钨合金细观参数对其宏观屈服强度的影响

通过细观分析,给出钨颗粒相的形状、组分和两相力学参数对钨合金宏观屈服强度的影响.其中,钨颗粒看作基体上的夹杂,在小变形条件下假设钨颗粒仅发生弹性变形,而钨合金的宏观屈服强度决定于基体相的屈服强度.在该假设基础上,利用Eshelby方法及Mori-Tanake平均应力概念计算分析了不同钨合金材料,特别是不同变形量工艺处理的钨合金材料的宏观屈服强度,计算结果与实验结果基本一致.     

电镀钨合金镀层组织及其耐腐蚀性能研究

主要分析了电镀钨合金镀层质量及其耐H2S-CO2腐蚀性能。通过SEM、EDX和XRD分析发现镀层与基体结合强度较高,但镀层淬火处理时出现龟裂现象,裂纹均匀排布于镀层表面。腐蚀评价表明腐蚀作用只发生在镀层淬火所形成的裂缝部位,造成裂缝内部充满大量腐蚀产物,非裂纹表面未见腐蚀。指出镀钨合金若用于酸性环境,尚需优化配方、降低硬度、增加韧性,此外还应检测基材屈服强度85%拉应力下的镀层应力腐蚀开裂行为。     

电沉积铁镍钨合金性能研究

钨合金沉积机理至今未得到合理的解释.采用循环伏安法研究了柠檬酸铵盐体系中电沉积铁镍钨合金的规律,分析了主盐浓度、pH值、电流密度、温度对铁镍钨合金镀层组分及阴极电流效率的影响.结果表明,在pH值恒定为8的条件下,镀层中钨和铁的含量受各因素影响的趋势是一致的,随溶液中铁盐、钨盐、柠檬酸盐的含量、电流密度及温度的增加而增加;镀层组分受pH值的影响较大,镀层中钨含量值在pH值为6时最大.根据X射线衍射结果可知,铁镍钨镀层随着钨含量的增加,由纳米结构转变为非晶态结构.     

钨合金易断裂面的研究

介绍了易断裂面的几种形成方式,主要研究在冷等静压成型过程中用模具预制缺口法形成的易断裂面对钨合金力学性能的影响,并用有限元ANSYS程序模拟缺口试样拉伸实验,实验结果与模拟结果一致.     

钨合金动态力学性能的三维数值模拟研究

采用数值模拟的方法对钨合金在冲击载荷作用下的动态力学响应进行了研究.运用有限元动力分析程序建立了具有典型微观结构钨合金三维有限元单胞模型,对钨合金在拉伸载荷作用下的动态力学性能进行了数值模拟研究,分析了应变率对其力学性能的影响,给出了不同应变率条件下单胞模型的应力和应变分布云图,在与实验结果对比的基础上验证了该有限元模型的可靠性.     

高比重钨合金研究的新进展

分别从原材料、烧结工艺及其后处理、强韧化和杂质影响等方面较系统地介绍了国内外近十年来在高比重钨合金领域所取得的进展,并从这些方面详细讨论了影响高比重钨合金性能的具体因素。在此基础上对钨合金今后的发展方向提出了意见。     

钎焊参数对钨合金/钢钎焊接头性能的影响

目的研究钎焊温度和保温时间对接头性能的影响。方法在氩气氛围中用AgCu30钎料对钨合金(91WNiFe)与超高强合金钢(DT1900类ASME100)进行钎焊,并对接头进行组织观察和力学性能测试。结果通过改变钎焊温度(780~840℃),发现随着钎焊温度增加,钎焊接头钎缝中的气孔所占体积减少,钎焊接头的剪切强度先增加后减少;通过改变保温时间(0~30 min),发现随着保温时间的增加,钎焊接头钎缝中的气孔所占体积减少,钎焊接头的剪切强度先增大后趋于平缓。结论当钎焊温度为820℃和保温时间为30 min时,钎焊接头的剪切强度达到最大,为107.73 MPa。     

钨、铀合金破片侵彻性能对比数值研究

为研究不同形状钨破片和铀破片的侵彻性能的优劣,在有关试验的基础上通过AUTODYN软件开展了3组Ф7mm钨球侵彻Q235钢板的验证性仿真模拟,模拟结果与实验结果均吻合,由此验证了仿真方法和相关参数的正确性;分别开展了3种不同形状钨、铀合金破片在不同着靶姿态下侵彻10mm厚Q235钢靶的数值仿真.结果表明:在形状和初速均相同的条件下无论以何种姿态着靶,铀破片的侵彻能力都要强于钨破片;无论钨破片还是铀破片,棱角着靶姿态和棱边着靶姿态的立方体破片侵彻能力最佳,圆柱形水平姿态和面着靶姿态的立方形破片侵彻能力最差.     

均质钽2.5钨合金加工工艺研究

采用"锻造+多向轧制"工艺,研究了均质钽2.5钨合金材料在不同方向、不同部位和不同热处理工艺条件下的拉伸性能和显微组织,最终确定了均质钽2.5钨合金的加工工艺。     

液力挤压法制备新型钨合金穿甲弹芯材料技术

采用液力挤压法制备新型钨合金穿甲弹芯材料,较常规钨合金材料变形加工技术相比,其最大优势是仅通过一次变形可使钨合金材料的性能得到大幅度提高.可对现役、在研各口径、各长细比钨合金穿甲弹进行技术改造和移植.为钨合金穿甲弹芯材料的变形加工提供新的有效技术途径.     

