机械零件抗断裂疲劳寿命可靠性预测与设计

根据金属疲劳裂纹扩展理论，对机械零件断裂疲劳强度可靠性进行了探讨，提出了一种新的疲劳寿命可靠性预测与设计方法。     

Improving the life and reliability of sealing cuffs

Diffusional surface modification of sealing cuffs made of oiland benzene-resistant rubber halves their frictional coefficient and increases their life by a factor of almost six. This effect is seen at pressures up to 40 MPa. The results are confirmed by calculations and experiments.     

结构疲劳寿命、可靠性可视化技术与虚拟疲劳设计

介绍了大型图形用户界面有限元软件、疲劳寿命预测模型、疲劳寿命可视化,可靠性可视化实现方法等结构疲劳寿命以及可靠性可视化技术,阐述了先进的基于“全场”疲劳寿命,可靠性可视化技术的产品虚拟疲劳设计思想,以有限元软件ANSYS为平台,自行开发了基于结构疲劳寿命,可靠性可视化技术的外部模块,并采用该模块对某战斗机起落架框进行了“全场”疲劳寿命,可靠性可视化分析。     

机床刀具可靠性及寿命评估

为了评估金属切削刀具的可靠性,提出了机床切削刀具可靠度和平均寿命的概率评估方法,利用马尔科夫链蒙特卡洛法解决了描述刀具故障率的Weibull比例危险模型参数贝叶斯点估计及区间估计难题,所提评估方法可给出刀具可靠度、故障率、平均寿命及其下限的估计值。通过实例分析表明:刀具可靠度随切削用量和切削时间的变化非单调下降,而平均寿命随切削用量的变化而波动变化。所提方法综合考虑了切削用量和验前经验,给出的刀具可靠度和平均寿命估计更符合实际加工条件。     

疲劳试验机中增频等径凸轮机构的设计研究

针对某航空件的弯曲振动疲劳特性试验,设计了一种增频等径凸轮机构,应用于疲劳试验机,可在低速情况下获得较高的试验频率,既缩短了试验周期,又避免了高速时的振动、冲击等问题.     

汽车关键零部件的寿命定量设计

汽车关键件疲劳寿命定量设计是一种现代设计方法，它把定量疲劳寿命理论和试验相结合，使疲劳寿命由定性设计提高到定量设计，提高了设计水平，对于汽车制造商来说极具经济价值。     

某扭杆式双向平衡机的设计及疲劳寿命分析

为满足某炮架需要双向平衡的需求,采用实心扭杆与空心扭杆串联的方式,设计了某炮架的扭杆平衡机结构,并对其中的关键结构--扭杆进行了强度、刚度校核.由于当前一般的平衡机设计仅为单向平衡,因此针对双向平衡可能带来的风险,通过预扭试验证明了扭杆式双向平衡机的可行性.双向平衡机工作在交变应力状态下,为了预测其疲劳寿命,运用有限元方法进行了疲劳寿命分析,为其使用和维护提供了有力支持.     

难刨煤层刨刀可靠性与疲劳寿命研究

基于Pro/E,ADAMS,ANSYS,Matlab与nSoft构造联合仿真平台,建立了某滑行刨煤机刨头的刚柔耦合虚拟样机模型.通过对某难刨煤层赋存条件的研究,生成了实际工况下刨刀的三向力载荷文件.提出了减少煤脊残留的非对称方式布置的新型刨刀,并对传统刨刀与新型刨刀在煤质韧性较高,煤层次生性裂隙极不发育的工况下所受的最大主应力与疲劳寿命进行了对比分析.结果表明:两种刨刀所受最大主应力基本相等,但传统刨刀在刨削难刨煤层过程中将随着煤脊的残留而无法继续工作,而以左右非对称方式布置的新型刨刀既消除了煤脊的残留,同时又提高了刨刀工作的可靠性、延长了刨刀使用寿命.     

Principle of maximum entropy for reliability analysis in the design of machine components

Frontiers of Mechanical Engineering - We studied the reliability of machine components with parameters that follow an arbitrary statistical distribution using the principle of maximum entropy...     

基于威布尔分布的疲劳剩余寿命可靠性预测方法

在变应力作用下,机械零件的疲劳寿命为具有分散性的随机变量.威布尔分布是一种连续的概率分布,可以用来描述各种不确定因素对机械零件疲劳寿命的影响.文中用三参数威布尔分布描述零件疲劳寿命的分布规律,建立疲劳剩余寿命的分布模型,并采用解析方法获得疲劳寿命分布参数的点估计值.对在同一应力水平下疲劳剩余寿命的分布规律进行了探讨,结果表明:当前年龄越大,可靠度曲线越陡峭,疲劳剩余寿命的可靠度越低;而年龄越小,疲劳剩余寿命的概率密度曲线越平坦,剩余寿命的分散性越大.     

