How can we find the relation between life time and durability test in automotive part

[asghar.pu]

hello all,i want to find a relation between our tests(fatigue & durability test) on our product(aluminum wheel for passenger cars) and lifetime of it.i.e we test our wheels for 2000 km,so what's the lifetime of our products.i appreciate you helping me in advance.

 

[Stijloor]

Re: How can we find the relation between life time and durability test in automotive

Can someone help with this?

Thank you very much!

Stijloor.

 

[Marc]

Re: How can we find the relation between life time and durability test in automotive

Another quick "Bump" in case someone here can help. My Thanks in advance!

 

[Barbara B]

Re: How can we find the relation between life time and durability test in automotive

hello all,i want to find a relation between our tests(fatigue & durability test) on our product(aluminum wheel for passenger cars) and lifetime of it.i.e we test our wheels for 2000 km,so what's the lifetime of our products.i appreciate you helping me in advance.

To give an answer to your question a little bit more information is required:

• How many products did you test?
• How long did you test your products?
• Were there any failures in the test period? If so, when did they occur?

Reliability analysis is a probabilistic approach, so you could not determine what THE lifetime of a product is, but you could draw conclusions out of test results like "with 99% probability only 0.05% of our products will break down before 2000km".

Regards,

Barbara

 

[asghar.pu]

Re: How can we find the relation between life time and durability test in automotive

Thank you for your attention.there are enough tests and no failure until now.our acceptance criteria in durability test is 2000 km that all test done is OK.now i want to estimate the lifetime of our product ( how many years can i guarantee our product? 5 ,10 years or more).what is necessary here is to find a relation between acceptance criteria in durability test and lifetime of product.

 

[Barbara B]

Re: How can we find the relation between life time and durability test in automotive

Without failures it is difficult to calculate the chance of a failure (or the survival probability / reliability). At the point 2000km (test period) + 1 km all products could fail, but they could also survive for another 100.000km.

What number of km do you expect for your product after 5 years or 10 years?

Even if you test "enough" products you won't have enough information about the failures to guarantee the survival for a much longer operating time than your test period is, e.g. for a test period of 2000km, 0 failures in test assuming a Weibull distribution with shape 1.0 and 95% confidence level you have to test really much products to assess a reliability of 99.99%:

99.99% reliability at time t -> required sample size n
t=100km -> n=1498
t=500km -> n=7489
t=2000km -> n=29956
t=5000km -> n=74890
t=20000km -> n=299558
t=100000km -> n=1497791


So without specific requirements and numbers you can't calculate the reliability of your products.

Regards,

Barbara

 

[asghar.pu]

Re: How can we find the relation between life time and durability test in automotive

hello,thank you very much for your good information,our requirement for this test is 160000 km.we have a limit for number of test that each test takes about 2 days.so we can't test very much.you mentioned for 100000 km n =1497791 my question is 'what is n?'does it refer to the number of product should be tested? if yes so we can't do all of them.
another question ,why do you use Weibull distribution for estimation?can we use another distribution that needs fewer tests?

Best regards
asghar

 

[zancky]

Re: How can we find the relation between life time and durability test in automotive

I'm not an expert but once I was in automotive sector.
In the past the life time of a vehicle was
150.000 km 10 years 4000h operating

the relation between durability test and real life was normally based as a first approximation on woehler curve for the material and the loads expected during the life.

nevertheless SAE (see www.sae.org) has established standard and published papers etc about wheel test

 

[marchino]

Re: How can we find the relation between life time and durability test in automotive

Hello
I'm Marco and I work in the Automotive too.
I have a similar kind of question : we are developing an electronic device (it is basically a metallic box with 3 PCB inside).
The requirements from car manufacturer are : 15years,300.000km,70.000h in stanby mode.
Actually I think I should plan a reliability test plan , looking for the key points to be evaluated.
But after that , what can I do to know if my product will work again after 15yers and 300.000km and 70.000h ?
I can't test many pieces (they are not small and not chep) and I can't test for too much time , just few months.
Am I supposed to perform some ALT test and to use a simulation to estimate the failure rate at 300.000km and 15y ? how can I do it?
I have also an other date : the car manufacturer allows 0.13cases/100 veichles in the firts 24 months.

Does anyone know what I have to do ?

thank you