on Product Reliability

A listing in reverse chronological order of articles by:

Kirk Grey — Accelerated Reliability series

Les Warrington — Achieving the Benefits of Reliability series

Adam Bahret — Apex Ridge series

Michael Pfeifer — Metals Engineering and Product Reliability series

Fred Schenkelberg — Musings on Reliability and Maintenance series

Arthur Hart — Reliability Engineering Insights series

Chris Jackson — Reliability in Emerging Technology series

by Enrico Belmonte Leave a Comment

Bathtub Curve and Human Mortality

The bathtub curve is one of the most famous graphical representations in reliability. It shows the typical trend of failure rate over time (Figure 1). This curve can be divided into three parts corresponding to decreasing, constant and increasing failure rate.

High but decreasing failure rate in the first part of the curve (1) indicates products defective or prone to fail due to manufacturing or design issues. The middle section (2) is characterized by low and constant failure rate. Failures in this phase are caused by unpredictable external events like flatting tire or power surge causing electronic failures. The right-hand side of the bathtub curve (3) shows increasing failure rate. In this stage, failures occur due to wear-out damage mechanisms such as fatigue, creep, ageing, wear and corrosion.

[Read more…]

by Enrico Belmonte 6 Comments

Calculation of Reliability Using the Stress Strength Interference Model

The calculation of reliability consists of the comparison between stress and strength. If we consider stress and strength as deterministic quantities, failure occurs when the stress exceeds strength. In reality, stress and strength are stochastic variables (Figure 1a). If the two curves overlap (Figure 1b), failure may occur. Let us suppose that s and S are continuous random variables with probability density functions f(s) and f(S), respectively.

[Read more…]

by Christopher Jackson Leave a Comment

What does Apple’s lightning cable, John Deere and the Mafia have in common?

Apple new iPhones will be somewhat different to those of the past. They will now have a USB-C charging and data port, and not Apple’s lightning cables. Why? Because the European Union said so. And they said so because they are not happy with the number of different charging cables we all now need for our various devices. Having a single cable that can charge an iPhone, Samsung smartphone, and virtually every other small electronic consumer product makes sense. It means fewer cables, smaller carbon footprints, less electronic waste, and prices will come down as less and less products assume that they need to provide a charging cable in their packaging. I have at least 20 power cables in my office that have been provided with various electronic gadgetry over the years.

[Read more…]

by Christopher Jackson Leave a Comment

Find Me the Statistics that I Like to Believe the Most …

It looks like 2023 will be the hottest year on record. Along with all the cyclones, hurricanes, floods and bushfires we have already had. Those who study and take climate change seriously unanimously agree that man-made changes to the environment are causing the climate to change so fast that mother nature will struggle to keep up.

And for the minority (yes, it is a minority as has been confirmed by many surveys and studies across the world), their arguments against climate change go something like this …

It might not be because of us …

… so it’s definitely not because of us.

[Read more…]

by Christopher Jackson Leave a Comment

The (Smaller) Carbon Footprints of Reliability Engineering

Climate change is universally accepted. And when I say ‘universally,’ I mean that the only people who think it is not a thing are fringe elements of society who are predisposed to specific interpretations of religion or commercial greed that would be harmed by any attack on fossil fuels and the energy we derive from them.

The good thing about this is that organizations who are serious about being successful and profitable can’t do so by sharing the ideology of a small minority. More and more people (including younger humans who will be the decision makers of tomorrow) are demanding more and more from the organizations they buy services and products from – especially when it comes to environmental concerns.

So to be successful, you need to take this stuff seriously.

Improving Fatigue Resistance

Fatigue involves localized, permanent damage to metals exposed to cyclic stress. In a previous article I discussed the fatigue mechanism. This article covers factors that can be addressed to improve high-cycle fatigue life

Factors that influence fatigue life

Several design, material, and fabrication factors influence component and joint fatigue life, including the following: [Read more…]

by Fred Schenkelberg 1 Comment

First Steps with Data

Once word got out that I was taking graduate-level courses in statistics, I dreaded the knock on the door. Colleagues, some of which I knew and others from some far reach of the company, would ask if I could take a look at their data. I didn’t learn the necessary first steps with a stack of data in class.

