45#钢高速冲击穿孔的显微组织

借助烧结的W合金圆柱体垂直冲击60mm厚的45^#热轧钢板实验,利用扫描电镜和光学金相显微镜研究了45^#钢高速冲击穿孔的显微组织。冲击波使穿孔周围的晶粒破碎,冲击引起的材料变形功转变为热能,以及侵彻过程中的摩擦作用,使穿孔表面熔化,靠近熔化区的晶粒发生再结晶。从穿孔表面到钢板内部可分为：熔化快凝层、再结晶细晶层、变形细晶层、形变层和正常基体组织。在细晶层和形变层中,铁素体晶粒的变形量要远远大于珠光体,部分珠光体开裂,其周围形成微裂纹和微孔洞。钢中的硫化锰夹杂在变形中被剧烈拉长。由于铁素体的塑性,钢板的破坏方式为延性扩孔。     

穿甲靶板弹孔微观结构观察及侵彻过程分析

为研究穿甲侵彻机理,使用海37弹道炮,发射93W次口径穿甲弹,侵彻45靶板,采用扫描电镜和透射电镜研究弹孔周围微观结构特点.研究结果表明,绝大部分弹孔表面被溶化快凝物覆盖,其厚度约为10μm,其内未发现腐蚀组织.熔化物中含有钨的成分,说明在侵彻过程中产生的高压下,钨颗粒可以熔化.高速碰撞动能在侵彻瞬间可能使弹靶部分作用区域的温度超过钨的熔点.靶板材料在局部区域熔化和再结晶,破坏形式为延性扩孔破坏,观察弹孔周围未发现绝热剪切带.     

Numerical simulations of impact behaviour of thin steel plates subjected to cylindrical,conical and hemispherical non-deformable projectiles

In this paper, a numerical study of normal perforation of thin steel plates impacted by different projectile shapes is reported. The numerical simulations of this problem have been performed using a finite element code, ABAQUS-Explicit with a fixed and an adaptive mesh for the plate. To define the thermoviscoplastic behaviour of the material constituting the plate, the Johnson–Cook model has been used. This homogeneous behaviour has been coupled with the Johnson–Cook fracture criterion to predict completely the perforation process. Three kinds of projectile shape (blunt, conical and hemispherical) have been simulated with a large range of impact velocities from 190 to 600 m/s. The analysis considers the influence of adiabatic shear bands, plastic work and the gradient of temperature generated in the plate. The numerical results predict correctly the behaviour projectile-plate in agreement with experimental data published by other authors.     

正交切削高强度钢绝热剪切带组织和硬度研究

为了研究切削速度和工件硬度对高强度钢锯齿形切屑内绝热剪切带显微组织和硬度的影响,利用光学显微分析、SEM和TEM以及硬度测量等方法观察和测量了不同切削速度下正交切削两种回火硬度的30CrNi3MoV钢形成的锯齿形切屑中绝热剪切带的微观组织和显微硬度的变化过程.结果表明:低速下形成以组织剧烈拉长为特征的形变带,高速下形成以组织严重细化为特征的转变带;工件硬度的提高有利于形成转变带;增加切削速度和工件硬度对转变带硬度影响很小,但会显著提高形变带硬度.     

Ballistic Limit of Single and Layered Aluminium Plates

Abstract: This paper presents an experimental and finite‐element investigation of ballistic limit of thin single and layered aluminium target plates. Blunt‐, ogive‐ and hemispherical‐nosed steel projectiles of 19 mm diameter were impacted on single and layered aluminium target plates of thicknesses 0.5, 0.71, 1.0, 1.5, 2.0, 2.5 and 3 mm with the help of a pressure gun to obtain the ballistic limit in each case. The ballistic limit of target plate was found to be considerably affected by the projectile nose shape. Thin monolithic target plates as well as layered in‐contact plates offered lowest ballistic resistance against the impact of ogive‐nosed projectiles. Thicker monolithic plates on the other hand, offered lowest resistance against the impact of blunt‐nosed projectiles. The ballistic resistance of the layered targets decreased with increase in the number of layers for constant overall target thickness. Axi‐symmetric numerical simulations were performed with ABAQUS/Explicit to compare the numerical predictions with experiments. 3D numerical simulations were also performed for single plate of 1.0 mm thickness and two layered plate of 0.5 mm thickness impacted by blunt‐, ogive‐ and hemispherical‐nosed projectiles. Good agreement was found between the numerical simulations and experiments. 3D numerical simulations accurately predicted the failure mode of target plates.     

