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Tham khảo tài liệu 'assessing product reliability_5', kỹ thuật - công nghệ, điện - điện tử phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 8.I.6.5. Gamma Note that the value of gamma can be estimated using a PPCC plot. EXCEL also has built-in functions to evaluate the gamma pdf and cdf. The syntax is GAMMADIST t a 1 b FALSE for the PDF GAMMADIST t a 1 b TRUE for the CDF http www.itl.nist.gov div898 handbook apr section1 apr165.htm 6 of 6 5 1 2006 10 41 46 AM 8.I.6.6. Fatigue life Birnbaum-Saunders ENGINEERING STATISTICS HANDBOOK HOME TOOLS Ệ AIDS IS-EAR-CH BACK N xf 8. Assessing Product Reliability 8.1. Introduction 8.1.6. What are the basic lifetime distribution models used for non-repairable populations 8.I.6.6. Fatigue life Birnbaum-Saunders A model based on cycles of stress causing degradation or crack growth In 1969 Birnbaum and Saunders described a life distribution model that could be derived from a physical fatigue process where crack growth causes failure. Since one of the best ways to choose a life distribution model is to derive it from a physical statistical argument that is consistent with the failure mechanism the Birnbaum-Saunders Fatigue Life Distribution is worth considering. Formulas and Plots for the Birnbaum-Saunders Model Derivation and Use of the Birnbaum-Saunders Model Dataplot Functions for the Birnbaum-Saunders Model Formulas and Plots for the Birnbaum-Saunders Model Formulas and shapes for the Fatigue Life model http www.itl.nist.gov div898 handbook apr section1 apr166.htm 1 of 6 5 1 2006 10 41 46 AM 8.I.6.6. Fatigue life Birnbaum-Saunders The PDF CDF mean and variance for the Birnbaum-Saunders Distribution are shown below. The parameters are a shape parameter p a scale parameter. These are the parameters used in Dataplot but there are other choices also common in the literature see the parameters used for the derivation of the model . PDF shapes for the model vary from highly skewed and long tailed small gamma values to nearly symmetric and short tailed as gamma increases. This is shown in the figure below. http www.itl.nist.gov div898 handbook apr section1 apr166.htm 2 of 6