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   LOW CYCLE FATIGUE MODEL

Table of Contents

  1. Description

  2. Limit State Function

  3. Random Variables

  4. Analysis

  5. Results

Description:

The low-cycle-fatigue (LCF) life may be computed using the following equation. In this equation, N is LCF life, s is the stress in the part (in ksi) and e is the model error.

 

Limit-State Function: 

( 1)

Random Variables:

X1 = stress     = s

X2 = modelerr = e

 Case 1:      s  ~ Normal (m=95, s=5), e ~ Normal(m=0, stand. dev.=0.3)

Case 2:      s  ~ Uniform (XL = 80, XU = 110), e ~ Normal(m=0, stand. dev.=0.3)

Case 3:      s  ~ Weibull (m =95, s =5, XL=0.), e ~ Normal(m=0, stand. dev.=0.3)

 Analysis:

Anal1:  Perform Inverse Probability Analysis to identify the level of limit-state function defined in Eq. 1 corresponding to  Pf = .001.

Case 1:   s  ~ Normal (m=95, s=5), e ~ Normal(m=0, stand. dev.=0.3)

Case 2:   s  ~ Uniform (XL = 80, XU = 110), e ~ Normal(m=0, stand. dev.=0.3)

Case 3:   s  ~ Weibull (m =95, s =5, XL=0.), e ~ Normal(m=0, stand. dev.=0.3)

Anal2:   Perform Probability Analysis for N (x)£ N (x*), where x* is the MPP obtained from Anal1 to verify the results of Anal1.

Case 1:   s  ~ Normal (m=95, s=5), e ~ Normal(m=0, stand. dev.=0.3)

Case 2:   s  ~ Uniform (XL = 80, XU = 110), e ~ Normal(m=0, stand. dev.=0.3)

Case 3:   s  ~ Weibull (m =95, s =5, XL=0.), e ~ Normal(m=0, stand. dev.=0.3) 

Anal3:  Compute the CDF of the limit-state function defined in Eq. 1 for Pf = 0.000001 ~ 0.999999 using different input methods.

Case 1:   s  ~ Normal (m=95, s=5), e ~ Normal(m=0, stand. dev.=0.3)

Case 2:   s  ~ Uniform (XL = 80, XU = 110), e ~ Normal(m=0, stand. dev.=0.3)

Case 3:   s  ~ Weibull (m =95, s =5, XL=0.), e ~ Normal(m=0, stand. dev.=0.3) 

Anal4:  Plot N as a function of b.

 

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Last Updated 02/08/10

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