Thermal Shock Failure in Thick Epoxy Coatings

In this paper we describe an apparatus for reproducibly measuring thermal shock resistance of thick polymer layers bonded to metals. The thermal shock behavior is discussed in terms of epoxy samples bonded to an aluminum substrate. It was found that both high resin toughness and low resin thermal expansion coefficient improved thermal shock resistance of thick coatings, but only a sample containing 60wt. % glass beads did not develop a failure crack. Effects of sample thickness, temperature gradient, and resin composition on thermal shock behavior are discussed.     

整流器故障原因分析

介绍了隔膜碱整流装置发生的整流器故障的经过，并对事故进行了分析，进而提出了类似事故的预防措施。     

Relationship between Viscoelastic and Peeling Properties of Model Adhesives. Part 1. Cohesive Fracture

The viscoelastic and peeling properties of polybutadiene/tackifying resin compatible blends have been studied in detail. Viscoelastic properties have been described through the variations of the complex shear modulus, G*(ω), as a function of frequency, ω and peeling properties through the variations of peeling force (F) as a function of peeling rate (V).

After showing the objective character of the peeling curves obtained, the variations of the peeling force and peeling geometry have been studied as a function of volume fraction of the tackifying resin.

In this first paper, the analysis is focused on the first domain of the peeling curves, i.e. the cohesive fracture region. In this region, the peeling properties have been related to the viscoelastic properties in the terminal region of relaxation. It is shown that the longest relaxation time, τ_o, is a reducing parameter of the peeling curves, so a peeling master curve-which is independent of temperature, resin volume fraction and polymer molecular weight-may be defined. Furthermore, the variations of the test geometry as a function of peeling rate have been investigated: the variations of the radius of curvature of the aluminium foil have been analyzed with respect to the viscoelastic behavior of the adhesive, which in fact governs the test geometry.

A detailed analysis of all these features leads to a model which allows one to calculate the peeling curves in the cohesive domain from the adhesive formulation.     

State space model predictive fault-tolerant control for batch processes with partial actuator failure

This paper presents a state space model predictive fault-tolerant control scheme for batch processes with unknown disturbances and partial actuator faults. To develop the model predictive fault-tolerant control, the batch process is first treated into a non-minimal representation using state space transformation. The relevant concepts of the corresponding model predictive fault-tolerant control is thus introduced through state space formulation, where improved closed-loop control performance is achieved even with unknown disturbances and actuator faults, because, unlike traditional model predictive fault-tolerant control, the proposed control method can directly regulate the process output/input changes in the design. For performance comparison, a traditional model predictive fault-tolerant control is also designed. Application to injection velocity control shows that the proposed scheme achieve the design objective well with performance improvement.     

The effect of the third invariant on the strength and failure of boron carbide and silicon carbide

This article presents new test data to assess the effect the third invariant has on the strength and failure of two ceramic materials: boron carbide and silicon carbide. Two experimental techniques are used: the Brazilian test that produces a biaxial state of stress, and a new technique that uses a high-pressure confinement vessel to load a specially designed dumbbell specimen in triaxial extension. The dumbbell geometry provides two important advantages over the typically used cylindrical specimen: no adhesive is required to bond the specimen to the load cell because the dumbbell geometry naturally takes the specimen into tension, and any loading asymmetries are essentially eliminated due to the axisymmetric geometry. The results show that when the stress state is on the tensile meridian the equivalent stress at failure is constant, independent of the hydrostatic pressure. The average equivalent stress at failure is for boron carbide and for silicon carbide. The Brazilian test was only performed on boron carbide and failed at , much higher than when on the tensile meridian () indicating that the effect of the third invariant is significant (because of the difference in the failure strength) and must be accounted for to accurately predict when failure will occur.     

