Design | Endurica LLC

4-in-1

December 30, 2024December 15, 2024 by Tom Ebbott, Ph.D.

Wow – this year has really been one of many firsts for Endurica. We had our first ever Community Conference in April, we started our first sister company – in Europe, and from September 9 – 13, 2024, we presented 4 technical papers – a new Endurica record for one week! The other impressive aspect of this latter feat was that the four presentations were on vastly different topics! I’ll just list the venues and titles and then discuss each one.

International Elastomer Conference 2024, Pittsburgh, PA, USA:

“Heat Build-Up and Thermal Runaway in a Rotating Bending Experiment”

44^th Annual Meeting and Conference of The Tire Society, Akron OH, USA:

“Coupled Multiphysics Strategy to Monitor the Health of Rubbery Structures Using Endurica Tools”
“Critical Plane Analysis of Surface-proximal Fields for the Simulation of Mechanochemical Wear”
“Models, Materials and the Move Towards Virtual Product Development”

Let’s start with the first presentation on heat build-up. Will Mars presented this paper at the IEC in Pittsburgh on Tuesday the 10^th of September. The presentation highlighted a new machine that has been developed by Coesfeld to evaluate the heat build-up behavior of rubber compounds. It uses a hollow rubber tube that is bent to a 60-90 degree arc and then rotated at about 600 rpm to create a tension-compression cycle throughout the tube due to the pre-bending as shown below.

This test offers many advantages over the historical Goodrich Flexometer self-heating test originally developed in 1937. The Heat Build-Up Analyzer is instrumented to measure internal temperature as well as forces and deformations while the test is progressing. The recent advances in the Endurica software and workflows are also equipped to predict the transient behavior in this test. When the rubber reaches a certain high temperature, the rubber starts to break down, often due to the volatilization of low molecular weight additives creating an exothermic reaction, and also due to the reversion of the cross-links. The exothermic reaction and thermal “runaway” condition can also be predicted by Endurica software. The animation below shows the elevated temperatures and the internal pressure rise due to the exothermic reactions. The combination of the HBA test and the Endurica FEA-based analysis will add understanding to the heat-rise behavior of compounds for any company. As with some other Coesfeld machines, Endurica is the sole distributor in the Americas.

The second presentation listed was presented by Mahmoud Assaad, co-authored by others at Endurica and also by Ed Terrill at ARDL. This work aims to provide the combination of a full oxygen diffusion and oxidation reaction simulation and experimental characterization capability. The plot here shows the distribution of reacted oxygen in the crown area of a commercial truck tire. As the oxygen diffuses into the carcass it also reacts with the rubber compounds creating a phenomenon known as Diffusion Limited Oxidation. Mahmoud, Ed Terrill and I worked on rubber oxidation with Sandia National Laboratories when the three of us worked together at Goodyear. Now we have developed a characterization and simulation capability that should be ready for customers to try in 2025!

For the third presentation listed, Will Mars quickly travelled from the IEC in Pittsburgh to the Tire Society in Akron to give a talk on an evolving capability for wear prediction. This work was co-authored by Lewis Tunnicliff and James Kollar at Birla Carbon as well as others from Endurica. For many years, researchers have been trying to link rubber fracture and tearing behavior to surface wear. One of the early works on this topic is shown in the drawing below from Southern and Thomas in 1979.

This work attempted to explain observations from blade abrader experiments. The Endurica/Birla work broadens this concept to different asperity shapes and a cumulative fatigue process that depends on the depth into the surface. Temperature distribution near the surface was also calculated and included in the analysis. Initial results gave similar trends for wear rates as work done by Gent and Pulford in 1983. This new approach also makes it easy to also incorporate any aging effects that may occur on the surface of a rubber product. Development work on this new capability will continue well into 2025. In the meantime, Endurica does have a more basic FEA-based offering for wear prediction that has been used for multiple customers.

Lastly, on Friday the 13^th of September, I had the honor of giving the Plenary Lecture for the Tire Society conference. Thanks go to Jim McIntyre and the conference organizers for giving me this unique opportunity to address the society.

In April, we conducted the first ever Endurica Community Conference, and we tied in the Solar Eclipse that passed over Findlay, Ohio on April 8th, to produce a very successful event. I wanted to include the solar eclipse in my Plenary talk and somehow relate it to topics concerning the development of tires. The two concepts I used to make the connection were:

All models are approximations, but some can be very useful, and
Some very good physics theories predict singularities. The singularities reveal our ignorance on the topic and show the area where further work and insights are needed.

