刚度耦合影响下的变速器箱体结构动态分析及疲劳寿命预估

研究某车用手动变速器箱体与轴系刚度耦合下的结构响应和疲劳状况。首先建立变速器箱体有限元模型并通过模态试验进行了校核。然后基于ROMAX软件建立了考虑齿轮、轴系及变速器箱体柔性的变速器结构动力学耦合分析模型,通过对不同档位工况下的运转进行了精确计算得到了各轴承处的激励频谱曲线。在此基础上,对不同档位下发动机最大扭矩时箱体的耦合模型进行了动响应计算,获得了危险区域应力幅值的分布情况。最后采用振动疲劳样本法对变速器箱体危险区域的疲劳寿命进行了计算与分析。     

基于流固耦合的混流式水轮机转轮应力分析

混流式水轮机转轮在正常运行时,会因为水利因素导致转轮叶片发生疲劳断裂或者出现裂纹,为了让机组在合适的工况和频域区间运行,避免因为应力或是振动等问题发生叶片失效。基于流固耦合理论,采用顺序耦合法,通过建立转轮模型、CFD分析、流固耦合应力分析以及振型仿真等操作,分析额定工况和飞逸工况下的运行规律。     

基于ABAQUS的离心叶轮力学性能研究

介绍了离心叶轮疲劳破坏的原因,利用有限元方法,通过对离心叶轮模态与尾流激振响应分析,研究了离心叶轮是否发生轮盘叶片耦合振动及单只叶片振动,得到危险工况点,计算出离心力、稳态气流力及非稳态交变应力,运用Goodman的方法修正载荷谱,并计算出疲劳寿命。     

锻造模具的随机疲劳损伤分析

塑性应变控制的低周疲劳失效是锻造模具的主要失效形式，由于受到多种因素的影响，其损伤过程呈现随机性。应用有限元与BP神经网络，建立了一种基于损伤累积理论的锻造模具的随机疲劳损伤分析模型。首先用有限元对锻造过程中模具内的场变量进行分析，由计算结果找到模具的危险部位，认为危险部位失效时的寿命即为模具寿命，并计算出确定性损伤；再考虑模具材料及实际工况的随机性，应用BP神经网络对模具的损伤进行模拟；根据损伤的累积效应，得出考虑随机因素作用下的模具疲劳寿命。以锻造齿轮模作为分析对象，得到不同工况下模具疲劳寿命的频数分布，其分布规律基本服从Weiubull分布。另外，还分析了打击速度对模具寿命的均值和离差的影响及可靠性随使用次数的变化。该 模型可用来对模具进行寿命预测和可靠性分析。     

压气机中叶片与叶盘耦合系统振动特性研究

基于有限元方法建立某型航空发动机压气机叶片模型,通过模态仿真获得了该叶片在榫头固支约束下的动力学特性,研究了离心力对叶片振动的影响,并通过模态试验对计算模型和仿真数据进行验证;利用循环对称法对建立的叶片轮盘有限元模型进行振动分析,获得叶轮耦合系统在不同工作转速下的振型和频率,并与单个固支叶片进行比较,结果表明,相同阶次下叶片耦合系统的自振频率较低;通过Campbell图分析得出了叶片耦合系统可能发生共振的频率及相应的转子转速,为其故障诊断、可靠性分析以及寿命估算提供了参考依据。     

非典型气动荷载下压缩机叶轮疲劳强度分析

针对气动激励下压缩机叶轮疲劳破坏问题,研究气动激振力的频域特性以及叶轮共振特性,提出相应的叶轮疲劳强度校核及失效分析方法。对某离心压缩机叶轮非定常气动荷载计算流体力学(Computational fluid dynamics,CFD)计算结果进行傅里叶变换,获得其频率、幅值与相位特征,重点分析气动激振荷载在相邻叶片间的相位关系。对于在相邻叶片间相位差循环对称分布的典型荷载分量,通过干涉图确定叶轮的共振模态,对于相位差非循环对称分布的非典型荷载分量,通过激振频率下叶轮动应力在各节径的分布情况确定叶轮的共振模态。基于叶轮静应力和共振动应力计算结果进行疲劳分析。结果表明,计算预测的疲劳破坏位置与实际发生疲劳裂纹位置相吻合,相位差非循环对称分布的非典型气动荷载激起叶轮零节径的共振是引起叶轮疲劳失效的主要原因。     

