起重机门架结构的疲劳寿命分析

重点介绍利用断裂力学理论进行门式起重机结构的疲劳寿命分析的方法,通过运用损伤容限设计方法对门架结构进行的疲劳寿命计算,得出了门机主梁与悬臂梁联结部位初始裂纹为0.5mm时门架结构的设计寿命,并分析了模型中参数变化对门架结构寿命的影响,说明利用该方法估算门架结构的寿命具有可行性,对实际工程具有参考价值。     

随机载荷作用下微车车身结构疲劳寿命仿真分析

以微型车车身结构为研究对象,合理简化结构后建立车身有限元模型,确定载荷形式后,对车身进行静应力分析。以应力分析计算结果为基础,在动力学软件中计算获取车身承受的随机载荷,结合材料的S-N曲线和线性累积损伤理论,运用Goodman平均应力修正法,对车体进行全寿命疲劳分析,根据车身疲劳分析结果可知,该微型车车身结构疲劳寿命满足强度和疲劳性能要求。     

Contact fatigue life prediction of a bevel gear under spectrum loading

Rolling contact fatigue (RCF) issues, such as pitting, might occur on bevel gears because load fluctuation induces considerable subsurface stress amplitudes. Such issues can dramatically affect the service life of associated machines. An accurate geometry model of a hypoid gear utilized in the main reducer of a heavy-duty vehicle is developed in this study with the commercial gear design software MASTA. Multiaxial stress–strain states are simulated with the finite element method, and the RCF life is predicted using the Brown–Miller–Morrow fatigue criterion. The patterns of fatigue life on the tooth surface are simulated under various loading levels, and the RCF S–N curve is numerically generated. Moreover, a typical torque–time history on the driven axle is described, followed by the construction of program load spectrum with the rain flow method and the Goodman mean stress equation. The effects of various fatigue damage accumulation rules on fatigue life are compared and discussed in detail. Predicted results reveal that the Miner linear rule provides the most optimistic result among the three selected rules, and the Manson bilinear rule produces the most conservative result.     

A thermodynamic approach for predicting fretting fatigue life

This paper extends the application of the theory of continuum damage mechanics (CDM) to predict the occurrence of fretting fatigue failure. It is concerned with the application of thermodynamic theory of CDM for predicting crack formation in fretting. This is done by calculating subsurface shear stress distribution due to fretting loading conditions and obtaining corresponding principal plane location. For given fretting conditions such as the load, the coefficient of friction and the bulk material properties, the present model predicts the number of cycles to failure. The results are validated with published experimental data.     

Assessment of fatigue life of remanufactured impeller based on FEA

Predicting the fatigue life of remanufactured centrifugal compressor impellers is a critical problem. In this paper, the S-N curve data were obtained by combining experimentation and theory deduction. The load spectrum was compiled by the rain-flow counting method based on the comprehensive consideration of the centrifugal force, residual stress, and aerodynamic loads in the repair region. A fatigue life simulation model was built, and fatigue life was analyzed based on the fatigue cumulative damage rule. Although incapable of providing a high-precision prediction, the simulation results were useful for the analysis of fatigue life impact factors and fatigue fracture areas. Results showed that the load amplitude greatly affected fatigue life, the impeller was protected from running at over-speed, and the predicted fatigue life was satisfied within the next service cycle safely at the rated speed.     

门座起重机金属结构疲劳寿命测试与估算

针对西基港务公司门座式卸船机的老化问题，并考虑到起重机金属结构在安全管理中的重要性，对2号门座起重机金属结构进行系统测试与评定，提出今后管理工作的重点，确保今后安全可靠地生产。     

基于生物力学分析Q值对颈肌疲劳的反映效果

颈肌疲劳是导致颈椎病的主要原因之一。为了有效预测和缓解颈肌疲劳,结合生物力学理论分析了表面肌电信号(SEMG)对颈部肌肉疲劳状态的反映效果。选取身体健康,年龄在21~33岁的8名志愿者作为被试者。所有被试者保持屈颈位2h,采集颈6、颈7节段两侧上斜方肌的表面肌电信号。首先,采用经验模态分解(EMD)对肌电信号进行去噪;然后,提取并分析了积分肌电(IEMG)、近似熵(ApEn)、疲劳状态指标Q值等3种特征参数在屈颈过程中的变化规律。实验结果表明,随着屈颈时间的增加,积分肌电值呈上升趋势,近似熵和疲劳状态指标Q值呈下降趋势;其中,状态指标Q值对颈肌疲劳的反映效果最好,表现在数据稳定、差异明显、同生物力学分析相一致。本实验条件下,颈6、颈7节段肌电信号屈颈疲劳前后Q值的均值由0.37降低至0.21,采用按摩缓解后又恢复到0.33。本研究内容对长期处于屈颈位人群预防颈肌疲劳,减少颈椎病的发生具有重要的指导意义。     