单向Cf/SiC复合材料的弯曲疲劳性能

对单向Cf/SiC复合材料进行了三点弯曲疲劳性能测试,得到了复合材料的应力－寿命曲线（S－N曲线）,并对其进行线性拟合,得到疲劳最大应力与复合材料疲劳寿命的关系;考察了疲劳过程中刚度下降和疲劳裂纹产生情况。结果表明在疲劳过程中复合材料的弯曲模量有3个变化阶段：首先在疲劳加载初期,弯曲模量的下降速度及幅度都较大;其次在弯曲模量下降到原始弯曲模量的85％（133GPa)后,其变化方式没有明显的规律可循,有时甚至可能上升;最后复合材料发生疲劳断裂时,模量将发生突变。显微结构分析表明：基体横向裂纹群的产生是疲劳断裂的独有特征。它的产生是由于基体SiC的断裂应变小于碳纤维的断裂应变,基体首先开裂并导致应力重新分布的结果。     

Failure load prediction of structural adhesive joints : Part 2: Experimental study

The objective of this study was to determine how the fracture of adhesive joints depends on elastic beam parameters describing the adherends and the applied loads. The basic specimen geometry was the cracked lap shear joint constructed of aluminium alloy with various adherend and bondline thicknesses. Loads were applied in different combinations of bending, tension and shear to generate a failure envelope for each adhesive and specimen geometry. It was found that crack propagation for precracked specimens occured at a critical strain energy release rate but was also a function of the G_I/G_II ratio and the bondline thickness. The experiments also showed that the loads required to propagate a crack in a precracked specimen were always lower than the loads required to break the fillet. Hence, by treating uncracked joints as being cracked, where the fictitious crack tip is assumed to coincide with the location of the fillet, a conservative estimate of the failure load is obtained.     

石灰乳输送泵的失效分析与优化设计

结合某水泵厂提供的石灰乳输送泵的设计资料,根据试制的离心渣浆泵出现的失效现象,分析失效原因,研究改进方法,为低比转数离心渣浆泵的设计提出优化设计意见。     

一种线性时间复杂度的高效路由保护方法

如何高效快速地应对网络中的故障是设计路由协议的基本要求和主要任务。由于动态路由协议在应对网络中的故障时,在协议动态收敛的过程中将会有大量的报文被丢弃。因此,目前路由器厂商普遍采用路由保护方法来克服网络故障,在众多的路由保护方法中,DC（downstream criterion）规则是一种被普遍认可的方法。然而,已有的实现 DC规则算法的时间复杂度普遍较高,并且复杂度随着网络节点平均度的增加而迅速增加。为了应对上述问题,提出一种线性时间复杂度的高效路由保护方案ERPLR（an efficient routing protection method with linear time complexity）,该方法首先提出了备份下一跳计算规则,然后在已有最短路径树的基础上,根据备份下一跳计算规则为所有的源目的节点对计算备份下一跳。在计算备份下一跳的过程中,每个节点和其邻居最多被访问一次,因此ERPLR的时间复杂度为O（V+E）。实验结果表明,与已有的实现DC规则相比较,ERPLR在故障保护率和路径拉伸度两个度量指标结果相似的情况下,在真实网络拓扑和模拟拓扑中,ERPLR分别降低了大约74.93%和78.91%的计算开销,该方法可以极大地降低DC规则的计算开销。     

考虑邻近建筑物影响的内撑式排桩基坑支护局部破坏研究

基坑开挖与周围环境相互影响,而邻近建筑物对基坑支护体系局部破坏的影响鲜有研究。通过内撑式排桩支护砂土基坑模型试验,研究了坑外有、无建筑物两种情况下基坑开挖、支撑局部破坏和桩后砂土渗漏对内撑式排桩基坑支护体系受力及变形性能的影响。试验结果表明：受邻近建筑物的影响,随基坑逐渐开挖,平行于邻近建筑物长边的支护桩桩顶水平位移增大,而垂直于邻近建筑物长边的支护桩桩顶水平位移减小,同时基坑中部内支撑轴力明显增大,角撑次之,边撑反而减小;邻近建筑物对平行于建筑物长边的支护桩桩身弯矩及反弯点影响较大,而对垂直于建筑物长边的支护桩桩身弯矩影响较小;局部内支撑破坏引起的坑外地面沉降较小,而内支撑连续破坏导致坑外地面产生显著沉降,影响范围为0.12~0.23倍开挖深度,同时临近的未失效支撑轴力显著增大,易引发连续破坏;邻近建筑物对平行于建筑物长边的支护桩桩身弯矩影响较大,对垂直于建筑物长边的支护桩桩身弯矩影响较小。当桩后砂土出现渗漏时,对平行于邻近建筑物长边的支护桩影响更为明显。