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Common Slope Assumption Abstract Chris and Fred discuss a ‘common slope assumption’ … which is something that only those of you with reliability engineering experience will have heard about. This is all about what we called ‘accelerated life testing’ where we increase stresses to accelerate failure. And software that is used to model accelerated life testing. Keen to learn more? Listen to this podcast! Key Points Join Chris and Fred as they discuss a common term used in ‘accelerated life testing’ or ALT. This is where we increase the stress our system is exposed to in order to accelerate failure. Why do we do this? Well … if we can increase stresses to our system and replicate 10 years worth of use in two weeks worth of testing … then we save lots of time and money. But as we know, failure is a random process. And one way of characterizing the way things fail (at least statistically) is with what we call the ‘slope’ of those times to failure. Tires that wear out will usually have a similar ‘slope.’ Steel that corrodes will typically have a similar … but different slope. So what does this mean? Topics include: Failure mechanisms tend to have the same slope. It doesn’t matter if it is wear, diffusion, corrosion, fatigue … they all have similar ‘slopes.’ Wear has a ‘typical slope.’ Diffusion has a different ‘typical slope.’ Fatigue has yet another, ‘typical slope.’ So even if you speed up failure by increasing stress (like temperature), the slope that describes the shorter times to failure will be the same. Accelerated life testing must not change the mechanism. Otherwise, we can’t be sure that two weeks worth of testing equates to 10 years worth of use. If you (for example) increase the temperature, and your system melts, then there is nothing you learn about actual time to failure. But it can be a lot more subtle than this. Increasing the temperature can change the characteristics of materials. Some materials (like plastic) become softer, meaning that you may accelerate time to failure in an essentially uncontrolled way. So why do we have the ‘common slope assumption?’ This should be more of a rule. And not an assumption. The slopes of the times to failure for systems exposed to different stresses should be the same. If they are not … then you almost certainly have different mechanisms being created by the increased stress. Unfortunately, many software packages and reliability engineers (neither of which are good at critical thinking) simply assume this to be the case. Which often leads to disastrous conclusions! What can go wrong? You might drastically underestimate reliability, and go back to the drawing board and waste time and money in creating a more robust design for no reason. Alternately, you can drastically overestimate reliability and launch a product that will very quickly fail in the hands of your users and customers. Takeaway? Always CHECK assumptions. Including common slopes for accelerated times to failure. Enjoy an episode of Speaking of Reliability. Where you can join friends as they discuss reliability topics. Join us as we discuss topics ranging from design for reliability techniques to field data analysis approaches.   Notice: JavaScript is required for this content.    Ask a question or send along a comment. Please login to view and use the contact form. Download Audio RSS Show Notes   The post SOR 725 Common Slope Assumption appeared first on Accendo Reliability.

Key Characteristics Revisited Abstract Carl and Fred having a new conversation about the age-old topic of key characteristics, and how they are used to improve products and processes. Key Points Join Carl and Fred as they discuss what is meant by key characteristics, and the application of key characteristics in achieving high reliability. Topics include: Specific examples of product characteristics Which product or process characteristics are most important (key characteristics)? How to prioritize characteristics Key characteristics must be measurable, part of product requirements, impact safety or performance CTQ vs key characteristics Linkage between key product characteristics and key process characteristics Examples of using key characteristics in testing Examples of using key characteristics in process control plans Is everything the same importance? Use of FMEA severity and occurrence to aid in identifying key characteristics How to derive key characteristics from FMEA Enjoy an episode of Speaking of Reliability. Where you can join friends as they discuss reliability topics. Join us as we discuss topics ranging from design for reliability techniques to field data analysis approaches. Download Audio RSS Show Notes   The post SOR 724 Key Characteristics Revisited appeared first on Accendo Reliability.

