All posts by Oleg Ivanov

About Oleg Ivanov

I am an aircraft engine design engineer with experience creating accelerated tests of aviation products (auxiliary power units, turbo generators, turbo pumps, electro pumps). I see the shortcomings of standards and theory reliability/lifetime tests. My passion is to create new approaches (methods, tools) to accelerated tests. Life Cycle Simulator is one of these new tools.

Lifetime Evaluation vs Measurement Part 3

14782008631_1af1c79419_oLifetime Evaluation vs. Measurement. Part 3.

Sometimes shifting your perspective
is more powerful than being smart.

—Astro Teller

Guest post by Oleg Ivanov

A common approach for “no failure” testing is the use of the well-known expression

\displaystyle (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: Continue reading Lifetime Evaluation vs Measurement Part 3

Lifetime Evaluation vs. Measurement. Part 2.

Lifetime Evaluation vs. Measurement. Part 2.

Guest post by Oleg Ivanov

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). Continue reading Lifetime Evaluation vs. Measurement. Part 2.

Lifetime Evaluation v Measurement

14762203536_122d644c93_zLifetime: Evaluation vs. Measurement

Guest Post by Oleg Ivanov

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. Continue reading Lifetime Evaluation v Measurement