Use of the Weibull Distribution in Analyzing Life Test Data from Vehicle Structural Components

1964 ◽  
Author(s):  
R. A. Lemense
Keyword(s):  
Weibull Distribution ◽  
Test Data ◽  
Structural Components ◽  
Life Test

Six Sigma quality evaluation of life test data based on Weibull distribution

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Niveditha A ◽  
Ravichandran Joghee
Keyword(s):  
Weibull Distribution ◽  
Test Data ◽  
Six Sigma ◽  
Performance Metrics ◽  
Normal Process ◽  
Life Test ◽  
Content Type ◽  
Life Tests ◽  
Two Parameter ◽  
Theoretical Procedure

PurposeWhile Six Sigma metrics have been studied by researchers in detail for normal distribution-based data, in this paper, we have attempted to study the Six Sigma metrics for two-parameter Weibull distribution that is useful in many life test data analyses.Design/methodology/approachIn the theory of Six Sigma, most of the processes are assumed normal and Six Sigma metrics are determined for such a process of interest. In reliability studies non-normal distributions are more appropriate for life tests. In this paper, a theoretical procedure is developed for determining Six Sigma metrics when the underlying process follows two-parameter Weibull distribution. Numerical evaluations are also considered to study the proposed method.FindingsIn this paper, by matching the probabilities under different normal process-based sigma quality levels (SQLs), we first determined the Six Sigma specification limits (Lower and Upper Six Sigma Limits- LSSL and USSL) for the two-parameter Weibull distribution by setting different values for the shape parameter and the scaling parameter. Then, the lower SQL (LSQL) and upper SQL (USQL) values are obtained for the Weibull distribution with centered and shifted cases. We presented numerical results for Six Sigma metrics of Weibull distribution with different parameter settings. We also simulated a set of 1,000 values from this Weibull distribution for both centered and shifted cases to evaluate the Six Sigma performance metrics. It is found that the SQLs under two-parameter Weibull distribution are slightly lesser than those when the process is assumed normal.Originality/valueThe theoretical approach proposed for determining Six Sigma metrics for Weibull distribution is new to the Six Sigma Quality practitioners who commonly deal with normal process or normal approximation to non-normal processes. The procedure developed here is, in fact, used to first determine LSSL and USSL followed by which LSQL and USQL are obtained. This in turn has helped to compute the Six Sigma metrics such as defects per million opportunities (DPMOs) and the parts that are extremely good per million opportunities (EGPMOs) under two-parameter Weibull distribution for lower-the-better (LTB) and higher-the-better (HTB) quality characteristics. We believe that this approach is quite new to the practitioners, and it is not only useful to the practitioners but will also serve to motivate the researchers to do more work in this field of research.

Rolling Fatigue Life and Reliability of Ball Screws

2007 ◽  
Author(s):  
Hirokazu Shimoda ◽  
Shigeo Shimizu ◽  
Katsuji Tosha ◽  
Yushi Otani
Keyword(s):  
Fatigue Life ◽  
Weibull Distribution ◽  
Test Data ◽  
Dynamic Load ◽  
Ball Screw ◽  
Test Machine ◽  
Load Rating ◽  
Life Test ◽  
Dynamic Load Rating ◽  
Fatigue Life Test

The experimental formula based on Lundberg-Palmgren theory has been used for the calculation of basic dynamic load rating of ball screws because its contact state resembles that of angular contact ball bearings. However, the compatibility between the theoretical and the actual rating life of ball screws has not been yet confirmed by life tests and probability theory. The inherent properties of ball screws are also not considered in this formula. In this paper, the authors deal with the development of ball screw life test machine and fatigue life test for ball screws with a total number of 31 test samples. Type and occurrence location of the initial failure of each sample are investigated. The fatigue life test data are analyzed with two and three parameters Weibull distribution functions. The basic dynamic load rating of the ball screws are also estimated from the life test data. The results are summarized as follows: (1) Initial failures are generated at the surface of the balls and the nut raceway as a spalling. (2) The life distribution of the test data fairy well fits three parameters Weibull distribution function. (3) Basic dynamic load rating, which is estimated by the life test, is approximately in agreement with that of manufacturer’s catalog.

scholarly journals Research on sampling schemes of Weibull distribution product life test

2021 ◽  
Vol 1043 (3) ◽  
pp. 032072
Author(s):  
Zhewen Li ◽  
Guixiang Shen ◽  
Yingzhi Zhang ◽  
Liming Mu ◽  
Jun Zheng
Keyword(s):  
Weibull Distribution ◽  
Life Test ◽  
Product Life ◽  
Sampling Schemes

scholarly journals Design and application of accelerated life test of grating ruler based on step stress loading

2021 ◽  
Vol 336 ◽  
pp. 02027
Author(s):  
Jili Wang ◽  
Qingyu Li ◽  
Xiaocui Zhu ◽  
Cheng Gao ◽  
Yi Li ◽  
...  
Keyword(s):  
Weibull Distribution ◽  
Test Method ◽  
Accelerated Life Test ◽  
Test Scheme ◽  
Life Test ◽  
Test Device ◽  
Typical Application ◽  
Accelerated Life ◽  
Life Model ◽  
Accelerated Life Model

Combined with the actual project, a grating ruler accelerated life test device is designed, which can simulate the actual loads, including temperature, humidity and speed stress. An accelerated life test scheme based on stepped stress loading is proposed, and 6 grating rulers are tested based on time-censored test method. An accelerated life model based on Weibull distribution used for evaluating the lifetime is established. Related experimental techniques also can be typical application cases for innovative practical teaching.

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