Your Reliability Engineering Professional Development Site
A listing in reverse chronological order of articles by:
Ideally, in every design of every component, the stress–strength relationship looks like this figure. The stress is well below the strength.
This implies there is very little chance of failure due to the element being overstressed.
Also, ideally, we fully characterize all stresses and all strengths for each element of a product. This is generally difficult to accomplish and it is rarely done to that extent.
Every once in a while I see a comment that by following the HALT methodology you will “over design” a product.
Many question at what point or operational limit do you quit increasing the stress-strength margins. Those who hold this view of HALT do not understand the essence of what was Gregg Hobbs’ principles and paradigm shift. [Read more…]
Reliability or life testing involves estimating the expected durability over time of an item.
This may be an entire system, a product, or an individual component. We may also focus on an element of a component, such has a material property.
At the end of the testing, we want to say something meaningful about the expected performance over time. [Read more…]
Highly Accelerated Life Testing (HALT) is a technique to expose weaknesses or faults with a product.
HALT uses individual or combined stresses in a step stress approach to quickly apply sufficient stress to reveal defects.
HALT is not a specific chamber or fixed set of test conditions. It is an exploratory process to reveal weaknesses in a design.
The product development process naturally includes a check step, to determine if the expected functions of the product work as expected.
Some teams then add a measured amount of stress (temperature, vibration, dust, load, etc.) to the product to explore functionality at elevated stress levels. [Read more…]
In short, you probably do, better reliability performance the better the brand image.
When I’m making a purchase I prefer to buy items that I either have personal experience work well over time (reliable) or have many comments and reviews noting the durability.
As a reliability engineer, I am often asked what kind of car I drive (a Toyota Highlander, if must know). Reliability does matter -not only to me- it matters for many making a buying decision.
When a product’s actual reliability performance exceeds the customers expected reliability performance, the customer may consider the product reliable. This experience builds and when supported by other experiences from the same brand, increases brand equity. High brand equity permits a price premium, increased brand loyalty, and increased positive word of mouth support. [Read more…]
Why do so many avoid failure?
In product development of plant asset management, we are surrounded by people that steadfastly do not want to know about or talk about failures.
Failure does happen. Let’s not ignore this simple fact. [Read more…]
Everything varies.
Your vendors provide components with a range of values. Your production process varies, too.
Creating, monitoring, and maintaining process stability enhances your product reliability performance.
When I started my professional life as a manufacturing engineer, a senior engineer told me we take a product design and can only make it worse.
He said if we could make every unit exactly according to the nominal values of the drawing, every unit would work well. [Read more…]
The trite answer is just as many samples as you need and not one more.
A better answer is enough samples to make the right decision. The realistic answer is you will not enough samples.
“How many samples?” is an oft-asked question when planning for quality or reliability testing. [Read more…]
A break from the normal format.
Reliability.fm is a podcast network focused on reliability engineering topics.
Starting with three shows. Speaking of Reliability and Dare to Know described below, along with recorded Accendo Reliability webinars. [Read more…]
Failures happen. Sometimes product failures happen quickly.
You just bought a new feature rich computer and discover it doesn’t work. Right out of the box, it will not power up. Conversations with the tech support and it’s a trip back to the store.
The failures that occur early the in the life of a product tend —
this ‘tend’ really is just a vague ‘in general’
…tend to occur because of manufacturing errors or shipping/installation damage.
Not always, though. [Read more…]
Your customers are your best testers for your next product. They will explore the features. Expose the product to use conditions in unconscious ways. And, they will let you what they consider failures without needing the specification document.
During the development process, you and team may work to understand what customer may want or expect for the new product. You may even conduct focus groups or review past product field failures and call center records. [Read more…]
Mechanical systems wear out and fail eventually. The ability of a structure to support a load, move through the specified range of motion, or spin degrades with use and time. Even our joints eventually wear out.
Accelerated life testing (ALT) has plenty of literature concerning the failure mechanisms unique to electronic components and materials. This is partially due to the limited number of unique electronic components compared to the often custom mechanical designs. ALT also has value as it provides information about a system’s reliability performance in the future.
Let’s explore an example of mechanical reliability testing (an ALT) in order to outline a basic approach to ALT design and analysis. [Read more…]
Suppliers often include reliability information along with performance specifications.
We look for reliability statements as one part of the selection process to ascertain if the component is likely to have sufficient reliability.
When the vendor’s data is clearly stated and meaningful, that information saves us from potentially having to conduct our own reliability evaluations. [Read more…]
If you buy more than one of an item used in your product, you will have to deal with variability. In general, the variability from part to part is minimal and expected. Occasionally, the variability is large and causes reliability problems. [Read more…]
It was late Friday afternoon and the phone rang. Which is rarely a good thing.
There seems to a significant spike in field failures due to one component. The initial failure analysis work reveals the issue started with a batch of parts received about two months ago and the flaw continues to appear in subsequent batches. [Read more…]