高压压气机转子叶片振动特性分析

基于ANSYS软件对某型航空发动机高压压气机第一级转子叶片的振动特性进行了分析研究,建立了叶片的三维有限元模型,采用分块Lanczos法,计算得到了叶片在发动机常用工况转速下的各阶自振频率、相应振型及振动应力分布,找出了应力较大的薄弱区域.最后考虑了高压压气机进口导流叶片后形成的气流尾迹对此级转子叶片的激振影响,得到该级转子叶片的共振图,结果证明该转子叶片在常用工况转速下,不会因为进口导流叶片后的气流尾迹引发共振.为叶片的后续结构分析、实验及振动排故提供了必要的数值依据.     

基于ANSYS兆瓦风力发电机叶片疲劳寿命分析

叶片作为风力发电机组最核心的部件,其主要的损坏形式为疲劳损坏。为了确保风力发电机组运行安全可靠,风电机组设计时,必须对叶片进行疲劳寿命分析。以1.2MW级风电叶片为例,建立了风电叶片和风轮的三维几何模型,依据Weibull两参数分布函数确定某风场风速分布数据。采用ANSYS Workbench软件对风轮模型进行流固耦合数值仿真分析,进而对叶片模型进行线性静态结构分析以及疲劳分析,提取风电叶片在典型风速工况下的危险节点位置及对应的等效应力值。最后结合线性疲劳累计损伤理论计算风电叶片的疲劳寿命。仿真结果表明,实验叶片满足设计要求。     

高耸塔器风致疲劳寿命时域分析

针对沿海多风地区高耸塔器可能因长期风致振动导致的疲劳问题,以随机风致应力响应的时程模拟、风速风向联合分布模型、雨流法以及Miner疲劳累积损伤理论为基础,提出了基于时域法的高耸塔器风致疲劳寿命数值计算方法,并针对某一典型高耸塔器进行了相关分析。结果表明：长时间的空塔工况可能导致该塔器严重的疲劳损伤甚至失效,而操作工况下的风致疲劳寿命一般可以满足设计年限要求;横风向共振是引起该塔器空塔工况风致疲劳的决定性因素,而强风造成的顺风向振动是导致其操作工况下疲劳损伤的主要原因;该塔器空塔和操作工况下的疲劳分布曲线分别呈多峰型和单峰型,可见顺风向的疲劳损伤比横风向更为集中。     

带预载的钢丝网套补偿器振动疲劳损伤分析

开展了基于有限元分析软件ABAQUS的钢丝网套补偿器在随机振动工况和正弦振动工况下的疲劳分析.首先采用梁单元建立钢丝网套等效模型,针对不同载荷工况构建不同的钢丝网套与波纹管间的相互作用关系,从而建立能够考虑预载影响的钢丝网套补偿器随机振动、正弦振动分析模型,并开展支反力试验和模态测试对模型进行验证.基于该模型,结合Dirlik方法及基于Miner线性累积损伤理论推导的疲劳寿命计算公式.分析了不同方向随机振动、正弦振动激励作用下的钢丝网套补偿器疲劳损伤情况.结果 显示,在随机振动工况和正弦振动工况下,钢丝网套补偿器在横向(X方向)上的损伤均最大,且在设计使用寿命(1 min)以内均未发生疲劳破坏;钢丝网套补偿器的薄弱环节分布于补偿器个别波峰以及管接头固定端附近;正弦振动工况下损伤水平小于随机振动工况下损伤水平.     

