K_2NbOF_5－MF_3系玻璃的结构及电性质

研制了Ｋ＿２ＮｂＯＦ＿５－ＭＦ＿３（Ｍ＝Ａｌ、Ｇａ）新体系氟化物玻璃，测定了玻璃的特征温度、Ｒａｍａｎ光谱和电导率，玻璃中Ｎｂ￣（５＋）、Ａｌ￣（３＋）、Ｇａ￣（５＋）分别以ＮｂＯＦ、ＡＩＦ、ＧａＦ八面体形式存在，玻璃的电导率随ＡｌＦ＿３含量的增加而增加，ＡｌＦ＿３含量达到３０ｍｏｌ％时，Ａｌ￣（３＋）除ＡＩＦ八面体外，还有ＡｌＦ四面体结构出现，同时电导率降低，Ｆ￣－阴离子是主要的导电离子，７５Ｋ＿２ＮｂＯＦ＿５·２５ＡｌＦ＿３玻璃的电导率在１９６℃时，σ＝１．０２×１０￣（－２）Ｓ·ｃｍ￣（－１）。     

二价离子替代的Nasicon及其应用研究

含二价阳离子的Ｎａｓｉｃｏｎ，Ｍ￣（２＋）Ｎａｓｉｃｏｎ（Ｍ＝Ｍｇ、Ｃａ、Ｓｒ、Ｚｎ）可由母体Ｎａ＿３Ｚｒ＿２Ｓｉ＿２ＰＯ＿（１２）（Ｎａｓｉｃｏｎ）为起始原料与相应的二价离子的盐浓液或熔盐进行离子交换而制得。Ｘ射线衍射分析结果表明离子交换后的产物Ｍ￣（２＋）－Ｎａｓｉｃｏｎ大多保持原母体的Ｃ＿（２／ｃ）结构。交流阻抗技术测定的电导率数据显示含不同的二价替代离子的Ｎａｓｉｃｏｎ的电导率相差甚大。其中最好的是Ｍｇ￣（２＋）－Ｎａｓｉｃｏｎ，其电导率在４００℃时可达到１．４８×１０￣（－２）Ｓ／ｃｍ。Ｍｇ￣（２＋）－Ｎａｓｉｃｏｎ用作微功率固态电池Ｍｇ／ＣｕＣｌ的电解质，该电池的开路电压为２．０７Ｖ，短路电流为１ｍＡ。平均放电电压为１．６Ｖ，电池的放电容量是３．４ｍＡＨ。     

多元线性超结构关系模型参数估计的大样本性质

讨论了如下线性超结构关系模型βｘｋ＋α＝０，ζｋ＝ｘｋ＋εｋｋ＝１，２，．．．ｎ，（εｋ，ｋ＝１，２，．．．ｎ）ｉ，ｉ，ｄ，Ｅ（ε１）＝０，Ｖａｒ（ε１）＝σ＾Ｉｍ其中（ｘｋ，ｋ＝１，２，．．．．，ｎ）为相互独立的ｍ维ｒ．ｖ．列，且和随机误差（ε，ｋ＝１，２，．．．．，ｎ）相互独立，在一定条件下，证明了ＬＳ估计量β，α，σ＾２的强相合性，唯一性，并给出了估计量的一类ａ．ｓ．收敛速度０（ｎ＾－１／２     

机会约束规划问题的最优解

本文讨论了机会约束规划ｍｉｎ［ｃｘ│Ｐ（Ａｉｘ≥ｂｉ）≥ｐｉ（ｉ＝１，……，ｒ），Ｄｘ≥ｄ］最优解的存在性，其中仅Ａｉ是随机的，Ａｉ是ｎ维正态随机向量，我们给出了这一机会约束规划存在最优解的充分条件，当Ａｉ－Ｎ（ｏ，σｉＩ）（ｉ＝１，……，ｒ）时，我们还给出了机会约束规划ｍｉｎ［ｃｘ│Ｐ（Ａｉｘ≥ｂｉ）≥ｐｉ，ｉ＝１，……，ｒ］的最优解。     

