Articles tagged Life estimation

Reliability Prediction using Monte Carlo Simulation

In the last video on stress-strength interference, we have seen the analytical method. This has limitations and often cannot be used in real life problems in reliability prediction. For example, velocity of windmill may have Weibull or lognormal distribution, elevators may have particular application load cycles which can only be modelled using empirical distributions. In such situations, we need to use Monte Carlo Simulation using various other distributions. I will discuss and explain this technique in this video.

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by Hemant Urdhwareshe Leave a Comment

Reliability Prediction using Stress Strength Interference (Analytical Method)

Often, products fail, and we don’t understand why! One of the reasons why such failures occur is not giving consideration for variation in load or stress levels. For example, potholes and speed breakers can create excessive stress on automobile suspensions; or larger number of clothes washed in a machine more often than the designer has considered; or a bus used in public transport would carry varying number of passengers! Designers often do not realize that the materials used in the product will also have variations! For example, wall thicknesses of castings will vary; or chemical composition of steel will vary from lot to lot! Thus, designers need to address the variations in usage patterns and variations in the materials used in the product as these can seriously affect reliability of systems! In my recently uploaded video, I have discussed how to predict reliability when load (stress) and strength of the part both vary and can be modelled using normal distribution. The video will also be very useful to those who wish to take ASQ Certified Reliability Engineer exam and all those who wish to learn the basics of reliability in design. This is the first video where the stress and strength can be modelled using normal distribution. In the next video related to this topic, I will explain reliability prediction using Monte Carlo Simulation.

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by Kirk Gray 2 Comments

Electronics Failure Prediction Methodology does not work

“When the number of factors coming into play in a phenomenological complex is too large, scientific method in most cases fails. One need only think of the weather, in which case the prediction even for a few days ahead is impossible.” ― Albert Einstein
“Prediction is very difficult, especially about the future.” – Niels Bohr* We have always had a quest to reduce future uncertainties and know what is going to happen to us, how long we will live, and what may impact our lives. Horoscopes, Tarot

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by Fred Schenkelberg Leave a Comment

When to Make a Reliability Prediction

The easy answer is very often. Each time you want to know how long a product will operate. The accompanying question on how well the estimate will match actual performance makes the real answer more difficult.

We regularly and intuitively do reliability predictions all the time. When starting a car at the beginning of a trip, we estimate the ability of the vehicle to complete the journey. When we purchase a phone, we expect it to operate for at least two years (your expectations may differ).

During the design process, we may have formal or informal useful life expectations. It is not knowing if our decisions related to the design will fulfill the lifetime expectations that leads to the desire to know how well the resulting system will operate. We also may need to estimate warranty or maintenance costs, thus knowing what is likely to fail becomes important.

In general, knowing how long something will operate without failure provides the feedback we need to create a viable system that meets our business and customer reliability expectations.

In short, we do reliability predictions regularly to gauge is we are making good decisions. [Read more…]

by Fred Schenkelberg 2 Comments

Reliability Testing Considerations

Reliability testing to determine what will fail or when will failures occur is expensive.

Organizations invest in the development of a product and attempt through the design process to create a product that is reliable. [Read more…]

by Fred Schenkelberg Leave a Comment

Consider Reliability Prediction Value

One of the primary questions we answer as reliability engineers is:

How long will it last?

Reliability prediction is the forecast or prognostication attempting to quantify either the time till failure, or expected future failure rate or warranty claims, or required spare parts.

We need to know as we make decisions today about the design or purchase.

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by Fred Schenkelberg 40 Comments

Reliability with Confidence

There are rare situations when we would like to estimate the reliability at the lower confidence level after estimating the mean from a sample (often a test result). And, to make even more rare of a situation, we know the population standard deviation. [Read more…]