任意分布参数的涡轮盘裂纹扩展寿命可靠性分析

讨论了某型涡轮盘随机参数服从任意分布时的可靠性问题.在基本随机参数前四阶矩已知的情况下,以Pairs-Erdogan裂纹扩展模型为基础,应用随机摄动理论和Edgeworth 级数技术,采用疲劳寿命模型对某型涡轮盘随机参数服从任意分布时的可靠性进行分析,建立了涡轮盘疲劳寿命可靠性分析模型,并求得了涡轮盘裂纹扩展寿命的可靠度.模型计算结果与Monte-Carlo仿真结果非常接近,文章提出的方法对涡轮盘可靠性设计具有一定的参考价值.     

高压涡轮盘的热弹性应力分析

本文利用大型通用有限元程序ALGOR某型发动机的高压涡轮盘及其榫齿进行了三维热弹性应力分析,对如何处理轮盘和叶片之间的连接进行了研究,并在有限元计算中应用了边界元法,从而得到了盘及榫齿的热弹性应力分布,并已应用于实际的发动机结构设计中。     

涡轮盘风冷过程数值模拟研究

采用商用CFD分析软件Fluent对涡轮盘固溶处理后的风冷过程进行了数值模拟研究,定量分析了盘件内温度、冷速等参数的分布情况.模拟结果显示,单风扇风冷过程中盘件沿径向和周向的温度分布较三风扇冷却方式均匀.两种形式风冷过程的风场结果表明,单风扇冷却时盘件表面的冷却速度较高.     

涡轮盘篦齿裂纹扩展的有限元数值模拟

为了详细考察篦齿裂纹的扩展规律,对篦齿裂纹从齿尖一直扩展到即将完全穿透篦齿环的过程进行了数值模拟.含篦齿裂纹的涡轮盘有限元模型采用子模型法建立,使用M积分计算裂纹前沿的应力强度因子;在确定篦齿裂纹前沿每一节点处的局部扩展方向及距离后,通过样条曲线拟合出新裂纹前沿,并依靠自适应网格划分实现裂纹区有限元网格的更新.数值模拟结果表明,篦齿根部过渡圆角顶部可以视为裂纹缓慢扩展阶段与快速扩展阶段的分界点,在此之前篦齿裂纹以穿透型裂纹的形态以较低的速度进行扩展,在此之后篦齿裂纹开始向表面裂纹进行转化,并且平均扩展速度大大增加,分界点前的裂纹扩展寿命是之后的数倍.此外,由数值模拟结果还可以发现,增大篦齿根部过渡圆角半径以及减小相邻篦齿的间距,均有助于延缓篦齿裂纹的扩展.     

涡轮盘榫槽综合测具的研究

涡轮盘是发动机重要承力构件,在转速高、温度高的环境下工作,涡轮盘具有较高的抗疲劳、抗高温氧化及抗燃气腐蚀能力。涡轮盘沿圆周均布一般在60-102个榫槽,叶片用枞树形榫头插入盘的枞树形槽内,检测榫槽的尺寸、位置度技术条件要求,保证叶片传递载荷分布均匀,提高发动机的性能稳定性。     

烟气轮机涡轮盘和叶片用WASPALOY合金研究

对烟气轮机涡轮盘和叶片用WASPALOY合金从合金成分特点、相析出规律、冶炼、加工和力学性能等方面进行了综述和讨论，重点介绍了该合金针对烟气轮机使用环境的合金设计特点及析出相特征，为烟气轮机用涡轮盘和叶片材料的发展给出研究方向。     

随机-区间型天线结构有限元及可靠性分析

构建了对随机-区间混合型天线结构的有限元及可靠性分析模型,提出了一种新的处理不确定性因素的结构有限元分析方法,给出了结构保精度和保强度两工况的概率描述。同时考虑了结构的物理参数、几何参数的随机性和作用风载荷的区间性。首先将随机变量固定,利用区间因子法求得结构位移和应力响应的区间范围,然后在区间内任意点处利用随机因子法求结构响应的随机分布范围。构造了天线反射面位移响应和结构单元应力响应不确定变量的数字特征计算公式,进而得到结构各响应量的可靠性指标。对一8m口径天线结构进行了分析,分析结果表明文中所提方法具有合理性和可行性。     

