某型发动机二级导向器叶片变形和裂纹分析

对一种发动机导向器叶片的变形、裂纹及其断口进行金相和电镜分析。结果表明，发动机温度场不均匀，出现局部高温、致使导向器叶片产生过烧，造成变形和裂纹。     

叶片裂纹声音检测技术研究及应用

提出了对称补偿降噪以及利用希尔伯特变换方法进行降噪和特征信号提取,将噪声信号按对称条件分解,然后利用对称点的信号统计特性相同的特点进行补偿降噪,从而提高了信噪比和系统实时响应能力,克服了监测的非即时性和气流噪声非零均值分布及波动信号对信号提取的干扰。     

涡轮导向器排气面积检测技术研究

本文介绍了几种涡轮导向器排气面积检测方法,针对同一导向器采用不同检测方法检测,对检测结果进行对比,并对检测结果的不确定度进行分析。     

某型航空发动机篦齿盘裂纹的原位涡流检测

针对某型航空发动机篦齿盘上产生的裂纹缺陷,在不拆分发动机的前提下,提出采用涡流检测的方法对篦齿盘进行原位无损检测．设计完成了一套可用于篦齿盘裂纹原位检测的涡流无损检测系统．采用正交型锁相放大器对涡流检测信号进行处理,提高了信号检测精度同时达到了抑制干扰的作用．在标准检测试件和模拟试件上分别进行了试验,试验结果表明,该涡流检测系统可以实现航空发动机篦齿盘裂纹缺陷的原位检测,并且可以定性判断裂纹的深度．     

钢坯表面裂纹的检测技术

表面裂纹的检测是生产高质量钢材的重要保证。目前,冶金企业已经开始应用一些检测技术对钢坯表面裂纹进行在线检测或离线检测。介绍了目前常用的几种钢坯表面裂纹检测技术的原理、特点、应用实例及其检测效果,这些技术包括涡流检测法、漏磁检测法、红外检测法和机器视觉检测法。在此基础上,总结了钢坯表面裂纹缺陷检测技术的发展方向。     

转轮叶片裂纹分析,检测及处理

转轮是水轮机核心部件,转轮的叶片出现裂纹会严重威胁水电厂的安全运行。通过对水轮机转轮叶片进行有限元计算分析,得出应力过于集中通常是叶片裂纹产生的主要原因,此外,叶片也存在设计、制造、运行方面的问题,为此,介绍了水轮机转轮叶片裂纹无损检测的常用方法和一般工艺。     

高炉煤气透平动叶片裂纹分析

在对高炉煤气余压透平发电机转子动叶片进行表面渗透探伤时,发现Ⅰ级动叶片组中有6片叶片的叶榫部有裂纹.为探明裂纹的形成原因,对叶榫裂纹进行了化学成分、高、低倍组织及断口的宏、微观分析.分析结果表明,叶榫第一齿根裂纹属于疲劳裂纹.疲劳裂纹形成的原因主要与齿根底部过渡圆弧类似于直角、圆弧底部的加工条痕比较粗糙、显微组织粗大不均匀、铁素体条带分布不合理以及楔块装配面接触不良等因素有关.     

清洗时间对钛合金铸件荧光渗透检测的影响

在钛合金铸件荧光渗透检测以浸涂方式施加渗透液时,渗透剂去除时的清洗时间对荧光渗透检测结果有重要影响。以不同清洗时间条件下的PSM-5标准试块渗透检测结果为依据,结合不同清洗时间下钛合金铸板的荧光渗透检测实验结果,研究确定了钛合金铸件荧光渗透检测允许最长清洗时间和单次渗透检测最大检测铸件数量。结果表明,为得到可靠的荧光渗透检测结果,在荧光渗透检测系统各参数满足标准要求的前提下,最长清洗时间不宜超过15 min。结合最长清洗时间,确定某铸件进行荧光渗透检测时的单次最大检测数量为20件。对大型复杂结构铸件进行荧光渗透检测时,可通过增加清洗人员数量的方法控制清洗时间,确保荧光渗透检测结果的可靠性。     

转子裂纹检测与寿命预测技术研究

现代的抗疲劳设计法——损伤容限设计使零件在出现疲劳裂纹后通过严格的检修、剩余寿命计算和断裂控制仍能安全使用 ,使充分利用零件的剩余强度成为可能。对损伤容限设计的关键技术——初始缺陷或服役中出现的疲劳裂纹检测和疲劳剩余寿命预测技术进行了研究。成功地研制了一套性能优良的交流电位表面裂纹监测系统 ,分辨率为 0 .1 mm,测量精度达到± 2 % ,测量范围为 0～ 1 0 0 mm;开发出一套微机平台上的基于断裂力学的 (含表面裂纹 )转子剩余寿命计算程序 ,为分析裂纹扩展形态和概率断裂力学方法估算剩余寿命提供了快速计算途径。有较强的工程实用性和良好的市场开发前景。     

裂纹检测中的相位信息研究

裂纹涡流无损检测时,可以通过测量检测信号与激励信号的相位差来进行判断是否有裂纹.为实现牵引电机主极裂纹检测,对黄铜材料制成的牵引电机主极,在检测信号频率的变化、提离、边缘以及正常和裂纹等情况下,进行检测信号与激励信号的相位差变化测试实验、分析,得出了上述情况下的相位差变化范围,为牵引电机主极裂纹的动态检测提供了依据.     

