A Comparative Study Of Weibull Conditional Probability Density Distribution Surface And Normal Conditional Probability Density Distribution Surface

Fatigue is a common problem in engineering machinery and other industrialfields. Almost all engineering machinery are facing the feasibility of fatigue damage.Fatigue phenomenons often lead to sudden disaster which would cause great harm, sothe reseaches of fatigue have great significance to enterprise economy and personalsafety protecting.The traditional fatigue tests include grouping test and staircase test. Through theexperiments, we can get the S-N curve and fatigue limit, so as to understand thefatigue properties of materials. However, staircase test is actually a kind of testmethods under the situation of given fatigue strength. The determination of the fatiguelimit limited by fatigue life.It also has long experimental time and high cost.Therefore, how can access to material fatigue properties through a more accurate andefficient method has become a new direction of fatigue research.Based on the above background, a Weibull CPDDS (Conditional probabilitydensity distribution surface) has been built based on the CPDDS theory in this paper.This paper has introduced the the method of acquiring S-N curve and fatigue limitfrom a Weibull CPDDS. At last, the Normal CPDDS and Weibull CPDDS has beencompared and analysised.Weibull CPDDS mathematical model is constructed by the functionalralationaship between average fatigue life and stress as well as the functionalralationaship between fatigue life standard deviation and stress. The functionalralationaship between average fatigue life and stress has used power function fittingformular which proposed by Basquin. The functional ralationaship between fatiguelife standard deviation and stress has used reciprocal fitting formular. Then a WeibullCPDDS mathematical model can be acquired by pluging the two functionalralationaships into Weibull distribution probability density function.The comparison of Weibull CPDDS and Normal CPDDS is mainly include thecomparison of S-N curve and fatigue limit which acquired from the two CPDDS.Though the comparison we could observed that the S-N curve and fatigue limit whichacquired from the Weibull CPDDS and Normal CPDDS are consistent, and they arealso consistent to the S-N curve and fatigue limit which acquired from the standardtest.The concept and method of building Weibull CPDDS is a new method to reserchthe fatigue. It will provide a new method and theoretical basis for fatigue reserches in the future.