Question Everything Abstract Carl and Fred discussing the value of questioning in the process of learning and personal growth. Students and instructors should question each other as part of learning, engineering teams should question each other as part of achieving consensus. Key Points Join Carl and Fred as they discuss the role of questions in every reliability activity. Topics include: Ask why you are doing this test or that test What is the mechanism of learning? Do you learn more by listening to a lecture or by interactive dialog? How to get your team or your students more involved by active questioning? The role of body language in making it safe to ask questions Other ideas to create an environment conducive for questions Stimulate discussion, by asking questions of every student in the room Don’t ask “any questions?” ask each student a specific question Set the expectation of questions Encourage students to ask each other questions “Question everything” requires environment where it is safe to ask Encourage curiosity Barrier to questioning is exaggerated sense of self-importance Plato: teacher uses “ignorant mindset” to compel student to explain things Don’t assume anything is correct = scientific method Ask if information being analyzed is falsifiable, as part of the verification of truth Concept of scientific method: search for validity of hypothesis by asking questions, listening, experimenting, verifying Enjoy an episode of Speaking of Reliability. Where you can join friends as they discuss reliability topics. Join us as we discuss topics ranging from design for reliability techniques to field data analysis approaches. Download Audio RSS Show Notes   The post SOR 723 Question Everything appeared first on Accendo Reliability.

Obsolescence and Reliability Abstract Kirk and Fred discussing the article Kirk wrote titled “Why the Drain in the Bathtub Curve Matters” (see link in notes) about how technological obsolescence, and not product failures are the cause that cause many products to be retired or replaced. Key Points Join Kirk and Fred as they discuss technological obsolescence with cell phones and some of the improvements that have been made, plus the fact that there a many more ways to communicate than the plain old telephone service and land lines. Topics include: Phone calls have been around for a long time, but now most of the time our voices are now sent Voice over Internet Protocol which has been a big technological improvement in cell and wi-fi voice call reliability. The increasingly rapid technological improvements have been made because of the rapid technological improvements in CAD, manufacturing, and the tools to create new designs. Fred relies on the independently telephone land line due to the frequent power failures, although that too may fail depending on the duration of environmental stress (i.e. Texas’s power failures due to sustained well below normal temperatures) Technological improvements, such as backup cameras in automobiles, are a significant safety improvement that motivates many to purchase a new car even if your current car works fine. Enjoy an episode of Speaking of Reliability. Where you can join friends as they discuss reliability topics. Join us as we discuss topics ranging from design for reliability techniques to field data analysis approaches. Download Audio RSS Show Notes Here is a link to the article referenced in this podcast “Why the Drain in the Bathtub Curve Matters” Please click on this link to access a relatively new analysis of traditional reliability prediction methods article from the US ARMY and CALCE titled  “Reliability Prediction – Continued Reliance on a Misleading Approach” For more information on the newest discovery testing methodology here is a link to the book “Next Generation HALT and HASS: Robust design of Electronics and Systems” written by Kirk Gray and John Paschkewitz. The post SOR 722 Obsolescence and Reliability appeared first on Accendo Reliability.

Reliability and Testing Abstract Kirk and Fred discussing how much of reliability engineering is devoted to testing and what other functions should a reliability engineer do. Key Points Join Kirk and Fred as they discuss what a reliability engineer should be doing before a prototypes or parts are available. Topics include: Reliability engineering traditionally focused on prediction of system failures based on historical and many times outdated models long before there are parts or prototypes to test, which has sometimes mislead reliability risks mitigation efforts (See “Reliability Prediction- Continued Reliance on a Misleading Approach” below in notes) . The NASA Perseverance rover on Mars, and its scout helicopter Ingenuity found a limit in line of sight communication, which is a test that found new limits to the design, but confirmed the helicopters fail=safe design. A new iteration of a product may not need as much testing if there is a significant reliability history from the field reliability data, which does not need to be rediscovered in a test. FMEA’s may uncover reliability risks issues that can be corrected before and without any test, but testing can and may be used to confirm the mitigation of the potential cause of failures. Enjoy an episode of Speaking of Reliability. Where you can join friends as they discuss reliability topics. Join us as we discuss topics ranging from design for reliability techniques to field data analysis approaches. Download Audio RSS Show Notes Please click on this link to access a relatively new analysis of traditional reliability prediction methods article from the US ARMY and CALCE titled  “Reliability Prediction – Continued Reliance on a Misleading Approach” For more information on the newest discovery testing methodology here is a link to the book “Next Generation HALT and HASS: Robust design of Electronics and Systems” written by Kirk Gray and John Paschkewitz. The post SOR 721 Reliability and Testing appeared first on Accendo Reliability.

