7A04-T6高强铝合金板对平头杆弹抗侵彻行为的试验与数值模拟研究

为了解高强铝合金对动能杆的抗侵彻性能,在一级轻气炮上开展了直径5.98 mm的平头刚性弹侵彻6mm厚7A04-T6铝合金靶板的打靶试验,撞击速度范围为73.9~446.5 m/s。获得了弹体贯穿靶板后的剩余速度以及靶板的断裂行为,通过拟合初始-剩余速度数据得到了弹道极限。同时,在ABAQUS/Explicit中建立了三维有限元模型对打靶试验进行了数值计算,7A04-T6的力学行为通过Johnson-Cook本构模型和修正的Johnson-Cook断裂准则描述。试验结果表明,7A04-T6高强铝合金靶板在平头弹撞击下发生剪切冲塞,塞块表面有明显裂纹产生,弹道极限为156.0 m/s,剪切冲塞可在撞击速度不低于约0.90倍弹道极限时形成。数值仿真发现,有限元计算可成功再现靶板的剪切冲塞及冲塞表面的断裂;预报的弹道极限为168.8 m/s,比试验结果高约9%;撞击速度不低于0.92倍弹道极限时靶板发生剪切冲塞破坏,与试验结果十分接近。     

结构参数对截锥弹低速正侵彻装甲靶的影响

采用数值模拟和实验研究相结合的方法,对截锥形动能弹低速正侵彻装甲靶作用行为进行了分析,获得了弹头锥角、前级半径和着靶速度对侵彻性能的影响特性,并对目前常用的侵彻理论模型进行了验证。数值模拟结果表明,弹头锥角和前级半径是影响截锥形动能弹侵彻性能的重要因素;着靶速度对侵彻深度和侵彻过载有显著影响,对弹体变形也有一定影响。实验结果与数值模拟结果吻合较好,而侵彻理论模型与实验结果有较大差别,侵彻模型并不适合分析存在一定变形的弹靶侵彻问题。     

易碎钨合金杆侵彻间隔靶的实验与仿真研究

易碎弹在侵彻多层靶板时,会带给前后间隔靶程度不一的破坏。其破坏程度和弹丸初速,弹体易碎特性相关。利用FEM-SPH耦合仿真的方法,在相同工况下,对实验进行了数值模拟,为量化靶板的破坏程度,提出以靶板质量损失率和靶板面积增加率作为评价靶版破坏程度的指标,并求得对应靶板的指标参数,最后将两指标叠加,作为评价靶板破坏程度的破坏指数。比较破坏指数可以证明易碎弹较普通弹对靶板具有明显的破坏作用,且速度越高,破坏程度越大,仿真结果和实验基本一致。     

弹体侵彻混凝土数值模拟失效指标研究

摘要: 利用单个立方体单元压缩和拉伸数值模拟揭示了HJC混凝土模型的抗压,抗拉和损伤特性,将该模型用于模拟Hanchak侵彻试验,采用最大主应变,等效塑性应变和最大拉静水力三种失效模式后得到的残余弹速和靶板破坏现象与试验结果对比后,最大主应变和拉静水失效得到的弹体残余速度误差比等效塑性应变失效要小,等效塑性应变失效得到的靶板表面破坏现象与实验结果也相差较大。 关键词：HJC混凝土模型;数值模拟;失效指标;弹体侵彻;混凝土板     

Kevlar-129纤维复合材料抗侵彻性能数值模拟

采用AUTODYN有限元软件,数值模拟了不同初速度下FSP破片对10 mm厚Kevlar-129纤维复合靶板的侵彻过程,获取了不同初速度下破片侵彻靶板后的剩余速度,计算了芳纶复合靶板的弹道极限,并将该值与弹道测试试验数据进行了对比.此外,研究了破片侵彻纤维复合靶板深度与破片初速度的关系.结果显示,Kevlar-129纤维复合材料弹道极限的数值模拟值与弹道实验测试值相吻合;破片初速度小于320m/s时,破片剩余速度随着破片初速度的增加而减小;破片初速度大于320m/s时,破片剩余速度随着破片初速度的增加而增大;破片初速度小于靶板的弹道极限时,破片侵彻靶板的深度随着破片初速度的增长呈二次函数增长.     