注射成形高密度钨合金脱脂工艺的研究

采用石蜡基多组元粘结剂体系,研究了注射成形高密度钨合金喂料的热脱脂工艺参数,包括样品厚度,温度,低温预脱脂和升温速率的。实验表明,当温度小于２５０℃时,脱脂量的对数与厚度的倒数呈比例,在长时间情况下,ＰＷ可以在２５０℃以衣全部脱除。温度,脱脂量和升温速率的撑峭当将导致脱脂缺陷的产生。     

Determination of the state parameters of explosive detonation products by computational inverse method

A computational inverse method is presented to determine the state parameters of Jones-Wilkins-Lee (JWL) equation of explosive detonation products based on cylinder test. In this method, the inverse problem of identifying the JWL parameters is formulated through minimizing the errors of the measured radial displacements on the cylinder surface and those computed by the forward solver. An available numerical model simulated by finite element method is built for the sake of obtaining results using the given JWL parameters. Because of the difference of coordinate systems between experiment and numerical model, it is necessary to conduct the transformation between the two coordinate systems. The sensitivity analysis method is adopted to evaluate the influence of the JWL parameters on the responses and find out the parameters those are suitable to be identified. In order to improve the computational efficiency, radial basis function approximate model is constructed to replace the time-consuming numerical model. In the process of constructing approximate model, the truncated singular value decomposition method is used to deal with the ill-condition of the model. At last, the intergeneration projection genetic algorithm is adopted to identify the parameters. The numerical results demonstrate that the proposed inverse method is potentially available to effectively identify the JWL parameters.     

NiTi合金主动脉支架弯曲变形行为的研究

利用Pro/E和Ansys软件建立了胸主动脉支架轴向柔顺性分析模型,对27种NiTi合金支架的柔顺性进行了模拟分析与实验验证。在此基础上,又进一步系统地分析了弯曲变形时支架结构尺寸变化对中央部位横截面变形行为的影响。结果显示,减少圆周方向上的连接体的数量,增加支撑体的长度或数量,都能够提高支架的柔顺性,但是减少连接体的数量比增加支撑体的长度或数量对支架柔顺性的影响程度要大。支架弯曲变形时连接体的数量对支架中央部位横截面的变形具有显著的影响。     

Applications of linear inverse finite element method in prediction of the optimum blank in sheet metal forming

A linear inverse finite element method has been developed and investigated to predict the optimum blank. To reduce the computation time, the part is unfolded properly on the flat sheet and treated as a 2D problem. This approach is employed primarily to design the optimum blank shape from the desired final shape with the linear formulations. The procedure is based on the minimization of energy for the unfolded elements. Two solution methods, Direct and Newton–Raphson methods have been examined for the solution of nodal displacements in the equilibrium equations. The convergence show high sensitivity to the initial guess for the strain path when assumed to be linear at the first step. Two applied examples are implemented to show the efficiency of this method. In S rail example, the thickness distributions have been compared with experimental analysis after obtaining the optimum blank with Linear IFEM. In circular cup example, the results have been compared with conventional forward incremental method. New calculation of the external forces vector has been displayed. In this calculation, both blank holder force (BHF) vector and in-plane force vector have been shown. Finally, in this approach good agreement was found between the forward incremental and Linear IFEM results.     

用有限元分析和DICM确定纸浆模塑材料弹性常数的逆问题

用有限元法分析纸浆模塑包装结构,需要事先确定纸浆模塑材料的弹性常数.基于纸浆模塑薄壁圆锥筒的压缩试验,讨论了可以利用有限元分析和数字相关测量方法(DICM)来识别纸浆模塑材料弹性常数的逆问题.     

卫星姿态滑模变结构控制的广义逆方法

对于卫星姿态滑模变结构控制问题,文献[1]提出了反馈线性化方法,但在病态情形中给出的确定逆矩阵方法涉及一个参数,如果参数过大,则控制精度较差;如果参数过小,则控制能量消耗较大.针对这一问题本文提出了利用广义逆矩阵求解控制律的方法,这种方法不仅控制精度高,而且能够大幅度地节约控制能量.     

Microstructure and mechanical performance of pulsed current gas tungsten arc surface engineered composite coatings on Mg alloy reinforced by SiCp

A new pulsed current GTA surface-modified process was used to fabricate composite layer on the surface of Mg alloy AZ31. Current pulsing enhances fluid flow, reduces temperature gradients and causes a continual change in the weld pool size and shape, so that it is responsible for refining the solidification structure in the composite layer. The observed grain refinement was shown to result in an appreciable increase in composite layer bend strength. Composite layers with lower scan speed have higher bend strengths and they also seem to have “good” metallurgical bond with the substrate thus showing better mechanical behavior than the other higher scan speeds used in this present study. The wear rate of the composite layer decreases linearly with increase in SiCp volume fraction and the wear resistance of composite layer varies inversely with square of the reinforcement size. Composite layers with higher H/E have smaller accumulative strain, smaller accumulative strain energy, and thus better wear resistance. The wear mechanism was oxidation at low-applied load levels and adhesion/delamination at high-applied load levels.     

基于遗传算法的功能梯度材料参数的反演分析

采用一种基于遗传算法结合响应面插值的反演方法,利用微压痕实验和有限元模拟,对功能梯度材料(FGM)的本构模型参数进行识别分析.此方法首先以解耦的方式对压痕试验进行有限元模拟计算,然后利用三次拉格朗日插值函数构造荷载-位移响应面,并将响应面上插值得到的相关结果传递给遗传算法以实现材料参数的反演辨识.对功能梯度材料参数的反演研究表明:该方法在保证较高精度的同时能够极大地提高常规遗传算法的反演效率;另外,利用大、小压头组合的双压头模式对功能梯度材料进行压痕的反演分析,较之单压头能够获得更为合理的结果.