Your Reliability Engineering Professional Development Site
We are well aware of cases when Accelerated Testing is successfully creating by statisticians, here I would like to propose an engineer’s approach.
We have created a new product, there is (is) an order for it (50 products at a price of $200). Can we start manufacturing and delivery? No, we can’t. We are stopped by significant warranty obligations and lack of confidence in the reliability of the product during the warranty period.
This is a typical task with uncertainty.
[Read more…]
Give me a place to stand on, and I will move the Earth.
Archimedes
Its known HALT is an effective way to find the weaknesses in your product during the reliability improvement program. In doing so, we view HALT as a qualitative test only. We cannot define the reliability and lifetime of the product from its results. So, unfortunately, we cannot use HALT for purposes of Type Certification, confirm the lifetime of Critical Parts, predict the warranty and maintenance costs, which are required, for example, for aviation.
If we could combine the effectiveness of HALT (high acceleration of testing) with the benefits of quantitative testing, we would get a very powerful tool for the Reliability Demonstration and the Reliability Development of the new products.
Sometimes shifting your perspective
is more powerful than being smart.—Astro Teller
A common approach for “no failure” testing is the use of the well-known expression
$$ (1) \quad 1-CL={{R}^{n}}$$
where CL is a confidence level, R is a required reliability, n is a sample size. Its parent is a Binomial distribution with zero failures. This expression is like a poor girl: [Read more…]
A result of life testing can be measurement or evaluation of the lifetime.
Measurement of the lifetime requires a lot of testing to failure. The results provide us with the life (time-to-failure) distribution of the product itself. It is long and expensive.
Evaluation of the lifetime does not require as many test samples and these tests can be without failures. It is faster and cheaper [1]. A drawback of the evaluation is that it does not give us the lifetime distribution. The evaluation checks the lower bound of reliability only, and interpretation of the results depends on the method of evaluation (the number of samples, test conditions, and the test time). [Read more…]
How can we tell whether an iron is hot enough? The answer is obvious: We can measure temperature by using a thermocouple and a meter. But, in practice, we lick our finger and touch the iron. Sizzle…. Yes, it’s hot!
We know a priori the boiling temperature of water and we can evaluate the temperature of the iron. This method has a lower cost. [Read more…]
Thems that die’ll be the lucky ones.
~ Robert Louis Stevenson
This post is a continuation of the series “Is the HALT a Life Test or not?”
Test two samples and demonstrate reliability R=0,99 over a lifetime with CL=0,99. This is real. But what payment will we pay, besides the duration of the test on triple lifetime, which can be significantly accelerated by the way? [Read more…]
Meaning of Identifiers
K&R
HALT (Highly Accelerated Life Test). There is an opinion that “its name doesn’t do it justice”.
In the first Part “Is the HALT a Life Test or not?” we added the test time to the HALT stress set. We see there is the Life in HALT.
In Part 2 we added knowledge of the lifetime distribution type and a shape parameter (variation). We were able to evaluate the reliability during the warranty time with a given CL by “pulling the lifetime distribution by the tail”. We see HALT may be a quantitative Test. [Read more…]
In the first part “Is the HALT a Life Test or not?” we added the test time to the HALT stress set. What does this give us for lifetime evaluation when testing one or two samples? The correct answer is nothing. But if we add knowledge of the lifetime distribution type and a shape parameter (variation), then we can work with its tails [Read more…]
Astro Teller
It is generally known that HALT testing means destroying a product with stepped stresses. Most experts agree that HALT doesn’t’ provide much information about life and the acronym of HALT (Highly Accelerated Life Test) is wrong. [Read more…]
