电子束对LY12硬铝的损伤效应

对LY12硬铝受到电子束辐照时产生的热激波及材料的损伤破坏效应进行了理论计算,将计算值同实验结果进行比较,二者基本上是一致的。在研究中等能量沉积产生材料的破坏效应时,应适当考虑材料的熔化过程,所用的状态方程是GRAY三相状态方程,而在研究材料的损伤破坏时,我们修正了计及损伤效应的Bodner-Partom本构模型。

LY—12铝高温屈服强度的测量

本文介绍LY-12铝合金在常温至400℃动载下(应变率为 10~3/秒),屈服强度的测试及研究。采用一维Hopkinson压杆实验装置及管式高温炉。利用一维应力波传播理论及应变片直接测量两种方法,得到了LY-12铝合金的屈服强度随温度变化的曲线。

LY12铝疲劳裂纹在冲击载荷下的演化研究

对LY12铝合金在低周疲劳条件下的裂纹情况和随后进行的动态拉伸条件下裂纹的发展给予了观察和统计分析。发现裂纹的累积数密度分布在损伤演化过程中保持指数形式，用NAG模型对实验结果进行分析，得出该材料裂纹演化发展方程的各种参数。

用电子散斑干涉法测量材料热膨胀系数

利用双光束电子散斑干涉法(ESPI)对试件受热变形进行了实时观测,针对一次实验过程中得到的图片较多(300～500幅)的特点,在图像处理时摒弃了以往的手动识别等位移线的办法,用MATLAB语言编写了批处理程序,能够在采集的大量散斑图片中自动快速准确地标定等位移线.得到相应的位移和应变.并结合实时测量的温度值,获得了45钢和LY12铝合金在不同温升率下的热膨胀系数及其随温度的变化.实验结果表明,在涉及的温升率范围内,温升率的改变对材料热膨胀系数的影响不明显.材料的热膨胀系数随温度的升高略有上升.

数字散斑相关法在高速变形测量中的应用

在SHTB加载装置上利用数字化的高速摄影和采集系统,并结合数字散斑相关方法,发展了一种光学动态变形测试技术,在霍普金森(Hopkinson)加载装置上实现了具有较高精度和分辨率的位移和变形场的实时光学测量.实验中,利用Imacon-790高速摄影机以105幅/s的速度分别拍摄了两组LY12试件的动态拉伸情况(一维平板拉伸试样和含对称缺口的拉伸试样),然后运用数字散斑相关方法对其不同时刻的图像进行分析和处理,可以得到试样在各个时间点的位移场.最后利用有限元数值模拟技术与实验结果进行了比较,验证了整个系统以及数字散斑相关方法用于高速动态测量中的可行性.

The Evolution of Fatigue bocks in Aluminum Alloy LY-12 under Shock beading

对LY12铝合金在低周疲劳条件下的裂纹情况和随后进行的动态拉伸条件下裂纹的发展给予了观察和统计分析。发现裂纹的累积数密度分布在损伤演化过程中保持指数形式,用NAG模型对实验结果进行分析,得出该材料裂纹演化发展方程的各种参数。

Electrochemical Impedance Spectroscopy Of Peo Coating On Aluminum Alloy In Nacl Solution

Various Plasma Electrolytic Oxidation (PEO) ceramic coatings were prepared on LY12 aluminum alloy by adjusting the concentration of sodium silicate solution. Optical microscope (OM), XRD and EIS were used to study their morphology, composition and anti corrosion behavior in NaCl solution. Increasing concentration of sodium silicate leads to the increase of the total coating thickness while too high and too low concentration lead to the decrease of inner dense layer. The main composition of PEO coatings prepared in 20, 40 and above 60g/L concentration solution are correspondingly alumina, alumina with mullite, and amorphous phase. The corrosion resistance is determined by the inner dense layer. Increasing the thickness of inner dense layer can improve the anti-corrosion performance. PEO coating's corrosion resistance in acidic, alkaline and neutral NaCl solution is proved and the corrosion mechanism involved is also discussed.