Reliability and Bathtub Curve Abstract Carl and Fred discussing the origin and meaning of the reliability “bathtub” curve, and why it is not useful as a visual analogy. Key Points Join Carl and Fred as they discuss the elements that make up full-life failure distributions, and the consequences of making wrong assumptions. Topics include: What is the actual shape of the “bathtub” curve? Why don’t system failure distributions follow a “bathtub” curve? What are the different elements that make up the “bathtub” curve? Early field failures due to manufacturing defects, later field failures due to design deficiencies What about service-generated failures or initial customer dissatisfaction? Discussion of actual field failures over time for vehicles, showing a “check-mark” curve We are seeing “check-mark” or “V” curves, why? What do the presence of early failure mechanisms have to do with the type of curve that is seen in practice? Why are people attracted to assumption of constant failure rate? Is it wishful thinking? Listener quiz: reliability allocation of the metric “Defects Per Thousand Vehicles” How to include “out-of-box” failures Look at actual data rather than forcing to a math model that doesn’t fit What visual representation reflects the failure rate of your product? Enjoy an episode of Speaking of Reliability. Where you can join friends as they discuss reliability topics. Join us as we discuss topics ranging from design for reliability techniques to field data analysis approaches. Download Audio RSS Show Notes Checkmark curve The post SOR 720 Reliability and Bathtub Curve appeared first on Accendo Reliability.

FMEAs and HALT Abstract Kirk and Fred discuss the relationship between FMEA (Failure Mode Effects Analysis)  and HALT (Highly Accelerated Limit Test) Key Points Join Kirk and Fred as they discuss how informal or formal FMEAs help identify the potential weaknesses in a systems to apply accelerated stress testing. Topics include: FMEAs help to identify potential weak links to to HALT to determine how much stress margin there is before a failure (limit) occurs and the variation and distribution of limits sample to sample. The informal FMEA on a medical product identified a possible weak link that could be a safety hazard due to the single failure point, and it led to a redesign. FMEAs that may identify safety issues are the highest priority in evaluating the amount of stress margin using HALT. Enjoy an episode of Speaking of Reliability. Where you can join friends as they discuss reliability topics. Join us as we discuss topics ranging from design for reliability techniques to field data analysis approaches. Download Audio RSS Show Notes Please click on this link to access a relatively new analysis of traditional reliability prediction methods article from the US ARMY and CALCE titled  “Reliability Prediction – Continued Reliance on a Misleading Approach” For more information on the newest discovery testing methodology here is a link to the book “Next Generation HALT and HASS: Robust design of Electronics and Systems” written by Kirk Gray and John Paschkewitz. The post SOR 719 FMEAs and HALT appeared first on Accendo Reliability.

Dealing with HALT Fear Abstract Kirk and Fred discuss misunderstandings of the limit testing and believing it’s “just breaking it” Key Points Join Kirk and Fred as they discuss what happens when there is not a common understanding of the using of empirical stress limits early in the development of a new product. Topics include: Early prototypes and samples of a part may have some slightly different mechanical properties then the materials used in mass production, making testing with prototypes limited in understanding of the final product. The term “Failure” has a negative perception and a better term for finding the stress level of operational failure in a HALT (above design specifications) should be called a limit. When designing a new product, the design rules are based on physics of materials and mechanical loads. Design rules are the most fundamental application reliability by making sure the strength of the system exceeds the nominal or worst case end-use stress  conditions. Enjoy an episode of Speaking of Reliability. Where you can join friends as they discuss reliability topics. Join us as we discuss topics ranging from design for reliability techniques to field data analysis approaches. Download Audio RSS Show Notes Please click on this link to access a relatively new analysis of traditional reliability prediction methods article from the US ARMY and CALCE titled  “Reliability Prediction – Continued Reliance on a Misleading Approach” For more information on the newest discovery testing methodology here is a link to the book “Next Generation HALT and HASS: Robust design of Electronics and Systems” written by Kirk Gray and John Paschkewitz. The post SOR 718 Dealing with HALT Fear appeared first on Accendo Reliability.