Modal characteristics and fatigue strength of compressor blades

High-cycle fatigue (HCF) has been identified as one of the primary causes of gas turbine engine failure. The modal characteristics and endurance strength of a 5 MW gas turbine engine blade developed by Doosan Heavy Industries & Construction Co., Ltd. in HCF fracture were verified through analysis and tests to determine the reliability of the compressor blade. A compressor blade design procedure that considers HCF life was performed in the following order: airfoil and blade profile design, modal analysis, stress distribution test, stress endurance limit test, and fatigue life verification. This study analyzed the Campbell diagram and estimated resonance risk on the basis of the natural frequency analysis and modal test of the compressor blade to guarantee safe and operational reliability. In addition, the maximum stress point of the compressor blade was determined through stress distribution analysis and test. The bonding point of the strain gage was determined by using fatigue test. Stress endurance limit test was performed based on the results of these tests. This research compared and verified the modal characteristics and endurance strengths of the compressor blades to prevent HCF fracture, which is among the major causes of gas turbine engine damage. A fatigue life design procedure of compressor blades was established. The 5 MW class gas turbine compressor blade is well designed in terms of resonance stability and fatigue endurance limit.     

压气机叶片流固耦合的强度和振动研究

为了研究流固耦合场对叶片强度与振动参数的影响,采用流体动力学和有限元方法,对压气机叶片进行了单向流固耦合分析。通过软件之间的接口,实现压力场数据的传递,并对加载气动力后的计算模型进行强度分析和模态分析,得到压气机大小叶片的应力应变云图以及固有频率和相应的模态振型,计算比较了离心力、气动力对应力和固有频率的影响。计算结果表明,流固耦合对叶片的结构强度和模态振型影响较小。通过频率分析,找出了叶片的共振频率,从而为叶片的优化提供依据。     

复杂载荷作用下压气机叶片疲劳寿命数值分析

为提高叶片服役寿命,在计算叶片应力分布并预测其在复杂载荷作用下的疲劳寿命后,基于逆向工程建立了三种不同精度的叶片模型;考虑离心和气动载荷作用,求解压气机叶片复合载荷作用下的应力分布规律;通过叶片模拟件疲劳试验,确定TC4钛合金疲劳极限,拟合寿命模型参数;利用非线性连续损伤力学模型预测叶片在典型工况下的疲劳寿命。结果表明：不同模型的应力及寿命计算值存在一定差异,开展叶片数值分析时,需考虑计算模型还原叶片几何特征的精度对计算结果的影响。     

Modal characteristics according to the tip shape and assembly condition of the turbine blade

To determine the reliability of a 5 MW gas turbine engine blade in high cycle fatigue (HFC) fracture being developed by Doosan Heavy Industries & Construction Co., Ltd., resonance characteristics are verified based on the turbine blade tip shape and assembly condition. In this study, the modal characteristics of compressor and turbine blades are investigated, and a Campbell diagram is established. During the preliminary study, modal analysis and holographic modal test of the first-, fifth-, and tenth-stage compressor blades were performed. Based on the preliminary study result, the natural frequency and Campbell diagram analysis for the turbine blades were performed. This research compared and verified the modal characteristic and resonance stability according to the tip shape and assembly condition of the blade to prevent any HCF fracture. In conclusion, the resonance stability of the shrouded blade is far superior to that of the squealer blade. Suitable assembly conditions must be applied.     

Dynamic test and fatigue life evaluation of compressor blades

High-cycle fatigue (HCF) has been identified as one of the primary causes of gas turbine engine failure. To verify the reliability of the high cycle fatigue fracture of the 5 MW gas turbine engine blade being developed by Doosan Heavy Industries & Construction Co., Ltd., dynamic tests were conducted using real size compressor rigs according to previous studies. The dynamic safety margin of the 5MW gas turbine engine blade was calculated on the basis of the ratio between the dynamic stress and endurance limit stress respectively determined through the compressor rig and fatigue tests. The HCF characteristics and the fatigue life stability of the DGT-5 compressor blades were verified through these processes. A fatigue life design procedure for the gas turbine compressor blade was established on the basis of the design, analysis, and test processes implemented in a previous study. In sum, the 5 MW class gas turbine compressor blades were found to be well designed in terms of resonance stability and fatigue life.     

