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”
44th 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 10th 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 13th 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!
Road load signals are notoriously difficult to work with. The signals feature so many different time increments that it becomes too much to directly model efficiently in FEA. It is difficult to tell which portions of the loading do the most damage. Experimental fatigue testing would be too time-consuming and costly to run on the full complex road load signal. For these reasons simplifying road loads into block cycle schedules has become the gold standard for working with road load signals. Experimental testing and FEA modeling are more manageable when using a block cycle schedule instead of the full road load signal. Traditional methods of converting a road load signal to block cycle schedule can often fall short. Endurica recently added a built-in method in the Endurica CL software that uses the power of critical plane analysis and rain-flow counting to automate block cycle creation.