Effect of projectile nose shape,impact velocity and target thickness on the deformation behavior of layered plates

The present study is based on the experimental and numerical investigations of deformation behavior of layered aluminum plates of different thicknesses under the impact of flat, ogive and hemispherical nosed steel projectiles. Thin-layered plates arranged in various combinations were normally impacted at different velocities with the help of a pneumatic gun. Ballistic limit velocity and the residual velocity of the projectiles for each layered combination were obtained experimentally as well as from the finite element code, and these were compared with those of the single plates of equivalent thicknesses. For two layers, the residual velocity was comparable to that of the single plate, however, when the number of layers was increased the velocity drop was found to be higher in the case of the single plate. Ogive nosed projectile was found to be the most efficient penetrator of the layered target. Hemispherical nosed projectile required maximum energy for perforation. Deformation profiles of the target plates in the layered combinations were measured, and it was found that hemispherical nosed projectile caused highest plastic deformation of target plates. Numerical simulation of the problem was carried out using finite element code ABAQUS. Explicit solution technique of the code was used to analyze the perforation phenomenon. Results of the finite element analysis were compared with experiments and a good agreement between the two was found.     

Study based on the analysis of valence electron structure for adiabatic shear sensitivity of 30CrMnMo and C45E4 steel in process of high‐speed penetration

In this paper, the influence of valence electron structure parameters on the adiabatic shearing sensitivity has been studied for two grade steels (30CrMnMo and C45E4) as a function of covalent pair number and lattice electron number by empirical electron theory of solids and molecules in high‐speed penetration process. The research shows that the adiabatic shearing sensitivity increases with the increase of the covalent electron pair number n_A, decreases with the increase of the lattice electron number n_l. The n_A of each structure unit in 30CrMnMo steel is larger than that in C45E4steel, the n_l of each structure unit in 30CrMnMo steel is smaller than that in C45E4steel. Therefore, the adiabatic shearing sensitivity is higher for 30CrMnMo targets damaged by adiabatic shear failure, and yet C45E4 targets were damaged by ductile fracture without any adiabatic shear band. The basis can be provided for appropriately selecting and designing materials with different adiabatic shearing sensitivity by studying the specific alloy elements on the influence of adiabatic shearing sensitivity in valence electron structure level.     

Influence of sharp microstructural gradients on the fatigue crack growth resistance of α+β and near-α titanium alloys

The present study focuses on the effect of microstructural gradients on the fatigue crack growth resistance of Ti‐6Al‐4V and Ti‐6242 titanium alloys. Sharp microstructural gradients from fine‐grained bimodal to coarse‐grained lamellar microstructures were obtained by heat treating only a portion of fine‐grained plates in the β single‐phase field using a high‐frequency induction coil. For fatigue crack growth from a bimodal into a lamellar microstructure, it was found that the initial crack extension past the microstructural transition within the lamellar microstructure shows the same crack growth resistance as the reference bimodal microstructure. Similarly, for fatigue crack growth from a lamellar into a bimodal microstructure, the initial crack extension past the microstructural transition within the bimodal microstructure shows same crack growth resistance as the reference lamellar microstructure. Based on detailed crack front profile investigations using optical light and scanning electron microscopy as well as heat tinting procedures, these findings can be mainly attributed to the effect of the crack front geometry.     

Initiation of adiabatic shear failure in a clamped circular plate struck by a blunt projectile

This paper presents an analytical model for studying the material failure in shear hinges formed during the dynamic plastic response of a circular plate under projectile impact. Analytic solutions for the ballistic perforation performance of a fully clamped circular plate struck by a blunt projectile are obtained. It takes into account both the global response (plate bending) and the localized shear. Based on the estimations of the shear strain and the size of shear hinge, condition for the initiation of an adiabatic shear band is formulated. The effectiveness of the present model is demonstrated by reasonable agreement between the theoretical predictions and the available experimental data for the perforation of Weldox 460E steel plates.     

