混凝土工程外观缺陷处理方法

对于混凝土工程,不仅要关注混凝土强度,而且还要求其外观质量。本文从实践操作经验出发,就如何保证混凝土质量问题提出了自己的看法。     

A multiscale flaw detection algorithm based on XFEM

We present a novel multiscale algorithm for nondestructive detection of multiple flaws in structures, within an inverse problem type setting. The key idea is to apply a two‐step optimization scheme, where first rough flaw locations are quickly determined, and then, fine tuning is applied in these localized subdomains to obtain global convergence to the true flaws. The two‐step framework combines the strengths of heuristic and gradient‐based optimization methods. The first phase employs a discrete‐type optimization in which the optimizer is limited to specific flaw locations and shapes, thus converting a continuous optimization problem in the entire domain into a coarse discrete optimization problem with limited number of choices. To this end, we develop a special algorithm called discrete artificial bee colony. The second phase employs a gradient‐based optimization of the Broyden–Fletcher–Goldfarb–Shanno type on local well‐defined and bounded subdomains determined in the previous phase. A semi‐analytical approach is developed to compute the stiffness derivative associated with the evaluation of objective function gradients. The eXtended FEM (XFEM), with both circular and elliptical void enrichment functions, is used to solve the forward problem and alleviate the costly remeshing of every candidate flaw, in both optimization steps. The multiscale algorithm is tested on several benchmark examples to identify various numbers and types of flaws with arbitrary shapes and sizes (e.g., cracks, voids, and their combination), without knowing the number of flaws beforehand. We study the size effect of the pseudo grids in the first optimization step and consider the effect of modeling error and measurement noise. The results are compared with the previous work that employed a single continuous optimization scheme (XFEM–genetic algorithm and XFEM–artificial bee colony methods). We illustrate that the proposed methodology is robust, yields accurate flaw detection results, and in particular leads to significant improvements in convergence rates compared with the previous work. Copyright © 2014 John Wiley & Sons, Ltd.     

重轨钢连铸工艺优化

针对重轨钢铸坯的角部缺陷、探伤不合、中心疏松和偏析问题,分析出其影响原因并采取了以下措施:改变保护渣的成分和性能,使用四孔浸入式水口,将典型拉速下的二冷比水量由大于0.3L/kg降至0.2L/kg左右,同时延长了轻压下位置。最终使得铸坯质量大幅提升,中心疏松I级合格率达99.5%,探伤合格率稳定在99.5%以上,角部缺陷消除。     

内压对射孔套管强度影响的有限元分析

射孔对套管抗挤强度的影响程度取决于多种因素.主要研究内压对射孔套管强度的影响.建立未射孔套管、不带水泥环射孔套管、外裹水泥环射孔套管有限元模型,并应用ANSYS有限元软件分析计算了未射孔、射孔及孔边开裂三种情况下套管的最大应力,同时研究了水泥环对射孔套管强度的影响.结果表明:射孔套管最大应力比未射孔套管增大了64%,孔...     

产品瑕疵担保责任与产品责任的区别

产品质量是关系国计民生的大事,而对产品质量出现问题所应承担的责任,在《产品质量法》中有明确规定。但多数人对产品瑕疵担保责任与产品责任了解的不多,常把二者混同起来,本文针对两点的区别,进行了阐述,并对产品瑕疵担保责任进行了详细的说明。     

硬填料密封泄漏分析

对硬填料泄漏进行了分析，并提出防止泄漏的有效方法。     

300MW核电汽轮机低压转子循环寿命的估算

本文介绍了缺陷转子锻件循环寿命的估算方法。按照冷态启动状态估算了临界缺陷尺寸,研究了循环寿命与缺陷形状的关系。结果表明,该转子的寿命不少于8815次循环。     

Flaw detection in metals by the ACPD technique: Theory and experiments

The Alternating Crack Potential Drop (ACPD) technique is mainly used to characterize surface cracks in metals. To-date, this technique has the following two limitations: it is limited to the so-called thin skin assumptions, and is applicable to open (visible) flaws. Saguy and Rittel recently proposed a methodology based on numerical simulations to overcome these limitations [Saguy H, Rittel D. Bridiging thin and thick skin solutions for alternating currents in crack conductors. Appl Phys Lett J 2005; 87: 84103–84103/3; Saguy H, Rittel D. Alternating current flow in internally flawed conductors: a tomographic analysis. Appl Phys Lett J 2006; 89: 94102–94102/3]. This paper presents experimental results, which support the proposed solutions and methodology to expand the universality of the ACPD technique as a key NDT tool.     

Metrological Provision of Ultrasonic Defectoscopes for General Purposes under Production and Operating Conditions

Objective data for determining defect parameters with the aim of optimizing monitored characteristics during operation of general purpose modern ultrasonic defect detectors in-situ are systematized. The redundancy of periodic verification by the Russian State Standards Organization of ultrasonic defect detector and piezoelectric transducer parameters is demonstrated. Recommendations are given for improving standard documents.     

对DF4、8型机车车轴不良状态的研究

对DF4、8型机车轮对大修中车轴的各种不良状态进行了统计,分析了各种不良状态产生的原因,并指出了轮对检修工作中应注意的问题。