某新机四级涡轮盘变形控制技术研究

某新机是新一代高性能发动机,低压四级涡轮盘是发动机中涡轮转子中的核心转动部件,因受零件结构限制,其加工时易产生变形,零件合格率低。通过优化涡轮盘加工工艺路线、加工余量及切削路径,控制切削参数,提高零件加工质量,提高零件合格率。     

模糊随机桁架结构可靠性指标的灵敏度分析

在结构有限元分析基础之上研究了模糊随机桁架的可靠性指标对设计变量的灵敏度问题.同时考虑结构参数和荷载的模糊随机性,在利用双因子法得出结构模糊随机响应及其模糊数字特征的基础之上,推导了结构的可靠性指标对设计变量的灵敏度.通过算例验证了该方法的可行性,得出了若干有意义的结论.     

Reliability-oriented optimal design of intentional mistuning for a bladed disk with random and interval uncertainties

When interblade coupling is weak, the dynamic response of a bladed disk is very sensitive to the presence of uncertainties. Excessive response variation can be very harmful. Previous studies have indicated that introducing blade-to-blade difference in nominal design, known as intentional mistuning, could reduce the level of response variation. In this research, an efficient computational framework that yields the optimal design of intentional mistuning is developed to maximize the bladed disk reliability. Both the random uncertainty of blades and the interval uncertainty of disk connections are considered. The Metropolis–Hastings algorithm is applied to find the worst case response under interval uncertainty, and Monte Carlo simulation is employed to account for the random mistuning effect. A gradient-based approach is then established to find the minimum design modification needed to achieve a designated reliability level. Case studies are carried out to illustrate the effectiveness of the proposed method.     

Fatigue reliability assessment of turbine discs under multi‐source uncertainties

Hot section components of aircraft engines like high pressure turbine (HPT) discs usually operate under complex loadings coupled with multi‐source uncertainties. The effect of these uncertainties on structural response of HPT discs should be accounted for its fatigue life and reliability assessment. In this study, a probabilistic framework for fatigue reliability analysis is established by incorporating FE simulations with Latin hypercube sampling to quantify the influence of material variability and load variations. Particularly, variability in material response is characterized by combining the Chaboche constitutive model with Fatemi‐Socie criterion. Results from fatigue reliability and sensitivity analysis of a HPT disc indicated that dispersions of basic variables must be taken into account for its fatigue reliability analysis. Moreover, the proposed framework based on the strength‐damage interference provides more reasonably correlations with its field number of flights rather than the load‐life interference one.     

Quench crack behavior of nickel-base disk superalloys

There is a need to increase the temperature capability of superalloy turbine disks to allow higher operating temperatures in advanced aircraft engines. When modifying processing and chemistry of disk alloys to achieve this capability, it is important to preserve the ability to use rapid cooling during supersolvus heat treatments to achieve coarse grain, fineγ′ microstructures. An important step in this effort is an understanding of the key variables controlling the cracking tendencies of nickel-base disk alloys during quenching from supersolvus heat treatments. The objective of this study was to investigate the quench cracking tendencies of several advanced disk superalloys during simulated heat treatments. Miniature disk specimens were rapidly quenched after solution heat treatments. The responses and failure modes were compared and related to the quench cracking tendencies of actual disk forgings. Cracking along grain boundaries was generally observed to be operative. For the alloys examined in this study, the solution temperature, not alloy chemistry, was found to be the primary factor controlling quench cracking. Alloys with high solvus temperatures show greater tendency for quench cracking.     

An efficient hybrid reliability analysis method with random and interval variables

Random and interval variables often coexist. Interval variables make reliability analysis much more computationally intensive. This work develops a new hybrid reliability analysis method so that the probability analysis (PA) loop and interval analysis (IA) loop are decomposed into two separate loops. An efficient PA algorithm is employed, and a new efficient IA method is developed. The new IA method consists of two stages. The first stage is for monotonic limit-state functions. If the limit-state function is not monotonic, the second stage is triggered. In the second stage, the limit-state function is sequentially approximated with a second order form, and the gradient projection method is applied to solve the extreme responses of the limit-state function with respect to the interval variables. The efficiency and accuracy of the proposed method are demonstrated by three examples.     

