On a class of multiple failure mode systems

The primary objective of this work is to introduce and perform a detailed study of a class of multistate reliability structures in which no ordering in the levels of components' performances is necessary. In particular, the present paper develops the basic theory (exact reliability formulae, reliability bounds, asymptotic results) that will make it feasible to investigate systems whose components are allowed to experience m ≥ 2 kinds of failure (failure modes), and their breakdown is described by different families of cut sets in each mode. For illustration purposes, two classical (binary) systems are extended to analogous multiple failure mode structures, and their reliability performance (bounds and asymptotic behavior) is investigated by numerical experimentation. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 167–185, 2002; DOI 10.1002/nav.10007     

When to commit in a serial supply chain with forecast updating

Negotiations between an end product manufacturer and a parts supplier often revolve around two main issues: the supplier's price and the length of time the manufacturer is contractually held to its order quantity, commonly termed the “commitment time frame.” Because actual demand is unknown, the specification of the commitment time frame determines how the demand risk is shared among the members of the supply chain. Casual observation indicates that most manufacturers prefer to delay commitments as long as possible while suppliers prefer early commitments. In this paper, we investigate whether these goals are always in the firm's best interest. In particular, we find that the manufacturer may sometimes be better off with a contract that requires an early commitment to its order quantity, before the supplier commits resources and the supplier may sometimes be better off with a delayed commitment. We also find that the preferred commitment time frame depends upon which member of the supply chain has the power to set their exchange price. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2003     

SFPB处理的38CrSi钢表面纳米化层微观结构特征

采用超音速轰击技术（Supersonic Fine Particles Bombarding,SFPB）对调质态合金钢38CrSi进行表面纳米化处理,在材料表面制备了纳米结构表层;利用X射线衍射、扫描电镜和透射电镜等分析技术研究了表面纳米层的微观结构特征。结果表明：经SFPB处理后,材料表层发生了严重的塑性变形,表面形成了晶粒尺寸约为15nm的纳米结构层,微观应变约为0．19％;表面纳米层的厚度约为20μm（晶粒尺寸〈100nm）,纳米晶粒的尺寸随着距表面距离的增加而增大;在距表面40μm的范围内,高密度的位错墙和位错缠结将晶粒分为了尺寸为200～400nm的胞块结构,分析表明表面纳米化主要是位错运动的结果。     

型钢混凝土桁架节点有限元分析

由于普通结构设计软件无法实现型钢混凝土空间桁架节点内部细化计算分析,为解决这一问题,通过采用ANSYS软件对整体结构进行静力分析,并提取桁架节点处各构件的内力,将其施加于桁架节点的实体模型,进行精细的有限元计算分析;检验桁架节点实体模型内部应力是否满足强度要求,验证结构设计时节点区域的型钢选取和配筋的合理性;同时将分析结果与在该结构施工现场实际检测结果进行对比。结果表明,AN—SYS软件能够准确地完成普通结构设计软件无法完成的复杂结构模型的细化有限元分析。     

喷丸强化对18Cr2Ni4WA渗碳钢性能的影响

采用强力喷丸工艺对渗碳18Cr2Ni4WA钢试样进行了表面喷丸强化处理。利用Nano Test 600纳米测试仪、2903X射线应力仪和TR200表面粗糙度仪,分别测试分析了试样处理前后的显微硬度、残余应力和表面粗糙度,并在JP-52接触疲劳试验机上考察了喷丸强化处理对渗碳18Cr2Ni4WA钢接触疲劳性能的影响。试验结果表明：渗碳试样经强力喷丸后,在0～0．50mm深的表层内形成一个喷丸硬化层,显微硬度提高了约1．1GPa;最大残余压应力由-478 MPa提高到-760 MPa;表面粗糙度由1．255μm降为0．979μm。接触疲劳特征寿命以与中值寿命L50均提高了2倍多,额定寿命L10提高了1倍多。     

细水雾灭火系统在钢铁冶金企业的应用研究

根据大量的模拟钢铁冶金企业的实体火灾的试验数据和工程设计经验,提出细水雾灭火系统的消防解决方案,并对该系统在实际应用过程中所可能出现的问题进行了专项研究,提出应对措施。     

Effects of material of metallic frame on the penetration resistances of ceramic-metal hybrid structures

The effects of metallic material on the penetration resistances of ceramic-metal hybrid structures against vertical long-rod tungsten projectiles were studied by artillery-launched experiments and numerical simulation. Hybrid structures with rectangular cores in transverse orthogonal arrangement and slide-fitting ceramic inserts of zirconia toughened alumina prisms were fabricated with titanium alloy TC4 (Ti6Al4V), AISI 4340 steel and 7075 aluminum alloy panels, respectively. The results showed that the hybrid structure of Ti6Al4V exhibited the highest penetration resistance, followed by that of 7075 aluminum alloy with the same area density. The penetration resistance of the hybrid structure of AISI 4340 steel was the lowest. The underlying mechanisms showed that the metallic material of a ceramic-metal hybrid structure can directly affect its energy absorption from the impact projectile, which further affects its penetration resistance. Different metallic frames exhibited different failure characteristics, resulting in different constraint conditions or support conditions for ceramic prisms. The high penetration resistance of the Ti6Al4V hybrid structure was due to its stronger back support to ceramic prisms as compared with that of AISI 4340 steel hybrid structure, and better constraint condition for ceramic prisms by metallic webs as compared with that of 7075 aluminum alloy hybrid structure. The results of mass efficiency and thickness efficiency showed that the Ti6Al4V hybrid structure has advantages in reducing both the thickness and the mass of protective structure. In addition, because the ceramic-metal hybrid structures in the present work were heterogeneous, impact position has slight influence on their penetration resistances.     

Effect of bending temperatures on the microstructure and springback of a TRIP steel sheet

Transformation-induced plasticity (TRIP) steel possesses high strength and formability, enabling the use of a thinner gauge material and allowing for the fabrication of complex shapes. In this research, we measured the effect of bending temperatures on the microstructure and air-bending springback angle of TRIP steel at temperatures from 25 to 600 °C. Real-time in situ X-ray diffraction and scanning electron microscopy were used for pre- and postbending analysis. As the prebending temperature increased from 25 °C to 600 °C, the retained austenite (RA) volume fraction decreased, and the RA transformed to bainite at temperatures above 400 °C. The springback angle was positively correlated with the prebending RA volume fraction, with the smallest springback angle achieved at 400 °C. Additionally, the springback angle was positively correlated with the bending angle, because the RA transformation ratio contributed to increased strain hardening. Further microstructure analysis revealed that the RA became elongated in the tension direction as the bending temperatures increased.     

大型复合材料空间刚架缩比模型设计方法

缩比模型试验是获取大型复合材料空间刚架力学特性或响应的一种有效途径,其中一项重要内容是缩比模型设计。以大型复合材料空间刚架为研究对象,阐述已有传统方法的局限性;基于离散相似提出结合有限元方法的方程分析法,利用该方法推导大型复合材料空间刚架静力学响应和动特性的相似关系;利用所提方法设计某复合材料龙骨的1/5缩比模型,并通过试验进行验证。验证结果表明,所提方法和推导的相似关系能够用于指导大型复合材料空间刚架的缩比模型试验。     

基于1553 B总线的半实物仿真系统

1553 B总线在半实物仿真系统中得到了广泛的应用。通过研究半实物仿真原理及1553 B总线协议,设计了1553B总线控制器与远程终端软件,提出了一种能很好地节省总线资源的消息帧设计方法。通过实例讨论了基于1553 B总线的半实物仿真系统的建模方法。