Fatigue crack propagaion under mixed mode loading

Mixed model fatigue crack propagation is analyzed in this paper, using a centre cracked plate geometry, loaded under un-iaxial cyclic tension. Based on maximum principal stress criterion, a modified Paris expression of fatigue crack growth rate is derived in terms of ΔK and crack angle β_α for an inclined crack. It is also shown that it is more convenient to express the Paris equation by means of crack length projected on the x -axis, α_x rather than the actual length, α itself. The crack trajectory due to cyclic loading is predicted, β is varied from 29° to 90°. Experimental data on Type L3 aluminium agree fairly well with predicted values when β_α exceeds 30°.     

开设实验结构力学课程的设想

首先指出了目前结构力学教学的现状与不足,接着论述了目前教学、设计和科研中存在的两个问题. 为弥补其不足并提升结构力学的教学质量,提出了开设实验结构力学课程的设想,说明了开设此课程的已有条件、实验内容和预期达到的目的.     

船用制动器摩擦片的寿命用可靠性分析

对某船用２ＺＦ－１２０Ｂ齿轮箱制动器摩擦片磨损数据进行回归分析，并讨论可靠度及耐磨寿命预测推算的原理和方法。该方法可推广应用于其他磨损件。     

15～600 keV脉冲硬X射线能谱测量

介绍了基于吸收法的脉冲硬X射线能谱测量的基本原理及设计思路,完成了探测器及吸收片的选型,设计了射线准直系统,研究了散射对测量的影响,以12路PIN探测器阵列及铜、铝吸收片为测量核心部件研制了脉冲硬X射线能谱测量系统。实验测量了真空环境下“闪光二号”加速器串级二极管产生的脉冲硬X射线强度,获得了不同衰减程度的实验波形,通过解谱获得了脉冲硬X射线的能谱,光子最高能量约600 keV,平均能量约89.1 keV,与理论计算的结果比较符合。     

Enhanced absorption properties of ordered mesoporous carbon/Co-doped ordered mesoporous carbon double-layer absorbers

Ordered mesoporous carbon (OMC) and metal-doped (M-doped) OMC composites are prepared, and their electromagnetic (EM) parameters are measured. Using the measured EM parameters we calculate the EM wave absorption properties of a double-layer absorber, which is composed of OMC as an absorbing layer and M-doped OMC as the matching layer. The calculated results show that the EM wave absorption performance of OMC/OMC-Co (2.2mm/2.1mm) is improved remarkably. The obtained effective absorption bandwidth is up to 10.3 GHz and the minimum reflection loss reaches 47.6 dB at 14.3 GHz. The enhanced absorption property of OMC/OMC-Co can be attributed to the impedance match between the air and the absorber. Moreover, it can be found that for the absorber with a given matching layer, a larger value of -tanδε (= tan δε absorbing tan δε matching ) can induce better absorption performance, indicating that the difference in impedance between the absorbing layer and the matching layer plays an important role in improving the absorption property of double-layer absorbers.     

变系数两点边值问题的有限元强校正格式

该文利用投影型插值,对于变系数两点边值问题,获得了一个高精度的有限元强校正格式,数值实验更验证了这一结果．     

THE ANALYSIS OF THE TRANSLATION-TORSION COUPLING EARTHQUAKE RESPONSES OF SINGLE-STORY ECCENTRIC FACTORY BUILDINGS WITH CONSIDERATION OF ROOF WHOLE-SPACE-WORK

In this paper, the translation-torsion coupling earthquake responses, of single-story ecoentric factory buildings with consideration of whole-space-work of the roof in 3-dimension non-inertia system are analysed and studied, and its calculation model has been established. And what is more, corresponding motion equations of earthquake responses have been derived, analysed and discussed. And it points out that under the action of the earthquake including rotational component, the principle of superposition of independent action for each earthquake component and mode-superposition method of dynamic responses analysis are already not applicable. In this paper, the translation-torsion coupling earthquake responses of sorne singlestory eccentric factory building are calculated and analysed by comparison methods without consideration of the earthquake torsional component. The conclusion is that when whole-space-work of the roof is considered, the results of calculation are more conformable to the actual earthq     

OSCILLATION CRITERIA OF SOLUTIONS FOR A CLASS OF DELAY DIFFERENTIAL EQUATIONS WITH POSITIVE AND NEGATIVECOE FFICIENTS

Some sufficient conditions for the oscillation of all solutions of the delay differential equations with positive and negative coefficientsare obtained, where 0 < αi, βi <1,pi> 0, qi > 0, are constants, t = 1,2, …, n.     

窄点设计法在功、热联合系统中的应用

余热利用是节能的重要途径。化工、炼油和冶金等企业中通常有若干股余热流拥有大量余热,一部分可在工艺过程中加以利用,另一部分可作为动力回收的热源。许多设计方法把热利用和动力回收两者隔裂开来,首先着眼于热利用,然后再考虑动力回收。这种方法可以对热利用和动力回收系统分别进行优化,但从总体上未必能达到最优目标。八     

全芳族有规交替共聚酯的合成及液晶性

合成了一系列三元和四元全芳族共聚酯，其链结构特征为有规交替地分布着对羟苯甲酰基（HB）单元。结构考察了HB在链中对共聚酯性能的影响，与不含HB的共聚物相比，发现其熔融温度下降，耐热性提高；液晶性不受损害；共聚物熔融时呈Schlieren或thred-like向列型织态结构；径熔融合冷却所得固态聚合物的激光小角光散射图象呈现明暗相同的斑纹。