Stress intensity factors for a wide range of long-deep semi-elliptical surface cracks, partly through-wall cracks and fully through-wall cracks in tubular members

To calculate the rate of fatigue crack growth in tubular members, one approach is to make use of the fracture mechanics based Paris law. Stress intensity factors (SIF) of the cracked tubular members are prerequisite for such calculations. In this paper, stress intensity factors for circumferential deep semi-elliptical surface crack (a/t > 0.8), semi-elliptical partly through-wall crack and fully through-wall crack cracks in tubular members subjected to axial tension are presented. The work has produced a comprehensive set of equations for stress intensity factors as a function of a/T, c/πR and R/T for deep surface cracks. For the partly through-wall cracks and fully through-wall cracks, two sets of bounding stress intensity factor equations were produced based on which all stress intensity factors within the range of parameters can be obtained by interpolation.     

Stress intensity factors for slanted through-wall cracks based on elastic finite element analyses

Based on detailed 3‐dimensional (3‐D) elastic finite element (FE) analyses, the present paper provides stress intensity factors (SIFs) for plates with slanted through‐wall crack (TWC) and cylinders with slanted circumferential TWC. Regarding loading conditions, axial tension was considered for the plates, whereas axial tension, global bending and internal pressure were considered for the cylinders. To cover a practical range, the geometric variables affecting the SIF were systematically varied. Based on FE results, SIFs along the crack front, including the inner and outer surface points, were provided. The present results can be used to evaluate the fatigue crack growth or stress corrosion cracking behaviour of a slanted TWC and furthermore to perform detailed Leak‐Before‐Break analysis considering a more realistic crack shape.     

Elastic-plastic fracture mechanics assessment for steam generator tubes with through-wall cracks

The present work provides an elastic‐plastic fracture mechanics (EPFM) assessment scheme for a steam generator tube with a through‐wall crack under internal pressure. Noting that the geometry and material are rather uniform for steam generator tubes, and furthermore the only loading to be considered is internal pressure, an engineering EPFM analysis method is proposed to assess through‐wall cracks in steam generator tubes. Important outcomes of the present work are closed‐form approximations for J and crack opening displacement (COD). Sufficient confidence in the proposed J and COD estimates is gained from good agreements with the finite element results over a wide range of the crack length and pressure magnitude. Another important element of the EPFM assessment is to determine relevant J‐resistance curve for steam generator tubes. To improve the accuracy of predicting tube failure, the present paper also proposes a new method to determine fracture toughness using an actual tubular specimen instead of using a standard specimen, from which J‐resistance curves of steam generator tubes are obtained. Using the proposed J and toughness estimates, maximum pressures of steam generator tubes with through‐wall crack are estimated based on EPFM analysis, which is compared with experimental results and predicted ones based on limit load approach.     

Determination of failure pressure for tubes with two non-aligned axial through-wall cracks

The 40% of wall thickness criterion which has been used as a plugging rule is applicable only to a single cracked steam generator tubes. In the previous studies performed by authors, several failure prediction models were introduced to estimate the plastic collapse pressures of steam generator tubes containing two adjacent collinear or parallel axial through-wall cracks. The objective of this study is to examine the failure prediction models and propose optimum ones for two non-aligned axial through-wall cracks in steam generator tubes. In order to determine the optimum ones, a series of plastic collapse tests and finite element analyses were carried out for steam generator tubes with two machined non-aligned axial through-wall cracks. Thereby, either the plastic zone contact model or COD based model was selected as the optimum one according to axial distance between two cracks. Finally, the optimum failure prediction model was used to demonstrate the conservatism of flaw characterization rules for multiple cracks having equal lengths according to ASME code.     

