估计疲劳寿命三参数P-S-N曲线的新方法

由于不同应力水平下对数疲劳寿命的方差不等,因而不同应力水平下的对数疲劳数据不满足最小二乘估计的Gauss-Markov假设条件,此时采用常规最小二乘法估计的三参数P-S-N曲线不是统计意义下的最佳线性无偏估计,而加权最小二乘法则可以给出异方差条件下的最佳线性无偏估计.为此基于加权最小二乘和Bootstrap方法提出一种疲劳寿命三参数P-S-N曲线估计方法,在所提方法中,Bootstrap方法被用来确定不同应力水平下疲劳试验寿命数据的协方差矩阵对角线元素,避免迭代确定加权最小二乘法中的权矩阵.对三种材料的四组疲劳试验寿命数据进行分析的结果表明,所提方法具有工程实用性,传统最小二乘法由于忽略了Gauss-Markov假设条件可能得到偏危险的结果,而由于所提方法得到的是最佳线性无偏估计,因而在子样容量增大时将趋于估计的真值,并且参数估计的方差将是最小的.     

疲劳试验数据任意置信度下C-R-S-N曲线的计算机辅助拟合

利用三参数威布尔分布对疲劳试验数据进行５０％置信度下的分布拟合,根据拟合结果,进一步利用最小二乘法对任意置信度（除５０％外）下的分布按二次曲线进行拟合。以此为基础,用一元线性回归法可求得任意置信度下的可靠度－应力－寿命曲线和疲劳极限。从而为可靠性设计提供更为全面的基础数据。     

疲劳试验数据任意置人度下分布的曲线拟合法改进

以对齿轮的疲劳试验寿命数据处理为例,叙述了一种以双曲线函数为原型同线拟合方法,来求取任意置信度Ｃ下的分布曲线,从而有效地改善了以一般二次函数为原型拟合时所出现的问题,即使拟合的曲线通常为抛物线,无法延伸到高可靠度区域。     

疲劳试验数据任意置信度下分布的曲线拟合法改进

以对齿轮的疲劳试验寿命数据处理为例,叙述了一种以双曲线函数为原型的曲线拟合方法,来求取任意置信度Ｃ下的分布曲线,从而有效地改善了以一般二次函数为原型拟合时所出现的问题：即使拟合的曲线通常为抛物线,无法延伸到高可靠度区域。     

25Cr2MoV 气体渗氮齿轮弯曲疲劳强度的试验研究

论述25Cr2MoV深层渗氮齿轮弯曲疲劳强度的试验研究。试验在英国产STRON1603型电磁谐振疲劳试验机上进行。短寿命区采用四级恒定应力水平的成组试验法,长寿命区采用应力升降试验法。在试验数据基础上,根据统计学原理,拟合出完整的C-R-S-N曲线,并获得各种置信度和可靠度下的弯曲疲劳极限值。     

用三参数威布尔分布求升降法试验的疲劳极限

在一定置信度下,运用优化的方法对机械零件升降法疲劳试验数据进行三参数威布尔分布参数估计,并求出一定可靠度下的疲劳极限应力。     

无失效数据场合智能换刀机器人中轴承的可靠性评估

在目前无失效数据可靠性评估方法中,采用一个模型很难同时得到参数的点估计和置信区间估计。如果采用不同方法分别进行点估计和区间估计,则会造成结果的一致性问题。为此在无失效数据情况下对某型号智能换刀机器人系统中转动关节处的滚动轴承进行可靠性分析,提出一种新的无失效数据可靠性评估模型。新模型采用E-Bayes方法推导出产品寿命概率分布曲线,进而得到产品可靠度的点估计。再利用参数Bootstrap法从寿命概率分布中重新抽取新样本,通过新样本获得产品可靠度的区间估计。在不降低结果可信度的情况下,同时得到产品可靠度的点估计和区间估计。算例分析结果表明,在威布尔分布条件下,新模型不仅能够满足可靠性评估的要求,还可以提高可靠度区间估计精度。所提模型已经验证在进行无失效数据可靠性评估过程中具有良好的可行性,且便于工程应用。     

37SiMn2MoV调质齿轮弯曲疲劳强度的试验研究

论述37SiMn2MoV调质齿轮弯曲疲劳强度的试验研究.在试验数据的基础上,根据统计学原理,拟合出完整的C-R-S-N曲线,并获得指定置信度下,各种可靠度时的弯曲疲劳曲线,从而为国产材料齿轮设计提供了必要的基础数据.     

置信度条件下轴承寿命的可靠度分析

汽车轴承的寿命一般有置信度下可靠度的要求。基于Bayes方法分析确定了可靠度和置信度的关系,进一步采用中间秩确定了轴承给定置信度和可靠度的额定寿命修正系数,最后给出了验证置信度和可靠度的寿命试验方案的制定方法。     

高置信度的载荷与寿命消耗折算方法

在载荷谱编制和单机寿命监控中常常需要进行载荷折算和寿命消耗折算，传统的未考虑置信度的折算方法，往往将载荷和寿命消耗折算小了，导致结果偏于危险，为此本文提出一种高置信度的载荷与寿命消耗折算方法。文中首先研究了载荷折算与置信度、可靠度的关系，结果表明在置信水平为γ、可靠度为R的定寿延寿中，应采用置信水平为γ、可靠度为R的P-S-N曲线进行载荷折算，而只有在方差相等的情况下，才可以采用置信水平为γ的中值S-N曲线进行载荷折算。然后建立了方差相等时中值S-N曲线斜率的单侧置信下限小样本评估方法，给出了方差未知和方差已知两种情况下的斜率置信下限计算公式。在此基础上，针对载荷谱编制，建立了其高置信度的载荷折算公式。针对单机寿命监控，在方差相等或已知的情况下提出了载荷谱当量应力水平计算公式，并采用整机试验结果对中值S-N曲线进行了修正，建立了任一应力水平下的置信水平为γ、可靠度为R的可靠寿命单侧置信下限计算公式，给出了将实际使用载荷转换为标准载荷或试验载荷谱上消耗的循环数公式，以及其置信水平为γ、可靠度为R的可靠寿命消耗百分比（即损伤）单侧置信上限公式，从而能够更加精准、更加简便地对产品进行单机寿命...     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...