Structural reliability analysis and uncertainties‐based collaborative design and optimization of turbine blades using surrogate model

In power and energy systems, both the aerodynamic performance and the structure reliability of turbine equipment are affected by utilized blades. In general, the design process of blade is high dimensional and nonlinear. Different coupled disciplines are also involved during this process. Moreover, unavoidable uncertainties are transported and accumulated between these coupled disciplines, which may cause turbine equipment to be unsafe. In this study, a saddlepoint approximation reliability analysis method is introduced and combined with collaborative optimization method to address the above challenge. During the above reliability analysis and design optimization process, surrogate models are utilized to alleviate the computational burden for uncertainties‐based multidisciplinary design and optimization problems. Smooth response surfaces of the performance of turbine blades are constructed instead of expensively time‐consuming simulations. A turbine blade design problem is solved here to validate the effectiveness and show the utilization of the given approach.     

Research on multiple-state industrial robot system with epistemic uncertainty reliability allocation method

Reliability allocation of industrial robot (IR) system is one of the important means to improve its whole life cycle, reduce maintenance cost, and characterize weak subsystems. The IR system is not only very complex but also has strong customization; meanwhile, its sample data are small, resulting in unclear degeneration and failure. Based on the above two epistemic uncertainties, a new methodology called multiple-state IR system reliability allocation method with epistemic uncertainty (MIRS-RAM-EU) is proposed. First, the Dempster-Shafer (D-S) evidence theory is used to quantify the epistemic uncertainty. Then, the Kolmogorov differential equations of MIR's subsystems are calculated. The reliability index of MIRS is allocated based on Birnbaum importance degree theory, and the reliability allocation coefficient of each IR subsystem is clearly expressed by this method. Finally, compared with traditional importance allocation method, the MIRS-RAM-EU is more efficient and accurate. This method is usefully directive for reliability evaluation of IR.     

风力机塔架结构研究概述

塔架作为风力机结构体系的重要组成部分,起到支撑上部结构质量、承受动载荷的作用,保障了风力机的正常运行.对塔架结构研究进行总结概述,能够完善风力机结构设计理论体系.从工程实用角度出发,以风力机塔架结构的刚度、强度、稳定性以及抗疲劳性能为核心,围绕结构选型、静动态特性、屈曲特性及疲劳特性等要点问题进行综述,回顾了各领域不同研究阶段的国内外成果,同时,介绍了新型塔架结构设计、随机荷载动力分析以及非线性屈曲与疲劳特性分析等前沿热点问题的研究进展.总结了上述要点问题的研究现状,详细阐述了相关技术的原理和应用,梳理其发展脉络,并对未来研究趋势进行了展望.内容涵盖了风力机塔架结构的各主要设计指标,能够为风力机塔架设计与分析提供指导.     

一种分段式结构的变桨距垂直轴风力发电机研究

针对国内风电频率不稳定的问题,提出了一种分段式结构的变桨距垂直轴风力发电机方案.简要介绍了该变桨距垂直轴风力发电机的特点,并采用叶素理论和数值仿真方法对其气动性能进行了研究,结果表明此结构的变桨距垂直轴风力发电机在变桨距性能及叶片的强度和刚度方面更加优越,相信将对我国风力发电的发展起到一定的推动作用．     

基于可靠性框图的可靠性建模研究

针对传统可靠性仿真模型建模繁琐、编程困难的问题,以可靠性框图为基础,设计了基于ExtendSim的可靠性建模流程,以两单元并联可修系统为例,建立了基于“致命修复”和“即坏即修”策略的仿真模型,并与解析模型进行了对比验证.仿真结果表明建立的可靠性模型是可信的,且此建模方法易于工程技术人员掌握,具有一定的推广价值．