On the influence of constitutive relation in projectile impact of steel plates

In this paper the influence of constitutive relation has been studied in numerical simulations of the perforation of 12-mm thick Weldox 460 E steel plates impacted by blunt-nosed projectiles in the sub-ordinance velocity regime. A modified version of the well-known and much used constitutive relation proposed by Johnson-Cook and both the bcc- and hcp-version of the Zerilli-Armstrong constitutive relation were combined with the Johnson-Cook fracture criterion. These models were implemented as user-defined material models in the non-linear finite element code LS-DYNA. Identification procedures have been proposed, and the different models were calibrated and validated for the target material using available experimental data obtained from tensile tests where the effects of strain rate, temperature and stress triaxiality were taken into account. Perforation tests carried out in a compressed gas gun on 12-mm-thick circular Weldox 460 E steel plates were then used as base in a validation study of plate perforation using LS-DYNA and the proposed constitutive relations. The numerical study indicated that the physical mechanisms during perforation can be qualitatively well predicted by all constitutive relations, but quantitatively more severe differences appear. The reasons for this are discussed in some detail. It was concluded that for practical applications, the Johnson-Cook constitutive relation and fracture criterion seems to be a good choice for this particular problem and excellent agreement with the experimental results of projectile impact on steel plates were obtained under the conditions investigated.     

Effect of distance from the support on the penetration mechanism of clamped circular polycarbonate armor plates

A 1.91-mm thick circular polycarbonate plate of 115 mm diameter was impacted by a spherical steel projectile of 6.98 mm diameter at its center. Subsequent impacts were made at 10, 20, 30, 40, and 50 mm radii of the plate. Dent dimensions for the damaged plate were measured using optical microscope. For a constant projectile velocity of 138 m s⁻¹ which was below the perforation limit of the plate under investigation, a maximum thickness reduction close to the edge support was observed. The experimental work was modeled into explicit finite-element analysis program LSDYNA for simulations. LSDYNA was able to predict the dent depth and reduction in plate thickness at impact points precisely. In this research, the effect of the impact location distance from the supports on the damage mechanism of circular polycarbonate armor plates is investigated. The target plate was subjected to constant velocity projectile impacts starting at the plate midpoint and varying the impact distance from midpoint towards the clamped edge. Failure of plate is predicted close to the constrained boundary under uniform conditions.     

Lokale Hochverformung zur Erzeugung von ultrafeinkörnigen Zonen

Local severe plastic deformation for producing ultrafine‐grained regions The methods of severe plastic deformation are able to produce semi‐finished products with a homogenous ultrafine‐grained microstructure. An alternative option is the formation of ultrafine‐grained layers or rather a gradation of the grain size. The qualification of incremental bulk forming processes is concluded from an analysis of methods for producing ultra fine‐grained materials and the kneading in cyclic forming. Spin extrusion is investigated regarding the formation of ultra fine‐grained regions. Tests are carried out to analyse the grain refinement in cyclically deformed regions.     

Synthesis of Boride Coating on Steel using High Energy Density Processes: Comparative Study of Evolution of Microstructure

Ultrahard titanium diboride (TiB₂) coatings are deposited on plain carbon steel substrate using two high energy density processes, viz. pulsed electrode surfacing (PES) and laser surface engineering (LSE). These two processes are entirely different in physical nature and hence result in dissimilar microstructures. In the present investigation, a comparative study has been made between the evolved microstructures. Both processes produced a surface layer which is adherent and metallurgically bonded to the substrate. PES produced relatively thinner and less uniform coating than LSE process. The PES coating was, however, homogeneous and very fine grained. The laser-assisted coating was “composite” in nature with TiB₂ particles embedded in Fe matrix. Mechanical characterization of these coatings has been performed using microhardness measurements.     

Perforation of AA5083-H116 aluminium plates with conical-nose steel projectiles—experimental study

The interest regarding use of aluminium alloys in lightweight protective structures is today increasing. Even so, the number of experimental and computational investigations giving detailed information on such problems is still rather limited. In this paper, perforation experiments have been performed on AA5083-H116 aluminium plates with thicknesses varying between 15 and 30 mm impacted by 20 mm diameter, 98 mm long, HRC 53 conical-nose hardened steel projectiles. In all tests, initial and residual velocities of the projectile were measured and a digital high-speed camera system was used to photograph the penetration and perforation process. Based on these measurements, impact versus residual velocity curves of the target plates were constructed and the ballistic limit velocity of each target was obtained. An analytical perforation model from the open literature is then used to predict the ballistic limit velocity, and excellent agreement with the experimental data is found. The experimental results are finally compared to similar experiments on steel and concrete targets, and the capacity of the different materials is evaluated in relation to total weight.     