环十二酮肟在硫酸中热效应

使用ＲＤ－１型热导式自动量热计测量了不同温度下环十二酮肟在９８％硫酸中热效应。结果表明：当Ｔ＜３３３Ｋ时，仅产生溶解热效应，３０３Ｋ下溶解热△Ｈ＿（ｓ，ｍ）＝－５１．７ｋＪ·ｍｏｌ￣（－１）（ｍ＝４．２８５ｍｏｌ·ｋｇ￣（－１））；当Ｔ＞３４３Ｋ时发生环十二酮肟重排反应，３９３Ｋ下反应热△Ｈ＿（Ｒ，ｍ）＝－２３１．８ｋＪ·ｍｏｌ￣（－１）（ｍ＝４．９６×１０￣（－３）ｍｏｌ·ｋｇ￣（－１））和△Ｈ＿（Ｒ，ｍ）＝－２３７．０ｋＪ·ｍｏｌ￣（－１）（ｍ＝１．７×１０￣（－２）ｍｏｌ·ｋｇ￣（－１））。     

具有连续分布时滞模型的稳定性分析

Ｌｙａｐｕｎｏｖ泛函方法讨论了具有连续分布时滞神经网络模型ｘｉ（ｔ）＝ｂｉｘｉ（ｔ）＋（ｎ）∑（ｊ＝１）ａｉｊｆｊ（μｊ∫－∞ｋｉｊ（ｔ－ｘ）ｘｊ（ｓ）ｄｓ）＋Ｆｉ（ｔ），ｉ＝１，２，…，ｎ平衡点的稳定性，获得了一些新的充分条件。     

多冲疲劳裂纹萌生期的测定和应力场强度因子KI的计算

冲击疲劳裂纹长度ａ和冲击周次Ｎ的关系可表示为：Ｎ＝ＮＡ－Ｃ’（Ｗ－ａ）＾ｎ１。由此式可精确计算出裂纹萌生寿命Ｎｏ和裂纹扩展速度ｄａ／ｄＮ。     

M－矩阵的行列式不等式

我们首先把文献［２］的结果：ｄｅｔＡｄｅｔＢ≤ｄｅｔｍ（Ａ＊Ｂ）改进为（ｂ１１…ｂｎｎ）ｄｅｔＡ＋（ａ１１…ａｎｎ）ｄｅｔＢ－（ｄｅｔＡ）（ｄｅｔＢ）≤ｄｅｔｍ（Ａ＊Ｂ），其中Ａ，Ｂ为ｎ阶Ｍ－矩阵，“＊”记Ｈａｄａｍａｒｄ积，“ｍ”记比较矩阵。其次，把关于Ｍ－矩阵的Ｈａｄａｍａｒｄ不等式改进为ｄｅｔＡ≤ａ１１…ａｎｎ－｜ａ１σ（１）…ａｎσ（ｎ）｜，其中σ是１，２…ｎ的任一个置换，当ｎ为奇数时，它为偶置换，否则为奇置换。最后，对Ｂ为非奇异的情形给出下列估计式：ｄｅｔＡ≤ｄｅｔ（Ａ＊Ｂ－１）／（β１１…βｎｎ）≤ａ１１…ａｎｎ，和ｄｅｔＡ／ｄｅｔＢ≤ｄｅｔ（Ａ＊Ｂ－１），其中，βｉｉ为Ｂ－１的主对角元     

立方A^4＋M^5＋2O7型化合物与新型负热膨胀材料

概述了立方Ａ＾４＋Ｍ＾５＋２Ｏ７型化合物的结构特点，讨论了ＡＶ２－ｘＰｘＯ７型（Ａ＝Ｚｒ或Ｈｆ；ｘ＝０．１～１．２）及其部分取代的Ａ＾４＋１－ｙＢ＾４＋ｙＶ２－ｘＰｘＯ７型（Ｂ＝Ｔｉ，Ｃｅ，Ｔｈ，Ｕ，Ｍｏ，Ｐｔ，Ｐｂ，Ｓｎ，Ｇｅ或Ｓｉ；ｙ＝０．１～０．４）和Ａ＾４＋１－ｙＣ＾１＋ｙＤ＾３＋ｙＶ２－ｘＰｘＯ７型（Ｃ为碱金属元素，Ｄ为稀土金属元素）材料的负热膨胀性能。     