Miner累积损伤理论的试验验证和统计分析

本文通过对LY12-CZ铝合金板材光滑试件和中心孔试件的常幅加载和变幅加载疲劳试验,对Miner累积损伤理论进行了试验验证,并对累积周比的分散性作了统计分析,发现累积周比的分散性服从Weibull分布,因此本文提出以最小累积周比值或以与一定存活率相应的累积周比值进行安全寿命估计的观点。

Dynamic damage and failure in viscoplastic materials

In this paper, a dynamic damage model in ductile solids under the application of a dynamic mean tensile stress is developed. The proposed model considers void nucleation and growth as parts of the damage process under intense dynamic loading (strain rates epsilon greater than or equal to 10(3) s(-1)). The evolution equation of the ductile void has the closed form, in which work-hardening behavior, rate-dependent contribution and inertial effects are taken into account. Meanwhile, a plate impact test is performed for simulating the dynamic fracture process in LY12 aluminum alloy. The damage model is incorporated in a hydrodynamic computer code, to simulate the first few stress reverberations in the target as it spalls and postimpact porosity in the specimen. Fair agreement between computed and experimental results is obtained. Numerical analysis shows that the influence of inertial resistance on the initial void growth in the case of high loading rate can not be neglected. It is also indicated that the dynamic growth of voids is highly sensitive to the strain rates.

Dynamic failure in ductile porous materials

In this paper, a mathematical model of dynamic fracture in porous ductile materials under intense dynamic general loading is developed. The mathematical model includes the influence of inertial effects and material rate sensitivity, as well as the contribution of surface energy of a void and material work-hardening. In addition, the condition of the void compaction is considered as well. The threshold stresses for the void growth and compaction are obtained. A simple criterion for ductile fracture which is associated with material distention and plastic deformation is adopted. As an application of the theoretical model, the processes of two-dimensional spallation in LY12 aluminum alloy are successfully simulated by means of two-dimensional finite-difference Lagrangian code.

The fatigue life estimation of notched specimens under random loading

The LY12-cz aluminium alloy sheet specimens with a central hole were tested under constant amplitude loading, Rayleigh narrow band random loading and a typical fighter broad band random loading. The fatigue life was estimated by means of the nominal stress and the Miner's rule. The stress cycles were distinguished by the rainflow count, range count and peak value count, respectively. The comparison between the estimated results and the test results was made. The effects of random loading sequence and small load cycles on fatigue life were also studied.

铝合金表面等离子体电解氧化陶瓷涂层在NaCl溶液中的电化学阻抗谱研究

通过调整电解液中硅酸钠的浓度，利用等离子体电解氧化（PEO）技术在铝合金LY12表面制备了各种陶瓷涂层，利用光学显微镜、XRD、电化学阻抗谱（EIS）对涂层的形貌、成分和涂层在NaCl溶液中耐腐蚀性能进行了研究．结果表明：提高电解液中硅酸钠的浓度可以使得涂层的总厚度增加，但过高或过低的浓度都会导致致密层厚度的减薄．当浓度为20g／L时，所制备的涂层的成分以氧化铝为主；当浓度为40g／L时，涂层的成分主要是莫来石和氧化铝；当浓度超过60g／L时，涂层的成分主要为非晶相．EIS的研究表明，涂层耐腐蚀性取决于涂层中的致密层，增加致密层的厚度可以提高PEO涂层的耐腐蚀性，在中性、酸性、碱性腐蚀介质中，PEO涂层都显示出对基体良好的保护作用．

Welding of Al alloy plates using a novel high-average-power pulsed CO2 laser

A novel high-average-power pulsed CO2 laser with a unique electrode structure is presented. The operation of a 5-kW transverse-flow CO2 laser with the preionized pulse-train switched technique results in pulsation of the laser power, and the average laser power is about 5 kW. The characteristic of this technique is switching the preionized pulses into pulse trains so as to use the small preionized power (hundreds of watts) to control the large main-discharge power (tens of kilowatts). By this means, the cost and the complexity of the power supply are greatly reduced. The welding of LF2, LF21, LD2, and LY12 aluminum alloy plates has been successfully achieved using this laser. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Welding of Al alloy plates using a novel high-average-power pulsed CO2 laser

A novel high-average-power pulsed CO2 laser with a unique electrode structure is presented. The operation of a 5-kW transverse-flow CO2 laser with the preionized pulse-train switched technique results in pulsation of the laser power, and the average laser power is about 5 kW. The characteristic of this technique is switching the preionized pulses into pulse trains so as to use the small preionized power (hundreds of watts) to control the large main-discharge power (tens of kilowatts). By this means, the cost and the complexity of the power supply are greatly reduced. The welding of LF2, LF21, LD2, and LY12 aluminum alloy plates has been successfully achieved using this laser. (c) 2005 Society of Photo-Optical Instrumentation Engineers.