2024－T3铝合金包铝薄板抗疲劳特性DFR截止值的试验研究EI

用一种新的ＤＦＲ概念比较国产和美国产２０２４－Ｔ３铝合金包铝薄板的抗疲劳特性，试验分析认为，在相同试验条件下，两国产２０２４－Ｔ３包铝薄板抗疲劳特性相当，没有显著差异。     

中华人民共和国国家标准批准发布公告

国家质量技术监督局批准以下１１１项国家标准,现予以公布。一九九九年十一月十二日序号国家标准编号国　家　标　准　名　称代替标准号批准日期实施日期１ＧＢ／Ｔ２３２－１９９９金属材料　弯曲试验方法Ｍｅｔａｌｌｉｃｍａｔｅｒｉａｌｓ－ＢｅｎｄｔｅｓｔＧＢ／Ｔ２３２－１９８８１９９９－１１－０１２０００－０８－０１２ＧＢ／Ｔ２３５－１９９９金属材料　厚度等于或小于３ｍｍ薄板和薄带　反复弯曲试验方法Ｍｅｔａｌｌｉｃｍａｔｅｒｉａｌｓ－Ｓｈｅｅｔａｎｄｓｔｒｉｐ３ｍｍｔｈｉｃｋｏｒｌｅｓｓ－Ｒｅｖｅｒｓｅｂｅ…     

铝薄板热顶—电磁铸造成型工艺研究

依据铝薄板的特点，提出了热顶－电磁铸造的基本思想，设计了一套完整的制取铝薄板的热顶－电磁成型系统，测量了电磁场分布，研究了铝薄板热顶－电磁铸造成型条件，经过大量工艺试验确定了液固界面位置，浇注温度，液柱高度和冷却水量等参数，获得了较佳的铸速０－时间曲线，成功地制取了厚２０ｍｍ，高８５０ｍｍ，宽４８０ｍｍ的铝薄板。     

稀土化合物缓蚀剂对Al2024铝合金防护的研究

研究用于Ａｌ２０２４铝合金的稀土化合物缓蚀剂，用来代替铬酸盐化合物。应用铈或镧的化合物，将Ａｌ２０２４铝合金浸入酸铈或醋酸镧的溶液中，当Ｃｅ＾３＋或Ｌａ＾３＋浓度仅５０－１００＊１０＾－６时，放置不同时间，电化学测试表明：浸泡稀土溶液的Ａｌ２０２４合金表面。     

热作模具钢热疲劳性能与铝液腐蚀性能研究

对４Ｃｒ５ＭｏＳｉＶ１钢和３Ｃｒ２Ｗ８Ｖ钢分别进行３ＳＮＣ－ＲＥ共渗加氧化、ＳＮＣ共渗加氧化和ＳＮＣ－ＲＥ共渗等表面处理，并对经处理的试样分别进行了热疲劳性能和铝液腐蚀性能试验研究。     

自生TiCp/2024复合材料熔体挤压组织与力学性能

对自生ＴｉＣｐ／２０２４复合材料采用Ｔ４和Ｔ６两种热处理制度,测试了该材料的σｂ、σｓ、Ｅ和δ。通过ＳＥＭ观察和分析了熔体挤压ＴｉＣｐ／２０２４复合材料的显微组织和断口形貌。结果表明：在Ｔ６状态下ＴｉＣｐ含量为１５ｗｔ％的复合材料的σｂ、σｓ、Ｅ分别达到５４０ＭＰａ、４３０ＭＰａ、９２ＧＰａ,δ为３．２％,断裂形式为韧性断裂,由此可以认为自生ＴｉＣｐ／２０２４复合材料具有优良的综合力学性能。     

基于抗振动疲劳的薄板加筋设计分析

振动是航空薄板常见的载荷形式,通常采用加强筋来减小振动幅度,从而提高薄板寿命.研究薄板的抗振动疲劳加筋方法,探讨加强筋与板的连接方式以及加强筋的布置方向对薄板振动与疲劳的影响机制.首先,基于振动理论和板筋变形协调条件,建立加筋薄板的运动方程.然后,建立铆接、点焊和滚焊连接形式的加筋薄板有限元模型,探讨连接单元的动力学建模方法;在此基础上,研究连接形式和加筋安装方向对薄板结构动力学特性的影响;最后,结合动力响应分析探讨板筋连接方式和加筋安装方向对疲劳寿命的影响.研究结果表明,双向加筋薄板在低频振动时刚度高于单向加筋薄板,双向加筋有利于提高结构抗疲劳强度,铆接单向加筋薄板的振动疲劳寿命最短.     