Determination of fragments of multiaxial service loading strongly influencing the fatigue of machine components

The paper presents a method for determination of multiaxial load segments from original service histories, where the loaded machine part is meaningfully subjected to fatigue damage. These load segments are directly separated from a service-loading history, which can be of a random character. Typical procedures used for fatigue life assessment under multiaxial random loading are implemented to perform this task. While reduction from the multiaxial stress state to the equivalent uniaxial one, application of the linear multiaxial fatigue failure criteria was proposed. The equivalent stress history is subjected to the rainflow cycle-counting method, which allows to determine the amplitudes and mean values of counted cycles, their occurrence moment and time of duration. Influence of the stress mean value was taken into consideration with the Morrow's model. On the assumption of the linear Palmgren–Miner hypothesis of damage accumulation and the stress–life fatigue characteristics of the material, the damage-time function was determined. The load segments, where the influence on the material fatigue was significant, were determined on the basis of the fixed damage-intensity level and the proposed damage-intensity function. The presented method was studied on a hook loaded with two independent forces. FEM program which has the possibility to perform fatigue analysis was used during the computation for determining the expected place of crack initiation. The service-loading course was compressed to shorter one, so that only a small decrease of the fatigue damage in comparison with full length of the original service loading was observed. The proposed method seems to be right for preparing multiaxial loading histories in order to cut down the fatigue tests, especially in the case when the correlation between particular loading channels is very important.     

Duplex positioning method for increasing the fatigue life of threaded connections under eccentric loading

A new method, duplex positioning method DPM, to increase the fatigue lifetime of the threaded connection under eccentric loading is presented. When DPM is applied, the most damaged stud regions periodically are removed from risky positions by a change of the stud’s and nut’s mutual position in the axial direction alongside with a change of the stud’s position in respect to bending plane. The mathematical model for DPM enables us to predict its efficiency. To simulate the fatigue strength of the stud the following was used: Patterson’s and Kenny’s thread deflection factors, solutions for the distributions of the axial load and bending moment along the threads, Neuber’s method for the stress concentration factors in multiplier notches, Heywood’s formulas for the stress due to the thread flank loading and for the combined stresses, as well as the results of the photoelastic analysis of the araldite models under eccentric loading.

     

Probabilistic fatigue life prediction methodology for notched components based on simple smooth fatigue tests

The methodology of probabilistic fatigue life prediction for notched components based on smooth specimens is presented. Weakestlink theory incorporating Walker strain model has been utilized in this approach. The effects of stress ratio and stress gradient have been considered. Weibull distribution and median rank estimator are used to describe fatigue statistics. Fatigue tests under different stress ratios were conducted on smooth and notched specimens of titanium alloy TC11. The proposed procedures were checked against the test data of TC11 notched specimens. Prediction results of 50 % survival rate are all within a factor of two scatter band of the test results.     

工程机械金属结构疲劳可靠性分析的响应面法

研究了响应面法在分析工程机械金属结构疲劳可靠性时的应用。求解疲劳可靠性时若将结构的材料、几何尺寸、载荷等视为基本随机变量,功能函数不能表达为基本随机变量的显式函数。本文运用商业有限元软件对结构进行计算,由响应面法构造功能函数二次多项式,再结合JC法或改进的一次二阶矩法求解疲劳可靠度。文中对160t铁路救援起重机伸缩臂结构其进行了疲劳可靠度计算。     

注射机导柱断裂成因分析及疲劳寿命预测

橡胶注射机合模机构中的导柱在承受复杂载荷工况下,使用1.5年半左右发生疲劳断裂。因此采用数值模拟技术对合模机构进行力学性能分析,寻找断裂原因。根据合模机构的结构和载荷的对称性,取模型的四分之一作为几何求解域,以面-面接触方式定义多区域非线性接触关系,采用粘接模型简化螺纹连接,模拟结果表明导柱颈部的应力集中是其断裂的主要成因,且模具的接触面积越小,导柱颈部的应力越大。采用电测法对合模机构正常工作下的应力水平进行实测,实测结果与数值模拟结果相吻合。在此基础上,对合模机构进行了结构改进,分别计算结构改进前后的疲劳寿命,对比发现改进后的导柱寿命明显提高。     

Fatigue life evaluation of mechanical components using vibration fatigue analysis technique

Unit brackets attached on a cross member and subjected to random loads often fail due to self-vibration. To prevent such failures, it is necessary to understand the fatigue failure mode and to evaluate the fatigue life using test or analysis techniques. The objective of this study is to develop test specifications for components, which are applicable to predict fatigue life at the stage of initial product design, for the unit brackets by using a vibration fatigue technique. For this objective, the necessity of a fatigue analysis considering resonant effect was reviewed. Also, a series of vibration fatigue analyses were carried out by changing the acceleration’s direction and magnitude. Then, a methodology was proposed to determine the optimum vibration fatigue test specification of the component, which gives an equivalent failure mode with the vehicle test condition.     

谐波齿轮传动柔性轴承疲劳寿命试验装置设计

根据谐波齿轮传动柔性轴承疲劳寿命测试需求,设计了能够模拟实际工作状态的柔性轴承疲劳寿命试验装置,避免了传统采用谐波齿轮传动整机进行试验的方法中,柔轮和刚轮等高成本零件的消耗问题,阐述了模拟试验装置的设计原理和机械系统设计,在模拟试验装置上对3E812KAT2型柔性轴承进行了疲劳试验,验证了试验装置设计原理的可行性。