I’ve lost count of the number of data sets I’ve reviewed and analyzed. I know there are important considerations and questions before creating the first plot. Let’s review the essential first steps you should take when presented with data.

[Read more…]

by Christopher Jackson Leave a Comment

Complex Processes Become your Product (not your Actual Product).

I was recently asked by a product design engineer why their organization struggles with reliability even though they have a very ‘robust’ design process that seemingly has lots of different ‘good’ reliability engineering activities embedded in it. And when I say ‘good’ reliability engineering activities, I mean activities that have (in the past) shown to have a really good impact on reliability.

When I looked at some of this engineer’s processes as summarized by a ‘process flow chart,’ the reason his organization struggled with making reliable products was quite obvious.

The process was so complex that it became the ‘product.’

[Read more…]

by Fred Schenkelberg 1 Comment

Product Reliability and Customer Service

After 30 minutes of being on hold, I wasn’t sure what to expect from customer service for a product reliability issue. The scratchy soundtrack didn’t foretell a great experience either.

Once connected to a company representative, we resolved the issue quickly and satisfactorily. Unfortunately, that was a pleasant surprise. All too often, the frequently repeated “Your call is important to us.” (an Amazon affiliate link) just isn’t true, in my experience.

Did you know that customer service can add significant value to an organization, especially when product reliability doesn’t meet customers’ expectations? Besides providing the team with valuable product reliability performance information for past products, the service team can improve customer loyalty.

Failure Mode and Mechanism

In a previous article I discussed the degradation of materials due to exposure to stressors (use conditions) and how to identify stressors. Cracks form and grow in axles and shafts due to cyclic stress, steel screws corrode when exposed to water, some plastics become brittle when exposed to sunlight, and coatings on surfaces can wear away. When too much degradation occurs, components and joints fail, leading to product failure.

Things to consider during design

If you’re someone who likes to design reliable products, you must think about the stressors and their effects. When designing a product, we must identify the following things [Read more…]

by Fred Schenkelberg 2 Comments

Writing and Accendo Reliability

While I’m not much of a New Year’s Resolution guy, I guess I’ve set a resolution. I need to restart writing weekly articles for Accendo Reliability.

The thing is, I struggle to write. Plenty of other interests and tasks keep me away from the keyboard. Yet, as I explained to a few new authors how writing and posting on Accendo Reliability is a good thing, I realized I have been putting off hitting the keyboard again.

Over the past few weeks, I’ve explained to those interested in writing articles about the virtuous circle created by having many authors contribute articles, which increases interest, engagement, and traffic to those articles, which further increases the reach of those articles. Of course, this is just one reason, and there are others, plus plenty of hurdles to overcome.

Fatigue

Fatigue is a common degradation and failure mechanism. It involves localized, permanent damage to metals exposed to cyclic stress. The stress can be uniaxial, bending, or torsional resulting from a variety of sources including an applied force, vibration, acceleration and deceleration, and differences in thermal expansion between mating components exposed to heating and cooling cycles. Localized means the damage is confined to a small portion of a component or joint.

[Read more…]

by John Kreucher Leave a Comment

ALT Design using Damage Bins

The Arrhenius Equation is widely used and accepted by reliability and validation engineers from many industries to develop accelerated life tests (ALT) for thermal aging environments.

The general form of the equation describes the reaction rate of a process as a function of temperature (K), the Boltzmann constant (8.617E-5 eV/K) and two empirical factors. It can be written as:

Why Stainless Steel is Corrosion Resistant

Stainless steel is known for its corrosion resistance in many environments, with different alloys having different levels of corrosion resistance. Also, stainless steels are available with a wide range of strengths. Understanding the reasons for the corrosion resistance is helpful for selecting alloys based on the required strength and environment to which the steel will be exposed.

Thinking small

Fatigue cracks that originate at inclusions. Stainless steel intergranular corrosion due to chromium carbide precipitates. Low steel toughness because martensite not tempered enough. Low aluminum strength because of excessive grain boundary precipitation. Orange peel due to large grains.

These are examples of how problems with a metal’s microstructure lead to reliability and performance problems. Of course, there are thousands of examples of microstructures that lead to good reliability and good performance.

One hurdle to understanding metallurgy is being able to think small – very small. Less than a millimeter. Less than a micron. And sometimes on the scale of atoms.

[Read more…]

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