A nonparametric approach to accelerated life testing under multiple stresses

Accelerated life testing (ALT) is concerned with subjecting items to a series of stresses at several levels higher than those experienced under normal conditions so as to obtain the lifetime distribution of items under normal levels. A parametric approach to this problem requires two assumptions. First, the lifetime of an item is assumed to have the same distribution under all stress levels, that is, a change of stress level does not change the shape of the life distribution but changes only its scale. Second, a functional relationship is assumed between the parameters of the life distribution and the accelerating stresses. A nonparametric approach, on the other hand, assumes a functional relationship between the life distribution functions at the accelerated and nonaccelerated stress levels without making any assumptions on the forms of the distribution functions. In this paper, we treat the problem nonparametrically. In particular, we extend the methods of Shaked, Zimmer, and Ball [7] and Strelec and Viertl [8] and develop a nonparametric estimation procedure for a version of the generalized Arrhenius model with two stress variables assuming a linear acceleration function. We obtain consistent estimates as well as confidence intervals of the parameters of the life distribution under normal stress level and compare our nonparametric method with parametric methods assuming exponential, Weibull and lognormal life distributions using both real life and simulated data. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 629–644, 1998     

Statistical analysis of exponential lifetimes under an adaptive Type‐II progressive censoring scheme

In this article, a mixture of Type‐I censoring and Type‐II progressive censoring schemes, called an adaptive Type‐II progressive censoring scheme, is introduced for life testing or reliability experiments. For this censoring scheme, the effective sample size m is fixed in advance, and the progressive censoring scheme is provided but the number of items progressively removed from the experiment upon failure may change during the experiment. If the experimental time exceeds a prefixed time T but the number of observed failures does not reach m, we terminate the experiment as soon as possible by adjusting the number of items progressively removed from the experiment upon failure. Computational formulae for the expected total test time are provided. Point and interval estimation of the failure rate for exponentially distributed failure times are discussed for this censoring scheme. The various methods are compared using Monte Carlo simulation. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009     

航空发动机叶片的内窥涡流集成化原位检测

目前内窥检测是航空发动机叶片原位检测的唯一方法,但是内窥检测对于叶片裂纹缺陷的检测效果不理想.为此,提出内窥涡流集成化检测技术,使这两种方法的优势互补,实现对航空发动机叶片的原位检测.研制了一种可用于航空发动机叶片原位检测的内窥涡流集成化检测探头,给出了航空发动机叶片的检测实例.检测结果表明:内窥涡流集成化检测技术的缺陷检测能力高,并且可以实现对裂纹缺陷的定量评估,因此较单一的内窥检测更有优越性.具有很高的实际应用价值.     

火控系统动态精度环绕测试设计方法

借鉴环绕BIT技术的思想,提出一种火控系统动态精度环绕测试的设计方法.该方法充分利用火控计算机的固有资源,通过增加少量接口转换电路(一组现在点坐标输出接口和一组射击诸元输入接口),来提高火控系统动态精度检查测试性水平.对于采用环绕测试设计的火控系统,只需使用两根外接电缆,无须外接检测计算机,即可完成动态精度检查的任务,从而显著降低了操作复杂性.该设计方法的一个优点是不会影响系统的可靠性.     

蓄电池在线检测方法研究

在对阀控铅酸蓄电池的性能指标、失效机理、检测方法研究的基础上,通过比较各种检测方法,提出了一种新的蓄电池内阻在线检测方法——四线两端法,阐述了四线两端法的测试原理,给出了该方法在蓄电池在线检测中的检测步骤,同时分析了影响测量精度的主要因素,提出了提高测量精度所采取的措施,并给出系统测量误差。     

表面类裂纹缺陷与地磁场相对空间位置对漏磁场检测的影响

采用低频电磁场的有限元单元分析方法,分析铁磁性金属零件表面类裂纹缺陷与地磁场的空间相对位置变化对缺陷处漏磁场的影响,并通过试验进行了验证。结果表明：相对空间位置对漏磁场强度值影响较大,但对漏磁场强度曲线的变化特征影响不大。当缺陷与地磁场磁力线相互垂直时,漏磁场强度值最大;当缺陷与地磁场磁力线平行时,漏磁场强度值最小。这表明当采用漏磁场检测方法进行无损探伤时,零件的空间方向可能会影响探伤结果。     

弹丸动平衡自动测试方法研究

采用 IBM- PC机为主机 ,对弹丸动不平衡量 (m1 ,m2 )及相位角α进行自动测试并做相应的数据处理。设计了弹丸左、右两标定面的平面分离电路、A/D转换电路等。     

面向构件的测试研究

主要阐述了对构件测试的一种观点 ,并通过对系统测试及集成测试的裁剪 ,给出了对构件的一种测试方法     

钢弦测功仪的智能化改造研究与实现

将过去传统的钢弦式测功仪用计算机技术进行数据采集与处理 ,从而提高了其测量速度及测试精度 ,数据更为准确、稳定 ,可在 1台仪器上同时连续高速动态显示被测主轴的转速、功率、扭矩 ,并自动保存数据 .人机界面强 ,智能化程度高 ,具有很强的数据后处理及文件形成功能 .     

测试系统静电干扰的仿真实验研究

由于静电干扰的随机性和测试手段的限制 ,难以定量计算静电对测试系统的影响程度。基于人体静电模型和器件模型 ,导出用起电率表示的静电干扰对测试系统影响的仿真计算式 ,并计算出了一般静电环境下静电干扰的具体值 ,为测试系统的干扰计算和静电防护提供了依据