Review on Stress Corrosion and Corrosion Fatigue Failure of Centrifugal Compressor Impeller

Corrosion failure,especially stress corrosion cracking and corrosion fatigue,is the main cause of centrifugal compressor impeller failure.And it is concealed and destructive.This paper summarizes the main theories of stress corrosion cracking and corrosion fatigue and its latest developments,and it also points out that existing stress corrosion cracking theories can be reduced to the anodic dissolution(AD),the hydrogen-induced cracking(HIC),and the combined AD and HIC mechanisms.The corrosion behavior and the mechanism of corrosion fatigue in the crack propagation stage are similar to stress corrosion cracking.The effects of stress ratio,loading frequency,and corrosive medium on the corrosion fatigue crack propagation rate are analyzed and summarized.The corrosion behavior and the mechanism of stress corrosion cracking and corrosion fatigue in corrosive environments,which contain sulfide,chlorides,and carbonate,are analyzed.The working environments of the centrifugal compressor impeller show the behavior and the mechanism of stress corrosion cracking and corrosion fatigue in different corrosive environments.The current research methods for centrifugal compressor impeller corrosion failure are analyzed.Physical analysis,numerical simulation,and the fluid-structure interaction method play an increasingly important role in the research on impeller deformation and stress distribution caused by the joint action of aerodynamic load and centrifugal load.     

内燃式水平对动空气压缩机的多工况动态特性分析

针对传统的内燃机驱动的活塞式空气压缩机工作过程中振动大,噪声大的问题,提出了内燃式水平对动空气压缩机原理方案,基于虚拟样机技术建立了内燃式空气压缩机曲轴轴系的动力学仿真模型。采用ADAMS软件对其进行了多种工况下的运动学和动力学分析,给出了作用在曲轴上的动态载荷及变化规律。运用有限元分析软件ANSYS对曲轴进行了模态分析,得到了曲轴前六阶模态的振型和响应的频率。建立了曲轴系刚柔混合体动力学模型,完成了内燃式水平对动空气压缩机曲柄连杆机构多柔体动力学仿真。     

叶片断裂破坏与气动非定常脉动的关联分析

在离心压气机实际的工况运行中,流量通常在一个区间内变化,如果流量超出稳定工作范围,在叶轮流道中可能会引起旋转失速甚至喘振等非稳定性流动现象,极易引发叶片的疲劳断裂[1].本文基于某型压气机在实际运行中发生叶片叶顶断裂事故,利用CFD软件NUMECA进行数值计算分析,主要从气动方面分析其在各个流量下的流动情况.从非定常流动特征方面深入分析其破坏机理.结果表明在一定的流量下,流场中的压力脉动非常强烈,极有可能引发叶片的疲劳破坏.本研究为压缩机叶片的疲劳破坏机理力学分析提供了可靠的理论依据和坚实的数据基础.     

Time-dependent vibration frequency reliability analysis of blade vibration of compressor wheel of turbocharger for vehicle application

Blade vibration failure is one of the main failure modes of compressor wheel of turbocharger for vehicle application. The existing models for evaluating the reliability of blade vibration of compressor wheel are static, and can not reflect the relationship between the reliability of compressor wheel with blade vibration failure mode and the life parameter. For the blade vibration failure mode of compressor wheel of turbocharger, the reliability evaluation method is studied. Taking a compressor wheel of turbocharger for vehicle application as an example, the blade vibration characteristics and how they change with the operating parameters of turbocharger are analyzed. The failure criterion for blade vibration mode of compressor wheel is built with the Campbell diagram, and taking the effect of the dispersity of blade natural vibration frequency and randomness of turbocharger operating speed into account, time-dependent reliability models of compressor wheel with blade vibration failure mode are derived, which embody the parameters of blade natural vibration frequency, turbocharger operating speed, the blade number of compressor wheel, life index and minimum number of resonance, etc. Finally, the rule governing the reliability and failure rate of compressor wheel and the method for determining the reliable life of compressor with blade vibration is presented. A method is proposed to evaluate the reliability of compressor wheel with blade vibration failure mode time-dependently.     

基于设计情形的叶片模态分析

针对某三叶片风扇,建立了叶片的有限元模型。通过对该模型进行模态分析,得到了叶片的固有频率和相应的模态振型,并分析了各阶振型下叶片的振动情况。通过不同的设计情形算例,分析了叶片材料弹性模量、泊松比、质量密度对叶片固有频率的影响。考虑叶片旋转工作状态下离心力会产生预应力的影响,通过加载旋转力矩,求解了多组设计情形的预应力下叶片的固有频率,计算结果表明,叶片的旋转状态会对叶片的振动特性产生影响,离心预应力会使叶片固有频率变大。