*** Please note, each row and course# listed below is a separate, complete course. ***
Tire Safety and Durability
| Course# | Date | Time | Location | |
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Coming Soon |
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Online Registration
CEU's: 0.8
Instructor: Dr. Gary R. Hamed
Course Overview
The National Highway Traffic Safety Administration (NHTSA) is the government “watchdog” that oversees tire safety. It can mandate recalls when tires are found to be defective. According to NHTSA, recent crashes of passenger vehicles per year in the U.S. have resulted in more than 42,000 fatalities, 5.5 million non-fatal injuries and an economic cost exceeding $250 billion. This does not include litigation costs, which have added costs of billions of dollars per year. NHTSA estimates that about 1% of vehicle crashes are due to catastrophic tire failure. Thus, tire failures have been quite costly.
NHTSA states that more than 95% of recalled tires have tread/belt edge separation. Thus, this portion of tires must have the greatest resistance to catastrophic tearing. Tires experience high tearing stresses when they are underinflated, overloaded, subject to excessive speed, and/or are severely stressed, for example, by hitting a large chuckhole. Belts of all tires made by all manufactures are always black-filled natural rubber (NR); such compounds have the highest resistance to catastrophic tearing of all rubbers. (It is noteworthy that the resistance of such rubbers to slow crack growth is not particularly high.) Tires must be able to tolerate rather large belt edge cracks without failing catastrophically. This will enable the driver to hear tire thumping and/or pulling (before tire failure) and know that it is time to get a replacement tire. I have examined many tires that are performing satisfactorily that, nonetheless, contain sizeable belt edge cracks.
Online Course Requirements
We want you to have a great experience participating in our remote (online) courses, and for that, you’ll need the right equipment and internet connection.
Minimum needs are:
- A broadband internet connection that has at least a 2 Mbps upload and download speed.
- A computer (PC or Mac) that can support the latest web browser versions.
- At least 4 GB of RAM and adequate hard drive space.
- A microphone and a speaker.
- International Students: For virtual (online) courses, an additional fee will be assessed to cover the cost of shipping the professional binder (presentation slides), to your address. The cost of international shipping can be significant.
For more information, visit our Online Course Requirements webpage.
Instructor Biography:
Dr. Gary R. Hamed has been a professor at the University of Akron for more than 40 years and has carried out extensive studies of tire science and technology for 50 years. He is a leading expert is this field and has consulted for many companies including Firestone, Bridgestone, Michelin, Goodyear, Continental, Cooper, Yokohama, Pirelli, Sumitomo, Hankook, Kumho, Cabot, Columbian Chemical, et al. He graduated from Cornell University with a 4.1 (A+ was 4.3) GPA in Chemical Engineering and studied under Alan Gent for his doctorate, maintaining a 4.0 (no A+ available) GPA. He then went to Firestone where he worked 4 years and obtained 14 patents. Next, he joined The University of Akron, where he received the Outstanding Researcher Award. He has also received Best Paper Awards, the first Sparks-Thomas Award and the George Stafford Whitby Award from the ACS Rubber Division. He is a fellow of the Adhesion Society and has presented or published nearly 500 short courses and papers.
He has been quite involved in research on tire safety and durability and has prepared an important short course on the subject. Dr. Hamed has also worked with NHTSA concerning tire safety, especially about truck tire treads that are widely strewn over our highways.
This short course will address the catastrophic tearing of elastomers used in tires, with emphasis on black-filled NR. The following will be shown and explained.
- The importance of tear strength on tire durability. Two compounds that have the same tensile strength can have tear strengths that differ by more than ten times!
- Outstanding catastrophic tearing resistance of black-filled NR. Certain NR compounds have tear strengths that are insensitive to defects!
- Circumstances where carbon black lowers the tear strength of NR.
- Methodology to maximize NR tear strength, especially at elevated running temperature.
- Influence of crosslink type and density on tear strength.
- Combining black types to maximize tear strength.
- Influence of black type and level on tear strength.
- NR compounds have higher tear resistance than SBR and BR compounds, especially at regions of high stress concentration.
- Basis of rubber reinforcement.
- Energy dissipation, positive and negative effects.
- Mechanism of carbon black reinforcement. It is impossible to have high reinforcement with micron-sized filler, even if rubber to filler bonding is very high.
- Non-relaxing strains affect fatigue life—sometimes increasing it substantially. Fatigue life can also be increased by employing double networks.
- Effect of stress concentration on tear resistance.
- Why do all tires contain carbon black.
- What is the role of bound rubber in reinforcement.
- Tear strength instability in NR compounds. Some NR compounds have tear strengths that are drastically reduced as flaw size increases.
- Tear strength is a good measure of durability, but tensile strength is not.
- Role of high strain rate on tearing. Rapid strain-crystallization is necessary for high resistance to catastrophic tearing.
- Double networks can improve tear resistance.
- Peroxide cured NR vulcanizates have lower tear strength than sulfur-vulcanized ones.
- Role of anisotropy on tear resistance.
- Rubber fracture is a mechano-chemical process.
- Natural rubber and synthetic isoprene rubber compounds can have similar or quite different tear strengths.