混凝土板在弹体冲击下的响应试验与数值模拟

混凝土板在刚性弹体垂直冲击下，受到侵彻对击穿，本文用有限元数值模拟了这一过程，得到了弹体击穿靶板后的剩余速度，靶板被击穿后形成的开坑区和层裂区的大小以及靶板中未被破坏部分的应力应变值，并与实弹试验结果及其它分析方法得到的结果作了比较，都较接近。     

弹体侵彻陶瓷/金属复合靶板问题的研究

针对弹体侵彻陶瓷/金属复合靶板的问题,将弹体的墩粗变形、陶瓷面板碎裂及陶瓷锥的形成变化和金属背板的变形结合起来,建立了可变形弹体垂直侵彻陶瓷/金属靶板的理论分析模型。利用大型非线性有限元程序LS-DYNA3D,对平头弹侵彻陶瓷/金属复合靶板的问题进行数值模拟,得到了陶瓷/金属复合靶板受弹体侵彻的变形过程。最后给出了典型位置的位移随时间的变化曲线,理论模型分析结果和数值模拟结果与实验结果进行了对比,吻合很好。说明理论分析模型的正确性和数值模拟结果的可靠性,可以为复合靶板的设计提供有利依据。     

大装填比弹侵彻钢筋混凝土实验研究

设计了一种薄壁弹体,采用YOUNG方程预估该弹体侵彻混凝土靶板的侵彻深度,采用SAMPLL程序预估轴向过载.运用LS-DYNA软件分析弹体的侵彻过程,对材料力学性能进行实验研究.通过在φ130 mm气炮上的一系列弹体侵彻钢筋混凝土靶实验,考核了弹体的结构强度和侵彻深度.结果表明:弹体在低速侵彻钢筋混凝土靶板时结构不会发生破坏,300 m/s速度下具备侵彻贯穿600 mm钢筋混凝土层的能力.     

破片着靶点位置对拼接的UHMWPE板抗侵彻性能影响数值研究

UHMWPE板抗侵彻性能优异但在实际使用过程中需切割成一定尺寸后再拼接安装,半穿甲导弹内爆后形成的高速破片侵彻UHMWPE板时弹着点位置具有随机性。利用数值仿真方法研究破片着靶点位置、破片速度、破片长径比对拼接的UHMWPE板抗侵彻性能的影响。结果表明:破片开始侵彻UHMWPE板时,UHMWPE板在弯矩和剪应力共同作用下出现纤维剪切破坏;随着破片继续侵彻,UHMWPE板主要受到弯矩作用发生纤维拉伸断裂破坏并伴随有严重的分层现象;当破片侵彻两块拼接的UHMWPE板速度较低(小于1 000 m/s)时,拼接的UHMWPE板存在明显的抗弹薄弱区,薄弱区域的范围大约为3倍的弹径;当破片侵彻四块拼接板时,可将靶板划分为薄弱,次薄弱及正常区域。考虑到半穿甲导弹产生破片的大小和安装工艺的方便性,认为UHMWPE板拼接安装时,拼接缝两侧10 cm范围内作为抗弹薄弱区域,需要加固。     

蜂窝铝的侵彻实验研究与有限元模拟

目的 研究弹体侵彻蜂窝铝的力学行为。方法 在实验中, 通过轻气炮加速的尼龙弹体冲击蜂窝铝靶体。利用Ansys/LS-DYNA建立了弹体侵彻蜂窝铝的壳单元有限元模型。结果 实验给出了冲击速度为140和167 m/s时弹体的加速度曲线。运用壳单元模型对蜂窝铝的侵彻进行模拟, 得到了弹体的加速度曲线以及蜂窝铝在侵彻过程中的变形图。结论 将模拟结果与实验结果进行了对比, 发现模拟结果与实验结果符合较好, 证明了壳单元有限元模型模拟蜂窝铝侵彻行为的可靠性。     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.