1-苯基-5-巯基-1.2.3.4-四氮唑的化学照相特性分析及合成方法的研究

本文介绍了１－苯基－５－巯基－１，２，３，４－四氮唑的化学特性和照相特性；评价了分析测定了ＰＭＴ纯度的方法；了ＰＭＴ五种不同的合成路线，并对较有实际意义的有方法用实际加以验证。     

复合材料中启裂的微观力学分析与实验观察

建立了一个非连续体增强金属基复合材料微观单元的力学分析模型，并以此分析计算了复合材料中不同位置处的受力和断裂临界条件，对１５ｖ％ＳｉＣｐ／２０２４Ａ１，３．６ｖＣＦｓ／２０２４Ａｌ和４－５ｖ％ＣＦ－ｓ／６０６１Ａｌ的实验观察表明，该模型完全适全于金属基复合材料微区力分析，查判断裂纹萌生位置及临界条件。     

Co基复合镀层对3Cr2W8V钢热疲劳性能的影响

利用自约束热疲劳试验方法，研究了在３Ｃｒ２Ｗ８Ｖ钢表面上沉积Ｃｏ－Ｃｒ２Ｏ３－，Ｃｏ－Ａｌ２Ｏ３及Ｃｏ－ＣａＦ２复合镀层对钢热疲劳性能的影响。结果表明：Ｃｏ－Ｃｒ２ｏ３及Ｃｏ－ＡｌＯ３复合镀层都在不同程度上提高钢的热疲劳抗力，而Ｃｏ－ＣａＦ２则降低钢的热疲劳抗力。     

Elastoplastic deformation of dissimilar-alloy adhesively-bonded tailor-made blanks

A combined experimental–numerical study of tailor-made blanks (TMBs) with dissimilar alloys is presented in this paper. The selected adhesive is AF163-2 K (from 3 M). Metal sheets are made from two dissimilar aluminum alloys, namely 2024-T3 and 7075-T6. The 7075-T6 sheet acts as a base sheet on top of which a 2024-T3 sheet is bonded. While the thickness of the base sheet (7075-T6) is the same (=2.0 mm) for all specimens, the thickness of the upper sheet (2024-T3) varies between 0.5 mm and 2.5 mm. The bonded sheets are machined to the standard dog bone shape. In addition, a thickness difference either perpendicular to the loading direction (transverse specimens) or parallel with it (longitudinal specimens) is created by milling. The tensile tests are conducted, while measuring the three-dimensional deformations of the sheets using digital image correlation technique. It is shown that, in contrast with the TMBs with similar-alloys (both sheets made from 2024-T3), the upper sheet does not delaminate during the test. The failure mode is therefore metal fracture. This is an important conclusion, because it improves the in-plane straining limits of adhesively-bonded TMBs. A Finite Element Method (FEM) model of the tensile tests is created. The adhesive damage and metal failure are, respectively, modeled using cohesive interface and distributed continuum damage theories. It is shown that the FEM model can explain the behavior observed in the experiments. The lower ductility of the base sheet together with competition between two failure mechanisms, namely metal failure and delamination, are found responsible for the observed behavior.     

电脉冲对2024 铝合金力学性能的影响

目的研究电脉冲辅助作用下铝合金板材的力学性能。方法通过直流电脉冲辅助单向拉伸实验,研究25 Hz频率下,不同电流密度脉冲电流对2024-T4态铝合金的力学性能的影响规律。结果在所通频率及电流密度脉冲电流作用下,随着脉冲电流密度的增加,2024-T4铝合金板延伸率和流变应力均减小,说明所采用参数脉冲电流辅助可以起到降低成形载荷的目的,但不利于提高材料成形极限。结论 25 Hz频率下脉冲电流辅助不利于2024铝合金的塑性提高,却可降低材料的成形载荷,且塑性、成形载荷随电流密度的增加而降低。     

Fatigue property of semisolid A357 aluminum alloy under different heat treatment conditions

Effect of heat treatment conditions on fatigue property of a semisolid A357 aluminum alloy under cyclic tensile loading was investigated. Comparison of the fatigue property of the semisolid A357 under T5 and T6 heat treatment conditions with other aluminum alloys including conventional casting A357-T6 alloy and four wrought aluminum alloys: 2024-T4, 7075-T6, 5052-T6 and 6061-T6 was made. It is found that the fatigue strength of the semisolid A357 under both heat treatment conditions is much higher than that of the casting A357-T6 alloy, comparable to that of the 6061-T6, but lower than that of the 2024-T4 and 7075-T6. Two-parameter Weibull distribution of fatigue data for the semisolid A357 under the two heat treatment conditions was constructed to show the statistical significance in fatigue lifetime. Fatigue fracture surface of the semisolid A357 under T5 and T6 heat treatment conditions was examined using scanning electron microscope (SEM). In the stable crack propagation region, the semisolid A357-T5 shows fatigue damage species of severely deformed grains, void coalescence, striations and ridgelines, while the A357-T6 displays less plastic deformation as revealed by the fatigue damage features of intergranular cracks, and transgranular cleavage patterns.     