The first concept comes from the late George E. P. Box, a statistics professor at the University of Wisconsin. The quote is usually stated as: “All models are wrong, but some are useful”. The second concept makes a tie between fracture mechanics and Einstein’s General Theory of Relativity, which was validated by data taken during a solar eclipse in 1919. Both of these theories predict non-physical singularities but remain extremely useful.

The bulk of my talk was on Virtual Tire Development using tire durability as one of the performances to evaluate without building and testing prototypes. It largely followed my experience and contributions to the topic over the 3+ decades I worked on this at Goodyear with many excellent colleagues and partner organizations like Sandia.

All four of these presentations are available on our website at this location: Fatigue Ninja Frontier – Resources from Endurica’s First Annual Meeting.

Please contact us if you have any questions about these presentations or if you would like to chat with us about anything, including possible work together.

One final note: we are working on a revised website. Our Marketing Director, Pauline Glaza, is heading up a project to develop a new website for us that should make navigating our material and interacting with us much easier. Expect to see our new site in early 2025!

What is the Price of Standing Still?

February 15, 2023February 15, 2023 by Pauline Glaza

What if we don't change at all and something magical just happens? Technical equation for entropy

“We have always done it this way.” No longer simply a hated phrase, this statement is a warning of impending disaster. Entropy – the disorder that happens when energy disperses and systems simply fall into chaos – happens when things do not change. But it’s a slow process you don’t see day-to-day. Continuing with traditional “build and break” development methods instead of embracing CAE and simulation has many long-term risks but it will only be after stagnating for some time that rubber parts manufacturing firms, and even the entire rubber industry, will realize the pitfalls:

Talent Loss
People are the key to it all and we start here since intelligent, hard-working, productive people are the fundamental reason any business succeeds. When the best and brightest employees leave a company, the fundamental reasons often include the lack of opportunity, learning, and career development. When not allowed to work with emerging technologies and are no longer challenged to grow, top performers find new opportunities taking not only raw potential but also institutional memory with them. And if they don’t see the industry as a viable long-term option, switching companies can also mean leaving the sector completely.

Warranty Issues/Payouts
Liability issues arise when product usage, applications and environments bring risks that may not have been factored in to the original designs and/or production methods. Traditional testing methods cannot be used to investigate “what if?” scenarios the way CAE and simulation can. Recalls and litigation can be significantly more costly than new technology implementations.

Lost Opportunity Costs
While harder to measure than fixed and variable business costs, there is an expense to every choice known as opportunity cost. Refusing to enter a new business sector may result in significant loss of revenue and profit. Taking on a big client project may strain production capabilities. “Standing still” eliminates those risks, but at what potential gain? As the rubber industry wrestles to “go green” we are all weighing and measuring the opportunity costs involved. The real lost opportunity is in refusing to embrace a fundamentally better design platform.

Incompatibility or Obsolescence
At some point, everything being produced right now will become obsolete. Even if you produce the best “widgets” anywhere, the environment around that “widget” will change and will no longer be needed in its current form. The rubber industry standard procedure of building a product then breaking it in physical testing to determine the next design rendition is incompatible with the time available for new product development. It just does not work anymore.

How quickly your business can adapt to or anticipate change is a key factor in continued success. The reasons companies do not make continued progress often include:

Change is expensive
Investments in training, new production systems, updated software and computers add up, but these numbers are not insurmountable when factored against the ongoing and often increasing costs of waste, repairs and downtime associated with outdated systems and equipment.

Learning new technology is time-consuming
Remember when you were thinking about going to college and four (6-8-10) years seemed like FOREVER? What was your ROI? What will it be now? Time invested in learning reaps many rewards beyond the subject at hand and often provides renewed overall energy.

The status quo works
For today, yes. For a brighter future for you company and the industry, NO. Companies that don’t evolve face certain death. Day-to-day operations may appear stable, but firms who do not keep up with technology do not stay in business. Covid forced many to embrace technology in new ways and those firms continuing to provide progressive working arrangements are gathering more than their fair share of the best and brightest talent. Enabling people to work beyond traditional geographic boundaries requires accountability and processes for measuring valued contributions rather than simply time at a desk. Firms embracing CAE and simulation technologies have realized this and are at the top of the leading rubber industry rankings.

