基于信息公理的FMEA风险评估改进方法

针对传统失效模式影响分析（FMEA）风险优先数（RPN）计算方法存在的误差大、精度低等缺陷,提出了一种基于信息公理的FMEA风险评估分析方法。在传统FMEA风险因子专家评分的基础上,综合考虑了专家意见和风险因子的权重,通过信息公理将不同物理含义的风险因子转化为无量纲的信息量;以此为基础,将风险因子信息量加权求和得到失效模式的信息量,根据失效模式信息量的大小确定失效模式的风险顺序。算例结果验证了方法的有效性和可行性。     

汽车内外饰设计用涂装材料及其工艺研究进展

汽车保有量的快速增长使得消费者对汽车内外饰设计的质量要求不断提高。汽车内外饰设计用涂装材料及其工艺作为影响内外饰设计的重要因素,已经成为当前涂装领域的研究热点。为了更有效把握汽车内外饰涂装材料及工艺的发展规律和方向,满足未来汽车内外饰设计的应用要求,综述了近年汽车内外饰设计用涂装材料及其工艺的国内外研究进展。在涂装材料方面,梳理了汽车内外饰中常用的涂装材料类型、性能、应用特点与不足。重点分析了以聚氨酯、丙烯酸和氟碳为代表的内饰涂装涂料,着重研究了外部底漆、中涂漆和面漆等外饰涂料。在工艺方面,探讨了汽车内外饰涂装各工艺的技术要求及现状,展望了新工艺的研究动态与前景。随着环保政策的日趋严格及环保意识的不断增强,汽车内外饰设计用涂装材料逐渐由溶剂型向改性水性型材料发展,涂装工艺则由高污染和低效率往绿色化和智能化转变。最后,从有助于增强消费者使用体验角度,提出了未来汽车内外饰涂装材料及其工艺改进的主要方向及具体策略。     

两种SPH算法在模拟不可压缩流中的比较

基于二维腔剪切流模型,对弱可压缩光滑粒子流体动力学（WCSPH）和不可压缩光滑粒子流体动力学（ISPH）两种SPH算法进行了对比分析。分别使用了排斥力方法与静态粒子法来设置边界。结果显示：ISPH算法在计算速度场和压力场时,计算精度均较WCSPH算法高;时间步长不像WCSPH算法受声速的限制,计算效率更高。     

Comparative study of rhomboidal mixing sections using the boundary element method

The rhomboidal mixing section is becoming very popular in polymer extrusion to provide distributive mixing. Currently, several different designs are used but the details of the flow behavior and mixing efficiency is not well understood. This information is needed to be able to design and find the most efficient rhomboid geometry. In this research, nine different geometries with various pitches (helix of rhomboids) are analyzed using a three-dimensional boundary element method (BEM). The geometries are compared according to mixing efficiency, pressure and energy consumption. The investigation led to the conclusion that the most effective distributive mixing sections were the ones with neutral rhomboids (pineapple mixer). However, the neutral rhomboidal mixing section consumes the most pressure in the extruder.     

The Modified Manson–Coffin Curve Method to estimate fatigue lifetime under complex constant and variable amplitude multiaxial fatigue loading

This paper investigates the accuracy of the so-called Modified Manson–Coffin Curve Method (MMCCM) in estimating fatigue lifetime of metallic materials subjected to complex constant and variable amplitude multiaxial load histories. The MMCCM postulates that fatigue damage is maximised on that material plane experiencing the maximum shear strain amplitude. In the present investigation, the orientation of the critical plane was determined through that direction along which the variance of the resolved shear strain reaches it maximum value. Under variable amplitude complex load histories, this direction was also used to count the resolved shear strain cycles via the classic Rain-Flow method. Further, the degree of multiaxiality and non-proportionality of the time-variable stress states at the assumed critical locations was directly quantified through a suitable stress ratio which accounts for (i) the mean value and the variance of the stress perpendicular to the critical plane as well as for (ii) the variance of the shear stress resolved along the direction experiencing the maximum variance of the resolved shear strain. The accuracy and reliability of the proposed approach was checked against approximately 650 experimental data taken from the literature and generated by testing un-notched metallic materials under complex constant and variable amplitude multiaxial load histories. The sound agreement between estimates and experimental results which was obtained strongly supports the idea that the proposed design technique is a powerful engineering tool allowing metallic materials to be designed against constant and variable amplitude multiaxial fatigue by always reaching a remarkable level of accuracy. This approach offers a complete solution to the strain based multiaxial fatigue problem.     

Ni—Zn铁氧体的结构和电磁性能的Nd^3＋掺杂效应

采用固相反应法制备Ni0.5Zn0.5Nd2-xFe2-3O4铁氧体,通过X射线衍射仪（XRD）、阻抗分析仪和振动样品磁强计（VSM）对样品的物相、结构和电磁性能进行表征,讨论了Ni0.5Zn0.5NdxFe2-xO4（x=0．002～0．010）铁氧体的结构和电磁性能。结果表明：Nd^3＋掺杂量z〉0．008时,样品中出现了杂相NdFeO3;随着Nd^3＋掺杂量的增加,晶格常数呈现先增大后不变,而密度、介电常数和介电损耗角正切呈现先增大后减小（z=0．008时出现最大值）,但饱和磁化强度呈现逐渐减小（z=0．010时有最小值71．22emu/g）;并且所有样品的介电损耗角正切均出现峰值,表现异常的介电行为。     

关于弧形类缩口件坯料计算模型

在设定金属材料塑性变形前后面积相等的前提下,利用几何关系和初等数学基本知识,导出了圆弧形缩口坯料计算的传统公式,指出了其存在理论依据粗浅、局限而导致精度不高的问题。进而,针对缩口件的典型形状,利用高等数学中的曲线积分方法,推导并提出了建立在金属塑性成形原理中体积不变条件下,能直接反映材料厚度及变化影响的弧形类缩口坯料计算新公式模型。并用算例进行对比分析,验证了新公式的较精确性与实用性。     

电沉积工艺参数对铜箔性能的影响

分别在不同的电流密度、铜离子浓度、聚乙二醇（PEG）添加剂3种工艺参数下,电沉积制备铜箔试样。利用扫描电镜（SEM）、电子万能试验机和高温拉伸机,分析各种电沉积参数对铜箔显微组织和性能的影响。实验结果表明：铜箔的力学性能主要取决于其组织结构;电流密度、铜离子浓度以及添加剂PEG是影响铜箔的力学性能关键因素,三者对铜箔性能的作用机理相似,都是通过改变阴极极化来影响铜箔的电结晶过程,最终导致铜箔显微组织的变化。