Self-assembled monolayer of 3-aminopropyltrimethoxysilane for improved adhesion between aluminum alloy substrate and polyurethane coating

A good adhesion between a polymer coating and a metal or metal alloy substrate such as Al 2024-T3 plays a critical role in corrosion protection of metal substrates. In our study, a self-assembled monolayer film of 3-aminopropyltrimethoxysilane was formed on Al 2024-T3 substrate by covalent bonding. The adhesion property of a self-priming polyurethane coating was evaluated by pull-off adhesion test, wet tape test and thermal cycling test. All the testing results indicate that both dry and wet adhesion properties of the polyurethane coating were improved significantly after APS treatment of Al 2024-T3 in polar solvents such as methanol and acetone. In nonpolar solvents such as hexane, the APS treatment led to inconsistent improvement or sometime decreased adhesion of polyurethane coating. X-ray photoelectron spectroscopic study revealed that while a monolayer film was formed on the aluminum alloy surface after treating the substrate with APS in methanol and acetone, a multilayer film was formed on the substrate surface when the treatment was conducted in hexane. The APS monolayer film served as a covalent bond linkage between polymer coating and aluminum alloy substrates, which led to the increased adhesion property of polymer coating and corrosion resistance of the metal alloy substrate.     

定量研究2024-T351铝合金搅拌摩擦焊过程中的时效相行为

采用差示扫描量热法研究了2024-T351铝合金搅拌摩擦焊接过程中时效相回溶或粗化的相对值,给出了一种定量研究搅拌摩擦焊接过程中时效相行为的方法.结果表明:相对于母材,焊缝不同区域时效相的回溶或粗化值可通过公式f=Sx/SBM-1来计算;当搅拌摩擦焊搅拌头转速为700r·min-1,焊接速度为200mm·min-1时,...     

2024-T3铝合金动力学实验及其平板鸟撞动态响应分析

通过电子万能试验机和分离式霍普金森拉杆（SHTB）拉伸试验分别获得2024-T3铝合金材料准静态和高应变率两种应变率下的应力-应变曲线。铝合金材料的本构关系由能够反映材料硬化效应和应变率强化效应的Johnson-Cook材料模型描述,方程中的4个参数通过不同应变率下的应力-应变曲线拟合得到。基于瞬态动力学软件PAM-CRASH,结合材料动态力学性能试验所获得的2024-T3铝合金Johnson-Cook模型方程,耦合光滑粒子流体动力学（SPH）方法和有限元（FE）方法建立2024-T3铝合金平板的鸟撞数值模型,数值计算所得动态响应与鸟撞试验结果吻合较好,表明建立的鸟撞数值计算模型是合理、可靠的,整个分析流程从材料动态力学性能试验、鸟撞数值计算到最终的鸟撞试验验证为飞机结构的抗鸟撞设计与分析提供了有力的参考。     

Variation of the cyclic strain-hardening exponent in advanced aluminium alloys

The cyclic strain-hardening exponents for five fatigue-resistant aluminium alloys were determined throughout the fatigue life to study the degree of cyclic stability of these alloys. Data were compared with results for 2024-T4 aluminum and for two high-pressure steels. The strain-hardening exponent increased logarithmically in all cases except 2024-T4, although the increase was small and did not exceed 33% over the fatigue life. 7475-T351 aluminium alloy was found to be entirely stable, and 7075-T7351 almost so. These were followed in order of rising sensitivity by 2014-T6, 7050-T73651, and 2124-T851 aluminium alloys, and 28NiCrMo7.4 and 30CrNiMo8 steels. 2024-T4 aluminum alloy demonstrated a strong decrease in strain-hardening exponent with fatigue life.     

Fracture of laminates combining 2024-T3 and 7075-T6 aluminum alloys

Crack growth resistance curves have been determined for crack-divider laminates in which layers of 2024-T3 aluminum alloy are adhesively bonded to layers of 7075-T6 alloy. Results are compared with the fracture resistance of laminates consisting wholly of each material, the layer thickness being the same (1.54 mm) in all cases. The initial portions of the resistance curves are similar for both alloys; however those for 2024-T3 have steeper slopes at longer effective crack lengths. As a result, laminates consisting entirely of 2024-T3 alloy exhibit greater amounts of stable crack extension and higher toughnesses at instability. This is attributed in part to the greater strain hardening rate in 2024-T3 material. Laminates combining 2024-T3 and 7075-T6 layers are intermediate between those consisting entirely of one or the other alloy.     

Variations of various fracture parameters during the process of subcritical crack growth

The process of subcritical crack growth in a center-cracked specimen made of 2024-T3 aluminum alloy has been analyzed by finite element method. The variations of various fracture parameters in the process of crack growth are presented. A preliminary discussion is made about the general guidances in formulating the governing equation for crack growth.     

Multiple fatigue crack growth in pre-corroded 2024-T3 aluminum

Previous studies of fatigue crack growth in corroded aluminum have revealed that multiple crack-nucleating corrosion features often lead to the failure of individual test specimens. In the present work, this phenomenon was explored by performing quantitative fractography on forty 2024-T3 sheet aluminum fatigue specimens. Slightly over half of the specimens were found to have two or more crack-nucleating pits. The number of nucleating pits per specimen was found to be positively correlated with stress level, and an interactive effect with corrosion exposure duration was observed. A fracture mechanics-based model was developed to simulate the observed multiple crack growth process. Flaw interaction effects were investigated and the importance of modeling multiple crack growth at high stress levels was seen.