镧掺杂对CdO－SnO_2系物相及性能的影响

在ＣｄＯ－ＳｎＯ＿２体系中加入Ｌａ￣（３＋）可以提高学钛铁矿型β－ＣｄＳｎＯ＿３的热稳定性。通过对掺镧材料的物相及微结构的研究、认为Ｌａ￣（３＋）部分固溶到β－ＣｄＳｎＯ＿３品格中是提高其稳定性的主要原因。并可控制掺镧方式及热处理温度来合成不同相组成的气敏材料，改善ＣｄＯ－ＳｎＯ＿２系的气敏性能。     

Fatigue of engineering structures under combined nonproportional loads: An overview

Nonproportionality in fatigue is a matter of loading sequences acting on structures. In such loading cases, a life assessment‐based search of the initiation site is required. This means that for a variety of potential sites, their stress‐strain sequences must be determined and the corresponding fatigue lives have to be calculated. For the determination of local stress‐strain sequences, a superposition of the action of loads at all times for all potential sites must be performed. The superposition has not only to be performed at a particular time of a load reversal but also for a sufficiently large number of intermediate points in time. For the assessment of crack initiation under local nonproportional stress‐strain sequences, a multiaxial fatigue damage hypothesis must be specified. Due to the superiority with respect to accuracy, critical plane approaches are the favourite ones when dealing with nonproportional fatigue of ductile metals. For describing fatigue crack growth, the time sequences for the stress intensity factors corresponding to the 3 opening modes must be obtained by superposition. A mixed‐mode hypothesis must be applied to predict both the direction and the increment of crack growth at each crack front point. A first prediction trial should be based on an appropriate extension of the maximum tangential stress hypothesis. An application of a variant of the maximum shear stress hypothesis might be an amendment. Especially in the case of crack turning, the consideration of crack face contact is mandatory.     

Use of a load non-proportionality measure in fatigue under out-of-phase combined bending and torsion

A load non‐proportionality measure has been developed for use with an existing critical plane fatigue criterion for the case of fatigue under out‐of‐phase bending and torsion. Use of this measure shows improved agreement with test data in the literature for this loading condition.     

Fatigue of vulcanized natural rubber under proportional and non‐proportional loading

Two natural rubber (NR) compounds of hardness shore A 60 and 70 with 10 different biaxial displacement/twist paths were investigated using an axisymmetric cylindrical hollow dumbbell specimen. The effects of the proportional and non‐proportional loading modes on the fatigue life are discussed. In total, 52 fatigue test results are reported with fatigue life results of 3,918 to 488,000 cycles. The effect of the channel phase on the fatigue life is discussed.     

Damage behaviour of laminated composites during fatigue loading

This study deals with the modelling of damage evolution in the carbon/epoxy laminated composites under static and fatigue loading. A cumulative damage model is developed on the basis of damage evolution due to static and fatigue during cyclic loading. A continuum damage mechanics (CDM)‐based damage model coupling with the micromechanics has been utilized to predict the fatigue behaviour of laminate composites. A multicriterion approach has been introduced to predict the damage behaviour in the longitudinal, transverse, and shear direction at the ply scale. Extensive experimental results on T300/EPL1012 carbon/epoxy laminates are prepared to characterize under static and fatigue loading and to evaluate the proposed model in different conditions. The obtained results show that at the beginning of the cyclic loading, the damage grows suddenly and increases until final failure, which justifies the proposed method is able to predict the evolution of the damage due to static and fatigue loading separately during cyclic loading. The obtained results show that considering damage due to static loading leads to more accurate results, particularly in low‐cycle fatigue.     

Effects of non-proportional loading paths on the orientation of fatigue crack path

Fatigue crack path prediction and crack arrest are very important for structural safety. In real engineering structures, there are many factors influencing the fatigue crack paths, such as the material type (microstructure), structural geometry and loading path, etc. In this paper, both experimental and numerical methods are applied to study the effects of loading path on crack orientations. Experiments were conducted on a biaxial testing machine, using specimens made of two steels: 42CrMo4 and CK45 (equivalent to AISI 1045), with six different biaxial loading paths. Fractographical analyses of the plane of the stage I crack propagation were carried out and the crack orientations were measured using optical microscopy. The multiaxial fatigue models, such as the critical plane models and also the energy‐based critical plane models, were applied for predicting the orientation of the critical plane. Comparisons of the predicted orientation of the damage plane with the experimental observations show that the shear‐based multiaxial fatigue models provide good predictions for stage I crack growth for the ductile materials studied in this paper.     

