BM50型风扫磨机主齿轮失效分析

BM50型大力神风扫磨机在正常操作务件下主齿轮(材质为4340钢)出现早期失效，一齿断裂脱落，另有17齿开裂。采用化学成分分析、金相检验、扫描电镜观察以覆硬度测试方法，对断裂齿轮进行了失效分析，结果表明，失效齿轮属于疲劳断裂；引起断裂的直接原因是位于齿轮啮合面硬化层底部的堆积夹杂物，所用材料存在严重的冶金质量缺陷。     

翅片管路焊接接头断裂原因分析

通过KYKY2800扫描电镜等技术手段对翅片管路焊接接头进行失效分析。分析表明,焊缝与2#环管的焊趾处存在有不连续的咬边,造成应力集中;在交变应力的作用下于咬边处产生微裂纹,并沿一定方向扩展（同时材料的不均匀性也为裂纹的扩展提供了有利条件）,直至最后疲劳断裂,造成失效。最后提出了预防措施。     

The Distribution of the Maximum Sum of Rank

In this paper a c-sample slippage analogue of the Wilcoxon [11] test is considered. Given a sample of size n for each of c populations, the test rejects the hypothesis that the c populations are identical when max_1≤i≤c σ _k r _ik > λ, where r _i1, …, r _in are the ranks of the observations from the i-th population in the combined sample of size cn. The small and large sample distributions of the test statistic are derived. Tables of the exact distribution are given for c = 2(1)5, n = 2(1)5. Tables of critical values are given for c = 2(1)6, n = 2(1)8 for values of α = 0.001, 0.005, 0.01, 0.025, 0.05, 0.10, and 0.20.     

自蒸发器材质检验及裂纹成因分析

采用化学成分分析、力学性能试验、宏微观检验等方法对自蒸发器材质和裂纹成因进行了分析。结果表明,碱脆是导致自蒸发器产生裂纹的主要原因。     

Experimental study on the deformation and failure mechanism of overburden rock during coal mining using a comprehensive intelligent sensing method

Understanding the spatiotemporal evolution of overburden deformation during coal mining is still a challenge in engineering practice due to the limitation of monitoring techniques. Taking the Yangliu Coal Mine as an example, a similarity model test was designed and conducted to investigate the deformation and failure mechanism of overlying rocks in this study. Distributed fiber optic sensing(DFOS), highdensity electrical resistivity tomography(HD-ERT) and close-range photogrammetry(CRP) technolo...     

油气分离器失效分析

通过对油气分离器失效部位进行宏观检查、化学成分分析、金相分析、力学性能测试、断口形貌观察及能谱分析,认为工艺介质中硫化氢浓度的上升和材料纯净度不高是导致设备失效的根本原因,并提出了相应的建议。     

Reliability analysis and micromechanics: A coupled approach for composite failure prediction

This work aims at associating two classical approaches for the design of composite materials: first, reliability methods that allow to account for the various uncertainties involved in the composite materials behaviour and lead to a rational estimation of their reliability level; on the other hand, micromechanics that derive macroscopic constitutive laws from micromechanical features. Such approach relies on the introduction of variabilities defined at the microscale and on the investigation of their consequences on the material macroscopic response through an homogenization scheme. Precisely, we propose here a systematic treatment of variability which involves a strong link between micro- and macroscales and provides a more exhaustive analysis of the influence of uncertainties. The paper intends to explain the main steps of such coupling and demonstrate its interests for material engineering, especially for constitutive modelling and composite materials optimization. An application case is developed throughout on the failure of unidirectional carbon fibre-reinforced composites with a comparative analysis between experimental data and simulation results.     

Consequence-based structural design approach for black swan events

The metaphor of black swan refers to unpredictable events like 9/11, the Indian Ocean tsunami, or the Oklahoma City Federal Building bombing, that cause catastrophic consequences for structural system safety. The likelihood of occurrence for such unforeseen events cannot be estimated from the observed data or prognosticated by experts. The absence of event and likelihood information renders futile the application of usual risk-based methods for design. Therefore, a shift from the probabilistic approach to consequence-based structural design is necessary for coping with the unexpected demands. This is accomplished through the conceptual development of a system capacity oriented design approach, where structural members are designed for variable reliabilities based upon their contribution to causing adverse system consequences. Information about general structural integrity encoded in the stiffness matrix is applied, using member consequence factors ranging from 0 to 1, for determining a member’s contribution towards system response. The structural system is designed using member consequence factors as additional partial factors on the resistance side of the design equations. The consequence-based scheme does not need a triggering hazard event (or its likelihood) and is an apt structural design approach for black swan events.     

Comparison of different failure criteria for fiber-reinforced plastics in terms of fracture curves for arbitrary stress combinations

For fiber-reinforced plastics exists a big number of different criteria for the failure prediction. The intention of this paper is to compare the TSAI-HIL-, the LaRC04- and PUCK’s criterion in terms of their fracture curves for a unidirectional glass-fiber reinforced composite layer. Therefore after the implementation of these three criteria, the two-dimensional fracture curves for all possible stress combinations, which can be derived from a general spatial stress tensor, are computed. In this way, the characteristics of the criteria, similarities and differences and possible weak points become obvious.     

VRLA蓄电池的可靠性和主动维护

VRLA铅酸蓄电池是当前通信电源系统中采用的主要的储能装置。与传统的VLA蓄电池相比,VRLA铅酸蓄电池的主要优点是维护工作量较小,主要缺点是寿命短。而且,其实际的寿命比设计寿命低得多。因此,VRLA蓄电池的可靠性在一定程度上受到限制。为了确保VRLA蓄电池系统的安全可靠,必须积极主动地进行维护工作。本文分析VRLA蓄电池早期故障的原因,讨论延长VRLA蓄电池寿命,提高VRLA蓄电池供电系统的可靠性的途径,提出VRLA蓄电池主动维护和运行数据分析方法。