绝热剪切带.随着冲击(加载)气压的加大,绝热剪切现象更明显,冲击气压为1.4 MPa时剪切带宽度约为10μm,从而有助于材料在动态压缩条件下产生绝热剪切破坏,提高材料在穿甲过程中的"自锐"能力.     

丹池成矿带五圩矿集区矿床地质特征及构造成矿分析——以箭猪坡矿床为例

根据岩层能干性特征,五圩矿集区整体结构为两"强"夹一"弱"的"三明治"岩层结构,以箭猪坡最为典型,赋矿层位为弱能干性泥岩层。通过对箭猪坡矿床脉状矿体构式和平面、剖面矿脉展布特征的观察和分析,判断矿体形成于印支早期脆—韧性逆冲剪切带中,矿脉呈雁列状向深部倾伏,之后受印支晚期断展褶皱和燕山期SN向褶皱叠加、改造,最终使矿脉走向为NNW、剖面呈正"八"字形分布。矿脉直接受脆—韧性逆冲剪切带分布范围的控制。由此推断,具备"三明治"岩层结构的丹池成矿带内,在中间的泥岩层内均可能赋存脆—韧性剪切带控制的脉状矿体。     

老挝沙耶武里地区纳克汗(B.Nakhan)剪切带岩石有限应变特征及其与金成矿关系探讨

本文通过对老挝沙耶武里地区纳克汗(B.Nakhan)剪切带进行岩石学、构造样式、动力学及运动学分析,认为该剪切带应变型式以K1的挤压型应变为主,表明其形成于挤压环境。带内构造岩的矿物组合以绿片岩相为主,变形温度为250℃~300℃,为一条具多期活动的低温绿片岩相具右旋逆冲型韧性剪切带。同时,在区域上纳克汗(B.Nakhan)剪切带与已发现的金矿带分布位置关系密切,空间上属于韧脆性区—脆性区域,这为下一步研究沙耶武里地区韧性剪切带与金矿的关系研究提供了一个新的重点方向。     

The study of adiabatic shear band instability in a pearlitic 4340 steel using a dynamic punch test

The formation of adiabatic shear band instabilities in a pearlitic 4340 steel using a dynamic punch test has been studied. The dynamic punch-impact test produced white-etching adiabatic shear bands. The average strain of 0.5 was sufficient to produce adiabatic shear bands in this steel at an average strain rate of 18,000 s⁻¹. Nanohardness variations found across the adiabatic shear band are thought to be caused by the fragmentation and spheroidization of the Fe₃C and the overall deformation and work hardening of the pearlitic microstructure. The cracks formed at the termination of the adiabatic shear band caused the sample to fracture in a ductile mode.     

Development of adiabatic shear bands in annealed 316L stainless steel: Part I. Correlation between evolving microstructure and mechanical behavior

Adiabatic shear localization in an annealed AISI 316L stainless steel was examined through a forced shear technique using a split Hopkinson pressure bar and hat-shaped specimens. A well-controlled forced shear technique provided the possibility of correlating the microstructural evolution of adiabatic shear localization to its transient mechanical behavior. The initiation of adiabatic shear bands occurred when the shear stress peaked after substantial work hardening. The work-hardening rate was found to play a dominant role in the formation of adiabatic shear localization. The stress drop presupposed the development of the localized deformation. A core structure of shear bands was generated within the shear band, which characterized a narrow-down process in the early stage of the shear band evolution. The continuous expansion of the shear band core to the entire width of the band was seen to correlate with the full development of shear localization.     

Deformation Mapping and the Role of Carbides on the Microstructure and Properties of Evolved Adiabatic Shear Bands

Impacting hardenable steel such as 4340, results in the formation of adiabatic shear bands (ASBs). Previous studies have shown that the presence of carbides/second-phase particles in the pre-deformation microstructures of 4340 steel increases their susceptibility to the formation of ASBs. The current study examines the role of carbides on the microstructure and properties within evolved ASBs in 4340 steel after impact. Geometric phase analysis was used to map local deformation fields within the evolved ASBs. It was observed that carbide fragmentation due to plastic deformation of carbides produces both residual carbides and residual carbide particles in regions away from the shear bands. Extensive carbide fragmentation produces fine residual carbide particles which are redistributed within the ASBs. This is attributed to strain localization within the ASBs which result in higher local strain and strain rates within the shear bands than in regions outside the bands. In addition, it is observed that the residual carbide particles trap and pin dislocations within the shear bands and contribute to an increase in local hardening. A more homogenous distribution of narrower and shorter rotational and shear-strain fields were revealed by the local deformation maps within the evolved ASBs. Lattice deformation mapping revealed that the ferrite matrix, prior to impact, had broader and longer rotational and shear-strain fields perpendicular to the direction of impact. This is attributed to lattice-invariant deformation and shape deformation processes that occur on specific crystallographic planes during martensitic transformation. It is concluded that strain localization during high strain rate deformations does not occur on specific crystallographic planes. This results in a more regular distribution of internal lattice rotational and strain fields within the evolved ASBs.     

