#1 Re: Questions about Arbre-Analyste » Weibull VS Exponential Law » 2017-02-23 13:46:28

Emmanuel,

Thank you so much, I made a big mistake sorry:)

Can I have a suggestion?

Concerning Weibull law, If I would like to consider the fatigue phenomena I have to use beta>1. However, I am not sure which value I could apply to the scale parameter alpha. I know this relationship: MTTF= alpha Γ (1+1/beta).
Knowing that I have the MTTF of each base event are there any other way to get the parameter alpha? Or I have to use this formula: MTTF= alpha Γ (1+1/beta).

Ps: why if I always use for each base event an exponetial law the global plot does not follow the classic exponetial law trend and I do not obtain a costant lamda system during time ( lamda=1/MTTF).

Sorry for all these questions and thank you so much for your time and kindness

Best

Alessio

#2 Re: Questions about Arbre-Analyste » Weibull VS Exponential Law » 2017-02-23 11:16:28

Good morning Emmanuel,

Thank you for your answer. Unfortunately I tried again this morning but I can not obtain the same results.
I think that I am doing the same approach, using more gates and base events.
However, I am attaching my FTA...

test-law-exp-vs-weibull_imagesia-com_1d793_small.png
Hébergé par Imagesia.com

What do you think?

Moreover, I would like to understand why the plot does not follow the classic exponetial law trend and I do not obtain a costant lamda during time ( lamda=1/MMTF if I use the exponetial law).

I think that I am making some errors but I do not know where exactly.

Thank you for your time

Best

Alessio

#3 Questions about Arbre-Analyste » Weibull VS Exponential Law » 2017-02-22 15:03:40

AleDela
Replies: 5

Good afternoon,

First of all, thank you for your software and your service:)

I did a test:

- Using the exponetial law for all the base events
- Using the weibull law for all the base events applying Beta=1 and alpha=MTTF=1/lamda (case: Weibull= Exponetial)

But I do not get the same results (different F(t)). I performed a "calcul ponctuel".
Could you help me to understand where is my error.

Thank you for your time

Best

Alessio