新型圆周摩擦活动导叶保护装置的研究

介绍了一种新型圆周摩擦保护装置,应用于水轮机导水机构中,对活动导叶起过载保护作用。该装置采用一种新型预紧结构（FROMO®预紧螺母）,通过与剪断销保护装置、端面摩擦保护装置的结构比较及试验数据的分析,表明其摩擦力矩的设定简单而且方便,一致性高,准确性好,并使机构具有良好的重复使用性能。     

Strength of guide vane components of gas turbines

The article presents an analysis of the main kinds of damage to elements of guide vanes of gas turbine engines: cracking, irreversible deformations, bending of the vane edges. Methods are described for calculating the safety factor of guide vane components under conditions of loading by heat cycling on the basis of the theory of adaptability.Leningrad. Translated from Problemy Prochnosti, No. 11, pp. 119–124, November, 1989.     

Elastic-plastic fracture mechanics analyses of circumferential through-wall cracks between elbows and pipes

The present work proposes a method for elastic-plastic fracture mechanics analysis of the circumferential through-wall crack in weldment joining elbows and attached straight pipes, subject to in-plane bending. Heterogeneous nature of weldment is not explicitly considered and thus, the proposed method assumes cracks in homogeneous materials. Based on small strain finite element limit analyses using elastic-perfectly plastic materials, closed-form limit loads for circumferential through-wall cracks between elbows and straight pipes under bending are given. Then applicability of the reference stress-based method to approximately estimate J and crack opening displacement (COD) is evaluated. It was found that the limit moments for circumferential cracks between elbows and attached straight pipes can be much lower than those for cracks in straight pipes, particularly for a crack length of less than 30% of the circumference; this result is of great interest in practical cases. This result implies that, if one assumes that the crack locates in the straight pipe, limit moments could be overestimated significantly, and accordingly, reference stress-based J and COD could be significantly overestimated. For the leak-before-break analysis, accurate J and COD estimation equations based on the reference stress approach are proposed.     

Design of the new guide vane for the turbo air classifier

The guide vane is a common guide part in a turbo air classifier. However, there is a lack of a theoretical design basis and an analogy method is often used to design the guide vanes. The guide vanes’ effects of improving the flow field distribution are obtained by means of comparison of the flow field of the classifiers with and without guide vanes. However, the guide vane of a 15° setting angle should be optimized due to the non-uniform airflow circumferential distribution in the annular region. To obtain a well-distributed flow field of a turbo air classifier, a design method for the guide vane is provided based on the airflow trajectory in the volute and a new guide vane of a 10° setting angle is designed under the operating condition of 12–1200. The numerical simulation results show that the standard deviation of circumferential radial and tangential velocity is decreased. Besides, the trajectories of the particles with the same size in different circumferential positions show their classification results are consistent. This guide vane design method is feasible and provides the design references for the turbo air classifiers.     

Stress intensity factors and crack opening displacements for slanted axial through-wall cracks in pressurized pipes

This paper proposes elastic stress intensity factors and crack opening displacements (CODs) for a slanted axial through-wall cracked cylinder under an internal pressure based on detailed three-dimensional (3D) elastic finite element (FE) analyses. The FE model and analysis procedure were validated against existing solutions for both elastic stress intensity factor and COD of an idealized axial through-wall cracked cylinder. To cover a practical range, four different values of the ratio of the mean radius of cylinder to the thickness ( R _m/ t ) were selected. Furthermore, four different values of the normalized crack length and five different values of the ratio of the crack length at the inner surface to the crack length at the outer surface representing the slant angle were selected. Based on the elastic FE results, the stress intensity factors along the crack front and CODs through the thickness at the centre of the crack were provided. These values were also tabulated for three selected points, that is, the inner and outer surfaces and at the mid-thickness. The present results can be used to evaluate the crack growth rate and leak rate of a slanted axial through-wall crack due to stress corrosion cracking and fatigue. Moreover, the present results can be used to perform a detailed leak-before-break analysis considering more realistic crack shape development.     

The T-stress solutions for through-wall circumferential cracks in cylinders subjected to general loading conditions

The elastic T-stress is a parameter used to define the level of constraint at a crack tip. It is important to provide T-stress solutions for practical geometries to apply the constraint-based fracture mechanics methodology. In the present work, T-stress solutions are provided for circumferential through-wall cracks in thin-walled cylinders. First, cylinders with a circumferential through-wall crack were analyzed using the finite element method. Three cylinder geometries were considered; defined by the mean radius of the cylinder (R) to wall thickness (t) ratios: R/t = 5, 10, and 20. The T-stress was obtained at eight crack lengths (θ/π = 0.0625, 0.1250, 0.1875, 0.2500, 0.3125, 0.3750, 0.4375, and 0.5000, θ is the crack half angle). Both crack face loading and remote loading conditions were considered including constant, linear, parabolic and cubic crack face pressures and remote tension and bending. The results for constant and linear crack face pressure were used to derive weight functions for T-stress for the corresponding cracked geometries. The weight functions were validated against several linear and non-linear stress distributions. The derived weight functions are suitable for T-stress calculations for circumferential cracks in cylinders under complex stress fields.