Influence of initial texture on the microstructural instabilities during compression of commercial α-Titanium at 25 °C to 400 °C

Cylindrical specimens of textured commercial pure α-titanium plate, cut with the cylinder axis along the rolling direction for one set of experiments and in the long transverse direction for the other set, were compressed at strain rates in the range of 0.001 to 100 s~’ and temperatures in the range of 25 °C to 400 °C. At strain rates ≥ 1 s⁻¹ ’, both sets of specimens exhibited adiabatic shear bands, but the intensity of shear bands was found to be higher in the rolling direction specimens than in the long transverse direction specimens. At strain rates ⪯0.1s ⁻¹ the material deformed in a microstructurally inhomogeneous fashion. For the rolling direction specimens, cracking was observed at 100 °C and at strain rates ⪯0.1 s⁻¹. This is attributed to dynamic strain aging. Such cracking was not observed in the long transverse specimens. The differences in the intensity of adiabatic shear bands and that of dynamic strain aging between the two sets of test specimens are attributed to the strong crystallographic texture present in these plates.     

Adiabatic shear band formation in Al-SiCw composites

The objective of this study is to investigate the adiabatic shear band formation in 2124-T6 aluminum composites reinforced with SiC whiskers. The composites were deformed at high strain rates by ballistic impact. Adiabatic shear bands initiated from cracks near the impacted region were observed. The shear bands tended to propagate along the extrusion direction, since they were blocked by SiC whiskers. Within the shear bands, microvoids and microcracks formed, presumably by the temperature rise. Shear bands, together with microvoids and microcracks, deteriorated the impact resistance of target materials. Finally, performance of the composites against ballistic impact loading was discussed by comparing the behavior of shear banding with dynamic fracture toughness.     

Dynamic deformation behavior and ballistic impact properties of Ti-6Al-4V alloy having equiaxed and bimodal microstructures

Effects of microstructural morphology on dynamic deformation behavior and ballistic impact properties of Ti-6Al-4V alloy plates were investigated in this study. Dynamic torsional and ballistic impact tests were conducted on equiaxed and bimodal microstructures, which were processed by different heat treatments, and then the test data were analyzed in relation to microstructures and tensile properties. According to the dynamic torsional test data, maximum shear stress and fracture shear strain of the bimodal microstructure were higher than those of the equiaxed microstructure, and the possibility of the adiabatic shear band formation was more likely in the equiaxed microstructure than in the bimodal microstructure. In the ballistically impacted region of the equiaxed microstructure, a number of adiabatic shear bands and cracks were observed to be formed along plastic flow lines, and delamination occurred because of cracking along the flow lines or shear bands. In the case of the bimodal microstructure, shear bands were found in limited areas near the penetrated surface without occurring delamination, and their number was smaller than that of the equiaxed microstructure. Thus, ballistic performance of the bimodal microstructure was better than that of the equiaxed microstructure, which was consistent with the dynamic torsional test results.     

Microstructural study of adiabatic shear band

This article presents a study of the microstructural development of the adiabatic shear band in an HY-100 steel. The steel was deformed at a high strain rate by ballistic impact, and subsequent metallographic observations along with electron microscopy were performed. A number of white- etched shear bands were found near the perforated region, and three typical microstructural features of the adiabatic shear band were observed: elongated grain structure at the boundary between the shear band and matrix, fine equiaxed grain structure with high dislocation densities in the middle of the shear band, and relatively coarse-grained structure located between the above two structures. These microstructures might be formed in an extremely short time by the combined effects of the large temperature rise and the highly localized deformation. Since very complex phenomena might occur within the shear band, possible mechanisms, such as dynamic recovery and strain-induced dynamic phase transformation, are suggested to explain the micro- structural development of the adiabatic shear band.     

多向高速冲击下LZ91镁合金的力学性能及组织

常温下采用霍普金森压杆在冲击气压为0.2MPa~0.7MPa的条件下对LZ91镁合金进行多向高速冲击,结合变形后的微观组织及应力应变曲线,分析应变速率和不同冲击方向对微观组织演变的影响。结果表明,冲击过程中β-Li和α-Mg的滑板效应和形变温升产生的软化作用和加工硬化存在竞争关系,导致随着应变速率增加和材料初始组织中位错密度的增加,应力应变曲线并不呈现单调增加的趋势;当局部应力达到一定程度,就会在材料内部产生绝热剪切带,继而在绝热剪切带内产生位错缠结并形成微型孔洞,最后形成裂纹。