Fretting fatigue life prediction using the extended finite element method

In this work, an efficient procedure to predict fatigue lives in fretting fatigue problems is presented. This is accomplished by means of a combined initiation-propagation approach in which the extended finite element method (X-FEM) is used. The procedure is verified by modelling several fretting fatigue tests available in the literature. The application of the X-FEM enables to numerically evaluate the stress intensity factors (SIFs) for cracks of different lengths emanating at the end of the contact zone and to estimate the propagation life corresponding to each of the tests. This propagation life is combined with the initiation life calculated using a multiaxial fatigue criterion (Fatemi-Socie). The predicted lives are then compared with the reported experimental lives, showing that the consideration of the crack-contact interaction through the numerical models tends to improve the life estimation when compared with a fully analytical approach. The procedure can be applied to more general fretting problems for which analytical solutions are not available.     

Fatigue characteristics of bearing steel in very high cycle fatigue

Very high cycle fatigue (VHCF) tests were carried out to find the fatigue characteristics of a super-long life range by using a cantilever type rotational bending fatigue test machine on three kinds of specimens in bearing steel which were quenched and tempered in air (A: non-shot peened and B: shot peened after heat treatment) and under vacuum environment(C: non-shot peened) in this study. S-N curves obtained from the VHCF tests of the B and C specimens tend to come down again in the super-long life (10⁹ cycles) range due to fish-eye type cracking, while most of the A and B specimens were fractured by surface defects such as scratches and slip lines. This duplex S-N behavior of bearing steel has to be reviewed by the change of the fracture modes. This paper was recommended for publication in revised form by Associate Editor Youngseog Lee Chang-Min Suh received his B.S. and M.S. degrees in mechanical engineering from Busan Na-tional University in 1964 and 1968, respectively, and received his Ph.D. degree from the University of Tokyo in 1981. He now is a professor at Kyungpook National University. He has served as the Head of the Department of Mechanical Engineering at Kyungpook National University, a Visiting Professor of Materials Science and Engineering in Univ. of California Berkeley, a Head of the Institute of Engineering Design Technology Kyungpook Nat’l Univ, and a Head of the Technology Innovation Center designated by the Department of Commerce and Industry of Korea.     

Residual fatigue life prediction of ball bearings based on Paris law and RMS

Paris law can reflect the failure mechanism of materials and is usually used to be a method to predict fatigue life or residual fatigue life.But the variable which can represent the health of machine i...     

电驱动换挡机构疲劳寿命试验系统设计

根据电驱动换挡机构疲劳寿命试验要求,设计开发了基于电驱动换挡机构疲劳寿命为评价指标的试验系统;并就系统的组成、工作原理和测控软件等进行了详细介绍。经试验验证,该系统稳定可靠,操作方便,很好地满足了电驱动换挡机构疲劳寿命试验的要求。目前,该系统已在多款电驱动换挡机构研发阶段取得了良好的应用效果。     

考虑疲劳可靠性的回转压头锁紧碟簧稳健设计

结合可靠性设计理论和稳健设计技术,以碟簧的疲劳可靠性为约束,碟簧组的轴向载荷及其方差为目标函数,建立了夹紧装置碟簧的稳健性优化模型,并进行了稳健优化。同时考虑了碟形弹簧各设计参数的不确定性对碟簧疲劳寿命和碟簧特性的影响,提高了设计结果的经济性和可靠性。     

应用遗传算法优化支持向量机的疲劳裂纹扩展预测

准确讯速地预测疲劳裂纹的扩展进程具有十分重要的现实意义和显著的经济效益.为了实现疲劳裂纹长度的准确预测,提出基于遗传算法优化支持向量机(GA-SVM)的疲劳裂纹扩展预测方法,其中遗传算法用于确定SVM中的训练参数,得到优化的SVM预测模型.试验结果表明:用GA-SVM对疲劳裂纹长度进行预测具有很好的预测精度.     