13MnNiMoNbR与00Cr19Ni10异种钢焊接接头的组织与性能

首先将H309L焊丝堆焊在13MnNiMoNbR钢板坡口上,再将堆焊后的13MnNiMoNbR钢板与00Cr19Ni10钢板用H308L焊丝填充焊接,得到了13MnNiMoNbR与00Cr19Ni10异种钢焊接接头,并对接头的显微组织及硬度进行了分析。结果表明：13MnNiMoNbR钢板侧熔合线附近出现了粗大的铁素体组织,形成脱碳层,而H309L焊缝侧的奥氏体堆焊层熔合线附近出现了黑色的非常细小的碳化物析出层;由于碳化物的析出或是固溶碳,使H309L焊缝侧增碳层处的硬度明显升高。     

Influences of microstructure and orientation on fracture toughness of intermetallic phase Al2Cu‐based alloy under directional solidification

The influences of microstructures and orientations on fracture toughness of intermetallic phase Al₂Cu‐based alloys during different directionally solidified rates were investigated. With solidified rates increasing, the patterns of Al₂Cu phase dendrite turned from faceted V‐shaped morphology to elongated plate‐shaped morphology and discontinuous complex morphology in longitudinal section. Moreover, the deviation angle between the growth direction of Al₂Cu dendrite and the heat flow direction was increasing. Because of fine grain toughening and crack propagation path deflected by orientation, the fracture toughness of Al₂Cu‐based alloy was improved. The experimental results showed that improving the brittleness could be well achieved under higher directionally solidified rate.     

CSP流程生产低碳高强度汽车板组织性能的研究

研究了珠钢电炉CSP工艺生产低碳高强度钢板的热轧工艺与组织性能之间的关系,通过光学显微镜和力学性能试验等检测分析技术分析了控制轧制和冷却各阶段工艺参数对成品板显微组织和力学性能的影响.研究表明:降低终轧温度和卷取温度可有效细化晶粒,提高钢板的强度;采用适当的控轧控冷工艺制度,可以获得不同强度级别强韧性能良好的热轧低碳高强度汽车用钢板.     

分析金属装甲弹道极限的两阶段模型

基于大量弹道试验分析,考虑靶板背面自由边界的影响,提出一个分析刚性尖头弹垂直撞击中等厚度理想弹塑性材料靶板弹道极限的两阶段工程模型。由圆柱形空腔膨胀理论和功能原理导出第一阶段延性扩孔耗能表达式,按薄靶板最小穿透能量的简化分析模型计算第二阶段耗能,由两阶段总的耗能最小确定第一阶段的侵彻深度,从而得到最小穿透能量的解析解。经与金属装甲弹道试验比较,表明两阶段工程模型计算结果与试验吻合较好,比现有单一延性扩孔模型精度高。     

Perforation experiments on HY-100 steel plates with 4340 Rc 38 and maraging T-250 steel rod projectiles

We conducted perforation experiments with 4340 R_c 38 and maraging T-250 steel, long rod projectiles and HY-100 steel target plates at striking velocities between 80 and 370 m/s. Flat-end rod projectiles with lengths of 89 and 282 mm were machined to nominally 30-mm-diameter so they could be launched from a 30-mm-powder gun without sabots. The target plates were rigidly clamped at a 305-mm-diameter and had nominal thicknesses of 5.3 and 10.5 mm. Four sets of experiments were conducted to show the effects of rod length and plate thickness on the measured ballistic limit and residual velocities. In addition to measuring striking and residual projectile velocities, we obtained framing camera data on the back surfaces of several plates that showed clearly the plate deformation and plug ejection process.     

Ballistic limit for oblique impact of thin sandwich panels and spaced plates

Ballistic perforations of monolithic steel sheets, two-layered sheets and lightweight sandwich panels were investigated both experimentally and numerically. The experiments were performed using a short cylindrical projectile with either a flat or hemispherical nose that struck the target plate at an angle of obliquity. A total of 170 tests were performed at angles of obliquity 0–45°. The results suggest that during perforation by a flat-nosed projectile, layered plates cause more energy loss than monolithic plates of the same material and total thickness. There was no significant difference in the measured ballistic limit speed between monolithic plates and layered plates during oblique impact perforation by a hemispherical-nosed projectile.