Six reasons to adopt Endurica workflows

Technically superior (click for details)
Save big on development out of pocket costs (click for details)
Reduce the need for physical testing (see page 2, blue box on right)
Speed to market (able to use the tools immediately)
Accuracy in meeting client needs (click for details)
Easier answers down the road (click for details)

The 5-50-500 Rule

December 12, 2022December 7, 2022 by Pauline Glaza

2 Minute Read | 400 Words

I ran a marketing consulting business for 30 years before joining Endurica and tried to save clients from learning the hard way. When brochures were the only way to convey a company’s message (pre-internet), it was critical that people understood the $5, $50, $500 rule.

$5 = cost for changes during the earliest design phase. This is the point where everything is on the table as you develop the look, feel, message, and content of the brochure.
$50 = cost to make changes at the first mock-up of the brochure. No big deal. At this stage, changes take a bit of work and may impact multiple pages or sections – but it’s a LOT better to make changes now than later and I encouraged people to speak up about anything/everything because change was still pretty easy. Approval at this stage sends us into production.
$500 = cost to make changes after we sent the brochure to the printer. That’s the cost to change even one LETTER, let alone a photo or – heaven forbid – an entire page. It was at this point that one client said “ok, now I’ll read it” and I had to stop myself from throwing a file at him.

All of this came up as we talked about the value of our software in rubber product development. The concept’s the same but the numbers are SO MUCH BIGGER. “Add about 3 zeroes to each of those steps,” remarked Tom Ebbott, Endurica’s VP and newest team member. “It’s the same concept in tire development but the impact is just so much bigger.”

From a technical side, one of our client’s says it best: “In optimizing a geometry to extend the fatigue life of a product I ran a few iterations of inner-cavity geometries, and found one specific geometry with Endurica that achieved 500,000 cycles to failure in contrast to the 30,000 I had before. It’s more than a 10-time improvement and that’s really significant. These concrete numbers are really powerful in helping us and our customers to make good decisions.” Francois Rouillard, R&D Mechanical Engineer, Maestral Sealing Laboratory, Technetics, Pierrelatte, France.

WHY IT MATTERS: Endurica’s users find THE BEST solution to their client’s problem early — at the $5,000 stage of design. They can skip the multiple iterations that easily run $50,000 each and go right into the $500,000 production testing cycle with complete trust in the product’s success.

Durability by Design on Any Budget

June 9, 2022June 7, 2021 by William V. Mars, Ph.D., P.E.

So, you’ve got a tricky durability problem to solve, a budget, and a deadline. Let’s look at a helpful framework for sorting which Endurica workflows you need. In the grid below, each row represents a potential approach you can take. The approaches are, in order of increasing complexity and cost, the Infinite Life approach, the Safe Life approach, the Damage Tolerant approach, and the Fail Safe approach.

The Infinite Life approach is by far the simplest approach. Here, we say that damage will not be allowed at all. All locations in the part must operate, at all times, below the fatigue limit (ie intrinsic strength) of the rubber. The required material testing is minimal: we need only know the fatigue limit T₀ and the crack precursor size c₀. We avoid the question of how long the part may last, and we focus on whether or not we can expect indefinite life. We report a safety factor S indicating the relative margin (ie S = T₀ / T) by which each potential failure location avoids crack development. When S>1, we predict infinite life. For S<=1, failure occurs in finite time and we must then go on to the next approach…

In the Safe Life approach, the chief concern is whether or not the part’s estimated finite life is adequate relative to the target life. The material characterization now becomes more sophisticated. We must quantify the various “special effects” that govern the crack growth rate law (strain crystallization, temperature, frequency, etc.). We consider the specific load case(s), then compute and report the number of repeats that the part can endure. If the estimated worst-case life is greater than the target life then we may say that the design is safe under the assumptions considered. If not, then we may need to increase the part’s load capacity, or alternatively to decrease the applied loading to a safe level. In critical situations, we may also consider implementing the next level…

The Damage Tolerant approach acknowledges that, whatever the reasons for damage, the risk of failure always exists and therefore should be actively monitored. This approach monitors damage development via inspection and via tracking of accrued damage under actual loading history. A standard nominal load case may be assumed for the purpose of computing a remaining residual life, given the actual loading history to date. Changes in material properties due to cyclic softening or ageing may also be tracked and considered in computing forecasts of remaining life.

