Quote:
Originally Posted by Tireman9
Danny, CWthe Man was nice enough to post the info from NHTSA and RVSEF about 50% of RVs having one or more tire in overload.
I trust you have read THIS post. Re your engineering analysis that indicates "china bomb" is a reason for failure I am wondering why that cause is not included in the Tire Industry Association condition manual approved and supported by Goodyear, Bridgestone, Michelin, Yokohama and a few other tire companies? Why isn't you analysis supported in the book on "Tire Forensic Investigation" by Giapponi?
RE the science behind Interply Shear. I have a number of posts on my blog on that topic but for those not interested in reading that info I provide the following from tire industry research.
Dr. Song's paper on"FATIGUE OF CORD-RUBBER COMPOSITES FOR TIRES."
Here is the abstract.
Fatigue behaviors of cord-rubber composite materials forming the belt region of radial pneumatic tires have been characterized to assess their dependence on stress, strain and temperature history as well as materials composition and construction. Using actual tires, it was found that interply shear strain is one of the crucial parameters for damage assessment from the result that higher levels of interply shear strain of actual tires reduce the fatigue lifetime. Estimated at various levels of load amplitude were the fatigue life, the extent and rate of resultant strain increase (“dynamic creep”), cyclic strains at failure, and specimen temperature. The interply shear strain of 2-ply ‘tire belt’ composite laminate under circumferential tension was affected by twisting of specimen due to tension-bending coupling. However, a critical level of interply shear strain, which governs the gross failure of composite laminate due to the delamination, appeared to be independent of different lay-up of 2-ply vs. symmetric 4-ply configuration. Reflecting their matrix-dominated failure modes such as cord-matrix debonding and delamination, composite laminates with different cord reinforcements showed the same S-N relationship as long as they were constructed with the same rubber matrix, the same cord angle, similar cord volume, and the same ply lay-up. Because of much lower values of single cycle strength (in terms of gross fracture load per unit width), the composite laminates with larger cord angle and the 2-ply laminates exhibited exponentially shorter fatigue lifetime, at a given stress amplitude, than the composite laminates with smaller cord angle and 4-ply symmetric laminates, respectively. The increase of interply rubber thickness lengthens their fatigue lifetime at an intermediate level of stress amplitude. However, the increase in the fatigue lifetime of the composite laminate becomes less noticeable at very low stress amplitude. Even with small compressive cyclic stresses, the fatigue life of belt composites is predominantly influenced by the magnitude of maximum stress. Maximum cyclic strain of composite laminates at failure, which measures the total strain accumulation for gross failure, was independent of stress amplitude and close to the level of static failure strain. For all composite laminates under study, a linear correlation could be established between the temperature rise rate and dynamic creep rate which was, in turn, inversely proportional to the fatigue lifetime. Using the acoustic emission (AE) initiation stress value, better prediction of fatigue life was available for the fiber-reinforced composites having fatigue limit. The accumulation rate of AE activities during cyclic loading was linearly proportional to the maximum applied load and to the inverse of the fatigue life of cord-rubber composite laminates. Finally, a modified fatigue modulus model based on combination of power-law and logarithmic relation was proposed to predict the fatigue lifetime profile of cord-rubber composite laminates."
As you understand Finite Eliment analysis but may not have run the analysis I will offer that the results show that tires on multi-axle trailers are subject to IPS that is 24% higher than an identical tire in motor vehicle service.
Looking forward to learning where I can read your peer reviewed scientific papers so I can correct my obviously flawed understanding of why tires fail.
Have a nice day and happy Camping. |
I am not questioning your "engineering" expertise, I question the definitive data that excludes the possibility of a "China bomb" - none has been presented. "Studies", unless performed on the actual failures are then just a basis for conjecture, assumptions and possibilities - nothing is proven by them other than what the data actually shows. To say that more than 1/2 of the RVs at a show had a tire in an overload condition, then jump that actual data, to state the fact that all tire failures are due to overload, underinflation or interply shear, and there are no defective tires from the factory is.....well, a 'fer stretch. IMO the data collected by those that have the failures and then share is far more definitive than studies on good tires. But that's just me.
For me, there is no "hornet's nest" surrounding the "China bomb" nomenclature. It's simply a fact that hasn't been refuted by any statement made in this thread thus far. Whether one chooses to call them a "China Bomb", "Shandong crap" or whatever to simplify addressing them seems OK to me. A "study" on "normal tires" does not disprove their existence IMO.
I know you have your thoughts on the subject and that's fine. We can agree to disagree.