The influence of constant axial compression pre-stress on the fatigue failure of torsion loaded tube springs

This paper reports the results of a series of biaxial static compression and torsion experiments performed to evaluate the effects of static compression stress on the fatigue life those smooth tubes made of high strength spring steel. Compression pre-stress was introduced by a solid steel bar inserted into a hollow spring and loaded with a screw-joint. The experimentally obtained results show a significant extension of fatigue strain life as a result of combining axial compression loading with torsion. Cracking behavior was observed and it was noted that compression pre-stresses contribute to retardation of the fatigue crack initiation process and, consequently, contribute to the extension of fatigue life. The fatigue shear crack initiated in a transverse direction. This crack continues to propagate in the same direction until it starts to propagate as a macro-crack on the maximum shear plane.     

A computerized procedure for long-life fatigue assessment under complex multiaxial loading

A computerized procedure is presented and evaluated for application examples of long-life fatigue analyses of metallic materials under complex multiaxial loading. The method is based on the stress invariants and uses the minimum circumscribed ellipse approach for evaluating the effective shear stress amplitude under complex multiaxial loading. The applicability of the procedure for handling non-proportional loading is examined through typical examples such as combined normal/shear stresses and combined bi-axial normal stresses with complex stress time histories. The effects of phase shift angles, frequency ratios and waveforms on fatigue endurance were re-analysed and compared with available experimental results from the literature. The comparison shows that the presented procedure based on stress invariants is a potential conservative engineering approach, very suitable for fast fatigue evaluation in the integrated computer aided fatigue design.     

Validating generality of recently developed critical plane model for fatigue life assessments using multiaxial test database on seventeen different materials

The present studies are aimed at validation of a newly developed critical plane model with respect to large variety of engineering materials used for different applications. This newly developed model has been recently reported by present authors. To strengthen general applicability of this model, multiaxial test database consisting of a wide variety of multiaxial loading paths have been considered. The strain paths include pure axial, pure torsion, in‐phase axial‐torsion, out‐of‐phase axial‐torsion with phase shift angles varying from 30° to 180° having sine/trapezoidal/triangular strain waveforms, with/without mean axial/shear strains and asynchronous axial‐torsion strain paths of different frequency ratios etc. The materials covered in present study are mainly categorized as ferrous and nonferrous alloys. In ferrous alloy category, material grades from plain carbon steel (mild steel, 16MnR, SA333 Gr. 6, E235 and E355), low‐alloy steel (1Cr‐Mo‐V and S460 N) and austenitic stainless steel (SS304, SS316L and SS347) have been considered. In nonferrous alloy category, aluminium alloys (2024T3‐Al, 7075T651‐Al, and PA38‐T6‐Al), titanium (pure titanium and TC4 alloy), cobalt base super‐alloy (Haynes 188), and nickel alloy (Inconel‐718) have been considered. The predicted and test fatigue lives are found in good agreement for all these materials and complex multiaxial loading paths.     

Fatigue of alumina under contact loading

Bars cyclically loaded by opposite concentrated forces via rollers are appropriate test specimens for the determination of fatigue under contact loading. As practical applications of the proposed test, the contact strengths and numbers of cycles to failure under contact loading were determined for three Al₂O₃. In additional tests the residual strength after a pre-loading under contact loading conditions was determined in four-point bending tests.     

Cumulative fatigue damage dynamic interference statistical model

After studying in depth the statistical characteristics of cumulative fatigue damage D(t) and its critical value D_c, a new dynamic interference statistical model for fatigue reliability analysis is presented in this paper. Because the non-linearity of fatigue damage accumulation has been taken into account, this model is able to predict the fatigue reliability for random spectrum loading. To verify the predicted results, two fatigue experiments were conducted in which the numbers of specimens were more than 100, using fighter spectrum loading (FALSTAFF spectrum) and constant-amplitude loading respectively. It is shown that the new model is reliable, practicable and better than existing models.