Planning a Reliability Program Abstract Carl and Fred discussing the planning that goes into any reliability program. Key Points Join Carl and Fred as they discuss approaches to achieving high reliability. Specifically using the 6-step process. (See Show Notes) Topics include: The 6-step” process to achieve high reliability (See Show Notes) Does the 6-step process apply to setting up a reliability organization? What is a “reliability organization”? Vision for reliability in one, three and five years Aligning the tasks in a reliability program to year of implementation. Scope of reliability plan can be project or program Reliability plans can include organization-related tasks, as well as project-related tasks The 6-step process works for setting up a program, laboratory, consulting practice, and many other activities Stephen Covey: “begin with the end in mind” If you are setting up a reliability organization, consider aligning to an actual project in parallel “Reliability organization” does not mean a separate reliability team, it is an integration of reliability expertise with product and process engineering How to alter the culture of an organization Measuring things does not change reliability. Improving reliability involves changing mindsets and influencing the organization. Enjoy an episode of Speaking of Reliability. Where you can join friends as they discuss reliability topics. Join us as we discuss topics ranging from design for reliability techniques to field data analysis approaches. Download Audio Show Notes 6-Step process with deliverables Reliability Maturity Matrix Quick note: in this SOR episode, I mistakenly called Greg Hutchins, Greg Hutchinson (sorry, Greg). Greg is a thought-leader on  AccendoReliability. He is managing director and principal engineer at Critical Infrastructure Protection: Forensics, Assurance, Analytics (R), and heads up many exciting projects about the future of professions. I’ve enjoyed reading his book “Working It: Disruption Rules – COVID Edition.” Here is Greg’s About Page The post SOR 717 Planning a Reliability Program appeared first on Accendo Reliability.

Practical Way to Learn Statistics Abstract Chris and Fred discuss statistics! Yay! And how we can be better at using them in a practical way. And that starts with wanting to learn about statistics. But how do we make that happen? Key Points Join Chris and Fred as they discuss statistics and how we can better use them in a practical way. Statistics are often seen as a concept to avoid at all costs. Or pretend to know without really knowing. As they say … there are lies, damn lies and statistics. So what can we do to have statistics help us in a more meaningful way? Topics include: Make statistics relatable. Many ‘learning’ institutions start statistical education with a jar with a bunch of red/blue or black/white beads in it. And then proceed to talk about how statistics can apply to the number of beads you might randomly select. But who carries around jars full of beads? … and who makes important business decisions based on jars of beads? Why do this? A little more thinking can quickly identify real-world scenarios that mean something to students. And THAT is when we start to remember concepts. Don’t confuse ‘statistics experts’ with ‘statistics gatekeepers.’ Statistics gatekeepers are those annoying people in many organizations who enjoy having the power to stop anything as opposed to help people. That is, they sit in quality, reliability or design reviews and explain how everything has been done wrong, everything needs to be more complicated, and how everyone has (once again) failed to meet their lofty expectations regarding statistics. They know enough to be intimidating to those around them. But they don’t know enough to be helpful. So they add no value, keep having their egos challenged, and are otherwise avoided. So no one is happy. And it starts with teaching. Chris talked about a Statistical Process Control (SPC) course he is developing which is based on breadmaking. The statistic he was using as the central example was ‘chewability.’ This sounds like a ‘made up’ abstract metric that can’t really be applied in an objective way. But it can! In fact – there are really expensive test rigs that are able to measure the hardness and elasticity of bread that is analogous to what we would describe as ‘chewy.’ The point is … everyone knows or can relate to sliced bread. And the fact that ‘chewability’ is a novel metric (at least to students) makes it interesting. So people remember it. But because many statistics courses aren’t fun … they aren’t done. Many undergraduate engineers manage to get their degree without ever doing a statistics course. This is a damning indictment on learning institutions. Starting with universities that employ professors who aren’t interested in crafting a message that is more interesting than jars of beads. Which one of the many reasons Accendo Reliability’s statistics articles and courses are so popular … Enjoy an episode of Speaking of Reliability. Where you can join friends as they discuss reliability topics. Join us as we discuss topics ranging from design for reliability techniques to field data analysis approaches. Download Audio RSS Show Notes   The post SOR 716 Practical Way to Learn Statistics appeared first on Accendo Reliability.