基于ANSYS/FE-SAFE的液压扳手连杆疲劳寿命仿真分析

使用UG软件对液压扳手进行三维建模,分析关键部件连杆在工作中所受的载荷,通过ANSYS软件与FE-SAFE软件的结合,对液压扳手连杆在工作时所受的交变载荷进行仿真并计算出其使用寿命。仿真结果与试验数据的对比结果表明,该仿真分析方法可靠,可为液压扳手其他零部件的疲劳寿命分析提供一种可行的思路。     

面向质量的集成产品开发决策研究

面向质量的集成产品开发能够有效地指导企业进行有竞争力产品的开发。本文讨论了面向质量的产品开发思想指导下的产品开发决策过程。并以开发过程中产生的产品概念设计方案集为对象,建立了评价选优的指标体系和基于模糊优选理论的决策模型。     

基于PDM的CAx集成技术研究

信息共享在产品开发过程中十分重要,基于ＰＤＭ的ＣＡｘ信息集成为开发者提供一个协同的工作环境,确保ＣＡｘ产生的数据的唯一性。本文根据作者参加了在西安飞机制造（集团）有限公司并行工程的实施和对ＩＢＭ公司ＰｒｏｄｕｃｔＭａｎｇｅｒ的认识,初步探讨了ＣＡｘ与ＰＤＭ的集成方案,以及ＣＡｘ信息集成管理的内容,并介绍了ＣＡｘ分系统之间的信息集成途径与技术。     

基于Cruise的PHEV动力总成集成控制研究

针对目前PHEV动力总成系统各部件协调控制的不足,对混合动力汽车多能源动力总成的集成控制进行了研究,提出了一种动力总成部件的系统集成控制方法。依据发动机、电机、蓄电池、动力耦合器等各部件电控单元ECU的属性及特点,构建了动力总成各主要部件ECU的模型,以此为基础搭建了集成系统的协调框架,利用系统ECU实时监测各动力部件ECU的工作状态和环境状态,结合逻辑门限阈值控制和状态流程图,判断总成系统的工作模式,并在Matlab/Simulink和Cruise环境下进行了控制策略的联合仿真验证。研究结果表明,PHEV动力总成的集成控制策略具有良好的控制效果,有效适应了外界工况的变化,改善了发动机的工作点并且降低了燃油消耗,解决了总成各部件的动力匹配与协调控制问题。     

New optimization method, the algorithms of changes, for heat exchanger design

Heat exchangers are widely used in the process engineering such as the chemical industries,the petroleum industries,and the HVAC applications etc.An optimally designed heat exchanger cannot only help the optimization of the equipment size but also the reduction of the power consumption.In this paper,a new optimization approach called algorithms of changes (AOC) is proposed for design and optimization of the shell-tube heat exchanger.This new optimization technique is developed based on the concept of the book of changes (I Ching) which is one of the oldest Chinese classic texts.In AOC,the hexagram operations in I Ching are generalized to binary string case and an iterative process,which imitates the I Ching inference,is defined.Before applying the AOC to the heat exchanger design problem,the new optimization method is examined by the benchmark optimization problems such as the global optimization test functions and the travelling salesman problem (TSP).Based on the TSP results,the AOC is shown to be superior to the genetic algorithms (GA).The AOC is then used in the optimal design of heat exchanger.The shell inside diameter,tube outside diameter,and baffles spacing are treated as the design (or optimized) variables.The cost of the heat exchanger is arranged as the objective function.For the heat exchanger design problem,the results show that the AOC is comparable to the GA method.Both methods can find the optimal solution in a short period of time.     

集成封装发光二极管光提取效率的计算及优化

基于蒙特卡罗方法模拟、计算并分析了芯片类型、大小、间距、数量以及布局对GaN基发光二极管(LED)集成封装器件COB(Chip On Board)能效的影响。计算结果表明:在芯片间距小于200μm且芯片尺寸或布局等参数相同的条件下,正装LED COB的能效最低,其次为倒装LED COB,垂直结构芯片的能效最大。当芯片间距大于200μm,3种LED COB的能效趋向饱和。芯片尺寸增加或数量减少可使正装和倒装芯片COB的能效上升,而垂直结构COB的能效基本保持不变。加入图形衬底可提高同样尺寸或布局的正装芯片COB封装器件的能效,但使倒装芯片COB的能效恶化。分析表明:芯片的侧面出光量占整个芯片出光量的比值以及相邻芯片材料的吸收对3种类型COB封装器件的能效有决定性影响。文中还针对正装芯片COB设计了新型菱形芯片布局,与常规正方形芯片布局的COB相比,其能效提高了6.2%。     

基于集成战略的工业维护管理理论体系的构建

介绍了工业维护管理发展的背景和原因，给出了工业维护管理的内涵和外延，构建了由哲理层、方法论层、应用实现层和技术工具层组成的工业维护管理理论体系结构，并提出了工业维护管理的实现模式，包括维护管理信息系统、维护决策支持系统、维护质量控制系统、维护操作过程系统、维护对象／资源管理系统和维护成本控制系统。