The Fail Safe approach takes for granted that failure is going to occur, and obliges the designer to implement measures that allow for this to happen safely. This can take the form of a secondary / redundant load path that carries the load once the primary load path has failed. It can take the form of a sacrificial weak link / “mechanical fuse” that prevents operation beyond safe limits. It can take the form of a Digital Twin that monitors structural health, senses damage, and requests maintenance when critical damage occurs.

The last three columns of the grid show which Endurica fatigue solver workflows align with each design approach. The Endurica solvers give you complete coverage of all approaches. Whether you need a quick Infinite Life analysis of safety factors for a simple part, or deep analysis of Damage Tolerance or Fail Safety, or anything in-between, our solvers have just what you need to get durability right.

Solving the Durability Puzzle

June 3, 2022August 8, 2019 by William V. Mars, Ph.D., P.E.

Solve the Durability puzzle with Endurica Ever thought about what it takes to deliver the durability you expect from products you use? Durability reflects the combined sum of many decisions made all along the supply chain. What sources to use for raw materials? What dimensions and shape for product features? Are there OEM- or customer-imposed design constraints? What load cases occur in manufacturing, shipping, installation, and operation? Manufacturing processes? OEM-specified qualification and / or regulatory testing requirements? What is the warranty or brand promise? If these decisions are not made well, then durability (as well as cost and weight) will suffer.

The people making these decisions come from many backgrounds. They are chemists, product engineers, testing engineers, structural analysts. The big challenge is to organize things so that their contributions all add up to the desired end result: getting durability right, preferably on the first try. It’s a big challenge because the domain expertise and tools in place today in many organizations were largely built before the science was ready and before the workflows were understood well enough to integrate across disciplines. This situation can make it quite difficult to solve the durability puzzle. The pieces don’t all fit together!

Oversimplified lab tests whose relationship to actual product use is doubtful
Fatigue testing instruments that produce noisy data, or execute with uncontrolled test duration
Raw materials suppliers struggling to relate chemistry and process improvements to actual impact on end products
Compounders making materials selection decisions based on insufficient / poor information
Product engineers missing opportunities to fully leverage material capacity
Outdated and inaccurate ‘rule of thumb’ engineering that doesn’t work on new cases
Incomplete simulation efforts that fail to forecast or diagnose key durability issues
Product qualification tests that under- or over-solicit damage or change failure modes
Part suppliers leaving OEMs with too little confidence that durability issues have been handled
OEMs and part suppliers struggling to account for actual end-use load cases

Endurica-powered workflows overcome these barriers. Our training, testing services, testing instruments, and CAE software solutions integrate across disciplines. Our motto is “Get Durability Right”.

Our classes are geared specifically for your compounders, test engineers, product engineers and analysts. Your compounder doesn’t need to be a mechanical engineer, but she does need to negotiate the demands on the material. Your product engineer and your analyst don’t need a PhD in chemistry, but they do need to push for performance that will win for the customer. Your test engineer needs reliable, productive measurement strategies that get the key information that will power up your materials and product development efforts. Our classes will pay for themselves many times over when your team confronts the next durability pitfall.

Our testing services and testing instruments produce a complete picture of what limits durability in your application. Rubber exhibits many ‘special effects’, and our tests are very useful for quantifying each effect, for building material models, and for solving and diagnosing durability issues. We partner with leading labs around the world to bring you fast and reliable testing for durability simulation. We partner with testing instrument maker Coesfeld to bring our protocols directly to your own lab with automated, user-friendly control, measurement and data reduction. Analysts, designers and materials engineers all need clean, abundant, high-relevance measurements.

Our software (Endurica CL, Endurica DT, Endurica EIE and fe-safe/Rubber) provides the most complete set of durability analysis capabilities in the world. Total life, incremental damage, residual life, critical plane analysis, rainflow counting, nonlinear loads mapping, road load signal analysis, stiffness loss co-simulation, self-heating – its all here: documented, supported, validated, with examples and a large user-base. We support the Abaqus, Ansys and MSC/Marc Finite Element solvers. Use our software to see how different materials, different geometry, different load / use cases impact durability. If your materials, product, analysis or testing people can ask the question, chances are that our tools will simulate it and give you new insights.

Durability doesn’t have to be a difficult puzzle. It costs way too much when people from different disciplines don’t “speak the same language” and try to go forward with conflicting ideas and tools. Solve the puzzle by using pieces that fit together. Get your team speaking Endurican!

Keywords: Compounding, Design, Testing, Analysis, Training